Simultaneous detection of vector bending and temperature using dual-core fiber cascaded FBG structure

•Our sensor based on the MMF-DCF-MMF-FBG realizes bending recognition in different directions and temperature measure simultaneously.•The DCF features two cores that are spaced relatively far apart and symmetrically arranged in a linear array. It has advantages such as vector property, high sensitivity bending response capability, and ease of integration and application.•The vector bending sensor exhibits the max sensitive bending response could reach 18.259 nm/m−1 with the curvature increasing from 0 to 0.882 m−1 and the bending direction ranging from 0° to 135°. In the paper, we experimentally presented vector bending sensor based on the multimode-dual core- multimode fiber cascaded Fiber Bragg grating (FBG) structure, which owns the ability of dual-parameter detection. These two multimode fibers (MMFs) function as a mode beam expander and a mode coupler, separately, and the FBG is used to eliminate the temperature crosstalk. Because of the central symmetry of the dual-core fiber (DCF) and its two cores arranged in a linear array, the sensor can achieve recognition directional bending. The experiment of results demonstrates our sensor exhibits a robust response to vector bending response with the max bending sensitivities of 18.259 nm/m−1 in the bending direction of 0°. The temperature sensitivity of the resonance wavelength generated by the Mach-Zehnder interferometer (MZI) and FBG can reach −0.285 nm/°C and 0.010 nm/°C, separately. Through the dual wavelength matrix method, we can achieve simultaneous measurement of vector bending response and temperature response. Featuring notable strengths such as high vector bending sensitivity, ease of fabrication, low cost, and direction recognition, the sensor can be applied in various fields of vector bending measurement.