Polarization Mode Dispersion Measurement System PMD5000 ... · 2006 Operation Manual Thorlabs...

2006

Operation Manual

Thorlabs Instrumentation

Polarization Mode DispersionMeasurement System

PMD5000FIN / HDR

Version:Date:

2.004.10.2006

© <2006> Thorlabs

© <2006> Thorlabs

Table of Contents

Foreword 3

Part I General Information 5

................................................................................................................................... 51 Safety

................................................................................................................................... 62 Parts List - Accessories

................................................................................................................................... 73 License Key

Part II Getting Started 10

................................................................................................................................... 101 Quick Start-up

................................................................................................................................... 122 Export and Save Data

................................................................................................................................... 133 Setup

................................................................................................................................... 144 Theory of Operation

Part III Hardware Description 17

................................................................................................................................... 171 Operating Elements

......................................................................................................................................................... 17PMD5000FIN

......................................................................................................................................................... 17PMD5000HDR

................................................................................................................................... 182 Installing and Removing Cards

Part IV Operating Instruction 20

................................................................................................................................... 201 Preconditions

................................................................................................................................... 212 The Graphical User Interface (GUI)

......................................................................................................................................................... 21Start the GUI

......................................................................................................................................................... 21Configuration

.................................................................................................................................................. 22Laser Configuration

.................................................................................................................................................. 25VISA Remote Server

.................................................................................................................................................. 27SOP Controller Configuration

.................................................................................................................................................. 29Polarimeter Configuration

......................................................................................................................................................... 32Connection

......................................................................................................................................................... 33Measurement

.................................................................................................................................................. 34Measurement Configuration

.................................................................................................................................................. 37Start a Single Measurement Scan

.................................................................................................................................................. 37Repeated Measurement Scans

......................................................................................................................................................... 41Measurement Results

.................................................................................................................................................. 43Diagrams

........................................................................................................................................... 43PDL Diagram

........................................................................................................................................... 44IL Diagram

........................................................................................................................................... 45Power Diagram

........................................................................................................................................... 46DGD Diagram

........................................................................................................................................... 47DGD Histogram

........................................................................................................................................... 48Phase Diagram

........................................................................................................................................... 492nd Order DGD Diagram

........................................................................................................................................... 502nd Order DGD Histogram

........................................................................................................................................... 51PSP Diagram

........................................................................................................................................... 52PCD Diagram

........................................................................................................................................... 53PSP Rotation Rate Diagram

.................................................................................................................................................. 53Data Analysis / Calculations Window

.................................................................................................................................................. 55Cursor Control

.................................................................................................................................................. 58Saving Data

© <2006> Thorlabs

......................................................................................................................................................... 62Program Navigation

.................................................................................................................................................. 63Menu Bar

.................................................................................................................................................. 65Tool-Bar

.................................................................................................................................................. 66Display Functions

......................................................................................................................................................... 67Display Configuration

.................................................................................................................................................. 68Color Setup

.................................................................................................................................................. 68Display Options

Part V Service and Maintenance 71

................................................................................................................................... 711 Troubleshooting

................................................................................................................................... 722 Service

Part VI Appendix 74

................................................................................................................................... 741 Warranty

................................................................................................................................... 752 Technical Data

................................................................................................................................... 753 WEEE

......................................................................................................................................................... 76Waste Treatment on your own Responsibility

......................................................................................................................................................... 76Ecological Background

................................................................................................................................... 774 Listings

......................................................................................................................................................... 77List of Acronyms

......................................................................................................................................................... 77List of Figures

......................................................................................................................................................... 79Addresses

Part VII Application Notes 81

................................................................................................................................... 811 Definitions and Terms

................................................................................................................................... 832 Accuracy

................................................................................................................................... 903 Measurement of Fibers

................................................................................................................................... 964 Measurement of Narrow Bandwidth Components

Index 101

© <2006> Thorlabs

We aim to develop and produce the best solution for your applicationin the field of optical measurement technique. To help us to come upto your expectations and develop our products permanently we needyour ideas and suggestions. Therefore, please let us know aboutpossible criticism or ideas. We and our international partners arelooking forward to hearing from you.

Thorlabs

This part of the instruction manual contains every specific information onhow to handle and use the PMD5000FIN / HDR.

Attention

This manual contains "WARNINGS" and "ATTENTION" label inthis form, to indicate danger for persons or possible damage of

equipment.

Please read these advises carefully!

NOTE

This manual also contains "NOTES" and "HINTS" written in this form.

G G

© <2006> Thorlabs

General Information

PMD5000

Part

I

5General Information

© <2006> Thorlabs

1 General Information

1.1 Safety

GAttentionG

All statements regarding safety of operation and technical data in thisinstruction manual will only apply when the unit is operated correctly as it

was designed for.

Before applying power to your TXP system, make sure that the protectiveconductor of the 3 conductor mains power cord is correctly connected to

the protective earth (GROUND) contact of the socket outlet!Improper grounding can cause electric shock which may result in severe

injury or even death!

All modules must be fastened with all provided screws for this purpose.Modules of the TXP5000 Series must only be operated in mainframes of the

TXP5000 Series.

All modules must only be operated with proper shielded connection cables.Only with written consent from Thorlabs may changes to single

components be carried out or components not supplied by Thorlabs beused.

This precision device is only serviceable if properly packed into thecomplete original packaging including the plastic foam sleeves. If

necessary, ask for a replacement package.

GAttentionG

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© <2006> Thorlabs

The modules 'ECL5000' and 'LS5000' are Class 1M Laser Sources.Emitted wavelengths and optical power: See label on the ECL5000 or

LS5000, respectively.

CAUTION – When using these products together with other opticalinstruments or setups, sufficient measures to provide eye safety must be

undertaken!!

G Attention G

The laser modules supplied by Thorlabs are Class 1M Laser Systems.However, if you collimate or focus the laser beam you will create a Class 3R

or Class 3B Laser System!In this case, additional safety precautions should be observed!

For the individual wavelength and output power see the certificate ofcalibration supplied with the module!

Never switch on the output without a fiber connected and switch off theoutput before disconnecting the fiber!

Tunable laser sources from a third party can have different laser classes.Refer to the specific manual for these laser systems.

1.2 Parts List - AccessoriesA complete PMD measurement system based on the JME consists of a tunablelaser source, a SOP controller and a polarimeter. Thorlabs offers 4 differentmodels of the PMD5000 system.

Thorlabs offers an integrated tunable laser source, the ECL5000D, and drivers forexternal laser sources. The DPC5500 is used to control the SOP. There are twodifferent kinds of polarimeters. The IPM5300 is a fast in-line polarimeter and isespecially suited to measure PMD on fibers where environmental conditionsinfluence the PMD and therefore measurement speed is required. ThePAX5720IR3 in contrast has a high dynamic power range. The main field ofapplication is the DGD measurement of components with band passcharacteristics. A preconfigured notebook is also included in the delivery.

7General Information

© <2006> Thorlabs

1. PMD5000FIN-1 :· TXP5016 Mainframe· ECL5000D Tunable Laser Source· DPC5500 Deterministic Polarization Controller· IPM5300 Fast In-line Polarimeter· Preconfigured Laptop· CD-ROM with all Software included· Operating Manual for the PMD5000 System and all Modules· Patchcord FC/APC - FC/APC· Cross Link Cable (CABCRO)

2. PMD5000FIN-2:· TXP5016 Mainframe· DPC5500 Deterministic Polarization Controller· IPM5300 Fast In-line Polarimeter· Preconfigured Laptop· CD-ROM with all Software included· Operating Manual for the PMD5000 System and all Modules· Cross Link Cable (CABCRO)

3. PMD5000HDR-1:· TXP5016 Mainframe· ECL5000D Tunable Laser Source· DPC5500 Deterministic Polarization Controller· PAX5720IR3 Polarimeter· Preconfigured Laptop· CD-ROM with all Software included· Operating Manual for the PMD5000 System and all Modules· Patchcord FC/APC - FC/APC· Cross Link Cable (CABCRO)

4. PMD5000HDR-2:· TXP5016 Mainframe· DPC5500 Deterministic Polarization Controller· PAX5720IR3 Polarimeter· Preconfigured Laptop· CD-ROM with all Software included· Operating Manual for the PMD5000 System and all Modules· Cross Link Cable (CABCRO)

1.3 License KeyTo use all features of the PMD5000 software the license key has to be installed.Without the license key you can run the PMD5000 software as evaluationsoftware. That means you can load measurement files (*.pmd) and analyze thedata. However, you cannot connect to a PMD5000 measurement system andperform PMD measurement scans.To install the license key insert the provided Thorlabs TXP PMD5000 License

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© <2006> Thorlabs

Key CD-ROM into your CD-ROM drive. Follow the instructions of the installationwizard. The license key is already installed on your preconfigured Laptop for thePMD5000 system.

Getting Started

PMD5000

Part

II

10 PMD5000

© <2006> Thorlabs

2 Getting StartedThis section is provided for those interested in getting the PMD5000 up andrunning quickly. The more detailed description and advanced features aredescribed in the following sections.

2.1 Quick Start-upThe system comes with an already preconfigured computer. You can also installthe TXP5000 software and the PMD5000 software on your own computer usingthe supplied installation CDs.

The following description shows the start-up with the supplied computer:

1. Connect the computer with the cross-link cable (CABCRO) with the TXP5016chassis.

2. Use optical patchcords to connect the TLS output with the input of the SOPController (DPC5500), the output of the SOP Controller with the input of theDUT and the output of the DUT with the polarimeter (IPM5300 orPAX5720IR3).

3. Connect the TXP5016 to the mains supply and switch it on. Wait until theREADY LED lights up.

4. Power up the computer.5. To start the PMD5000 measurement system, click on the desktop icon or

select the 'START' button in the Windows task bar and choose 'All Programs /TXP Series /TXP PMD5000'.

6. The following screen will appear.

Figure 1 PMD5000 Graphical User Interface

11Getting Started

© <2006> Thorlabs

7. The PMD5000xxx-1 system is already preconfigured. The IP addresses andslot numbers are valid for the delivered system. The PMD5000xxx-2 systemworks with an external tunable laser source which has to be configured. SeeLaser Configuration section for more details. To connect to the system, clickthe button with the green arrow or select from the menu 'System / Connect'.

Figure 2 Connect to the System

8. The connection to the single modules will last several seconds. After asuccessful connection the green 'Go' button will be enabled and ameasurement can be started.

9. Enable the 'Measurement Panel' by clicking on the button 'View MeasurementConfiguration Panel' from the tool bar.

10.Enter start and stop wavelength, the step width and the Laser power for yourmeasurement in the 'Standard JME Measurement' window.

Figure 3 Standard JME Measurement Window

11.Click the button 'Optimize Step Width' from the 'Standard JME Measurement'window to find the optimized step-size for the device under test.

12.Press the 'Start' button from the 'Standard JME Measurement' window toperform the measurement. You can also select 'Measurement / Start Scan' bysimply pressing the 'F5' key on your keyboard or click on the 'Run New

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© <2006> Thorlabs

Measurement' button from the tool bar to run the measurement.13.During the measurement the result is continuously updated in the diagram. If

nothing is shown in the diagram during the scan the view area does not coverthe measurement data. Simply click on the button 'Zoom Out to Full View' or press the 'Home' key on your keyboard.

14.The progress of the measurement is shown in the lower part of the 'StandardJME Measurement' panel.

Figure 4 Measurement Scan finished

To disconnect from the instruments, click the 'Disconnect Measurement System'button in the tool bar or choose 'System / Disconnect' from the menu. Allsettings will be stored and present after a new connection. Now you can continueto work with the captured measurement data and you can save or loadmeasurement data. You do not have to connect to the system to analyze thedata.You can close the application with the 'File \ Exit' from the menu or with the crossin the right upper corner of the screen.

2.2 Export and Save DataThe measurement data should be saved as a *.pmd file. Once saved in this typeof file format (*.pmd) it can be reloaded into the application again.

It is possible to export all relevant measured and calculated data that can bedisplayed with this software including DGD or PSP in a comma separated valuesfile (*.csv). This file format can be handled with third party software (Text editors,Microsoft Excel™) but it cannot be reloaded into the application again.

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Select 'File / Save Measurement Data ...' to save a *.pmd file. To export a *.csvfile choose 'File / Export Measurement Data ...' from the menu.

Figure 5 Saving / Export Data

2.3 SetupThe following schematic shows the principal measurement setup split in itscomponents.

Figure 6 Setup Schematic Diagram

Setup Description:

- Tunable Laser SourceThe Thorlabs ECL5000D tunable laser source is used to generate laserlight from 1520nm to 1630nm. The laser output power can be set from0.5 to 10mW. The tuning step width is variable, which is important for

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accurate DGD measurements.An alternative is to use a third party tunable laser source. Ask our TechSupport Team for available lasers.

- SOP GeneratorThe DPC5500 generates the SOPs necessary to perform Jones Matrixanalysis.

- Device Under Test (DUT)The DUT can be a long fiber of an optical network or a narrowbandwidth device.

- Polarization AnalyzerThe setup uses the IPM5300 inline polarimeter to analyze the incomingbeam. The polarimeter is based upon patented FBG technology thatfeatures fully fiber based polarization measurements. The IPM5300 isappropriate for measurements of long fiber systems.Another alternative is the PAX5720IR3. It is based on the rotatingwaveplate technique. This polarimeter offers a wide dynamic powerrange and should be used for PMD measurements of narrow bandwidthdevices.

