双峰效应光纤光栅薄膜传感器的优化设计

Optimization design of fiber grating film sensor based on dual peak resonance

利用双峰谐振效应,通过在长周期光纤光栅(LPFG)包层表面涂覆一层对周围气氛敏感的薄膜,建立了一种新型薄膜传感器,其双峰谐振波长间隔随薄膜折射率的变化而变化。基于三包层光纤光栅物理模型,根据耦合模理论研究了传感器的灵敏度Sn与薄膜光学参数(折射率n3和厚度h3)和光纤光栅结构参数(光栅周期Λ、折变量σ)之间的关系。采用最优化数值方法,确定了最佳的膜层光学参数和光栅结构参数。计算表明,该类型传感器对膜层折射率的测量分辨率高达10-7。

Based on dual peak resonance of long-period fiber grating（LPFG）, a novel film sensor is presented, in which the film that is sensitive to the surrounding gases is coated on the cladding of the fiber grating region,and the intervals of dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory,a triple-clad numerical model is developed to analyze the relationship between the sensitivity and the thin film optical parameters（the film thickness and the refractive index） and the fiber grating parameters（the grating period and the core index modulation）. By using the optimization method,the optimal film optical parameters and the grating structure parameters are obtained. Data simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to he more than 10 ^-7.