Random mode coupling assists kerr beam self-cleaning in a graded-index multimode optical fiber

Spatiotemporal light beam dynamics in multimode fibers (MMF) recently has attracted renewed interest in both fundamental physics and various fields of practical application . Recent experiments have shown that, owing to the Kerr effect, a process of beam self-cleaning can be observed in graded-index (GRIN) MMFs. As a result, one observes a robust nonlinear beam, which has a size that is close to the fundamental mode at the fiber output, in contrast to a speckled output beam, which is obtained in the case of the linear regime.