Fiber-optic refractive index sensor based on cladding-mode resonance

Abstract

A fiber-optic refractive index (RI) sensor is proposed based on a double-cladding special fiber. The double-cladding fiber (DCF) consists of core, inner cladding and outer cladding. And refractive index of core and outer cladding is higher than that of inner cladding. Through evanescent wave coupling, cladding mode can be excited resonantly at phase-matched wavelength. Because the cladding mode transmission is sensitive to ambient refractive index variation, the DCF can be used to solution refractive index sensor. By splicing a section DCF into standard single mode fiber (SMF), SMF-DCFSMF sensor was constructed and studied for refractive index sensing. A resonant wavelength shift of 65nm was achieved by changing ambient refractive index within the range of 1~1.4525.