微扰模型分析长周期光纤光栅薄膜传感器

Analysis of Long Period Fibrer Grating by Perturbation Solution

提出了一种新的基于三层阶跃折射率光纤的微扰模型,分析长周期光纤光栅(Long Period Fiber Grating,LPFG)薄膜传感器,并从β2稳定性定理出发推导出适用于薄膜传感器的微扰公式.该模型不仅能够清晰反映薄膜参量与包层模传播常量变化量之间的关系,而且在计算量和计算难度远低于四层波导模型情况下获得与严格求解结果相当的计算准确度.考虑数值计算本身引入的计算误差,该模型能够满足定性和半定量理论分析需要.最后通过长周期光纤光栅液态水膜的挥发实验对该模型进行了初步验证.

A novel perturbation model based on 3-layer step refractive index fiber was presented which can be used to analyze LPFG film sensor. Perturbation equation of film sensor was educed by β^2 stability theorem. This model can be used to express the relation between film parameter and cladding-mode propagating parameter while it can get the same calculation accuracy as that of 3-layer model when the calculation quantity and difficulty are less. This model can satisfy the need of qualitative an＇d half- quantitative theoretical analysis enven though taking account of bias by numerical calculation. The model was proved by an experiment in which LPFG water film was volatilized.