Hi,
I'm trying to develop a laser driver circuit for fiber sensing application. I'm using pretty much the same circuit given in datasheet, figure 20.
Here are some other details,
-Circuit is connected to an FPGA board through an FMC connector.
-Input DIN signal is LVDS, coming from FPGA (AC coupled- as in datasheet)
- Laser diode is RIO Planex (with custom TEC driver)
- Detector is SIR5-FC
- Instead of two series coils, I used one with a value of 1500nH
-In bias path, I didn't use an coil, since laser itself already has one in package
I made one assumption that this device can work with lower speeds (thus longer pulses), since SDD11 is given from 0.01 to 11 Gbps.
What I see is that pulse amplitudes varies too much Please see the waveform. Bias register is set to 1, and modulation current is set to 500. I'm ruling out temperature change in laser, cause when I monitor thermistor voltage at package pin, I don't see any correlation. Event though, temperature shouldn't change this fast.
Do you have any idea what might be the problem(s)?
Thanks,
Murat