Sensitivity of a direct WDM-system with a frequency selective optical receiver and optical preamplifier

We present an accurate model for the evaluation of the performance of a direct detection system with frequency selective Fabry-Perot (FP) filter and optical preamplification. The model includes the Poisson statistics of photodetection, a realistic model of the polarization behavior of the amplified spontaneous emission and the degradation of the system due to intersymbol interference (ISI). The influence of filtered white noise is taken into account by the expansion in a set of orthonormal functions. We discuss the implementation of a polarization filter for the rigorous model as well as the optimum bandwidth-bit duration (BT) product. The results confirm that the optimum bandwidth-bit duration product has a value of 6 for the discussed system.