The Snr Improvement Of BOTDR System Based On The EDFA With An Optical Bridge Structure

Fiber optic distributed sensors based on Brillouin Optical Time Domain Reflector(BOTDR) can measure continuous parameters in space and time domain with the merits ofhigh precision spatial resolution and long range. The paper researches on the SNRimprovement based on distributed fiber sensor of BOTDR. By using sweeping frequencyto obtain the energy of different frequency signal in the system, the paper analyzes indetailed factors limiting the performance of BOTDR. To strengthen the backscattered light,two methods need to be further researched. The article mainly includes following works:Firstly, the paper introduces the mechanism of brillouin scattering and theoreticallyanalyzes the Brillouin-based sensor. The paper gives a clear insight into direct andcorrelation detection methods and analyses the factors that affect the system SNR.Secondly, the Paper introducts the EDFA important parameters of performanceevaluation and the design and take simulation test. The Paper introduces Raman amplifierprinciple and the selection of parameter and the co-propagating pump structure.Thirdly, by making experiment on the cascade EDFAs with an optical bridge andRaman amplifier, the advantages and disadvantages of various structures are studied indetail. The paper tests the performance parameters of the preamplifier and comparesco-propagating EDFA, counter-propagating EDFA and single-stage EDFA for selecting theoptimal one. The paper analyses the effect of Raman amplifier and cascaded EDFAs.Finally, in order to determine the equipment which play an important role in thesystem stability, the system equipment is inspected and optimized. Considering SNRmeasurement method of coherent detection system, the cascaded EDFAs is used as apreamplifier in the system. The experimental results of the preamplifier show accuracy ofimproving the measuring results. The paper combine BOTDR based on electro-opticmodulator frequency shift with the two cascaded EDFAs preamplifier to strengthenBrillouin backscattering light and affirm the spatial resolution of the sensing system.