Wavelength demultiplexing using bends in a single-mode optical fiber

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Abstract
A method of wavelength demultiplexing is developed that makes use of the wavelength and bend-radius dependence of the pure bend loss at single radius bends in a single-mode fiber. The light leaving the fiber at a bend forms one output of the demultiplexer. Equations are derived that predict the bend radii for the most-efficient operation of the demultiplexer and the power extracted from the fiber at each wavelength. The demultiplexer operates over the wavelength range corresponding to V numbers from 2.4 to 1.6. A two-wavelength demultiplexer formed from 90 degrees bends is constructed and tested. Collection efficiencies of 70% and insertion losses of less than 2 dB are shown to be possible. Crosstalk isolation in excess of 40 dB can be achieved with the aid of optical wavelength filters. The performance of a three-wavelength demultiplexer is also considered.