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

By A. Alvarado, Erik Agrell, D. Lavery, R. Maher, Polina Bayvel. Journal of Lightwave Technology, 2015

322 citations recorded by the source corpus.

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.

Subfields: Computer Networks and Communications, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/e230cc5db67bfef72879126959d11bcf1ee92a56

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Citations in the corpus

Rate Adaptation and Reach Increase by Probabilistically Shaped 64-QAM: An Experimental Demonstration (2016, methodology): “We further indicate in Table II the Iawgn thresholds, the Ibmd thresholds (as proposed in [41]) (see Section III for the definition of Iawgn, Ibmd) and the equivalent pre-FEC BER thresholds for the codes and the modulation format they are used with.”
Probabilistic Constellation Shaping for Optical Fiber Communications (2019, methodology): “After proper normalization of the GMI, we can derive a channel metric that quantiﬁes the number of information bits per transmitted bit , which is called the normalized GMI (NGMI) [79]–[81].”
Bandwidth Efficient and Rate-Matched Low-Density Parity-Check Coded Modulation (2015, background): “In [83], it was observed that the achievable rate R∗ approximately determines Pe.”