| abstract |
An optical fiber cable comprises one or more "units" surrounded by a sheath. Each unit comprises a dielectric central strength member, a smooth cushion layer thereon, and one or more optical fibers helically wrapped thereon. A tube surrounds this structure, with the space therebetween optionally filled with a waterproofing gel that has a low modulus over a wide temperature range. The tube is made of a material (typically PVC) that obtains a low modulus during cooling after extrusion so that substantially no compressive stresses are transmitted to the optical fibers. In an alternate embodiment, the optical fibers do no lay directly on the cushion layer but "float" in the waterproofing gel. In another embodiment, a spacer fiber of larger diameter than the optical fibers provides for clearance between the tube and the optical fibers. The resulting structure provides for ease of manufacture and low microbending losses for the optical fibers over a wide temperature range. |