基于笼形分子敏感膜涂覆的光子晶体光纤甲烷气体浓度检测技术研究

Gas accident is always the main threat to safe production in coal mille，and it is necessary to prevent and control gas accident．So far，monitoring concentration of methane gas(the main component of gas，83-89％CH4)，which is the most important component in coal mine，is the effective approach．Recently，several techniques have been developed for methane detection including semiconductor detectors，thermal catalytic, optical interference，infrared absorption and electrochemical method，etc．These methods are not remotely distributed real-time monitoring,and they have great limitations. In order to further improve the ability of mine gas monitoring, a cryptophane sensitive film coating based distributed photonic crystal optical fiber methane sensor was developed.Based on the refractive index sensitivity of the sensitive film to the methane concentration, as well as the interference phenomenon between the core-mode and cladding-modes of photonic crystal fiber, an all-fiber detecting structure with a reflecting long tail probe was designed, which could realize the real-time monitoring of methane in the time domain as well as in a remote distance. The main research work includes: Design of the reflecting photonic crystal fiber Mach-Zehnder interferometric sensing probe；Research on the key method to improve the coupling ratio among modes as well as to decrease the optical loss；Study on the fabrication of sensing film with cryptophane and the mechanism of action between methane and cryptophane；Modeling of the relationship between methane concentration and Mach-Zehnder interferometric spectrum；Experimental proving of the theoretical analysis and test of the response to surrounding environment.

瓦斯事故是煤矿安全生产的最大威胁之一，监测甲烷 (瓦斯主要成分，约占83%-89％)浓度则是一种预防瓦斯事故发生的重要手段之一。目前，已有基于半导体、热催化、光干涉、红外吸收、电化学法等不同类型的甲烷传感器，但都无法进行远程分布式实时监测，给瓦斯监测工作带来了很大局限性，为了进一步提高矿井瓦斯监测的能力，本项目提出一种基于笼型分子敏感膜涂覆的光子晶体光纤甲烷浓度传感器，借助敏感膜折射率对甲烷浓度的敏感性，以及光子晶体光纤的模间干涉现象，设计出一种反射式的全光纤长尾探头结构，为实现甲烷浓度远程实时监测提供了可能。主要研究工作包括：反射式马赫曾德干涉光子晶体光纤传感器设计，以及提高耦合效率及降低损耗的关键技术研究;笼形分子敏感膜的制备方法以及甲烷与笼形分子敏感膜的作用机制研究;并建立甲烷浓度与马赫曾德干涉谱漂移之间的关系模型，进行实验验证以及外部环境影响测试。

提出了一种双腰式光子晶体光纤马赫曾德干涉结构，实现了折射率的测量，在1.3374到1.3477的折射率范围内，灵敏度为263.469 nm/RIU，该结构损耗小，稳定性好，灵敏度高，不易折断，具备实用价值；提出了一种长尾式光子晶体光纤马赫曾德干涉结构，可方便地延伸到测量现场，节约光纤线路的距离，可有效减少损耗，节约能源；在光子晶体光纤马赫曾德干涉结构表面涂敷笼形分子敏感膜，实现了甲烷浓度的测量，在0%-5%甲烷气体浓度范围内，波长漂移灵敏度达到129.91nm/浓度百分比，为生化、煤矿等场合中甲烷气体浓度远程在线检测提供了重要依据，具有本质安全、尺寸小、易于分布式测量等优点；通过金属毛细管封装，并填充乙醇作为敏感介质，实现了温度的测量，在76 °C 至80 °C温度范围内，温度测量的灵敏度为0.3379 nm/°C，具有结构简单、灵敏度高、无需温度补偿等优点，为甲烷浓度与温度的同步测量提供了实验依据；提出了一种具有独立探头结构的光子晶体光纤萨格那克干涉仪，可以作为甲烷浓度传感器的主要结构之一，推导了干涉谱方程以及干涉谱周期与光子晶体光纤长度之间的关系，为甲烷气体浓度传感器实用化和小型化奠定了理论基础；提出了一种基于WGM谐振器的磁场传感器，磁流体渗透腐蚀性的六氯环己烷与逐渐变细的光纤耦合，当空芯光纤壁厚为2μm时磁流体的体积比为0.7%时，获得了32.4pm/Gs的高磁场灵敏度；提出了一种可同时测量温度和汞离子（Hg2+）浓度的反射式光纤传感探头，将壳聚糖（CS）/聚丙烯酸（PAA）作为Hg2+敏感膜，并采用逐层自组装的方法在无芯光纤表面涂覆，Hg2+的灵敏度可达0.0823nm/μM，可重复性好，具有结构简单、制造容易、机械性能好等优点，强度高，成本低，适合远距离测量，也为实现甲烷浓度与其他参量多参数测量提供了实验基础。