Intrachannel four-wave mixing in highly dispersed RZ-DPSK transmission with a non-symmetric dispersion map

Nonlinear penalties due to intrachannel four-wave mixing (IFWM) in highly dispersed return-to-zero differential-phase-shift- keyed (RZ-DPSK) transmission are studied for both symmetric and non-symmetric dispersion maps. As the dispersion map changes from symmetric to non-symmetric, the nonlinear amplitude fluctuation overtakes the effect of the nonlinear phase fluctuation and dominates the system's nonlinear performance. The impact of IFWM on the bit error rate (BER) is estimated using a simple model based on Gaussian approximations for the nonlinear amplitude and phase fluctuations.