Information Rates of Next-Generation Long-Haul Optical Fiber Systems Using Coded Modulation

Abstract

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 soft-decision (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.

submitted to IEEE/OSA Journal of Lightwave Technology

References in corpus (2)

• On Achievable Rates for Long-Haul Fiber-Optic Communications
• Capacity of a Nonlinear Optical Channel with Finite Memory

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• Achievable Information Rates for Fiber Optics: Applications and Computations
• Performance Prediction of Nonbinary Forward Error Correction in Optical Transmission Experiments
• Nonlinearity Mitigation in WDM Systems: Models, Strategies, and Achievable Rates
• Achievable Information Rates for Coded Modulation with Hard Decision Decoding for Coherent Fiber-Optic Systems
• Performance Prediction Recipes for Optical Links
• Improved Lower Bounds on Mutual Information Accounting for Nonlinear Signal-Noise Interaction