Do we use any filter after photodiode?
Do we use a similar filter after the photodiode to get rid of the out-of-signal-space noise, before sampling?


Generally, we don't have a separate filter device or circuit. We'd rather connect the photodiode directly to a trans-impedance amplifier (TIA) chip to avoid losses due to impedance matching (the photodiode produces a current signal so we'd rather it drive a low-impedance input to the chip than a middle-impedance filter circuit).

But the other circuit elements are themselves bandwidth limited and this typically helps to reject out-of-band noise.


The photodiode has an associated parasitic capacitance that limits its bandwidth.
The TIA has limited bandwidth, which rejects higher-frequency noise.