| The research state of Brillouin-based distributed optical fiber sensing technology is introduced. The principle of Brillouin Optical Time-Domain Reflectometer (BOTDR) sensing system based on heterodyne detection and its microwave down-conversion part has been introduced detailly. The spectrum and output power range of Brillouin scattering in the photodetector has been analyzed and calculated theoretically, as well as the input signal range of the data acquisition card. One time frequency down-conversion microwave detector scheme has been determined the realization of the down-converter in subject ultimately, and the main performance features of the scheme have been designed. The system performance has been simulated by the Advanced Design System (ADS)-a simulation software is used in radio frequency and microwave, and the rationality of the technical performance features design has been confirmed. Finally the low noise amplifier (LNA) part of this scheme has been designed detailly, and optimized and simulated by ADS. The performance features of LNA which finally obtained are superior to the system design before. |
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