Patent ID: 7228040

Claim:
A hole-assisted single mode optical fiber comprising: a first cladding region having a uniform refractive index; a core region with a radius r 1 having a refractive index higher than that of said first cladding region, and placed at a center of said first cladding region; and a second cladding region including at least four air hole regions, each of which has a radius r 2 , is separated by a distance d from a center of said core region, and is placed in said first cladding region, wherein the distance d is 2.0 to 4.5 times the radius r 1 of said core region, and the radius r 2 of said air hole regions is equal to or greater than 0.2 times the radius r 1 of said core region, and wherein said hole-assisted single mode optical fiber has zero-dispersion wavelength characteristics in a range from 1300 nm to 1324 nm, and has a bending loss characteristics equal to or less than 1 dB/m at a bending radius 10 mm, and variations in a mode field diameter by providing said air hole regions is equal to or less than ±10%.