Fitel USA Corporation

Furukawa Electric North America, Inc.

Ofs Fitel, LLC

Torben Erik Veng

David John DiGiovanni

Andrew Douglas Yablon

Lars Riis

Tonny Sorensen

Lars Gruner-Nielsen

Bera Palsdottir

Jorgen Ostgaard Olsen

Stig Nissen Knudsen

Bent Edvold

Lars Gruener-Nielsen

Dan Jakobsen

Peter Mikal Holmblad

Erling D Christensen

A technique is described for creating a localized modulation of an optical fiber's refractive index profile. A segment of optical fiber is loaded into a heating unit having a resistive heating element with a localized heating zone. A selected portion of the fiber segment is positioned within the heating zone, and the heating unit is used to create a refractive index modulation the selected fiber portion. The localized modulation is repeated along the length of the fiber segment to write a fiber grating. Also described is a resistive heating system for performing the described technique.

Systems and methods for creating localized refractive index modulations in an optical fiber

An air-clad optical fiber is provided having a core that is surrounded by an inner cladding region, an air-clad region, and an outer region. A lead end of the air-clad optical fiber is prepared for splicing by removing the air-clad region and all fiber regions outside of the air-clad region, so as to expose an inner fiber region. The prepared lead end of the air-clad optical fiber is then spliced to a lead end of the optical device. The air-clad region may be removed from a selected portion of an air-clad fiber by causing an etchant gas to stream through the air-clad region in the selected portion of the fiber. Heat is then applied to the selected fiber portion, causing at least some of the microstructure to be etched away.

Systems and methods for modifying selected portion of optical fiber microstructure

An optical fiber has a core region and a first cladding region surrounding the core. The first cladding region is doped to increase the fiber's refractive index volume. A second cladding region surrounds the first cladding region. The second cladding region is doped to reduce the fiber's cutoff wavelength, offsetting an increase in the fiber's cutoff wavelength caused by the first cladding region. An outer cladding surrounds the cutoff reduction region. In a further embodiment, the volume increasing region is doped to have a refractive index profile that is sloped to increase from the region's outer circumference towards its inner circumference. In another embodiment, the cutoff reduction region has a step refractive index profile that may have more than one section.

Optical fibers with reduced splice loss and methods for making same

Techniques are described for reducing splice loss between a pair of optical fibers. A first fiber is spliced to a second fiber at a splice point. A region of the spliced fibers, including the splice point, is thermally treated to cause a controlled diffusion of dopants in the region. A controlled tension is then applied to the splice region while heating it to a predetermined temperature to produce a controlled change in the splice region's strain state. Further described is a heat and tension station for performing a heat and tension technique on a pair of spliced fibers.

Systems and methods for reducing splice loss in optical fibers

Systems and techniques are described for fabricating a low-loss, high-strength optical transmission line. In one described technique, a first fiber is spliced to a second fiber at a splice point. The spliced fibers are loaded into a heat treatment station, where a gas torch flame is used to thermally treat a splice region including the splice point, with the thermal treatment reducing splice loss between the first and second fibers. While heating the splice region, a dry gas is purged around the torch flame during the heat treatment process to avoid water at the surface of the spliced fibers. According to further described techniques, a purging gas is fed to the torch flame to purge dust particles from the flame, and after the heat treatment has been completed, the torch flame is used to restore the glass surface of the spliced fibers. Additionally described are torch assemblies for fabricating low-loss, high-strength optical fiber transmission lines.

Systems and methods for fabricating low-loss, high-strength optical fiber transmission lines

Techniques and systems are described for reducing splice loss in an optical fiber transmission line. One described technique includes splicing together at a splice point a first fiber having a first modefield diameter to a second fiber having a second modefield diameter larger than the first modefield diameter. The splice point is heated to a core expansion temperature to cause a controlled thermal diffusion of core dopant in the first fiber in order to reduce modefield mismatch between the first and second fibers. Splice loss is then reduced by heating the splice point to a differential diffusion temperature to cause a controlled diffusion of a cladding dopant in the first fiber, while maintaining the expanded core.

Systems and methods for low-loss splicing of optical fibers

Optical fibers are described that exhibit reduced splice loss. Further described are techniques for fabricating optical fibers exhibiting reduced splice loss. One described fiber includes a plurality of regions, one region having a higher viscosity and the other region having a lower viscosity, such that when the fiber is drawn under tension, a strain is frozen into the higher viscosity region. A lower viscosity buffer layer is sandwiched between the higher viscosity region and the lower viscosity region. The buffer layer isolates the lower viscosity region from changes in refractive index in the higher viscosity region arising from a change in the strain frozen into the higher viscosity region.

A dispersion compensating fiber is described having a core and cladding as well as methods for making such fiber. The cladding has a first cladding region surrounding the core, a second cladding region surrounding the first cladding region, and a third cladding region surrounding the second cladding region. The core, and the first, second, and third cladding regions are doped to create a refraction index profile characteristic of dispersion compensating fiber. The core is doped with germanium, the first cladding region is doped with fluorine, and the second cladding region is doped with germanium and fluorine. A portion of the cladding is doped with phosphorus, thereby resulting in splice loss reduction.

Dispersion compensating fiber with reduced splice loss and methods for making same

Techniques and systems are described for splicing together first and second optical fibers. A thermal treatment station is described, having a chassis, a fiber holding block for holding a pair of optical fibers that have been spliced together at a splice point, the fiber holding block including a cutaway portion exposing the splice point, and a torch, the fiber holding block and the torch being mounted to the chassis such that the positions of the splice point and the torch can be adjusted with respect to each other so that the splice point lies in the flame. A technique for splicing together two optical fibers is further described, in which the optical fibers are first spliced together using a fusion splicer and then thermally treated by positioning the splice point in a flame while monitoring splice loss.

Systems and methods for low-loss splicing of optical fibers having a high concentration of fluorine to other types of optical fiber

An optical transmission line with reduced splice loss, and methods for fabricating an optical transmission line with reduced splice loss, are described. In one described method, a length of dispersion-compensating fiber, or other suitable first transmission fiber, is spliced to a first end of a length of a bridge fiber. The splice is heated to a maximum temperature to cause a measurable reduction in splice loss. The temperature of the splice is then ramped down to room temperature, such that the reduction in splice loss is maintained. A second end of the bridge fiber is then spliced to a length of a second transmission fiber. Further described is a technique for determining the maximum temperature for heating the splice between the first transmission fiber and the bridge fiber.

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Roskilde, Denmark

Torben Erik Veng