Demonstration of Mode-Switching in a Few-Mode Fiber Using Electric Field Controlled Dynamic Off-Set Coupling

We experimentally demonstrate the switching between different linearly polarized modes in a few-mode fiber using electric field-controlled fiber-to-fiber dynamic off-set coupling. In this work, a single-mode fiber based cantilever beam-deflection transducer is devised with its suspended free end coated with electrostrictive nanocomposite film, as the coupling source. In experiment, precise launching conditions governing the excitation of modes and intermodal switching are minutely controlled by applied electric field. By modelling the offset coupling geometry, the estimated experimental launching conditions are seen to match very well with those obtained from mode solutions, clearly establishing the significance of the approach. Also, the experimentally procured intensity profiles for different cases are theoretically mapped with the relevant linearly polarized modes with appropriate excitation coefficients. The study provides a useful insight of selective mode excitation and also a guideline to designing electric field controlled automated mode switching device.