基于多模二极管激光吸收光谱的氧气浓度测量

可调谐二极管激光吸收光谱技术(TDLAS)具有高灵敏度、高选择性和快速响应等特点，被广泛应用于环境监测、工业生产监控和生物医疗等众多领域。为克服传统TDLAS技术成本高以及长时间工作过程中由于中心波长偏移造成的稳定性差等问题，提出了利用多模二极管激光关联光谱和谐波检测技术实现氧气浓度在线监测的研究。以Fabry-Perot(FP)激光器为光源，通过对760 nm附近氧气分子的多条吸收谱线的探测，实现了对氧气浓度的测量。输出光束被分光系统分成两路信号，分别经过样品池和测量池，双路接收采集含有气体浓度信息的光信号送后级处理，通过测量信号和参考信号之间的相关性及比例关系对氧气浓度进行反演，其中关联光谱技术和谐波检测技术被用于提高系统稳定性和信噪比。结果表明，在1个大气压条件下，系统的探测极限为280 ppm·m，对同一样品在30 min内的30次连续测量的标准偏差为0.056%，表明了系统良好的稳定性。该系统在软、硬件上的设计可以满足氧气的在线监测，且系统稳定性高、装置简单、易用，便于复杂环境应用。

Measurement of Oxygen Concentration Using Multimode Diode Laser Absorption Spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) is a widely used technique for high sensitivity, good selectivity and fast response. It is widely used in environment monitoring, industrial process control and biomedical sensing. In order to overcome the drawbacks of TDLAS including high cost, poor stability and center wavelength shift problem. A multi-mode diode laser system based on correlation spectroscopy and wavelength modulation spectroscopy (TMDL-COSPEC-WMS) was used to measure O₂ concentration near 760nm at the 1%～30% range of near room temperature. During the experiment, the light is splitter into two beams, respectively through the sample and measuring cell, two receiving optical signal collection containing gas concentration information sent back stage treatment, invert the oxygen concentration through correlation and ratio between measured signal and reference signal, the correlation spectroscopy harmonic detection technique is used to improve the stability of the system and the signal to noise ratio. The result showed that, there was a good linear relationship between the measured oxygen concentration and the actual concentration value. A detection limit of 280 pmm﹒m in the 1 atmospheric which approved of the same sample. A continuous measurement for oxygen with the standard deviation of 0.056% in ambient air during approximately 30minutes confirms the stability and the capability of the system. The design of the system includes soft and hardware can meet the needs of oxygen online monitoring. The experimental device is simple and easy to use, easy to complex environment application.