This paper reviews and extends the study of nonlinear performance of few-mode fiber links operating in all different linear coupling regimes for different mode delay maps. Nonlinear performance was estimated using the four-wave-mixing theory and the split-step Fourier method including semi-analytical solutions for linear mode coupling of arbitrary strength. The optimum link configurations minimizing the nonlinear penalty at practical levels of training sequence length are presented, including: the required coupling strength to give nonlinear distortion below that of the single-mode propagation without mode coupling, and the impact of mode delay maps. Finally, different approximate solution methods of the multimode nonlinear Schr-dinger equation are compared, highlighting the accuracy of a stochastic solution method including distributed linear mode coupling.
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Funding: This work has been partially supported by the European Union
(Grants 654809-HSPACE, and 659950-INVENTION), and by the EPSRC
(Grant EP/L000091/1-PEACE and EP/R024057/1-FPA-ROCS)
- Few-mode fiber
- fiber nonlinearity
- linear mode coupling
- mode-division multiplexing