出了一种多模二极管激光吸收光谱测量系统，该系统以发射谱稳定的多模二极管激光器作为光源，结合长程吸收技术和谐波检测技术，通过对1570 nm CO分子多条吸收谱线的探测，实现了对CO浓度（即指体积分数）的测量。实验在室温和20.265 kPa(即0.2个标准大气压)条件下进行，通过配置不同的CO-N2混合气体，对一系列不同浓度的样品气体进行了测量。测量前通过9种不同浓度的CO-N2混合气体对系统进行定标，获得定标公式，用得到的定标公式进行CO浓度的反演。结果表明，在CO体积分数低于10%的情况下，浓度测量值与已知值一致性较高，平均偏差为2.57%；通过对CO体积分数为0.5%的混合气体测量信号进行分析，得到系统对CO的探测极限为3.03×10-5。该系统可以满足CO的在线监测，且稳定性高、灵敏度高，实验装置简单、易用。

A multi-mode diode laser absorption spectroscopy system is built by using a multi-mode diode laser with stable emission spectrum as light source. Combined with the long path absorption and harmonic detection techniques, concentration (volume fraction) measurement of CO is realized by detecting multiple absorption lines near 1570 nm. The experiments are carried out at room temperature and 20.265 kPa (0.2 standard atmospheric pressure). By configuring different CO-N2 gas mixtures, a series of different concentrations of sample gases are measured. The system is calibrated by using nine kinds of CO-N2 mixtures with different concentrations. The calibration formula is obtained and used to inverse CO concentration. The results show that in the case of volume fraction below 10%, the consistency between the measured and known values is higher, and the average deviation between them is 2.57%. By analyzing the mixed gas measurement signal of 0.5% volume fraction, the system detection limit of CO is 3.03×10-5. The system can meet the on-line monitoring of CO, and it has high stability and high sensitivity. The experimental device is simple and easy to use.