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ECE 135 – The Three Presentation 10

This work summary discusses troubleshooting and modifications of the Aggressive Tx and Conservative Rx boards. It includes the GANTT chart, troubleshooting steps, modifications made, testing results, and plans for future work.

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ECE 135 – The Three Presentation 10

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  1. ECE 135 – The Three Presentation 10 Bryan Chavez with Pat Cleary & Kevin Parker April 14th, 2005

  2. Work Summary • Troubleshoot Board 1Γ • Soldered Aggressive Tx on Board 1 • Tested Aggressive Tx Board 1 • Verified Conservative Rx Board 1

  3. GANTT Chart

  4. Troubleshooting Board 1Γ • Pots adjusted to high resistance values • Replaced VCSEL with 100 Ohm resistor • No heating and no blown ferrite beads! • Probing showed inputs to the LD clean • Outputs of the LD dirty (vague outlines of an eye diagram) • Further probing caused a short in the circuit … blew another ferrite bead • Replaced ferrite bead … but it blew up again as power was plugged in • Cannot locate short in the circuit • Low on passives so decided to move on to Aggressive Tx design

  5. Aggressive Tx Modifications • Soldered all passives super carefully • Used a 25k potentiometer to modulate Ibias instead of 1k potentiometer • Adjusted the VCSEL orientation for forward-biasing • Adjusted pot values to safe levels before testing

  6. Aggressive Tx Probing Laser Driver Inputs Laser Driver Outputs Data - Data - Data + Data +

  7. Aggressive Tx Test Setup

  8. Aggressive Tx Results • LASING!!!! • Adjusting Imod and Ibias showed improved results

  9. Aggressive Tx Results (cont.) Working!!!!!!!!

  10. Conservative Rx Test Setup

  11. PRBS7 Pattern 9 dB BER < 10^-11 5 minute duration Proper operation verified! Conservative Rx Results

  12. Solder Aggressive Rx on Board 1 Test Aggressive Rx on Board 1 Perform Loop-back test Order More Passives Order 2nd Board Fabrication if necessary Future Work

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