为了在矿井中实现快速、 便携式的甲烷浓度检测, 同时系统还具备高灵敏度及长的工作周期, 设计了基于半导体激光器模式跳变的差分光学光谱吸收法, 建立了井下甲烷浓度无线检测系统。 系统利用调制电流使半导体激光器的输出波长发生模式跳变, 从而获得了两个相近波长的激光, 其中一个在甲烷的特征吸收峰上, 而另一个基本不被吸收。 实验中将两束光分别照射被测气室时, 两束光的光强之差代入比尔朗伯定律即可求解气室内的甲烷浓度。 实验结果显示, 调制电流从20.0 mA增大到60.0 mA过程中, 输出波长在电流达到48.3 mA时发生跳变, 由1 650.888 nm改变为1 651.020 nm。 通过HITRAN光谱数据库可知, 波长1 650.888 nm位置可作特征吸收峰, 而波长1 651.020 nm适合作参考波长。 在此基础上, 对密闭容器内标准浓度的甲烷气体进行测试, 采用H-BD5GD410-HC型便携式甲烷检测仪的测试数据作对比。 两种检测结果相近, 但随着浓度不断地增高, 该系统的检测误差相对平稳, 略优于甲烷检测仪。 系统的检测误差均低于0.050%, 在不采用昂贵的锁相器、 检相电路的条件下, 实现了精度优于0.10%的井下甲烷浓度检测。

In order to detect rapid, portable concentration of methane in the mine, meanwhile, the system includeed a high sensitivity and a long working period, designed differential optical absorption spectroscopy method based on mode-hopping of semiconductor laser, and established wireless detection system for concentration of methane in the mine. Output wavelengths of the semiconductor laser occurred mode-hopping by modulation current of the system, so it obtained the two wavelengths close to the laser, and one is on the characteristic absorption peak of methane, while the other is not substantially absorbed. When the two beams of light were illuminated test chamber, methane concentration of the gas chamber was solved by Bill Lambert law with the difference of the light intensity between the two beams. Light source used DFB single mode semiconductor laser from Japan Anritsu company. Experimental results show that, when the modulation current increased from 20.0 to 60.0 mA, output wavelength occurred mode-hopping when the modulation current reached 48.3 mA, and output wavelength changed to 1 651.020 nm from 1 650.888 nm. By HITRAN spectrum database, it showed that the position of the wavelength 1 650.888 nm can be used for characteristic absorption peaks, while the wavelength 1 651.020 nm was suitable for reference wavelength. On this basis, the standard concentrations of methane gas was tested in the sealed container, test data of the system was compared to the H-BD5GD410-HC portable methane detector. Test results of the system and the H-BD5GD410-HC portable methane detector were similar, but with the constant concentration increased, the detection error of the system is relatively stable, slightly better than the portable methane detector. Detection error of system were less than 0.050%, under the conditions that there were without the use of expensive phase lock or inspection phase circuit, to achieve the accuracy of better than 0.10% concentration of methane detected in the mine.