Research On Signal Detection And Processing Technology Of Brillouin Temperature Measuring Instrument

Distributed optical fiber Brillouin sensing technology is a new sensing technology developed in recent years.It has the advantages of high measuring precision, high sensing distance and so on, and it can also measure the temperature and strain distribution at the same time,so it is very suitable in the harsh environment of large engineering structure health monitoring, it has a very important application prospect.In this paper, based on the principle of BOTDA technology, the signal detection and processing technology of Brillouin temperature measuring instrument is studied deeply and systematically.Put forward using acousto optical and electro-optical combining frequency shift method, solves the existing based on electro-optic shift frequency BOTDA technology principle exist on both sides of the band offset problem of the pump energy.Design of signal detection, processing and control circuit software and hardware based on industrial control computer as the core,The circuit design includes a program controlled narrow pulse circuit and a photoelectric detection circuit which is composed of a FPGA and a high speed amplifier,in which the program controlled narrow pulse circuit can be controlled by the computer output arbitrary pulse width of the narrow pulse, the minimum pulse width of 5ns;the photoelectric detection circuit is composed of a Ⅰ/Ⅴ conversion circuit, a signal amplifying and filtering circuit and a voltage conversion circuit, and the pulse width is 10ns, and the intensity of the light pulse signal which is less than-50dBm is detected. Signal processing using the sampling data pretreatment, BOCAX integration, wavelet transform and other methods to improve the measurement data of the signal to noise ratio.The nonlinear least square method is used to fit the measured data, and the distribution temperature data are calculated by Brillouin spectrum at last.Experimental device of distributed optical fiber Brillouin temperature measurement system is built,through the experimental reach temperature resolution of 1℃, the spatial resolution of 1m.