Enhancement of RI Sensitivity Through Bending a Tapered-SMF-Based Balloon-Like Interferometer

An all-fiber sensitivity-enhanced refractive index (RI) balloon-like interferometer based on a tapered single-mode fiber (SMF) is proposed and experimentally investigated. The tapered fiber is designed into a balloon-like shape to form a modal interferometer which is sensitive to external environmental RI solutions. Compared with the untapered-SMF-based modal interferometer with an optimal sensitivity of 187.73 nm/RIU which also has been investigated in this paper, the tapered-SMF-based balloon-like interferometer has an improvement in RI sensitivity. Further, a serial of balloon-like interferometers based on tapered fiber with different bending radii are fabricated to explore the RI sensitivity properties on account of bending. Experimental results show that by bending the tapered-SMF-based balloon-like interferometer, the RI sensitivity has been enhanced further, and a higher sensitivity of 404.9 nm/RIU is achieved, which exhibits great potential in areas related in RI sensing.