The Study Of Distributed Optical Fiber Sensing Based On BOTDA

Since the 1970 s,with the rapid development of optical fiber technology and optical communication technology,distributed optical fiber sensor as the fusion of the two derivative types sensing technology has gradually stepped into all aspects of the national economy as well as people's livelihood.It also holds an important practical status in the field of structural health monitoring.Apart from the advantages of traditional optical fiber,such as small volume,light quality,electromagnetic resistance,radiation resistance,corrosion resistance,the distributed optical fiber sensor also integrated the information transmission and sensing.This way has greatly reduced the sensor technology's costs in energy consumption.Also,in many difficult artificial detections,it has showed its strong application abilities,so it gradually gets the favor of the scientific researchers.The traditional distributed optical fiber sensing system that based on stimulated Brillouin scattering optical time-domain analysis(Brillouin optical time domain analysis,BOTDA)technology needs a lot of measuring time and exists great noise.So the measurement result may produce significant error,which may seriously affect the efficiency of the sensor measurement.For the problem of noise and long measuring time,this paper puts forward the signal processing method which combined the cumulative average and wavelet transform to deal with it.Through combining labVIEW and MATLAB,this method has greatly reduced the measuring time and improved the SNR of the system.This paper makes a basic introduction on the distributed optical fiber sensing technology based on BOTDA subject.And the paper makes a detailed introduction on the theory of optical fiber sensing technology based on three kinds of scattering effect,especially for the distributed optical fiber sensing technology based on brillouin scattering of microeconomic theory.Then,for the BOTDA optical fiber sensing system to be studied in this paper,the paper makes theoretical researches from the aspects of stimulated Brillouin scattering theory,sensing mechanism,stimulated Brillouin scattering effect threshold and the relationship between temperature and strain and Brillouin frequency shift,etc.And the photoelectric device that to be used and data acquisition card are discussed in detail.Base on that,the paper designed the BOTDA sensing measurement system of this experiment.According to the basic structure of BOTDA system,this paper introduces and analyzes the main parameters influencing the performance of the system,including measuring accuracy,the spatial resolution,sensing distance and time,etc.Finally,the paper introduces the used to stimulate the stimulated brillouin scattering effect of the pulse modulation of the production process,gives examples of FPGA program.At the same time,the combined technology of labVIEW and MATLAB is used to design the cumulative and average Wavelet transform of the data processing module.All these have helped to realize the frequency sweep,acquisition and signal processing in the integration of BOTDA measurement and control systems.In order to verify the effectiveness of the system and the timeliness of the data processing methods,this paper has carried out the temperature measurement test and the distributed measurement test based on the experimental system respectively,and achieved good experimental results,which laid a solid foundation for the following system optimization.