Highly Sensitive Curvature Sensor Based on Quasi-Curved Structure with Temperature Independent

In this article, a core-offset inline-fiber Mach-Zehnder interferometer (CI-MZI) for curvature sensing is proposed and experimentally verified. Here, the proposed sensor is fabricated by the splicing method, by which a single-mode fiber (SMF) is introduced between two core-offset connectors with a large core-offset distance. With advantages of quasi-curved structure, when external bending applies to the CI-MZI, the portion of quasi-curved structure gets influence severely, which strongly affects the light propagation. Under theoretical analysis and experimental investigation, the CI-MZI is further optimized. In the experiment, the sensor exhibits a peak sensitivity to curvature of 244.29 nm/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> along the 0° direction, -80.74 nm/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at 180°, and -20.67 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>at 90°. Additionally, a temperature sensitivity of 23 pm/°C is achieved, and a low curvature-temperature crosstalk of 9.7S×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>/°C is obtained. With advantages of cost-effective, excellent sensitivity and temperature independent, the proposed CI-MZI has potential applications in curvature measurements.