2107 and 2117 User Manual Reva

7/25/2019 2107 and 2117 User Manual Reva

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U S E R S G U I D E

10-MHz AdjustableBalanced PhotoreceiversModels 2107 & 2117

2584 Junction Avenue San Jose, CA 95134-1902 USA

phone: (408) 9191500 e-mail: [email protected] www.newfocus.com


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WarrantyNew Focus, Inc. guarantees its products to be free of defects for one year fromthe date of shipment. This is in lieu of all other guarantees, expressed or implied,and does not cover incidental or consequential loss.

Information in this document is subject to change without notice.Copyright 2004, New Focus, Inc., a division of Bookham Technology plc. All

rights reserved.

The logo and NEW FOCUS, Inc. are trademarks or registeredtrademarks of Bookham Technology plc in the U.S.A or other countries.Products described in this document may be covered by one or more patents inthe U.S.A. and abroad.

Document Number 200331 Rev. A


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Models 2107 & 2117 Contents 3

Contents

Operation 5Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Using the Photoreceiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Checking the Battery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

General Features & Principles 9Photoreceiver Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Optical Power and Output Voltage . . . . . . . . . . . . . . . . . . . . . 10

Frequency Response and Noise 13

Measuring Bandwidth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Measuring Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Performance Data for Frequency Response. . . . . . . . . . . . . . 16Performance Data for Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Common Mode Rejection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Characteristics 21

Physical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Model 2107 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Model 2117 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Customer Service 24Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24


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4 Contents NEW FOCUS, Inc.


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Models 2107 & 2117 Operation 5

Operation

Introduction

The Model 21X7 is a general-purpose balancedphotoreceiver with adjustable gain and bandwidth.These receivers can be powered by batteries or by anexternal 15-V power supply. There are two modelsavailable, each based on a different photodetector.Free-space (FS) and fiber-coupled (FC) versions areavailable for each model:

Complete specifications begin onpage 21.

The 10-MHz three-stage transimpedance amplifierincludes selectable gain and selectable low- and high-pass filters for easy signal optimization.

Model Wavelength DiodeType

Active Area

2107-FC 3001070 nm silicon 0.8 mm2

2107-FS 3001070 nm silicon 0.8 mm2

2117-FC 9001700 nm InGaAs 0.0078 mm2

2117-FS 9001700 nm InGaAs 0.08 mm2

Note:Note:


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6 Operation NEW FOCUS, Inc.

Figure 1:

Typical

responsivities

of the Model

2107 & 2117photodiodes

To obtain the value of the response factor in V/mW, divide thephotodiode responsivity by 1.5. For more information onfrequency response and noise, seepage 13.

800

0.0

0.2

0.4

0.6

0.8

1.0

Wavelength (nm)

400

Responsivity

(A/W)

1200 1600

2107

2117

Note:Note:


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Models 2107 & 2117 Operation 7

Using the Photoreceiver

1. Mount the photoreceiver.Use the 8-32 thread(M4 for metric versions) on the bottom of the cas-

ing to mount the photoreceiver to a post or pedes-tal.

2. Supply power.Power the Model 21X7 usingeither two 9-volt alkaline batteries or a15-V low-noise linear power supply (such as the New FocusModel 0901).

3. Connect the receiver output.Connect your

voltmeter, oscilloscope, or other instrument to theOutputSMA connector on the receiver.

If you wish to connect to a BNC cable, you can purchase aBNC-to-SMA adapter such as the New Focus Model1225.

4. Turn on the photoreceiver power.For external

power, use15 VDC ON; for battery, use Batt ModeON.

5. Align optical beams onto the detectors.The photodiodes are not very large, so take carewhen aligning each beam.

6. Adjust the gain.Use the knob and rocker switchon the receiver to set the gain. The bandwidths

vary with the gain setting (see table on page 10).

7. Adjust the filters. Select low-pass and high-passcorner frequencies using the knobs on the receiver.

8. Balance the optical input levels.Alternatelyblock each diode and observe the signal strength.When they are approximately equal and opposite,

adjust their relative intensity until the balancedoutput is zero volts.

