In an optical fiber, a plurality of individual cores extend through a common cladding. Each individual core supports at least one local transverse spatial mode. The individual cores and surrounding cladding are structured to support propagation of plurality of desired signal-carrying modes, while suppressing undesired modes, thereby supporting the propagation of one or more spatially multiplexed signals. The core-to-core spacing of the fiber is configured to maintain an acceptably low level of mode-coupling between cores.

A fiber connector, comprising a housing comprising a region extending in a lengthwise direction an optical fiber disposed in the region, a first portion of the optical fiber comprising an inner core, a cladding layer surrounding the core, and a first outer polymer layer surrounding the cladding layer and a second portion of the optical fiber comprising the inner core, the cladding layer surrounding the core and a second outer polymer layer that is different from the first polymer layer.

Described is a technique for optimizing the design and manufacture of broadband MMFs. MMFs for use in CWDM applications are specifically described.

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 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 fiber optic cable includes a jacket forming a cavity therein, the jacket having an indentation on the exterior thereof that forms a ridge extending into the cavity along the length of the jacket; and a stack of fiber optic ribbons located in the cavity, each ribbon having a plurality of optical fibers arranged side-by-side with one another and coupled to one another in a common matrix, wherein corners of the ribbon stack pass by the ridge at intermittent locations along the length of the jacket, and wherein interaction between the ridge and the ribbon stack facilitates coupling of the ribbon stack to the jacket.

An optical fiber includes a core, a first clad that is provided on an outer circumferential portion of the core and has a refractive index lower than that of the core, and a second clad that is provided on an outer circumferential portion of the first clad and has a refractive index lower than that of the first clad. In the optical fiber, a mode field diameter at a wavelength of 1.55 μm is equal to or greater than 11.5 μm, a cutoff wavelength is equal to or less than 1.53 μm, a bending loss at a bending radius of 30 mm and a wavelength of 1.625 μm is equal to or less than 2.0 dB/100 turns, and a delay time of transmission light per unit length at a wavelength of 1.55 μm is equal to or less than 4.876 μs/km.

An optical fiber according to an embodiment includes a core and a cladding. The average value n1_ave of the refractive index of the core, the minimum value nc_min of the refractive index of the cladding, and the refractive index n0 of pure silica glass satisfy relationships of n1_ave>nc_min and nc_min<n0. The cladding contains fluorine. The fluorine concentration in the cladding is adjusted to be minimum in the outermost portion of the cladding including the outer peripheral surface of the cladding.

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.

An optical fiber includes: a core portion made of glass; and a cladding portion made of glass, having a refractive index lower than the refractive index of the core portion, and positioned on an outer periphery of the core portion. Further, the cladding portion has an outer diameter smaller than 100 μm, and the core portion has a relative refractive-index difference of 0.32% to 0.40% with respect to the cladding portion.