Patent ID: 8520995

Claim:
An optical fiber, comprising a central core and an optical cladding, wherein: said central core has a refractive index n 1 and a radius r 1 such that 3.2 μm<r 1 <4.5 μm; said optical cladding has a refractive index n 2 such that n 2 <n 1 and 0.31%<((n 1 −n 2 )÷n 2 )<0.55%; and said optical cladding comprises at least five holes of radius r h , each said hole positioned at a distance Λ from said central core, the distance Λ being measured from the center of said central core to the center of each said hole, wherein (i) 0.5r 1 ≦r h ≦r 1 , and (ii) 9 μm<Λ≦17 μm; wherein the optical fiber has an effective cut-off wavelength (Λ Ceff ) of 1280 nanometers or less; wherein the optical fiber has a MAC value at least 6.5, the MAC value defined as the ratio of the optical fiber's mode field diameter (2W 02 ) at a wavelength of 1550 nanometers to the optical fiber's effective cut-off wavelength (Λ Ceff ); and wherein all holes in said optical cladding are substantially positioned in a single ring (i) equidistantly from said central core and (ii) circumferentially equidistantly around said central core.