An optical fiber with ultra-low attenuation and large effective-area includes a core layer and cladding layers. The cladding layers have an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary outer cladding layer. The core layer has a radius of 4.8-6.5 m, and a relative refractive index difference of 0.06% to 0.10%. The inner cladding layer has a radius of 9-15 m, and a relative refractive index difference of about 0.40% to 0.15%. The trench cladding layer has a radius of about 12-17 m, and a relative refractive index difference of about 0.8% to 0.3%. The auxiliary outer cladding layer has a radius of about 37-50 m, and a relative refractive index difference of about 0.6% to 0.25%. The outer cladding layer is a pure silicon-dioxide glass layer.

An optical fiber comprising: (i) a core region comprising an outer radius r.sub.1, and 3.0r.sub.17.0 microns and a relative refractive index .sub.1max and 0.32%.sub.1max0.5%; (b) a depressed index cladding region surrounding the core region comprising an outer radius r.sub.3 and a relative refractive index .sub.3 less than 0.2%, and trench volume V.sub.3 wherein 45% -micron.sup.2|V.sub.3|200% -micron.sup.2; (c) a first outer cladding region surrounding the depressed index cladding region and comprising a relative refractive index .sub.4 and an outer radius r.sub.4; and (d) a second outer cladding layer comprising 5 wt %-20 wt % titania, a relative refractive index .sub.5, and a thickness T.sub.M, wherein 3 micronT.sub.M30 microns, and outer radius r.sub.565 microns; the optical fiber has a mode field diameter MFD.sub.1550 and 8 micronsMFD.sub.155010.5 microns, a cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, and a bending loss at 1550 nm when using a mandrel comprising a radius of 2.5 mm of 10 dB/turn.

A single-mode fiber with ultralow attenuation includes a core layer and cladding layers. The cladding layers includes an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary cladding layer. The core layer has a radius of 3.9-4.8 m and a relative refractive index difference of 0.08% to 0.10%. The inner cladding layer has a radius of 9-14 m and a relative refractive index difference of 0.40% to 0.15%. The trench cladding layer has a radius of 13-25 m and a refractive index difference of 0.7% to 0.3%. The auxiliary outer cladding layer has a radius of 30-50 m and a relative refractive index difference of 0.4% to 0.15%. The outer cladding layer is a pure silicon dioxide glass layer.

A single-mode fiber with an ultra-low attenuation and a large effective area includes a core layer having a radius of 4.8 to 6.5 and a relative refractive index difference n.sub.1 of 0.06% to 0.10%, and cladding layers. The cladding layers includes an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary cladding layer. The inner cladding layer has a radius of 9 to 15 m and a relative refractive index difference of 0.40% to 0.15%. The trench cladding layer has a radius of 12 to 17 m and a relative refractive index difference of 0.8% to 0.3%. The auxiliary outer cladding layer has a radius of 37 to 50 m and a relative refractive index difference of 0.6% to 0.25%. The outer cladding layer is a pure-silicon-dioxide glass layer.

The optical fiber according to the present invention includes, in a cross section of the optical fiber, one core region (11) and a cladding region (12) that is arranged on an outer periphery of the core region. The cladding region is a medium that has a lower refractive index than that of the core region and also has a smaller refractive index wavelength dispersion than that of the core region. The optical fiber has a solid core and therefore, allows more reduction in the Rayleigh scattering loss compared to an optical fiber having a hollow core. In addition, since the optical fiber adopts, for the cladding region, a medium that has a smaller refractive index wavelength dispersion than that of the core region, it allows a reduction in the wavelength dispersion of n.sub.eff.

An optical fiber cable has a sectional area of Ac [m.sup.2] and housing a number N of optical fibers. A transmission loss .sub.dB [dB/km], a mode field diameter W [m], an effective area Aeff [m.sup.2], an effective length L.sub.eff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined equation.

A single-mode fiber with an ultra-low attenuation and a large effective area includes a core layer having a radius of 4.8 to 6.5 and a relative refractive index difference n.sub.1 of 0.06% to 0.10%, and cladding layers. The cladding layers includes an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary cladding layer. The inner cladding layer has a radius of 9 to 15 m and a relative refractive index difference of 0.40% to 0.15%. The trench cladding layer has a radius of 12 to 17 m and a relative refractive index difference of 0.8% to 0.3%. The auxiliary outer cladding layer has a radius of 37 to 50 m and a relative refractive index difference of 0.6% to 0.25%. The outer cladding layer is a pure-silicon-dioxide glass layer.

An optical fiber cable has a sectional area of Ac [mm.sup.2] and housing a number N of optical fibers. A transmission loss .sub.dB [dB/km], a mode field diameter W [m], an effective area Aeff [m.sup.2], an effective length L.sub.eff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 m.sup.2.

An optical fiber cable has a sectional area of Ac [mm.sup.2] and housing a number N of optical fibers. A transmission loss .sub.dB [dB/km], a mode field diameter W [m], an effective area Aeff [m.sup.2], an effective length L.sub.eff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined, equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 m.sup.2.

An optical fiber cable has a sectional area of Ac [mm.sup.2] and housing a number N of optical fibers. A transmission loss .sub.dB [dB/km], a mode field diameter W [m], an effective area Aeff [m.sup.2], an effective length L.sub.eff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined, equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 m.sup.2.