Abstract

We demonstrate a mid-infrared compatible tunable bandpass filter that consists of a singlemode-multimode-singlemode fiber structure, made from chalcogenide fibers. Experiments have been carried out using step-index multimode fibers with small core radius, resulting in a continuous wavelength tunability >52 nm and a hop wavelength tunability of 84 nm, via mechanical bending. Core to core lateral offsets at input and output interfaces between singlemode fibers and multimode fiber are optimized to maximize the extinction ratio and set a desired transmission wavelength. Transmission characteristics of the multimode interference effect and design rules of a widely tunable filter are also presented.

Tunable multimode-interference bandpass fiber filter

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