A method for manufacturing of an optical fibre preform (100) using optimized core particles includes optimization of particles of calcium aluminum silicate powder (104), utilizing the optimized core particles, sintering the optimized core particles inside a fluorine doped glass tube (106) and drawing of an optical fibre. Particularly, the optimization of the particles of calcium aluminum silicate powder (104) facilitates formation of the optimized core particles and the optimized core particles are filled inside the fluorine doped glass tube (106). Moreover, sintering of the optimized core particles solidifies and adheres smoothly with the fluorine doped glass tube (106) for manufacturing of the optical fibre preform (100).

A method for drawing an optical fibre from an optical fibre preform with a core section, a cladding section, a first gap and a second gap. The optical fibre preform is attached to an optical fibre draw tower through a handle. In addition, the optical fibre preform is connected to a vacuum system to supply and remove gas from the first gap and the second gap. Moreover, the gas is supplied to create a thermal barrier between the core section and the cladding section during heating of the optical fibre preform. Further, the optical fibre preform is heated inside a heating furnace to draw the optical fibre from the optical fibre preform.

A reduced diameter optical fibre preform positioned along a longitudinal axis includes a core section defined around the longitudinal axis and a cladding section circumferentially surrounding the core section. The reduced diameter optical fibre preform is manufactured by utilizing a calcium aluminum silicate rod and a fluorine doped glass cylinder.

An optical fibre including a core region defined along a central longitudinal axis of the optical fibre and a cladding region concentrically surrounds the core region of the optical fibre. In particular, the core region has a first radius r.sub.1 and a first refractive index n.sub.1. Moreover, the cladding has a second radius r.sub.2 and a second refractive index n.sub.2. Furthermore, the optical fibre has a step index profile.

A method of fabricating an optical fiber, the method including providing a core portion including a doped portion having greater than or equal to 1.6 wt. % of a halide dopant and eliminating seed precursor sites at an exterior surface of the core portion, the seed precursor sites forming seeds in the optical fiber, wherein the eliminating the seed precursor sites includes one or more of: (i) fabricating the core portion by densifying an exterior portion of a silica soot body prior to exposing the silica soot body to the halide dopant, and (ii) exposing the exterior surface of the core portion to a reactive etchant. The method further including forming an optical fiber preform by applying cladding material to the exterior surface of the core portion and drawing the fiber preform into the optical fiber.

An optical fiber according to an embodiment includes a core, a cladding, and a coating layer. At the boundary between the core and the cladding, the local sound velocity decreases in the direction from the core side toward the cladding side. At least in the cladding, the local sound velocity changes continuously in a radial direction. Further, the line width of the Brillouin gain of the light beam guided by the fundamental mode is 60 MHz or more.

The production and new type of preforms are presented which yield, upon drawing, new, class of optical fibers, improved, speckle-free output optical fibers. Useful fibers, providing speckle-free, smooth output with flat top transmission of light from gaussian or few mode sources are produced from preforms introduced herein. The unique production of these improved preforms is also presented. The preforms, and thus the fibers produced in varying core dimensions from about 100 μm to above 1000 μm, are based on a structured silica section of mode mixing area adjacent to the inner core, or in the case of non-circular core, within the core. Plasma Vapor Deposition process is modified to achieve the structured sections in a well-controlled manner. The structured sections are composed of a number of pairs of layers, where a thin down-doped layer is alternated with a much thicker core material layer. The ratio of the thickness of the core layer to the thickness of the down-doped layer is about 3 to 25. The number of paired layers is typically between about 8 to 30-layer pairs. The effective NA of the structured section is dependent on the particulars of the structured silica section and of the individual down-doped layer. Both circular inner core examples and non-circular core examples are possible and are discussed, herein.

According to embodiments, a method of making a microstructured glass article includes bundling M bare optical fibers in a fiber bundle, wherein M is an integer greater than 100. Thereafter, the fiber bundle may be inserted in a cavity of a soot preform. The soot preform may have a density of less than or equal to 1.5 g/cm.sup.3 and comprise silica-based glass soot. The soot preform and inserted fiber bundle may then be consolidated to form a microstructured glass article preform. The microstructured glass article preform may then be drawn into the microstructured glass article comprising M core elements embedded in a cladding matrix.

A method for producing rare earth metal-doped quartz glass includes the steps of (a) providing a blank of the rare earth metal-doped quartz glass, and (b) homogenizing the blank by softening the blank zone by zone in a heating zone and by twisting the softened zone along a rotation axis. Some rare earth metals, however, show a discoloration of the quartz glass, which hints at an unforeseeable and undesired change in the chemical composition or possibly at an inhomogeneous distribution of the dopants. To avoid this drawback and to provide a modified method which ensures the production of rare earth metal-doped quartz glass with reproducible properties, during homogenization according to method step (b), the blank is softened under the action of an oxidizingly acting or a neutral plasma.

An optical fiber containing alkali metal elements or the like in which Rayleigh scattering loss can be reduced is provided. An optical fiber includes a core composed of silica glass and a cladding which surrounds the core, has a refractive index lower than a refractive index of the core, and is composed of silica glass containing fluorine. The core contains a first group of dopants and a second group of dopants having a diffusion coefficient lower than a diffusion coefficient of the first group of dopants. The difference between the maximum value and the minimum value of residual stress in the optical fiber is 150 MPa or less.