Maximum-Likelihood Detection in Few-Mode Fiber Transmission With Mode-Dependent Loss

In this letter, the performance of maximum-likelihood (ML) detection is evaluated and compared with the zero-forcing (ZF) and minimum mean square error (MMSE) equalizers for a 3 $,\times,$ 158-Gb/s mode-division multiplexed dual-polarization quadrature phase shift keying orthogonal frequency division multiplexing transmission impaired by mode-dependent loss. The receiver schemes are compared in terms of performance and complexity. The simulations show that the ML approach outperforms both ZF and MMSE equalization for strongly coupled modes. However, the complexity of the ML detection is significantly higher and increases faster with the number of modes used for transmission and the modulation format order.