Channel coding for coherent lightwave binary FSK communications

The authors evaluate the performance of several channel coding schemes for a weakly coherent optical communications system that employs binary frequency shift keying (FSK). For the detection of signals, a double-filtering receiver structure is considered. Numerical results computed for BCH codes, Reed-Solomon codes, convolutional codes, and a concatenated code show that coding can provide a very economical solution for greatly improving the performance of such a system and for making it widely tolerant to laser phase noise. The codes evaluated demonstrated that the effects of various system impairments, such as laser phase noise and AWGN (additive white Gaussian noise), can be successfully ameliorated, providing significant relaxation of various system requirements such as SNR (signal-to-noise ratio), IF (intermediate frequency) filter bandwidth, and laser linewidth.< >