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• The vector curvature sensor is based on an air cavity FPI. • Vector measurement of curvature can be achieved by cavity length demodulation. • The sensor has high curvature sensitivity and overcomes the crosstalk of small axial stress. 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. [ABSTRACT FROM AUTHOR]

• The vector curvature sensor is based on a single FBG. • Vector measurement of curvature can be achieved by tracking the offset of the central wavelength. • The sensor improves the curvature sensitivity and overcomes the crosstalk of small axial stress. A stress-insensitive vector curvature sensor based on a single fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The sensor is easily fabricated by encapsulating an FBG on a thin steel plate with ultraviolet glue. When the FBG deviates from the neutral plane, its effective refractive index and grating constant are changed by bending, therefore, the sensor can realize the curvature measurement. The sensitivity of the sensor in convex bending is 553.65 pm/m−1 in the range of 0.4798–1.3569 m−1. The sensor can realize vector measurement of curvature due to the opposite stress direction on the two sides of the neutral plane during bending. The concave curvature sensitivity of the sensor is −811.19 pm/m−1 in the range of 0.4798–1.3569 m−1. Due to the large stiffness of the thin steel plate, the package of the FBG makes it insensitive to small axial stress. The favorable stability of the sensor facilitates its practical application in the measurement of curvature and inclination. This sensor has the advantage of simple manufacture, low cost, and easy industrial production. [ABSTRACT FROM AUTHOR]