Origin Of Spontaneous Wave Mixing Processes In Multimode Grin Fibers

We show that geometric parametric instability (GPI) in graded-index multimode fibers is strongly influenced by higher-order dispersion. By measuring the output spectrum for different core radii, we distinguish peaks generated by GPI from other coexisting parametric processes using phase-matching arguments and numerical simulations. We highlight for the first time a non-degenerate GPI process involving two pumps at different wavelengths. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement