Design And Optimization Of Distributed Optical Fiber Brillouin Sensor

As the critical parts of the information-access process, sensors have played a more and more important role in information science field. With the development of optical fiber technology, sensing technology which combines with optical fiber technology has been proposed and propulsive. Owing to the advantages of small volume and low dissipation, the measurement capability of long distance and high precision, as well as its immunity to electromagnetic interference and resistance to corrosion, distributed fiber sensing technology has become a research hotspot and attracted much attention from scientific institutions, colleges and developing departments of companies. Distributed optical fiber sensor systems based on the stimulated Brillouin scattering, using the knowledge of optics, electronics and signal processing, utilizes the function relationship between Brillouin frequency shift, intensity and the sensing information to realize the measurement of strain and temperature. Compared with other distributed sensors, Brillouin sensors have many advantages such as higher signal intensity, longer test distance, et al. Therefore, they have a good application prospect in the construction industry, the rail transit, the power systems, the water industry, the oil industry, the geological monitoring and the aerospace business.This thesis focused on the theory of distributed optical fiber Brillouin sensor, finished the system design and the system building. Moreover, according to the problem existing in ventilating system, we proposed some methods to optimize system design.1. On the basis of related theory of Brillouin scattering, we introduce the principle of distributed optical fiber Brillouin sensing systems. And the Brillouin optical time domain analysis (BOTDA) technology and microwave frequency-sweep technique are studied.2. The structure of the light path and the circuit, as well as the device selection are designed and confirmed, and the performance parameters of the devices have been introduced detailedly. Some technical indicators of this system such as spatial resolution, time resolution and measuring accuracy have been evaluated.3. Experimental system is established. The measured parameters of the devices as well as the modulation of probe waves and pump waves are presented. Then we find the proper microwave frequency to observe the phenomenon of Brillouin gain, and get the three-dimensional Brillouin gain spectrum when the microwave sweeper is scanning.4. Design and implement the data acquisition scheme based on FPGA to solve the chaos in additive process. A novel method using incident probe waves normalization to eliminate the impact of microwave source power fluctuation is proposed. And contrast experiment between conventional and new method were carried out to validate the benefit of the novel method.