Design and characteristics of negative dispersion of two layered five ring photonic crystal fiber

A numerical finite element method (FEM) based analysis of mode profile, dispersion characteristics and birefringence of two layered five rings photonic crystal fiber for different air fill fraction d/Λ (0.6-0.9) is proposed. The proposed structure consists of two inner hexagonal layers and outer three circular layers. The inner hexagonal layers consist of air holes each of diameter d₁. Two circular layers surrounding the hexagonal layers have air holes of diameter d₂ while the outer most circular layer has air holes of diameter d₃. The proposed structure is shown to possess an optimum mode profile. The effective refractive index of the cladding depends on the air-fill fraction of the fiber. Refractive index decreases with increasing air-fill fraction for the same wavelength. It is shown that the negative dispersion coefficient can be controlled by the pitch Λ and the diameter of air holes. Also shown is the linear relation of Birefringence with bit rate. The corresponding graphs of all the parameters are evaluated and plotted. The proposed structure is simulated using the commercial Rsoft software.