Sensing principle of fiber-optic curvature sensor

•We carry out a ray tracing simulation by using optical analysis software TracePro.•We propose the sensing principle of fiber-optic curvature sensor.•The bent fiber shows a convex concentration feature.•The mathematic model of fiber-optic curvature sensor is presented.

A novel fiber-optic sensor, which can measure curvature directly, has been developed in recent years. Its curvature measurement sensitivity is improved by a sensitive zone. To better understand the working principle and improve the performance of the sensor, the ray tracing simulation was carried out by using optical analysis software TracePro, which provides the sensing process for us. The results show that the rays will concentrate to the convex side of bent fiber. That is, the light intensity will increase at convex side and decrease at concave side, which leads to the changes of light leakage at sensitive zone and realizes the modulation to light intensity. The mathematic model of relationship among light loss, parameters of sensitive zone׳s configuration and bending curvature is presented.