Residual Carrier-Based Inter-Channel Nonlinearity Compensation for WDM NFDM Systems

Abstract

Nonlinear frequency division multiplexing (NFDM) exploits the nonlinear Fourier transform (NFT) to modulate signals in the nonlinear spectral domain, where intra-channel Kerr nonlinear distortion can be mitigated. However, inter-channel nonlinear interference remains a major limitation in wavelength division multiplexed (WDM) NFDM systems based on linear optical multiplexing. In this work, we propose a residual carrier-based inter-channel nonlinearity compensation method for WDM NFDM systems. A residual optical carrier with a narrow guard band is embedded in each channel as a nonlinear phase probe and extracted to compensate for inter-channel nonlinear phase distortion using only single-channel information. In an $8\lambda \times 32$ -GBd 36-QAM WDM NFDM experimental system over 960-km standard single-mode fiber (SSMF), the method achieves 0.66-dB Q2-factor improvement and 50% reach extension. The results show improved launch-power tolerance and verify the effectiveness under different extraction bandwidths and channel spacings.