For indoor applications, the jacketed fiberis generally enclosed, with a bundle of flexible fibrous polymer strengthmembers like Kevlar aramid, in a lightweight plastic cover to form a simplecable. Each end of the cable may be terminated with a specialized optical fiberconnector to allow it to be easily connected and disconnected from transmittingand receiving equipment.
For use in more strenuous environments, amuch more robust cable construction is required. In loose-tube construction thefiber is laid helically into semi-rigid tubes, allowing the cable to stretchwithout stretching the fiber itself. This protects the fiber from tensionduring laying and due to temperature changes. Loose-tube fiber may be gel-filled.a loose tube, the fiber may be embedded in a heavy polymer jacket, commonlycalled "tight buffer" construction. Tight buffer cables are offeredfor a variety of applications, but the two most common are "Breakout"and "Distribution". Breakout cables normally contain a ripcord, twonon-conductive dielectric strengthening members (normally a glass rod epoxy),an aramid yarn, and 3 mm buffer tubing with an additional layer of Kevlarsurrounding each fiber. The ripcord is a parallel cord of strong yarn that issituated under the jacket of the cable for jacket removal. Distribution cableshave an overall Kevlar wrapping, a ripcord, and a 900 micrometer buffer coatingsurrounding each fiber. These fiber units are commonly bundled with additionalsteel strength members, again with a helical twist to allow for stretching.
A critical concern in outdoor cabling is toprotect the fiber from contamination by water. This is accomplished by use ofsolid barriers such as copper tubes, and water-repellent jelly orwater-absorbing powder surrounding the fiber.
Finally, the cable may be armored toprotect it from environmental hazards, such as construction work or gnawinganimals. Undersea cables are more heavily armored in their near-shore portionsto protect them from boat anchors, fishing gear, and even sharks, which may beattracted to the electrical power that is carried to power amplifiers orrepeaters in the cable.
Modern cables come in a wide variety ofsheathings and armor, designed for applications such as direct burial intrenches, dual use as power lines, installation in conduit, lashing to aerialtelephone poles, submarine installation, and insertion in paved streets.