Near-quantum optimum receivers for the phase-quadrature coherent-state channel.

A theoretical analysis of two simple implementations for optical receivers that achieve near-quantum optimum performance for phase-quadrature coherent-state signaling is carried out. For a large received average photon count per symbol, N(s), the error probability is proportional to exp(-2N(s)) as opposed to the conventional heterodyne performance of exp(-N(s)/2).