Patent ID: 7920768

Claim:
A single mode optical fiber, comprising: a first central region defining a radius r1, said first central region having a maximum refractive index value n1 max and a minimum refractive index value n1 min ; and a second ring surrounding said first central region, wherein said second ring has a substantially constant refractive index value n2 that is less than the minimum refractive index value n1 min of said first central region; wherein the refractive index value of said first central region decreases from the central axis of symmetry in said first central region in a radial direction over a distance equal to the radius r1, the refractive index value decreasing from n1 max to n1 min in a substantially linear fashion, whereby said first central region is substantially free of a portion having a constant refractive index value, and wherein the decrease takes place in accordance with the following equation: slope = ( D ⁢ ⁢ 1 max - D ⁢ ⁢ 1 min ) / ( r ⁢ ⁢ 1 ) , wherein 0.11 < slope < 0.22 , ⁢ D i = n i 2 - n Cl 2 2 · n i 2 · 100 ⁢ % ⁢ ⁢ and ⁢ ⁢ n i > n Cl , and wherein D i =refractive index contrast for position i, n i =refractive index value of position i, and n cl =refractive index value of an outer fiber cladding.