Comparative performance of equalizers for linear constellation precoded coherent optical OFDM systems

Abstract

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) system has become attractive for use in the long haul optical transmission in the recent years. This paper extends the linear constellation precoding to the CO-OFDM system to form LCP-CO-OFDM system in order to combat the problem of large peak-to-average power ratio (PAPR) associated with the OFDM transmission scheme. In addition, three equalization-based algorithms, minimum mean square error (MMSE), zero forcing (ZF) and maximum likelihood (ML) algorithms are employed for the LCP-CO-OFDM system. The simulation results obtained suggest that the LCP-CO-OFDM system demonstrates superiority to the uncoded CO-OFDM system. The ML-based equalizer also shows the best performance in comparison with the two other equalizers, while ZF-based equalizer shows the worst performance in comparison with the LCP-CO-OFDM system.