An optical waveguide fiber comprising: (i) a Ge free core having an effective area of 100 μm 2 to 150 μm 2, at 1550 nm wavelength, said core comprising: (a) a central core region extending radially outwardly from a centerline to a radius r 1, and having a relative refractive index percent profile Δ 1 (r) in % measured relative to pure silica, wherein -0.1 % ≤ Δ 1 (r) ≤0.12 %, wherein the central core region has a maximum relative refractive index percent, Δ 1MAX; (b) a first annular core region surrounding and directly adjacent to the central core region, and extending to an outer radius r 2, wherein 6 μm ≤r 2 ≤ 10 μm, and having a relative refractive index percent profile, Δ 2 (r) in % measured relative to pure silica, a minimum relative refractive index Δ 2MIN, a maximum relative refractive index Δ 2MAX and the relative refractive index measured at a radius r = 2 μm, wherein - 0.45 ≤ Δ 2 ≤ 0; - 0.25 ≥ Δ 2 ⁢ MIN ≥ - 0.45 und Δ 1 ⁢ MAX ≥ Δ 2 r = 2 ⁢ μm; (c) a fluorine doped second annular region surrounding and directly adjacent to the first annular core region and extending to a radius 20 μm ≤r 3 ≤ 30 μm and having a negative relative refractive index percent profile, Δ 3 (r) in %, measured relative to pure silica, with a minimum relative refractive index percent Δ 3MIN and - 0.5 % < Δ 3 ⁢ MIN < - 0.25 %; and Δ 3 ⁢ MIN ≤ Δ 2 ⁢ MIN (ii) a cladding surrounding the core and having a relative refractive index percent Δ 4 (r) in % measured relative to pure silica and a minimum refractive index delta Δ 4MIN, and - 0.4 % < Δ 4 < - 0.2 %; wherein the relative refractive index profile of the optical fiber is selected to provide attenuation of no more than 0.17 dB/km at the 1550 nm wavelength; characterised in that the first annular core region has an α value 1.5 ≤ α ≤ 10. (i) a Ge free core having an effective area of 100 μm 2 to 150 μm 2, at 1550 nm wavelength, said core comprising: (a) a central core region extending radially outwardly from a centerline to a radius r 1, and having a relative refractive index percent profile Δ 1 (r) in % measured relative to pure silica, wherein -0.1 % ≤ Δ 1 (r) ≤0.12 %, wherein the central core region has a maximum relative refractive index percent, Δ 1MAX; (b) a first annular core region surrounding and directly adjacent to the central core region, and extending to an outer radius r 2, wherein 6 μm ≤r 2 ≤ 10 μm, and having a relative refractive index percent profile, Δ 2 (r) in % measured relative to pure silica, a minimum relative refractive index Δ 2MIN, a maximum relative refractive index Δ 2MAX and the relative refractive index measured at a radius r = 2 μm, wherein - 0.45 ≤ Δ 2 ≤ 0; - 0.25 ≥ Δ 2 ⁢ MIN ≥ - 0.45 und Δ 1 ⁢ MAX ≥ Δ 2 r = 2 ⁢ μm; (c) a fluorine doped second annular region surrounding and directly adjacent to the first annular core region and extending to a radius 20 μm ≤r 3 ≤ 30 μm and having a negative relative refractive index percent profile, Δ 3 (r) in %, measured relative to pure silica, with a minimum relative refractive index percent Δ 3MIN and - 0.5 % < Δ 3 ⁢ MIN < - 0.25 %; and Δ 3 ⁢ MIN ≤ Δ 2 ⁢ MIN (a) a central core region extending radially outwardly from a centerline to a radius r 1, and having a relative refractive index percent profile Δ 1 (r) in % measured relative to pure silica, wherein -0.1 % ≤ Δ 1 (r) ≤0.12 %, wherein the central core region has a maximum relative refractive index percent, Δ 1MAX; (b) a first annular core region surrounding and directly adjacent to the central core region, and extending to an outer radius r 2, wherein 6 μm ≤r 2 ≤ 10 μm, and having a relative refractive index percent profile, Δ 2 (r) in % measured relative to pure silica, a minimum relative refractive index Δ 2MIN, a maximum relative refractive index Δ 2MAX and the relative refractive index measured at a radius r = 2 μm, wherein - 0.45 ≤ Δ 2 ≤ 0; - 0.25 ≥ Δ 2 ⁢ MIN ≥ - 0.45 und Δ 1 ⁢ MAX ≥ Δ 2 r = 2 ⁢ μm; (c) a fluorine doped second annular region surrounding and directly adjacent to the first annular core region and extending to a radius 20 μm ≤r 3 ≤ 30 μm and having a negative relative refractive index percent profile, Δ 3 (r) in %, measured relative to pure silica, with a minimum relative refractive index percent Δ 3MIN and - 0.5 % < Δ 3 ⁢ MIN < - 0.25 %; and Δ 3 ⁢ MIN ≤ Δ 2 ⁢ MIN (ii) a cladding surrounding the core and having a relative refractive index percent Δ 4 (r) in % measured relative to pure silica and a minimum refractive index delta Δ 4MIN, and - 0.4 % < Δ 4 < - 0.2 %; wherein the relative refractive index profile of the optical fiber is selected to provide attenuation of no more than 0.17 dB/km at the 1550 nm wavelength; characterised in that the first annular core region has an α value 1.5 ≤ α ≤ 10.