Investigation Of Bent Fiber Gratings

This thesis is devoted to research on the property of bent long-period fiber grating (LPG) theoretically and experimentally. And, for the first time, the feasible theoretical mode is presented. The optical fiber grating is a very useful fundamental element in the area of optical fiber telecommunication and fiber sensors. Bending can be an easy modulation of fiber grating抯 resonance wavelength. Numerous reports on the application of bent fiber grating can be found in the literature. However, there is no report on the theoretical analysis. In order to make further study on the property of bend fiber grating, we have done some useful work on its theory. Due to the complexity of theoretical analyze by the perturbation, the bent LPG is analyzed in predigestion. For the first time, we regard bent LPG as the bent single mode optical fiber that meets LPG抯 phase-matching condition. Based on couple-mode theory, step-index single mode fiber抯 weakly guiding theory and perturbation theory, the LPG is analyzed theoretically. With the analyzed result, we analyzed the LPGs?optical property. A method is performed in this paper to increase the strain sensitivity of the strain sensor and decrease the temperature sensitivity of the concentration sensor in bent long-period gratings with applied bending technique. The parameters of strain and concentration also are measured in the experiment. Candidate: Lu Yaodong Directed by: associate professor Hong Deming, professor Chen Zhihao...