基于中空波导光纤的CO2气体传感器稳定性的研究  

Stability of CO Gas Sensor Based on Hollow Waveguide Fiber

作　　者：张倩倩 吴涛[1] 孙城林 叶谌雯 王梦宇 范乐康 刘洋 何兴道[1] Zhang Qianqian;Wu Tao;Sun Chenglin;Ye Chenwen;Wang Mengyu;Fan Lekang;Liu Yang;He Xingdao(Key Laboratory of Nondestructive Testing,Ministry of Education,Nanchang Hangkong University,Nanchang,Jiangxi 330063,China)

机构地区：[1]南昌航空大学无损检测教育部重点实验室,江西南昌330063

出　　处：《光学学报》2021年第15期219-226,共8页Acta Optica Sinica

基　　金：国家自然科学基金(61865013);江西省自然科学基金(20203BBG73039,20192BBH80019,20202BABL212011);科技部重点研发项目(2018YFE0115700);南昌航空大学研究生创新基金(YC2019062)。

摘　　要：激光器受到诸如热波动和机械振动等低频因素扰动时会发生激光波长漂移和光强波动,进而会影响系统的测量精度。使用波长为2.73μm的分布式反馈(DFB)激光器作为探测光源,搭建一套基于中空波导光纤的CO2气体传感系统,该系统采用CO2的三次谐波吸收信号(3f)来实现激光器的稳频,再利用谐波信号来反演CO2的浓度。实验中对标准CO2气体进行长时间测量,分别利用二次谐波(2f)、稳频条件下的二次谐波(2f-lock)、二次谐波比一次谐波(2f/1f)、稳频条件下二次谐波比一次谐波(2f/1f-lock)4种测量方法对系统进行分析。2f-lock条件下得到的系统测量精度为0.001255,比2f条件下的提高了2.4倍;2f/1f-lock条件下得到的系统测量精度为0.00138,比2f/1f条件下的提高了2.34倍。2f/1f-lock方法得到的系统稳定时间最长,为210 s,探测极限最低,为4.24×10^(-5)。综合分析,2f/1f-lock是4种方法中最优的。在2f/1f-lock条件下,对测得的数据进行Kalman滤波,得到滤波后系统的测量精度为0.0002786,相较于未滤波前提高了4.95倍。When a laser is disturbed by low-frequency factors(e.g., thermal fluctuations and mechanical vibrations), laser wavelength drift and light intensity fluctuations occur, which affect the measurement accuracy of the system. In this study, a 2.73-μm distributed feedback(DFB) laser is used as the detection light source and a set of CO2 gas-sensing system based on hollow waveguide fiber is built. The proposed system uses the third harmonic absorption signal(3f) of CO2 to achieve the frequency stabilization of the laser and then uses the harmonic signal to reverse the concentration of CO2. In the experiment, the standard CO2 gas is measured for a long time and the system is analyzed according to four measurement methods: second harmonic(2f), stabilized second harmonic(2f-lock), second harmonic ratio first harmonic(2f/1f), and stabilized second harmonic ratio first harmonic(2f/1f-lock). The system measurement accuracy obtained under the 2f-lock condition is 0.001255, which is 2.4 times higher than that under the 2f condition. The system measurement accuracy obtained under 2f/1f-lock condition is 0.00138, which is 2.34 times higher than that under 2f/1f condition. It can be seen that the 2f/1f-lock method has the longest stable time of 210 s and the lowest detection limit of 4.24×10^(-5). Comprehensive analyses reveal that 2f/1f-lock is the most optimal among the four methods. Kalman filtering is performed on the measured data under the 2f/1f-lock condition, and the measurement accuracy of the filtered system is 0.0002786, which is 4.95 times higher than that before the filtering.

关 键 词：传感器 激光吸收光谱 稳频技术 谐波技术 二氧化碳 

分 类 号：O436[机械工程—光学工程]