光纤气体传感技术的研究
文献类型：学位论文
| 作者 | 王允韬 |
| 学位类别 | 博士 |
| 答辩日期 | 2008 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 方祖捷 |
| 关键词 | 光纤气体传感 波长调制光谱 微结构光纤 应变传感 |
| 其他题名 | Study on fiber gas sensor |
| 中文摘要 | 本论文以光纤气体传感技术为目标，开展了两方面的研究：一是波长调制吸收光谱在光纤气体传感技术中的应用；二是对微结构光纤用于气体传感和其他物理量的传感进行了探索和实验研究。 本文综述了波长调制光谱技术的发展，介绍了有关的基本理论和实验研究状况；分析了将波长调制光谱技术和光纤技术应用于气体传感的优点。 鉴于我国瓦斯监测的紧迫性，和进一步技术发展的要求，本文针对甲烷在1650nm波段的吸收线，研发了一套波长调制吸收光谱光纤瓦斯传感装置。该系统包括激光器驱动电路、温控电路、传感探头、光电探测电路、数据处理程序几个部分。在浓度范围0－4％之间，本文系统可以达到10ppm甲烷体积浓度的测量分辨率，在4％以上，可以达到100ppm的分辨率。 本文对波长调制光谱技术中一系列的机理和技术问题进行了理论分析和实验研究，取得了以下的主要结果： 推导了偶次谐波随光学深度变化的近似的解析公式，该公式很好地解释了偶次谐波的双值特性以及存在零值的性质。理论分析结果得到了实验验证。 理论分析和比较了偶次谐波方法、二次/一次谐波比值方法和对数光谱方法的特性和优劣并且指出了对数方法的优越性。讨论了半导体激光器中与波长调制相伴随的功率调制问题；研究了对数光谱中的光源功率调制，首次得到了其傅里叶系数的严格解析结果；推导了波长调制存在二次项时，波长调制的洛伦兹线型的傅里叶系数，首次得到了相应的严格解析公式。这些结果对于优化系统性能以及深入研究波长调制光谱和对数光谱具有重要意义。 对常用的比值方法和对数方法的噪声进行了理论分析和实验研究。实验发现对数方法的噪声低于比值方法2-3个数量级。理论上对这一改善进行了讨论，得到了相应的公式，公式计算的结果与实际吻合得很好。 分析讨论了光源功率调制对波长调制光谱的扭曲，推导了基本关系，给出了直观的解释，并进行了相应实验研究。 本文的另一个主要内容是利用柚子光纤开展了微结构光纤传感应用的研究，得到了以下的主要结果： 为了提高气体进出柚子光纤空气孔的速度，分别采用化学腐蚀方法、机械磨抛和飞秒激光脉冲烧蚀三种工艺，进行了了光纤侧面开孔的实验探索，获得了一定的工艺经验。 对柚子光纤的近场分布进行了观察和研究，发现了其不同于常规多模光纤的散斑特性。采用单模－多模－单模光纤结构，测量了接收功率、光谱等基本参数随外界扰动（拉伸、弯曲、振动）的变化。对柚子光纤的散斑特性和光谱特性做出了定性的理论解释，并且估算了传输光谱的蓝移，与实测结果基本相符。研究表明，微结构光纤在应力应变传感上也有很好的应用前景。 |
| 英文摘要 | This thesis is focused on the fiber gas sensing technology and has two main aspects: the first is the application of wavelength modulation spectroscopy (WMS) in fiber gas sensor; the second is for investigating the application of microstructure fiber in gas sensing and the sensing of physical variables. In this thesis, the development of WMS has been reviewed and the principles have been introduced. The promising features of applying WMS and optical fiber technology in gas sensor have been pointed out. Taking into account the urgent domestic demanding of high quality methane sensor and the requirement of technology development in this area, a fiber methane sensor based on the principle of WMS and targeting the spectrum of Methane near 1650nm has been developed. The system is composed of LD driving circuit, temperature controlling circuit, sensor head, photo detect circuit and data processing program. The resolution by methane volume is up to 10ppm and 100 ppm when concentration is between 0-4% and above 4%, respectively. In this thesis, a series of problems existed in WMS have been studied theoretically and experimentally. The main achievements of this thesis are showing below. With some approximation, the analytic formula of even order harmonic signals varied with optical depth has been deduced, which can provide a direct insight of some properties of curves, such as the zero point and non-monotony. The formula has been proved by experimental results. The direct even order harmonic method, ratio method based on 2nd harmonic divided by the 1st and logarithmic spectrum method have been characterized and compared theoretically and the advantage of logarithmic method has been pointed out. The amplitude modulation accompanied with wavelength modulation in LD has been studied; the amplitude modulation in logarithmic method has been studied and its Fourier coefficient has been given for the first time; exactly analytic Fourier coefficients of Lorentzian function wavelength-modulated by a function with second order harmonics have been given for the first time. These analytical results can facilitate deeper insight of logarithmic spectrum of WMS and optimizing the performance of system. The noise levels of ratio method and logarithmic method have been studied experimentally and theoretically. The experiment results show that the former is 2-3 order higher than later. The theoretical explanation and corresponding formula of this improvement have been given, and the estimation results using this theory can fit with experiment well. Because of the existence of amplitude modulation of light source, the shape of WMS has been distorted. With some approximation, a direct viewing of this distortion has been brought out and the corresponding experimental study has been performed. In this thesis, the application of microstructure fiber in sensing area has been investigated by using grapefruit fiber and main results are showed below. For enhancing the speed of gas infusing into the holes of grapefruit fiber, the side access of grapefruit fiber has been performed by HF etching, polishing and femto-second laser ablating and the corresponding craft has been gotten. By observing and studying the near-field distribution of grapefruit fiber, some special properties of speckle pattern which differs from regular multimode fiber have been found. The received power and transmission spectrum of grapefruit fiber varied with external disturbance (stretching, curving, and vibration) in SMS fiber structure have been measured. The properties of speckle pattern and transmission spectrum in grapefruit fiber have been explained theoretically. The blue shift of transmission has been estimated and the result has been proved by experiment. The experimental study shows that the grapefruit fiber has very promising prospects in strain sensing. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15247]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 王允韬. 光纤气体传感技术的研究[D]. 中国科学院上海光学精密机械研究所. 2008. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。