High sensitivity vector torsion sensor based on a single Stress-Applying fiber Sagnac interferometer

•A torsion sensor based on a Single Stress-Applying Fiber (SSAF) Sagnac interferometer isproposed and experimentally demonstrated.•The sensor can achieve themeasurement sensitivity up to 53.3 nm/(rad/m)and has directional recognition characteristics.•The influence offiber structure on sensorperformanceis analyzed theoretically.