Study On Infrared Absorption CO Fiber Optic Sensor

Carbon Monoxide is a poisonous gas which is flammable and explosive, it brings a great damage to industry safety production. In order to realize the CO detection, equip a flammable gas sensor, find the danger of accident immediately, take a saving measurement is very essential. We use infrared technique to detect CO, not only overcome the shortage of usual detect measurement, but also have many virtues such as good selectivity, continuous analysis and quick response, it is more suitable to the mine environment, so using the infrared technique to the CO detection has an important meaning and a good application foreground.In this thesis, we use the spectrum absorption method, design a kind of fiber optic sensor. We use the CO as the experiment gas, confirm the spectral absorption, and find out the spectra characteristics which are fit for low-loss transmission window of optic fiber. Distributed Feedback laser diode (DFB LD) is used as a light source and light source modulation harmonic measurement is presented in this paper. The ratio of the fundamental and second harmonic signal can be used as output for eliminating the interference owing to the light power changing.The main works of this thesis include:1. Study on spectrum absorption measurement principle of optical fiber gas sensor. Analysis sine wave and triangle wave modulation harmonic measurement and compare the two ways. At last, simply introduce the technology of source modulate.2. Select CO absorption apex, choose DFB LD as the light source, InGaAs PIN photodiode as the detector, based on the wavelength and measuring method that are selected.3. According to the theoretical analysis, we design a optical fiber sensor system based on DFB LD. The feeble signal is obtained by phase locked amplifier. The noise will be restrained in maximum degree, and the ratio of signal to noise will be raised.4. Using the CO as the sample gas, do some experiments and get the concentration measurement curves, valuate the system, and supply some data for the following research.5. Improve on controlling the light sour's working temperature, because the changing of DFB LD surface and kernel temperatures will affect the light source's centre wavelength.