2.4 Theory of OperationAll measurements are based on the Jones Matrix method. The SOP generatorapplies 3 linear polarizations with 45° difference to the device under test. Thepolarimeter measures the related azimuth and ellipticity values.From these the PDL can be calculated for every wavelength step.To calculate the DGD a further wavelength step is necessary. The differentazimuth and ellipticity angles and the optical angular frequency are set into theequations for the Jones Matrix Eigenanalyzis (JME) – the result is a DGD value.The mean of all DGD values for each wavelength step is the PMD of the deviceunder test.To calculate the second order DGD two DGD values at different wavelengths andthe corresponding principal states of polarization PSP are necessary.

Figure 7 Jones Matrix Eigenanalyzis

Procedure:· Set first wavelength @ l1 with TLS· Set 3 different input polarization states @ A· Measure the 3 corresponding output polarization states @ B· Calculate Jones Matrix JC(l1)· Determine PDL1 from [JC(l1)]*T JC(l1)

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· Repeat for next wavelength l2· Determine DGD1 from JC(l1) and JC(l2)· Average DGDs over l for PMD

Definition:PDL: Maximal difference in attenuation among all input polarization statesPDL axis: Input polarization state with minimum attenuationDGD: Delay between the fastest and the slowest polarization state at a

certain wavelength and a certain time; it is an instantaneous valuewhich can be random or deterministic variable.

PMD: Mean delay (= DGD mean value) averaged over a certainwavelength range at a certain time or equivalently certain timewindow at a specific wavelength; or averaged over both it is almost /truly independent of time (result of measurement / in a mathematicalsense).

SOPMD: The second order PMD is the meanvalue of the second order DGDdistribution averaged over the wavelength range. For a moredetailed description see Definitions and Terms section.

Hardware Description

PMD5000

Part

III

17Hardware Description

© <2006> Thorlabs

3 Hardware DescriptionThe Thorlabs PMD5000FIN and PMD5000HDR Polarization Mode DispersionMeasurement System is a flexible and powerful analyzing tool for fiber links aswell as narrow bandwidth devices. It is based on the Jones Matrix Eigenanalyzis.This method features not only the PMD value with one wavelength scan but alsothe DGD versus wavelength and the PDL, the PSPs, the second order DGD andthe insertion loss (IL). Passive components like couplers and isolators can bemeasured as well as active components (EDFAs and PDFAs).

The PMD5000 system is modular. Each module can be used by its own. Themeasurement system can also be upgraded to measure already installed fibers orto monitor the DGD of one channel of an in-use DWDM system.

3.1 Operating Elements3.1.1 PMD5000FIN

The PMD5000FIN is available in two versions. The PMD5000FIN-1 consists ofthe tunable laser source (ECL5000D), the deterministic polarization controller(DPC5500) and the in-line polarimeter (IPM5300).The PMD5000FIN-2 features the deterministic polarization controller (DPC5500)and the in-line polarimeter (IPM5300). As tunable laser source an external laserhas to be used.The mainframe is a TXP5016 which is controlled via Ethernet.

Figure 8 PMD5000FIN

3.1.2 PMD5000HDR

The PMD5000HDR is available in two versions. The PMD5000HDR-1 consists ofthe tunable laser source (ECL5000D), the deterministic polarization controller(DPC5500) and the polarimeter (PAX5720IR3).The PMD5000HDR-2 features the deterministic polarization controller (DPC5500)and the polarimeter (PAX5720IR3). As tunable laser source an external laser has

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© <2006> Thorlabs

to be used.The mainframe is a TXP5016 which is controlled via Ethernet.

Figure 9 PMD5000HDR

3.2 Installing and Removing CardsThe Thorlabs TXP series mainframe and cards are 'Hot-Swappable', whichmeans you do not have to switch off the mainframe while exchanging cards:

· Loosen the two to four mounting screws on top and below the ejector handle· Push the red button of the ejector handle and flip down the black ejector

handle. This pulls out the card from its internal plug.

You can now remove the card. If you do not insert another card, please close theempty slot with a blind module to maintain a proper cooling air flow inside the unit.Tighten the two to four screws.

NOTEAll Slots of the TXP must be occupied, either by a card or by a blind module tomaintain proper air flow for internal cooling!

NOTEThe PMD5000 application has to be stopped before you remove a card. After acard is exchanged the application has to be restarted.

For more information refer to the TXP5016 manual.

Operating Instruction

PMD5000

Part

IV

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© <2006> Thorlabs

4 Operating InstructionThis section gives an introduction to operating the PMD5000 measurementsystem.

4.1 PreconditionsThe system includes a preconfigured Laptop; you have only to set up the cableconnections and then you can use the system.

For PMD5000xxx-1 systems:1. Connect the Laptop with the TXP5016 using the cross-link cable (CABCRO).2. Use the delivered patchcords to connect the optical output of the tunable laser

with the optical input of the DPC5500. Both connectors are FC/APC.3. The input of DUT has to be connected with the output of the DPC5500 and

the output of the DUT with the input of the polarimeter (IPM5300 orPAX5720IR3). Note that the IPM5300 has FC/APC connectors and thePAX5720IR3 has a FC/PC input by default.

4. Switch on the Laptop and the TXP5016.

For PMD5000xxx-2 systems:1. Connect the Laptop with the TXP5016 using the cross-link cable (CABCRO).2. Connect your external TLS appropriate with the laptop (e.g. GPIB cable). No

special hardware interfaces are supplied with this system.3. Connect the optical output of the tunable laser with the optical input of the

DPC5500. Note that the DPC5500 has FC/APC connectors.4. The input of DUT has to be connected with the output of the DPC5500 and

the output of the DUT with the input of the polarimeter (IPM5300 orPAX5720IR3). Note that the IPM5300 has FC/APC connectors and thePAX5720IR3 has a FC/PC input by default.

5. Switch on the Laptop and the TXP5016.

If you prefer to use your own PC follow the steps below:

1. Ensure that National Instruments VISA 3.0 or higher is already installed onyour computer. This software can be found on the installation CD.

2. Install the TXP Series Instrumentation software:a) Insert the CD-ROM into the CD-ROM driveb) If the 'autorun' function is active on your PC, the installation program

should start automatically. If not start the program 'Autorun.exe' on theCD.

c) A panel appears. Select 'Install Software'.d) An installation panel appears. Following the instructions of the

installation wizard.3. Proceed as described above depending on your PMD5000 system.

The TXP system is now ready for operation and you can start the PMD5000graphical user interface (GUI).

21Operating Instruction

© <2006> Thorlabs

4.2 The Graphical User Interface (GUI)4.2.1 Start the GUI

The PMD5000 software can be started by clicking on the desktop icon. You canalso select 'Programs' via the START button in the Windows task bar and thenchoose 'All Programs / TXP Series / TXP PMD5000'. The graphical user interface(GUI) appears.

Figure 10 PMD5000 Graphical User Interface

You can use this tool to analyze previously captured measurement scans withoutconnecting to the PMD5000 system. This can be done by selecting 'File / OpenMeasurement Data ...' from the menu or clicking on the button 'LoadMeasurement Data from File' from the tool bar. Furthermore, you can also loada reference scan by choosing 'File / Open Reference Data ...' from the menu.For a detailed description about the evaluation of the measured data refer tosection Data Analysis.

4.2.2 Configuration

The PMD5000 system consists of the transmitter section and the receiver section.The tunable laser source (e.g. ECL5000D) and the polarization controller(DPC5500) represent the transmitter unit. The receiver is a polarimeter module.

To configure the system select 'System / Configuration ...' from the menu.

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Figure 11 System Configuration

The following window appears and displays the current configuration informationof the modules. If the system is not connected you can select the module you liketo configure.

Figure 12 Main Configuration Window

4.2.2.1 Laser Configuration

The laser configuration tab depends on the laser model. The PMD5000FIN-1 andPMD5000HDR-1 are equipped with the ECL5000. The systems PMD5000FIN-2and PMD5000HDR-2 work with external tunable laser sources. Currently theAgilent 8164A system and the Ando AQ4320D are available. Contact Thorlabs forthe latest information about the supported laser sources.

Select Laser Type Select the laser you want to use in your PMD system.

Thorlabs ECL5000DThis laser is integrated in the TXP5016 mainframe. If you are using thepreconfigured laptop the correct IP address and slot number is already loaded.You only have to change it if you alter the setup configuration.


© <2006> Thorlabs

Figure 13 ECL5000D Configuration Window

IP / Hostname Contains the IP address of the TXP mainframe. ThePMD5000 system consists of a TXP5016. This mainframehas a fixed IP address by default for example192.xxx.xxx.xxx. Please refer to the operating manual of theTXP5016 for more information about the IP address.The expression 'localhost' is only valid if the ECL5000D isoperated in a TXP5004 or TXP5001 mainframe.

Port Specifies the port number of the TCP/IP- Connection to theTXP5016 mainframe. The default port value is 2402.

Slot Defines the slot of the TXP5016 mainframe where theECL5000D is installed.

Timeout Describes the timeout for the laser remote connection.

If you want to use an external tunable laser select the corresponding laser typefrom the 'Select Laser Type' selection. According to the laser type the connectionparameter will change.

Agilent 8164AThis laser is an external laser source which has to be connected via a GPIB cableto the computer or to a different PC which works as a VISA Remote Server. Referto the VISA Remote Server section for more details.

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Figure 14 Agilent 8164A Configuration Window

Check Box If the external tunable laser source is used with a differentcomputer which acts as a VISA Remote Server set the checkbox 'Use VISA Remote Server'. The controls 'IP / Hostname'and 'Port' will be enabled and can be altered.

IP / Hostname Contains the IP address or the hostname of the computer inthe network to which the Agilent 8164 is connected. Thiscomputer works as a VISA Remote Server. Please refer tothe VISA Remote Server section for more information.

Port Specifies the port number of the TCP/IP connection to theVISA remote server. The default port value is 3537.

GPIB Board This parameter gives the number of the GPIB board. Thedefault number is usually 0.

Address Defines the GPIB address of the Agilent 8164A.Timeout Describes the timeout for the laser remote connection.TLS Slot The Agilent 8164A is a mainframe which offers several slots

for different modules. This parameter contains the slotnumber. Most TLS modules for the Agilent 8164A have to bemounted to the back loadable slot 0.

Ando AQ4320DThis laser is an external laser source which has to be connected via a GPIB cableto the computer or to a different PC which works as a VISA Remote Server. Referto the VISA Remote Server section for more details.


© <2006> Thorlabs

Figure 15 Ando AQ4320D Configuration Window

Check Box If the external tunable laser source is used with a differentcomputer which acts as a VISA Remote Server set the checkbox 'Use VISA Remote Server'. The controls 'IP / Hostname'and 'Port' will be enabled and can be altered.

IP / Hostname Contains the IP address or the hostname of the computer inthe network to which the Ando AQ4320D is connected. Thiscomputer works as VISA Remote Server. Please refer to theVISA Remote Server section for more information.

Port Specifies the port number of the TCP/IP connection to theVISA remote server. The default port value is 3537.

GPIB Board This parameter gives the number of the GPIB board. Thedefault number is usually 0.

Address Defines the GPIB address of the Ando AQ4320D.Timeout Describes the timeout for the laser remote connection.

4.2.2.2 VISA Remote Server

The PMD5000 system offers the possibility to use external tunable laser sources(TLS) from third party manufacturer. Most of these TLS have a GPIB interface. Itis not absolute necessary to connect the external laser to the computer where thePMD5000 software is running but to another computer next to the PMD5000system. In this case it is required that this computer has network access andNational Instruments program Measurement & Automation full version is installed.The computer connected to the TLS works as a VISA Remote Server and thecomputer with the PMD5000 software acts as a VISA Remote Client. Thefollowing picture shows the configuration of the above described setup.

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Figure 16 External TLS with extra PC Configuration

Configure the VISA Remote ServerTo configure a VISA server the full version of the VISA runtime engine 3.0 or laterfrom National Instruments which is not supplied with the PMD5000 software isrequired.1. Start the NI Measurement & Automation software by clicking the 'START'

button from the left lower corner of your desktop and selecting 'All Programs /National Instruments / Measurement & Automation'

2. Select 'Tools / NI-VISA / VISA Options...' from the menu bar.

Figure 17 VISA Options

3. Now you can alter the VISA options. To enable access from certain or allcomputers select 'VISA Server / Security' from 'My System'. Add newpermissions to a certain computer in the network by entering the computername or to all computers by entering '*'. If the list is empty no system hasaccess to this VISA server.


© <2006> Thorlabs

Figure 18 VISA Server Security

4. Select the directory 'VISA Server' from 'My System'. Here you can start theVISA server by clicking on the button 'Start server now'. Furthermore, you canset the check box 'Run the VISA server on startup'.

Figure 19 Start VISA Server

5. Depending on your NI MAX version you may have to apply or save yourchanges.

4.2.2.3 SOP Controller Configuration

The SOP Controller is the DPC5500. Analog to the tunable laser the defaultconnection data are automatically loaded during the start up. Currently there isonly the DPC5500 polarization controller available.

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Figure 20 SOP Controller Configuration Window

The 'Communication Setup' tab contains all necessary information about theconnection to this module.

IP / Hostname Contains the IP address of the TXP mainframe. ThePMD5000 system consists of a TXP5016. This mainframehas a fixed IP address by default for example192.xxx.xxx.xxx. Please refer to the operating manual of theTXP5016 for more information about the IP address.The expression 'localhost' is only valid if the DPC5500 isoperated in a TXP5004 or TXP5001 mainframe.

Port Specifies the port number of the TCP/IP connection to theTXP5016 mainframe. The default port value is 2402.

Slot Defines the slot of the TXP5016 mainframe where theDPC5500 is installed.

Timeout Describes the timeout for the SOP controller remoteconnection.

The 'Measurement Setup' tab contains parameters for the module specificmeasurement setting.

