Abstract

In this paper, two new square-lattice photonic crystal fibers (PCFs) are designed and proposed. Both fibers have identical structures with five air-hole rings, yet the diameter of air-holes differ in their structures. Finite-difference time-domain (FDTD) method with the perfectly matched layers (PML) boundary conditions has been used to investigate these fibers. The proposed photonic crystal fibers exhibit properties of ultra-flattened nearly zero dispersion and low confinement loss in wavelength range of 1.2 to 1.7 µm. Dispersion slope in both fibers is about 7 × 10^-3 ps/(nm².km). Since dispersion and confinement loss of the first photonic crystal fiber (PCF₁) at the wavelength 1.55 µm are 0.00249 ps/(nm.km) and about 4 × 10^-6 dB/km, respectively, its application as transmission medium in optical communications will be highly favored. Although, the zero dispersion wavelength of the second PCF (PCF₂) is 1.45 µm, the confinement loss of this fiber is lower than PCF₁ and below 10^-7 dB/km in all of the studied wavelength range.

Key words: Square lattice, photonic crystal fiber, dispersion, confinement loss.