High-sensitivity strain sensor based on a Fabry–Pérot interferometer with a tapered capillary structure

A high-sensitivity strain sensor based on a Fabry–Pérot interferometer (FPI) with a tapered capillary structure is proposed and experimentally demonstrated. The sensor is designed to enhance strain responsiveness while minimizing temperature cross-sensitivity, making it suitable for precision strain measurements. It is fabricated by fusing a segment of capillary glass tube between two single-mode fibers using a cost-effective and simple method. The tapered air cavity deforms more readily under axial strain, resulting in improved sensitivity. In the strain range from 0 to 202.84 μ ε , the sensor exhibits a high strain sensitivity of 32.19 pm/ μ ε . In the temperature range from 30 to 80 ∘ C, the temperature sensitivity and strain–temperature cross-sensitivity were measured to be 3.26 pm/ ∘ C and 0.101 μ ε / ∘ C, respectively.The sensor also demonstrates excellent stability and repeatability. These characteristics highlight its potential for structural health monitoring in aerospace, civil infrastructure, and energy systems.