以空芯光子带隙光纤作气室的全光纤甲烷检测

以空芯光子带隙光纤(PBGF)作为气体传感部件,分析了PBGF内部导光机制及其甲烷在纤芯缺陷区域的扩散特性,设计多段PBGF连接耦合弯曲成圈在一起组成的传感气室,构建一套全光纤甲烷浓度检测系统。引入分布式反馈光纤激光器的调控机制,采用谐波检测技术,实现了整体对全光纤甲烷浓度检测系统的优化。经实验,可证明由该传感部件组成的全光纤甲烷浓度检测系统能够实现甲烷浓度在线实时检测,并且甲烷浓度与相对强度成良好的线性关系,其线性度可达99.8%。     

气体滤波相关技术在红外甲烷监测系统中的应用

针对空气痕量气体中甲烷含量低、吸收弱,在非分散红外甲烷检测系统中噪声干扰大的问题,本文提出了利用气体滤波相关检测技术去除背境噪声干扰来提高检测能力的方法.该方法依据气体对红外辐射的特征吸收和相关运算的原理,结合了先进的气体滤波技术和相关检测技术,实现了对微弱光谱信号的调制和检测,最后实现了对浓度的反演,从而达到了甲烷气体实时、快速在线检测目的.试验结果表明,系统有10 ppb的测量精度.     

甲烷气体多点光纤传感系统的研究

基于气体在其特征吸收波长下光的吸收随浓度变化的机理和空分复用技术,复用多个气体吸收型光纤传感器,并通过谐波检测技术对微弱信号进行处理,设计了一套甲烷气体多点光纤传感系统。研究表明,该传感器的精确度为 5ppm,精确度和稳定性均可满足实际要求,仪器可在多场合进行多点在线测量。     

光谱吸收式光纤甲烷气体传感器及其信号处理方法

基于气体在其特征吸收波长下光的吸收随浓度变化的机理,通过对甲烷气体吸收光谱的分析,提出了一种光谱吸收式全光纤甲烷气体传感器及其系统。该系统以1300nm波段的DFBLD作为光源,波长响应范围为1100~1900nm的高灵敏度、低噪声的InGaAsPIN作为光电探测器,利用锁相放大器对传输信号进行相敏检波,采用一次谐波反馈光源注入电流、二次谐波与一次谐波的比值作为系统输出的谐波检测技术对微弱信号进行处理,使得系统达到很高的灵敏度。研究表明,该传感器的灵敏度达到10ppm,精确度和稳定性等性能指标均可满足甲烷气体检测要求。     

用LED作光源的Fabry-Perot光纤甲烷气体传感器的研究

利用Fabry Perot腔的选频特性 ,考虑与光纤的低损耗窗口相一致和价格等因素 ,采用价廉的1 3μm波段的LED作为光源 ,实现了PZT对Fabry Perot腔的正弦调制。对甲烷气体浓度进行谐波检测 ,检测灵敏度可达 10× 10 - 6 ,大大提高了灵敏度和稳定性     

红外气体检测技术在天然气安全生产中的应用

从检测原理和检测技术上,对应用在天然气生产过程中,检测易燃易爆或有毒气体的红外气体传感技术进行了分析。采用红外可调谐激光光谱技术（TDLS）结合波长调制技术（WMS）,对天然气管道传输中的甲烷气体泄露进行远距离检测,有效克服了长距离检测中激光照射到地表物体之后存在的严重光散射和光吸收所带来的系统误差。分析了含硫天然气井喷或泄露时,硫化氢气体的红外检测方法。在空气中水蒸气和甲烷气体的干扰下,通过分析硫化氢、水蒸气和甲烷红外吸收谱线的分布情况,选择出可用的硫化氢吸收谱线。同时根据谱线交叠隋况建立起二元一次方程组,能够在不同浓度甲烷气体干扰下同时计算出甲烷和硫化氢的浓度．     

调制式光纤甲烷气体传感器的研究

利用Fabry-Perot腔的选频特性，考虑与光纤的低损耗窗口相一致和价格等因素，以价廉的1300nm波段的LED作为光源，实现了PZT对Fabry-Perot腔的正弦调制；对甲烷气体浓度进行谐波检测，检测灵敏度可达10ppm。研究表明，该传感器灵敏度和稳定性大大提高。     

波导式气体吸收池时间响应特性

波导式光学吸收池在气体浓度测量等领域有广泛的应用前景.本文理论分析了在普通扩散环境和压差环境下波导式光学吸收池的时间响应机理和特性,并搭建了相应的传感系统,优化系统结构进行了实验验证.通过对低浓度的甲烷和甲苯气体的测量实验,验证和修正了响应时间的理论模型.实验结果表明,优化系统在可以大幅降低响应时间的同时,保持较高的灵敏度,为波导式吸收池的设计与优化提供了重要的参考.     

