Design And Optimization Of Distributed Optical Fiber Raman Temperature Measurement System

Since the advent of optical fiber,optical fiber sensing technology has also come into being.The distributed optical fiber sensing technology is becoming more and more mature.It has become a new research hotspot in the whole technological field.In distributed optical fiber temperature measurement system(Distributed Optical Fiber Temperature Measurement System,DTS),optical fiber is not only a porter for signal transmission,but also a mission of sensing element.Compared with point type sensing system,it has the advantages of optical fiber itself: light weight,small volume,corrosion resistance,electromagnetic interference and high bandwidth,so it will shine in the field of sensing.In early 1970 s,the first foreign began to research on the DTS system,China also started exploring in 80 s,with the ongoing,continuous optimization of system performance,place and application of more and more,such as temperature monitoring long-distance oil and gas pipeline,tunnel,dam construction,maintenance platform with the monitoring,the bridge safety monitoring.This paper is from the perspective of OTDR theory research,through detailed analysis and comparison of the principle of measuring different scattering light,finally chose to build the distributed optical fiber sensor measurement system based on Raman scattering,and optimize the system performance parameters,the specific content of the work are as follows:1.In the aspect of basic theory,expounds the principle of spatial localization of optical time domain reflectometer,and starting from the two angles of quantum mechanics and classical electromagnetism,temperature measurement principle of Raman scattering is studied in detail,analyzes the Brillouin scattering measurement system,temperature measurement system and the Rayleigh scattering optical fiber grating temperature measurement technology's advantages and disadvantages,finally the stokes and anti-stokes Raman scattering signal as temperature sensitive signal.2.In terms of system hardware design,through analyzing the performance of the system,we finally selected high speed pulse laser with high central wavelength1550 nm,high isolation wavelength division multiplexer,In GaAs photoelectric detector,high-speed data acquisition card and multi-mode sensing fiber.The function,performance and advantages and disadvantages of each module are introduced,which lays a theoretical foundation for the optimal selection of the system hardware toreduce the error loss.Design software in the system,first on the choice of programming language,we decided not to use Verilog or VHDL language to program,but the use of storage and computing ability of computer hardware,based on the use of Microsoft card Visual C++6.0 development environment for further development in data acquisition.3.In the design of system software,using Microsoft Visual C++6.0 to develop the data acquisition software of data acquisition card,and PC to demodulate the signals of Stokes and anti Stokes signal display,and completed the anti-stokes and stokes signal as compared to the temperature sensitive temperature display and alarm signal.4.In terms of system performance optimization,cumulative averaging algorithm and wavelet denoising theory are applied to denoising and optimization of stokes and anti-stokes signals.The average temperature error of temperature measurement is1.02 ?.The optical fiber scattering compensation algorithm is studied to reduce the effect of dispersion on the positioning accuracy of the system.The final experimental results show that the optimized resolution error temperature reached 0.54 ?,the spatial resolution of 2m,and the utility of Raman type DTS system is verified by experiments.The results show that the system can carry on the 8000 m cable insulation material in the length of aging investigation and fire warning.