Design and construction of a fiber-optic microbend sensor for structural strain monitoring
摘要
A fiber-optic microbend strain sensor is designed and constructed for structural strain monitoring applications. The sensing principle is based on the periodic microbending-induced optical losses resulting from mechanical deformation of a multimode optical fiber, which modifies the evanescent field and enhances the coupling to radiation modes. Three microbend cells with different pitches (3, 5, and 8 mm) are fabricated using locally manufactured periodic mechanical curvatures. The experimental setup consists of a multimode optical fiber, an 810 nm laser diode source, a microbend deforming cell, and an optical power meter. The external forces in the range of 5–60 N are applied to induce strain in the fiber, and the corresponding strain values are calculated for each microbend configuration. The results indicate that the 3 mm microbend cell exhibits the highest strain sensitivity, with a maximum strain of ε = 7⋅10−8 at 60 N and a minimum strain of ε = 1⋅10−8 at 5 N. For the 5 mm cell, the strain ranges from ε = 2⋅10−9 at 5 N to ε = 1.3⋅10−8 at 60 N. In contrast, the 8 mm cell exhibits the lowest strain response, with the strain values ranging from ε = 1.5⋅10−10 at 5 N to ε = 4.5⋅10−10 at 60 N. The calculated sensor sensitivity is approximately 0.02 per unit force, demonstrating the suitability of the proposed microbend sensor for practical structural strain monitoring applications.