In-line higher order mode filters based on long highly uniform fiber tapers

This paper presents a simple and effective design of taper-based higher order mode (HOM) filters that can effectively remove HOMs from the few-mode fibers. For this purpose, a taper manufacturing technique that allows the production of long and highly uniform tapers was developed. A filter performance was demonstrated on a standard single-mode telecommunication fiber operating at 850 nm. The HOM suppression was better than -39 dB, and the insertion loss of the fundamental mode was less than 0.15 dB.