High sensitivity strain and refractive index MZI-SPR sensing based on dual fiber winding structure

Fiber strain and refractive index dual parameter sensor have enormous potential in the field of underwater structural health monitoring. This article proposes a strain and refractive index highly sensitive MZI-SPR composite sensor based on a dual fiber winding structure. By twisting single-mode fiber and multi-mode fiber, the two fibers are wound together to produce regular multiple bends. Among them, single-mode fiber achieves beam splitting and coupling of light during the first bending and the end of bending, forming a double beam interference MZI. The multi bending structure excites high-order cladding mode to achieve highly sensitive strain sensing. Meanwhile, multi-mode fiber excites cladding mode at the bending point and generate surface plasmon resonance effect, forming a cladding type SPR sensor. By controlling the winding parameters, the bending curvature is controlled, further controlling the SPR incidence angle and achieving highly sensitive refractive index sensing. The experiment indicates that the sensor can achieve simultaneous detection of strain and refractive index, and its sensitivity can reach 33pm/ µε and 4386.262 nm/RIU, respectively. The proposed MZI-SPR composite dual parameter sensor has a stable structure and high sensitivity, providing a reliable solution for simultaneously measuring strain and refractive index in the field.