Optical solitons in graded-index multimode fiber

Solitons are non-dispersing localized waves that occur in diverse physical settings. A variety of optical solitons have been observed, but versions that involve both spatial and temporal degrees of freedom are rare. Optical fibers designed to support multiple transverse modes offer opportunities to study wave propagation in a setting that is intermediate between single-mode fiber and free-space propagation. Here we report the observation of optical solitons and soliton self-frequency shifting in graded-index multimode fiber. These wave packets can be modeled as multi-component solitons, or as solitons of the Gross-Pitaevskii equation. Solitons in graded-index fibers should enable increased data rates in low-cost telecommunications systems, are pertinent to space-division multiplexing, and can offer a new route to mode-area scaling for high-power lasers and transmission.