Improving soft FEC performance for higher-order modulations via optimized bit channel mappings.

C. Häger, A.G. i Amat, F. Brännström, A. Alvarado, E. Agrell

Research output: Contribution to journalArticleAcademicpeer-review

20 Citations (Scopus)
65 Downloads (Pure)


Soft forward error correction with higher-order modulations is often implemented in practice via the pragmatic bit-interleaved coded modulation paradigm, where a single binary code is mapped to a nonbinary modulation. In this paper, we study the optimization of the mapping of the coded bits to the modulation bits for a polarization-multiplexed fiber-optical system without optical inline dispersion compensation. Our focus is on protograph-based low-density parity-check (LDPC) codes which allow for an efficient hardware implementation, suitable for high-speed optical communications. The optimization is applied to the AR4JA protograph family, and further extended to protograph-based spatially coupled LDPC codes assuming a windowed decoder. Full field simulations via the split-step Fourier method are used to verify the analysis. The results show performance gains of up to 0.25 dB, which translate into a possible extension of the transmission reach by roughly up to 8%, without significantly increasing the system complexity.
Original languageEnglish
Pages (from-to)14544-58
Number of pages15
JournalOptics Express
Issue number12
Publication statusPublished - 2014


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