Speed Index Specifies the time when polarization measurements aretaken which are averaged to generate a single resultpolarization. The measured polarization is used as controlcriteria to adjust the desired polarization. As smaller the indexas faster is the polarization controlling and therefore the PMDmeasurement process. If the laser source has a small poweror is unstable a higher 'Speed Index' should be used toaverage several polarization measurements for onepolarization control step.The following table shows the relation between index andaverage time.


© <2006> Thorlabs

Speed Index Average Time

3 30µs

4 100µs

5 300µs

6 1ms

7 3ms

8 10ms

Table 1 Speed Index DPC

Average Type You can choose between 'Current' and 'DOP' mode.The 'Current' mode is the standard mode. All polarizationstates are averaged which can yield a DOP less than 100% ifthere is a large SOP variance.The 'DOP' mode should only be used if depolarizationappears in the DUT.

Refer to the operating manual of the DPC5500 for more information about themeasurement and control parameters.

4.2.2.4 Polarimeter Configuration

The receiver is a polarimeter module. Depending on your PMD5000 system youcan have the fast in-line polarimeter (IPM5300) or (PAX5720IR3). From the'Select Polarimeter Type' selection you can make your choice.

Figure 21 Polarimeter Connection Setup Tab

The 'Communication Setup' tab contains all necessary information about theconnection to this module.

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IP / Hostname Contains the IP address of the TXP mainframe. ThePMD5000 system consists of a TXP5016. This mainframehas a fixed IP address by default for example192.xxx.xxx.xxx. Please refer to the operating manual of theTXP5016 for more information about the IP address.The expression 'localhost' is only valid if the IPM530 orPAX57xx polarimeter is operated in a TXP5004 or TXP5001mainframe.

Port Specifies the port number of the TCP/IP connection to theTXP5016 mainframe. The default port value is 2402.

Slot Defines the slot of the TXP5016 mainframe where thepolarimeter is installed.

Timeout Describes the timeout for the polarimeter remote connection.

The tab 'Communication Setup' of the IPM5300 and PAX57xx polarimeter areidentical. The 'Measurement Setup' tab for the polarimeters is different.

Figure 22 PAX57xx Polarimeter Measurement Setup Tab

Basic Sample Rate Specified in samples per seconds (from 66.667 to333.333 SPS). One basic period is captured during ahalf turn of the waveplate. The basic sample rate isdirectly related to the rotation frequency of the motor.

Number of Basic Periods The number of basic periods (half turns of thewaveplate) over which the photodiode current ismeasured. The default setting is two basic periods.The number of basic periods, together with the samplerate (rotation frequency) of the waveplate, can be usedto filter out unwanted modulation frequencies (noise).

Signal Averaging The photodiode current is measured over the Numberof Basic Periods selected previously. When measuring


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light of a low power, it may be advantageous to takean average of several photodiode currentmeasurements before the Fourier Analysis isperformed, thereby reducing the effects of noise orsignal fluctuations. The Signal Averaging parameterspecifies how many measurements should beaveraged.

Result Averaging On some occasions, e.g. when the PAX is integratedin a complex measurement system to measure PMDor PDL, it may be advantageous to take an average ofthe polarization data from several Fourier Analyses.The Result Averaging parameter details the number ofdata sets over which the polarization data is averaged.

For more information about the measurement settings of the PAX polarimeterrefer to the PAX57xx manual.

Figure 23 IPM5300 Polarimeter Measurement Setup Tab

Speed Index Specifies the time during polarization measurements aretaken which are averaged to generate a single resultpolarization. As smaller the index as faster is the polarizationmeasurement and therefore the PMD measurement process.If the laser source has a small power or is unstable a higher'Speed Index' should be used.The following table shows the relation between index andaverage time.

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Speed Index Average Time

2 10µs

3 30µs

4 100µs

5 300µs

6 1ms

7 3ms

8 10ms

9 30ms

10 100ms

11 300ms

Table 2 Speed Index IPM

Average Type You can choose between 'Current' and 'DOP' mode.The 'Current' mode is the standard mode. All polarizationstates are averaged which can yield a DOP less than 100% ifthere is a large SOP variance.The 'DOP' mode should only be used if depolarizationappears in the DUT.

Refer to the operating manual of the IPM5300 for more information about themeasurement and control parameters.

4.2.3 Connection

Before you can start a measurement you have to connect to the singleinstruments. Select 'System / Connect' from the menu or click on the icon'Connect to Measurement System' from the tool bar. The following windowappears and shows the status of the connection process. All devices (TLS, SOPcontroller and polarimeter) will be connected simultaneously. After all instrumentsare connected successfully this window will disappear automatically.


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Figure 24 Connection Status Window

To cancel the connection process, simply click on the button 'Cancel'. It may takethe entire time specified by the timeout feature until cancel is finished. Themaximum timeout of the 3 instruments has to be taken into account.

4.2.4 Measurement

The PMD5000 system offers a wide range of measurement data.The insertion loss (IL), the polarization dependent loss (PDL), the received opticalpower, the differential group delay (DGD), the resulting phase difference, theoutput fast principal state of polarization (PSP), the second order DGD, thepolarization dependent chromatic dispersion (PCD) as well as the PSP rotationrate are given each in a separated diagram over wavelength. Additionally, theDGD and the second order DGD are displayed in a histogram. The meanvaluesare also shown in the extra window 'Calculation'. Furthermore, you can get asingle measurement set for a certain wavelength by using a cursor. SeeCursor Control section for details. All parameters which effect the measurementas well as the control buttons are placed in the window 'Standard JMEMeasurement'.

The following figure shows the PMD5000 GUI with the graph selection.

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Figure 25 Selection of the Graph

4.2.4.1 Measurement Configuration

The 'Standard JME Measurement' window is shown in the following figure. Thiswindow can be hidden. Select 'View / Measurement Configuration' from the menuor the button 'View Measurement Configuration Panel' from the tool bar toshow or hide the 'Standard JME Configuration' window.

Figure 26 Standard JME Measurement Window


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In the data window you can enter the step width, the start and stop wavelength aswell as the output power of the tunable laser source. The start and stop can beentered in terms of wavelength (nm), frequency (THz) or wavenumber (1/cm).The power can be entered in mW or dBm. Select 'View / Preferences / DisplayOptions ...' from the menu to set your choice.

Step WidthThe first control is the wavelength step width. It is given only in nm. The minimalstep size depends on the used laser source. For the ECL5000D it is 1pm.The selected wavelength step must harmonize with the PMD of the DUT. You canchoose a wavelength step according to the following table or click on the button'Optimize Step Width' of the 'Standard JME Measurement' panel.

NOTEIf the selected step size is too high, ambiguities will occur in the phasemeasurement and the measurement will yield very low PMD values. If the stepsize is too low, inaccuracies due to only small changes of the DGD will increase.

Due to the phase periodicity of p (180°) any phase difference between the fastand slow principal state exceeding 180° can not be uniquely resolved, but will bemapped into the basic interval 0° … 180°. Therefore, the DGD valuescorresponding to phase differences larger than p can not be safely detected.Therefore, for every wavelength a maximum measurable DGD value exists whichcan be calculated by:

DGDmax*Dl < l2 / 2c

DGDmax depends on the wavelength step size: the smaller the step size, thelarger is the maximum measurable DGD value.The following table lists the maximum measurable DGD value according to thisformula for the wavelength range at 1550nm. Since the PMD value is the averagevalue of the DGD distribution a safe determination of the PMD value requires thateven DGD values much larger than the PMD value are unambiguously detected:i.e that they still meet the above requirement. Therefore, in the relationshipbetween the PMD value and the wavelength step size a safety factor isincorporated to give room for large DGD values. The built-in safty factor of 2 isappropiate for weak mode coupling as in isolators with narrow DGD distributions.Fibers with a strong mode coupling have a broad distribution (like the Maxwellian)and a saftx factor of 8 should be used. For detailed information about step widthand accuracy refer to the application note: Accuracy.

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Wavelength Step Size[nm]

1550nm Wavelength Range

Maximum measurableDGD [ps]

Safely measured PMD [ps] withmode coupling

weak strong

0.01 400 200 50.00

0.02 200 100 25.00

0.05 80.0 40.0 12.50

0.10 40.0 20.0 10.00

0.20 20.0 10.0 2.500

0.50 8.00 4.00 1.000

1.00 4.00 2.00 0.500

2.00 2.00 1.00 0.250

5.00 0.80 0.40 0.100

10.0 0.40 0.20 0.050

20.0 0.20 0.10 0.025

50.0 0.08 0.04 0.010

100 0.04 0.02 0.005

Table 3 Maximum measurable DGD / PMD

NOTEFor devices under test with low mode coupling, (e.g. with polarizationmaintaining fibers) i.e. with lower variations of DGD over wavelength,relatively high phase value above 90° as measurement results arerecommended to achieve the highest accuracy.

For devices under test with strong mode coupling, i.e. with strongfluctuations of DGD, the measured phase difference should cover the entireallowed range (0 … 180°) so that even peak phase values can bedetermined unambiguously and the best accuracy is achieved.

If working with a device with unknown PMD, start with the lowest possible stepsize. If the measured DGD values are narrowly distributed increase the step sizeso that the maximum measured phase value is slightly smaller than 180°. If themeasured DGD values exhibit a broad distribution with a tail, increase the stepsize until the entire phase range (0 … 180°) is used.

Start and StopThese parameters specify the start and stop wavelength for the DGDmeasurement scan. Consider that a data set at one wavelength supplies only thePDL, the insertion loss and the received optical power. To calculate the DGD twoJones matrices are necessary. The second order DGD can be computed fromtwo DGD values at different wavelengths.


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Optimize Step WidthThe step size can also be determined automatically. Click the button 'OptimizeStep Width' in the 'Standard JME Measurement' window.At the start wavelength of the current measurement configuration the step size isdetermined by a search algorithm for the optimal value depending on the deviceunder test. It is automatically entered in the control 'Step Width'. The determinedstep width has a security factor of 2 that means the phase of the calculated stepwidth achieves a maximum value of 90°.

NOTEThis function is useful for the DUT with a relatively constant DGD overwavelength. If you have a DUT with a strong changing in DGD or a narrowbandwidth device and you start the scan outside the pass band this optimizingstep width function will not work properly.

Laser SettingsThe laser can be switched on individually by a click on the 'Switch Laser on'button. The actual wavelength and received power from the polarimeter areshown below this button. If no PMD scan is running the actual wavelength of thelaser corresponds to the start wavelength. The laser power can be set manually indBm or mW. To change from dBm to mW select 'View / Preferences / DisplayOptions ...' from the menu.

4.2.4.2 Start a Single Measurement Scan

To start a measurement scan click on the 'Start' button in 'Standard JMEMeasurement' window or click on the 'Run New Measurement' button in thetool bar. Another possibility to start a scan is to press the key 'F5' on yourkeyboard. The measurement starts immediately. The laser is set to the enteredscan start wavelength / frequency and will be switched on automatically. Then theDPC5500 adjusts the 3 linear polarization states and the polarimeter measuresthe output polarizations. This will be repeated for all wavelength points.

A running scan can be stopped at any time by just clicking on the 'Stop' button inthe 'Standard JME Measurement' window or the 'Stop Running Measurement'button in the tool bar. The 'F6' key is the short cut to interrupt themeasurement scan.

All measured values are continuously displayed in the diagrams showing thedependency on the wavelength. After the first Jones matrix is calculated only theIL, received optical power and PDL are available. To obtain the first DGD valuetwo Jones matrices at different wavelengths are necessary. The second orderDGD is available after three measurement points.

4.2.4.3 Repeated Measurement Scans

The PMD5000 system offers the feature to perform repeated DGD measurementscans over a long period of time with an optional interlaced loop. If connectedselect 'Measurement / Repeated Scan...' from the menu. The following panelappears.

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Figure 27 Repeated Scan Setup

Target DirectoryThe target directory specifies the directory where the result files with themeasurement data are stored. You can change the target directory by clicking thebrowse button .

Target File PrefixThis string defines the prefix of the data files. In the example above the name of adata file would be RepMeasFile_0000000000.pmd. The number after the prefixwill be increased for each measurement scan. If there is another file with thesame prefix in the specified target directory a warning panel appears.

File FormatThis ring control contains the types of files which can be used to store themeasured data. A *.pmd file contains all necessary information to calculate theDGD and PDL data. It is only for reloading the data into the PMD application. A*.csv file contains all information which are shown in the PMD application. Thiskind of file cannot be loaded again into the application. It can be used to processthe data with third party software. Also see Saving Data section.It is possible to select either a *.pmd or a *.csv file or both of them as target files.

CSV Export SetupThe controls for the CSV export setup are only accessible if a *.csv file is selected


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as target file.

SeparatorA *.csv file is a file containing a list of comma separated values. However, theseparator can be selected using the ring control 'Separator'. A comma [ , ], asemicolon [ ; ], a tabulator or a pipe [ | ] can be chosen as a separator.

CommentHere you can add a certain comment to the file.

TimerThe PMD5000 application offers the feature of two interlaced timer loops forrepeated measurement scans. This means it is not only possible to arrangerepeated measurements with a certain time frame but also to perform severalmeasurements with a certain time frame then have another longer time frame forall these measurements and start it again.This can be applied for example to an already installed fiber. Starting themeasurement cycle in the morning beginning with 20 scans at a time in intervalsof 1 minute per scan with 30 seconds per scan. Then a larger time frame of letssay 1 hour defines the beginning of the next cycle of 20 measurement scan. Atthe end you can determine the DGD together with all the other optical data over afull day or more in an interval of 1 hour and 20 scans per cycle.

The following diagram shows the principle of interlaced measurement scans.The 'Scan Trigger Timer' defines the time frame of the single scans. If the timeframe is shorter than an actual scan the following measurement is startedimmediately as it can be seen in 'Scan Example 2'.The 'Interlace Timer' specifies the time frame for a complete measurement scancycle. If the time frame is shorter than a scan cycle as shown in 'Scan Example 3'the next cycle is started immediately.The time frames are set correctly as it is demonstrated in 'Scan Example 1'.

