The Digital Detection System Of The Fiber Optic Oxygen Sensor

The fiber optic sensing technology is a kind of new sensing technology developed rapidly in the 1980s. With the development of fiber technology, spectroscopy, information engineering and computer technology, there are increasing interests in the development of fiber gas sensor in the recent years. Nowadays the fiber optic sensing technology has been used in many fields such as chemical analysis, biology detection and polluting environment detection. The technology of the fiber optic gas sensor is the hotspots and difficulty in the fiber optic sensor.In the thesis we study the system of the detection of the fiber optic gas sensor by detecting the fluorescence. It measures the density of oxygen by detecting the life-span of the fluorescence quenching. The so-called fluorescence quenching is a kind of physics or chemistry process that the fluorescence material has chemical or physical reactions with certain substance is selected here. It has the advantage of good stability of fluorescence, long life span and the strong quenching effect. We demonstrate the feasibility and superiority in the digital phase-locked detection applying in the life-span of the fluorescence quenching in the base of the phase-locked phase theory. By the former experiment, we know that the fiber optic gas sensor with the pulse light of the blue light LED can emit the steady fluorescence. So we can detect the density of oxygen through. But the optic fiber coupling effects in the light way reduces the intensity of the fluorescence. So the PIN in the system for optic and electric changing just gets the faint fluorescence. It is difficult to detect the intensity of the fluorescence in such condition. The project detecting the oxygen density by measuring the life-span of the fluorescence quenching has better advantages such as the more sensitive, the better anti-jamming, the more system stabilization, the better dynamic area than by measuring the intensity of the fluorescence quenching.We design the digital phase-locked loop applying the method designingdigital circuitry from the top down. We design the circuitry by the VHDL in the MAXPULSII software environment. We validate the circuitry function in the emulator. What is more, we devise the software in order to communicate among the FPGA, the SCM and the PC. We compile the program in order to realize the change between the phase and the density of oxygen in the VB6.0 environment. The program has the good interface between people and computer and it is operated very simply.The detecting system in the fiber gas sensor has the comparability. So the system has better flexibility. The study in fiber oxygen sensor refers to the other gas sensor.