On the capacity of a direct-detection photon channel with intertransition-constrained binary input

The classical directed detection photon channel is modeled by an output nu /sub t/ (observed signal) describing the photon-arrival Poisson (count) process with intensity (rate) lambda /sub t/+ lambda /sub 0/, where lambda /sub t/ (photons/s) is the channel input (information carrying) intensity and lambda /sub 0/ (photons/s) is the dark current intensity. Upper and lower bounds on the capacity of this channel are presented for two-level (binary) inputs taking on the extreme value lambda /sub t/ in (0,A), where A denotes the peak power satisfying an average power constraint E( lambda /sub t/)>