Study On Acetylene Optical Fiber Sensor

With the development of global economy, environment pollution has been increasingly serious. Therefore environment protection is the major research project all over the world. It is worth to mention that the study on instrumentation for gas concentration detection has been research focus in sensor technology field among many nations. Based on environment protection, the present graduate project makes use of existent theories and instrumentation facilities to develop monitoring sensor for atmospheric pollution. This monitoring sensor has widespread application prospect in environment monitoring, power system, oil and mine fields. Because of intrinsic advantages of optical fiber sensor, spectrum absorption optical fiber sensor has been the mainstream of gas concentration detection. By means of comprehension and analysis of former research achievements, the present paper presents the main reason for not high sensibility and precision of gas concentration detection and advances single-spectrum full-width modulation technology. It means that, based on the thorough analysis of the fine line type, position and correspondent line width of spectrum, sinusoidal modulation voltage is employed on piezoelectricity ceramic. With piezoelectric converse effect of piezoelectricity ceramic, the center wavelength of optical fiber grating can be modulated. The maximum peak value of C2H2 at low-loss transmission area of quartz optical fiber can be selected to conduct single-spectrum full-width scan. Meanwhile reflection spectrum intensity and transmission spectrum intensity of optical fiber grating are detected simultaneously. Thus the negative effect of illuminant vibration can be eliminated by their ratio. In the circuit design for weak signal detection, the lock-in amplifier is employed to extract quadratic harmonic. Through the ratio of linear harmonic and quadratic harmonic, the gas concentration can be measured. The present graduate project has multitude innovations as following: 1. The conception, theoretic foundation and implementation method of single-spectrum full- width modulation is advanced. 2. For the first time presented is the detection approach -U- Abstract of light intensity ratio of reflection spectrum from signal channel and transmission spectrum from reference channel of optical fiber grating. 3. The detection theory of quadratic harmonic and its correspondent lock-in amplifier technology are propounded by means of single-spectrum full-width modulation. During the development of this project, the author has been mainly engaged in the task of theoretic research, scheme design and feasibility analysis for gas concentration detection. Implementation of detection circuit and experiment of theoretic demonstration are achievements of the whole research group. The author has assisted the research group leader to complete many positive assignments. From the starting involvement to material finding and system model design, the author holds an opinion that optical fiber gas concentration detection relates to multidisciplinary knowledge. In order to develop a better detection system, there are still a lot of practical works to accomplish. The present paper advances the basic system model of C2H2 concentration detection. It has played a solid foundation and provided a valuable reference for the research of high-performance optical fiber gas sensor in the future.