Improving the efficiency of frequency domain channel estimation in 16-QAM polarization division multiplexing coherent optical OFDM systems using complex fixed-point ICA

Abstract

Polarization division multiplexing coherent optical OFDM (PDM-CO-OFDM) systems are a method that provides to be achieved high data rate, offering the possibility for the use of information regarding polarization, amplitude and phase simultaneously. However, the impairment affects related to optic channel decrease the data transmission performance. For this reason, in the receiver, the channel equalizer, one of the signal processing techniques, are used for the impairments in order to compensate. Even though the periodic training symbols are generally used for the estimating of channel information in the channel equalizers, the use of training symbols increase system redundancy and decrease spectral efficiency. In this study, a blind channel equalizer based on complex fixed-point ICA without training symbols is suggested for the PDM-CO-OFDM systems with 16-QAM signals. The results show that the complex fixed-point ICA algorithm improves the performance of channel equalizer without the training symbols. This situation is indicated by the BER values of the signals obtained according to the change of the launch power values and optical signal noise ratio (OSNR) values. Simulation results have shown that the suggested channel equalizer has better performance than other channel equalizers, especially in the region where the effect of the fiber nonlinearity is effective.