Study On The Characteristics Of PBG-PCF With Defects

Photonic crystal fiber was first proposed in 1992. It has unique structures and specialproperties compared to the traditional fiber. The photonic band gap of photonic crystal fiber(PBG-PCF) is a new generation of fiber. However, many defects are introduced in manufacturingprocess, by which the performance of the PBG-PCF is attenuated severely. For example, the loss ofvalue has not reached the level of conventional fiber.By keeping the strict periodicity of the cladding, three types of core are discussed. ThePBG-PCF with core cut by R = 1*Λis selected as the research object. In this paper, three forms ofdefect are studied: air hole missing defect, air hole deformation defect and air hole dislocationdefect. There are three new defect modes beside core mode introduced by an air hole missing defect.When the air hole missing defect appears within four levels of the cladding, there will be an"Avoided-Crossing Effect" at the cross point. The dispersion curve of core mode is cut off at theavoided crossing point. When air hole missing defect appears outside of the fourth level of thecladding, the dispersion curve of core mode is continuous. But at the cross point, there will be apeak on the curves of loss and birefringence. The number of the defect modes introduced byair hole deformation defect is determined by the deformation degree of the defect. No defect modeswill be introduced by the air hole deformation defect if the deformation degree is small(e.g. an airhole narrowed byΔd / d = 0.1 ). No new defect modes are introduced by the air hole dislocationdefect. But high birefringence is caused by this type of defect. A birefringence of 10?4 can beachieved by the second row of air holes with 20% of the dislocation. Air hole dislocation defect isa useful defect for high birefringence PBG-PCF.Finally, combination of multiple materials are also discussed. All the modes in the bandgapare easily solved by Vector Finite Element Method (FEM) , and more conclusions are reached. Thewhole paper is hoped useful to improve the performance of the PBG-PCF.