U型缠绕式光纤弯曲损耗位移传感器设计

Design of Displacement Sensor Based on the Bending Loss of U-Type Wingding Fiber

针对传统光纤弯曲损耗位移传感器中位移与弯曲损耗的非线性关系,且高灵敏度和大量程不能兼得的问题,设计了一种U型缠绕式光纤弯曲损耗位移传感器,结构包括U型回绕和螺旋绕轴,两者合称为U型缠绕。理论证明被测位移量与光纤弯曲损耗之间的线性关系,推导出表达式,讨论了螺旋绕轴方式对光纤弯曲半径的影响和U型回绕方式对传感器精度的影响,并进行了一系列实验研究和性能测试。结果表明:传感器的测量范围为0~120mm,灵敏度为0.14dB/mm,线性相关系数大于0.99,光纤在U型缠绕中无应力松弛的现象,建议U型回绕光纤曲率半径大于6mm。U型缠绕式光纤弯曲损耗位移传感器具有良好的测量精度和较大量程,能够实现传感器对混凝土结构的裂缝监测和大型结构位移的连续监测。

In view of the nonlinear relationship between displacement and bending loss in traditional fiber bending loss displacement sensor,and the problem that high sensitivity and large scale cannot be obtained at the same time,we design a novel displacement sensor based on the bending loss of U-type winding fiber.The fiber consists of a U-type turning and a spiral winding around the shaft,which of them are called U-type winding.It is proved theoretically that there is a linear relationship between the measured displacement and the bending loss.We deduce the expression of them,discuss the effect of spiral winding on the bending radius of fiber and the effect of U-type turning on the accuracy of the sensor,and carry out a series of experimental studies and performance tests.Experimental results demonstrate that displacement sensitivity of the sensor is 0.14 dB/mm in the range from 0 to120 mm,and the linear correlation coefficient is greater than 0.99.There is no stress relaxation of the optical fiber in the winding process.It is suggested that the radius of curvature of the U-type turning fiber should be larger than6 mm.The displacement sensor based on the bending loss of U-type winding fiber has good measurement precision and large scale.It can realize the monitoring of concrete structure cracks and continuous monitoring of the displacement of large structure.