An optical fiber with ultra-low attenuation and bend insensitivity 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 3.0-3.9 m, and a relative refractive index difference of 0.04% to 0.12%. The inner cladding layer has a radius of 8-14 m, and a relative refractive index difference of about 0.35% to 0.10%. The trench cladding layer has a radius of about 14-20 m, and a relative refractive index difference of about 0.6% to 0.2%. The auxiliary outer cladding layer has a radius of about 35-50 m, and a relative refractive index difference of about 0.4% to 0.15%. The outer cladding layer is a pure silicon-dioxide glass layer.

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 doping optimized single-mode optical fiber with ultra low attenuation includes a core layer and cladding layers. The cladding layers has 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 content of fluorine in the core layer is 0.5 wt %, Ge0.12%, n.sub.10.12%. The content of fluorine in the inner cladding layer is 0.5-1.5 wt %, n.sub.20.14%. The content of fluorine in the trench cladding layer is 1-3 wt %, n.sub.30.25%. The content of fluorine in the auxiliary outer cladding layer is 0.5-2 wt %, n.sub.40.14%. The outer cladding layer is a pure silicon dioxide glass layer and/or a metal-doped silicon dioxide glass layer.

A bending-insensitive 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 3.0 to 3.9 m and a relative refractive index of 0.04% to 0.12%. The inner cladding layer has a radius of 8 to 14 m and a relative refractive index 0.35% to 0.10%. The trench cladding layer has a radius of 14 to 20 m and a relative refractive index of 0.6% to 0.2%. The auxiliary outer cladding layer has a radius of 35 to 50 m and a relative refractive index of 0.4% to 0.15%. The outer cladding layer is a pure silica glass layer.

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.

An optical fiber comprising: (i) a core comprising silica and having a maximum relative refractive index delta .sub.1MAX; and LP01 effective area >100 m.sup.2 at 1550 nm; (ii) an inner cladding surrounding the core and having a minimum relative refractive index delta .sub.2MIN and .sub.coreMAX>.sub.2MIN; (iii) an outer cladding surrounding the inner cladding and comprising a first outer cladding portion with a maximum refractive index .sub.3A such that .sub.3A>.sub.2MIN; and another outer cladding portion surrounding the first outer cladding portion with a maximum refractive index delta .sub.3B wherein with a maximum refractive index delta .sub.3B wherein .sub.3B>.sub.3A, said another portion being the outermost portion of the outer cladding; and (iv) a coating layer surrounding the outer cladding, and in contact with said another outer cladding portion, the coating layer having a relative refractive index delta .sub.C wherein .sub.C>.sub.3B.

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 core region of an optical fiber is doped with chlorine in a concentration that allows for the viscosity of the core region to be lowered, approaching the viscosity of the surrounding cladding. An annular interface region is disposed between the core and cladding and contains a concentration of fluorine dopant sufficient to match the viscosity of the core. By including this annular stress accommodation region, the cladding layer can be formed to include the relatively high concentration of fluorine required to provide the desired degree of optical signal confinement (i.e., forming a low loss optical fiber).