Study On The Simultaneous Temperature And Strain Sensing Based On The Brillouin Scattering

The distributed fiber sensor has the merits of the normal fiber sensor. In addition, itcan get the continuous time and space information of the measurand along the fibersimultaneously. It can measure the information of strain, temperature, vibration anddamnify at every point along the fiber and realize long length and distributed sensing.Among all the distributed fiber sensing system, the distributed fiber sensing systembased on Brillouin scattering can realize simultaneous temperature and strain longlength, big dynamic range, high accuracy sensing. It has aroused wide concern of theresearchers at home and abroad.Combining with the BOTDA system in our group, we investigate the simultaneoustemperature and strain sensing with the methods of double fibers and doublewavelengths. This thesis includes the following work and innovations:(1) The sensing principle of Brillouin scattering is analyzed in detail, including therelation of Brillouin frequency shift and power versus temperature and stress. Thepractical sensing functions are obtained.(2) The BOTDA system based on microwave electro-optical modulation isintroduced in details. The key device selection, signal acquisition and analysis areanalyzed and discussed. Based on this system, the Brillouin frequency shift temperatureand strain coefficients calibration system is built. The Brillouin frequency shiftcoefficient matrix of G652D, G657, G657B3and bending fiber under the1536nm,1550nm and1559nm pump wavelengths are calibrated.(3) The method of polynomial fitting is proposed. It can shorten processing timewith high frequency resolution.(4) Distributed simultaneous temperature and strain sensing based on the methodsof double fibers and double wavelengths is proposed. The accuracy of these twodamceoctuuhbroladecs fy i ibises r2ds..e5r℃ive da.n Bd athseed s tornai nth aec ccuarliabcrya tiesd coefficient matrix, if the accuracy of theBrillouin frequency shift of the BOTDA sy5s1teμmε ocfa tnh ea tmtaeinth o0d.1oMf Hdoz,u bthlee temperature wavelengths...