9. Turn off the photoreceiver power. When youare finished with the receiver, place the powerswitch in the 15 VDC ONposition and switch offor unplug the external power supply.

Note:Note:


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8 Operation NEW FOCUS, Inc.

Checking the Batteries

The Model 21X7 can be powered by two standard 9-volt alkaline batteries. Under normal operating

conditions with low light levels and a high impedanceload attached to the BNC connector, the photoreceiverdraws about 20 mA from the batteries, and the batterylifetime is approximately 24 hours.

To check the condition of the battery:

1. Turn on the photoreceiver using the power switch.

2. Set the Low Frequencyadjustment to DC.3. Set the Gainto 3x104.

4. Focus at least 1 W of optical power on thedetector (or place the detector in front of a desklamp).

The output should be greater than 7 V. If it is not,

replace the batteries with fresh ones.

Replacing the Batteries

The Model 21X7 is shipped with two fresh 9-Vbatteries installed. To avoid confusion due to lowbatteries, replace the batteries on a monthly basiswhen the receiver is in frequent use, or use an external

linear power supply such as the New FocusModel 0901.

1. Turn off the receiver using the power switch.

2. Use a Phillips-head screwdriver to remove thetwo screws on the back panel of the photo-receiver.

3. Remove the back panel.4. Replace the used 9-V batteries with fresh ones.

5. Replace the back panel and the two screws.

6. Recheck the battery level as described above.


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Models 2107 & 2117 General Features & Principles 9

General Features & Principles

Photoreceiver Circuitry

The circuitry inside the Model 21X7 consists of twophotodiodes followed by a three-stage transimpedanceamplifier. The gain can be adjusted from 626 V/A to18.8x106V/A in 5-dB steps. The low-noise amplifierdesign is optimized to maximize bandwidth at eachgain setting. At the higher gain settings, the bandwidthis limited by amplifier gain-bandwidth product. Theplots of Figure 3 show the typical frequency responsesfor the different gain settings.

Figure 2:Functional

schematic of

the Model 21X7

circuitry

+15 V

-15 V

GND

BATT

9 V

INDEPENDENTLY

ADJUSTABLE 6-dB/OCTAVE

HIGH- AND LOW-PASS FILTERS

+9 V

DETECTOR

HOUSING IS

GROUNDED

SMA

-9 V

ADJUSTABLE-GAIN

STAGE

x3

x1

ADJUSTABLE-GAIN

STAGE

x104

x103

x102

x10

x1

f_L f_H

BATT

9 V

+9 V REG

-9 V REG

+9 V

-9 V


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10 General Features & Principles NEW FOCUS, Inc.

The following table summarizes the bandwidth at eachgain setting. The bandwidth on the 3x settings issomewhat lower than the 1x settings, and significantlydecreases at the highest gain settings. There is little

difference in frequency response between the visible(Model 2107) and IR (Model 2117) models. The plots ofFigure 3show the frequency-response details for eachgain setting.

Optical Power and Output Voltage

The typical operating range for these receivers is froma few nanowatts up to 2 to 5 mW (depending on themodel and gain setting). Be careful to keep thedifferential optical power below the maximum opticalpower difference of 10 mW to avoid damaging thephotoreceiver.

To compute the approximate output voltage for a giveninput optical power use the relationship

Vout= (P+-P-)RG,

Gain

SettingSpecification Typical Performance

1x1 10 MHz 12 MHz

3x1 NA 6 MHz

1x10 NA 12 MHz

3x10 NA 6 MHz

1x102 NA 8 MHz

3x102 NA 6 MHz

1x103 NA 700 kHz

3x103 NA 700 kHz

1x104 NA 250 kHz

3x104 150 kHz 250 kHz


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Models 2107 & 2117 General Features & Principles 11

where P+and P-are the input optical powers in Wattson the right and left photodiodes respectively, Ris thephotodetectors response factor in V/mW, and Gis theamplifiers gain setting.

