OCF: Q7

What two processes must a photodetector perform to be able to work?

In which layer of a pn-photodiode is it preferable to have the most absorption?

Why does a pin-photodiode increase performance compared to a pn-photodiode?

How do we optimize the efficiency of a photodiode?

What limits the transit time of a photodiode?

What are the four types of photodetectors that we discussed?

What constitutes the front end of an optical receiver?
What are the important parameters when designing the front end?

Which kind of front end provides both high responsivity and large bandwidth?

What are the fundamental noise mechanisms that result in current fluctuations in optical receivers?

What is the source of shot noise?
Which probability distribution function describes shot noise?

What is the source of thermal noise (a.k.a. Johnson noise or Nyquist noise)?

The dominance of either shot or thermal noise depends on the input optical pwr. at the PIN receiver. State the cases where one is dominant over the other and write the equations for the SNR of the received electrical signal for the two cases.

Why does the enhancement of the responsivity in an APD receiver result in a reduction of the SNR?