Studies On Design And Properties Of Several Special Photonic Crystal Fibers

Photonic crystal fiber(PCF), also called microstructured fiber(MOF) or holey fiber(HF), is formed from a central defect region surrounded by air holes running parallel to the fiber length. Because of their unique properties that cannot realize in conventional optical fibers such as a wide range of single-mode operations, easily controllable dispersion, nonlinearity, etc. PCF are attracting much attention in recent years.In this study, the dispersion, nonlinearity of total internal reflection photonic crystal fiber and bandgap of photonic bandgap photonic crystal fiber are discussed in detail, the main contents are following:1. Tailor of chromatic dispersion is a very important for communication systems, especially with the aim to achieve ultra-flattened, near zero dispersion. In this study, the numerical model of an index-guiding photonic crystal fibers filled by liquid with refractive index which is sensitive to temperature was demonstrated and the influence of the geometrical and optical parameters of this kind of fibers on the dispersion was numerically described by using the vectorial beam propagation method, the photonic crystal fibers with ultra-flattened, near zero dispersion, the absolute value of dispersion is less than 0.5 ps /( nm? km) between 1.46μm and 1.65μm were presented by adjusting the diameters of air holes and the pitch. Ethanol filled is a refractive index sensitive to temperature, so the influence of temperature on the dispersion, effective area and nonlinear properties was researched. The results show that the temperature obviously influence the transmission properties of this kind of photonic crystal fiber. When temperature increases, the dispersion increases and decreases in short wavelength region and in long wavelength region respectively. the effective area decreases and nonlinear coefficient increases with increasing the temperature in the whole wavelength region. The effects of the hole filling on dispersion, mode effective area and nonlinearity of this kind of fibers were presented. The results indicate that the dispersion will become more flattened and the nonlinearity will decrease after filling liquid into the holes in the cladding. This results provide theoretical basis for designing novel components for optical telecommunication system and optical sensors.2. The nonlinear property of photonic crystal fiber is simulated with the vectorial beam propagation method. The effective area of fundamental mode and the nonlinear coefficient are evaluated. The relationship between the effective area and nonlinear coefficient with the pitch and hole diameter, is analyzed. The nonlinear property of photonic crystal fiber can be controlled by the structural parameters.3. The bandgap distribution characteristic of photonic bandgap photonic crystal fiber(PBG-PCF) with triangular and square structure is analyzed by using plane waves method. The condition of air-guiding of light in PBG-PCF is deduced. By theory analysis and numerical simulation, the relation between the PBG property and the structure parameters of PCF has been found. The result indicate that the bandgaps increase with increase the diameters of air holes, decrease with decrease the pitch. When increasing the refractive index of the medium in rods of cladding ,the width of bandgap is increase.