Figure 28 Repeated Scan Trigger

Scan Trigger Timer

Start Time RasterThis control defines the time frame beginning with the start of a singlemeasurement scan until the start of the next measurement scan. If the scanlasts longer than the specified time frame the next measurement is started

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immediately.

RepetitionsThis control sets the numbers of single measurement scans for one cycle. Upto 65500 repetitions are possible.

Start next Scan immediatelyThis check box enables / disables the 'Start Time Raster'. If checked, a singlescan will be immediately started after the previous scan has finished.

Start IndexThis parameter defines the starting number for the data file. The default is 1and the first data set would be stored in the fileRepMeasFile_0000000001.pmd. Any number between 0 and 4294967295will be accepted.

NOTEThe largest number is 4294967295. If this number is reached and more scansare needed to be recorded the counter will be set to 0 and it starts again. Thismeans an already existing file with the number 0 and the following files will beoverwritten.

Interlace Timer

Activate Interlace TimerThis check box enables / disables the interlace timer.

Start Time RasterThis control defines the time frame beginning with the start of a measurementscan cycle until the start of the next measurement scan cycle. See figure'Repeated Scan Trigger'. If the scan cycle lasts longer than the specified timeframe the next scan cycle is started immediately.

RepetitionsThis control sets the numbers of measurement scan cycles. Up to 65500repetitions are possible.

Minimum Measurement TimeThe minimum time for the complete repeated measurement scan is given. It iscalculated under the assumption of an infinite short scan time. If a single scan ora scan cycle lasts longer than the specified time frame the repeatedmeasurement scan will also last longer than the displayed time.

NOTEIt is possible to set the repetitions and time frames to large values so that ameasurement time of several years would be needed to perform this repeatedmeasurement scan.

Start a Repeated MeasurementClick the 'Start' button to start a repeated measurement. A panel appears whichshows the progress of the repeated measurement process. All analysis tools to


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view measurement data can still be used during the repeated measurementprocess.

Figure 29 Repeated Scan Progress

Abort a Repeated Measurement ProcessClick the 'Close' button to abort a running repeated measurement scan.

4.2.5 Measurement Results

A general survey is given in the 'Calculations' window. This panel can be hiddenor shown, respectively, by clicking on the button 'View Calculations Panel' . Theminimum and maximum DGD value of a specified wavelength range aredisplayed as well as the average magnitude of the PDL and IL. Furthermore, thePMD (the mean DGD) is shown as numerical average (avg) and as root meansquare (rms). The PMD coefficient (Coeff) and the second order PMD (SOPMD)are also displayed. Even during the scan these data are constantly updatedbased on the number of up to the measured samples. Only the values in therange defined by 'Start' and 'Stop' are considered. Please refer to theData Analysis section for more details.

Figure 30 Calculations Window

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Recall that the PMD value is either the mean average ('Avg') or the RMS average('RMS') of the DGD distribution. Both values are given for convenience.The RMS PMD value is a measure for the width of the DGD distribution, whereasthe mean PMD value is the average of the distribution.

For an ideal long fiber with strong mode coupling the mean and the RMS PMDvalue are correlated by a constant factor. However, there is no correlation for nonfiber devices or poor mode coupled devices.

The so called PMD coefficient is indicated by "Coeff" (RMS PMD/Ö(Length/km)).This value is only relevant for long fibers with high mode coupling since theabsolute PMD scales with the square root of the fiber length. The PMD coefficientis then a figure of merit to compare the PMD of different fiber types independentof the fiber length.Enter the correct value into 'Fiber Length' to calculate the coefficient. If there is nostrong mode coupling in your device or you don't know the behavior, simply setthe length to 1.0km.

The dependency of the DGDs from wavelength can change due to ambientconditions, especially for long fibers with high mode coupling. The diagrams ofthe device under test may look completely different when taken under differentenvironmental conditions.

However, the mean and RMS PMD value remain (for ideal components)unchanged. I.e. the temporal average of the DGD distribution at one specificwavelength is identical to the average of the DGD distribution sampled at onespecific time but over many wavelengths. This has been proven mathematically.Please refer to the application note Accuracy for more details.


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4.2.5.1 Diagrams

All measurement data are shown in several diagrams over the wavelength evenduring the scan. Choose the appropriate graph from the 'Graph Display' selectionin the tool bar.

4.2.5.1.1 PDL Diagram

The PDL graph shows the measurement data of the polarization dependent lossvs. wavelength. It is given in [dB]. For each wavelength point exists a measuredPDL value.

Figure 31 PDL Diagram

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4.2.5.1.2 IL Diagram

The graph IL shows the measurement data of the insertion loss vs. wavelength. Itis given in [dB]. For each wavelength point a measured IL value exists. You canenter an additional 'System Loss' which will be subtracted from the measured IL.You can alter this parameter by selecting 'View / Preferences / Display Options...'. See Display Options section for more details.

Figure 32 IL Diagram


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4.2.5.1.3 Power Diagram

The graph Power shows the measurement data of the detected power vs.wavelength at the polarimeter. It is given in [dBm] or [Watt]. For each wavelengthpoint a measured power value exists.

Figure 33 Power Diagram

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4.2.5.1.4 DGD Diagram

The graph DGD shows the Differential Group Delay vs. wavelength. It is given in[ps]. To obtain a single DGD value two Jones matrices are necessary. Theresulting DGD value is then displayed for the mean value of both wavelengthpoints. That means the DGD calculated from the Jones matrix at l1 and l2 ismapped at (l1+l2)/2. Scanning N wavelength points yield N-1 DGD values.

Figure 34 DGD Diagram


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4.2.5.1.5 DGD Histogram

The DGD histogram shows the statistical distribution of the measured DGDvalues. A long standard fiber will show a Maxwell distribution. Only DGD valueswithin the calculation range defined by 'Start' and 'Stop' in the 'Calculations' panelare considered.The range of the x- axis is set to the minimum and maximum value of the data setdefined by the calculation range. The x- axis is split into a fixed number ofcolumns equally spaced. The number of columns can be set selecting 'View /Preferences / Display Options ...'. See Display Options for more information.The occurrence is given in % of all DGD values within the calculation range.

Figure 35 DGD Histogram

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4.2.5.1.6 Phase Diagram

The Phase graph shows the phase difference between the fast and slow principalstate in degrees. The phase range is limited mathematically to 0 ... 180°. Youmust ensure that the phase shift remains in this range by selecting a suitablewavelength step. The DGD is calculated from the phase.

Figure 36 Phase Diagram


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4.2.5.1.7 2nd Order DGD Diagram

The graph DGD 2. Order shows the second order DGD vs. wavelength. TheSODGD is given in [ps²]. To obtain a single SODGD value two first order DGDvalues and their corresponding PSPs are necessary. The resulting SODGD valueis then displayed for the mean value of the wavelength points of both DGDvalues. That means the SODGD calculated from the DGD1 corresponding tol(DGD1) and DGD2 corresponding to l(DGD2) is mapped at(l(DGD1)+l(DGD2))/2.Since two DGD values are used to calculate a single SODGD value and twoJones matrices are necessary to calculate a single DGD value Jones matrixmeasurement at three different wavelengths has to be done. Scanning Nwavelength points yield N-2 SODGD values.

Figure 37 2nd Order DGD Diagram

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4.2.5.1.8 2nd Order DGD Histogram

The SODGD histogram shows the statistical distribution of the measured SODGDvalues.The range of the x- axis is set to the minimum and maximum value of the data setdefined by the calculation range. The x- axis is split into a fixed number ofcolumns equally spaced. The number of columns can be set selecting 'View /Preferences / Display Options ...'. See Display Options for more information.The occurrence is given in % of all SODGD values within the calculation range.

Figure 38 SODGD Histogram


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4.2.5.1.9 PSP Diagram

The graph PSP Stokes graph shows the fast Principal State of Polarization vs.wavelength. The PSP is given as normalized Stokes parameter.

Figure 39 PSP Diagram

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4.2.5.1.10 PCD Diagram

The second order DGD is the derivative of the DGD vector. It consists of twoparts the polarization dependent chromatic dispersion (PCD) and the PSProtation rate (k). Please refer to the Definitions and Terms section for moreinformation.In the graph PCD the chromatic dispersion is displayed. It is given in [ps²].

Figure 40 PCD Diagram


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4.2.5.1.11 PSP Rotation Rate Diagram

In the PSP rotation rate (k) graph is displayed. It is given in [ps²].

Figure 41 PSP Rotation Rate Diagram

4.2.5.2 Data Analysis / Calculations Window

The PMD5000 is based on the Jones Matrix Eigenanalyzis (JME). The 'raw' dataof a JME measurement is the Jones matrix. This is the base for all calculations todetermine the PDL, DGD, PMD etc. Once the Jones matrices for severalwavelengths are measured all these data can be calculated.

If a wavelength scan is started the determined measurement data are updatedfrequently. After a scan is finished all measurement results are displayed and themean values are calculated over the complete wavelength range defined by 'Start'and 'Stop' of the 'Calculations' window.

Especially for narrow bandwidth devices with steep edges the obtained databeyond the bandpass can distort the measurement results of the mean values.Therefore, it is convenient to adjust calculation boundaries. This can be done inthe 'Calculations' window.

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The 'Calculation' window can be hidden. Select 'View / Calculation Window' fromthe menu or click the button 'View Calculation Panel' from the tool-bar toenable or disable the display of the 'Calculations' window.

The controls 'Start' and 'Stop' define the boundaries of the mean valuecalculations. You can change these parameters any time. If the calculation rangecontains one or more invalid data sets (no measurement data available at thesewavelengths, e.g. because of low power at the polarimeter) only the valid datasets will be used. If no valid values are inside the specified calculation range novalues are displayed.

The boundaries will be displayed as vertical cursors in the diagram. The cursorsare valid for all diagrams. They are only visible if the displayed range containsthese boundaries. The 'DGD Histogram' and the 'DGD 2. Order Histogram'include only the values which are inside of the specified range. Refer to theCursor Control section for more information about the cursors.

The parameter 'Fiber Length' serves to calculate the PMD coefficient for thedevice under test. It is the PMD value scaled to square root of the length of thedevice. If the length is unknown, set the length to 1.0 km.

The mean value of the PDL and IL are shown in the first two rows in dB. Theminimum and the maximum DGD are also shown followed by the arithmetic meanand the root mean square of the DGD indicated by PMD avg and PMD rms,respectively. DGD and PMD are given in ps. The PMD coefficient in ps/Ökm andthe second order PMD (SOPMD) in ps² are also presented.

The 'Measurement' column shows the values of the current measurement. Eachmeasurement can be set to reference for comparison. These data are shown inthe 'Reference' column. To set a measurement scan to reference click the button'Make Measurement Data to Reference' from the tool-bar, select'Measurement / Make Reference' from the menu, right click on the diagram andselect 'Make Reference' or press the key 'F7'. Furthermore, you can load a savedfile (*.pmd) as reference. Choose 'File / Open Reference Data ...' from the menu.


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4.2.5.3 Cursor Control

The application offers several cursor functions to navigate inside the graphs andto display the areas of interests. There are two different kinds of cursors: two'Boundary' cursors and a 'Data' cursor. They can be distinguished by their color.The color can be set for these cursors individually. Refer to theDisplay Configuration section for more details.The cursors are vertically drawn and the x- position (wavelength) is identical foreach diagram. The histograms do not offer any cursor functions. It may happenthat no cursors are visible within a diagram. In this case the cursors are outside ofthe displayed wavelength range which can occur by zooming into a range ofinterest.

Boundary CursorsThe boundary cursors define the wavelength range and its correspondingmeasurement results to calculate the mean values of PDL, DGD etc. These meanvalues are shown in the 'Calculations' panel. See the Data Analysis section. Thecursors can be set by entering the numerical values into the 'Start' and 'Stop'controls in the 'Calculations' panel or by drag and drop them with the mousecursor inside the diagram when working in the 'Move Cursor Mode'. The'Calculations' panel can be hidden or shown clicking the button 'View CalculationsPanel' .

Figure 43 Boundary Cursor

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Data CursorThe data cursor represents a measurement value at a single wavelength. Youcan manually enter a wavelength in nm in the control 'Wavelength' in the 'Cursor'panel. In the field below you will see the values for this single wavelength point forthe actual measurement as well as for the reference. In all diagrams this 'Data'cursor is shown and can also be set by drag and drop in the 'Move Cursor Mode'.The 'Cursor' panel can be hidden or shown clicking the button 'View Cursor Panel'

.

Figure 45 Data Cursor


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Figure 46 Cursor Window

Move Cursor ModeThis mode is set either by selecting 'Graph / Cursor Mode' from the menu or byclicking on the 'Move Cursor Mode' button from the tool bar. Now you canplace a cursor at any position in the diagram.The numerical values for the boundary cursor will be updated in the controls'Start' and 'Stop' in the 'Calculations' panel. The mean values are also refreshedimmediately. The numerical values for the data cursor are interpolated from thetwo adjacent data points and displayed in the window 'Cursor'.

Zoom Horizontal ModeThis mode is set either by selecting 'Graph / Zoom horizontal' from the menu orby clicking on the 'Zoom Horizontal Mode' button from the tool-bar.Select with the mouse cursor a point on the diagram. Click and hold the leftmouse button and draw a rectangle whose width marks the new view area. Nowrelease the mouse button. This zoom function will only affect the range of the x-axis. The range of the y-axis remains.

