Selective fused couplers consisting of a mismatched twin-core fiber and a standard optical fiber

This paper demonstrates a novel selective fused coupler consisting a mismatched twin-core fiber and an ordinary optical fiber. Selective coupling of over 99% has been achieved between the high NA core of the twin-core fiber and the ordinary optical fiber core with insertion loss as low as 0.04 dB. The coupler can be made easily on a standard fused coupler rig. We also studied the principle of the device. The device opens a variety of applications so far limited by the difficulty in simultaneous accessing the both cores of a mismatched twin-core fiber