Cascaded Fabry-Perot cavity and fiber Bragg grating on sapphire fibers for high-temperature strain sensing

High-temperature strain sensors are key elements for several applications. Key issues of the existing devices include the difficulties of sensor operating above 1000°C as well as the very strong thermal effect under high temperatures introducing significant bias on the strain measurement. Here we developed a cascaded Fabry-Perot cavity and fiber Bragg grating strain sensor fully integrated on sapphire fibers, permitting a sufficient temperature compensation and strain measurement up to 1150°C temperature. A three-point adhesive bonding process is proposed to greatly improve the adhesion performance, and hence the robustness of the device at high temperatures. Experimental results show that the fabricated strain sensor can achieve a measurement range of ±1000 με at temperature up to 1150°C. The experimental results show that the measurement accuracy is not more than 5% at room temperature. the measurement accuracy is significantly decreased at high temperature, and the maximum strain measurement error is 14% at 1150°C.