Development of Smart Structure for Thermo-Insulating-FRP-Support-Structure by Using Optical Fiber Sensor

超导线圈用复合支撑结构由于其外覆绝缘结构，因此对其进行自动健康监测是非常重要的。超导线圈的复合支撑结构处于强变磁场中。这导致很难应用电学方法来检测缺陷。虽然我们可以使用几个光学应变传感器，但仍然昂贵，并且长期可靠性存在一些问题。因此，在本研究中，一种新的光学应变传感器，利用宏观尺度弯曲的功率损耗，并进行了详细的研究。弯曲的光纤连接到样本。当试件受扭时，弯曲光纤半径的变化会引起光功率损耗的变化。通过计算，找到了最佳的光纤路径结构（四分之一圆）。在静态和循环载荷下对传感器的适用性进行了实验研究。由于该系统结构简单，价格低廉，具有足够的可靠性。

Since composite support structures applied to super conductivity coils are covered by structures for insulation, automatic health monitoring system is very important for the structures. The composite support structures for super conductivity coils are in strong variable magnetic fields. This causes that it is very difficult to apply electrical methods for detection of defects. Though we can use several optical strain sensors, there have been still expensive and had some problems for long term reliability. In the present study, therefore, a novel optical strain sensor using power loss by macro scale bending was developed, and was investigated in detail. Curved optical fiber was attached to specimens. When the specimen is tnesioned, optical power loss changes due to the change of radius of curved optical fiber. The optimum fiber path configuration (quarter circle) was found by computations. The applicability of the sensor was investigated experimentally under the static and cyclic loading. Since the system is simple, it is very inexpensive and has enough reliability.