The manufacture of fiberglass filtration media, and particularly paint arrestance fiberglass media, is disclosed. Fiberglass filtration media is formed in part by controlling the speed of a melter traversing a drum. The fiberglass media passes through rollers and water sprays before it enters a curing apparatus. Progressive density changes from the air intake side to the air exit side of the media result in increased filtration qualities.

An optical fiber with low attenuation is provided. The fiber is produced under conditions that reduce fictive temperature. Processing includes maintaining the fiber at temperatures at or near the glass transition temperature (T.sub.g) for an extended period of time. For silica-based fibers, the preferred temperatures are temperatures between 1000 C. and 1700 C. The extended residence times are achieved in a continuous fiber manufacturing process by increasing the path length of the fiber through a processing region maintained at temperatures between 1000 C. and 1700 C. The increased path length is achieved by including one or more fluid bearing devices in the processing region. The extended residence time in the processing region allows the structure of the glass fiber to relax more completely and to more closely approach the equilibrium state. The more relaxed glass structure leads to a lower fictive temperature and provides fibers with lower attenuation.

The present invention, as disclosed and described herein, in one aspect thereof comprises a preform for making a vortex optical fiber includes a glass cylinder formed substantially of silicone dioxide that defines a core portion along a longitudinal axis of the glass cylinder and a cladding portion surrounding the core portion. The glass cylinder further defines a plurality of holes running parallel to the longitudinal axis from a first end of the glass cylinder to a second end of the glass cylinder.

A drawn glass element for producing glass optical waveguides is provided. The element has two first length portions with a first cross-sectional area and which define the two ends of the glass element; a second, intermediate length portion between the two first length portions, which has a second cross-sectional area smaller than the first cross-sectional area; a first transition portion between the intermediate length portion and one of the first length portions; and a second transition portion between the intermediate length portion and another of the first length portions. The first and second transition portions have a cross-sectional area that steadily changes and merges from the first cross-sectional area into the second cross-sectional area.

Aspects of the embodiments include an optical fiber formed in a low gravity environment. The optical fiber can be used in airframe applications for missile defense, oil-field applications for down-well laser applications, optical communications, and other applications. The optical fiber can include a fluoride composition, such ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN), and can be characterized by an insertion loss in a range from 13 dB/1000 km to 120 dB/1000 km. The optical fiber can deliver optical energy with low insertion loss at the desired power and wavelength for the various applications.

A preform for making a vortex optical fiber comprises a glass cylinder formed substantially of silicone dioxide that defines a core portion along a longitudinal axis of the glass cylinder and a cladding portion surrounding the core portion. The glass cylinder further defines a plurality of holes running parallel to the longitudinal axis from a first end of the glass cylinder to a second end of the glass cylinder.

There is provided an optical fiber for providing increased sensitivity in sensing applications by increasing the Rayleigh backscatter coefficient of the fiber while maintaining tolerable levels of signal attenuation (e.g., less than 20% over 10 km). Such an optical fiber comprises a core, a first cladding layer and a second cladding layer. The core comprises at least one core dopant selected from the range of: germanium, phosphorus, aluminium, boron, fluorine. The at least one core dopant is used to increase the core refractive index and enhance the core Rayleigh backscatter coefficient. The first cladding layer comprises at least one dopant selected from: germanium, phosphorus, aluminium, boron, fluorine; wherein at least one first cladding layer dopant is used to reduce the first cladding layer refractive index. The signal attenuation generated in the fiber is less than 20% over 1 km.

A fluid bearing for directing optical fibers during manufacturing is presented. The fluid bearing provides a flow of fluid to levitate and direct an optical fiber along a process pathway. The optical fiber is situated in a fiber slot and subjected to an upward force from fluid flowing from an inner radial position of the fiber slot past the optical fiber to an outer radial position of the fiber slot. The levitating force of fluid acting on the optical fiber is described by a convex force curve, according to which the upward levitating force on the optical fiber increases as the optical fiber moves deeper in the slot. Better stability in the positioning of the optical fiber in the fiber slot is achieved and contact of the optical fiber with solid surfaces of the fluid bearing is avoided. Various fluid bearing structures for achieving a convex force curve are described.

A preform material including a starter tip to facilitate an initial fiber draw from the preform within a furnace, wherein the tip comprises a vacuum-sealed tip to receive a plastic grip which attached to an end of a preform.

An apparatus for manufacturing an optical fiber including: a drawing portion; a coating portion; and a curing portion, wherein: a direction changer which changes a direction of the bare optical fiber is disposed in any position from the drawing portion to the coating portion; the direction changer includes a guide groove which guides the bare optical fiber; a blowout port of a fluid which floats the bare optical fiber wired along the guide groove is formed along the guide groove in the guide groove; and in the blowout port, the Reynolds number in an inlet wire portion of the bare optical fiber to the guide groove and an outlet wire portion from the guide groove is greater than the Reynolds number in an intermediate portion between the inlet wire portion and the outlet wire portion.