“…1 in our experiment, the two pumps, P 1 and P 2 , were launched into the fundamental TE00 mode, while the signal and the generated idlers were in the first order, TE10, mode. A cartoon of the operational principle of how to achieve phase matched inter-modal FWM for the I BS,r or I BS,b , respectively, is illustrated in Fig.2 [13], [12], [18], [19], where the inverse group velocity (v −1 g ) curves of the modes supported in a multi-mode waveguide are shown as a function of wavelength. Phase matching is satisfied when the following equation is (almost) fulfilled:…”