| The research trend of fiber-optic sensing based on BOTDR technology has been introduced with particular attention to signal processing. The sensing principle using Brillouin scattering has been analyzed and the dependences of Brillouin shift and intensity on temperature and strain have been founded. A BOTDR sensing system based on Landau-Placzek Ratio and using microwave heterodyne detection has been designed, the control scheme of the sensing system has been studied and the tunable laser and data acquisition card can be controlled by computer in LabVIEW. The digital multi-point averaging algorithm has been analyzed in detail, and the de-noising of Brillouin intensity simulation signal and acquisition signal have been achieved. The de-noising result presents that program of algorithm is correct and effective. The principle of nonlinear least square fitting based on LM algorithm has been studied and the fitting of simulation Brillouin spectrum with single-peak and multi-peak has been realized. By simulating signal processing of BOTDR system based on frequency scanning, temperature information can be demodulated correctly from detection information in 10 km fiber. |
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