弯曲增敏型光纤曲率传感器机理的研究

近年国外出现一种直接检测弯曲的低成本光纤曲率传感器,采用弯曲增敏技术提高光纤对弯曲的灵敏度。这种传感器的线性范围宽,能区分正向弯曲和负向弯曲,在测量较大弯曲变形的场合更具优势;并且适合埋入结构内部检测,通过转换还可测量轴向应变。然而其传感机理方面的研究仍处于探索阶段。通过分析光辐射度余弦定律理论、回音壁光线理论、沟槽角度理论等国内外对该传感器机理的研究成果,并基于平面波导的光散射损耗理论,提出了光纤曲率传感器的机理。指出弯曲引起光纤敏感区表面散射损耗的改变是导致光传输损耗改变的原因;推导出损耗与光纤弯曲半径、表面特性、光纤结构参量关系的数学模型,并通过实验验证了模型的有效性。

Operation Principle of a Bend Enhanced Curvature Optical Fiber Sensor

A low cost curvature optical fiber sensor that can detect curvature directly is developed in recent years;its curvature measurement sensitivity is improved using bend enhanced method and the sensor can distinguish between positive bending and negative bending.This sensor has a wide linear range and is suitable for measuring large curvature deformation.It meets the demand for embedded measuring in structure.With transfering strain to curvature,it can also measure axial strain.Nevertheless,the operation principle of this sensor is still under exploration.Through analyzing radiation law of cosines,whisper gallery ray and groove angle theories,the operation principle of this intensity modulated macro-bend curvature optical fiber senor is presented based on light scattering theory: bending of sensitive zone bring about mode coupling and lead to the variation of surface scattering loss.The mathematic model of relationship among light loss,bending curvature,surface roughness and parameters of the fiber's configuration is also presented.Experimental results have demonstrated the proposed model.