Broadband ultra-flattened dispersion micro-structured fiber

A micro-structured fiber comprising a core region and a cladding region, wherein the materials of the core region and the cladding region are silica, and the cladding region has a plurality of air holes regularly arranged on a plurality of rings, wherein an innermost ring of the fiber defines the core region, wherein the cladding region comprises an inner circumference portion and an outer circumference portion, the inner circumference portion and the outer circumference portion are adjacent one another, the inner circumference portion comprising at least two rings, wherein the air holes on each ring of the inner circumference portion have equal first diameters and first pitches therebetween respectively, the outer circumference portion comprising at least one ring, wherein the air holes on each ring of the outer circumference portion have equal second diameters and second pitches therebetween respectively, wherein the second diameter of the air hole on the outer circumference portion is larger than the first diameter of the air hole on the inner circumference portion, wherein a ratio of the first diameter to the first pitch of the air holes on the inner circumference portion is in the range of 0.2 to 0.4, and a ratio of the second diameter to the second pitch of the air holes on the outer circumference portion is in the range of 0.5 to 0.99, wherein the fiber has a flattened dispersion of ±0.5 ps/km/nm with a bandwidth in the range of 40 to 600 nm.