Abstract: Low signal attenuation optical fibers and methods for making such fibers mimimize the internal and interface defects while providing high throughput by radial deposition of successive particulate layers about a small diameter start element and co-vitrification of the layers followed by drawing to the small final diameter that is desired. Radial vapor deposition of an interface layer on the start element, followed by an encompassing core and then a cladding provides boundaries that form transitional continuums after the structure has been vitrified. The start element remains as part of the core but is so small as to have no discernible effect on light propagation, and the number of interfaces in the light propagating portion is limited by maintaining the ratio of the cladding thickness to the core radius to less than 1.5 in the initial preform. By drawing this preform to form separate rods, additional cladding is applied to form a fiber preform from which optical fibers may be drawn.

Abstract: A process for manufacturing a preform from which is drawn an optical fiber, the core of which comprises layers of different glass composition. In one embodiment, the known CVD process for making preforms is modified by halting rotation of the substrate tube while the tube is asymmetrically heated by a source that traverses the length of the tube. A vapor mixture flowing through the tube reacts only near that region of the inner surface of the tube that is being heated. This forms a longitudinal strip of glass particles. The flow of reactants stops, the tube is rotated, and it is traversed by heating means which heats the tube to a temperature sufficiently high to fuse the glass particles and forming a longitudinal strip of glassy material.

Abstract: A single mode optical waveguide is fabricated in a manner such that the core thereof is subjected to a stress-induced birefringence. A hollow intermediate product is formed by depositing layers of cladding and core glass on the inner surface of a substrate tube. Opposite sides of the intermediate product are heated to cause it to collapse into a solid preform foreproduct having an oblong cross-section. A layer of flame hydrolysis-produced soot having a circular outer surface is deposited on the preform foreproduct and is consolidated to form a dense glass cladding layer thereon. The TCE of the outer cladding layer is different from that of the preform foreproduct on which it is deposited so that when the resultant preform is drawn into a fiber, a stress-induced birefringence exists in the core.

Abstract: A glass optical waveguide filament preform is prepared by chemical reaction of vapor ingredients within a glass bait tube. As the reactants flow through the bait tube, a hot zone traverses the tube to cause the deposition of sooty reaction products in the region immediately downstream of the hot zone. A baffle tube extends into that end of the bait tube into which the reactants flow. The baffle tube, which traverses the bait tube along with the burner, ends just short of the hot zone so that no soot is deposited thereon. A gas flowing from the baffle tube creates a gaseous mandrel which confines the flow of reactant vapors to an annular channel adjacent the bait tube wall in the hot zone, thereby increasing deposition rate and efficiency.

Abstract: A glass optical waveguide preform is prepared by chemical reaction of vapor ingredients within a bait tube. As the reactants flow through the bait tube, a hot zone traverses the tube to cause the deposition of soot in a section of the tube just downstream of the hot zone. An axially disposed tubular burner, which is located just upstream from the hot zone, is mechanically coupled to the burner which generates the hot zone. The burner generates an axial water-free flame that extends through the hot zone. The flame creates a mandrel which confines the flow of reactants to an annular channel adjacent the bait tube wall in the hot zone. The flame also extends downstream from the hot zone where it increases the thermal gradient between the axis and the wall of the bait tube, thereby enhancing the thermophoresis effect, whereby deposition rate and efficiency are improved.

Abstract: A glass optical waveguide filament preform is prepared by chemical reaction of vapor ingredients within a glass bait tube. A reactant feed tube extends into one end of the bait tube and terminates just short of the hot zone where reaction occurs. The end of the feed tube traverses the bait tube along with the burner which generates the hot zone. Reactants flow radially from slots in the end of the wall of the feed tube and combine with a flushing gas to form a mixture which flows in a spiral path through the hot zone.

Abstract: A method of forming a preform or blank for a high bandwidth gradient index optical filament, the preform itself and the resulting optical filament is disclosed. The preform which ultimately forms the optical filament includes a barrier layer between a tubular starting member which comprises the cladding and the core, the index of refraction of the barrier layer being equal to or less than the index of refraction of the tubular starting member; there being no step increase in the index of refraction of the barrier layer at the barrier layer-cladding interface nor of the core at the core-barrier layer interface of the optical filament. The barrier layer is formed from a base glass, a first dopant B.sub.2 O.sub.3, and at least one other dopant which is maintained substantially constant in the barrier layer and then gradually varied during the formation of the core. The quantity of B.sub.2 O.sub.

Abstract: A method of forming a preform or blank for a high bandwidth gradient index optical filament, the preform itself and the resulting optical filament is disclosed. The preform which ultimately forms the optical filament includes a barrier layer between a tubular starting member which comprises the cladding and the core, the index of refraction of the barrier layer being equal to or less than the index of refraction of the tubular starting member; there being no step increase in the index of refraction of the barrier layer at the barrier layer-cladding interface nor of the core at the core-barrier layer interface of the optical filament. The tubular starting member is formed of a base glass and at least one dopant, the index of refraction of the tubular starting member being in excess of said base glass. The barrier layer is formed from a base glass and at least one dopant which is maintained substantially constant in the barrier layer.

Abstract: The application of low loss optical fibers in optical communication systems requires that the glass fibers are suitably packaged into a cable. This invention provides a system of multiple optical fibers between two tapes or films, one of which holds the fibers on the film by pressure-sensitive adhesive and in spaced relation to one another. The fibers are covered by a second film, preferably thinner than the first film, and secured to the first film along the edges of the films to provide a laminated structure suitable for cabling. Spacers between the films eliminate asymmetric pressure of the covering film against the optical fibers which are nearest to the edges of the films; and the spacers are preferably strength members for stiffening the laminate.

Abstract: This specification describes a novel apparatus and method for testing optical wave guides to determine the optical attenuation and to locate faults in the optical fiber. The light for test purposes is launched into the fiber by one or more light beams that surround the wave guides and that are focussed to converge from around the circumference and at the axis of the wave guide; the convergence being at low angles of incidence, so that some of the light enters the wave guide. The remaining light launched into the wave guide in opposite directions at a location, nearer to one end than to the other, is measured at opposite ends of the wave guide. The ratio of the light at the opposite ends of the wave guide and the difference in the length of travel of the light from the region of entry to each end is used to compute attenuation. Faults are found by internal reflections of the light beam in the wave guide.

Abstract: This optical fiber cable has the optical fibers adhered to a support. An assembly including the fibers and the support is carried by a core element having a helical channel in which the fiber assembly is located and free to adjust itself to accommodate bending of the cable without subjecting the optical fibers to pressure or to bends that are excessively sharp. The construction also avoids pressure on the optical fibers from binders, core tapes, or the cable sheath when the cable is bent. It also avoids micro-bending losses. Locating of the optical fibers closer to the cable axis further decreases bending losses.