Bit error rate performance comparison of equal channel spacing and repeated unequal spacing in reducing the four wave mixing effect in a WDM ring network

The bit error rate (BER) performance comparison of a wavelength division multiplexing (WDM) ring network in presence of four wave mixing (FWM) using repeated unequal spaced (RUS) and equal spaced (ES) scheme is reported taking into consideration of photo detector shot noise, beat noise components arising out of the beating of the signal with accumulated amplifierpsilas spontaneous emission (ASE) and crosstalk introduced at each node due to four wave mixing. It is found that RUS provides lower BER than ES for a given number of channels, total bandwidth and number of hops. The performance results evaluated at a bit rate of 10 Gbit/s show that for maintaining BER of 10^-9, the maximum number of achievable nodes are approximately 260 and 120 corresponding to receive power level -4 dBm and -7 dBm respectively for RUS scheme and ES scheme when the hop length is 5 km.