code (TC) decoders. A soft-decoding algorithm, the Bahl, Cocke, Jelinek, and Raviv (BCJR)
decoding algorithm, and there exist standard TCs for additive white Gaussian noise (AWGN)
channels. We show that using a MAP decoding algorithm based on the Gaussian noise
assumptions, however, may significantly degrade the TC decoder performance in an optical-
fiber channel with non-Gaussian ASE noise. To take full advantage of TC, the accurate noise …