Optical fiber sensor for curvature and temperature simultaneous measurement based on an anti-resonance mechanism

Based on an anti-resonance mechanism, we propose and experimentally demonstrate an optical fiber sensor for simultaneous measurement of curvature and temperature. The sensor structure consists of a hollow fiber and a twisted graded index multimode fiber spliced between two single-mode fibers. By using the twisted graded index multimode fiber to change the energy distribution of the mode field, not only improve the coupling efficiency of the sensor but also the sensitivity of the curvature measurement. The experimental results show that the intensity of the resonance peak based on the anti-resonance mechanism decreases with the increase of curvature, while the resonance peak wavelength is insensitive to curvature. In addition, due to the thermal expansion and thermo-optic effect of the fiber, the wavelength of the resonance peak is red-shifted with increasing temperature, and the intensity of the resonance peak is insensitive to temperature. Therefore, the intensity and wavelength signals of the resonance peak are monitored separately, and the simultaneous measurement of displacement and temperature is realized. The maximum sensitivity of the proposed curvature sensor can reach −2.84 dB/m−1, the dynamic range of curvature is 0 m−1 to 20.18 m−1, and the temperature sensitivity of 20 pm/∘C is realized. The proposed sensor has a compact structure, simple preparation, high coupling efficiency, and good repeatability, making it an ideal choice for simultaneous measurement of curvature and temperature in structural monitoring, mechanical manufacturing, and other fields.