Performance analysis of WDM-SDM system with employing Phase-Conjugated twin waves technique

Abstract

In this paper, the phase conjugated twin waves (PCTWs) technique is proposed to reduce the nonlinear phase noise in wavelength division multiplexing (WDM) - spatially division multiplexing (SDM) system. In the proposed system, the m-ary quadrature amplitude modulation (mQAM) signals are generated and multiplexed to produce mQAM WDM signal. Similarly, the second WDM signal is created by multiplexing the phase conjugated copies of the mQAM signals and then they are spatially multiplexed by two fiber links. At receiver, they are firstly demultiplexed and then superimposed coherently to revoke the nonlinear phase noise and improve the signal to noise ratio (SNR). Moreover, the analytical model that best describes the phase noise alleviation is developed. Analytical results show that the proposed scheme significantly reduces the variance of the phase noise. Furthermore, to show the effectiveness of proposed scheme, 16-channel 4QAM WDM-SDM system with and without PCTWs method is numerically investigated. Numerical results reveal that the PCTWs scheme enhances the SNR of the received signal by more than 2.7 dB and extends the achievable transmission distance by 39.4% at 10 −5 bit error rate (BER).