Disclosed is a multi-core optical fiber having a plurality of cores extending parallelly along a central axis of the multi-core optical fiber. Each core of the plurality of cores is up-doped with an up-dopant. The multi-core optical fiber further has a plurality of buffer layers such that each buffer layer of the plurality of buffer layers envelop a corresponding core of the plurality of cores. Each buffer layer of the plurality of buffer layers has a predefined buffer layer thickness. The multi-core optical fiber further has a plurality of trench layers such that each trench layer of the plurality of trench layers envelops a corresponding buffer layer of the plurality of buffer layers. Each trench layer of the plurality of trench layers is down-doped with a down-dopant. The multi-core optical fiber has an inter-core crosstalk of less than −30 decibel/kilometres (dB/km) at a wavelength of 1550 nanometres (nm).

Embodiments of the current disclosure include low moat volume single mode ultra-low loss optical fibers. In some embodiments, a single mode optical fiber includes a first core region; a second core region surrounding and directly adjacent to the first core region, wherein a volume V of the second core region is less than or equal to 14% Δμm.sup.2; a cladding region surrounding the core region; and wherein the optical fiber has a cable cutoff of less than 1260 nm, a mode field diameter at 1310 nm of 8.6 microns to 9.7 microns, a mode field diameter at 1550 nm of 9.9 microns to 11 microns, and an attenuation at 1550 nm of less than or equal to 0.17 dB/km.

The present disclosure provides optical fibers with an impact-resistant coating system. The fibers feature low attenuation. The coating system includes a primary coating and a secondary coating. The primary coating and secondary coating have reduced thickness to provide low-diameter fibers without sacrificing protection. The primary coating has high tear strength and is resistant to damage caused by mechanical force. The secondary coating has high puncture resistance. The outer diameter of the optical fiber is less than or equal to 190 μm.

A single mode optical fiber is provided that includes a core region having an outer radius r.sub.1 and a maximum relative refractive index Δ.sub.1max. The single mode optical fiber further includes a cladding region surrounding the core region, the cladding region includes a depressed-index cladding region, a relative refractive index Δ.sub.3 of the depressed-index cladding region increasing with increased radial position. The single mode optical fiber has a bend loss at 1550 nm for a 15 mm diameter mandrel of less than about 0.75 dB/turn, a bend loss at 1550 nm for a 20 mm diameter mandrel of less than about 0.2 dB/turn, and a bend loss at 1550 nm for a 30 mm diameter mandrel of less than 0.005 dB/turn. Additionally, the single mode optical fiber has a mode field diameter of 9.0 microns or greater at 1310 nm wavelength.

This MCF ensures sufficient manufacturing tolerance, is excellent in mass productivity, and is also capable of suppressing degradation of splice loss. The MCF includes four cores and a common cladding. Each core has adjacent relationships with two cores of remaining cores, an adjacent core interval Λ is from Λ.sub.nominal−0.9 μm to Λ.sub.nominal+0.9 μm, a common cladding diameter is from 124 μm to 126 μm, an MFD, λ.sub.cc and d.sub.coat at a wavelength of 1310 nm satisfy a predetermined relationship, the MFD is from a MFD-reference-value−0.4 μm to the MFD-reference-value+0.4 μm with the MFD-reference-value of from 8.6 μm to 9.2 μm, a zero-dispersion wavelength is from a wavelength-reference-value−12 nm to the wavelength-reference-value+12 nm with the wavelength-reference-value of from 1312 nm to 1340 nm, a dispersion slope at a zero-dispersion wavelength is 0.092 ps/(nm.sup.2.Math.km) or less, λ.sub.cc is 1260 nm or less, and a predetermined structural condition and an optical condition are satisfied.

The present invention provides a large-effective-mode-area low-loss optical fiber with optimized cladding components, which comprises a core layer and a cladding comprising, from the inside to the outside, a first sinking layer, a second sinking layer, an optional third sinking layer, and an outer cladding. In the present invention, phosphorus and aluminum are co-doped in the optical fiber cladding, to form a tetrahedron [AlPO.sub.4] in glass, thus optimizing the viscosity of the cladding while effectively reducing the refractive index of the cladding, without causing increased hydrogen loss. The process is simple, and highly repeatable.

An optical fiber includes a core and a cladding surrounding an outer periphery of the core and has a refractive index profile in which a relative refractive index difference with respect to a distance r from a center of the core is represented by Δ(r), where a value of A represented by

A=−∫.sub.0.sup.0.22MFD.sup.1.31(Δ(r)−Δ.sub.ref(r))dr+∫.sub.0.22MFD.sub.1.31.sup.0.44MFD.sup.1.31(Δ(r)−Δ.sub.ref(r))dr  (Formula 1)

is 0.3%.Math.μm or less, where a unit of r is μm, a unit of a relative refractive index difference Δ(r) is %, Δ.sub.ref(r)=−0.064r+0.494, and MFD.sub.1.31 is a mode field diameter at a wavelength of 1.31 μm.

According to some embodiments a method of processing an optical fiber comprises the steps of: (i) drawing the fiber at a drawing rate of at least 30 m/sec; and (ii) cooling the drawn fiber in a gas at an average cooling rate less than 5000° C./s, such that said cooling reduces the temperature of the fiber from an entering temperature in the range between 1500° C. and 1700° C. to another temperature in the range between 1200° C. and 1400° C., the gas being at a temperature between 800° C. and 1500° C.; and the thermal conductivity κ of the gas being not greater than 1.5×10.sup.−4 cal/cm-s-K for at least one temperature within a range of 800° C. to 1500° C. at one atm (atmosphere) pressure absolute.

Described herein are coated optical fibers including an optical fiber portion, wherein the optical fiber portion includes a glass core and cladding section that is configured to possesses certain mode-field diameters and effective areas, and a coating portion including a primary and secondary coating, wherein the primary coating is the cured product of a composition that possesses specified liquid glass transition temperatures, such as below −82° C., and/or a viscosity ratios, such as between 25° C. and 85° C., of less than 13.9. Also described are radiation curable coating compositions possessing reduced thermal sensitivity, methods of coating such radiation curable coating compositions to form coated optical fibers, and optical fiber cables comprising the coated optical fibers and/or radiation curable coating compositions elsewhere described.

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.