Spatiotemporal nonlinear dynamics in multimode fibers

Nonlinear mode coupling in multimode optical fibers leads to complex self-organization phenomena. These are associated with the emergence of extreme waves, in the form of stable nonlinear coherent attractors characterized by low-order transverse mode patterns. The periodic or quasi-periodic oscillations of the multimode beam intensity due to mode beating lead to light scattering into a series of spectral sidebands spanning multiple octaves. We overview recent theory and experiments of complex spatiotemporal nonlinear beam reshaping phenomena in both passive and active multimode optical fiber systems.