Comparison of the Channel Estimation Method for Optical OFDM/OQAM Based on Three and Five Loaded Pilot Blocks

Suppressing the intrinsic imaginary interference (IMI) effect induced by multiple-path fading channel is the key technology for maintaining the good performance of the orthogonal frequency division multiplexing offset-quadrature amplitude modulation (OFDM/OQAM) systems. Recently, both theoretical studies and experimental demonstrations for coherent optical OFDM/OQAM (CO-OFDM/OQAM) system has been studied. A number of works have been conducted to provide effective channel estimation for CO-OFDM/OQAM. However, there are no theoretical discussions on optimal pilot design principles. In this paper, we discuss the system robustness against IMI for the optical OFDM/OQAM with the using of different pilot structure. The pseudo pilot was constructed with three and five consecutive loaded pilot blocks were compared for CO-OFDM/OQAM. As demonstrated in the theoretical analysis and simulation results, triangle loaded pilot blocks were sufficient to combat IMI with moderate complexity.