Zoom Vertical ModeThis mode is set either by selecting 'Graph / Zoom vertical' from the menu or byclicking on the 'Zoom Vertical Mode' button from the tool-bar.Select with the mouse cursor a point on the diagram. Click and hold the leftmouse button and draw a rectangle whose height marks the new view area. Nowrelease the mouse button. This zoom function will only affect the range of the y-axis. The range of the x-axis remains.

Zoom Rectangular ModeThis mode is set either by selecting 'Graph / Zoom Rectangle' from the menu orby clicking on the 'Zoom Rectangular Mode' button from the tool-bar.Select with the mouse cursor a point on the diagram. Click and hold the leftmouse button and draw a rectangle whose dimension marks the new view area.Now release the mouse button. This zoom function will affect both the range ofthe y-axis and the x-axis.

Zoom OutYou can zoom out of the graph either by selecting 'Graph / Zoom out' from the

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menu or by clicking on the 'Zoom Out' button from the tool-bar or by pressingthe 'Page Up' key.It will zoom out to the double range in x- and y- direction if you are in the 'MoveCursor Mode' or 'Zoom Rectangular Mode'. If the 'Zoom Horizontal Mode' or'Zoom Vertical Mode' is active only the x- or the y- axis, respectively, is affected.

Zoom Out to Full ViewYou can zoom out to full view either by selecting 'Graph / Zoom 100%' from themenu or by clicking on the 'Zoom Out to Full View' button from the tool-bar orby pressing the 'Home' key.The x- and the y- axis are affected if the 'Move Cursor Mode' or 'ZoomRectangular Mode' is active. The other cursor modes will only apply to theaccording axis.

User defined View AreaThe displayed zoom range can be defined manually by selecting 'Graph / SetView Area ...' or by pressing the 'End' key. A popup panel appears and the rangefor the x- and y- axis can be set individually. The x- axis of all diagrams is effectedand the y- axis only for the current graph.

Figure 47 Graph View Settings

4.2.5.4 Saving Data

The measurement data can be saved for later use with third party software likeMicrosoft Excel™ or Mathlab™. The PMD5000 software offers two different kindsof data handling. The first one saves the *.pmd data which includes the Jonesmatrices for all wavelength points but no measurement results like PDL and DGD.The second method exports all measurement results including PDL, DGD, PSP,SODGD and the mean values in a *.csv file which is human readable and can beeasily imported into third party programs.

Save Measurement / Reference DataThe *.pmd file data contains the measured Jones matrices for each wavelengthpoint and the determined power from the polarimeter and the insertion loss.These data is sufficient to calculate all optical parameters like PDL, DGD etc.Therefore these data cannot only be saved but also reloaded. It is very possibleto perform measurement scans, save the data and analyze it at a later time withall features that the PMD software offers.


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To save the measurement data to a *.pmd file select 'File / Save MeasurementData ...' from the menu or click the button 'Save Measurement Data to File' from the toolbar or use the shortcut keys 'Ctrl' + 'S'. A file dialog window appearsand you can choose the filename and directory. The file extension of this kind offile is *.pmd.

Similar to this procedure the current reference data can also be saved to a pmd-file by selecting 'File / Save Reference Data ...' from the menu or using theshortcut keys 'Ctrl' + 'Shift' + 'S'.

A pmd- file can be loaded by selecting 'File / Open Measurement Data ...' fromthe menu or click the button 'Load Measurement Data from File' from thetoolbar or use the shortcut keys 'Ctrl' + 'O'. A file dialog panel appears and youcan select your *.pmd file. You can also load a pmd- file directly as referencedata. Select 'File / Open Reference Data ...' from the menu or use the shortcutkeys 'Ctrl' + 'Shift' + 'O'.

Export DataThe measurement data can be exported to a *.csv file. All available data includingthe mean, min and max values as well as all determined values over wavelengthcontaining also the Jones matrices are stored in this file. The data can only beexported but not reloaded into the program for further manipulation. The data canbe easily processed with third party software e.g. Microsoft Excel™ orMathLab™.

To export the current measurement data to a *.csv file select 'File / ExportMeasurement Data...' from the menu. A popup panel appears and you canchoose the separator character and enter a comment. Finally a file dialog windowappears and you can choose the filename and directory. The prefix of this kind offile is *.csv. The reference data can be handled in the same way.

An exported file contains a header with a date and time-stamp. The time is givenas a time-stamp in seconds elapsed since 01.01.1900 as well as date and time ina common format. The scanner name is also listed which is the 'Standard JMEScan' as the only available scanner at this time. Furthermore, there are thenumbers of the measurement sample values and a user defined comment.

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Figure 48 Export File Header

The next part contains the minimum and maximum values of the completemeasurement range. This includes the IL, power, PDL, DGD and second orderDGD. You will also find the average values for each of these parameters for theselected wavelength range. See the Data Analysis section for more informationabout the range selection.

Figure 49 Export File General Values

The third part contains the actual measurement data. Since the computed datahas different wavelength correlation there are three sections. The received powerand the insertion loss (IL) are measured for each wavelength as well as the Jonesmatrix. The PDL is calculated from the Jones matrix and therefore also mappedto a certain wavelength point. A time-stamp also exists for each wavelength step.

The DGD, the phase and the input and output PSPs are calculated from twoJones matrices at two different wavelengths. On account of this all thesemeasurement values are mapped to the mean value of both wavelength stepswhich is indicated by '1st Order Wavelength'.

Similar to that the '2nd Order Sample Values' like SODGD, PCD and PSP rotation


© <2006> Thorlabs

rate are determined from the DGDs and PSPs at two different wavelength steps.These values are correlated to the '2nd Order Wavelength' which is the averageof both wavelengths of the DGD / PSP.

Figure 50 Export File Measurement Values

Measurement Sample ValuesTime-Stamp - Time-stamp for each measurement given in seconds and

starting at 0s for the first measurement at the startwavelength.

Sample Wavelength - Actual wavelength, frequency or wavenumber for themeasurement of the received polarization. The wave unitdepends on the user settings.

Output Power 0 - Output power given in dBm or mW received at thepolarimeter for horizontal linear input polarization. Thepower unit depends on the user settings.

Output Power 45 - Output power given in dBm or mW received at thepolarimeter for linear input polarization with 45° azimuth.The power unit depends on the user settings.

Output Power 90 - Output power given in dBm or mW received at thepolarimeter for vertical linear input polarization. Thepower unit depends on the user settings.

Insertion Loss 0 - Insertion loss (IL) given in dB for horizontal linear inputpolarization.

Insertion Loss 45 - Insertion loss (IL) given in dB for linear input polarizationwith 45° azimuth.

Insertion Loss 90 - Insertion loss (IL) given in dB for vertical linear inputpolarization.

PDL - Polarization dependent loss given in dB.JM00R - Absolute value of the element 00 of the Jones matrix.JM00Phi - Phase of the element 00 of the Jones matrix given in

radiant.JM01R - Absolute value of the element 01 of the Jones matrix.JM01Phi - Phase of the element 01 of the Jones matrix given in

radiant.JM10R - Absolute value of the element 10 of the Jones matrix.JM10Phi - Phase of the element 10 of the Jones matrix given in

radiant.JM11R - Absolute value of the element 11 of the Jones matrix.

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JM11Phi - Phase of the element 11 of the Jones matrix given inradiant.

The Jones matrix is arranged as follows:

Figure 51 Jones Matrix Form

1st Order Sample Values1st Order Wavelength - Mean value of the two wavelengths corresponding to the

Jones matrices which are used to calculate the followingparameters. The actual wave unit depends on the usersettings. It can be [nm] for wavelength, [THz] forfrequency or [1/cm] for the wavenumber.

DGD - Differential group delay given in ps.Phase - Phase given in degrees.Output PSP Stokes 1 - Stokes parameter 1 of the Principal State of Polarization

for the Output.Output PSP Stokes 2 - Stokes parameter 2 of the Principal State of Polarization

for the Output.Output PSP Stokes 3 - Stokes parameter 3 of the Principal State of Polarization

for the Output.Input PSP Stokes 1 - Stokes parameter 1 of the Principal State of Polarization

for the Input.Input PSP Stokes 2 - Stokes parameter 2 of the Principal State of Polarization

for the Input.Input PSP Stokes 3 - Stokes parameter 3 of the Principal State of Polarization

for the Input.

2nd Order Sample Values2nd Order Wavelength - Mean value of the two wavelengths corresponding to

the DGD and PSP, respectively, which are used tocalculate the following parameters. The actual wave unitdepends on the user settings. It can be [nm] forwavelength, [THz] for frequency or [1/cm] for thewavenumber.

2nd Order DGD - Second order differential group delay given in ps².PCD - Polarization dependent Chromatic Dispersion given in

ps².PSP Rotation Rate - Rotation rate of the PSPs.

4.2.6 Program Navigation

The PMD5000 software offers different possibilities to navigate through itsextensive functions. The toolbar features several shortcuts for function which ofcourse can also be accessed via the menu bar. Furthermore, there are controls


© <2006> Thorlabs

and buttons in the 'Standard JME Measurement', 'Calculations' and Cursorwindow.

4.2.6.1 Menu Bar

The PMD5000 application has several menu items.

File MenuThe 'File' menu contains all functions for saving, loading and exportingmeasurement data.You can save the current measurement data in a *.pmd file. This kind of file canbe loaded into the application. You can also save and load reference datadirectly.The differences between saving and exporting data is the used file format. Asaved *.pmd file can be loaded in the application whereas an exported *.csv filecannot. Exported files are human readable and can be easily imported into a thirdparty application.

Figure 52 File Menu

System MenuIn the 'System' menu you find all functions regarding your actual PMD5000system. You can configure your system and connect / disconnect the completesystem. Refer to the Configuration section for further information.

Figure 53 System Menu

Measurement MenuAll functions regarding the measurement configuration and control are listed inthe 'Measurement' menu.A PMD measurement scan can be started or stopped via this submenu.Repeated scans can be done as well as setting the current measured data asreference or delete the reference from the memory.

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Figure 54 Measurement Menu

View MenuThe 'View' menu contains all functions to configure the display. The 'StandardJME Measurement', 'Calculations', 'Cursor' and the 'Graph Legend' windows aswell as the reference graph can be shown or hidden. Furthermore the data whichare shown in the graph can be selected. A print function enables to plot either thecomplete panel or just the graph window. The colors of the graph such asbackground and plotted curves are user adjustable. Select 'Preferences... / Color...' to set the desired view. You can also reset the colors to factory default at anytime. See the Display Configuration section for details. Furthermore, the displayoptions such as power and wave unit can be set by selecting 'Preferences /Display Options ...'. Refer to the Display Options section for more information.

Figure 55 View Menu

Graph MenuAll functions to zoom and resize the graph are listed in the menu 'Graph'.The 'Set View Area ...' function opens a panel where you can enter theboundaries for the new view area as numerical values.The 'Cursor Mode' enables to drag and drop the data cursor which can be set toany position in the graph. 'Zoom horizontal' and 'Zoom vertical' will zoom thegraph only in horizontal or vertical direction, respectively. The forth cursor mode'Zoom Rectangle' allows to assign a rectangular area as the new view area.The 'Zoom out' function will double the current displayed range in x- and y-direction if you are in the 'Move Cursor Mode' or 'Zoom Rectangular Mode'. If the'Zoom Horizontal Mode' or 'Zoom Vertical Mode' is active only the x- or the y-axis, respectively, is affected.To get all data visible, select the function 'Zoom 100%' if the 'Move Cursor Mode'or 'Zoom Rectangular Mode' is active. The other cursor modes will only apply tothe according axis.


© <2006> Thorlabs

Figure 56 Graph Menu

Help MenuYou will find the online help in the menu 'Help'. Furthermore, there is a convenientway to visit the Thorlabs Web page to check for the latest drivers or softwareversions for example. You can also check the current version by selecting'About...'.

Figure 57 Help Menu

4.2.6.2 Tool-Bar

The tool-bar offers an easy access to important functions.

Figure 58 Tool-Bar

Opens an existing file (*.pmd) with saved Jones matrices. The data is usedto calculate PDL, PMD etc.Saves the Jones matrices of the current measurement in a file (*.pmd).This is 'raw' data only. Calculated data such as PMD or DGD vs.wavelength are not available in this file. To obtain the data from a file usethe 'Export' function 'File / Export ...' from the menu bar.Connects the single modules (laser, SOP controller and polarimeter).Disconnects the single modules (laser, SOP controller and polarimeter).Opens the configuration panel to adapt your current system settings.Starts a PMD measurement scan.Stops a running PMD measurement scan.Transfers the current measurement data as reference data.Shows / hides the measurement configuration panel.Shows / hides the calculations panel.Shows / hides the cursor panel.Shows / hides the reference graph.Shows / hides the graph legends.Enables the cursor mode. You can move the data cursor to a certain pointin the graph. The data corresponding to this point will be shown.

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Enables the zoom horizontal mode.Enables the zoom vertical mode.Enables the zoom rectangular mode.Zooms out by factor 2.Zooms out to full view.Opens an information window about the program.Opens the windows help for the PMD5000.

4.2.6.3 Display Functions

All functions to manipulate the diagram display can also be easily accessed by aright click on the diagram area. The following menu appears.

Figure 59 Display Functions

The x- and y- axis range can be set numerically by choosing Set View Area .... Apanel appears and the desired range can be entered.The Mouse Tool contains the curser modes which include Move Cursor Mode,Zoom Horizontal, Zoom Vertical and Zoom Rectangle.Zoom Out will zoom out to the double range in x- and y- direction if you are in the'Move Cursor Mode' or 'Zoom Rectangular Mode'. If the 'Zoom Horizontal Mode'or 'Zoom Vertical Mode' is active only the x- or the y- axis, respectively, isaffected.Zoom 100% will zoom out to full view for x- and y- axis only if 'Move Cursor Mode'or 'Zoom Rectangular Mode' are active and affects the corresponding axis if'Zoom Horizontal Mode' or 'Zoom Vertical Mode' is selected.Make Reference will set the current measurement data to reference.Clear Reference will delete the reference data from the diagram and memory.The reference data will not be available afterwards. If you just want to hide thereference data from the diagram use the button 'View Reference Graph' fromthe tool-bar.View includes all subpanels which can be hidden (Measurement Configuration,Calculation Window, Cursor Position, Reference Data and Graph Legends).Print offers an easy access to the print functions which contains the Full Window... mode, the complete program window will be printed, and the Graph only ...mode, only the diagram panel will be printed.Preferences contains the Color ... setup and the Display Options ... setup.


