Fiber-Optic Temperature Sensor Based on Difference of Thermal Expansion Coefficient Between Fused Silica and Metallic Materials

In this paper, we report a novel fiber-optic Fabry-Perot interferometric (FFPI) temperature sensor based on the difference of thermal expansion coefficient between fused silica and metallic materials. The sensor head is made by a single-mode fiber (SMF). A gold film and a nickel film are sputtered and electroplated on the surface of the SMF. Then, a microcavity is micromachined by focused ion beam (FIB) milling. Because the thermal expansion coefficient of nickel is about 20 times of fused silica, the different thermal expansions force the sensor head to bend when the temperature is high or low. Its temperature sensitivity is over 14 pm/°C in a wide range from -79°C to +70°C. And the coefficient of determination R² is excellent (over 0.995). Moreover, the metallic cylinder can reinforce the cavity spot of the fiber sensor, so that this kind of sensor can work in harsh environments. For the first time to the best of our knowledge, we report this type of FFPI temperature sensor based on difference of thermal expansion coefficient between fused silica and metallic materials.