Research And System Integration Of Distributed Optical Fiber Raman Temperature Sensing System

Distributed Fiber Optic Raman Temperature Sensing System is widely used in aviation,petroleum,electric power,coal mine,water conservancy,transportation,chemical industry,military industry,ships and construction and other fields because of its distributed temperature measurement,high precision,corrosion resistance,strong anti-interference ability,light weight,small size and low cost advantages.Distributed Fiber Optic Raman Temperature Sensing System measures the temperature information in the environment according to the temperature effect of fiber backward Raman scattering,and then locates the fiber through optical time domain reflectometry(OTDR),which can measure the temperature distribution field in the whole fiber link continuously in real time.This paper develops the system design and implementation of Distributed Fiber Optic Raman Temperature Sensing System.The main work is as follows:(1)Distributed Fiber Optic Raman Temperature Sensing System overall scheme design.After reading a lot of literature and theoretical analysis,this paper determines the Distributed Fiber Optic Raman Temperature Sensing System design scheme based on Raman scattering Stokes(Stokes)and Raman scattering anti-Stokes(anti-Stokes)signal demodulation.The key technologies of the program are analyzed.(2)Complete the development of pulsed laser.Firstly,the pulse driver is designed,then the characteristics of the seed light source are studied and improved.Firstly,1550 nm seed light sources and 980 nm pump drivers are designed,which are the key components of the pulsed laser,and then the 1550 nm seed light is amplified based on the main oscillating power amplification(MOPA)structure to complete the design and implementation of the pulsed laser.The pulse laser frequency and pulse width are adjustable,and the frequency is set to 10 k Hz and the pulse width to 20 ns.When the 980 nm pump power is 350 m W,the peak output power of the pulse laser is 25 W.When the pump power is 450 m W,the peak output power of the pulse laser is 36.295 W.(3)Complete the development of the signal acquisition and processing system.Raman optical signal acquisition is realized through the designed dual-channel avalanche photodetector and FPGA-based dual-channel high-speed acquisition card with a sampling rate of 100 MHz,a storage depth of 16384 12-bit data,and accumulation times of up to 16384 times.The high efficiency linear accumulation method is used to process the data,improve the signal-to-noise ratio and reduce the running time,and effectively restore the weak Raman signal.(4)System integration and testing.A human-computer interface based on QT software is designed in this paper in order to realize Distributed Fiber Optic Raman Temperature Sensing System integration.Then,the pulse laser,signal acquisition and processing system and the host computer software system are integrated to realize the development and test analysis of the Distributed Fiber Optic Raman Temperature Sensing System.Experimental results show that the Distributed Fiber Optic Raman Temperature Sensing System spatial resolution is 2 m;the sensing distance is 918 m.The temperature accuracy is 1.3 °C;the theoretical sensing distance is 12 km,when the sensing distance is 4.986 km,the single measurement time is 1.385 s,and the cumulative average of 16384 times is 2.204s.