Multi-Rate Nyquist-SCM for C-Band 100Gbit/s Signal over 50km Dispersion-Uncompensated Link

TL;DR

This paper introduces a novel multi-rate Nyquist-SCM technique for C-band 100Gbit/s optical transmission over 50km without dispersion compensation, effectively mitigating chromatic dispersion effects and maximizing capacity.

Contribution

It proposes the first multi-rate Nyquist-SCM approach for dispersion-uncompensated links, enhancing spectral efficiency and signal recovery in high-speed optical communications.

Findings

Achieves 7% FEC limit at -4dBm received power

Attains normalized GMI of 0.967 at high SNR

Effectively mitigates chromatic dispersion effects

Abstract

In this paper, to the best of our knowledge, we propose the first multi-rate Nyquist-subcarriers modulation (SCM) for C-band 100Gbit/s signal transmission over 50km dispersion-uncompensated link. Chromatic dispersion (CD) introduces severe spectral nulls on optical double-sideband signal, which greatly degrades the performance of intensity-modulation and direct-detection systems. Based on the prior knowledge of the dispersive channel, Nyquist-SCM with multi-rate subcarriers is proposed to keep away from the CD-caused spectral nulls flexibly. Signal on each subcarrier can be individually recovered by a digital signal processing, including the feed-forward equalizer with no more than 31 taps, a two-tap post filter, and maximum likelihood sequence estimation with one memory length. Combining with entropy loading based on probabilistic constellation shaping to maximize the capacity-reach, the C-band 100Gbit/s multi-rate Nyquist-SCM signal over 50km dispersion-uncompensated link can achieve 7% hard-decision forward error correction limit and average normalized generalized mutual information of 0.967 at received optical power of -4dBm and optical signal-to-noise ratio of 47.67dB. In conclusion, the multi-rate Nyquist-SCM shows great potentials in solving the CD-caused spectral distortions.