Information rates of next-generation long-haul optical fiber systems using coded modulation
Journal article, 2017

A comprehensive study of the coded performance of long-haul spectrally-efficient WDM optical fiber transmission systems with different coded modulation decoding structures is presented. Achievable information rates are derived for three different square QAM formats and the optimal format is identified as a function of distance and specific decoder implementation. The four cases analyzed combine hard-decision (HD) or softdecision (SD) decoding together with either a bit-wise or a symbol-wise demapper, the last two suitable for binary and nonbinary codes, respectively. The information rates achievable for each scheme are calculated based on the mismatched decoder principle. These quantities represent true indicators of the coded performance of the system for specific decoder implementations and when the modulation format and its input distribution are fixed. In combination with the structure of the decoder, two different receiver-side equalization strategies are also analyzed: electronic dispersion compensation and digital backpropagation. We show that, somewhat unexpectedly, schemes based on nonbinary HD codes can achieve information rates comparable to SD decoders and that, when SD is used, switching from a symbol-wise to a bit-wise decoder results in a negligible penalty. Conversely, from an information-theoretic standpoint, HD binary decoders are shown to be unsuitable for spectrally-efficient, long-haul systems.

generalized mutual information

soft-decision decoding

forward error correction

coded modulation

optical communications

Achievable information rates

mutual information

nonbinary codes

hard-decision decoding


Gabriele Liga

University College London (UCL)

Alex Alvarado Segovia

Eindhoven University of Technology

Erik Agrell

Chalmers, Signals and Systems, Communication, Antennas and Optical Networks

Polina Bayvel

University College London (UCL)

Journal of Lightwave Technology

0733-8724 (ISSN) 1558-2213 (eISSN)

Vol. 35 1 113-123 7553569

Subject Categories

Other Electrical Engineering, Electronic Engineering, Information Engineering



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