Modified Huber ICA-based frequency domain channel equalizer for polarization division multiplexing coherent optical OFDM systems

Abstract

Polarization division multiplexing coherent optical OFDM (PDM-CO-OFDM) is an approach which ensures reaching high data rates by enabling the utilization of the amplitude, phase and polarization of light at the same time in long-haul transmissions. The channel equalizer is used for the compensation of the linear and nonlinear effects of fiber in the optical receiver, and channel estimation is realized with periodic training symbols. In this study, a channel equalizer based on modified Huber independent component analysis (MHICA) without training symbols (TS) was proposed for the PDM-CO-OFDM systems. Thus, the mathematical model of the PDM-CO-OFDM system and MHICA were analyzed. It is shown in the simulations that the proposed channel equalizer in the receiver can compensate for the linear and nonlinear effects in the optical channel and successfully recover the OFDM signals. In addition, compared to other ICA-based channel equalizers, the proposed channel equalizer is the fastest, and provides slightly improved or similar performance for QPSK and 16-QAM modulated signals respectively. Under the same conditions, the proposed channel equalizer achieves better performance than conventional TS-based frequency domain channel equalizers, both with and without intersymbol frequency-domain averaging (ISFA). © 2019 Elsevier GmbH