A multicore optical fiber comprising: a depressed index common-cladding region having a refractive index Δ.sub.cc; and a plurality of core portions disposed within the depressed index common-cladding region, wherein each core portion comprises: a central axis, a core region comprising a relative refractive index Δ.sub.1, an inner-cladding region encircling and directly contacting the core region comprising a relative refractive index Δ.sub.2, a trench region encircling and directly contacting the inner cladding region comprising a relative refractive index Δ.sub.3, and an outer-cladding region encircling and directly contacting the trench region comprising a relative refractive index Δ.sub.4, wherein the refractive index of the depressed index common-cladding region Δ.sub.cc is less than the refractive index of the outer-cladding region Δ.sub.4, and wherein a difference between the refractive index of the depressed index common-cladding region Δ.sub.cc and the refractive index of the first outer-cladding region Δ.sub.4 is greater than 0.05% Δ.

A multicore optical fiber includes two or more cores, a common interior cladding surrounding the two or more cores, and a common exterior cladding surrounding the common interior cladding. The common exterior cladding has a lower relative refractive index than the common interior cladding and reduces tunneling losses from the cores. The reduced tunneling loss allows placement of cores closer to the edge of the fiber, thus providing multicore optical fibers having higher core count for a given fiber diameter. Separation between cores is controlled to minimize crosstalk.

A multicore optical fiber includes two or more cores, a common interior cladding surrounding the two or more cores, and a common exterior cladding surrounding the common interior cladding. The common exterior cladding has a lower relative refractive index than the common interior cladding and reduces tunneling losses from the cores. The reduced tunneling loss allows placement of cores closer to the edge of the fiber, thus providing multicore optical fibers having higher core count for a given fiber diameter. Separation between cores is controlled to minimize crosstalk.

A multicore optical fiber comprising: a depressed index common-cladding region having a refractive index Δ.sub.cc; and a plurality of core portions disposed within the depressed index common-cladding region, wherein each core portion comprises: a central axis, a core region comprising a relative refractive index Δ.sub.1, an inner-cladding region encircling and directly contacting the core region comprising a relative refractive index Δ.sub.2, a trench region encircling and directly contacting the inner cladding region comprising a relative refractive index Δ.sub.3, and an outer-cladding region encircling and directly contacting the trench region comprising a relative refractive index Δ.sub.4, wherein the refractive index of the depressed index common-cladding region Δ.sub.cc is less than the refractive index of the outer-cladding region Δ.sub.4, and wherein a difference between the refractive index of the depressed index common-cladding region Δ.sub.cc and the refractive index of the first outer-cladding region Δ.sub.4 is greater than 0.05% Δ.

An optical fiber includes (i) a chlorine doped silica based core having a core alpha (Core.sub.α)≥4, a radius r.sub.1, and a maximum refractive index delta Δ.sub.1max % and (ii) a cladding surrounding the core. The cladding surrounding the core includes a) a first inner cladding region adjacent to and in contact with the core and having a refractive index delta Δ.sub.2, a radius r.sub.2, and a minimum refractive index delta Δ.sub.2min such that Δ.sub.2min<Δ.sub.1max, b) a second inner cladding adjacent to and in contact with the first inner cladding having a refractive index Δ.sub.3, a radius r.sub.3, and a minimum refractive index delta Δ.sub.3min such that Δ.sub.3min<Δ.sub.2, and c) an outer cladding region surrounding the second inner cladding region and having a refractive index Δ.sub.5, a radius r.sub.max, and a minimum refractive index delta Δ.sub.3min such that Δ.sub.3min<Δ.sub.2. The optical fiber has a mode field diameter MFD at 1310 of ≥9 microns, a cable cutoff of ≤1260 nm, a zero dispersion wavelength of 1300 nm≤zero dispersion wavelength≤1324 nm, and a macrobending loss at 1550 nm for a 20 mm mandrel of less than 0.75 dB/turn.

A multicore optical fiber includes two or more cores, a common interior cladding surrounding the two or more cores, and a common exterior cladding surrounding the common interior cladding. The common exterior cladding has a lower relative refractive index than the common interior cladding and reduces tunneling losses from the cores. The reduced tunneling loss allows placement of cores closer to the edge of the fiber, thus providing multicore optical fibers having higher core count for a given fiber diameter. Separation between cores is controlled to minimize crosstalk.

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.

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.

A high bandwidth radiation-resistant multimode optical fiber includes a core and a cladding layer surrounding the core. The core is a fluorine-doped quartz glass layer with a graded refractive index distribution and a distribution power exponent of 1.7-2.2. The core has R1 of 15-35 m and 1%min of 0.8% to 1.2%. The cladding layer has an inner cladding layer having R2 of 15-38 m and 2% of 0.8% to 1.2% and/or a depressed inner cladding layer having R3 of 15-55 m and 3 of 1.0% to 1.4%, an intermediate cladding layer having R4 of 15.5-58 m and 4 of 0.7% to 0.2% a depressed cladding layer hasving R5 of 16-60 m and 5 of 0.8% to 1.2%, and an outer cladding layer sequentially formed from inside to outside. The outer cladding layer is a pure silica glass layer.

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.