光纤传感器端面结构对反射面形状因子的消除作用分析

Analysis of Elimination Effect of Shape Factor of Reflecting Surface by End Structure of Optical Fiber Sensor

在光纤式叶尖间隙测量系统中,光源波动、光纤弯曲损耗、反射面粗糙度和反射面形状因子会降低测量精度,为此从光纤传感器端面结构入手分析了双圈型和三圈型端面结构对这些影响因素的消除作用。通过建立带反射面形状因子的单光纤对接收光功率函数模型,发现双圈型端面结构可以通过接收光功率的比值消除光源波动、光纤弯曲损耗以及粗糙度的影响。然而双圈型接收光功率的比值同时与间隙和反射面形状因子有关,因此单个比值无法消除反射面形状因子的影响,但可通过采用三圈型端面结构,用两组比值来消除反射面形状因子的影响。三圈型端面结构可以进一步消除双圈型端面结构不能消除的反射面形状因子影响,因此具有更为广泛的适应性。

In fiber optic tip clearance measurement systems,source fluctuations,fiber bending losses,reflective surface roughness,and shape factor of the reflecting surface will reduce the measurement accuracy. Therefore,by changing the end structure of the fiber sensor,the elimination effects of the double loop type and the three loop type end structures on these influencing factors are analyzed. By establishing a single optical fiber pair receiving optical power function model with shape factor of the reflecting surface,it is found that the double loop type end structure can eliminate the influence of source fluctuations,fiber bending losses and roughness by the ratio of received optical power. However,the ratio of the double loop type received optical power is related to both the blade tip clearance and the shape factor of the reflecting surface at the same time,so that the single ratio cannot eliminate the influence of shape factor of the reflecting surface,but the influence of shape factor of the reflecting surface can be eliminated by the two ratios by adopting the three loop type end structure. The three loop type end structure can further eliminate the influence of the shape factor of the reflecting surface which cannot be eliminated by the double loop type,and thus has wider adaptability.