提出一种基于双包层光纤和耦合器的双包层光纤微弯传感器结构及暗场检测方法。通过理论和仿真分析，建立了双包层光纤弯曲损耗的理论模型；通过对光纤结构参数与传感器灵敏度关系的仿真，获得了实验用光纤最佳结构参数；理论和仿真分析了变形器的最佳周期、齿间距和齿数问题；对双包层光纤微弯传感器及其暗场检测方法进行了实验研究，结果显示，传感器输出光场与光纤形变之间有着较好的线性关系。

In this paper, a double-clad fiber-optic microbend sensor and its dark-field detection method are presented. The theoretical model for the double-clad fiber bending loss is established by theoretical analysis and simulation. The optimum structural parameters are obtained by the simulation of the relationship between the fiber structural parameters and sensing sensitivity, the optimum period, tooth spacing and tooth number of the deformer are analyzed in theory and simulation and the double-clad fiber microbend sensor and its dark-field detection method are experimentally studied. The results show that there is a good linear relationship between the sensor output light field and fiber deformation.