Nonlinear propagation in multi-mode fibers in the strong coupling regime
  In spite of the massive interest that the generalized Manakov equation has attracted in the past two decades, no physical system which is quantitatively described by this equation has been reported so far. In this paper we show that propagation in a group of degenerate modes of a multi-mode optical fiber satisfies this equation in the presence of random mode coupling. Consequently, this is the first reported physical system that admits true multi-component soliton solutions. The reported formalism constitutes the starting point for future studies of nonlinear effects in multi-mode fiber transmission. 
Antonio Mecozzi, Cristian Antonelli, and Mark Shtaif
physics.optics nlin.PS