U-Shaped High-Sensitivity Sensor Based on Tapered Single-Mode Fiber for Simultaneous Displacement and Temperature Measurement

A U-shaped displacement and temperature sensor based on tapered single-mode fiber (TSMF) is proposed. The sensor is fabricated by bending the TSMF into a U-shape to excite higher-order modes, thereby forming a Mach-Zehnder interferometer. Through simulation and analysis of the transmission spectrum of the U-shaped sensor, obtain the suitable U-shaped bending radius and waist diameter. When the waist diameter of the TSMF is 40 μm and the bending radius of the U-shape is 1355 μm, the sensor exhibits two interference dips. By monitoring the wavelength shifts of two interference dips, simultaneous measurement of displacement and temperature is achieved. The experimental results show that the U-shaped sensor achieves high displacement sensitivity of 1.367 and 2.771 nm/μm in the 0-50 μm displacement range, respectively. Besides, the sensor achieves temperature sensitivities of 20.71 and 31.43 pm/°C in the range of 30-90 °C, respectively. The proposed U-shaped sensor has the advantages of compact structure, simple preparation, and high sensitivity, making it an ideal candidate for the future simultaneous measurement of displacement and temperature in structural health monitoring.