Concatenated non-binary LDPC and HD-FEC codes for 100Gb/s optical transport systems

In this paper, we propose a soft-decision-based FEC scheme which is the concatenation of a non-binary LDPC (NB-LDPC) code and hard-decision FEC code having a compatibility with existing OTU-4 frame structure. The proposed concatenated NB-LDPC + RS frame structure is also provided and the entire frame size is 18,368 bytes. The proposed NB-LDPC(2304,2048) code over GF(2⁴) provides a superior performance at the higher BER region and can be concatenated with HD-FEC code. The simulation result shows that the proposed concatenated NB-LDPC(2304,2048) and RS(255,239) FEC can provide a superior NCG performance over 10.3 dB at a post-FEC BER 10⁻¹⁵ and over 10.8 dB with enhanced HD-FEC in the outer code. As a result, the proposed NB-LDPC codes are expected to be strong FEC candidates of soft-decision FEC for 100Gb/s optical transmission system.