Research on Effective Separation Method of Multi-Molecule Composite Absorption Spectrum Based on Modulation Technology

‘Carbon Peak And Carbon Neutrality’ is an important goal of China's current economic development. Therefore, it is crucial to detect the greenhouse gases such as CO
2
, and the main products in the process of carbon emissions such as H
2
O and CO. In this paper, two lasers with wavelengths of 1570 nm and 1985 nm are selected to realize the simulation verification of the simultaneous measurement method of H
2
O, CO
2
and CO. A multi molecule composite absorption spectroscopy separation method is proposed in this article. Based on tunable diode laser absorption spectroscopy technology, the concentration information of H
2
O and CO
2
is obtained sequentially by fitting the normalized second harmonic signal after deducting the background. Then, using this as the background, it is substituted into the composite absorption spectrum, and the spectral information of CO is obtained through sub-channel deduction, achieving effective separation of the absorption spectrum. The simulation results show that the maximum absolute deviations of the three gases are 0.21%, 1.83% and 2.72%, respectively, which provides strong support for the engineering application of wavelength modulation technology to simultaneously measure multiple components.