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Hardware optimization of dual-stage carrier-phase recovery for coherent optical receivers

Martins, C. M. ; Guiomar, F. P. ; Pinto, A. N.

OSA Continuum Vol. 4, Nº 12, pp. 3157 - 3157, December, 2021.

ISSN (print): 2578-7519
ISSN (online):

Scimago Journal Ranking: 0,59 (in 2020)

Digital Object Identifier: 10.1364/OSAC.438524

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We present an optimized dual-stage CPR method based on pilot symbols and a blind phase search algorithm (BPS) for M-QAM coherent optical transmission systems, targeting an efficient hardware implementation. A comprehensive optimization of the key CPR parameters is performed, including, pilot-rate, number of test phases, angle interval and moving average filter size. The optimization process is validated through numerical assessment of the optical communication system performance using 16-QAM, 64-QAM, and 256-QAM modulation formats at 64 GBaud. The optimized dual-stage CPR is demonstrated to operate with a very low number of test phases in the second stage BPS algorithm. In addition, it supports more than 10× higher laser linewidth than the standard CPR based on pilot symbols. Besides, a reduction of more than 90%, in terms of hardware complexity is achieved with respect to the standalone application of the BPS algorithm. The optimized dual-stage CPR is also validated through hardware implementation based on VHDL, and its gate-level complexity is assessed for a commercial off-the-shelf Xilinx Virtex-7 FPGA.