Abstract: In order to effectively evaluate the information transmission characteristics of infrared gas sensing system, to serve the teaching needs of basic concepts such as information entropy in the course of “information theory” and to promote the full integration of teaching and scientific research, the infrared gas sensing system is treated as a channel, the actual concentration is treated as an input information source and the measured concentration is treated as an output information source. The information theoretical model of the infrared gas sensing system is established. The analysis method of information transmission efficiency of infrared gas sensing is proposed. Firstly, aiming at the wavelength modulation spectroscopy technique, the functional simulation of laser modulation, gas absorption, photoelectric conversion and harmonic extraction are carried out. According to the relevant principles of Shannon‘s information theory, the mathematical expressions of transfer matrix, source entropy and mutual information are presented, and the characteristics of information transmission efficiency and the minimum resolvable concentration interval of the sensing system are analyzed. Based on the actual measurement results of long-time stability of the sensor, the variation characteristics of the information transmission efficiency and the minimum resolvable concentration interval of the sensor system with the integration time of the system are analyzed. The presented information measurement method integrates the basic knowledge of information theory and expands the scientific research and application case of infrared gas sensing system based on wavelength modulation spectroscopy, which is innovative. The practical application shows that the information measurement method of infrared gas sensing system meets the experimental teaching needs of information theory and the scientific research needs of wavelength modulation spectroscopy, and has achieved good teaching and scientific research application results.

Key words: teaching and researching system, information theory, noise entropy, wavelength modulation spectroscopy, tunable diode laser absorption spectroscopy