Impact of nonlinear phase noise on direct detection DQPSK systems

Abstract

The error probability of differential quadrature phase-shift keying (DQPSK) systems is analyzed considering both selfand cross-phase modulation (SPM and XPM)-induced nonlinear phase noise. XPM-induced nonlinear phase noise is treated here as Gaussian distributed phase noise. In DQPSK systems where group velocity dispersion (GVD) is perfectly compensated span after span, the influence of XPM-induced nonlinear phase noise on the error bribability performance can be dominant compared with that of the SPM-induced nonlinear phase noise. The 10-Gb/s systems, whose walkoff length is larger than that of the 40 Gb/s systems, are more sensitive to XPM-induced nonlinear phase noise.