Compact Tri-FFPI sensor for measurement of ultrahigh temperature, vibration acceleration, and strain

As a high-precision fiber optic sensor, a single optical fiber Fabry Pérot interferometer (FFPI) sensor is often used to measure parameters such as temperature or strain. However, the use of combined FFPIs to measure multiple parameters simultaneously has rarely been reported. In this paper, a compact Tri-FFPI sensor consisting of three series-connected FFPIs is proposed to measure high temperature, high acceleration, and large strain. The total length and diameter of the sensing part are only 2558.9 µm and 250 µm, respectively. One of the FFPIs, FFPI-1, contains a cantilever beam structure to measure vibration acceleration. FFPI-2 is used to measure temperature and the temperature compensation of the strain measurement. FFPI-3 is used to measure strain. To ensure that the sensor has high measurement sensitivity, two demodulation methods are used: the light intensity demodulation method for vibration acceleration and the wavelength demodulation method for temperature and strain. The sensor is capable of withstanding ultrahigh temperatures up to 1000°C.