US Patent 7555187 Large effective area fiber

An optical fiber according to an embodiment of the present invention comprises: a glass core extending from a centerline to a radius R1 wherein R1 is greater than about 5 μm; a glass cladding surrounding and in contact with the core, the cladding comprising: (i) a first annular region extending from the radius R1 to a radius R2, the first annular region comprising a radial width, W2=R2−R1, (ii) a second annular region extending from the radius R2 to a radius R3, and comprising a radial width, W3=R3−R2, and (iii) a third annular region surrounding the second annular region and extending from the radius R3 to an outermost glass radius R4; wherein the core comprises a maximum relative refractive index, Δ1MAX, relative to the third annular region, and wherein Δ1MAX is greater than about 0.1% and less than about 0.3%; the first annular region has a refractive index delta Δ2(r) is less than about 0.025%; wherein the second annular region comprises a minimum relative refractive index, Δ3MIN, relative to the third annular region;