Ultra-flattened chromatic dispersion control for circular photonic crystal fibers

A simple design procedure is utilized for achieving circular photonic crystal fibers with ultra-flattened chromatic dispersion. This procedure only requires four parameters (three air-hole diameters and one concentric spacing). The influence of the diameter of each air-hole ring on the circular PCF is investigated by simulations. The results show that the influence of air-hole size of each ring on the dispersion weakens from the inside ring to the outside. Based on the simulation results, an optimization procedure is utilized to control dispersion of the circular PCF. Through the reasonable set of concentric spacing and air-hole diameters of the inner three rings, a five-ring circular PCF with a flattened dispersion of 0 ± 0.5 ps km − 1 nm − 1 within the wavelength range of 1.215–2.02 µm is achieved. A low confinement loss of 3.2 × 10 − 3 dB km − 1 at 1.55 µm wavelength is simultaneously obtained. The influence of manufacturing imperfections of parameters on dispersion is also discussed to verify the robustness of our design.