A multimode coupling fiber for optical data links features low coupling loss to silicon photonics lasers, VCSELs, single mode transmission fibers, multimode transmission fibers, and high speed receivers. The coupling fiber includes a core, an optional inner cladding region, a depressed index cladding region, and an outer cladding region. The relative refractive index profile of the coupling fiber includes a core region with α profile and a depressed index cladding region that facilitates low bending loss and high bandwidth. The mode field diameter of the coupling fiber is well-matched to standard single mode transmission fibers and the etendue of the coupling fiber is high enough to couple efficiently to multimode transmission fibers.

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.

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.

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.

An optical fiber includes: a core; and a clad which is formed so as to surround an outer circumference of the core concentrically with the core, the clad having at least an inner cladding layer adjacent to the outer circumference of the core and an outer cladding layer formed on an outer circumference of the inner cladding layer, wherein a refractive index of the outer cladding layer is Δ3, and an outer circumference radius of the outer cladding layer is r3, a relationship of Δ1max>Δ3>Δ2min is satisfied, a relationship of Δ3−Δ2min≦0.08% is satisfied, a relationship of r1<r2<r3 is satisfied, a relationship of 0.35≦r1/r2≦0.55 is satisfied, a cable cut-off wavelength is less than or equal to 1260 nm, and an MFD at a wavelength of 1310 nm is 8.6 μm to 9.2 μm.

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.

The invention concerns a multimode optical fiber, with an ct-profile graded-index core with an a-value between 1.96 and 2.05 and a N value defined as N=(R.sub.1/λ).sup.2(n.sub.1.sup.2−n.sub.0.sup.2) between 7 and 52, where R.sub.1 is the multimode core radius, n.sub.1 is the maximum index of the multimode core and n.sub.0 is the minimum index at the outer edge of the graded index core. According to the invention, a depressed region directly surrounds the graded/index core and satisfies the criteria: −2.20<Dn.sub.2<0, where Dn.sub.2 is the index difference of depressed region with external cladding, and 220 Ln(N)−1100<V.sub.2<220Ln(N)−865, where V.sub.2 is the volume of the depressed region. Such a multimode fiber shows an increased OFL-bandwidth above 10000 Hz.Math.km at an operating wavelength between 950 nm and 1310 nm.

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.

A single mode optical fiber having a core made from silica and less than or equal to about 11 weight % germania and having a maximum relative refractive index Δ.sub.1MAX. The optical fiber also has an inner cladding surrounding the core and having a minimum relative refractive index Δ.sub.2MIN, a first outer cladding surrounding the inner cladding and a second outer cladding surrounding the first outer cladding. The viscosity at 1650° C. of the second outer cladding minus the viscosity at 1650° C. of the first outer cladding is greater than 0.1e.sup.7 Poise, and Δ.sub.1MAX>Δ.sub.2MIN. The single mode optical fiber may also have an outer cladding surrounding the inner cladding made from silica or SiON. The first outer cladding has a maximum relative refractive index Δ.sub.3MAX, and Δ.sub.3MAX>Δ.sub.2MIN.

A preform for making a vortex optical fiber comprises a glass cylinder formed substantially of silicone dioxide that defines a core portion along a longitudinal axis of the glass cylinder and a cladding portion surrounding the core portion. The glass cylinder further defines a plurality of holes running parallel to the longitudinal axis from a first end of the glass cylinder to a second end of the glass cylinder.