Patent ID: 8873917

Claim:
An optical fiber comprising: a central glass core region comprising maximum refractive index delta percent Δ 1 , a first inner annular region surrounding said core comprising refractive index delta percent Δ 2 , a depressed annular region surrounding said inner annular region and comprising Δ 3 and a third annular region surrounding the depressed annular region comprising refractive index delta percent Δ 4 ; wherein the third annular region comprises chlorine an amount greater than 0.2 weight percent in a region which is within 5 microns from the depressed annular region, wherein Δ 1MAX >Δ 4 >Δ 2 >Δ 3 , wherein the difference between Δ 4 and Δ 2 is greater than or equal to 0.01 and a profile volume, V 3 , equal to: V 3 = 2 ⁢ ∫ r ⁢ ⁢ 2 r ⁢ ⁢ 3 ⁢ Δ ⁡ ( r ) ⁢ r ⁢ ⅆ r wherein |V 3 | is at least 50% Δμm 2 , and said fiber exhibits a cable cutoff less than 1260 nm.