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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。
In recent years, there is a foreign direct detection of bending low-cost optical fiber curvature sensor, the use of bending sensitization technology to improve the optical fiber sensitivity to bending. The wide linear range of this sensor distinguishes forward and negative bends, giving them an advantage in measuring large flexural deformations and is suitable for embedded internal inspection of structures, which can also measure axial strain. However, the research on its sensing mechanism is still in the exploratory stage. The mechanism of optical fiber curvature sensor is proposed based on the research results of the cosine law of light radiance, the theory of light ray of echo wall and the groove angle theory at home and abroad, and based on the light scattering loss theory of planar waveguide. It is pointed out that the change of surface scattering loss caused by bending causes the change of optical transmission loss. The mathematical model of the relationship between loss and fiber bend radius, surface characteristics and fiber structure parameters is deduced. The validity of the model is verified by experiments.