Optical fiber liquid refractive index sensor based on Fresnel reflection of anti-Stokes light

An optical fiber liquid refractive index (RI) sensing method based on Fresnel reflection of Raman anti-Stokes light is firstly proposed and demonstrated. A specially fabricated sensor head formed by a fiber end and a fiber coil is designed, and they are used to sense RI and temperature respectively. Experimental results show that the sensor has a RI resolution up to 0.0002 RIU (Refractive Index Unit) and a temperature accuracy of ±1 °C within a measurement range of 10 km. The performance confirms that the sensor has potential to act as a remote refractometer and thermometer. Its case of simple fabrication of using only one multimode fiber offers attractive remote RI and temperature sensing applications involving chemical and biological fields.