A Novel Compensation Method for FWM Impairments Based on Cancellation by Estimated Components in Digital Coherent Detection

We propose a novel four-wave mixing (FWM) impairments compensation method based on cancellation by means of estimated FWM components. Digital coherent detection can compensate for fiber transmission degradation, including fiber nonlinearity impairments. However, in the backward propagation (BP) method, the out-of-band FWM components must be detected. With our proposed method, only the transmitted signal channels need to be detected. The compensation results indicate that the input optical power tolerance is improved by nearly 4 dB at 1-dB eye penalty. The compensation possibility is demonstrated experimentally in a three-channel wavelength-division-multiplexing (WDM) system with differential phase-shift keying (DPSK) modulation and digital coherent detection. The eye penalty of each signal is improved by more than 3 dB with P₀=8 dBm. This compensation method is also effective in multichannel systems.