Multimode hexagonal photonic crystal fiber for extremely negative chromatic dispersion and low confinement loss

In this paper, a multi-mode hexagonal photonic crystal fiber is proposed. The cladding of the proposed PCF has circular air-holes arranged in five hexagonal rings whereas core has tiny circular air-holes arranged in two different rings. This structure is designed and simulated using COMSOL Multiphysics which is based on finite element method. The performance parameters viz chromatic dispersion, confinement loss, V-number, effective area, and nonlinearity coefficient are determined by wavelength interrogation method and optimized with respect to size and number of tiny circular air-holes in the inner ring of the core. The results show that V-number is greater than 3.1416 over wide range of spectrum which confirms the multimode operation of the fiber. The obtained value of performance parameters at 1.55 µm wavelength are; negative dispersion (− 2159 ps nm⁻¹ km⁻¹), confinement loss of (3.61 × 10⁻³ dB km⁻¹), V-number (3.66), effective area (3.44 µm²), and nonlinearity coefficient (27.5 w⁻¹ km⁻¹). The extremely negative dispersion alongwith very low confinement loss at the center wavelength of main communication window, i.e., 1.55 µm suggests that the proposed PCF is best suited for the dispersion compensation.