基于耦合模理论及传输矩阵法,给出了级联长周期光纤光栅和Bragg光纤光栅系统(CLBG)的耦合模方程与总传输矩阵,理论模拟了CLBG的反射谱,得到的反射峰位置与已知文献中所给出的两个反射峰的位置关系相吻合。在此基础上,模拟了镀膜CLBG之间的光纤长度、薄膜折射率、薄膜厚度等参数对反射谱的影响。由仿真结果可知,CLBG反射峰中受长周期光纤光栅和Bragg光纤光栅共同影响产生的反射峰对外界环境的变化非常敏感,其对薄膜折射率的分辨率较单个镀膜长周期光纤光栅高2个数量级,表明CLBG在薄膜传感领域具有重要的应用价值。 Based on the coupled-mode theory and the transfer matrix method, the coupled-mode equations and the total transfer matrix of the cascade long-period fiber grating and the Bragg fiber grating system (CLBG) are given. The reflection spectra of the CLBG are theoretically simulated. The positions of the two reflection peaks given in the literature agree. On this basis, the influence of parameters such as fiber length, film refractive index and film thickness on the reflection spectra of the coated CLBG was simulated. From the simulation results, it can be seen that the reflection peaks caused by the combination of long-period fiber grating and Bragg fiber grating in the CLBG reflection peak are very sensitive to the change of the external environment, and the resolution of the refractive index of the film is 2 higher than that of a single coated long-period fiber grating Order of magnitude, indicating that CLBG has an important application value in the field of thin film sensing.