Study On Key Technology Of Distributed Fiber Temperature Sensor Based On Raman Scattering

Distributed optical fiber sensor system is a new sensor technology which can realtime detect the changes of physical parameters along the sensor fiber,which has unique advantages over traditional sensor systems.Distributed optical fiber temperature sensing system has the characteristics of anti-electromagnetic interference,long detection range,high reliability,etc.Hence,it has good practical and economic value in the fields such as oil pipelines,smart power grids and subway tunnels.In the existing Raman optical fiber temperature sensing system,the overall spatial resolution is limited by the insufficient conversion speed and bandwidth of detection circuit.Moreover,most of the system uses genetic data acquisition card to collect data,and an upper-computer to complete the denoising,demodulating and other processing.The deficiency of data sampling and processing speed in this technology is the main reason for the poor real-time performance of the current system.In view of the above problems,this paper studies the key technologies of each module in the system,and a distributed optical fiber temperature-sensing system is designed to realize distributed measurement and real-time display along the sensor fiber.Starting from the scattering principle and the temperature effect of spontaneous Raman scattering,this paper expatiates the working mechanism and positioning principle of distributed fiber temperature sensing system.Then,a detection circuit with low-noise,high-gain and broad-band is developed,in which the InGaAs avalanche photodiode and integrated operational amplifier have been used.Finally,according to the characteristics of the signal and its noise,the linear cumulative mean algorithm is adopted.Based on high-speed data acquisition card and FPGA hardware development platform,a highspeed signal acquisition and processing module of "hard acquisition and hard processing" is accomplished.The experimental results show that the system can reach spatial resolution of 1m and temperature accuracy of ±0.5? within two kilometers detection range.And it has fast signal-processing speed,strong real-time performance,high stability and reliability.The outcomes have certain reference value and guidance significance to the engineering application of temperature measurement.