Digital compensation of imperfect pump counter-phasing induced phase distortion in optical phase conjugation of high-order QAM.

Tu T Nguyen,Ryuichi Sugizaki,Shigehiro Takasaka,Abdallah A I Ali,Sonia Boscolo,Stylianos Sygletos,Andrew D Ellis

doi:10.1364/oe.418386

Tu T Nguyen, Ryuichi Sugizaki + Show 5 more

Open Access

https://doi.org/10.1364/oe.418386

Copy DOI

Abstract

We propose a new two-stage digital signal processing scheme to suppress the phase distortion that arises from imperfect pump counter-phasing in a dual-pump fibre-based optical phase conjugation system. We demonstrate experimentally and numerically a signal-to-noise ratio improvement of more than 4 dB relative to conventional phase noise compensation, when the proposed scheme is used with 16/64/256 quadrature-amplitude modulation signals at pump-phase mismatch values as large as 8°.

Highlights

Optical phase conjugation (OPC) is gaining increasing attention as an all-optical technique that can enable the simultaneous compensation of chromatic dispersion and fibre Kerr nonlinearity induced distortions in optical communication systems through mid-span spectral inversion [1,2]
We develop a new method for compensating the phase distortion caused by deviations from ideal counter-phasing of the pumps in the OPC of high-order quadrature-amplitude modulation (QAM) signals, which we implement using a two-stage design
To evaluate the effectiveness of the proposed two-stage phase noise (PN) compensation scheme, we set the OPC transceiver to operate at an optical signal-to-noise ratio (SNR) of ∼ 36 dB under optimum pump counter-phasing, achieving an optimum effective SNR after digital signal processing (DSP) of ∼ 20-21 dB

Summary

Introduction

Optical phase conjugation (OPC) is gaining increasing attention as an all-optical technique that can enable the simultaneous compensation of chromatic dispersion and fibre Kerr nonlinearity induced distortions in optical communication systems through mid-span spectral inversion [1,2]. Typical waveforms demonstrated for pump dithering include combinations of well-chosen sinusoidal tones [5], pseudorandom binary sequences [6] and white noise, where the first phase modulation format is the most commonly used in practice as it enables control of the details of the laser spectrum. This approach itself is a source of problems. Small deviations from the ideal case commonly exist, and should be accounted for in the design of the optical transceivers for phase-modulated communication systems deploying OPC

Methods

Results

Conclusion