Development of grating fiber sensor with asymmetrical cross section detectable the bending direction for prevention of slope failures

微机械加工的光纤被认为是一种防止斜坡失效的传感器。利用中心反射波长与其他波长的反射光功率之差来检测光纤尖端液体的折射率具有一定的可能性。测量了两个中心反射波长不同且具有相似不对称截面且刻蚀面不同的两个FBG串联排列时的反射光谱。结果表明，当熔覆层厚度为14μm时，弯曲方向的识别精度为5°，曲率识别精度为3.0m-1。

Micro-machined grating fiber was evaluated as a sensor for prevention of slope failures. There is some possibility to detect refractive index of liquid on the fiber tip by the difference of reflected light power between at the center reflection wavelength and at the other wavelengths. Reflected light spectra were measured, when a serial arrangement of two FBGs with two different center reflection wavelengths and similar asymmetrical cross sections with different etching faces was bent. It was found that bend was recognized with accuracy of 5°in bend direction and 3.0 m-1in curvature when the clad thickness was 14μm.