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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Phase and Frequency Recovery Algorithms for Probabilistically Shaped Transmission

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Barbosa, Fabio Aparecido [1] ; Rossi, Sandro M. [2] ; Mello, Darli A. A. [1]
Total Authors: 3
[1] Univ Estadual Campinas, Sch Elect & Comp Engn, BR-13083970 Campinas, SP - Brazil
[2] CPqD, Div Opt Technol, BR-13086902 Campinas, SP - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Journal of Lightwave Technology; v. 38, n. 7, p. 1827-1835, APR 1 2020.
Web of Science Citations: 0

In additive white Gaussian noise (AWGN) channels, probabilistic shaping (PS) approaches the information-theoretical capacity using typical squareM-ary quadrature amplitude modulation (M-QAM) constellations with nonuniform a priori probabilities. However, shaped constellations may have a detrimental impact on the chain of digital signal processing algorithms of typical coherent receivers, reducing or even eliminating the expected shaping gains. In this article, we evaluate carrier phase recovery (CPR) and carrier frequency recovery (CFR) algorithms for probabilistically shaped transmission. The results are obtained by offline processing of experimental data with laser imperfections and additive noise loading. We investigate an existing two-stage CPR, where the first stage is based on pilots with 3.1% overhead, and the second stage uses the blind phase search (BPS) algorithm. We showthat the BPS stage is severely impaired by PS at moderate and low SNRs. These impairments can be partially compensated using extremely long noise rejection windows, which may be undesirable from a computational complexity standpoint. Conversely, using only the pilot-based stage exhibits penalties at high SNRs, as phase noise dominates over additive noise. In order to obtain a suitable performance over the full range of SNRs, we propose to detune the PS factor (with respect to the AWGN-optimized value) to optimize the BPS stage. In scenarios with relatively low phase noise and low modulation orders, we show that an equivalent performance can be obtained without shaping factor detuning by operating with the two-stage approach at high SNRs and switching off the BPS stage at moderate and lowSNRs. We also showthat typical blindCFRbased on the 4th power algorithm is severely affected by PS at moderate block lengths, but its expected performance can be recovered using very long block lengths. Alternatively, a pilot-based algorithm with 3.1% overhead (employing the same pilots used for the first stage of the two-stage CPR algorithm) achieves a suitable performance in all the investigated scenarios. (AU)

FAPESP's process: 18/14026-5 - Design and optimization of submarine optical links using space-division multiplexing
Grantee:Darli Augusto de Arruda Mello
Support type: Scholarships abroad - Research
FAPESP's process: 15/24341-7 - New strategies to confront with the threat of capacity exhaustion
Grantee:Helio Waldman
Support type: Research Projects - Thematic Grants
FAPESP's process: 15/24517-8 - Photonics for next generation internet
Grantee:Hugo Enrique Hernández Figueroa
Support type: Research Projects - Thematic Grants