Large Girth Low-Density Parity-Check Codes for Long-Haul High-Speed Optical Communications

An FEC scheme based on large girth LDPC codes is proposed. A girth-10 block-circulant LDPC code of rate 0.8 outperforms its turbo-product code counterpart by 0.95 dB at BER of 10^-10, on an AWGN channel. It provides the net effective coding gain of 10.95 dB at BER of 10^-12. In long-haul optical transmission at 40-Gb/s it provides at least 1.47 dB improvement over corresponding turbo-product code.