Fabry-Perot vector curvature sensor based on cavity length demodulation

We have demonstrated a high-sensitivity Fabry-Perot curvature sensor. The main components of its sensing fiber are hollow silica tube and single-mode fiber (SMF). When the sensor is bent, the length of the FPI changes with curvature. Hereby, we can achieve vector curvature measurement through cavity length demodulation. The convex and concave bending sensitivities are 151.30 nm/m(-1) and 333.89 nm/m(-1), respectively. Besides, the curvature sensitivity is optimized with the increase of air cavity length. The packaging of the sensing fiber increases its robustness while increasing its sensitivity from 151.30 nm/m(-1) to 251.54 nm/m(-1). Meanwhile, the structure is insensitive to axial stress and refractive index (RI). This sensor has potential applications in engineering health detection and small-scale structural deformation detection.