Observing in Single-Shot the Space-Time Dynamics of Soliton Collision with a Recirculating Fiber Loop

Solitons in optical fibers are pulses of light that propagate indefinitely while retaining their shape as a result of a perfect balance between dispersion and nonlinearity. Since the prediction of their existence 50 years ago [1], they have been the subject of an incredible amount of studies driven both by their applicative potential and fundamental interest in the domain of nonlinear waves. Almost concomitantly with this prediction, Zakharov and Shabat developed the theoretical framework that enables description of the propagation of such solitons by solving exactly the focusing one-dimensional nonlinear Schrödinger equation [2]. One of the remarkable result of this so-called inverse scattering transform is the fact that solitons “collide” ellastically which means that they emerge after their interaction completely unaltered except for position shifts that are solely determined by their amplitude and relative velocities. Propagation and interaction of solitonic pulses have been realised in optical fiber experiments under very diverse configurations [3], [4] but the observations are in most cases indirect or do not illustrate the full extent of notable features of soliton collision.