Parametric-gain approach to the analysis of DPSK dispersion-managed systems

We review a recently proposed method for bit error rate (BER) evaluation of differential phase shift keying (DPSK) long haul dispersion-managed (DM) optical systems, based on a parametric gain modeling of the nonlinear interaction between signal and amplified spontaneous emission noise along the DM transmission line. Such an interaction is responsible of nonlinear phase noise, which is the main nonlinear impairment in DPSK longhaul transmission.We review the fundamentals of the novel DPSK BER evaluation method, which extends Forestieri’s method for on-off keying modulation to the DPSK case. The method avoids calculation of the nonlinear phase statistics, and accounts for intersymbol interference due to nonlinear waveform distortion, and both optical and electrical filtering. The method is critically based on the assumption of Gaussian statistics of the received optical field. In this paper, we provide further evidence of the appropriateness of the Gaussian assumption, by showing multicanonical simulations of the probability density function (PDF) of both the received optical field and of the photodetected decision variable, with a comparison to the theoretical PDF