© <2006> Thorlabs

4.2.7 Display Configuration

The GUI of the PMD5000 is divided into the menu and tool-bar and the panelsection which is subdivided into several windows. All functions for configurationand control can be accessed via the menu bar. See the Program Navigationsection for more information. The most important functions can be easily calledusing the tool-bar. Refer to the Tool-Bar section.

There are several windows containing the measurement settings and results. Allwindows but the graph can be hidden for more concision. Select 'View /Measurement Configuration' from the menu or click the button 'ViewMeasurement Configuration Panel' from the tool-bar to show or hide the'Standard JME Measurement' window. The 'Calculations' window can bedisplayed or hidden by selecting 'View / Calculation Window' or clicking on thebutton 'View Calculations Panel' . The 'Cursor' window can be similarly handledvia 'View / Cursor Position' or the button 'View Cursor Panel' .

Two different data sets can be shown together in the graph as well as in the'Calculations' and 'Cursor' window at the same time. These two data sets arecalled 'Measurement Data' and 'Reference Data'. You can transfer measurementdata to reference data. Select 'Measurement / Make Reference' from the menu orclick the button 'Make Measurement Data to Reference' . You can also load analready saved data file as reference (Select 'File / Open Reference Data...' fromthe menu.). If you have loaded reference data you can show or hide them byselecting 'View / Reference Data' from the menu or clicking the button 'ViewReference Graph' from the tool-bar.

Especially if more than one curve is displayed in the graph for example in the'Output PSP Stokes' mode it is convenient to have a legend showing the name ofthe several curves. To display or hide the legend select 'View / Graph Legends'from the menu or click the button 'View Graph Legends' from the tool-bar.

The data displayed in the diagram can be set by choosing 'View / Graph / ...' fromthe menu or directly via the tool-bar from the selector 'Select Graph Display'.

Figure 60 Graph Selection

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4.2.7.1 Color Setup

The colors of the graph and its curves can be adjusted by selecting 'View /Preferences / Color...' from the menu. The following window appears and you canset the colors to the desired value. If you click on the button 'Default' the factorydefault will be valid. All changes will be saved after you confirm it with a click on'OK'.

Figure 61 Color Setup

4.2.7.2 Display Options

There are several display options which can be set by selecting 'View /Preferences / Display Options ...'. The following setup panel appears.


© <2006> Thorlabs

Figure 62 Display Options Setup

Autoscale Wavelength Axis on Scan StartIf this check box is set the x- axis view area is automatically set to the currentscanner wavelength range when a new scan is started.

Autoscale Calculation Range on Scan StartIf this check box is set the start and stop wavelength of the 'Calculations' windowis set to the same values as the current scanner start and stop wavelength whena new scan is started.

Number of Histogram ColumnsThis parameter defines the number of columns of the DGD and DGD 2. Orderhistogram. The default value is 50.

System LossThe system loss specifies a constant insertion loss over wavelength. This offsetwill be not displayed in the IL diagram. That means if a system loss of 1dB isdefined and the measured insertion loss is actually 2dB only 1dB insertion loss isshown in the IL diagram.

Power UnitYou can choose the power unit in dBm or Watt [W].

Wave UnitThe wave unit can be displayed in wavelength [nm], frequency [THz] orwavenumber [1/cm].

Service and Maintenance

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5 Service and Maintenance

5.1 Troubleshooting

· TXP Card does not work at all :

· Look if the card is inserted properly into the TXP mainframe and the ejectorhandle has snapped into its position.

· Look if the mainframe is powered up (the LED light is on).· Try to insert the card in another slot. Maybe the internal fuse of the slot has

opened (refer to the mainframe manual for changing the fuses).· See also the Trouble-shooting section of the card's specific user manual.

· PMD of a polarization maintaining fiber (PMF) is not constant over wavelength :

· The step width is too large. Decrease the step width to an according size.Refer to Table 3 in the Measurement Configuration section. Before youstart the measurement scan use the function 'Optimize Step Width'.

· Also see the Measurement of Fibers application note.

· Measurement is running but the diagram is not updated with new measurementvalues :

· The last diagram view area range is still valid. That means if the wavelengthrange and / or the new measured data are different from the previousmeasurement the new data are outside of the current displayed range.Select 'Graph / Zoom 100%' from the menu or the button 'Zoom Out to FullView' from the tool-bar.

· Cursors are not displayed :

· The boundaries and the data cursor are only shown if they are within thedisplayed range. Check the 'Start' and 'Stop' controls in the 'Calculations'panel for the boundaries cursor and the 'Wavelength' control in the 'Cursor'panel for the data cursor.

· Histogram does not show the expected values or does not show any values :

· The histogram does only show the values specified by 'Start' and 'Stop'wavelength in the 'Calculations' panel. These 'Start' and 'Stop' values arerepresented as boundary cursors in each diagram except the histograms. Ifthe boundary cursors enclose a part of the measurement range only thesevalues are used to draw the histogram. Refer to the Cursor Control sectionfor more details.

· After opening an exported *.csv file with Microsoft Excel, a large number ofincorrect numbers are displayed at the Excel sheet :

· The decimal separator in your Microsoft Excel may be set to ',' instead to '.'.The *.csv files generated by this program requires that Excel interprets '.' as

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the decimal separator.

· The system loss is too high :

· Check the fiber connectors and clean them if necessary.

5.2 ServiceIn normal operation the PMD5000 system does not need any service. For highestprecision of the measurement it is recommended to recalibrate the TXP cards ofthe PMD5000 every two years. You can see the due date of calibration in thecard info-menu of the card driver to determine the recalibration date.

Appendix

PMD5000

Part

VI

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6 Appendix

6.1 WarrantyThorlabs warrants material and production of the PMD5000 for a period of 24months starting with the date of shipment. During this warranty period Thorlabswill see to defaults by repair or by exchange if these are entitled to warranty.For warranty repairs or service the unit must be sent back to Thorlabs or to aplace determined by Thorlabs. The customer will carry the shipping costs toThorlabs, in case of warranty repairs Thorlabs will carry the shipping costs backto the customer.If no warranty repair is applicable the customer will be responsible for the costsfor return shipment.In case of shipment from outside the EU, any duties, taxes etc. which shouldarise have to be carried by the customer.

Thorlabs warrants the hardware and software determined by Thorlabs for this unitto operate fault-free provided that they are handled according to the requirementsof Thorlabs. However, Thorlabs does not warrant a faulty free and uninterruptedoperation of the unit, of the software or firmware for special applications nor thisinstruction manual to be error free. Thorlabs is not liable for consequentialdamages.

Restriction of warranty

The warranty mentioned above does not cover errors and defects being the resultof improper treatment, software or interface not supplied by Thorlabs,modification, misuse or operation outside the defined ambient conditions statedby Thorlabs or unauthorized maintenance.

Further claims will not be consented to and will not be acknowledged. Thorlabsdoes explicitly not warrant the usability or the economical use for certain cases ofapplication.

Thorlabs reserves the right to change this instruction manual or the technical dataof the described unit at any time.

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6.2 Technical DataAll technical data are valid at 23 ± 5°C and 45 ± 15% rel. humidity

General technical data

Operating Temperature: +5 ... +40 °C

Storage Temperature: -40 ... +70 °C

Space Requirement:MainframeECL5000DDPC5500IPM5300 (PMD5000FIN)PAX5720 (PMD5000HDR)

TXP5016 (3U)4 TXP slots2 TXP slots2 TXP slots2 TXP slots

Warm-up time for rated accuracy: 15 min

Optical Parameters

Wavelength Range: 1520 ... 1630nm

Dynamic Range1:FINHDR

45dB60dB

DGD Measurement Range2: 0.001 ... 400ps

DGD Repeatability3: <0.01ps

Typical Measurement Time:1 Data Point100 Data Points

£0.5s£50s

Measurement Method: Jones Matrix Eigenanalyzis

Fiber Connector:ECL5000DDPC5500IPM5300PAX5720IR3

FC/APCFC/APCFC/APC

FC/PC

1) At Pinput ³ 1mW2) The maximum measurable DGD is limited by the smallest possible wavelength

step. The given value is valid for a 10pm step size.3) For PMD <0.3ps

6.3 WEEEAs required by the WEEE (Waste Electrical and Electronic Equipment Directive)of the European Community and the corresponding national laws, Thorlabs offersall end users in the EC the possibility to return "end-of-life" units without incurringdisposal charges.

This offer is valid for Thorlabs electrical and electronic equipment

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· sold after August 13, 2005· marked correspondingly with the crossed out "wheelie bin" logo (see fig.

62)· sold to a company or institute within the EC· currently owned by a company or institute within the EC· still complete, not disassembled and not contaminated

As the WEEE Directive applies to self-contained operational electrical andelectronic products, this "end-of-life" take back service does not refer to otherThorlabs products, such as

· pure OEM products, that means assemblies to be built into a unit by theuser (e. g. OEM laser driver cards)

· components· mechanics and optics· left over parts of units disassembled by the user (PCBs, housings etc.)

If you wish to return a Thorlabs unit for waste recovery, please contact Thorlabsor your nearest dealer for further information.

6.3.1 Waste Treatment on your own Responsibility

If you do not return an "end-of-life" unit to Thorlabs, you must hand it to acompany specialized in waste recovery. Do not dispose of the unit in a litter bin orat a public waste disposal site.

6.3.2 Ecological Background

It is well known that WEEE pollutes the environment by releasing toxic productsduring decomposition. The aim of the European RoHS Directive is to reduce thecontent of toxic substances in electronic products in the future.The intent of the WEEE Directive is to enforce the recycling of WEEE. Acontrolled recycling of end-of-life products will thereby avoid negative impacts onthe environment.

Figure 62 Crossed out "Wheelie Bin" Symbol

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6.4 Listings6.4.1 List of Acronyms

The following acronyms and abbreviations are used in this manual:

AGND Analog GroundCSV Comma Separated ValuesDC Direct CurrentDFB Distributed Feedback (Laser)DGD Differential Group DelayDGND Digital GroundDPC Deterministic Polarization ControllerDOP Degree of PolarizationDUT Device under TestEC European CommunityECL External Cavity LaserEDFA Erbium Doped Fiber AmplifierER Extinction RatioFBG Fiber Bragg GratingGUI Graphical User InterfaceIL Insertion LossIPM Inline PolarimeterJME Jones Matrix EigenanalyzisLAN Local Area NetworkLED Light Emitting DiodeMMF Multi Mode FiberOEM Original Equipment ManufacturerPC Personal ComputerPCB Printed Circuit BoardPCD Polarization dependent Chromatic DispersionPDFA Praseodymium Doped Fiber AmplifierPDL Polarization Depending LossPMD Polarization Mode DispersionPM Polarization MaintainingPMF Polarization Maintaining FiberPSP Principal State of PolarizationSMF Single Mode FiberSOP State of PolarizationSOPMD Second Order PMDSPS Samples per SecondTLS Tunable Laser SourceTXP Thorlabs Extended PlatformUSB Universal Serial BusWEEE Waste Electrical and Electronic Equipment Directive

6.4.2 List of Figures

Figure 1 PMD5000 Graphical User InterfaceFigure 2 Connect to the SystemFigure 3 Standard JME Measurement WindowFigure 4 Measurement Scan finishedFigure 5 Saving / Export DataFigure 6 Setup Schematic Diagram

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Figure 7 Jones Matrix EigenanalyzisFigure 8 PMD5000FINFigure 9 PMD5000HDRFigure 10 PMD5000 Graphical User InterfaceFigure 11 System ConfigurationFigure 12 Main Configuration WindowFigure 13 ECL5000D Configuration WindowFigure 14 Agilent 8164A Configuration WindowFigure 15 Ando AQ4320D Configuration WindowFigure 16 External TLS with extra PC ConfigurationFigure 17 VISA OptionsFigure 18 VISA Server SecurityFigure 19 Start VISA ServerFigure 20 SOP Controller Configuration WindowFigure 21 Polarimeter Connection Setup TabFigure 22 PAX57xx Polarimeter Measurement Setup TabFigure 23 IPM5300 Polarimeter Measurement Setup TabFigure 24 Connection Status WindowFigure 25 Selection of the GraphFigure 26 Standard JME Measurement WindowFigure 27 Repeated Scan SetupFigure 28 Repeated Scan TriggerFigure 29 Repeated Scan ProgressFigure 30 Calculations WindowFigure 31 PDL DiagramFigure 32 IL DiagramFigure 33 Power DiagramFigure 34 DGD DiagramFigure 35 DGD HistogramFigure 36 Phase DiagramFigure 37 SODGD DiagramFigure 38 SODGD HistogramFigure 39 PSP DiagramFigure 40 PCD DiagramFigure 41 PSP Rotation Rate DiagramFigure 42 Calculations WindowFigure 43 Boundary CursorFigure 44 Calculations WindowFigure 45 Data CursorFigure 46 Cursor WindowFigure 47 Graph View SettingsFigure 48 Export File HeaderFigure 49 Export File General ValuesFigure 50 Export File Measurement ValuesFigure 51 Jones Matrix FormFigure 52 File MenuFigure 53 System MenuFigure 54 Measurement MenuFigure 55 View MenuFigure 56 Graph MenuFigure 57 Help Menu

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Figure 58 Tool-BarFigure 59 Graph SelectionFigure 60 Color SetupFigure 61 Display Options SetupFigure 62 Crossed out "Wheelie Bin" Symbol

6.4.3 Addresses

Europe: Thorlabs GmbH

Gauss-Strasse 11D-85757 KarlsfeldFed. Rep. of Germany

Tel.: +49 (0) 8131 / 5956 0Fax: +49 (0) 8131 / 5956 99Email: [email protected]: http://www.thorlabs.com

US, Canada & Mexico: Thorlabs, Inc.

