Final Report 1394b:Optoelectronic Data Communications

1. Final Report1394b:Optoelectronic Data Communications Group G9: Tiffany Lovett, gte291r Tornya Moore, gte668r Mareisha Winters, gte824t ECE 4006C April 23, 2002

2. 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

3. 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.

4. 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

5. 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

6. 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)

7. 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.

8. 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

9. Comparison of Two Photodiode Candidates Lasermate RSC-M85A306 Hamamatsu S5973

10. 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 .01F.

11. 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

12. 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.

13. Testing (cont’d) • Simple square wave test with connectorized photodetector

14. Testing (cont’d) • Spectrum analysis with photodetector not connected

15. 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

16. 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

17. Comparison of Two VCSEL Candidates HFE4380-521 HFE4384-522

18. 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

19. Link Budget Analysis (Cont’d)

20. 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

21. 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.

22. 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.

23. 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

24. Testing (cont’d) • Block diagram of test setup for VCSEL

25. Testing (cont’d) • Eye diagram of Agilent board

26. Testing (cont’d) • Eye diagram of VSCEL board

27. Testing (cont’d) • Eye diagram of VSCEL board with 1394b TX MAXIM board

28. 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

29. 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

30. 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