Carrier Phase Estimation in Dispersion-Unmanaged Optical Transmission Systems

TL;DR

This paper compares three carrier phase estimation methods in long-haul dispersion-unmanaged optical systems, analyzing their performance under phase noise and modulation effects, and providing analytical expressions for bit-error-rate behavior.

Contribution

It offers a comprehensive analysis and comparison of three CPE algorithms, including analytical performance predictions considering phase noise effects.

Findings

Viterbi-Viterbi outperforms others at low phase noise

All methods converge at high phase noise levels

Differences diminish with higher modulation formats

Abstract

The study on carrier phase estimation (CPE) approaches, involving a one-tap normalized least-mean-square (NLMS) algorithm, a block-wise average algorithm, and a Viterbi-Viterbi algorithm has been carried out in the long-haul high-capacity dispersion-unmanaged coherent optical systems. The close-form expressions and analytical predictions for bit-error-rate behaviors in these CPE methods have been analyzed by considering both the laser phase noise and the equalization enhanced phase noise. It is found that the Viterbi-Viterbi algorithm outperforms the one-tap NLMS and the block-wise average algorithms for a small phase noise variance (or effective phase noise variance), while the three CPE methods converge to a similar performance for a large phase noise variance (or effective phase noise variance). In addition, the differences between the three CPE approaches become smaller for higher-level modulation formats.