Impact of decision threshold on performance of optically amplified synchronous coherent optical ASK systems in presence of laser phase noise

The phase fluctuations in semiconductor lasers have shown to be an important source of sensitivity degradation in coherent lightwave systems. In this paper, we analyze the performance of amplifier based synchronous heterodyne binary ASK systems by taking into account the combined effects of the noise arising due to the optical amplifiers, receiver and the phase fluctuations of the transmitter and local oscillator lasers. Special attention is paid towards the study of the influence of optimum threshold on the bit error rate of binary ASK systems both in absence and presence of optical amplifiers, for different amounts of laser phase noise.