Abstract: The specification describes the production of optical fibers and optical fiber preforms using Chemical Powder Deposition (CPD). In this process a slurry of silica powders and dopant powders in a liquid carrier is prepared and the inside surface of a silica glass starter tube is coated with the slurry, then dried. The coating is then consolidated and the tube collapsed as in the conventional MCVD process. Multiple coatings, and coatings with varying compositions, can be used to produce any desired profile. In an alternative embodiment, doped silica glass of the desired final composition is prepared, and then pulverized to form the powder for the slurry. In both embodiments, the use of powders of known composition in the slurry allows direct control over the final glass composition, as compared with conventional processes in which the composition in the final glass is indirectly controlled by control of the thermodynamics of a vapor phase reaction.

Abstract: The use of large dense vitreous spherical (LDVS) silica powders for making sol-gel silica bodies has been found to have important advantages. Among these are higher gel strength, higher silica loading, more rapid aging and drying of the gel, a reduction in the amount of organic additives leading to reduced process time required for organic burn-off, and easier removal of contaminant particles due to their larger size. It was also discovered that combining LDVS particles with conventional non-spherical, lower density, aggregate particle mixtures, further improves the process.

Abstract: The specification describes the production of optical fibers and optical fiber preforms using Chemical Powder Deposition (CPD). In this process a slurry of silica powders and dopant powders in a liquid carrier is prepared and the inside surface of a silica glass starter tube is coated with the slurry, then dried. The coating is then consolidated and the tube collapsed as in the conventional MCVD process. Multiple coatings, and coatings with varying compositions, can be used to produce any desired profile. In an alternative embodiment, doped silica glass of the desired final composition is prepared, and then pulverized to form the powder for the slurry. In both embodiments, the use of powders of known composition in the slurry allows direct control over the final glass composition, as compared with conventional processes in which the composition in the final glass is indirectly controlled by control of the thermodynamics of a vapor phase reaction.

Abstract: The doped silica core region of a core rod for an optical fiber preform is protected against unwanted fluorine doping during fluorine doping of the outer silica layer by selectively consolidating the core region prior to fluorine doping. Due to dopants in the core region, the soot in the core region consolidates before the soot in the outer undoped region. This inherent property allows the entire core rod to be heated prior to fluorine doping resulting in selective partial consolidation and preventing fluorine doping of the doped center core region. The process time required may be reduced by using incremental fluorine doping. In the incremental doping process the doping step is separated into a deposit step, where “excess” fluorine is deposited on the silica particles, and a drive-in step where atomic fluorine is distributed into the silica particles. The drive-in step is conveniently combined with the sintering or consolidation step to further enhance the efficiency of the doping process.

Abstract: The specification describes optical fibers that are constructed to prevent theft of optical signals. One construction is designed to block access of the core of the fiber to the “writing” radiation necessary to form a grating tap. In this embodiment the optical fiber cladding is provided with a highly absorbing UV layer. In a variation of this embodiment, one or more additional optical paths are provided in the optical fiber to accommodate monitoring signals. The added optical paths allow monitoring signals to be transmitted in the optical fiber, separate from the information signal, to signal an attempt to breach the outer coating or the cladding of the optical fiber. A second case of intrusion is addressed by increasing the sensitivity of the optical fiber to microbending loss to the extent that bends in the fiber cause such high attenuation of the signal that the bends do not go undetected at the receiving station.

Abstract: The use of large dense vitreous spherical (LDVS) silica powders for making sol-gel silica bodies has been found to have important advantages. Among these are higher gel strength, higher silica loading, more rapid aging and drying of the gel, a reduction in the amount of organic additives leading to reduced process time required for organic burn-off, and easier removal of contaminant particles due to their larger size. It was also discovered that combining LDVS particles with conventional non-spherical, lower density, aggregate particle mixtures, further improves the process.

Abstract: The doped silica core region of a core rod for an optical fiber preform is protected against unwanted fluorine doping during fluorine doping of the outer silica layer by selectively consolidating the core region prior to fluorine doping. Due to dopants in the core region, the soot in the core region consolidates before the soot in the outer undoped region. This inherent property allows the entire core rod to be heated prior to fluorine doping resulting in selective partial consolidation and preventing fluorine doping of the doped center core region. The process time required may be reduced by using incremental fluorine doping. In the incremental doping process the doping step is separated into a deposit step, where “excess” fluorine is deposited on the silica particles, and a drive-in step where atomic fluorine is distributed into the silica particles. The drive-in step is conveniently combined with the sintering or consolidation step to further enhance the efficiency of the doping process.

Abstract: The process time required for fluorine doping of porous silica bodies to produce fluorine doped preforms for the manufacture of depressed index optical fibers is reduced by separating the doping step into a predeposit step, where “excess” fluorine is deposited on the silica particles, and a drive-in step where atomic fluorine is distributed into the silica particles. The drive-in step is conveniently combined with the sintering or consolidation step to further enhance the efficiency of the doping process.

