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Four-Wave-Mixing in Optical ASK WDM Transmission System Employing Heterodyne Detection

We analyze the impact of four-wave-mixing (FWM) in optical fibers on wavelength-division-multiplexed (WDM) optical communication systems employing amplitude-shift-keying (ASK) and heterodyne detection. The manifestation of fiber FWM in the receiver is viewed as an interference process, and a suitable statistical model is developed for the same including the influence of receiver bandpass filter on the FWM interference. The receiver bit-error-probability (BEP) is evaluated in presence of the FWM interference and the receiver shot noise. For a given fiber, the plot of receiver BEP versus received optical power shows an irreducible minimum which depends on the transmission distance (TD). For a 16 channel 1 Gbit/s WDM ASK system, the maximum TD for a BEP min is 229 km for nondispersion-shifted (NDS) fibers, which is 21 km larger than the same for dispersion-shifted (DS) fibers. The receiver power penalty (RPP) due to the FWM as compared to the shot noise limited operation is also evaluated. For the present system the FWM leads to the RPP of 1.54 dB and 1.39 dB for DS and NDS fibers respectively when operating at the corresponding maximum TDs.