A high stability microfiber Sagnac loop refractive index sensor

A Sagnac loop liquid refractive index sensor is proposed based on SMF-Tapered TCF-SMF (STS) and FBG. In the refractive index range of 1.333-1.3465 and 1.3515-1.363, the sensitivity is 5521.6nm/RIU and 7173.8nm/RIU, respectively. By cascading FBG, the random fluctuation of wavelength is reduced from±0.862nm to 0.004nm. It can effectively filter out part of the cladding mode and improve the stability of the sensor.