Influence of equalization enhanced phase noise on digital nonlinearity compensation in Nyquist-spaced superchannel transmission systems

Abstract

In digital signal processing (DSP) based coherent optical communication systems, the effect of equalization enhanced phase noise (EEPN) will seriously degrade the transmission performance of high-capacity optical transmission system. In this paper, we have investigated the influence of EEPN on 9-channel 32-Gbaud dual-polarization 64-ary quadrature amplitude modulation (DP-64QAM) Nyquist-spaced superchannel optical field trial by using electronic dispersion compensation (EDC) and multi-channel digital backpropagation (MC-DBP). The deteriorations caused by EEPN on the signal-to-noise-ratio (SNR) and achievable information rates (AIRs) in high-speed optical communication systems have been studied. The system performance versus back-propagated bandwidth under different laser linewidth have also been demonstrated. The SNR penalty due to the distortion of EEPN achieves ~5.11 dB when FF-DBP is implemented, which informs that FF-DBP is more susceptible to EEPN, especially when the LO laser linewidth is larger. The system AIR versus different transmission distance under different EEPN interference using EDC-only and MC-DBP have also been evaluated, which show that there is a trade-off on the selection of lasers and back-propagated bandwidths to achieve a target AIR.