Study On Spectral Properties And Structure Design Of Fiber Bragg Grating Flow Meters

The measurement of flow rate is very important in processing of industrial production, for instance, in Petroleum chemical industry, medicine, energy measurement and environmental monitoring. Flow sensors are the imperative device in fluid detection and control process. It has a long term for people to measure fluid. There are many kinds of flow rate instruments, traditional mechanical flow sensors have big discrepancy and low accuracy.Fiber Bragg Grating(FBG) has comprehensive application foreground because of its advantage of simply structure, high sensitivity, width frequency wavelength, wavelength division multiplex and time division multiplex, wavelength coding except its advantage of light weight, corrosion resisting, electromagnetism resisting and using safety etc. Substantial, FBG is reflectance distribution of ultraviolet which utilize its photosensitive of fiber in the fiber core. The transmit regular pattern theory of wavelength of fiber grating and its characters of optics, mechanical, decline when heated are the base of its application in communication and sensor area. Research of these theories and characters has important guide sense for us to display performance of fiber grating components better. In according of different application required.In the topic, at first, by means of theoretical analysis of characters of reflectance of fiber grating, using fiber grating emulator based on FBG theory we can examine the affect regular pattern of temperature, strain, valid refraction coefficient of fiber grating, length of grating modulate of refraction coefficient and other correlating parameters to characters of reflectance. Then design a new type of flow rate sensor based on FBG technical which has target structure, encapsulation fiber grating in triangle sheet metal by thermal gel, deformation take place on the isosceles triangle sheet metal when shocked by fluid, the deformation make the central wavelength of fiber grating which fixed on cantilever drift. Set up experiment device, observe the transformation of wavelength by spectrograph, determine the function between flow rate and offset of central wavelength of fiber grating, establish internal relation between them, in other words, we can gain flow rate which is to be measured according to observe the variation of central wavelength of fiber grating. In order to decrease the discrepancy, the method of eliminating the temperature cross sensitive affection is researched at last. Through laboratory experiments we can measure the variation of the offset of central wavelength of FBG in different flow rate and different stress. The experiment results show that, the offset of central wavelength of FBG increase along with the flow rate increase, the relationship between them is linear; deformation take place when there is external force, the offset of central wavelength increase along with the external force increase, the relationship between them is also linear.