High sensitivity refractive index sensor based on the semicircular bent fiber

A refractive index sensor based on a semicircular bent fiber is presented. The interference occurs between the cladding mode excited in the bending region and the core mode. Both the theoretical and experimental results show that the resonant dip wavelength decreases linearly with the increase of the refractive index of the surrounding environment. A high sensitivity of 1031 nm per refractive index unit is obtained over the refractive index range of 1.3324 to 1.3435 by using a bent fiber with a bending radius of 500 {\mu}m.