Mitigation of fiber non linear effects by Maximum Likelihood Sequence Detection

Maximum Likelihood Sequence Detection (MLSD) in the optical receiver has been proposed to combat the nonlinear effects in optical channels. The MLSD is typically implemented through a Viterbi algorithm. In this paper, it is shown that a low-complexity maximum likelihood sequence detector with proper metrics can achieve better results. Computational complexity grows exponentially with the length of the channel impulse response and makes it unsuitable for high data rates. To practically enable uncompensated long haul with MLSD, complexity must be minimized. While in the linear regime such a model is available and linear impairments such as chromatic dispersion and polarization-mode dispersion can be almost fully compensated by adaptive equalizers, this is not the case for nonlinear impairments, whose mitigation is essentially based on heuristic strategies. Fiber nonlinearity remains as one of the major limitations for long haul transmission.