Optimization of nearly zero ultra-flattened dispersion photonic crystal fibre with fluorine doped threefold symmetry core

A novel of PCF with nearly-zero ultra-flattened dispersion is proposed. It is composed of a threefold symmetry core and a cladding with seven rings hexagonal symmetry structure. The diameter of innermost air-holes is reduced to induce the optimum ultra-flattened dispersion upon wavelength over the range of 1.25~1.7 μm.