The present invention generally relates to the field of fiber optics, and more specifically to optical fibers, methods of manufacturing optical fibers, and methods of classifying optical fibers. In an embodiment, the present invention is a multimode optical fiber which comprises a core and clad material system where the refractive indices of the core and cladding are selected to minimize chromatic dispersion in the 850 nm wavelength window and the refractive index profile is optimized for minimum modal-chromatic dispersion in channels utilizing VCSEL transceivers. Multimode optical fibers according to this embodiment may have increased channel bandwidth.

An amplification optical fiber according to the present invention includes: a core doped with an active element, through which multi-mode light propagates; an inner cladding that surrounds the core and has a refractive index lower than that of the core; and an outer cladding that surrounds the inner cladding and has a refractive index lower than that of the inner cladding. The inner cladding has a polygonal outline in a cross section perpendicular to the longitudinal direction, and the inner cladding has a permanent twist applied by turning around the central axis of the core.

The present invention generally relates to the field of fiber optics, and more specifically to optical fibers, methods of manufacturing optical fibers, and methods of classifying optical fibers. In an embodiment, the present invention is a multimode optical fiber which comprises a core and clad material system where the refractive indices of the core and cladding are selected to minimize chromatic dispersion in the 850 nm wavelength window and the refractive index profile is optimized for minimum modal-chromatic dispersion in channels utilizing VCSEL transceivers. Multimode optical fibers according to this embodiment may have increased channel bandwidth.

A method of making a multi-mode optical fiber that includes: depositing a porous germania-doped silica soot to form a germania-doped porous soot preform; depositing a porous silica layer over the porous soot preform; doping the porous soot preform and the porous silica layer with a fluorine dopant to form a co-doped soot preform having a core region and a fluorine-doped trench region; consolidating the co-doped soot preform to form a sintered glass, co-doped core preform having a refractive index alpha profile between 1.9 and 2.2 measured at 850 nm; depositing a cladding comprising silica over the sintered glass, co-doped preform to form a multi-mode optical fiber preform; drawing the optical fiber preform into a multi-mode optical fiber. Further, the step of doping the germania-doped soot preform and the porous silica layer is conducted according to a doping parameter () that is set between 20 and 300, and given by: $=\frac{1{10}^{14}{R}_{\mathrm{prc}}^2\exp \left(-E/{\mathrm{RT}}_{\mathrm{dop}}\right)T_{\mathrm{dop}}^{1/2}}{x^{3/4}}.$

An exemplary embodiment of the disclosure provides a double fiber optic mode adapter including: a fiber core having a variable core diameter; a fiber cladding having a variable cladding size; a first input interface corresponding to a first core diameter and a first cladding size; a second input interface corresponding to a second core diameter and a second cladding size; a thermally-tapered region wherein the variable core diameter of the fiber core transitions from the first core diameter to the second core diameter and the variable cladding size of the fiber cladding transitions from the first cladding size to a third cladding size; and an etched tapered region wherein the variable core diameter of the fiber core is constant and the variable cladding size of the fiber cladding transitions from the third cladding size to the second cladding size.

An optical coupling includes a planar tapered waveguide coupling element having a first end opposite a second end, a tapered waveguide positioned within a planar substrate, the tapered waveguide comprising a waveguide diameter that is larger at the first end than at the second end. An optical pathway is disposed within the tapered waveguide and extends between the first end and the second end. The tapered waveguide is tapered from the first end to the second end such that the waveguide diameter transitions a light beam traveling along the optical pathway from a first beam size at the first end to a second beam size at the second end.

Holey fibers provide optical propagation. In various embodiments, a large core holey fiber comprises a cladding region formed by large holes arranged in few layers. The number of layers or rows of holes about the large core can be used to coarse tune the leakage losses of the fundamental and higher modes of a signal, thereby allowing the non-fundamental modes to be substantially eliminated by leakage over a given length of fiber. Fine tuning of leakage losses can be performed by adjusting the hole dimension and/or spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holey fibers have a large hole dimension and spacing, and thus a large core, when compared to traditional fibers and conventional fibers that propagate a single mode. Other loss mechanisms, such as bend loss and modal spacing can be utilized for selected modes of operation of holey fibers.

It is proposed a home optical data network formed of an optical fiber comprising an optical core and an optical cladding surrounding the optical core, the optical core having a refractive graded-index profile with a minimal refractive index n.sub.1 and a maximal refractive index n.sub.0, said optical fiber being such that it has a numerical aperture NA and an optical core radius a satisfying a criterion C of quality of optical communications defined by the following equation: $C=\mathrm{NA}-0.02a$$\mathrm{where}\text{:}$$\mathrm{NA}=\sqrt{n_0^2-n_1^2}=n_0.Math.\sqrt{2}\mathrm{with}=\frac{n_0^2-n_1^2}{2n_0^2},$

Some embodiments of the disclosure relate to an optical transmission system that operates at a wavelength in the range from 950 nm to 1600 nm and that employs a single-mode optical transmitter and an optical receiver optically coupled to respective ends of a multimode fiber designed for 850 nm multimode operation. The optical transmission system also employs at least one single mode fiber situated within the optical pathway between the optical transmitter and the receiver and coupled to the multimode fiber.

An exemplary embodiment of the disclosure provides a double fiber optic mode adapter including: a fiber core having a variable core diameter; a fiber cladding having a variable cladding size; a first input interface corresponding to a first core diameter and a first cladding size; a second input interface corresponding to a second core diameter and a second cladding size; a thermally-tapered region wherein the variable core diameter of the fiber core transitions from the first core diameter to the second core diameter and the variable cladding size of the fiber cladding transitions from the first cladding size to a third cladding size; and an etched tapered region wherein the variable core diameter of the fiber core is constant and the variable cladding size of the fiber cladding transitions from the third cladding size to the second cladding size