光纤布拉格光栅横向应变特性的研究

根据耦合模理论，对光纤布拉格光栅(FBG)的横向应变特性进行了深入研究，并采用数值分析方法对光纤布拉格光栅在平面应变和应力情况下进行了模拟分析：对于平面应变情况，一个谐振峰向波长增大的方向移动，而另一个谐振峰向波长减小的方向轻微移动；对于平面应力情况，两个谐振峰都向波长增大的方向移动。设计了相应的实验进行验证，实验结果与理论分析相符；该实验结果表明光纤布拉格光栅的横向应变情况介于平面应力和平面应变之间，而且更接近平面应力情况。根据理论分析，横向应变与纵向应变对波长漂移的贡献不一样，从而使三维应变测量成为可能。

Study on Transversal Strain on Fiber Bragg Grating

In this paper, the transversal strain on fiber Bragg grating (FBG) is specially analyzed according to the couple-mode theory. For both cases, plane strain and plane stress, numerical simulation is done for uniform FBG. In the case of plane strain, one peak of the reflection spectrum shifts towards the longer wavelength, while the other shifts slightly towards the shorter wavelength and in the case of plane stress, both peaks shift towards the longer wavelength. Finally, a plan of experiment on FBG under lateral load is designed to examine the conclusions. Good agreements between experimental results and numerical simulations have been obtained. The results of the experiment indicate that the transversal strain is between the case of plane strain and plane stress and more close to the case of plane stress. Since the transversal strain and the axial strain have different contributions to the wavelength shift based on the theoretical analysis, it is possible to obtain the measurement of three-dimensional strain from the Bragg reflection wavelength variation.