Enhancing oFEC using MAP Decoding of BCH Component Codes

Forward error correction (FEC) plays a vital role in optical communication. The open FEC code (oFEC) is a very efficient code suitable for high-speed optical communication and used for e.g. 200-800 Gbit/s solutions. The oFEC code is based on component BCH codes. We investigate maximum a posteriori (MAP) algorithms for soft-in soft-out (SISO) decoding of the BCH codes and present an efficient algorithm that speeds up this MAP decoding significantly. In simulations, we demonstrate a SISO MAP decoding that satisfies the ITU-T 709.3 specification of a bit error rate (BER) output value of 10⁻⁹ at a BER input value of 0.025. In terms of coding gain, this corresponds to an improvement of 0.4 dB compared to the requirement of the ITU-T 709.3 specification.