Design of dispersion flattened photonic crystal fiber with a large core and a concentric missing ring

Novel structure of an index-guiding photonic crystal fiber (PCF) is proposed for flattened dispersion characteristics. As compared with the conventional PCFs, the proposed PCF has a following feature in its structure; the first ring area contains no air holes, and the third ring area also contains no air holes. Then the proposed PCF has a large core and a concentric missing ring. The chromatic dispersion was numerically simulated by the semi-vector finite difference method. The chromatic dispersion becomes almost flat in 1300 ∼ 1650 nm wavelength range when the air hole diameter is about 0.35 times the air hole spacing. Especially the chromatic dispersion is -1 ∼ 0 (ps/nm/km) in the above wavelength range when the air hole spacing is 1.25 μm and the air hole diameter is 0.43 μm.