Research On Gas Sensing Based On Gas Frequency Stabilized Laser

With industrial development,air pollution has increasing influence on people's living environment and their health.Due to its high detection sensitivity,adaptability for harsh environment,and ability for long-distance transmission,optical fiber gas sensing has become the trend of the modern gas detection technology.The light source is a critical section of optical fiber gas sensing system and a broadband light source or a fiber laser can be chosen as this section.Comparatively,fiber laser is more capable to produce wavelength-stabilized and high-power output,which will greatly improve the detection accuracy of optical fiber gas sensing.In this paper,an implementation of frequency-stabilized laser light source is presented.In depth study of the principle of multi-wavelength laser,a method of multi-wavelength laser based on the combination of erbium doped fiber amplifier and semiconductor optical amplifier is proposed.Finally,The main contents of this paper are as follows.(1)A gas absorption comb filter is designed based on the principle of spectrum absorption and optical interference.A research on the principle and numerical simulation analysis of gas absorption comb filter is made.By comparing the performance of the filter at different phase and different splitting ratio,the optimal parameters of the absorption comb filter is achieved.The gas reversal spectrum through the filter is stable and does not change with temperature change.(2)By comparing the pros and cons of erbium-doped fiber multi-wavelength laser and semiconductor optical multi-wavelength laser,a novel mixed gain mechanism with a combination of EDFA and SOA is proposed.(3)The effects of the SOA driving current and the splitting ratio of the splitter on the stability of the laser output are analyzed.In a two-hour repeating scanning process,the wavelength shift and the peak power change are less than 0.006 nm and 0.4dB,respectively.(4)Gas concentration detection based on the frequency-stabilized laser is demonstrated.A gas sensing system is built based on the frequency-stabilized laser and then high-sensitivity detection of acetylene is demonstrated.Gas sensing experiments with single-wavelength and multi-wavelength laser output respectively show that the sensitivity and stability of the sensing system is good and the laser power exhibits a good linear relationship with the concentration of acetylene,and the linearity is up to 99.5%.