Applications for quantum amplifiers in simple digital optical communication systems

Previously published results on the performance of optical direct detection digital receivers using avalanche detectors are extended to the case where incoherent noise due to quantum amplifiers in the transmission medium is present at the detector. These calculations are applied to determine the usefulness of quantum amplifiers in simple digital transmission systems where the optical source instability results in a required amplifier bandwidth which may be orders of magnitude greater than the modulation bandwidth. It is concluded that practical applications exist where quantum amplifiers can be used in analog repeaters between regenerating repeaters in a hybrid digital system; and also as front ends of regenerating repeaters to increase their sensitivities.