Strain Measurement by Curved Optical Fiber Sensor

Abstract

Since composite structures applied for supporting super conductivity coils are covered by structures forinsulation, health monitoring systems are very important for the structures. Composite structures will be used in strong variable magnetic fields. This causes significant difficulty in applying electrical methods for detection of defects. Although we can use several optical strain sensors, they are still expensive and have some problems of long term reliability. In the present study therefore, a novel optical strain sensor using power loss by macro scale bending was developed and investigated in detail. A curved optical fiber was attached to specimens. When the specimen is tensioned, the optical power loss changes due to the change of radius of the curved optical fiber. The optimum fiber path configuration (quarter circle) was found by computations. The applicability of the sensor was investigated experimentally under static and cyclic loading. As a result, the sensor was proved to be very effective and to be reliable at low cost.