| In recent decades,China has entered a period of rapid development,and various types of infrastructure have emerged,such as urban skyscrapers,large data centers,road tunnels,etc.For these complex infrastructure,once a fire occurs,it may cause incalculable losses.Therefore,a complete and effective fire warning management system for comprehensive,comprehensive,and real-time temperature monitoring of infrastructure is very urgent.In response to the above requirements,this article has built a distributed optical fiber temperature measurement system using optical fiber as the temperature sensor,which has the function of long-distance,large-scale,and real-time online monitoring of environmental temperature.In addition,optical fiber has advantages such as high temperature resistance,corrosion resistance,electromagnetic interference resistance,and intrinsic non electrification.Therefore,this temperature measurement system can also replace traditional electrical temperature sensors to achieve temperature measurement in complex environments.However,currently,the Raman distributed fiber optic temperature measurement system still faces issues such as high cost,low signal-to-noise ratio,and low spatial resolution.In response to these issues,this article has done the following work:1.Analyzed the temperature demodulation theory and positioning theory based on Raman distributed fiber optic temperature measurement system.From the perspective of system theoretical requirements and cost,the system architecture was constructed using relevant hardware modules.2.This article self-developed an FPGA data acquisition system for a distributed fiber optic temperature measurement system.The system was designed using Verilog language to achieve data acquisition,cumulative average filtering,off chip DDR3 SDRAM data storage,and gigabit Ethernet data interaction.3.In order to achieve a higher signal-to-noise ratio of the backscattered Raman scattering signal of the temperature measurement system,this paper adopts a combined algorithm of cumulative averaging and VMD-SVD to denoise the signal.The optimal solution for the decomposition layer values and effective rank order S values of the VMD-SVD algorithm was obtained through simulation experiments.The VMD-SVD algorithm with the optimal parameters was used to compare the denoising performance of Raman backscatter signals with EMD,VMD,and EMD-SVD algorithms,verifying that the VMD-SVD algorithm has the best denoising effect.Finally,the average backscattered Raman scattering signal accumulated by the temperature measurement system will be processed through VMD-SVD denoising to achieve the optimal denoising effect of the actual signal.4.In order to improve the spatial resolution of the distributed fiber optic temperature measurement system without changing the system hardware,this paper uses a self-developed low sampling rate FPGA data acquisition system from the original system,and designs and implements a high sampling rate distributed fiber optic temperature measurement system using Verilog language.This design adopts the FPGA acquisition system with a sampling rate of 50 Mhz in the original system,which effectively improves the sampling rate of the temperature measurement system to 200 Mhz.Therefore,the spatial resolution of the temperature measurement system has been changed from 2m to1.5m,with an improvement rate of 25%.5.This article developed the upper computer software of the temperature measurement system using C # language under the Winform framework using Visual Studio 2019.Polynomial interpolation method and temperature measurement accuracy fitting correction method were used for fiber dispersion and temperature sensitivity issues,respectively.Temperature gradient experiments showed that the above algorithm improved the temperature measurement accuracy of the temperature measurement system from 2 ℃ to 1 ℃.Finally,a one week temperature measurement was conducted on two temperature measurement points of the system,and the high stability of the system was verified through the 700 frame temperature measurement curves obtained. |
