Study On Gas Sensor With Optical Fiber In Atmospheric Monitor

In this dissertation, the optical methods on atmospheric monitoring in the world are analyzed. Absorption spectrum analysis is still a key method, but it is a defect that long reliability of the cell is poor. In order to improve the reliability of the cell, means of constructing the cell based on right angle prism and the corner cube are proposed. The principle of the cells and the transmission rules of probing light are analyzed in detail. The measurement equations based on the right angle prism and the corner cube are established. Photo-electronic signals processing circuit is designed according to frequency spectrum analysis and system theory. Correlation method is adapted in order to reduce the background noise. A way of automatic adjusting the sensitivity of the optical fiber sensor is proposed in atmospheric monitor. More attention are paid on the applications of the sensor to test atmospheric extinction coefficient, visibility and methane consistency. A new method is brought forward to measure atmospheric extinction coefficient with different sensitivity and shear-time. The limit to dirtiness on the surface of the cell may be relaxed. The sensor system is employed in the monitoring of formaldehyde in room. The sensitivity is increase while the sampling time is decreased. The influence of the thermal deformation cased by the environment to the sensor's performance in real time monitor is analyzed. A method to reduce the effect of thermal deformation is presented and a way for auto-collimation is put forward.The sensitivity of the fiber atmospheric sensor based on the constructions of right angle prism and corner cube can be conveniently adjusted. The cell is not sensitive to the environmental influence and is reliable for long time operation. It can be used in real time monitor system. The stability of the cell based on the corner is better than that on the right angle prism. But the former has less sensitivity adjustment range than that of the latter because of the different mechanical construction.