Estimate the value of the response factor by dividing theresponsivity shown in Figure 1by 1.5.

For example, the Model 2107 on the 1x103gain settingand with 10 W of optical power at 900 nm on onephotodiode will have an output voltage ofapproximately

(0.01 mW)(0.35 V/mW)(1x103

) = 3.5 V.The maximum differential optical power that can bedetected by the photoreceiver is determined by theinput optical power at which either stage of thetransimpedance gain saturates. We can calculate thesaturation power at 900 nm for the Model 2107 at itsmaximum output voltage of 7 V with fresh batteries

or operating from an external 15 VDC power supply.

Using the expression 7 V =PsatRG, the Model 2107 hasa differential saturation power of 20 mW for the lowestgain setting up to 0.7 W for the highest gain setting.At other wavelengths where the responsivity is lower,the saturation power increases inversely with responsefactor.

Note:Note:


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12 General Features & Principles NEW FOCUS, Inc.


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Models 2107 & 2117 Frequency Response and Noise 13

Frequency Response and Noise

Measuring Bandwidth

The frequency response and noise characteristics ofthe photoreceiver depend on the selected gain. Thefigures beginning on page 16give the typicalfrequency response and noise behavior for thephotoreceivers at each of the gain settings. Thefrequency response of the transimpedance gain isplotted using the expression

20log[Gain()/Gain(0)],whereis the frequency and Gain(0) is the gain at DC.The photoreceivers bandwidth is defined as thefrequency where the gain has decreased by 3 dB, or afactor of .

Measuring NoiseThe photoreceiver noise is characterized using thenoise equivalent power (NEP), which is a measure ofthe weakest optical signal that the photoreceiver candetect. The NEP is the optical power which willproduce a signal-to-noise ratio of 1 in a 1-Hzbandwidth. The minimum detectable optical power

can be found using the relationship

Minimum Optical Power = NEP ,

where BWis the bandwidth. Note that NEP is awavelength-dependent quantity that changes with thephotodetectors responsivity.

2

BW


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14 Frequency Response and Noise NEW FOCUS, Inc.

Another way to characterize the noise is with thephotocurrent noise (In), which is related to NEP by

In= R NEP,

whereR

is the photodetectors responsivity (in A/W).The photocurrent noise is independent of wavelengthbecause it gives the noise of the photoreceiver with thephotodetectors responsivity factored out.

To characterize the noise of the photoreceiver, theoutput electrical noise spectrum is measured with aspectrum analyzer. This voltage noise spectrum is

converted to an equivalent optical photocurrent noiseby dividing the voltage noise by the transimpedancegain (V/A). The photocurrent noise, In(), has units ofpA/ and is plotted in Figure 3and Figure 4usingthe expression 20log[In()/1 A].

Calculating NEP

The noise equivalent power (NEP) can be calculated bydividing the photocurrent noise by R, the detectorsresponsivity (see page 6).

From DC to 150 kHz the average photocurrent noisefor the Model 2107 on the high gain setting is about0.4 pA/ , corresponding to an average NEP at900 nm of 0.8 pW/ . The integrated noise

equivalent power from DC to 150 kHz is then obtainedby multiplying the average NEP by , the squareroot of the bandwidth.

The expression BW= 23-dB/4for a one-pole low-pass filter is useful for calculating the equivalent noisebandwidth. Using the high-pass filter set 1 decadebelow the low-pass cutoff reduces noise-equivalentbandwidth by approximately 10 %. For the Model 2107with a 3-dB bandwidth of 150 kHz, the equivalentnoise bandwidth is 235 kHz. This gives an optical noiseequivalent power of about 390 pW, so the minimumdetectable optical signal at 900 nm (with a signal-to-noise ratio of 1) for the Model 2107 on the highest gain

Hz

Hz

Hz

BW


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setting is 390 pW when operating at full detectorbandwidth.

