Efficient higher-order mode filtering in multimode optical fiber based on an optical microwire

We report the use of an optical microwire (OMW) with specifically designed transition region as an efficient tool to filter higher-order modes in multimode waveguides. Higher-order modes are effectively suppressed by controlling the transition taper profile and the diameter of the optical microwire. As a practical example, single-mode operation of a standard telecom optical fiber over a broad spectral window (400 ~ 1700 nm) was demonstrated with a 1 mum OMW.