These fiber units are commonly bundled with additional steel strength members, again with a helical twist to allow for stretching.Ī critical concern in outdoor cabling is to protect the fiber from contamination by water. Distribution cables have an overall Kevlar wrapping, a ripcord, and a 900 micrometer buffer coating surrounding each fiber. The ripcord is a parallel cord of strong yarn that is situated under the jacket(s) of the cable for jacket removal. Breakout cables normally contain a ripcord, two non-conductive dielectric strengthening members (normally a glass rod epoxy), an aramid yarn, and 3 mm buffer tubing with an additional layer of Kevlar surrounding each fiber. Tight buffer cables are offered for a variety of applications, but the two most common are 'Breakout' and 'Distribution'. Instead of a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called 'tight buffer' construction. Dry block offers less protection to the fibers than gel-filled, but costs considerably less. Loose-tube fiber may be 'dry block' or gel-filled. This protects the fiber from tension during laying and due to temperature changes. In loose-tube construction the fiber is laid helically into semi-rigid tubes, allowing the cable to stretch without stretching the fiber itself. For use in more strenuous environments, a much more robust cable construction is required.
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