Interference-Type High-Sensitivity Temperature Sensor Based on the Photosensitive Fiber Microsphere

A high sensitive temperature sensor based on photosensitive optical fiber is proposed in order to detect the special environment temperature in real time. After cutting the end faces of a single-mode fiber and a photosensitive fiber (PF) into flat, put them into a fiber fusion machine for manual discharging. Because of the tension effect of the fiber surface, an optical fiber end face will be fused into an optical fiber microsphere at the moment of discharging, and then two optical fiber microspheres will be fused into an optical fiber peanut structure through manual discharging. The optical fiber peanut structure has the same functions as fiber beam splitter and combiner in an interferometer. Considering that the refractive index of the core and cladding of the PF is different, result in the difference of optical paths propagating between in the core and in the cladding, which causes that the interference will occur when the two beams are coupled. While boron and germanium are doped in the core of the PF, the thermo-optical coefficient and thermal expansion coefficient of the core increase. When the ambient temperature changes, the interference spectrum will drift. Experimental results show that, in the temperature range of 45 degrees C-65 degrees C, the sensor sensitivity is -386.96 pm/degrees C, and the linear fitting degree is 99.76%. The sensor has the advantages of high sensitivity, fast response and simple fabrication process. In addition, it has a certain application prospect in marine environmental measurement and in other fields.