Patent ID: 7289710

Claim:
A single-mode optical fiber suitable for a WDM (Wavelength Division Multiplexing) system, comprising: (a) a first core region positioned in the center of cross section and having a radius r 1 from the center and a relative refractive index difference Δ 1 ; (b) a second core region surrounding the first core region and having a radius r 2 from the center and a relative refractive index difference Δ 2 ; (c) a third core region surrounding the second core region and having a radius r 3 from the center and a relative refractive index difference Δ 3 ; and (d) a clad region surrounding the third core region and having a radius r 4 from the center and a relative refractive index difference Δ 4 , (e) wherein the radii of the regions have a relation of r 1 <r 2 <r 3 <r 4 , and the relative refractive index difference of the regions have relations of Δ 1 >Δ 2 , and Δ 2 <Δ 3 ; (here, Δ 1 (%)=[(n 1 −n c )/n c ]×100, Δ 2 (%)=[(n 2 −n c )/n c ]×100, Δ 3 (%)=[(n 3 −n c )/n c ]×100, n 1 : a refractive index of the first core region, n 2 : a refractive index of the second core region, n 3 : a refractive index of the third core region, n c : a refractive index of the clad region) (f) wherein the optical fiber uses a wavelength region from 1460 to 1625 nm, and has a dispersion value of 0.1 to 3.0 ps/nm-km at 1460 nm, 3.0 to 5.5 ps/nm-km at 1550 nm, and 4.5 to 8.0 ps/nm-km at 1625 nm, and (g) wherein a bending loss is 0.5 dB or less at 1625 nm under the condition of a bending radius of 30 mm, 100 turns.