基于高局域化FBG的液相扩散过程监测方法研究  

Monitoring Method of Liquid Diffusion Process Based on High Localized FBG

作　　者：周峰 王龙南 曾雨琪 罗潇 刘显明[1] ZHOU Feng;WANG Longnan;ZENG Yuqi;LUO Xiao;LIU Xianming(Key Lab of Optoelectronic Technology&Systems Ministry of Education,College of Optoelectronic Engineering,Chongqing University,Chongqing 400044,China;AECC Hunan Aviation Powerplant Research Institute,Zhuzhou 412002,China)

机构地区：[1]重庆大学光电工程学院,光电技术及系统教育部重点实验室,重庆400044 [2]中国航发湖南动力机械研究所,株洲412002

出　　处：《光子学报》2024年第10期169-178,共10页Acta Photonica Sinica

基　　金：国家重点研发计划(No.2022YFB3207500)。

摘　　要：提出了一种利用高局域化光纤布拉格光栅测量液相扩散过程的方法。采用飞秒激光和相位掩模法在载氢的普通单模光纤中成功制备了一种高局域化光纤布拉格光栅,其折射率变化区域在光束入射方向上高度局域在纤芯中,从而在透射光谱中除了具有纤芯模式对应的损耗峰之外,还具有丰富的包层模式对应的损耗峰,纤芯模式和包层模式对应的损耗峰分别达-17.6 dB和-17.2 dB。实验测得光栅截止模式对液体折射率很敏感,截止模式对应的损耗峰中心波长随液体折射率呈线性变化,折射率灵敏度为531.69 nm/RIU,而纤芯模式几乎不随液体折射率发生改变,可用于折射率测量过程中的温度补偿。将高局域化光纤布拉格光栅布设在两种液体的分界面处时,随着液相扩散过程的进行,光纤周围液体的折射率发生变化,通过监测高局域化光纤布拉格光栅透射光谱中截止模式中心波长的变化,实现了对液相扩散过程的原位实时监测。Monitoring of liquid phase diffusion process in real-time is very important in many fields such as chemistry,biomedicine,environmental science and so on.The traditional methods of liquid phase diffusion measurement mainly include nuclear magnetic resonance,optical holographic interferometry,diaphragm cell,etc.Fiber Bragg grating(FBG)has many advantages and especially can be used in harsh environment,so it has been widely used for sensing temperature,strain and refractive index.However,for ordinary FBG,the core mode is transmitted in the fiber core,so it can't be used directly for monitoring the liquid phase diffusion process.One method is coupling the light to the fiber cladding to excite the cladding modes,which are very sensitive to the refractive index.At present,there are three types of FBGs with strong cladding modes:tilted FBG(TFBG),off-axis FBG and high localized FBG(HLFBG).HLFBG is suitable for monitoring the liquid refractive index and liquid phase diffusion process and is usually inscribed by the femtosecond laser and point-by-point method,but high accuracy motorized linear translation stages are required.In this paper,a new monitoring method of liquid phase diffusion process based on HLFBG is proposed.The HLFBG is inscribed in hydrogen-loaded fiber by femtosecond laser and phase mask method.In order to reduce the peak power of femtosecond laser and avoid damage to the phase mask,the standard single-mode fiber is hydrogen loaded under 8 MPa and 120°C for a week before inscription of FBG.A HLFBG with grating period of 1.071μm is successfully inscribed by using femtosecond laser with a pulse energy of 400μJ,a phase mask with period of 2.142μm and a cylindrical lens with focal length of 40 mm.The width of the refractive index modulation region induced by femtosecond laser is about 4μm,which is smaller than the fiber core diameter of 9μm,so the refractive index modulation region of FBG can't completely cover the fiber core,resulting in high localization effect.The dip corresponding to the core mode in

关 键 词：高局域化FBG 液相扩散 折射率 飞秒激光 截止模式 

分 类 号：TP212[自动化与计算机技术—检测技术与自动化装置]