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stranding

Stranding is the mutual, helical twisting of insulated cores, which is applied to symmetrical copper cables, stranded wire and optical fib ers. In symmetrical copper cores, the symmetry of the core pairs prevents interference signals from being picked up. Such a cable system is therefore largely insensitive to interference, since interspersed interference cancels each other out and the receiver only receives the interference signal difference of one pair of wires.

During stranding, the cores are stranded in concentric layers or bundles around a stranding axis. This is why we also speak of layer stranding (Lg) and bundle stranding( Bd). In layer stranding of telephone cables, one pair of wires is always twisted against each other; in bundle stranding, several wires are combined in bundles and twisted against each other. In the case of telecommunications cables, a bundle consists of four cores, with the two cores of a pair of cores arranged opposite each other.

Stranding of cores, photo: strasser-elektrotechnik.de

Stranding of cores, photo: strasser-elektrotechnik.de

The stranding of wire pairs significantly determines the frequency behavior and crosstalk. In order to keep the crosstalk between adjacent wire pairs as low as possible, these wire pairs are stranded with different lay lengths and lay directions. In order to produce cables with the widest possible frequency range, manufacturing requires minimal tolerances. Stranding also has the advantage that the cables are flexible.

Lay length of a bundle stranding

Lay length of a bundle stranding

In fiber optic cables, the cores are usually stranded in opposite directions around a support element. If the individual optical fib ers are arranged in several layers around the support element, this is referred to as layer stranding or an LwL layer cable. If, on the other hand, the cable core consists of a bundle of optical waveguides, it is referred to as an FO bundle cable.

In the case of LwL cables, the stranding ensures that the cable does not exhibit any internal stress during installation and that it rolls up again like a spiral in the normal state.

Informations:
Englisch: stranding
Updated at: 09.04.2017
#Words: 327
Links: copper (Cu), stranded wire, indium (In), interference (I), cable
Translations: DE
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