Spatially multiplexed picosecond pulse-train generations through simultaneous intra-modal four wave mixing and inter-modal cross-phase modulation

We report on the experimental generation of spatially multiplexed picosecond 40 GHz pulse trains at telecommunication wavelengths by simultaneous intra-modal multiple four wave mixing and inter-modal cross-phase modulation in km-long bi-modal and 6-LP-mode graded-index few-mode fibers. More precisely, an initial beat-signal injected into the fundamental mode is first nonlinearly compressed into well-separated pulses by means of an intra-modal multiple four-wave mixing process, while several group-velocity matched continuous-wave probe signals are injected into higher-order modes in such a way to develop similar pulsed profile thanks to an inter-modal cross-phase modulation interaction. Specifically, by simultaneously exciting three higher-order modes (LP₁₁, LP₀₂ and LP₃₁) of a 6-LP-mode fiber along group-velocity matched wavelengths with the fundamental mode, four spatially multiplexed 40 GHz picosecond pulse-trains are generated at selective wavelengths with negligible cross-talks between all the modes.