The Study On Embedded FBG Distributed Sensing System For Dual-measurement Of Temperature And Strain

This subject has studied and designed a distributed optical fiber sensing system for the structure health monitoring of the building. The embedded optical fiber sensor can be used conveniently in reinforced concrete structure of most buildings now, and this designed sensors can simultaneously measurement of temperature and strain. In order to adapt to large volume and wide measuring scale of the structure characteristics, the distributed optical fiber sensing system has been designed based on FBG sensor using the combination technique of WDM and SDM, and this sensing system has strong operability which can be determined according to the actual needs, it’s convenient in practical engineering application. At the same time, a FBG demodulation system has been designed, is good for the FBG sensor signal demodulation and distributed system information collection.This paper firstly introduces the structure health monitoring of buildings and the optical fiber sensor. The development history and the current application of the optical fiber sensor are summarized in the construction measurement, the main method of the distributed optical fiber sensing system has been comprehensively analysised, there are OTDR and OFDR for distributed optical fiber sensing system of the light scattering.The FBG sensor technology is relatively mature and widely used. The FBG sensing principle of temperature and strain has been studied in this paper; The method of the FBG distributed sensing technology is proposed, this technical method is optical multiplexing technology mainly including WDM,TDM and SDM, which is analysised the application of the actual engineering measurement; The FBG wavelength demodulation of direct method, filtering method and interference method has been presented and studied.Every specific part of distributed optical fiber sensing system has been studied in this paper. First, a embedded FBG sensor is designed within the concrete, not only can which simultaneously measure temperature and strain with the double grating, but also solves the strain problem of temperature compensation, and the sensor is packaged with the steel tube and double epoxy resin; Second, a new method of FBG wavelength demodulation is proposed. In this method, the STM32semiconductor controls the tunable laser module and InGaAs PIN photodiode; In the end, the FBG distributed sensing system is designed with the technology of WDM and SDM, which has high stability and strong practicability in practical engineering.The FBG demodulation system has been tested in the experiment, it has measurement accuracy and the resolution of1pm. The temperature and strain characteristics of the embedded FBG sensor has been tested in the experiment, the temperature and strain resolution are0.1℃and0.5με. The FBG distributed sensing system based WDM and SDM has been tested in the experiment. Every optical channels multiplexes different kinds of FBG sensors in the distributed sensor network. The system is relatively simple,convenient practical and strongly maneuverable in the the actual project.