Development Of Distributed Optical Fiber Raman Temperature Measurement Device Based On FPGA

With the rapid development of China's economy,the process of industry and urbanization has been accelerating.In order to meet the needs of industrial and urban modernization,the number of large-scale infrastructure projects such as industrial buildings,subway tunnels,urban comprehensive galleries,and large-scale buildings is increasing,and the prevention of fire safety is also paid much attention.However,because of its wide space and bad environment,it is difficult to achieve distributed on-line detection of environmental temperature or fire by traditional means.Therefore,there is a need for a distributed temperature on-line detection technology suitable for a wide range of harsh environments.For temperature detection in a wide range of space and complicated environment,the traditional detection technology has many problems such as high maintenance cost,limited measurement range,and sensitive element corrosion.Optical fiber sensing technology has the advantages of intrinsic safety,anti-electromagnetic interference and corrosion resistance,which provides a new idea for distributed temperature sensing detection in long range and wide range.In this paper,a distributed optical fiber temperature sensing detection technique(DTS),which uses optical fiber as a temperature sensing unit and a signal transmission medium,is studied.In order to solve the problem that the measurement period time is long in long distance distributed temperature detection,the fast data acquisition and processing scheme based on FPGA is proposed,which accumulates data while collecting.A fast distributed fiber-optic thermometer is developed to provide a fast on-line temperature detection technology for security in a wide range of space and complex environments.It has the advantages of easy maintenance,large measurement range,essential safety,anti-electromagnetic interference and corrosion resistance.The major research work in this paper includes the following aspects.(1)Utilizing FPGA's great advantages in high-speed data acquisition,processing,and improving the real-time performance of the system,a fast DTS system overall plan based on FPGA data acquisition and processing is designed.According to the overall goal of the system and the technical goals of the research,a comprehensive analysis of the key parameters of the various key devices is given.Then the appropriate key devices are selected to set up the experimental platform.(2)DTS temperature measurement theory and DTS location theory are analyzed.In view of the low signal-to-noise ratio of the scattered signal,the advantages and disadvantages of commonly used methods of averaged de-noising and wavelet de-noising are analyzed.In order to ensure the accuracy of the system and achieve good real-time performance,the method of using cumulative averaging in conjunction with wavelet transform is proposed,and the feasibility and effectiveness of the method are verified by experiments.(3)Combined with the functional requirements of DTS system,the overall structure of the software system is designed.According to the overall structure of the software,the functions of starting and stopping control of the software,reading the scattering signal,demodulation and display of temperature,threshold alarm,storage and query of data are completed.(4)Combined with DTS software system and hardware system,the integration of DTS system prototype is completed.Then the performance of DTS prototype is tested through experiments.In the 10 km long measuring distance,the temperature is measured from-25°C to 200°C,the measurement accuracy of ±1°C is achieved,the positioning accuracy of ±2m and measurement time is 2.031 s,and for the measuring distance of 2.6km,the measurement time is 1.063 s.Compared with existing DTS products,the real-time performance of measurement has been improved.