WE START OUT BY DERIVING an expression for the statistics of the photocurrent in the pin receiver, along the lines of [BL90, RH90]. It is useful to think of the photodetection process in the following way. Each time a photon hits the receiver, the receiver generates a small current pulse. Let tk denote the arrival times of photons at the receiver. Then the photocurrent generated can be expressed as
where e is the electronic charge and eh(t – tk) denotes the current impulse due to a photon arriving at time tk. Note that since eh(t – tk) is the current due to a single electron, we must have
The arrival ...