Fiber Bragg grating strain sensor with extended measurement range via strain relief ring

A novel large strain sensor is designed and fabricated by radially mounting a fiber Bragg grating (FBG) onto an annular elastic element. The sensor responds to strain in a single direction through geometric deformation, featuring a large strain measurement range and adjustable sensitivity. This addresses the drawbacks of existing FBG strain sensors, such as fragility, limited strain measurement range, and challenges in adapting to diverse applications and installation scenarios. Our experiments demonstrate that at an angle of 40° between the FBG and the strain axis, the sensor achieves an impressive strain measurement range of 0 to 12,148 μϵ accompanied by a sensitivity of 0.151 pm/μϵ. The sensor's performance can be further tailored by adjusting the angle. For instance, at angles of 30°, 20°, and 10°, the sensitivities are enhanced to 0.506 pm/μϵ, 0.858 pm/μϵ, and 1.035 pm/μϵ, respectively. This flexibility allows for customized sensitivity and measurement range, catering to various application needs.