Performance evaluation of CPFSK lightwave systems

The receiver sensitivity of polarization diversity continuous-phase frequency-shift-keyed (CPFSK) lightwave systems with differential detection is determined using a technique which combines computer simulation, to determine a probabilistic characterization of the signal at the receiver output, with a formula-based method of evaluating the bit error ratio. This approach permits consideration of laser phase noise, nonlinear signal processing, and nonideal components within a general framework. In particular, the technique captures the asymmetry in the probability density function of the sampled signal at the received output. Numerical results yield a sensitivity at a bit error ratio of 10/sup -9/, which is 4 dB better than that obtained with a simpler Gaussian approximation.<>