Research On Locating Range And Accuracy Of Distributed Fibers In Mines

China is a large coal producer with high casualties.At present,the equipment for personnel positioning monitoring in coal mines is an active electronic sensor.After the mine accident occurs,the power supply needs to be cut off in time.This type of equipment cannot work normally.Therefore,accurately obtaining the position information of the trapped people in the underground without electricity,and accurately positioning the trapped people in the underground is the key to improving the rescue rate of the trapped people in the mine accident.It has become a research hotspot in the field of underground coal mine personnel positioning at home and abroad.This paper first introduces the system structure and positioning method of several typical interference and scattering distributed optical fiber sensors,and it provides a theoretical basis for long-distance,high-precision disturbance positioning.The analysis shows that the distributed optical fiber sensing technology is suitable for the harsh environment of coal mine underground.Applying it to the underground coal mine positioning problem can be used as the focus of future research and an important way of underground emergency rescue.Secondly,this paper adopts a Φ-OTDR(Phase-Sensitive Optical Time-Domain Reflectometer)distributed optical fiber sensing system,which can complete the positioning of underground personnel and adapt to the complex environment of coal mine underground.In order to improve the system positioning accuracy problem,in the process of setting the light source and sensor head and signal demodulation data processing,the light source with narrow line width and low frequency drift characteristics is selected to accurately obtain the vibration signal.The experiment monitors different vibration points.The results show that compared with the traditional OTDR distributed optical fiber sensing system,the system adopted in this paper is more reliable and has higher positioning accuracy.Thirdly,for the problem of low positioning accuracy and short sensing distance in the positioning of the distributed optical fiber positioning sensing system for coal mines,ADMZI(Asymmetric Double Mach-Zehnder interferometer)distributed optical fiber sensing technology using distributed feedback laser and dense wavelength division multiplexing is proposed.The sensing distance of distributed fiber positioning is expanded,and the positioning accuracy is improved.Through experimental analysis,the ADMZI structure is superior to the traditional DMZI in remote sensing and it has higher sensitivity.Significant improvement in sensing distance and positioning accuracy.Finally,it is aimed at the special environment of underground coal mines and the characteristics of the positioning algorithm,an improved cross-correlation delay estimation algorithm based on SVD(Singular Value Decomposition)is proposed,which combines SVD with cross-correlation time delay estimation.The simulation results are based on ADMZI positioning experiment.The simulation results show that the proposed algorithm has higher positioning accuracy,better performance and wider application prospect than traditional direct cross-correlation delay estimation algorithm.