Abstract: The process time required for fluorine doping of porous silica bodies to produce fluorine doped preforms for the manufacture of depressed index optical fibers is reduced by separating the doping step into a predeposit step, where “excess” fluorine is deposited on the silica particles, and a drive-in step where atomic fluorine is distributed into the silica particles. The drive-in step is conveniently combined with the sintering or consolidation step to further enhance the efficiency of the doping process.

Abstract: The use of silica powders having large particle sizes in making sol-gel silica bodies has been found to have important advantages. Among these are higher gel strength, higher silica loading, more rapid aging and drying of the gel, a reduction in the amount of organic additives leading to reduced process time required for organic burn-off, and easier removal of contaminant particles due to their larger size. It was also discovered that spherical particle morphology contributes to the improved properties.

Abstract: A tube take-up apparatus is provided to handle a length of freshly extruded tube. The apparatus includes an elongated housing in which a pair of parallel, spaced-apart rollers extend lengthwise in a position just below the extruded tubing. The housing is removably mounted on an elongated supporting fin which is secured to the extruder at its near end, extends upwardly between the two rollers and substantially along the entire length of the housing, and is, in turn, supported on a fixed pedestal at its remote end. After the full length of tubing has been extruded, the housing and rollers as a unit are lifted with the tube from the supporting fin and replaced by an empty housing, to extrude the next tube, while the full housing is carried away to a dryer.

Abstract: The specification describes optical fibers that are constructed to prevent theft of optical signals. One construction is designed to block access of the core of the fiber to the “writing” radiation necessary to form a grating tap. In this embodiment the optical fiber cladding is provided with a highly absorbing UV layer. In a variation of this embodiment, one or more additional optical paths are provided in the optical fiber to accommodate monitoring signals. The added optical paths allow monitoring signals to be transmitted in the optical fiber, separate from the information signal, to signal an attempt to breach the outer coating or the cladding of the optical fiber.

Abstract: The use of silica powders having large particle sizes in making sol-gel silica bodies has been found to have important advantages. Among these are higher gel strength, higher silica loading, more rapid aging and drying of the gel, a reduction in the amount of organic additives leading to reduced process time required for organic burn-off, and easier removal of contaminant particles due to their larger size. It was also discovered that spherical particle morphology contributes to the improved properties.

Abstract: The disclosed method of making microstructured optical fiber comprises providing a mold, with a multiplicity of elongate elements extending into the mold and being maintained in a predetermined spatial arrangement with respect to the mold. Silica-containing sol is introduced into the mold and is caused to or permitted to gel, such that a gel body results. After removing the elongate elements from the gel body and removing the gel body from the mold, the gel body is dried, sintered and purified, and the microstructured fiber is drawn from the sintered body.

Abstract: A silica-water dispersion suitable for use as a sol for sol-gel fabrication is produced from a silica-water mixture with addition of alkaline agent. The agent functions to increase viscosity so as to improve dispersing efficiency during shear mixing.

Abstract: The invention is a sol-gel extrusion process which allows fabrication of both thick and thin wall tubes. For example, the process is capable of preparing silica overcladding tubes in a manner easier than sol-gel casting processes, and also capable of preparing relatively thin substrate tubes, which are difficult to cast. According to the invention, a silica dispersion containing a stabilizing agent is provided, a gelling agent is added to the dispersion to induce gellation, and the resultant gel is extruded into a silica body, in the substantial absence of polymeric material from the gel. Substantially avoiding the inclusion of such polymeric material in overcladding and substrate tubes offers significant commercial advantages by reducing the time and energy required to remove organic materials from the tube bodies, by reducing environmental impact, and by reducing the amount of impurities introduced in the tubes.

Abstract: The specification describes sputtering processes for the deposition of silicon dioxide films doped with high levels of oxides or other materials to alter the optical and/or electrical characteristics of the films. Sol gel methods are used to prepare composite sputtering targets of ultra fine mixtures of materials so the composition of the sputtered films replicate the composition of the target.

Abstract: Cracking in thin sheets of sol-gel-produced material is avoided by use of a support liquid during gelation and drying. Silica glass, as well as other glass and ceramic bodies, is contemplated.

Abstract: A novel planar waveguide structure has been constructed by sintering substantially pure SiO.sub.2 layers in a He.sub.2 /BCl.sub.3 atmosphere. This results in the generation of a liquid phase of substantially lower viscosity than that of the deposited silica by itself. Since viscous sintering is enhanced by the presence of this liquid, consolidation occurs at lower temperature, e.g. 1000.degree.-1100.degree. C., than those used in the prior art, e.g. 1350.degree.-1500.degree. C. Much of the B.sub.2 O.sub.3 remains unreacted with the silica particles it helps to sinter, acting like a flux to bring about consolidation. This remaining B.sub.2 O.sub.3 is removed at the conclusion of the consolidation procedure by steam treatment at temperatures of 900.degree.-1100.degree. C. Some boron is incorporated into the silica layer, changing its CTE without substantially increasing its index.

Abstract: This application discloses a technique for producing optical fibers with longitudinal variations in index of refraction. The deposition apparatus is arranged to allow for the formation of an intertwined double helix of two different materials. The technique does not require imposing any time dependent conditions on the fabrication apparatus.