Disclosed is an optical fiber which includes a core including silica with a core diameter and having at least two dopants, a maximum relative refractive index delta of at least 0.7% and an alpha value in the range of 1.9-2.2. The core has a refractive index profile configured to transmit light in a multimode propagation at a first wavelength λ.sub.1 in the range of 800-1100 nm and to propagate light in a LP01 mode at a second wavelength λ.sub.2. The second wavelength λ.sub.2 is greater than 1200 nm. The optical fiber is structured to have a LP01 mode field diameter in the range of 8.5-12.5 μm at 1310 nm.

An MCF cable according to an embodiment contains a plurality of MCFs each including at least one coupled core group and a common cladding. Λ is set such that κ at a wavelength of 1550 nm is falls within a range of from 1×10.sup.−1 [m.sup.−1] to 1×10.sup.3 [m.sup.−1], and (βΛC.sub.avg)/(2κ) or (βΛC.sub.f)/(2κ) is set in a specific range in a wavelength band of from 1530 nm to 1625 nm, where C.sub.avg [m.sup.−1], C.sub.f [m.sup.−1], and f.sub.twist [turn/m] represent the average curvature, the pseudo-curvature, and the average torsion, respectively, for each MCF, and κ [m.sup.−1], β [m.sup.−1], and Λ [m] represent the coefficient of mode coupling between adjacent cores, the average of propagation constants, and the core center-to-center distance, respectively.

Disclosed herein are optical waveguide fibers comprising: (I) a core comprising an outer radius r.sub.1, a maximum refractive index delta percent Δ.sub.1 max and core alpha, α, of larger than 5; and (II) a cladding surrounding the core, the cladding comprising: (i) an inner cladding region having outer radius r.sub.2 and refractive index delta percent Δ.sub.2, wherein Δ.sub.1max>Δ.sub.2; (ii) a trench region surrounding the inner cladding region, the trench region having an outer radius, r.sub.3 where r.sub.3≧10 microns and refractive index delta percent Δ.sub.3; and (iii) an outer cladding region having chlorine concentration of ≧1.2 wt. % surrounding the trench region and comprising refractive index delta percent Δ.sub.4, wherein Δ.sub.1max>Δ.sub.4 and Δ.sub.2>Δ.sub.3, and Δ.sub.4>Δ.sub.3 and wherein the difference between Δ.sub.4 and Δ.sub.3 is ≧0.12 percent.

A method is provided that includes: forming a low-index trench region with a first density; forming an inner barrier layer comprising silica around the trench region at a second density greater than the first density; depositing silica-based soot around the first barrier layer to form an overclad region at a third density less than the second density; inserting a core cane into a trench-overclad structure; forming an outer barrier layer comprising silica in an outer portion of the overclad region at a fourth density greater than the third density; flowing a down dopant-containing gas through the trench-overclad structure to dope the trench region with the down dopant, and wherein the barrier layers mitigate diffusion of the down-dopant into the overclad region; and consolidating the trench-overclad and the core cane.

An optical fiber includes a core, and a clad surrounding an outer circumference of the core, in which a first relative refractive index difference Δ1a is greater than 0, a second relative refractive index difference Δ1b is greater than 0, the first relative refractive index difference Δ1a is greater than the second relative refractive index difference Δ1b, the first relative refractive index difference Δ1a and the second relative refractive index difference Δ1b satisfy a relationship denoted by the following expression: 0.20≦(Δ1a−Δ1b)/Δ1a≦0.88, and a refractive index profile Δ of the core in an entire region of a section of 0≦r≦r1 as a function Δ(r) of a distance r from a center of the core in the radial direction is denoted by the following expression: Δ(r)=Δ1a−(Δ1a−Δ1b)r/r1.

The invention concerns a multimode optical fiber, with a graded-index core co-doped with at least fluorine F and germanium GeO.sub.2 and a refractive index profile with at least two α-values. According to the invention, the concentration of fluorine F at the core center ([F].sub.r=0) is between 0 and 3 wt % and the concentration of fluorine F at the core outer radius ([F].sub.r=α) is between 0.5 wt % and 5.5 wt %, with [F].sub.r=α−[F].sub.r=0>0.4 wt %. For wavelengths comprised between 850 nm and 1100 nm, said multimode optical fiber has an overfilled launch bandwidth (OFL-BW) greater than 3500 MHz.Math.km and a calculated effective modal bandwidth (EMBc) greater than 4700 MHz.Math.km over a continuous operating wavelength range greater than 150 nm.

A rollable optical fiber ribbon utilizing low attenuation, bend insensitive fibers and cables incorporating such rollable ribbons are provided. The optical fibers are supported by a ribbon body, and the ribbon body is formed from a flexible material such that the optical fibers are reversibly movable from an unrolled position to a rolled position. The optical fibers have a large mode filed diameter, such as ≥9 microns at 1310 nm facilitating low attenuation splicing/connectorization. The optical fibers are also highly bend insensitive, such as having a macrobend loss of ≤0.5 dB/turn at 1550 nm for a mandrel diameter of 15 mm.

An MCF of the present embodiment has eight or more cores. A diameter of a common cladding is not more than 126 μm. Optical characteristics of each core are as follows: a TL at a predetermined wavelength of 1310 nm is not more than 0.4 dB/km; an MFD at the predetermined wavelength is from 8.0 μm to 10.1 μm; a BL in a BR of not less than 5 mm or in the BR of not less than 3 mm and, less than 5 mm is not more than 0.25 dB/turn at the predetermined wavelength; λ0 is from 1300 nm to 1324 nm; λcc is not more than 1260 nm; an XT or XTs at the predetermined wavelength is not more than 0.001/km.

A fiber span comprising: a first optical fiber and a second optical fiber coupled to the first optical fiber, both fibers comprising the an inner core region with maximum refractive index delta, Δ.sub.0≦0.1% and an outer radius R.sub.1>4.5 μm, an outer core region with an outer radius R.sub.2 and a minimum refractive index delta Δ.sub.1 and alpha value α≧5, wherein Δ.sub.1<Δ.sub.0, 5.5 μm≦R.sub.2−R.sub.1≦12 μm; a cladding including a low index ring surrounding the core and a minimum refractive index delta Δ.sub.R,MIN<Δ.sub.1; and an outer cladding having Δ.sub.Outer-Clad>Δ.sub.R,MIN; the first fiber introducing differential mode delay DMD.sub.1 for wavelengths between 1525 and 1570 nm such that |DMD.sub.1|≦100 ps/km, and a first differential mode delay slope DMDS.sub.1; the second fiber introducing differential mode delay DMD.sub.2 for wavelengths between 1525 and 1570 nm such that |DMD.sub.2|≦100 ps/km, and a second differential mode delay slope DMDS.sub.2 that has an opposite sign from the first dispersion slope DMDS.sub.1; wherein total differential mode delay provided by the first fiber in conjunction with the second fiber is DMD.sub.tot=DMD.sub.1+DMD.sub.2, and −1.0 ps/km<DMD.sub.tot<1.0 for all wavelengths between 1525 nm and 1570 nm.

An optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.