Demonstration of Broadband Inter-Modal Four-Wave Mixing in Graded-Index Few-Mode Fibers

We experimentally demonstrate broadband four-wave mixing (FWM) between two spatial modes of a 5-km-long few-mode fiber. We show that, in contrast to FWM in single-mode fibers, intermodal FWM (IM-FWM) can be better phase matched for waves well separated in frequency (a few THz) than when they are closely spaced (tens of GHz). The large values of chromatic dispersion in each spatial mode did not suppress IM-FWM.