镀膜级联长周期光纤光栅折射率传感研究

镀膜的级联长周期光纤光栅（Cascaded Long-Period Fiber Gratings, CLPFGs）对膜层的折射率及环境折射率有很高的敏感性, 可用作气体传感器或溶液浓度传感器。本文采用耦合模理论与传输矩阵法, 数值计算了不同薄膜厚度下镀膜CLPFGs干涉峰波长的相对变化率与薄膜折射率的相对变化率的比值, 及不同薄膜厚度下镀膜CLPFGs干涉峰波长的相对变化率与环境折射率的相对变化率的比值。选择恰当的镀膜厚度, 使镀膜CLPFGs传感器的灵敏度最优化, 结果表明镀膜CLPFGs传感器对薄膜折射率及环境折射率的分辨率可达10-5。

Refractive Index Sensing of Cascaded Long-Period Fiber Gratings with Film Coating

Cascaded long-period fiber gratings (CLPFGs) with film coating is highly sensitive to the film refractive index and surrounding refractive index, so it can be used as gas sensor or solution concentration sensor. The ratio between the relative change of interference peak wavelength of CLPFGs with film coating and relative change of the film refractive index, and the ratio between the relative change of interference peak wavelength of CLPFGs with film coating and relative change of the surrounding refractive index under different film thickness are numerically calculated using couple-mode theory and transfer matrix method. By choosing appropriate film thickness, we can obtain higher sensitivity. Data simulation shows that the sensitivity to film refractive index and surrounding refractive index is predicted to be 10-5.