A dispersion shifted optical fiber where a radius r.sub.0 of a first center segment is 0.5 μm to 2.8 μm, and a relative refractive index difference Δ.sub.0 is 0.4% or more and 0.9% or less. A radius r.sub.1 of a first segment is 1.8 μm or more and 4.5 μm or less. A radius r.sub.2 of a second segment is 4.0 μm or more and 8.0 μm or less, and a relative refractive index difference Δ.sub.2 is 0.00% or more and 0.07% or less. A radius r.sub.3 of a third segment is 4.5 μm or more and 8.5 μm or less, and a relative refractive index difference Δ.sub.3 is 0.285% or more and 0.5% or less. A radius r.sub.4 of a fourth segment is 8.0 μm or more and 16.0 μm or less, and a relative refractive index difference Δ.sub.4 is 0.005% or more and 0.04% or less.

An object is to obtain an optical fiber having a small diameter and suppressing the increase of a microbending loss of the optical fiber. The optical fiber includes: a core portion made of silica glass; a cladding portion made of silica glass, the cladding portion covering the outer periphery of the core portion and having a refractive index smaller than a maximum refractive index of the core portion; and a coating portion covering the outer periphery of the cladding portion. The outer diameter of the cladding portion is 100 μm or smaller, the relative refractive-index difference Δ1 of the core portion is 0.5% or smaller, and the thickness of the coating portion is 10 μm or larger.

An optical fiber connection is provided that includes a first optical fiber defining a first exterior surface and a first effective area. The first fiber defines a first tapered region tapering from a first nominal fiber diameter to a first tapered diameter. A second optical fiber has a second exterior surface and a second effective area less than the first effective area. The second fiber defines a second tapered region tapering from a second nominal fiber diameter to a second tapered diameter and a fiber splice optically coupling the first tapered region of the first fiber to the second tapered region of the second fiber. The first and second tapered regions taper such that the first and second exterior surfaces have a variance from a Gaussian function of less than 25% of the Gaussian function at each point along the first and second exterior surfaces.

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.

No core is disposed at the lattice point of a triangular lattice of a first layer LY1. First cores 11a and 11b of the core elements 10a and 10b are disposed at the lattice points of a second layer LY2. A first core 11c of the core element 10c and the second core 21 are alternately disposed at the lattice points of a third layer LY3. In a fourth layer LY4, no core is disposed at six lattice points, and the first cores 11a and 11b of the core elements 10a and 10b are disposed at the other lattice points. The second cores 21 are adjacent to the lattice points of the fourth layer LY4, at which no core is disposed. The effective refractive indexes of the core elements adjacent to each other are different from each other.

An optical fiber having a core comprising silica and greater than 1.5 wt % chlorine and less than 0.5 wt % F, said core having a refractive index Δ.sub.1MAX, and an inner cladding region having refractive index Δ.sub.2MIN surrounding the core, where Δ.sub.1MAX>Δ.sub.2MIN.

The present embodiment relates to a CMCF including a structure to achieve more efficient reduction in transmission loss by suppressing decrease in concentration of alkali metal due to diffusion of alkali metal. In the CMCF including a plurality of cores, a power coupling coefficient h between adjacent cores is set to 1×10.sup.−3/m or more, to maintain an optical coupling state between the adjacent cores. In addition, alkali metal contributing to reduction in transmission loss is added to each of the cores such that a stress maximum value σ_.sub.max between adjacent cores has a negative value.

An optical fiber is provided that includes a core region, a cladding region having a radius less than about 62.5 microns; a polymer coating comprising a high-modulus layer and a low-modulus layer, wherein a thickness of the low-modulus inner coating layer is in a range of 4 microns to 20 microns, the modulus of the low-modulus inner coating layer is less than or equal to about 0.35 MPa, a thickness of the high-modulus coating layer is in a range of 4 microns to 20 microns, the modulus of the high-modulus inner coating layer is greater than or equal to about 1.6 GPa, and wherein a puncture resistance of the optical fiber is greater than 20 g, and wherein a microbend attenuation penalty of the optical fiber is less than 0.03 dB/km, and wherein an outer diameter of the coated optical fiber is less than or equal to 175 microns