Performance limitations of WDM optical transmission system due to cross-phase modulation in presence of chromatic dispersion

With the increasing demands on the capacity of wavelength division multiplexed (WDM) systems, nonlinear effects including inter-channel crosstalk become increasingly important. One of the most significant nonlinear effects in this context is cross-phase modulation (XPM) in optical fiber and accurate determination of this effect is an important issue in the design of WDM optical system. This paper presents XPM theory in brief and simulation results for intensity fluctuation due to XPM in an intensity modulation-direct detection (IM-DD) WDM optical transmission system at a bit rate of 10 Gbit/s. The spectral characteristics have been found to be strongly dependent on channel spacing and dispersion coefficient. It is shown that the system suffers maximum penalty due to XPM effect at zero dispersion coefficient and XPM interference is linearly dependent on the optical powers of the injected signals in a very large range of system parameters. For example, the eye opening penalty is about 8.10 dB and 1.45 dB for corresponding dispersion coefficients of 0.5 ps/nm-km and 4.0 ps/nm-km respectively at a probability of 10^-3.