Chapter 2: Advanced Copper Pair Technology

Chapter 2: Advanced Copper Pair Technology

?The reports of my death are greatly exaggerated.?

?Mark Twain

2.1 Background

Most of the investment to date in access networks has been in the installed copper cabling used to provide PSTN service to homes and businesses across the world. Copper wires are twisted together to ensure that external electronic noise is picked up equally on both wires to form a longitudinal signal that can be removed by coupling to the wires with transformers. The pairs of wires are then spun into cables or into binder groups within cables to average out the effects of their physical position within the cables. Coaxial copper cables are used in some places because their external shielding improves their noise immunity, but they are larger and more expensive than copper pairs and so are mainly used in specialized applications, such as between multiplexers.

For a short time, aluminum wires were tried out instead of copper because an increase in the cost of copper was predicted. Aluminum wires need to be larger than their copper equivalent because of the higher electrical resistance of aluminum. In addition, aluminum is harder to work with because it is more difficult to solder. The predicted cost increase for copper did not materialize, so the use of aluminum was dropped due to the operational difficulties.

Paper insulation continued to be used on copper pairs even after the introduction of plastic insulation because the pressurization needed for paper insulation was still needed with the...

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Access Networks: Technology and V5 Interfacing

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Chapter 2: Advanced Copper Pair Technology

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