超紧凑结构光纤马赫-曾德温湿度传感器的研究

As one of the more difficult to measure and important environment parameters, humidity measurement has important applications in environmental monitoring, electric power, aerospace etc. To solve the disadvantages of existing interferometric fiber humidity sensors, such as high transmission loss, relatively weak signal, temperature crosstalk and low sensitivity, we propose a temperature and humidity sensor based on an ultracompact fiber Mach-Zehnder interferometer. The sandwich structure formed by hollow tapering cavity constitute Mach-Zehnder interferometer, which has characters of ultracompact, high fringe contrast and high stress sensitivity. Humidity changes are converted into wet strain by means of sensitive membrane depositing on the taper area, which make interference fringe shift. We will study the sensing mechanism, workmanship, signal processing method, multiplex techniques and encapsulation structure.The proposed sensor is made of silica fibers only, the major advantages of the optical fiber sensors over the conventional electrical sensors include the immunity to electromagnetic interference, resistance to harsh environment and capability of multiplexing. The proposed sensor also shows many desirable properties including high sensitivity, high precision, fast response, ultra-compact and simultaneous measurement of humidity and temperature, which make it has wide application prospects in the petrochemical, meteorological observation and aerospace sectors.

作为较难测量又特别重要的环境参量之一，湿度的测量在环境监测、电力、航空航天等众多方面有着重要的应用。本项目针对现有干涉型光纤湿度传感器传输损耗大，检测信号相对较弱、存在温度串扰及灵敏度不高的缺点，提出了基于超紧凑结构光纤Mach-Zehnder干涉的温、湿度传感结构。由空心拉锥腔和周围SiO2形成的三明治结构构成了Mach-Zehnder干涉仪，具有结构超紧凑、条纹对比度高、应力灵敏度高的特点；湿度的变化通过涂覆在拉锥区的敏感膜转换为湿应变使干涉条纹偏移。研究传感器的传感机理、制作工艺、信号处理方法、复用技术及封装结构。拟研制的传感器对湿度具有高灵敏度、高精度、快速响应，结构超紧凑并能同时测量温度和湿度的优点，适用于强电磁干扰、易燃易爆等恶劣环境，在石油化工、气象探测和航空航天领域有着广泛的应用前景。

作为较难测量又特别重要的环境参量之一，湿度的测量在环境监测、气象预报、农业生产、食品储存、电力、航空航天等众多方面有着重要的应用。针对已有光纤湿度传感器存在的传输损耗大，检测信号相对较弱、存在温度串扰及灵敏度不高的缺陷，本项目主要研究了一种基于超紧凑全光纤马赫-曾德干涉仪的温湿度传感器。设计制作了一种利用光子晶体光纤和普通单模光纤的熔接技术以及光纤拉锥技术构成的超紧凑全光纤马赫-曾德干涉仪。封闭在光纤內的纺锤型空气腔和其周围SiO2构成了三明治结构全光纤马赫-曾德干涉仪，干涉仪两个干涉臂介质为空气和SiO2，因此超短的干涉臂长使光传输损耗大大降低，构成超紧凑全光纤马赫-曾德干涉仪。基于这种超紧凑结构全光纤马赫-曾德干涉仪设计了应变和温、湿度传感器。借助理论分析与实验验证相结合的方法，研究了传感器的传感机理和制作工艺。在轴向应变0-10000με范围内，轴向应变灵敏度1pm/με；湿敏薄膜材料采用PI聚酰亚胺，在20%-95%湿度范围内，湿度灵敏度0.1nm/%RH，湿度测量精度±4%RH。研制的传感器具有高灵敏度、高精度、快速响应，结构超紧凑等优点，适用于强电磁干扰、易燃易爆等恶劣环境。.设计制作了基于微椭球型空气腔的光纤在线型干涉仪，基于这种干涉仪研究了一种波长调制型折射率传感器和一种微压传感器。折射率传感器在1-1.6范围内不出现折射率转折点；在1.333-1.466范围内, 折射率灵敏度~37.088nm/RIU, 分辨率~2.69×10-5。该传感信号干涉条纹对比度高、体积小、成本低，用于折射率测量可靠性高、分辨率高、无折射率拐点、温度串扰小。微压传感器基于F-P干涉原理测量压力，全石英结构，制作工艺简单，温度串扰小。