Effect of fibre dispersion on four-wave mixing in multichannel coherent optical transmission system

Severe bit error rate degradations and strong error rate floors caused by fibre four-wave mixing (FWM) in a high launch power, seven channel, coherent optical transmission system are reported. The critical influence of fibre chronic dispersion is highlighted, with a negligible penalty after transmission over conventional step index fibre, even for a launch power of +17 dBm. Several orders of FWM products are visible in the optical spectra for dispersion shifted fibre.