Patent ID: RE39028

Claim:
A single mode optical waveguide fiber comprising: a core glass region comprising a first circular central segment, having a relative index Δ 0 % and a radius r 0 , a first annular segment surrounding and in contact with the central segment, having a relative index Δ 1 % and a radius r 3 and a second annular segment surrounding and in contact with the first annular segment, having a relative index Δ 2 %, a radius r 2 , and a width w 2 , the respective segments each having a refractive index profile; a clad glass layer having a refractive index profile and a minimum refractive index n c , wherein n c is the reference index for the relative index of each core segment; in which the index profile of the central segment is an a profile having α in the range of about 0.7 to 2, the index profile of the first annular segment is substantially flat, the index profile of the second annular segment is a rounded step, and Δ 0 %>Δ 2 %>Δ 1 %, the values of the respective Δ's and radii being chosen so that the inner profile volume is in the range 2.28 to 3.26% μm 2 , the outer profile volume is in the range 3.70 to 13.75% μm 2 and the ratio of outer to inner volume is in the range 1.5 to 4.3.