Temperature Measurement by the Shift of Interference Bands in a Fabry–Perot Microinterferometer Based on a Silicon Plate

A fiber-optic temperature sensor with a sensitive element based on a silicon Fabry–Perot microinterferometer, the temperature of which is measured by the shift of interference fringes due to the dependence of the refractive index of silicon on temperature, is described. The Fabry–Perot interferometer is a silicon plate with dimensions 500 × 500 µm2 and thickness 20 µm located at the end of a single-mode fiber. The conversion coefficient of such a Fabry-Perot interferometer is approximately 1 nW/°C, which, when using modern balanced photodetectors, provides the sensitivity of the order of 5 × 10–3°C.