The Study Of Optical Fiber Sensing Based On Stimulated Brillouin Scattering

In recent years, the rapid development of distributed optical fiber sensing technology, with its small size, light weight, resistance to electromagnetic interference, can be simultaneously measured temperature of the optical fiber along the information. The traditional discrete couldn’t have the advantages completely. The distributed optical fiber sensing technology is widely used in structural health monitoring, oil and gas pipeline monitoring, security cable monitoring, aerospace and other fields. It can also effectively reduce the loss of life and property of the people. Thus, the fully distributed fiber optic sensing technology has broad application prospects.The distributed optical fiber sensors based on initial stimulated Brillouin optical time domain analysis(Brillouin optical time domain analysis, BOTDA) has a lot of system noise and requires measurement time. It causes great measurement error and destructs real-time capability. To improve the signal to noise ratio and real-time data collection of system, in theory, we propose using the Simplex coding and wavelet transform combining technology to enhance system performance.This paper studies the working principle of BOTDA system and could analysis the mechanism of stimulated Brillouin scattering and the numerical solution of the three-wave coupling equations. Further, the theoretical fitness analysis of scattering spectrum and temperature measurement of system is performed.Secondly, the coding theory and de-noising performance of the S-coding techniques combined with Wavelet de-noising technology is analyzed. It is introduced into a conventional three-wave coupling equations system based on BOTDA. This chapter numerically simulates that, the interference is added in 470 m of 500m-fiber, In the case of distinguishing the varying scramble of the signal, a combination of techniques to distinguish the interference signal only uses 31-order coding, and it takes 45.1673s; however, the single S-coding technology needs 255 steps, and it takes 4439.7244 s. Therefore, the combination of S-coding and wavelet de-noising technology can significantly reduce the signal processing time.Finally, the author builds the experiment platform and programs PC interface of optical fiber sensing system with Labview, while can control the microwave signal source with automatic sweeping, FPGA that generates pulse modulates continuous light by electro-optic modulator(electro-optic modulator, EOM) and triggers data acquisition card to begin collecting data. The collected data will be displayed and saved. The data of PC interface is analyzed, while we conclude that the BOTDA fiber sensing system can monitor the variation of temperature.