光纤收发的空气差分吸收光谱测量方法研究

环境污染气体监测是防治大气污染的前提条件。污染气体的监测方法中，光谱分析方法具有原理和结构简单、响应速度快、精度高等优点。差分吸收光谱法利用气体分子在紫外-可见光谱范围的特征吸收来测量其浓度含量，是环境气体监测领域的典型光谱分析方法。根据差分吸收光谱的测量原理，提出光纤收发一体测量结构，将该结构应用于空气质量监测中。氙灯光源经耦合透镜耦合后进入入射光纤，经望远镜系统准直后出射，经过被测气体之后，由位于被测气体另一端的角锥棱镜反射后沿原路返回，再次经过望远系统汇聚，携带被测气体的信息经出射光纤传入光谱仪。根据该方法研制了样机，采用SO₂，NO₂标准气体对样机进行标定，并应用样机对大气中的污染气体进行现场监测。实验结果表明，该方法能够满足空气质量监测要求。

Air Pollutants Study by Differential Optical Absorption Spectroscopy with Transmit-Receive Fibers

The differential optical absorption spectroscopy system is presented to monitor air pollutants, such as SO₂, NO₂, etc. The system employs a reflective telescope to collimate light source and focus absorbed light. A combined transmitting and receiving fiber bundle is set to the focus of a concave mirror. A Xenon lamp works as the light source. The light is coupled into the transmitting fiber, and then collimated by the reflective telescope system. After absorbed by the pollutants, the light is reflected by a pyramid mirror far away the telescope. Then the absorbed light is incident on the concave mirror the second time, and focused on the focal plane again. The receiving fiber induces the light which carries the information of the measured gas into a spectrometer. We can get the concentration of the pollutants by DOAS algorithm. Experimental results show that the proposed method can be adopted to measure some pollutants in air quality monitoring.