1. Laser Drive Needs Total laser current BIAS Current
ITOT = IBIAS + IMOD
BIAS Current
Keeps ITOT > ITH (laser “on”)
IBIAS – ITH related to speed
Modulation (MOD) Current
Shaped by the data
Larger IMOD gives larger signal
IBIAS
IMOD
ITOT

2. MAX3287 Evaluation Kit

3. Test Setup for Maxim board
Tested to verify its functionality
Two test conducted for Maxim board
DC coupled output of Maxim board
AC coupled output of Maxim board
Equipment used
5V power supply
SMA cables and connectors
Oscilloscope and function generator

4. Test Results for Maxim board DC coupled
Near perfect open eye
Fits the compliance mask
Signifies very low SNR
Slight dip at the bottom (unexplained phenomenon)

5. Test Results for Maxim board AC coupled
Again a near perfect open eye
Low SNR
Fits the compliance mask
The dip on bottom disappears (mysteriously)

6. Circuit from unstuffed part of MAX 3287 Eval board
Remove feedback loop PD, bias adjustment PNP

7. Circuit from unstuffed part of MAX 3287 Eval board
Keep almost all other components
Use Eval board part numbers for inductors (ferrite beads)

8. Design elements Match load on OUT- with OUT+ as well as you can
Need to adjust Laser DC Bias current
Need to adjust Laser modulation current