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 <i>μ</i><i>ε</i>, the sensor exhibits a high strain sensitivity of 32.19 pm/<i>μ</i><i>ε</i>. 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 <i>μ</i><i>ε</i>/^∘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.