Simplified Iterative Decoder for Polybinary-Shaped Optical Signals in Super-Nyquist Wavelength Division Multiplexed Systems

Shuai YUAN  Koji IGARASHI  

Publication
IEICE TRANSACTIONS on Communications   Vol.E102-B   No.4   pp.818-823
Publication Date: 2019/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2018EBP3179
Type of Manuscript: PAPER
Category: Fiber-Optic Transmission for Communications
Keyword: 
wavelength division multiplexing,  forward error correction,  maximum likelihood decoder,  

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Summary: 
In super-Nyquist wavelength division multiplexed systems, performance of forward error correction (FEC) can be improved by an iterative decoder between a maximum likelihood decoder for polybinary shaping and an FEC decoder. The typical iterative decoder includes not only the iteration between the first and second decoders but also the internal iteration within the FEC decoder. Such two-fold loop configuration would increase the computational complexity for decoding. In this paper, we propose the simplified iterative decoder, where the internal iteration in the FEC decoder is not performed, reducing the computational complexity. We numerically evaluate the bit-error rate performance of polybinary-shaped QPSK signals in the simplified iterative decoder. The numerical results show that the FEC performance can be improved in the simplified scheme, compared with the typical iterative decoder. In addition, the performance of the simplified iterative decoder has been investigated by the extrinsic information transfer (EXIT) chart.