Investigation Of Fiber Optic Refractive Index Sensor Based On Single-mode Fiber Core-Offset

With many unique advantages compared to traditional sensors, optical fiber sensors have been studied and applied to many different areas. Interferometric sensors are one of the most useful sensor types due to their high sensitivities and relatively relaxed requirement on the stability of the optical source’s power level. Optical sensors based on the principle of Michelson interferometer are one of the most popular sensor types due to their simple-structure and measurement facilities. Fiber refractive index sensors have so many available applications extremely in the field of biology, chemistry, medicine and so on.Based on the principle of Michelson interferometer, a new kind of optical sensor is developed. We call it single-mode core-offset optical sensor which couple light from core to cladding to replace LPG. We get the relationship between surrounding RI and cladding’s effective RI with BPM. The coupling coefficients between core and cladding modes are calculated by it too. The results show that the effective RI of the cladding mode increases while the surrounding RI increasing and the effective RI of the core mode stays almost at constant; each mode’s coupling efficiency changes gradually and finally reaches a fixed value with the increasing of core-offset distance. The characteristic wavelength will shift to short wavelength direction when the surrounding RI increases.The experiment results include three parts:the result of sugar solution’s RI, the result of aqueous solution after temperature compensation and the result of high temperature. The result fit well with theoretical analysis, Experimental results show that there will be an increasing relationship between characteristic wavelength and temperature. There will be a better decrease gradually relationship between characteristic wavelength and refractive index after temperature compensation.