Transcript Presentation 10

ECE 135 – The Three
Presentation 10
Bryan Chavez
with Pat Cleary & Kevin Parker
April 14th, 2005
Work Summary
Troubleshoot Board 1Γ
Soldered Aggressive Tx on Board 1
Tested Aggressive Tx Board 1
Verified Conservative Rx Board 1
GANTT Chart
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
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
Aggressive Tx Probing
Laser Driver Inputs
Laser Driver Outputs
Data -
Data -
Data +
Data +
Aggressive Tx Test Setup
Aggressive Tx Results
LASING!!!!
Adjusting Imod
and Ibias
showed
improved
results
Aggressive Tx Results (cont.)
Working!!!!!!!!
Conservative Rx Test Setup
Conservative Rx Results
PRBS7 Pattern
9 dB
BER < 10^-11
5 minute duration
Proper operation verified!
Future Work
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