Design of a novel octagonal photonic crystal fiber with fiat dispersion and high nonlinearity

In order to obtain a new flattened dispersion photonic crystal fiber with high nonlinearity,a novel octagonal photonic crystal fiber(O-PCF) with three-cladding structure was designed.The effect of the hole size and hole space on the nonlinearity and dispersion of the PCF was analyzed by means of the multi-pole method.The result shows that the dispersion and the nonlinearity coefficient of O-PCF decrease with the increasing of the diameter of inner air hole.With the increasing of the diameter of the third air hole,the dispersion increases.Meanwhile,the nonlinearity coefficient almost remains constant.The dispersion and nonlinearity coefficient is affected little by the diameter of the second layer and peripheral air hole.By optimizing the diameters of the O-PCF holes and the hole pitch,an O-PCF with high flattened dispersion and nonlinearity was achieved.At the wavelength range of 1.46μm~1.73μm,the dispersion coefficient is merely changed within ±0.5ps/(km·nm),and the nonlinearity coefficient is merely changed from 42.5W-1·km-1 to 50W-1·km-1 at 1.5μm to 1.65μm.These results offer theoretical references for designing the photonic crystal fiber with some specific function.