Soliton trapping in multimode fibers with random mode coupling
  We derive the fundamental equations describing nonlinear propagation in multi-mode fibers in the presence of random mode coupling within quasi-degenerate groups of modes. Our result generalizes the Manakov equation describing mode coupling between polarizations in single-mode fibers. Nonlinear compensation of the modal dispersion is predicted and tested via computer simulations. 
Antonio Mecozzi, Cristian Antonelli, and Mark Shtaif
physics.optics nlin.PS