Fiber-optic refractive index sensor based on tapered thin core fiber

In this paper, we propose the design of fiber optic refractive index sensor based on a thin core fiber, sandwiched between an input and output single mode fibers. This structure is characterized by a refractive index sensitivity about 187.98 nm/RIU (refractive index unit). In order to enhance the sensitivity, we designed a tapered single mode-thin core-single mode fiber structure where the sensitivity with different waist-diameters (90, 60 and 30 mu m) is investigated. As a result, we obtained an ultra-high sensitivity of the tapered sensor about 783.19 nm/RIU in the refractive index range of 1.3346-1.3899, using sucrose and water mixture solution, achieved for a waist diameter equal to 30 mu m and a taper length of 675 mu m. The designed structure presents the merits of high sensitivity which is 4 times higher than that of the thin core fiber modal interferometer which makes it an excellent candidate for biochemical sensing applications.