The receiver performance of optical Costas PLL's is evaluated accounting for the effects of laser phase noise, shot noise and the data-to-phaselock crosstalk induced by signal waveform distortion. In contrast to the conventional discussion in which the received signal data is a sequence of square pulses, this paper for the first time investigates the problem encountered in BPSK homodyne communication systems with Costas PLL's as the received signal data is not a sequence of square pulses but is a sequence of distorted pulses. The signal waveform distortion induces additional amount of phase error variance and henceforth an incresae in bit-error rate, resulting in a more stringent laser linewidth requirement. The laser linewidth requirement is evaluated here taking into account such an effect of signal waveform distortion.

We analyze the system performance of optical heterodyne CPFSK receivers with AFC loops. The effects of closed loop gain and postdetection filters are taken into account.The GQR (Gaussian quadrature rule) method is used to deal with the laser phase noise characteristics in computing the bit-error rates. The impact of closed loop gain on the system performance is investigated. The optimum design of postdetection filters is outlined in showing the improvement of system performance compared with the system without AFC.