High-Temperature Fiber Optic Sensor Using a Grating on an Angled Fiber Tip

Abstract

In order to achieve a more stable fiber-optic temperature sensor in a high temperature range, a grating was produced by lithography and dry etching on the 45° angled fiber tip to diffract a portion of the incident light back to the fiber axis and to interfere with the light which is totally reflected from the angled fiber tip. The performance was investigated in the range of the room temperature to 1100°C for s- and p-polarized input beams and then analyzed by the parameter estimation technique. The result shows that the variation of signal intensity is dependent on the input polarization state and that the phase change from the thermo-optic and thermal expansion coefficients must be treated as a linear function of temperature.