Dual-Carrier-Assisted Phase Retrieval for Polarization Division Multiplexing

Abstract

Phase retrieval (PR) schemes based on modified Gerchberg-Saxton (GS) algorithm using pilot symbol or pilot tone have recently attracted great attentions in self-coherent systems. In this work, we propose a dual-carrier-assisted phase retrieval (D-CAPR) algorithm and further fulfill a dual-polarization carrier-assisted PR (DP-CAPR) scheme. The polarization diversity is realized by transmitting a polarization-division-multiplexed (PDM) signal with orthogonal offset carriers, and the dual-polarization optical fields are recovered by the proposed D-CAPR algorithm. The D-CAPR scheme is able to directly retrieve the phases of optical field given the prior phase information of two carriers on each polarization without the use of any frequency guard band. We numerically characterize the performance of proposed DP-CAPR and experimentally demonstrate it for 30 GBaud dual-polarization-32-ary quadrature amplitude modulation (DP-32-QAM) transmission over 80 km single-mode fiber. The impacts of polarization rotation, polarization mode dispersion, and electrical noise on DP-CAPR have been investigated. Moreover, we compare the electrical bandwidth requirement, optical signal-to-noise ratio (OSNR) sensitivity, and hardware complexity of the DP-CAPR scheme with previously reported DP field recovery schemes.