435 Route 206 NorthNewton, NJ 07860USA

Tel.: (973) 579-7227Fax: (973) 300-3600Email: [email protected]: http://www.thorlabs.com

Japan: Thorlabs Japan, Inc.

5-17-1 OhtsukaBunkyo-ku Tokyo 112-0012Japan

Tel.: 81-3-5977-8401Fax: 81-3-5977-8402Email: [email protected]: http://www.thorlabs.com

Our company is also represented by several distributors and sales officesthroughout the world.Please call our hotline, send an Email to ask for your nearest distributor or justvisit our homepage http://www.thorlabs.com

Application Notes

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© <2006> Thorlabs

7 Application Notes

7.1 Definitions and TermsDGD The Differential Group Delay is the difference in group

delay at a specific wavelength between the slow and fastPSP. It is specified in ps.

PSP The Principal State of Polarization is defined by two inputSOP's whose output SOP's remain unchanged uponfrequency variation. These two PSP's show the slowest(PSP-) and fastest (PSP+) group velocity and they areorthogonal to each other.The term PSP is frequently confused withEigenpolarization.

PMD The Polarization Mode Dispersion is the mean or RMSvalue of the distribution of the DGD averaged over acertain wavelength range at a certain time or equivalently acertain time window at a specific wavelength or averagedover both. Hence, the PMD value is a more stable andcomparable parameter of a fiber than a single DGD value.

SODGD The second order DGD is defined as the frequencyderivative of the DGD vector (W). Two terms will beobtained which are often treated separately by breakingthe SODGD into parallel and perpendicular components.The term Dt denotes the DGD and q is the normalized fastPSP vector (PSP+).

The parallel part of the SODGD (Ww||) causes polarizationdependent chromatic dispersion (PCD) and theperpendicular part (Ww^) represents a frequencydependent rotation of the PSP (k).

SOPMD The second order PMD is the meanvalue of the distributionaveraged over the wavelength range. It is calculated

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according to the following formula:

The factor of 0.5 is due to theory. The PSP vector SPSP inthe above formula is the normalized unit vector pointinginto the direction of the fast principal state. N is the numberof wavelength points at which the Jones matrix ismeasured. Since the SOPMD involves the second orderderivative of the DGDs and the PSPs the average can onlybe taken over N-2 data points.Due to the SW feature, that every scan can be stopped atany intermediate wavelength point without loss of alreadyrecorded data, the theoretical scaling factor 1/(N-2) mustbe treated as running factor and is therefore approximatedby

.Since the accuracy of DGD and PSP values reduces withdecreasing step size, the weighting factor

decreases also the importance of less accurate DGDvalues within the average.

PCD Polarization dependent Chromatic Dispersion causespolarization dependent pulse compressing andbroadening.

Depolarization term k The depolarization term k is the rate of rotation of thePSPs.

Eigenpolarization Eigenpolarizations refer to the eigenvectors of the Jonesmatrix of an optical element, the states which areunchanged in polarization by the action of the elementsJones matrix.Homogeneous polarization elements possess orthogonaleigenpolarizations whereas inhomogeneous polarizationelements feature non-orthogonal eigenpolarization.Another class of polarization elements called degeneratepolarization elements have only one linearly independenteigenpolarization.

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7.2 AccuracyQuestion 1: What is the PMD bandwidth? or How strongly are two DGD

measurements at l1 and l2 correlated or statistically independent?Answer 1: For random mode coupling like in fibers two DGD measurements at

closely spaced wavelengths will still be correlated to some extent.Correlated here means that the knowledge of DGD(l1) still allows topredict with some reasonable probability what the value of DGD(l2)will be. There is a memory (correlation) effect. Only if thewavelength distance is large enough a reliable prediction will fail inany case and the two values are statistically independent. Thewavelength (frequency) distance over which a correlation exists iscalled the PMD/DGD bandwidth and is given by (the numericalvalue differs slightly for different references) (Shtaif, Mecozzi, Nagel,PTL 12,1, (Jan. 2000), p.53) DBn = 640 GHz / PMD [in ps]. This canbe converted into DBl = 5.1 nm / PMD [in ps] by DBn / DBl = n / l.Hence, for a random mode coupled device, if one wishes to pickrandomly distributed DGDs to get a fair Maxwell representation, thewavelength increment should be a bit larger than DBl. Otherwise,the counts in a bar of the histogram are not made on a true randomsample.Obviously, this has an impact on the PMD accuracy of randommode coupled devices (see below).

Question 2: What is the accuracy of the PMD5000 for a single DGDmeasurement?

Answer 2: There are different parameters which influence the accuracy of thedetermined DGD.

Wavelength StepThe step width is an important parameter which influences theaccuracy of the calculated DGD. The DGD is calculated from thephase. The phase given in degrees describes the difference of thefast and slow principal state. Due to the phase periodicity of p (180°)any phase difference between the fast and slow principal stateexceeding 180° can not be uniquely resolved, but will be mappedinto the basic interval 0° … 180°. Therefore, the DGD valuescorresponding to phase differences larger than p can not bedetected.The step width controls the phase. A small step width can be usedto measure high DGD values. See Table 3 in theMeasurement Configuration section. However, if a small stepsize isused to measure low DGD values the accuracy of the measurementsystem can distort the results significantly.

The following examples show the measurement of a PMF. TheDGD over the wavelength is constant.The first example displays the DGD and Phase measured with astep size of 0.5nm shown as reference and 1.0nm shown as current

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measurement data. The function 'Optimize Step Width' determinedthe step width of 0.5nm which has a minimum safety factor of 2.Therefore it is possible to increase the step width to 1.0nm. Thephase has a maximum of about 109° at the start wavelength. Thephase is doubled with a step width of factor 2. It is still possible toincrease the step width.

Figure DGD of a PMF measured with a step width of0.5nm and 1.0nm

Figure Correlating Phase of a PMF measured with a stepwidth of 0.5nm and 1.0nm

The next example shows the same PMF patchcord measured with astep width of 2.0nm displayed as current measurement data. Thephase is now higher than 180°. Because of the ambiguity the phaseis mapped to the range of 0 ... 180°. Hence, a lower DGD is

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measured than it is with a step width of 0.5nm as shown asreference data.A good indication for the correct step width is if you perform asecond scan with half the step width. If the phases match to eachother by factor 2 a correct step width was chosen and the resultsare correct.

Figure DGD of a PMF measured with a step width of0.5nm and 2.0nm


The last example shows the measurement with a step width of0.1nm. The phase is in the range of 10° and has a high noise. Thesingle DGD values are erroneous whereas the PMD is the same asfor the reference data with a step width of 0.5nm. It can be clearly

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seen that since the phase is quite low the inaccuracy of themeasurement system itself has a much bigger impact than it has forvalues with a higher phase.



You will find these measurement files in the directory 'C:\ProgramFiles\TXP Series\TXP PMD5000\OnlineHelp\Examples'. The filenames are 'PMF StepWidth 0.1nm.pmd', 'PMF StepWidth0.5nm.pmd', 'PMF StepWidth 1.0nm Scan 01.pmd' and 'PMFStepWidth 2.0nm.pmd'.

Wavelength Accuracy

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The accuracy for a single DGD value, measured only once isstrongly dependent on the difference between the nominal andactual wavelength increment of the tunable laser source (TLS).Since the PMD5000 system does not measure the wavelengthincrement it relies on the stepping accuracy of the TLS. A 10% erroron Dl resp. Dw leads to a 10% error in the DGD = Dj/Dw. Also, theerror on the phase shift Dj contributes to the DGD error.Obviously, for a given Dw with no error d(Dw)=0, the DGD errorDDGD will increase the smaller the phase shift Dj gets to a zerophase shift. For a patch-cord with virtually no DGD we continuouslymeasure a noise floor of 3-5fs with a step size of Dl = 10nm. Thiscorresponds to a phase shift Dj of 2° [Dw = 10nm/800pm*100GHz*2p = 1250GHz*2p = 7854e9 1/sec). DGD*Dw = 5fs *7854e9 1/sec = 4*1e-2 rad = 2° = Dj];2° does not seem an awful good phase measurement. But you haveto see through how many steps we get there: 3 outSOPs for 3inSOPs, needed for two wavelengths. Then we do have to get theinverse of Jones matrices, multiply by a Jones matrix and do theeigenvalues calculation. The difference of the phase of the twoeigenvalues finally gives Dj.The DGD accuracy would be approximately given byDDGD/DGD = 2°/Dj + d(Dw)/Dw = 2°/Dj + d(Dl)/Dl.Best in class tunable laser sources do currently have a d(Dl) of±10pm. For step sizes of 100pm the relative error from thewavelength increment error is therefore 20%. As long as the phaseshift is much larger than 20° the contribution from the phase shifterror is negligible compared to the wavelength error contribution.

The single DGD accuracy DDGD could be enhanced by repeatedlymeasuring the DGD at the same wavelength and with the sameincrement (and under the same environmental conditions) andaveraging the samples. The DGD variance would improve as1/ÖN (N-1). This is achieved by averaging of the primarymeasurement parameters azimuth and ellipticity. However, tunablelaser sources tend to reproduce the same wavelength incrementwith the same error. They are usually always offset to the same sideand do not scatter symmetrically around the nominal wavelengthincrement. This leads then to a biased DGD value. Averaging in thissense therefore helps only if the wavelength increment is measuredby an external wavemeter and reducing thereby considerably d(Dl).

Question 3: What is the accuracy of the PMD for a weakly mode coupled devicelike an isolator?

Answer 3: The DGD values from a series of measurements are more or lessnormal distributed with a narrow width since there is almost nowavelength dependence of the DGD. PMD as the average valuemust be regarded as a statistical parameter. Take e.g. a sample oflength measurements on a stick and calculate the average. Add afurther measurement result and take again the average. Bothaverages will slightly differ and therefore an average value behaves

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as a random parameter with an inaccuracy. The uncertainty isgenerally the width of the distribution function.Any large systematic wavelength increment offset appears as anerror and will immediately lead to a shift of the whole distributionfunction. High wavelength measurement accuracy is thereforemandatory for small PMD measurements on such a component.

Question 4: What is the accuracy of the PMD for a strongly mode coupleddevice like a fiber?

Answer 4: PMD as an average value must be regarded as a statisticalparameter. Take e.g. a sample of length measurements on a stickand calculate the average. Add a further measurement result andtake again the average. Both averages will slightly differ andtherefore an average value behaves as random parameter with aninaccuracy. The uncertainty of the average is generally thesquareroot of the variance of the sample divided by the squarerootof the number of samples and so correlated to the width of thedistribution function.However, another issue comes into play, namely: do we collectenough statistical uncorrelated data samples? Recall a) that wealways have a finite wavelength scan range (truncated since ourtunable laser has limits), and b) that the PMD bandwidth determinesa minimal wavelength increment to ensure low correlation. Theseaspects have been treated theoretically by Gisin, PTL, 8, 12, Dec.1996, p.1671 with the result that there is a physical limit given byDPMD/PMD = ± 0.9/Ö (PMD*[wstop-Dwstart]) with [wstop-Dwstart]the tuning range between the start and stop wavelength. Recall thatthe PMD bandwidth is given by DBn = 640 GHz / PMD [in ps] andthe accuracy is then limited by the number [wstop-Dwstart]/ DBn ofuncorrelated DGD samples within the tuning range. Hence, the scanrange truncation imposes a further constraint on the accuracy.This limit can not be exceeded even if the accuracy of an individualDGD measurement would be extremely high. It therefore does notmake sense to increase the single DGD measurement accuracy forrandom mode coupled devices.Numerical examples for the PMD accuracy are

PMD Scan Range DPMD/PMD

10ps 10nm ± 10%

1ps 10nm ± 32%

For a 10ps PMD value a 10nm tuning range gives a reasonablegood accuracy of ± 10% or 1ps for DPMD. However, the accuracyfor a PMD of 1ps measured within a 10nm range is only ± 32% andhence, quite large. One would have to extend to a 100nmwavelength window to achieve the 10% accuracy.Compared to that the error of the PMD5000 for measuring a singleDGD value (<10fs) is almost negligible if the tunable laser isbehaving well while stepping.A good check is of course how closely the distribution resembles a

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Maxwellian distribution.For a deterministic component the DGD distribution is normal andthe accuracy is given by the standard error of an average value withN the number of samples.

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7.3 Measurement of FibersThe results of a PMD measurement of fibers depends strongly on themeasurement configuration. The effect of PMD is shown in the following picture.

Figure PMD Effect

Standard single mode fibers (SMF), polarization maintaining fibers (PMF) andcombinations of them show different behaviors and therefore yield differentresults.

Single Mode FibersAn ideal standard single mode fiber would have no differential group delay. Therewould be no difference in the refractive index along the x- and y- axis whichcauses PMD / DGD. As usual in real life there is no ideal SMF. Stress by bendingor temperature fluctuations or asymmetrical fiber geometry generate birefringencewhich results in PMD.

The PMD is not constant over time. Seasonal temperature changes will causedifferent PMD over the year and temperature differences between day and nightproduce variances during 24 hours. Furthermore vibrations generated by trafficnear to an installed fiber or by wind to an overland installed fiber will causedynamic changes in PMD.

