The Multi-peak Spectrum Feature Extraction Technology Research Of BOTDR Distributed Optical Sensing Systems

The measured information can be monitored in real-time by distributed optical fiber sensing technology in continuous space and time along the path of the fiber, and this gives it a huge and growing field to play on. Because of its characteristics of high measurement precision, long sensing distance and good real-time performance, the distributed optical fiber sensing technology based on Brillouin scattering has become into the mainstream technology in the field of optical fiber sensing. Aiming on the problems of spatial resolution and measurement accuracy in distributed optical fiber sensing system, the details of this paper’s research are as follows:Firstly, this paper expounds the types of fiber scattering, discusses the generated mechanism of spontaneous and stimulated Brillouin scattering light in fiber, studies response characteristics and quantitative relation between Brillouin scattering spectrum parameters and the change of temperature and stress, analyzes classification and characteristics of Brillouin scattering signal detection technology, and the main performance of Brillouin Optical Time Domain Reflectometry(BOTDR) system has been introduced in this paper.Secondly, for the high precision and multi feature extraction of center frequency shift on multi-peak Brillouin scattering spectrum, this paper proposes a new fitting algorithm for multi-peak Brillouin scattering spectrum, namely MCDM-PSO-LM algorithm. This algorithm uses the principle and properties of multi-criteria decision-making, locates the positions of every peaks on multi-peak Brillouin scattering spectrum accurately, and fits each peak separately. Finally it will get the complete version of multi-peak Brillouin scattering spectrum. The simulation results show that this algorithm can improve spatial resolution of the system effectively.Thirdly, this paper introduces the basic concepts and its combination rules of D-S evidence theory, and on the basis of the above, a new combination rule of D-S theory evidence has been proposed. This rule can verificate and optimize the feature extraction algorithm of multi-peak Brillouin scattering spectrum, finally it will get the exact value of each center frequency shift on multi-peak Brillouin scattering spectrum, and improves the measurement accuracy of BOTDR system.Finally, this paper introduces the whole structure of the system, introduces the parameters of several important modules and its function in this system, obtains the multi-peak Brillouin scattering spectrum under the condition of experiment, and uses the MCDM-PSO-LM algorithm to proceed the curve fitting, eventually its result is extraordinary ideal.