Research On Transmission Characteristics Of Photonic Crystal Fiber Long Period Gratings

Currently, photonic crystal fiber in optoelectronics has been a focus of research.Compared with the traditional single-mode fiber grtings, long period fiber gratings inphotonic crystal fiber have many advantages and cause great interest of researchers. Inthis paper, the transmission spectrum of long period gratings is theoretically analyzed,and the relevent features are obtained. The main contents of the dissertation are asfollows.Firstly, the development history, structural characteristics, applications of photoniccrystal fiber and long period fiber gratings are discussed in detail. With the numericalmethod about the photonic crystal fiber and the fiber gratings, a general methods foranalyzing the photonic crystal fiber gratings are given in this paper.Secondly, the transmission spectrum characteristics of grape-fruit photonic crystalfiber long period gratings are studied by finite element method and coupled mode theory.The transmission spectrum of long period gratings has realized through nunericalsimulation method, furthermore, the rules between the transmission spectrumcharacterisics and the fiber gratings parameters are obtained. But the cladding structureof grape-fruit photonic crystal fiber is special, then the transmission spectrumcharacteristics of the hexagonal-type photonic crystal fiber long period gratings varyingwith the structure parameters are discussed in the same way.Thirdly, photonic crystal fiber long period gratings written through the structuralmodulation are discussed with a modified coupled-mode theory named coupledlocal-mode theory. The mechanism and the transmission characteristics are analyzed intheory. The mode coupling is studied in this kind of fiber gratings, and the transmissionspectrum is simulated. Then the laws of resonant peaks varying with structuralparameters are obtained.Finally, the structural parameters of hollow-core air-silica photonic bandgap fibersare theoretical calculated with the plane wave expansion method. The transmissionspectrum of hollow core photonic bandgap fiber graings is numerically simulated through finite element method and the coupled local-mode theory. Furthermore, we can find thatthe transmission spectra properties vary with the structural parameters and then get somerelated rules.