A single mode fiber can be synthesized by a large number of elementary cells.Such a cell can assumed as a short piece of fiber with a certain PSP. These cellsare randomly orientated to each other as shown in the next figure.

Figure SMF Model

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A sample of a 1km single mode fiber can be seen in the following diagrams.Today's fibers are optimized to reduce the PMD. The PMD of this fiber is verysmall only a few tens femtoseconds. A large step width is appropriate for this fibersince the PMD is very low. To obtain accurate data a large phase is necessarywhich can be achieved by a large step width. See the Accuracy section for moredetails regarding the relation between step width and accuracy. The shownreference data was scanned with a step width of 20nm whereas the currentmeasurement scan was taken with 5nm.

Figure DGD of a SMF

A typical behavior of a SMF is the relatively smooth change of the PSP as it canbe seen in the diagram below.

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Figure PSP of a SMF

You will find these measurement files in the directory 'C:\Program Files\TXPSeries\TXP PMD5000\OnlineHelp\Examples'. The file names are 'SMFStepWidth 5.0nm.pmd' and 'SMF StepWidth 20.0nm.pmd'.

Polarization Maintaining FibersA polarization maintaining fiber has a large difference of the refractive index in x-and y- direction. This can be done by an elliptical shape of the fiber core or bystress elements along the core as it is realized with PANDA and BowTie fibers.

A PMF preserves the linear polarization state of the input only if the polarizationstate at the input is linearly polarized and perfectly aligned with one of theprincipal PM axes (polarization eigenstates). If both principal axes are excitedwith some light, they propagate independently through the fiber, each keeping it'slinear polarization state when measured individually and always stayingorthogonal to each other. However, due to the birefringence of the PMF thephase shift between the two axes continuously changes. This phase shift yieldsdifferent polarization ellipses at each measurement location along the fiber. Theaccumulated phase shift at the fiber exit point depends on the wavelength of thelight source, the length of the PMF and the fiber birefringence. This phase shift isthe equivalent of the DGD in case of a single PMF.

A sample of a 2m polarization maintaining fiber patch-cord can be seen in thefollowing diagrams. The PMD of this fiber is about 2.336ps. A step width of 1nm isappropriate for this fiber. The reference and measurement data were taken withthe same scan parameter and at the same ambient conditions.

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Figure DGD of a PMF Patch-Cord

The DGD is almost constant over wavelength which is a typical behavior for aPMF patch-cord. Therefore, a PMF can be used as a DGD reference. If the DGDshows a large slope the step width is most likely to large! See the Accuracysection for more details.Also the Stokes parameter for a PMF patch-cord is nearly constant overwavelength as it can be seen in the diagram below.

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Figure PSP of a PMF Patch-Cord

You will find these measurement files in the directory 'C:\Program Files\TXPSeries\TXP PMD5000\OnlineHelp\Examples'. The file names are 'PMFStepWidth 1.0nm Scan 01.pmd' and 'PMF StepWidth 1.0nm Scan 02.pmd'.

Combination of Single Mode and Polarization Maintaining FibersIf SMFs and PMFs are connected to each other the DGD and PSPs arecompletely different to the smooth graphs shown above. Even if two PMF patch-cords are coupled to each other there will be a small misalignment of the mainaxes. The example of a combination of single mode and polarization maintainingfibers are displayed in the diagrams below.The DGD is varying over wavelength. This is due to the fact that at certainwavelengths the DGDs of the single PMFs neutralize each other whereas at otherwavelengths they will be added.Also the PSPs strongly vary over the wavelength.

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Figure DGD of a Combination of SMF and PMF Patch-Cords

Figure PSP of a Combination of SMF and PMF Patch-Cords

You will find these measurement files in the directory 'C:\Program Files\TXPSeries\TXP PMD5000\OnlineHelp\Examples'. The file names are 'SMF and PMFStepWidth 0.5nm Scan 01.pmd' and 'SMF and PMF StepWidth 0.5nm Scan02.pmd'.

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7.4 Measurement of Narrow Bandwidth ComponentsThe difficulty of DGD (differential group delay) measurement for narrow bandcomponents like filters arises from the conflict of measuring small DGD valueswith small wavelength resolutions (step width) due to the band structure of thefiltering device. Recall that the DGD is defined as:

.

The phase change Dj comes from the birefringence / PMD of the device and Dwis associated with the wavelength increment Dl ( =Dw l/w).Obviously for a given DGD the phase change Dj decreases with decreasing Dw.It approaches the intrinsic phase noise Djn of the instrument

and the minimal resolvable DGD is thus limited by the combination of severalfactors. On the other hand if Dw is too large a fine structure of the DGD within Dwis not resolved, but averaged out. This could mean a loss of information,especially the information about a maximal DGD within a wavelength window.Therefore, the challenge is to find the optimal step size Dw which is large enoughto avoid instrumental noise and small enough to yield the most information.Obviously, this challenge depends on the details of the DUT and can hardly beintegrated into a generic tool for any component with satisfactory performance.One could of course use the smallest allowed step size Dwscan = Dwmin (determinedby the used tunable laser source; ~1 pm or 0.12 GHz) and determine the Jonesmatrix at each wavelength point. But the existing PMD analysing routines do referto Jones matrices from adjacent wavelength points (Dwscan) for the determinationof DGD and usually run into the issue with large statistical DGD fluctuations frominstrumental noise.

In general, there are further issues involved in characterizing band structuredcomponents.1. It does not make sense to use a frequency resolution Dw larger than the true

bandwidth DB of the device (defined by a certain insertion loss drop from theminimum insertion loss). The strong insertion loss variation outside the passband reflects strong internal interference effects with associated phasevariations which would just be washed out.

2. Since Jones Matrix analysis involves polarimetric measurements thefrequency resolution Dw must be small enough that polarization states are stilluniquely defined. Recall that an output polarization on the Poincaré spherestarts rotating on a cone around the so called principal state of polarization ifthe step size Dl is increased from 0. At a certain value Dwmax ( = Dlmax*w/l) thepolarization state comes back to its original value. This could then beinterpreted as a zero phase change with DGD = 0 or a p phase shift with aDGD = p/Dwmax and is therefore ambiguous (see Table 1).

3. Some devices like interleavers do exhibit multiple pass and stop bands andeach of them requires a PMD/DGD characterization.

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4. Stepping an ECL tunable laser with small frequency resolution (~5 – 25 pm)may lead to systematic errors in the step size dDl (dDw) and hence tocontributions to the overall DGD error: DDGD/DGD = (dDj + Djn)/Dj + dDw/Dw if Dw is taken from the nominal step size for scanning.

Dlmax resp. Dnmax max meas. DGDp

nm GHz ps

0.01 1.2 400

0.02 2.5 200

0.04 5.0 100

0.10 12.5 40

0.20 25.0 20

0.40 50.0 10

0.80 100.0 5

1.00 125.0 4

Table At 1550 nm a 1 nm/125 GHz wavelength frequencyresolution leads to unambiguously measurable DGDvalues if they are smaller than 4 ps:Dlmax * DGDp = 1 nm * 4 ps.

The following diagrams show examples of a DGD measurement of narrowbandwidth devices. A Fiber Bragg Grating (FBG) was measured in reflection. Acirculator was used to extract the reflection at a certain narrow wavelength range.The first measurement was done with a step width of 0.1nm. As it can be seen inthe diagram as reference curve (light blue) there are only 20 measurement pointsfor IL (19 DGD values / 18 SODGD values) over the scanned wavelength rangefrom 1554.5nm to 1556.5nm. The interesting area ranges from about 1555.2nmto 1555.5nm which is marked by the green cursors. It gives only a rough ideaabout the measurement data over wavelength. The second scan was done with0.05nm step width which provides 40 measurement points. It is drawn as redcurve and gives a better overview about this FBG.

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For a more detailed diagram the step width can be decreased to 0.01nm. Thisresults in a very fine resolution for the IL. You can observe several ancillarymaxima and an unsymmetry of the FBG. However, the PMD measured at thisstep width is higher than measured with a step width of 0.1nm shown as thereference. This is only for this special case but cannot be applied in general. Infact the DGD values vary strongly around the mean value. This is due to a smallphase change and its dependence on the polarization accuracy. As smaller thephase change is as higher is the influence of polarization measurement error.Therefore it is recommended to use a large wavelength step width which is stillsmall enough to obtain a reasonable amount of DGD data within the bandwidth.

Figure IL of a FBG in Reflection

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Figure DGD of a FBG in Reflection

You will find these measurement files in the directory 'C:\Program Files\TXPSeries\TXP PMD5000\OnlineHelp\Examples'. The file names are 'FBG StepWidth0.01nm.pmd', 'FBG StepWidth 0.05nm.pmd' and 'FBG StepWidth 0.1nm.pmd'.

Index

- 2 -2nd Order DGD Diagram 49

2nd Order DGD Histogram 50

- 8 -8164A 22

- A -Accessories 6

Accuracy 83

Activate Interlace Timer 37

Addresses 79

Agilent 22

Analyzis 53

Ando 22

AQ4320D 22

Autoscale 68

Average Type 27, 29

- B -Basic Sample rate 29

Boundary Cursor 55

- C -Calculation Boundaries 53

Calculations Window 41, 53

Coefficient 41, 53

Color Setup 68

Comment 37

Configuration 21, 34

Connection 32

CSV Export Setup 37

CSV File 37, 58

Current Mode 27, 29

Cursor 53, 55

- D -Data Cursor 55

Data Export 12, 58

dBm 68

Depolarization Term k 81

DGD 14, 81

DGD Diagram 46

DGD Histogram 47

Diagrams 43

Differential Group Delay 46

Display Configuration 67

Display Functions 66

Display Options 68

DOP Mode 27, 29

DPC5500 27

- E -ECL5000D 22

Ecological Background 76

Eigenpolarization 81

Error Handling 71

Exchanging TXP Cards 18

Export Data 12, 58

- F -Fiber Length 41, 53

File Format 37

File Menu 63

Frequency 68

- G -Getting Started 10

GPIB 25

Graph 43

Graph Menu 63

Graphical User Interface 21

GUI 21

- H -Hardware Description 17

Help Guide 10

Help Menu 63

Histogram Columns 68

Hostname 22, 27, 29

- I -IL Diagram 44

Insertion Loss 44

Index 101

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Installing TXP Cards 18

Interlace Timer 37

Interlaced Measurement Scans 37

IP 22, 27, 29

IPM5300 29

- J -JME 14

Jones Matrix Eigenanalyzis 14

Jones Matrix Method 14

- L -Laser Configuration 22

Laser Settings 34

List of Acronyms 77

List of Figures 77

- M -Make Reference 67

Maximum Measureable DGD 34

Measurement 33

Measurement & Automation 25

Measurement Configuration 34

Measurement Data 67

Measurement Menu 63

Measurement Results 41

Measurement Setup 13

Menu Bar 63

Minimum Measurement Time 37

Move Cursor Mode 55

- N -Narrow Bandwidth Components 96

Narrow Bandwidth Devices 53

National Instruments 25

National Instruments VISA 20

navigation 62

NI 25

NI MAX 25

NI-VISA 25

Number of Basic Periods 29

- O -Operating Instructions 20

Optimize Step Width 34

- P -Part List 6

Patchcords 20

PAX5720IR3 29

PCD 81

PCD Diagram 52

PDL 14

PDL Axis 14

PDL Diagram 43

Phase Diagram 48

PMD 14, 81

PMD Bandwidth 83

PMD Coefficient 41, 53

PMD File 37, 58

PMD5000FIN 17

PMD5000HDR 17

PMF 90

Polarimeter 29

Polarization Analyzer 13

Polarization Dependent Chromatic Dispersion 52

Polarization Dependent Loss 43

Polarization Maintaining Fiber 90

Port 22, 27, 29

Power 45

Power Unit 68

Preconditions 20

Principal State of Polarization 51

PSP 81

PSP Diagram 51

PSP Rotation Rate 81

PSP Rotation Rate Diagram 53

- Q -Quick Start-up 10

- R -Reference 53

Reference Data 67

Removing TXP Cards 18

Repeated Measurement 37

Repeated Scans 37

Repetitions 37

Result Averaging 29

Results 41

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- S -Safety 5

Save Data 12, 58

Scan 37

Scan Start Wavelength 34

Scan Stop Wavelength 34

Scan Trigger Timer 37

Second Order DGD 14

Separator 37

Service 72

Signal Averaging 29

Single Mode Fiber 90

Slot 22, 29

Slot Timeout 27

SMF 90

SODGD 81

SODGD Diagram 49

SODGD Histogram 50

SOP Controller 27

SOP Generator 13

SOPMD 81

Speed Index 27, 29

Start Index 37

Start Measurement 37

Start Scan 37

Start Time Raster 37

Step Optimizer 34

Stringly Mode Coupled Device 83

System Loss 68

System Menu 63

- T -Target Directory 37

Target File Prefix 37

Technical Data 75

Theory of Operation 14

Thorlabs ECL5000D 22

Timeout 22, 29

Timer 37

TLS 22

Tool Bar 65

Troubleshooting 71

Tunable Laser Source 13, 22

TXP Card Configuration 21

Types of optical connectors 20

- U -User Application 21

- V -View Area 55

View menu 63

VISA 25

VISA Remote Client 25

VISA Remote Server 25

- W -Warranty 74

Waste Treatment 76

Watt 68

Wave Unit 68

Wavelength 68

Wavelength Step Width 34

Wavenumber 68

Weakly Mode Coupled Device 83

WEEE 75

- Z -Zoom Mode 55

Index 103

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Polarization Mode Dispersion Measurement System PMD5000 ... · 2006 Operation Manual Thorlabs...

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