| The research condition of Brillouin distributed optical fiber sensing technology is introduced in this thesis. The dependences of Brillouin shift and intensity on temperature and strain are investigated theoretically. A Brillouin distributed sensing system for simultaneous temperature and strain measurement with heterodyne detection is proposed. Based on the performance measurement of electro-optic modulator, the working parameters of the system are optimized. The waveform of backscattered light in time domain is measured using acoustooptic modulation. According to the characteristics of Brillouin signal and based on Labview7.1, weak signal with high-frequency is extracted using synchronous averaging algorithm. The simulation is conducted using the Morlet Wavelet Transform to detect the envelope of simulated Brillouin signal. Unknown parameters in Brillouin scattering model are estimated using Lorentz fitting based on Levenberg-Marquardt (LM) algorithm, which is verified the LM algorithm to be practical for precise fitting of Brillouin spectrum. |
PDF Full Text Request