Laser Drive Needs Total laser current –I TOT = I BIAS + I MOD BIAS Current –Keeps I TOT > I TH (laser “on”) –I BIAS – I TH related to speed Modulation (MOD) Current –Shaped by the data –Larger I MOD gives larger signal I BIAS I MOD I TOT

MAX3287 Evaluation Kit

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

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)

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 – AC coupling?)

Circuit from unstuffed part of MAX 3287 Eval board Remove feedback loop PD, bias adjustment PNP RED Note: Pin 2 is really “FLTDLY” NOT “POR” as in MAXIM data sheet. So it must be grounded.

Circuit from unstuffed part of MAX 3287 Eval board Remove C25 and R27 RED Keep all other components GREEN Use Eval board part numbers for inductors (ferrite beads)

Design elements Match load on OUT- with OUT+ as well as you can (R26) Need to be able to adjust Laser DC Bias current (R1) Need to be able to adjust Laser modulation current (R25)