Optical fiber sensor for micro displacement monitoring based on a balloon-like interferometer with a spring-shaped structure

A sensor based on a balloon-like interferometer and a spring-shaped structure for micro curvature measurement is proposed and experimentally demonstrated. The sensor is composed by singlemode fiber inserted into a capillary tube. The experimental results show micro-curvature sensitivities of -35.04 pm/mu m, -28.07 pm/mu m e -18.7 pm/mu m in the range from 0 to 200 mu m for three resonants dips lambda(1), lambda(2) and lambda(3), respectively. In addition, the sensor has advantages of easy fabrication, low cost, and satisfactory sensitivity, which shows good results of sensing of micro curvature in some applications.