A Fabry–Perot Interferometer Strain Sensor Based on Concave-Core Photonic Crystal Fiber

A high-sensitivity Fabry-Perot interferometer (FPI) strain sensor based on a concave-core photonic crystal fiber (CPCF) was proposed and demonstrated. The FPI was formed by directly splicing a CPCF to a standard single-mode fiber. The CPCF was fabricated by cleaving a high-numerical-aperture solid-core photonic crystal fiber under axial tension using a traditional fiber cleaver. An FPI strain sensor with a cavity length of 4.85 μ m and a strain sensitivity of 31.58 pm/με was successfully produced. The sensor also demonstrated a low temperature sensitivity of 0.653 pm/°C, reducing the cross-sensitivity between tensile strain and temperature. The benefits of the proposed sensor include simple fabrication, high strain sensitivity, and low temperature cross-sensitivity, making it attractive for practical applications.