You can further improve your signal-to-noise ratio byusing optical modulators or choppers with lock-in

amplifiers to limit the detection bandwidth. Usingsuch techniques you can reduce equivalent bandwidthto 1 Hz or less.

Calculating Output-Voltage Noise

The output-voltage noise can be calculated from

G R NEP ,where Gis the gain (V/V), Ris the photodiode responsefactor (V/mW), NEPis the average noise equivalentpower, and BWis the bandwidth. This gives an outputnoise voltage for the Model 2107 on the high gainsetting of

(3x104 V/V) (0.35 V/mW) (0.8x10-9 mW/ )

=4 mVrms.

The Johnson noise at the input of a 100-MHz bandwidthoscilloscope with 1-Minput impedance is 1.6 mVrms. This isoften the limiting factor in broadband measurements.

Summary

With the Model 2107 on the highest gain setting theminimum NEP is 0.8 pW/ , and this yields anoutput noise voltage of 4 mVrms. Viewed another way,for operation at the peak responsivity wavelength of900 nm and for the high gain setting, you will achieve a

signal-to-noise ratio of unity if the input power is390 pW.

For the Model 2117 with an InGaAs photodiode, theNEP at peak response wavelength of 1500 nm is0.4 pW/ over the 150-kHz bandwidth. The full

BW

Hz

2

4------ 150 10

3Hz

Hz

Hz


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bandwidth signal-to-noise ratio of 1 is achievedaround 200 pW.

Note that this assumes operation without any post-photoreceiver filtering and with the full photoreceiver

bandwidth. By using the built-in electronic band-passfilter or an optical chopper and a lock-in amplifier, thereceiver can detect significantly weaker optical signals.

Performance Data for Frequency Response

The 3-dB frequency bandwidth is defined as the

frequency where the photoreceivers transimpedancegain has decreased by a factor of . The typicalfrequency responses for the Model 2107 and Model2117 are shown in the following figures.

Figure 3:Typical

frequencyresponse for

Model 21X7 at

each gain

setting

2

Gain Setting=1

-15

-12

-9

-6

-3

0

3

0.01 0.1 1 10 100

Frequency (MHz)

NormalizedGain(dB)

x1

x3

Gain Setting=10

-12

-9

-6

-3

0

3

0.01 0.1 1 10 100

Frequency (MHz)

Normalized

Gain(dB)

x1

x3


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Gain Setting=102

-15

-12

-9

-6

-3

0

3

0.01 0.1 1 10 100

Frequency (MHz)

NormalizedGain(dB)

x1

x3

Gain Setting=103

-6

-3

0

3

0.01 0.1 1

Frequency (MHz)

No

rmalizedGain(dB)

x1

x3

Gain Setting=104

-6

-3

0

3

0.01 0.1 1

Frequency (MHz)

NormalizedGain(dB)

x1

x3


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Performance Data for Noise

Figure 4 shows the typical noise spectrum expressed asphotocurrent noise for Model 21X7 photoreceivers on

the highest gain setting.To derive the receivers Noise Equivalent Power (NEP),divide the photocurrent noise by the photodioderesponsivity. To convert to output voltage noise (RMS),multiply the photocurrent noise by the gain settingfrom the 21X7 front label, then by 630 V/A (the scalingfactor between the gain setting labels and the actual

amplifier transimpedance gain).

For example, the output voltage noise (RMS) for Model2117 in the 3x103setting is approximately:

0.4 pA/ x 3 x 103x 630 V/A = 0.75 Vrms/ .

For the 700 kHz of amplifier bandwidth in the 3x103gain setting, the equivalent noise bandwidth is:

( 2 x /4 ) x 700 x 103Hz = 1.1 MHz,

so the predicted output noise voltage is approximately

0.75 Vrms/ x = 0.8 mVrms.

Because the NEP is listed at the highest gain setting,some additional considerations add to the NEP at lower

gain settings. First, the noise spectrum (Figure 4) is notflat, rising at frequencies above 100 kHz. Thiscontributes an extra 20% to the output noise voltage inthe 3 x 103setting compared to 3 x 104. Also, as theoutput noise voltage approaches 1 mVrms, the Johnsonnoise limit of your measurement instrument willbecome important. Note that the Johnson noise for anoscilloscope with 100-MHz bandwidth (assumingperfect roll off) and 1-Minput impedance is1.2 mVrms.

