Low-Complexity Zipper-LDPC and Low-Latency Zipper-BCH Concatenated Codes

A novel concatenated forward error correction (FEC) scheme is proposed that consists of an inner zipper framework with low-density parity-check component codes and an outer zipper framework with BCH component codes. The proposed soft-decision inner codes have a universal, flexible, and implementation-friendly structure with low decoding complexity. The inner code is error-reducing, tasked with reducing the error rate on bits passed to the outer hard decision code below its threshold. The proposed outer codes have ultra-low overhead and are designed to have small decoding memory and latency. Computer simulations show that the proposed zipper-BCH codes can reduce the decoding latency and required memory by up to a factor of 30, compared to the conventional zipper codes, while maintaining a minimal performance loss. The proposed scheme is considered with higher-order modulation with both multi-level coding and bit-interleaved coded modulation. Simulations show that the concatenated FEC scheme can provide a 0.1 dB gain over the state-of-the-art FEC designs, making it a highly attractive FEC solution for high-throughput optical communication systems.