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All-dielectric self-supporting (ADSS) cable is a type of optical fiber cable that is strong enough to support itself between structures without using conductive metal elements. It is used by electrical utility companies as a communications medium, installed along existing overhead transmission lines and often sharing the same support structures as the electrical conductors.〔Richard C. Dorf (ed), ''Electronics, Power Electronics, Optoelectronics, Microwaves, Electromagnetics, and Radar'' CRC Press, 2006 ISBN 0849373395 page 21-27〕 ADSS is an alternative to OPGW and OPAC with lower installation cost. The cables are designed to be strong enough to allow lengths of up to 700 metres to be installed between support towers. ADSS cable is designed to be lightweight and small in diameter to reduce the load on tower structures due to cable weight, wind, and ice.〔G. F. Moore (ed.), ''Electric Cables Handbook Third Edition'', Blackwell Science, 1997 ISBN 0-632-04075-0 Chapter 51 All-dielectric Self-supporting Cables pp. 730-744〕 In the design of the cable, the internal glass optical fibers are supported with no strain, to maintain low optical loss throughout the life of the cable. The cable is jacketed to prevent moisture from degrading the fibers. The jacket also protects the polymer strength elements from the effect of solar ultraviolet light. Using single-mode fibers and light wavelengths of either 1310 or 1530 nanometres, circuits up to 100 km long are possible without repeaters. A single cable can carry as many as 144 fibers. ==Construction details== No metal wires are used in an ADSS cable. Optical fibers are either supported in loose buffer tubes, or arranged in a ribbon configuration. To prevent strain on the fibers, most types provide the fibres with excess slack length compared to the length of the supporting member.〔 Several designs of cable are used. In one type, small plastic tubes each containing up to eight fibers are filled with a gel compound, and stranded around plastic rods. The hydrocarbon gel compound prevents water from wicking along the length of the cable. The inner structure is wrapped with polyester tapes and encased in a pultruded glass reinforced plastic tube, which provides the structural strength for the cable. An outer sheath is applied to protect the strength member from ultraviolet light and from damage due to leakage current. Another type uses a glass reinforced plastic rod with a notch in one side, which carries one or two ribbons of glass fibers. The notch is filled with water-resistant gel and covered with an extruded plastic filler strip. The whole assembly is enclosed in a sunlight and tracking resistant sheath. This design is not as flexible as the symmetrical cylindrical design above, but provides good access to the fibers at joints and is resistant to crushing. At full working load the optical fibers may experience up to 0.25% strain, which is undesirable for long fiber life. A third type gets its strength from aramid fiber yarns, which are coated to prevent water wicking. The aramid yarn strength member surrounds a core made up of multiple buffer tubes, each with a fiber, all surrounding a plastic core. The outer sheath provides protection from water and sunlight. This design does not have as great resistance to crushing. Another type of design uses four glass-reinforced plastic strength member strands, and loose buffer tubes cabled into an assembly and protected by a jacket. This is more flexible than the outer cylinder type first described, but does not provide as much protection to the fibers. ADSS cables made by BICC with 24 or 48 fibers in the above designs range from 220 to 284 kg/kilometre in weight and are between 13 and 16 mm outside jacket diameter. These cables can support between 20 and 25 kilonewtons of tension. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「All-dielectric self-supporting cable」の詳細全文を読む スポンサード リンク
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