Experimental study on temperature-insensitive curvature sensor based on reflective all-fiber structure

In the paper, a reflective all-fiber sensor for curvature measurement has been proposed, which is composed of Mach-Zehnder interferometer (MZI) and Fabry-Pérot interferometer (FPI). The MZI section acts as curvature sensing unit and is made by splicing a section of twin-hole and dual-core fiber (THDCF) between two sections of seven-core fiber (SCF). The FPI section is made by introducing an FPI cavity between two segments of single mode fibers inside a hollow core capillary through using UV-curable resins and used to reflect the energy. The reflection spectrum information tuned by MZI has respond to bending change. The experiment results show the reflective sensor exhibits a high curvature sensitivity and low temperature sensitivity of −1.19 nm/m−1 and −1 pm/°C in the range of 0–5.7778 m−1 and 30–100 °C, respectively. With the advantages of reflective structure, compact size, easy fabrication, and low temperature crosstalk, our sensor could be widely used in practical applications.