Based On Acousto-optic Tunable LPFG Research

Long period fiber grating is a kind of the most important passive devices in optical fiber communications, optical fiber sensing and optical fiber lasers. This paper analyzed grating based on coupled-mode theory and segmented transfer matrix method. The analysis of Long period fiber grating coupler-mode is based on the three-layer model of the fiber and coupled-mode theory of the grating. We have analyzed in detail on the mechanism of long period fiber grating, studied the relations of related parameters, the effective refractive index, the coupling coefficient expression. Our researches provide a theoretical basis for the cascaded long period fiber grating, which is suitable for computer simulation.According to the coupled-mode theory, this thesis analyzes the various parameter s of long-period fiber grating. Research work was done both on various simulation analysis and some basic experiments. For side lobe suppression and wavelength of long-period fiber grating, simulation and experimental results are analyzed separately. Meanwhile, the thesis sums up the applications in the filter. A tunable long-period fiber grating filter based short interval cascaded gratings was proposed and experimentally studied.The results show that the cascade of gratings have two different types of transmission spectrum characteristics, when the cascade interval is very close to centimeter, there will be a double wavelength loss of transmission spectrum, by segmented refractive index modulation depth control, can suppression the side lobe effectively. The simulation result shows that the peak loss of double wave is related to the fiber length, the resonant wavelength and acousto-optical grating have a linear correlation within a certain range.This paper provides a simple way to dynamically manipulate the grating period, while the side lobes of the transmission spectrum are suppressed. The simulation results provide a novel method to adjust the dual wavelength filter, which has great potential for laser and optical fiber communicat ion.