We demonstrate an intermodal Cerenkov radiation effect in a higher-order-mode (HOM) fiber with a mode crossing (i.e., two guided modes having the same propagation constant at the same wavelength). A frequency-shifted soliton in the vicinity of the mode-crossing wavelength emits a phase-matched dispersive wave in a different propagation mode. We develop a theoretical explanation for this nonlinear optical effect and demonstrate that the mode crossing in HOM fibers can be utilized to achieve simultaneous wavelength and mode conversion; the strength of this inter-modal nonlinear interaction can be tuned by controlled fiber bending.
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