Research On Temperature And Pressure Sensing Characteristics And Static Ice Pressure Detection Based On FBG Ring-down Cavity

Many rivers and lakes in high latitudes such as North China and Northeast China will freeze in winter.The static ice pressure accompanying the ice generation and dissipation process will not only cause damage to hydraulic structures,but also bring hidden dangers to the lives and properties of surrounding residents.The static ice pressure is the main control load during the design and construction of hydraulic structures.Due to the special environment of detection and the inherent complexity of ice,there is still a lack of real-time,effective sensing theory and continuous detection method for obtaining high-precision static ice pressure during ice generation and dissipation.In response to the above problems,this paper combines the principle of fiber Bragg grating(FBG)sensing combined with fiber ring cavity ring-down spectroscopy to establish a theoretical model of pressure and temperature sensing,and builds an FBG ring cavity ringdown sensor system based on FPGA pulse modulation,and carries out an experimental research to verify the simulation results of the theoretical model.The results show that the experimental results are consistent with the theoretical simulations.At the same time,the sensing system is used to detect the static ice pressure and during the ice generation and dissipation process,the evolution law of static ice pressure caused by the ice layer to the boundary is explored.The paper mainly is completed by the following works:(1)Sensing principle of the FLRDS and the fiber grating sensing principle are expounded.Theoretical model of the pressure and temperature sensing based on the FBG ring-down cavity are established which is carried out by numerical simulation to explore the pressure and temperature attenuation characteristics of the FBG ring-down cavity,spectral response characteristics,the best coupling ratio and the best reflectivity of FBG;(2)Pulse laser source is designed based on the FPGA and FBG ring-down cavity sensing system is built.Experiments on the pressure and temperature of the system were conducted,and the difference between the reciprocal of the ringdown time and the initial ring-down time was linearly related to the pressure and temperature.The experimental results agree well with simulation results.The experimental researches also demonstrate the sensing system exhibits the excellent stability and repeatability under low temperature conditions;(3)The static ice pressure test experiment and analysis.Based on the FPGA,FBG ring-down cavity sensing system is utilized to measure the static ice pressure to side wall of ice in the process of temperature decreasing from 10? to-10?and the temperature increase from-10? to 10?.