Optical directional coupler using tapered sections in multimode fibers

Abstract

An optical directional coupler with high efficiency has been fabricated using tapered sections in multimode fibers. In the biconical taper sections of the coupler, some of the higher‐order modes are converted into radiation modes launched into a clear adhesive and subsequently reconverted into guided modes of two arms of the coupler. The insertion loss, power coupling, and directivity were measured to be 1.0, 10.2, and 20 dB, respectively.