Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems

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Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems

Alvarado, A; Agrell, E; Laver, D; Maher, R; Bayvel, P; (2016) Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems. Journal of Lightwave Technology , 34 (2) pp. 707-721. 10.1109/JLT.2015.2482718. Green open access

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Abstract

The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high-order modulation formats, the use of the soft-decision FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis.

Type:	Article
Title:	Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
Open access status:	An open access version is available from UCL Discovery
DOI:	10.1109/JLT.2015.2482718
Publisher version:	http://dx.doi.org/10.1109/JLT.2015.2482718
Language:	English
Additional information:	Copyright © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Keywords:	Bit error rate, forward error correction, generalized mutual information, mutual information, soft-decision decoding
UCL classification:	UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI:	https://discovery.ucl.ac.uk/id/eprint/1481350