1. Gigabit Ethernet PMD Opto-Link, Inc. – Status Report 9 Vinh Nguyen April 14, 2005

2. Gigabit Ethernet: Progress Summary Completed Tasks  Finished troubleshooting  Updated Bill of Materials  Updated budget to reflect latest purchases Next Week’s Tasks  Complete second board layout  Design review for next fabrication  Place order for board fabrication  Assemble second board

3. Gantt Chart

4. Current Budget

5. Projected Budget

6. Estimated Bill of Materials Part Description:Manufacturer:Mfg. Part Number:Vendor: Vendor Part Number: Unit Cost: Quantity/B oard: Total Part Cost: CAP 10000PF 50V CERAMIC X7R 0603 BC ComponentsVJ0603Y103KXACW1BCDigi-KeyBC1252TR-ND0.00346180.06228 RES 30.0 OHM 1/10W 1% 0603 SMDRohmMCR03EZPFX30R0Digi-Key RHM30.0HTR- ND0.002031 RES 100 OHM 1/10W 1% 0603 SMDRohmMCR03EZPFX1000Digi-KeyRHM100HTR-ND0.0020330.00609 RES 115 OHM 1/10W 1% 0603 SMDRohmMCR03EZPFX1150Digi-KeyRHM115HTR-ND0.002031 RES 3.00K OHM 1/10W 1% 0603 SMDRohmMCR03EZPFX3001Digi-Key RHM3.00KHTR- ND0.002031 POT 1.0K OHM 3/8" SQ CERM SL MTBourns Inc3296W-1-102Digi-Key3296W-102-ND1.0921 POT 10K OHM 3/8" SQ CERM SL MTBourns Inc3296W-1-103Digi-Key3296W-103-ND1.0921 MAX3286 Laser DriverMaxim ICMAX3286+CTIMaxim ICMAX3286+CTI4.071 MAX3264 Limiting Amplifieraxim ICMAX3264CUE+Maxim ICMAX3264CUE+4.001 PCB Fabrication RunExpress PCBProduction ServiceExpress PCB1.354381 AOC 2.5 Gbps VCSELAOCHFE419x-541AOCHFE419x-5417.251 AOC 1.25/2.5 Gbps ROSAAOCHFD3180-103AOCHFD3180-103515 Total Per Board:$23.93

7. Transmitter Testing  Last week’s transmitter problems persisted  Testing resulted in closed “eyes” for both the AOC and the Emcore board designs  The VCSEL is lasing but no signal is getting though to the receiver  Probing the board resulted in a blown inductor Transmitter PRBS7 Signal with no attenuation

8. Troubleshooting  Hypothesis: Limiting resistor values may be incorrect Would prevent the VCSEL from receiving enough current to bias it above threshold Adjusting the potentiometers would have little effect on the output signal beyond a certain level

9. Testing the Hypothesis  Set bias potentiometer to high resistance  Shorted the limiting resistor  Reduced the potentiometer resistance  Resulted in closed eye  Continued reduction of potentiometer resistance resulted in a blown Emcore VCSEL  Probing the AOC board design resulted in another blown VCSEL

10. Repairs  Replaced all damaged components on the Emcore design  Testing the repaired board resulted in closed eyes again  Tried to systematically tune potentiometers Careful tuning did not result in open eyes  Carefully probed inputs and outputs

11. Test Signals D21.5 input signal obtained using the probe Output signal for D21.5 input obtained using the optical test equipment

12. Test Signals Cont.  Tried using PRBS7 test signal as input PRBS7 input obtained using the probe plotted beside the clock signal

13. The Magic Probe  Probing between the laser driver and the VCSEL resulted in the “Magic Probe Effect”  The optical output signal formed excellent eye diagrams when the probe leads were placed between the laser driver and the VCSEL

14. Magic Probe Results Eye diagram for optical output for PRBS7 input with probe

15. Possible Explanations  The use of smaller potentiometers may have resulted in the overdriving of the laser driver chip  Board layout issues Unbalanced circuit Weird layout effects

16. Testing Hypothesis  Replaced the bias potentiometer with a larger 50 kΩ potentiometer from the practice board  Unable to obtain an open eye diagram by tuning the potentiometer  Can still obtain good eye diagrams using the “Magic Probe”  Effectively rules out overdriving hypothesis  Only leaves potential layout issues

17. Next Week  Complete second board layout Second board layout will use passive components to try to replicate the effect of the probe on the board  Design review for next board fabrication?  Place order for board fabrication  Start Final Report  Assemble second board  Get board blessed in chapel

18. Board Layout Review