In this paper, we investigate the phase-conjugated twin waves (PCTWs) technique in spatially division multiplexing (SDM) system for suppressing the nonlinear phase noise. Furthermore, the analytical model that describes the phase noise suppression is developed. In the proposed system, the 20 Gsymbol/s quadrature phase shift keying (QPSK) signal and its phase-conjugated copy are spatially multiplexed through two identical optical fiber channels. At receiver, they are coherently superimposed to suppress the nonlinear phase noise and maximize the signal-to-noise ratio (SNR). The analytical results show that the phase noise variance is extremely decreased when PCTWs technique is employed. In addition, the numerical results reveal that the proposed scheme improves SNR of received signal by more than 4.5 dB and extends the achievable transmission distance by 77.8% at bit error rate (BER) of 10-5.