Hz Hz

Hz 1.1 106

Hz


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Figure 5:

Typical CMRR

for

Model 2107 in

each gainsetting

Figure 6:

Typical CMRRfor

Model 2117 in

each gainsetting

20

25

30

35

40

45

50

0.01 0.1 1 10 100

Frequency (MHz)

CMRR(dB)

1x103- 3x103

1 - 3x102

1x104- 3x104

20

25

30

35

40

45

50

0.01 0.1 10 100

Frequency (MHz)

CM

RR(dB)

1x103- 3x103

1 - 3x102

1x104- 3x104

1


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Models 2107 & 2117 Characteristics 21

Characteristics

Physical Specifications

Figure 7:Mechanical

drawing of the

Model 21X7

casing photo-detectors

2.50"(63.5)

5.17"(131.2)

1.24"(31.5)

2.31" (58.6)

8-32 (M4)THD

1.78"(45.2) 0.66"

(16.7)

1.00"(25.4)

powerswitch

low freq.corneradjustknob

high freq.corneradjustknob

gainmultiplierswitch

SMAoutputconnector

external

powerinput(15VDC)

gainknob


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22 Characteristics NEW FOCUS, Inc.

Model 2107 Specifications

Model 2107

Wavelength Range 3001070 nm

3-dB Bandwidth 10 MHz, 5 MHz, 150 kHz

Typical Common-Mode Rejection 25 dB

Rise Time 80 ns

Peak Conversion Gain 9.4 x 106V/W

Typical Max. Responsivity 0.5 A/W

Max. Transimpedance Gain 18.8 x 106V/A

Output Impedance 16

Minimum NEP 0.8 pW/

CW Saturation Power 20 mW @ 850 nm

Max. Differential Power 20 mW @ 850 nm

Max. Power per Photodiode if

balanced (damage threshold)

20 mW @ 850 nm

Detector Material/Type Si/PIN

Detector Active Area 1.0 mm x 0.8 mm

Optical Input FC or Free Space

Electrical Output SMA

Power Requirements 15 VDC


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Models 2107 & 2117 Characteristics 23

Model 2117 Specifications

Model 2117

Wavelength Range 9001700 nm

3-dB Bandwidth 10 MHz, 5 MHz, 150 kHz

Typical Common-Mode Rejection 25 dB

Rise Time 80 ns

Peak Conversion Gain 18.8 x 106V/W

Typical Max. Responsivity 1 A/W

Max. Transimpedance Gain 18.8 x 106V/A

Output Impedance 16

Minimum NEP 0.4 pW/

CW Saturation Power 10 mW @ 1600 nm

Max. Differential Power 10 mW @ 1600 nm

Max. Power per Photodiode

(damage threshold)

10 mW @ 1600 nm

Detector Material/Type InGaAs/PIN

Detector Active Area 0.3-mm diam. (FS)

0.1-mm diam. (FC)

Optical Input FC or Free SpaceElectrical Output SMA

Power Requirements 15 VDC


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Customer Service

Technical Support

Information and advice about the operation of anyNew Focus product is available from our applicationsengineers. For quickest response, ask for TechnicalSupport and know the model and serial numbers foryour product.

Hours:8:005:00 PST, Monday through Friday(excluding holidays).

Toll Free:1-866-NUFOCUS (1-866-683-6287)(from the USA & Canada only)

Phone:(408) 919-1500

Support is also available by fax and email:

Fax:(408) 980-8883Email:[email protected]

We typically respond to faxes and email within onebusiness day.

Service

In the event that your photoreceiver malfunctions orbecomes damaged, please contact New Focus for areturn authorization number and instructions onshipping the unit back for evaluation and repair.

2107 and 2117 User Manual Reva

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