基于覆膜锥形长周期光纤光栅的高灵敏度海水盐度传感器研究

Research on High Sensitivity Salinity Sensing Using Tapered LPFG with Overlay Deposition

文章提出了一种基于包覆TiO_(2)纳米薄膜锥形长周期光纤光栅(long-period fiber grating,LPFG)的高灵敏度海水盐度传感器。通过将多种增敏方案,包括调节LPFG的工作点位于转换点附近、倏逝场增强和模式转变效应有效结合,显著提高了传感器在海水盐度典型变化范围(0.5~0.8 M)对应的环境折射率变化(1.339~1.342)区间内的灵敏度。利用四层圆柱形波导模型,采用矢量模分析法计算了传感器的优化参数。利用原子层沉积技术,将TiO_(2)纳米薄膜包覆在锥形光纤上制备的LPFG表面。实验结果表明:LPFG的HE1,12模式的环境折射率灵敏度超过1×10^(4)nm/RIU,盐度灵敏度超过110 nm/M,线性度达到0.998。实验结果与理论计算吻合较好。

This article demonstrate a highly sensitive salinity sensor based on the tapered long-period fiber grating(LPFG)coating with the titanium dioxide(TiO_(2))film.By combining the dispersion turning point,the evanescent field enhancement and the mode transition effects,the surrounding refractive index(SRI)sensitivity is enhanced significantly in the range 1.339~1.342 which corresponds to the typical salt concentration range 0.5~0.8 M.The theoretical model of the hybrid modes in four-layer cylindrical waveguide is proposed to obtain the optimal parameters.The atomic layer deposition technology is utilized to deposit a TiO_(2)nanofilm on the surface of LPFG written in the tapered fiber.The SRI sensitivity exceeding 1×10^(4)nm/RIU is obtained in the range 1.339~1.342 for HE1,12 mode.The salinity sensitivity exceeding 110 nm/M is achieved,the linearity is 0.998.The experimental results are well consistent with theoretical calculations.