Furukawa Electric North America, Inc.

Lucent Technology

Kenneth L Taylor

Peter A Weimann

Harold P Debban

Luis M Bocanegra

Jennifer R Meeks

Clyde Jefferson Lever, Jr

Robert J Brown

The specification describes an improved optical fiber cable wherein the cable cross section is round and contains a plurality of bundled optical fibers. The bundle may comprise randomly spaced fibers or fibers aligned in a ribbon configuration. The bundle is encased in a polymer encasement that couples mechanically to each optical fiber. Preferably, the fibers are spaced from the nearest neighbor to improve coupling. In some embodiments the encasement is relatively hard, and is deliberately made to adhere to the optical fiber bundle. Consequently the encasement medium functions as an effective stress translating medium that deliberately translates stresses on the cable to the optical fibers. The cable construction of the invention is essentially void free, and provides a dry cable with water blocking capability.

Optical fiber cables

The specification describes an improved optical fiber cable wherein the cable cross section is round and contains a plurality of bundled optical fibers. The bundle may comprise randomly arranged optical fibers or optical fibers aligned in a ribbon configuration. The bundle is encased in a polymer encasement that couples mechanically to the optical fibers. In some embodiments the encasement is relatively hard, and is deliberately made to adhere to the optical fiber bundle. Consequently the encasement medium functions as an effective stress translating medium that deliberately translates stresses on the cable to the optical fibers. The cable construction of the invention is essentially void free, and provides a dry cable with water blocking capability.

The specification describes an optical fiber drop cable with a flat configuration, corresponding to &ldquo;A-drop&rdquo; cable. The cable is dry, and has a conformal primary encasement that is coupled directly to the optical fiber(s). Coupling the optical fibers and the exterior surface of the cable provides unexpected benefits, reducing the tendency of the fiber cable to buckle or shrink-back, and reducing the susceptibility of the cable to fiber retraction. The drop cable comprises three in-line components encased in a conformal secondary encasement. The center component comprises the optical fiber(s) coupled to the primary encasement. Located on each side of the optical fiber system are strength members. In a preferred embodiment, dimensions of the three elements are chosen so that the diameter of the center component is less than the diameter of either strength member. This provides crush protection for the optical fiber system. In an alternative embodiment, the cable is round on the end portions, with the middle portion, the portion that contains the optical fiber(s), dished so that the hyphen between the end portions has concave sides.

The specification describes an improved optical fiber ribbon cable. The cable design addresses the problem of wrinkles in the cable coating that occur on the interior bend radius on moderate bending of the cable. The wrinkles are much smaller than the bend radius, and are, relatively speaking, microbends. These may cause microbending losses in the fibers even where the bend radius is relatively large. The cable design of the invention has a combination of three important features. The cable cross section is round. The encasement for the optical fiber stack is relatively hard, and is deliberately made to adhere to the optical fiber stack. Consequently the encasement medium functions as an effective stress translating medium that deliberately translates stresses on the cable to the optical fibers. The optical fibers function as compressive strength members to retard longitudinal strain on the cables, and thereby reduce wrinkling of the encasement.

An optical fiber cable which is constructed so as to minimize optical transmission loss, and which comprises one or more compliant core units retained within a surrounding sheath. Each compliant core unit is composed of a bundle of parallel optical fibers, such as a stack of ribbons, enclosed in and supported by a compliant unitizing structure. The structure may derive its compliance from a foamed material, such as polyethylene, that is extruded to surround the fiber bundle. The foam material sufficiently cushions the bundle of fibers from external stresses that are applied when the cable is bent or encounters compressive loading.

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Lawrenceville, GA, United States of America

Kenneth L Taylor