Asymmetrical twin-core fiber based Michelson interferometer for environmental refractive index sensing

We presented a type of refractive index sensor based on Michelson interferometer by using asymmetrical twin-core fiber. The central-core and side-core of the asymmetrical twin-core fiber are used as the reference arm and sensor arm respectively, and the D-shape side-polish sensing region are fabricated on the sensing arm by the side-polishing technique. The optical path difference is formed between the two arms due to the sensing region of the side-core sensitive to the change of the surrounding refractive index. Thus, through the reflection of the end and taper of the fiber to achieve the interference of transmission to form Michelson interferometer. Therefore, the changes of the surrounding will lead to the shift of the transmission spectrum to reach the purpose of the sensing. The experimental results show that the device has a maximum refractive index sensitivity of about -80nm/RIU in the range of 1.333-1.3824 and the result is basically consistent with the simulation. This sensor is a simple structure and convenient in its production advantages, and can be used in many areas such as biological sensing and chemical sensing.