Comparison of Short Blocklength Sphere Shaping and Nonlinearity Compensation in WDM Systems

TL;DR

This paper compares short blocklength sphere shaping with nonlinear compensation techniques in WDM systems, showing that sphere shaping with a Volterra-based equalizer can achieve comparable or better performance with lower complexity.

Contribution

It introduces a comparison between sphere shaping and fiber nonlinearity compensation methods, highlighting the effectiveness of sphere shaping combined with VNLE in WDM systems.

Findings

ESS with VNLE achieves similar performance to uniform signaling with DBP in single-channel.

ESS outperforms uniform signaling with DBP in dense WDM systems.

Sphere shaping improves nonlinear tolerance and system performance.

Abstract

In optical communication systems, short blocklength probabilistic enumerative sphere shaping (ESS) provides both linear shaping gain and nonlinear tolerance. In this work, we investigate the performance and complexity of ESS in comparison with fiber nonlinearity compensation via digital back propagation (DBP) with different steps per span. We evaluate the impact of the shaping blocklength in terms of nonlinear tolerance and also consider the case of ESS with a Volterra-based nonlinear equalizer (VNLE), which provides lower complexity than DBP. In single-channel transmission, ESS with VNLE achieves similar performance in terms of finite length bit-metric decoding rate to uniform signaling with one step per span DBP. In the context of a dense wavelength-division multiplexing (WDM) transmission system, we show that ESS outperforms uniform signaling with DBP for different step sizes.