Surface-modified glass fiber, comprising: a core made of a first glass fiber material; a surface layer that encloses the core completely in a sheath-like way; wherein the surface layer has a higher silicon dioxide percentage and a higher porosity compared to the core.

A method of drawing a material into sheet form includes forming a preform comprising at least one material as a large aspect ratio block wherein a first transverse dimension of the preform is much greater than a second transverse dimension substantially perpendicular to the first transverse dimension. A furnace having substantially linearly opposed heating elements one spaced from the other is provided and the heating elements are energized to apply heat to the preform to create a negative thermal gradient from an exterior surface along the first transverse dimension of the preform inward toward a central plane of the preform. The preform is drawn in such a manner that the material substantially maintains its first transverse dimension and deforms across its second transverse dimension.

A glass fiber including a plurality of flat-cross-section glass filaments each having a cross-section in flat shape, the cross-section having a major axis in the range of 15.0 to 25.0 m, a minor axis in the range of 8.0 to 12.0 m, and an irregular shape ratio R, being the ratio of the major axis to the minor axis (major axis/minor axis), in the range of 1.5 to 3.0. The flat-cross-section glass fiber has a packing rate P, being the ratio of the cross-sectional area of each flat-cross-section glass filament to the area of a rectangle circumscribing the cross-section of the flat-cross-section glass filament, in the range of 80.1 to 89.9%, and the irregular shape ratio R and the packing rate P satisfy the following formula (1):

337.6P.sup.3/2/R421.2 (1).

A glass fiber including a plurality of flat-cross-section glass filaments each having a cross-section in flat shape, the cross-section having a major axis in the range of 15.0 to 25.0 m, a minor axis in the range of 8.0 to 12.0 m, and an irregular shape ratio R, being the ratio of the major axis to the minor axis (major axis/minor axis), in the range of 1.5 to 3.0. The flat-cross-section glass fiber has a packing rate P, being the ratio of the cross-sectional area of each flat-cross-section glass filament to the area of a rectangle circumscribing the cross-section of the flat-cross-section glass filament, in the range of 80.1 to 89.9%, and the irregular shape ratio R and the packing rate P satisfy the following formula (1): 337.6P.sup.3/2/R421.2 . . . (1).

An optical fiber is formed from silica-based glass. The optical fiber includes a core including a central axis and a cladding surrounding the core. A refractive index of the core is greater than a refractive index of the cladding. The core contains chlorine, and one or more kinds of elements selected from an element group consisting of alkali metal elements and alkaline earth metal elements. A relative refractive index difference of the core based on a refractive index of pure silica is 0.00% or greater and 0.15% or less. An average concentration of fluorine in the cladding is 1.2% or less in a mass fraction.

A method of drawing a material into sheet form includes forming a preform comprising at least one material as a large aspect ratio block wherein a first transverse dimension of the preform is much greater than a second transverse dimension substantially perpendicular to the first transverse dimension. A furnace having substantially linearly opposed heating elements one spaced from the other is provided and the heating elements are energized to apply heat to the preform to create a negative thermal gradient from an exterior surface along the first transverse dimension of the preform inward toward a central plane of the preform. The preform is drawn in such a manner that the material substantially maintains its first transverse dimension and deforms across its second transverse dimension.

Provided are a high-efficiency parallel-beam laser optical fiber drawing method and optical fiber, the method including the steps of: S1: providing base planes on the side surfaces of both a gain optical fiber preform and a pump optical fiber preform, inwardly processing the base plane of the gain optical fiber preform to make a plurality of ribs protrude, and inwardly providing a plurality of grooves on the base plane of the pump optical fiber preform; S2: embedding the ribs into the grooves, tapering and fixing one end of the combination of the ribs and the grooves to form a parallel-beam laser optical fiber preform; S3: drawing the parallel-beam laser optical fiber preform into parallel-beam laser optical fibers. The process has high repeatability, and the obtained parallel-beam laser achieves peelability of pump optical fibers in a set area, thus facilitating multi-point pump light injection of parallel-beam laser optical fibers.

A method of drawing a material into sheet form includes forming a preform comprising at least one material as a large aspect ratio block wherein a first transverse dimension of the preform is much greater than a second transverse dimension substantially perpendicular to the first transverse dimension. A furnace having substantially linearly opposed heating elements one spaced from the other is provided and the heating elements are energized to apply heat to the preform to create a negative thermal gradient from an exterior surface along the first transverse dimension of the preform inward toward a central plane of the preform. The preform is drawn in such a manner that the material substantially maintains its first transverse dimension and deforms across its second transverse dimension.

The present invention provides an optical fiber and method of making the same. The optical fiber includes a body for transmitting light. The body has an anisotropic refractive index wherein the anisotropic refractive index offsets changes in the refractive index of the fiber caused by bending the fiber. The fiber body may further include a core and cladding.

A method of producing a conversion element includes forming a preform from a glass, reshaping the preform into a structured glass fiber using a structuring element, and dividing the glass fiber into conversion elements.