The Fiber Bragg Grating And The Sensing Study On The Sensor Encapsulated By The Alloyed Steel

Fiber Bragg grating is a new passive device in recent years,the sensor based on the fiber grating receieved more and more attention. The FBG sensor is made by using the average refractive index and the characteristics that the Grid cycle is sensitive to outside parameter,we turn the change of outside into the moving of Bragg wavelength.It is a kind of wavelength modulation fiber sensor,which has many advantages such as good dependability,anti-interference in electromagnetis -m,light in weight ,anti-corrossion,working in the mal-condition,high-reconvera bility , distributed sensing and so on. It has the wide applications in the fields of experimental mechanics,strain analysis and safely monitoring the engineering structure.The main contents of this paper are followed as: 1. Development of FBG sensor encapculated by alloyed steel The core of fiber grating is thin and brittle so that it must be encapsulated in the actal application.The senor encapsulated by the alloyed steel can not only protect the grating ,but also measure the strain by monitoring the change of the fiber grating. 2. Research on sensing characteristics of FBG sensor encapsulated by alloyed steel. We have measured the strain based on an equai-intensity beam and contrast between the measuring result of fiber grating and traditionally strain foil of ecletic resistance.The experiment showed the encapsulated sensor didn't chang the strain-sensitivity of fiber grating and also we got the measuring range ,sensitivity and resolution of the sensor.The temperature experiment indicated the encapsulation does not chang the temperature sensing characteristic of fiber grating. 3. Research on FBG sensor encapsulated by alloyed steel under the loading experi –ment of the concrete girder We measur the strain of concrete girder by fixing it on the concrete girder and contrast between the the measuring result of fiber grating and traditionally strain foil of ecletic resistance.It proves the FBG sensor applied in the real engeering. 4. FBG pressure enhanced-sensitive machanism The pressure sensitivity of the FBG is very low,this paper gives several pressure enhanced-sensitivity mechanisms with low and high pressure and their sensitivity expression.It provides some reference models to design the utility-type FBG pressure sensor in the future.