Transmission limitations in optical WDM networks due to cross-phase modulation

High power optical amplifiers and dispersion management enable increased length of inter-amplifier spans in multi-channel high bit-rate transmission systems. The bit-rate-distance product is limited by the combined effects of fibre dispersion and non-linear effects due to the high launched power into the fibre. In a dispersive fibre, the combined effects of self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) affect the transmission performance. Phase modulation due to XPM has a significant influence on a WDM system as it affects channels over a continuous wavelength range and is converted into amplitude distortion by residual dispersion. Little work has been done investigating the XPM induced pulse distortion systematically in dependence of a wide range of parameters. We present an experimental and theoretical investigation of an XPM impaired system depending on fibre dispersion, channel wavelength spacing, bit-rate and pulse form. Excellent agreement has been found between the experimental and computer simulation results