Research On Key Technologies Of Raman Distributed Fiber Temperature Sensing Based On Photon Counting

At present,Distributed Fiber Temperature Sensing(DTS)is widely used in various industries and has become a research hotspot in the field of fiber optic sensing.There is a trade-off between bandwidth and sensitivity of conventional photodetectors,and it is difficult to simultaneously achieve high spatial resolution and high temperature resolution.In recent years,the rapid development of the quantum information industry has provided a new vision for DTS technology.The combination of single photon detection and DTS technology for temperature sensing is an emerging field.The high sensitivity,low time jitter and low dark count rate of single photon detectors and other advantages can effectively make up for the shortcomings of traditional detectors.This paper aims to design a DTS system with high spatial resolution,high temperature resolution and fast response capability,and conducts related research around photon counting and DTS.The main contents include the following parts:1.The classical theory and quantum theory are used to analyze the DTS system based on Raman scattering in detail,and the advantages and disadvantages of three demodulation methods are compared and analyzed.Combined with the Raman anti-stokes single channel demodulation method,Photon Counting-Raman Distributed Temperature Sensing(PC-RDTS)system is proposed.2.The PC-RDTS detection model and Monte Carlo simulation method were proposed to explore the influencing factors of spatial resolution and temperature resolution of PC-RDTS system.Finally,it is determined that the spatial resolution of the system is mainly determined by the laser pulse width,the superconducting nanowire single photon detector and the time jitter of the time-digital converter,and the temperature resolution is mainly affected by the signal to noise ratio and temperature sensitivity.3.Theoretical analysis is conducted on polarization effects and Raman polarization related gain,proposing three polarization effect suppression methods,and constructing a PC-RDTS system based on polarization controller(PC)orthogonal method and polarization maintaining fiber method for experimental research.The results show that the spatial resolution of PC-RDTS based on polarization maintaining fiber method obtained by the10-90 and half height full width methods is 28 cm and 38 cm,respectively.It achieves a temperature resolution of 2.23 ℃ within 5 seconds at a distance of 100 meters,and a temperature resolution of 0.66 ℃ within 60 seconds.Under the same experimental conditions,PC-RDTS based on PC orthogonal method can achieve a temperature resolution of1.90 ℃ within 60 seconds,indicating that the polarization maintaining fiber method has better suppression effect on polarization effects and better sensing performance than PC orthogonal method.4.The algorithm model based on total variation and alternating direction multiplier method was used to denoise PC-RDTS.The results showed that the algorithm can achieve a temperature resolution of within 0.10 ℃ within 5 seconds,while satisfying fast convergence.This enables the system to have both fast response capability and high temperature resolution,enhancing its application prospects.