Photodiode bias issues
Consider the impact of the noise in the bias voltage of the PD on the noise figure of the system:
- Use a separate LDO for photodiodes bias + careful decoupling at EACH photodiode anode pin.
- Do not use jumpers or long traces on the PD bias net, it's very noise-sensitive.
- Do not use +3V3 coming from the FMC to bias the PD.