Wide-band dispersion controlled optical fiber

A wide-band dispersion controlled optical fiber, characterized in that a cut-off wavelength is substantially 1285 nm or less, dispersion values are −12 to −4 ps/nm/km in a wavelength region of substantially 1285 nm to 1330 nm and 8 to 14 ps/nm/km at substantially 1625 nm wavelength, a zero dispersion wavelength is positioned in a wavelength region below substantially 1430 nm, wherein the effective cross-section area of the optical fiber at substantially 1550 nm wavelength is less than 75 μm2, and wherein the difference of losses between the 1550 nm wavelength and the 1625 nm wavelength is substantially 0.03 dB/km or less, wherein the wide-band dispersion controlled optical fiber includes an internal core which has a diameter d1 and a refractive index n1;

• an external core which encloses the internal core and has a diameter d2, the refractive index n2 of the external core gradually decreasing from n1 in the direction away from the center of the internal core;
• an internal clad which encloses the external core and has a diameter d3 and a refractive index n3;
• and an external clad which encloses the internal clad and has a refractive index n4, and wherein the diameters meet with the relationships of 0≦d1/d2≦0.8 and 0.1≦d2/d3≦0.5 and the refractive indexes meet with the relationships of n1>n2≧n3≧n4, 0.0034≦(n1–n4)/n1≦0.007, 0≦(n2–n4)/n2≦0.0048, and 0≦(n3–n4)/n3≦0.0014.