非均匀应变场下相移光栅光谱特性及其实验研究

采用传输矩阵法系统研究轴向非均匀应变场下相移光栅光谱特性，对均匀应变、线性应变、二次应变以及三次应变分布下相移光栅反射谱进行仿真，分析应变分布函数各项系数对反射率、通透带宽、透射窗口对应波长以及光谱形状的影响，并得出规律性结论。基于不同形状悬臂梁组建应变调谐实验装置，利用有限元法计算固定于不同形状悬臂梁表面相移光栅栅区应变分布，结合数值计算结果进行相移光栅应变调谐实验，研究相移光栅栅区轴向在均匀应变场、线性应变场以及二次应变场下相移光栅的反射光谱，实验结果表明在不同应变场下相移光栅反射谱呈现规律性变化，与仿真结果很好吻合。

Research on the Phase-Shifted Fiber Grating Spectrum Characteristics in the Inhomogeneous Strain Fields

Based on the transfer matrix method, the spectrum characteristics of phase-shifted fiber grating were analyzed systematically, and the reflection spectra of phase-shifted fiber grating under uniform strain, linear strain, secondary strain and cubic strain were simulated respectively. The regularity conclusion that the influence of different strain distribution functions on reflectivity, transmission bandwidth, wavelength of transmission window and spectral shape came out. In order to verify the simulation result, strain-tuning equipment was designed based on cantilever with different structures. Finite element method was carried out to simulate the strain distribution of phased shift fiber grating fixed on the surface of cantilever during the strain-tuning experiment. Experiment result demonstrated that the reflection spectra of phase-shifted fiber grating under uniform strain, linear strain and secondary strain exhibited a regular change, which is in agreement with simulation results.