ECE 135 – The Three Presentation 10 Bryan Chavez with Pat Cleary & Kevin Parker April 14 th, 2005...
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Transcript of ECE 135 – The Three Presentation 10 Bryan Chavez with Pat Cleary & Kevin Parker April 14 th, 2005...
ECE 135 – The ThreeECE 135 – The Three Presentation 10 Presentation 10
Bryan ChavezBryan Chavezwith Pat Cleary & Kevin Parkerwith Pat Cleary & Kevin Parker
April 14April 14thth, 2005 , 2005
Work SummaryWork Summary
Troubleshoot Board 1Troubleshoot Board 1ΓΓ
Soldered Aggressive Tx on Board 1Soldered Aggressive Tx on Board 1
Tested Aggressive Tx Board 1Tested Aggressive Tx Board 1
Verified Conservative Rx Board 1Verified Conservative Rx Board 1
GANTT ChartGANTT Chart
Troubleshooting Board 1Troubleshooting Board 1ΓΓ
Pots adjusted to high resistance valuesPots adjusted to high resistance valuesReplaced VCSEL with 100 Ohm resistorReplaced VCSEL with 100 Ohm resistorNo heating and no blown ferrite beads!No heating and no blown ferrite beads!Probing showed inputs to the LD cleanProbing showed inputs to the LD cleanOutputs of the LD dirty (vague outlines of an eye Outputs of the LD dirty (vague outlines of an eye diagram)diagram)Further probing caused a short in the circuit … blew Further probing caused a short in the circuit … blew another ferrite beadanother ferrite beadReplaced ferrite bead … but it blew up again as power Replaced ferrite bead … but it blew up again as power was plugged inwas plugged inCannot locate short in the circuitCannot locate short in the circuitLow on passives so decided to move on to Aggressive Low on passives so decided to move on to Aggressive Tx designTx design
Aggressive Tx ModificationsAggressive Tx Modifications
Soldered all passives super carefully Soldered all passives super carefully
Used a 25k potentiometer to modulate IUsed a 25k potentiometer to modulate Ibias bias
instead of 1k potentiometerinstead of 1k potentiometer
Adjusted the VCSEL orientation for Adjusted the VCSEL orientation for forward-biasingforward-biasing
Adjusted pot values to safe levels before Adjusted pot values to safe levels before testingtesting
Aggressive Tx ProbingAggressive Tx ProbingLaser Driver Inputs Laser Driver Outputs
Data -
Data +
Data -
Data +
Aggressive Tx Test SetupAggressive Tx Test Setup
Aggressive Tx ResultsAggressive Tx Results
LASING!!!!LASING!!!!
Adjusting IAdjusting Imodmod
and Iand Ibias bias
showed showed improved improved resultsresults
Aggressive Tx Results (cont.)Aggressive Tx Results (cont.)
Working!!!!!!!!
Conservative Rx Test SetupConservative Rx Test Setup
Conservative Rx ResultsConservative Rx Results
PRBS7 PatternPRBS7 Pattern9 dB9 dBBER < 10^-11BER < 10^-115 minute duration5 minute durationProper operation verified!Proper operation verified!
Future WorkFuture Work
Solder Aggressive Rx on Board 1Solder Aggressive Rx on Board 1
Test Aggressive Rx on Board 1Test Aggressive Rx on Board 1
Perform Loop-back testPerform Loop-back test
Order More PassivesOrder More Passives
Order 2Order 2ndnd Board Fabrication if Board Fabrication if necessarynecessary