High sensitivity temperature sensor based on side-polished optical fiber

Side-polished optical fiber has long been used to build fiber sensors and other devices. In this work, we present a particular application leading to temperature sensors operating in the 10 to 70°C temperature range. Although the temperature-induced modulation yields variations of the output optical power amplitude, high sensitivity in the order of 0.5 dB°C^-1 can be obtained (insertion loss being around 2 dB). The sensor principle combines the extreme sensitivity of polished fibers to external refractive indices, especially for those values close to the core index and the variation of the refractive index with temperature as in the case of reference liquids such as vegetable oils