A method of manufacturing a multimode optical fiber includes specifying a peak wavelength λ.sub.P for the multimode optical fiber. The peak wavelength λ.sub.P corresponds to a wavelength at which the multimode optical fiber has a maximum bandwidth. The multimode optical fiber comprises a core and a cladding surrounding and directly adjacent to the core. The core has a radius r.sub.1 and a maximum relative refractive index Δ.sub.1,MAX>0. The cladding comprises a depressed-index region having a minimum relative refractive index Δ.sub.3,MIN<0 and a volume v. A draw tension T for the multimode optical fiber is selected based on a correlation relating peak wavelength λ.sub.P to draw tension T, the correlation comprising a correlation constant. The correlation constant K is a function of at least one of Δ.sub.1,MAX, r.sub.1, v, Δ.sub.3,MIN, and λ.sub.P. The multimode optical fiber is drawn from a preform at the draw tension T.

Embodiments of the current disclosure include small diameter single-mode optical fibers having gratings and methods of forming thereof. In some embodiments, methods of forming a small diameter single-mode optical fibers having gratings include providing an optical fiber having a core and cladding with a combined outer diameter of 100 μm to 125 μm and a coating having a thickness of less than or equal to 20 μm, wherein the coating comprises one of: (i) a high-modulus coating layer surrounding the cladding region; or (ii) a low-modulus coating layer surrounding the cladding region and a high-modulus coating layer surrounding the low-modulus coating layer; and exposing the core, through the coating, to a pattern of ultraviolet radiation to form an optical grating within the core.

An array-type polarization-maintaining multi-core fiber includes a main outer cladding, fiber core units, and stress units. The fiber core units and the stress units are arranged to form a unit array including one central unit and any unit in the unit array being equidistantly arranged from adjacent units thereof. Provided is at least one pair of stress units, each pair of stress units being arranged symmetrical about one fiber core unit to form a polarization-maintaining fiber core unit. The fiber core units each include a fiber core and an inner cladding surrounding a core layer. A portion outside the fiber core units and the stress units is the main outer cladding. The fiber can greatly enhance spectral efficiency of an optical transmission system, and improve fiber communication capacity.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

A method of manufacturing a tuned optical fiber includes providing a first preform from a set of like preforms each having substantially the same refractive index profile, including amount of axial variation relative to a target refractive index profile. The method includes drawing a reference optical fiber from the first preform and measuring a variation in an optical or physical property as a function of axial position. The method also includes drawing from a second preform from the set of like preforms the tuned optical fiber. The drawing includes using a time-varying tension that reduces the amount of variation of the optical or physical property of interest. The time-varying tension is defined by an amount of axial stress imparted to the tuned fiber needed to alter the refractive index profile and the at least one optical or physical property based on a stress-optic effect.

An optical fiber includes: a central core portion; an intermediate layer formed around an outer circumference of the central core portion; a trench layer formed around an outer circumference of the intermediate layer; and a cladding portion formed around an outer circumference of the trench layer. Further, when, relative to the cladding portion, a relative refractive-index difference of the central core portion is Δ1, a relative refractive-index difference of the intermediate layer is Δ2, and a relative refractive-index difference of the trench layer is Δ3, relationships Δ1>Δ2>Δ3 and 0>Δ3 are satisfied and Δ1 is equal to or greater than 0.34% and equal to or less than 0.40%, |Δ3| is equal to or less than 0.25%, and Δ1×|Δ3| is less than 0.08%.sup.2.

The present disclosure provides optical fibers that exhibit low macrobend loss at 1550 nm at bend diameters greater than 40 mm. The relative refractive index profile of the fibers includes a trench cladding region having a trench volume configured to minimize macrobend loss at large bend diameters. The thickness and/or depth of the trench cladding region are controlled to reduce trench volume to a degree consistent with reducing macrobend loss at bend diameters greater than 40 mm. The optical fiber includes an outer cladding region that surrounds and is directly adjacent to the trench cladding region and an optional offset cladding region between the trench cladding region and the core region. In some embodiments, the core region is a segmented core region that includes inner and outer core regions. The low macrobend loss available from the optical fibers makes them particularly suitable for applications in submarine telecommunications systems.

An optical fiber sensor with high sensitivity and high spatial resolution is described. The optical fiber sensor includes a multicore fiber having cores configured to permit crosstalk between cores. Crosstalk corresponds to transfer of an optical signal from a core to another core and is used as a mechanism for sensing the external environment surrounding the multicore optical fiber. The degree of crosstalk depends on the relative refractive index profile of the cores and surrounding cladding, as well as on the spacing between cores. The external environment surrounding the multicore optical fiber and changes therein influence crosstalk between cores to permit sensing. The relative refractive index profiles of the cores are also configured to provide a group delay difference for optical signals propagating in different cores. The group delay difference facilitates the position of an external perturbation along the length of the multicore optical fiber.

A rollable optical fiber ribbon utilizing low attenuation, bend insensitive fibers and cables incorporating such rollable ribbons are provided. The optical fibers are supported by a ribbon body, and the ribbon body is formed from a flexible material such that the optical fibers are reversibly movable from an unrolled position to a rolled position. The optical fibers have a large mode filed diameter, such as ≥9 microns at 1310 nm facilitating low attenuation splicing/connectorization. The optical fibers are also highly bend insensitive, such as having a macrobend loss of ≤0.5 dB/turn at 1550 nm for a mandrel diameter of 15 mm.

The present disclosure provides an optical fibre (100). The optical fibre (100) includes a glass core (102), a trench region (106) and a cladding (108). The trench region (106) has a trench curve parameter α.sub.trench in range of 5 to 8. The optical fibre (100) has a mode field diameter in range of 8.7 micrometers to 9.7 micrometers at wavelength of 1310 nanometer.