Digital Nonlinearity Compensation Techniques for Unrepeatered Optical Systems

In this paper, we experimentally investigate the performance of unrepeatered optical transmission comparing different nonlinear compensation (NLC) implementations. Specifically, digital back-propagation (DBP) algorithm and maximum likelihood sequence estimation (MLSE) are applied for intra-channel NLC with and without 4x4 multiple-input multiple-output (MIMO) equalization. Both NLC algorithms are evaluated in an unrepeatered WDM transmission of 17x200-Gb/s channels (32 GBd DP-16QAM) over 350 km of large effective area and low loss single-mode fibers. The results indicate a Q^2 factor and optimum launch power improvements of up to 0.4 dB and 2 dB, respectively, compared to the linear compensation (LC), combining MLSE and DBP with MIMO equalization.