Performance Comparison of Wavelength Shift Keying and Conventional on Off Keying Schemes in a Multi-Hop Optical Ring Network in Presence of Four Wave Mixing Cross Talk

A transmission performance study is carried out for an all-optical multi-wavelength metropolitan optical ring network (MON). Effect of using a wavelength shift keying (WSK) scheme is analyzed and compared to that of the conventional on off keying system (OOK) in respect of four wave mixing (FWM) cross talk. The performance results are evaluated at a bit rate of 10Gb/s taking into considerations the combined influence of photo detector shot noise, beat noise components arising out of the beating of the signal with accumulated amplifier´s spontaneous emission (ASE) and cross talk introduced at each node due to four wave photon mixing. The computed results show that for 50 hops the bit error rate (BER) of the standard wavelength division multiplexing (WDM) system is higher than 10^-12 while for the wavelength shift keying system, for the same received power the BER is lower than 10^-16 for the hop length of 100 km. It is also shown that for a given BER, WSK-WDM technique provides higher values of both the maximum allowable number of hops and minimum required power.