An intermodal switch based on optically induced (through the Kerr effect) periodic coupling in a two-mode waveguide is described and demonstrated. A high-power pump beam injected into the two modes of the waveguide produces a periodic modulation of the refractive-index profile with a period equal to the modal beat length, which causes coupling between the two modes of a simultaneously injected probe beam. The operating principle was successfully demonstrated in an elliptical-core two-mode fiber

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... with counterpropagating pump and probe beams. All-optical switching devices utilizing waveguides are of current interest for use in high-speed optical signal-