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ORIGINAL RESEARCH article

Front. Phys.
Sec. Optics and Photonics
Volume 12 - 2024 | doi: 10.3389/fphy.2024.1452087

A Simple Two-Stage Carrier-Phase Estimation Algorithm for 32-QAM Coherent Optical Communication Systems

Provisionally accepted
Min Peng Min Peng 1Xiangqing Wang Xiangqing Wang 2*Xiaokun Yang Xiaokun Yang 1Dongfei Wang Dongfei Wang 1
  • 1 Wuhan Technology and Business University, Wuhan, China
  • 2 Fuyang Normal University, Fuyang, China

The final, formatted version of the article will be published soon.

    The combination of high-order modulation formats and linewidth-tolerant carrier phase estimation (CPE) can effectively improve spectrum efficiency and relax the limitation of laser linewidth. This paper presents a simple two-stage CPE algorithm for polarization-multiplexed (PM) 32-quadrature amplitude modulation (32-QAM) coherent optical communication systems. The algorithm uses an enhanced QPSK partitioning algorithm combined with a simplified 4th power CPE method for coarse estimation in the initial stage and maximum likelihood (ML) detection in the subsequent fine stage. The CPE algorithm significantly increases the number of symbols used in the first stage of coarse estimation. This results in a significant increase in the stability and reliability of the phase estimation, and the CPE algorithm significantly reduces the computational complexity. The optimal parameters, phase estimation performance, and system performance of the algorithm were investigated by building a 22 Gbaud PM 32-QAM coherent system simulation platform and a 5 Gbaud PM 32-QAM coherent system experimental platform. The results show that the proposed two-stage CPE algorithm has a stronger linewidth tolerance difference than the conventional QPSK, and the two-stage CPE algorithm with an optimal block length of 105 performs comparable to blind phase search (BPS). The optical signal noise Ratio (OSNR) value is 21.2 dB and the bit error rate (BER) is 1.8 × 10 -3 for the optimal block length of 105. The receiving-end DSP unit with a flexible scheme and good communication performance will have potential applications in adaptive elastic optical networks.

    Keywords: Coherent optical communications, Quadrature amplitude modulation, Carrier phase estimation, QPSK-partitioning, Blind phase search

    Received: 20 Jun 2024; Accepted: 26 Aug 2024.

    Copyright: © 2024 Peng, Wang, Yang and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Xiangqing Wang, Fuyang Normal University, Fuyang, China

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.