Study On Spectrum Absorptive Fiber Optic Gas Sensors

Optical fiber gases sensing technology is a novel discipline, which has a wide applicable prospect in industrial production, environment monitoring and medical science. In recent years, with the development of optical fiber sensing technology, the research of optical fiber gas sensors has been seriously regarded all over the world. The signal detected by optical fiber gas sensors is carried by light wave, which has a small interference on surroundings. With their qualities of no electricity on sense organ and blast proof in essence, they can be used as on-line detection of flammable and exploding gases in industry.In this thesis, we have studied spectrum absorptive optical fiber gas sensors. Each kind of gases has inherent absorptive spectrum. When a light source's emitted wavelength is corresponding to the gas's absorptive wavelength, resonating absorption will happen. And the absorptive intensity is related to the gas's concentration. The gas's concentration can be known by the detection of light absorptive intensity. Two kinds of projects were provided in the paper. And experimental research was done on the detection of acetylene. Our main works are:1. The research status about spectrum absorptive optical fiber gas sensors at home and abroad was studied and analyzed. Different methods had their own advantages and disadvantages. Novel experiment schemes were designed to improve the precision and applicability of gas sensors.2. Through analyzing the gas's absorptive spectrum, two experiment schemes were provided on the basis of existing light sources on the market. They were separately Optical Fiber Gas Sensor Based on DFB LD and Optical Fiber Gas Sensor Based on Tunable Fabry-Perot Cavity. The issue of the first plan was harmonic detection. While the innovation of second plan was several kinds of gases can be detected by the demodulation of Tunable Fabry-Perot Cavity.3. Two projects' light path and circuit were designed separately. Their PCBs (Print Circuit Boards) were executed. Hardware's performance was optimized by circuit adjustment while the sensor's signal was processed by computer. And the task of detecting gases concentration was finished.4. Experimental research was done based on these two plans. Take the example of acetylene; the response curve of acetylene gas was plotted. Other gases concentration can be detected like this.5. Comparing these two plans: Optical Fiber Gas Sensor Based on DFB LD has the advantages of high detecting precision, quick response rate and good stability. But a light source can detect only one kind of gases. Optical Fiber Gas Sensor Based on Tunable Fabry-Perot Cavity can be used to detect several kinds of gases. But its cost is high at the present time.