Final Report1394b:Optoelectronic Data

Communications

Group G9:

Tiffany Lovett, gte291r

Tornya Moore, gte668r

Mareisha Winters, gte824t

ECE 4006C

April 23, 2002

Key features of 1394?

• It is a hardware and software standard for transporting data at 100, 200, or 400 Mbps

• It is a digital interface - no need to convert digital data into analog

• It is physically small and can replace larger, more expensive interfaces

• It is easy to use

Key features of 1394?

• It is hot pluggable - users can add or remove 1394 devices while the bus is active

• It is inexpensive• It is a scaleable architecture - can mix 100,

200, and 400 Mbps devices on a bus• It has a flexible topology• It is non-proprietary - there is no licensing

problem to use for products.

1394 Cable

• Is a small, thin serial cable

• Contains six wires: two of the wires carry power; the remaining four wires are grouped into two twisted signal pairs

How 1394 Works

• Supports both asynchronous and isochronous data transfers

• 1394 device requests control of the physical layer

• Asynchronous: The address if the sender & receiver is transmitted by the packet data. Once the receiver accepts the packet, an acknowledgement is returned to the original sender

• Isochronous: The sender requests an isochronous channel with a specific bandwidth. Isochronous channel IDs are transmitted followed by the packet data. The receiver monitors the incoming data’s channel ID

Why 1394b?

• 1394b is a revision of the initial 1394 standard

• 1394b is twice the speed, and allows for longer distances

• It provides new connection options such as Plastic Optical Fiber, Glass Optical Fiber and UTP-S. Previously 1394 could only be connected via copper cabling

• 1394b is a prime choice for connecting personal computers with digital devices (i.e. cameras, DVD players, and camcorders)

Photodetectors

• Optoelectronic device that senses and measures the output of a typical light source

• There are three steps in the photodetection process:

(1) absorption of optical energy and generation of carriers

(2) transportation of the photogenerated carriers across the

absorption region

(3) carrier collection and generation of a photocurrent• The three main types are photoconductors, PIN photodiode, and

Avalanche photodiodes

• For high-speed applications the PIN photodiode is the best choice because it has no internal gain and can attain very large bandwidths.

Design Considerations for the Photodetector

• Two candidates:– Lasermate RSC-M85A306– Hamamatsu S5973

• Responsivity-measures how much light input is required to produce a given current

• Capacitance of the photodiode must not exceed the maximum input capacitance of the MAXIM board.

• Rise/Fall Time

Comparison of Two Photodiode Candidates

Lasermate RSC-M85A306 

Hamamatsu S5973

Design of the Photodetector Board

• Both unconnectorized and connectorized photodectector were used in the circuit.

• The resistance for the unconnectorized is 53.1 and for the connectorized it is 66.4

• According the data on Murata’s website, the ideal value for both of the capacitors is .01F.

Design of the Photodetector Board (cont’d)

• Once all of the components were gathered they were mounted on the board and soldered onto the board.

Connectorized Unconnectorized

Testing

• Tested the connectorized photodetector board by connecting it to the GTS 1250 and then to the Agilent board.

• The board did not produce an eye diagram.

• To analyze why no eye diagram was produced, simple average value singles were looked at along with Fourier analysis and incoming data stream.

• Received a signal from the connectorized photodetector but did not get a signal from the unconnectorized photodetector.

Testing (cont’d)

• Simple square wave test with connectorized photodetector

Testing (cont’d)

• Spectrum analysis with photodetector not connected

Emitters

• Three types are LEDs, Edge emitting lasers, and VSCELs

• LEDs produce light by a process known as spontaneous emission, resulting in incoherent light

• Lasers produce light by stimulated emission, which results in coherent light

• For high-speed applications VCSELs are superior to LEDs and Edge emitting lasers because they achieve high data rates easier and they are less expensive

Design Considerations for the VCSEL

• Two candidates:– Honeywell HFE4380-521

– Honeywell HFE4384-522

• Threshold current-minimum amount of current needed for the VCSEL to emit light

• Slope Efficiency-tells how many amps it takes to produce a given power output

• Rise/Fall Times

Comparison of Two VCSEL Candidates

HFE4380-521

HFE4384-522

Link Budget Analysis

• Will the system work for the proposed link?

• For this project the purpose of the link budget is to determine whether the transmitter and receiver system provide sufficient current to drive the post amp.

• Link Budget = Power Incident on Photodetector x Responsivity of the Photodetector

• Power Incident on Photodetector = [Modulation Current of Transmitter x Slope Efficiency of VCSEL] – Losses Due to Connectors and Fiber

Link Budget Analysis (Cont’d)

HFE4380-521 HFE4384-522Ith (mA)

6 6

DC bias of laser (mA)7 . 2 7 . 2

Slope Efficiency (mW/mA)0 . 0 4 0 . 1 5

Modulation Current of TX (mA)3 0 3 0

Range of Power Output (mW)0 . 2 8 8 - 1 . 2 1 . 0 8 - 4 . 5

Range of Power Output (w/ Loss) (mW)0 . 1 4 4 - 0 . 6 0 . 5 4 - 2 . 2 5

Responsivity of Lasermate PD (A/W)0 . 4 0 . 4

Responsivity of Hamamatsu PD (A/W)0 . 4 7 0 . 4 7

Range of Current from Lasermate PD (uA)5 7 . 6 - 2 4 0 2 1 6 - 9 0 0

Range of Current from Hamamatsu PD (uA)6 7 . 7 - 2 8 2 2 5 3 . 8 - 1 0 5 7 . 5

Design of the VCSEL Board

• In order to minimize reflections the VCSEL circuit had to have a total resistance of 50

• A surface mount resistor of 25 was placed in series with the VCSEL. Which has a typical resistance of 25

• A DC bias T (2k resistor in series with the 5V power supply) was connected to the circuit to allow connect to the AC coupled GTS 1250 pattern generator

Design of the VCSEL Board (cont’d)

• Once all of the components were gathered they were mounted on the board and soldered onto the board.

Testing

• The two pieces of equipment that will be used to verify the functionality of the components are the Tektronix GTS 1250 pattern generator and Tektronix 7000 Series Oscilloscope.

Testing (cont’d)

• Initially tested the Agilent opto-electronic board from the previous semester to generate an eye diagram

• GTS 1250 was connected to the transmitter portion of the board,the oscilloscope was connected to the receiver portion, and a fiber cable was used to loop the receiver and transmitter together

• Tested the VCSEL board by connecting it to the GTS 1250 and then to the Agilent board

• Tested the VCSEL board with the MAXIM transmitter board

Testing (cont’d)

• Block diagram of test setup for VCSEL

Testing (cont’d)

• Eye diagram of Agilent board

Testing (cont’d)

• Eye diagram of VSCEL board

Testing (cont’d)

• Eye diagram of VSCEL board with 1394b TX MAXIM board

Design of Etched Board

• Using the design software SuperPCB an etched board was designed and created.

SuperPCB layout of etched board top layer of etched board

Testing

• The VCSEL components were mounted on the board, but no eye diagram appeared when tested

• It was determined that the traces on the board exceed the maximum amount allowed therefore a new etched board must be created with the appropriate trace lengths

Bottom layer of etched board Top layer of etched board

Conclusion

• The VCSEL board worked according to the design and specifications and an eye diagram was produced with both the Intel/Agilent board and the 1394b MAXIM transmitter board

• The photodetector board was unable to produce an eye diagram mainly because no signal could be identified from the photodetector.

• Another possible problem with the photodetector board is that the circuit itself could be wrong

• These problems should be looked into in further detail before further testing can begin