All-optical switch based on beam cross-cleaning effect in graded-index multimode fiber

We introduce the concept of beam all-optical spatial beam switching in graded-index multimode fibers. This consists of seeding a bell-shaped spatial profile to a laser beam at the output of the fiber by exploiting the nonlinear coupling between the modes of the two input beams. Remarkably, we demonstrate that even a weak-control signal allows for improving the spatial profile of a highly multimode intense signal. The device proposed herein will be easily integrated in state-of-the-art optical networks, and will find application in the fields of space-division-multiplexed telecommunication and of multimode fiber lasers.