Design Of Distributed TDM Multiple-point Strain Sensing High-seed Data Acquisition Syste

With the rapid development of China's economy and science,health monitoring of construction engineering structure has been paid more attention to the whole community.The monitoring of structure strain is the most effective health monitoring means.Among many different methods,FBG(fiber bragg grating)has been developed rapidly and applied widely by virtue of such advantages as high sensitivity,strong anti-interference ability,multiplexing and safety & reliability.Therefore,this paper is focused on the design of the strain measurement system by FBG.In the course of widely-applied wavelength-division multiplexing(WDM)technology,multiplexing capability of WDM is limited by its own principles and existing equipment.Therefore,in order to achieve more application of FBG sensors,time division multiplexing(TDM)is adopted and a high-speed data acquisition system for multiple-point strain sensing by distributed TDM is designed in this paper,and the simulation and optimization for FBG optimum peak reflectivity and initial operating point of laser were analyzed,respectively.A sensor network model is built with five FBG sensors with the same specification and series topological structure by series topology.With oscilloscope as the core of data acquisition unit,a software system is designed by LabVIEW software and possessed with such functions as oscilloscope communication,signal filtering,data storage and reading and signal processing,and thus relationship between the stress and pulse peak voltage of FBG reflected is obtained through the monitoring system based on oscilloscope data acquisition card.Aimed at strain measurement,a calibration system is designed by spectrum analyzer,and a mathematical model of FBG is obtained indicating the relationship of the reflected pulse peak value and strain,and thus to achieve the measurement from stress to strain via oscilloscope data acquisition card based on TDM.In addition,the sensitivity of sensor system and linearity of measurement datawere analyzed,which validated the feasibility of the OTDM(optical time division multiplexing)technology system.The experimental results showed that the high-speed data acquisition system by distributed TDM multiple-point strain sensing can effectively accomplish the strain measurement and improve the multiplexing root number of FBG,which will provide a new design scheme for safety monitoring of large-scale construction engineering structure.