差分吸收式光纤甲烷气体传感器的研究

设计一种新型的利用吸收法实现快速测量气体浓度的光纤传感器,该传感器基于比尔-朗伯定律,得到气体浓度与光强度变化的关系。利用差分吸收技术设计双光路双通道结构,消除了光源的不稳定性和光电器件的零漂。同时,设计了锁相放大器,抑制了噪声,从而提高了该传感器的灵敏度和测量精度。     

高性能虚拟数字示波器的研究

目的 介绍了基于虚拟仪器设计软件Labview开发的高性能虚拟数字示波器系统，方法 由数据采集DAQ、接口总线、硬件驱动程序和虚拟软件数字示波器构件构成了虚拟示波器系统，并应用在光纤气体浓度检测系统中。结果与结论 在实际光纤气体浓度检测系统中的应用表明，该虚拟数字示波器很好实现检测信号的处理，并具有良好人机界面和性能。     

Mid-infrared gas sensing using a photonic bandgap fiber

We demonstrate methane sensing based on Fourier transform infrared spectroscopy using a hollow-core photonic bandgap fiber guiding in the mid-infrared and idler pulses from a femtosecond optical parametric oscillator. Transmission measurements are presented for several fibers, and sensing is demonstrated using a fiber whose bandgap overlaps the methane fundamental absorption lines. The gas filling process of the air core is described, and qualitative methane concentrations measurements to 1000 ppm (parts in 10(6)) are reported. Operation down to 50 ppm based on our current experiment is predicted.     

基于正交偏振光的瓦斯浓度传感器研究

介绍了瓦斯浓度传感器系统的基本原理,提出了基于正交偏振光的差分吸收式瓦斯浓度检测模型,建立了瓦斯浓度传感器的数学模型,设计了传感器系统结构以及光路和气室结构,并对传感器进行了实验研究.传感器系统利用起偏器将两束不同波长的单色光转变为正交偏振光,然后让这两束正交偏振光同时通过检测气室,最后用渥拉斯顿棱镜将两束单色光分开,...     

低浓度氟化氢标准气体的FTIR分析方法研究

提出一种基于FTIR的氟化氢标准气体分析方法,使用其特征吸收区域(波数4100～4300cm-1)进行定量分析。通过稀释方法形成120、 100、 80.0、 60.0、 40.0、 20.0μmol/mol共6个浓度点的氟化氢标准气体,并对其重复性、标准曲线线性、检出限进行考察。结果显示：在20.0～120μmol/mol范围内仪器响应值与标气浓度呈线性,R2为0.9979; 各浓度点的重复性介于0.34%～1.1%之间; 检出限约为2.04μmol/mol。     

一种高灵敏度光声光纤SO2气体传感器的研究

基于气体光声效应原理，研究了一种高灵敏度光纤SO2气体浓度传感器。用染料激光器作为激励源，激励出光声信号，采用光纤位移传感器测量光声信号。设计了光学长程装置以提高光声腔的灵敏度。用此装置测量SO2气体浓度，给出了实验数据并对结果作了分析。     

He-Ne and cw CO2 laser long-path systems for gas detection

This paper describes the design and testing of a laboratory prototype dual He-Ne laser system for the detection of methane leaks from underground pipelines and solid-waste landfill sites using differential absorption of radiation backscattered from topographic targets. A laboratory-prototype dual cw carbon dioxide laser system also using topographic backscatter is discussed, and measurement results for methanol are given. With both systems, it was observed that the time-varying differential absorption signal was useful in indicating the presence of a gas coming from a nearby source. Limitations to measurement sensitivity, especially the role of speckle and atmospheric turbulence, are described. The speckle results for hard targets are contrasted with those from atmospheric aerosols. The Appendix gives appropriate laser lines and values of absorption coefficients for the hydrazine fuel gases.     

Near-infrared hollow waveguide gas sensors

The development of a hollow core waveguide (HWG) gas sensor in combination with a fast and compact near-infrared (NIR) spectrometer is presented. The spectrometer operates in the spectral range of 1200-1400 nm and may thus be applied for the detection of gas-phase analytes providing NIR absorptions in that spectral window such as, e.g., methane. Since mid-infrared spectroscopy in combination with HWGs has already been successfully demonstrated for probing hydrocarbons in the gas phase, the present study investigates the achievable sensitivity in the NIR spectral regime. Methane has been selected as an exemplary analyte due to the fact that it shows strong absorption features in the mid-infrared (mid-IR) fingerprint area, but also overtone bands in the NIR. Since the HWG simultaneously serves as a miniaturized absorption gas cell and as an optical waveguide for NIR radiation, a compact yet optical and cost-efficient sensor device was established providing an interesting alternative in target sensing for mid-IR devices. The achieved limit of detection (LOD) was 5.7% (vol./vol.) methane for a 9.5 cm long HWG, 1.6% (vol./vol.) methane for a 39.1 cm long HWG, and 1.3% (vol./vol.) methane for a setup using a 77.4 cm long HWG, which provides the most practical HWG dimensions among the three investigated setups. Limit of quantitation (LOQ) values were calculated at 20.1% (vol./vol.) methane, 8.7% (vol./vol.) methane, and 5.6% (vol./vol.) methane, respectively.     

Gas concentration monitoring system for small and medium sized coal mines based on gas sensing detection and single chip control

This paper is aimed at the actual conditions of disaster caused by gas in small and medium-sized coal mines. A new gas concentration monitoring system for coal mines is developed on the basis of gas-sensing detection and single-chip control. The monitoring system uses the tin oxide as the main material of N-type semiconductor gas sensors, because it has good sensitive characteristics for the flammable and explosive gas (such as methane, carbon monoxide). The QM-N5-semiconductor gas sensor is adopted to detect the output values of the resistance under the different gas concentrations. The system, designedly, takes the AT89C51 digital chip as the core of the circuit processing hardware structure to analyze and judge the input values of the resistance, and then achieve the control and alarm for going beyond the limit of gas concentration. The gas concentration monitoring system has many advantages including simple in structure, fast response time, stable performance and low cost. Thus, it can be widely used to monitor gas concentration and provide early warnings in small and medium-sized coal mines.