FBG Strain Measurement And Analysis On The Surface Of A Loaded Container

At present, Fiber Bragg Grating (FBG) is one of the most potential and typical optical passive components. FBG can be immune from disturbance of light source and system attenuation, because it transforms sensing information, strain and temperature for instance, into reflecting wavelength shift, which is of the characteristic of wavelength coding. Besides, FBG is of good characteristic such as good reliability, immune from fire, electromagnetic interference and corruption. It can also be constructed as an FBG network in series to realize distributed sensing by Wavelength Division Multiplex (WDM), which is impossible for traditional sensors. FBG sensor therefore has wide prospect in use in huge constructions and dangerous situations, such as the dam, building, bridge etc, especially the compressive container or pipe in oil field and mine. That is way the research and application of FBG attract more and more attention in recent years.This thesis focuses on the strain measurement on the surface of compressive container or pipe, and compared the results of FBG and traditional resistance foil strain gauges (RFSG) with theoretical strain value.This thesis first studied the characters of FBG strain sensor. By hanging weights, it researched the linear relations in quantity between Bragg wavelength and strain that is to calibrate the characters of FBG strain sensor.Secondly, the theoretical strain value of this loaded contain both in hoop and in axis is calculated.There were eight FBGs in a way of WDM to detect respectively hoop and axis strain on the surface of a hydrostatically loaded container. Nearby each FBG, there is a RFSG as a reference. Then, the responses were analyzed and compared with theoretical strain value.Considering the fiber getting thin when it is pulled, it affects the response. So a compensation measure is employed.Finally, a simplification FBG encapsulating method is used to change the complex stress into pure tensile stress, and to compare the strain response with the response from the un-simplified encapsulating FBGWe have drawn the following conclusions:1. In axis direction, taking theoretical strain value as true strain value, FBG was 6% closer than RFSG2. In hoop direction, taking theoretical strain value as true strain value, FBG was approximately the same with RFSG as 1% error.3. The strain responses of compensated tension FBG were closer to the theoretical strain value than before compensation.4. The strain responses from simplified encapsulating FBG were closer to the theory than the un-simplified encapsulating FBGThus, because the FBG is of high precision, repeatability, linearity, and sensibility, it is good for strain measurement of compressive container or pipe, in hoop or in axis directions. Introduced in this thesis, the research of compensation of tensioning FBG, and the research of simplified encapsulation of FBG, can promote the engineering application of FBG...