Twisted pair still has a copper-bottomed future

Feb 8, 2021

  • Old transmission medium remains relevant in the age of wireless and fibre
  • Cost effective, backwards compatible and can deliver power too
  • Remains a core transmission medium for data centres, domestic premises, enterprises and buildings
  • But will be gone from the PSTN within five years

In 1897, the American writer, Mark Twain, was in London when he was told that a US paper had published his obituary. In response he sent a telegram saying: "The reports of my death are greatly exaggerated." The same can be said of predictions of the demise of copper cabling. Its imminent death has been foretold for decades but it's still with us, still strong, secure and reliable. Despite the spread of fibre optics and the ubiquity of wireless communications, wireline is a venerable but still vital technology. 

Indeed, cell phone networks could not function without twisted-pair copper cables. The same is true of copper-wire-based data centre environments, in enterprise solutions, intelligent building systems, industrial networks and in domestic premises. The fact is that copper cables, fibre optics and wireless used together form systems and very fast network applications that are considerably bigger than are their individual parts.

In its latest edition, UK magazine Inside_Networks has a thought-provoking feature on the longevity and continued utility of copper cabling in even the most cutting edge comms systems and applications. The article points out that copper cable is a cost-effective solution under a wide variety of circumstances where high-bandwidth capabilities are required, is backward compatible and, a real bonus this, can transmit power to remote devices.

The ability of copper cable to deliver power to end devices is of great interest in providing services to multiple building systems because the cost-effective power/bandwidth combination is very attractive over existing infrastructure. Meanwhile, powered fibre cable, where optical fibres provide high-data-rate transmission over long distances and copper conductors enable power supply, are growing in popularity. With so many millions of buildings already literally embedded with copper wires, the old medium remains cheap and reliable, so why get rid of it and have to bear the cost of deploying a more expensive solution for what might be no more than a limited incremental benefit?

The Category 8 cabling specifications currently in use provides four times the bandwidth of its predecessor Category 6A and permits data transmission speeds of up to 40 Gb/s in cable runs of between five and 30 metres. Valerie Maguire, Distinguised Engineer at US data centre, LAN and Intelligent Buildings specialist, Siemon, points out that "the fastest speed supported by twisted-pair copper cabling over 100 metres is 10 Gb/s (10GBASE-T). Operation over this reach in addition to market availability and an installed base, will be key to successful adoption of new four-pair Ethernet technology."

She adds, "Looking to the future, higher transmission speeds can be supported over balanced twisted-pair cabling if more complex encoding, higher signalling rates and improved noise and echo cancellation and even different modulation schemes…. are employed. One thing's for sure, today's balanced twisted-pair shielded copper cabling systems have tremendous capacity and are here to stay whatever tomorrow brings."

In the same Inside_Networks piece, Piers Benjamin of Corning Optical Networks says, "Ultimately, while emerging smart connected building infrastructures will become more and more reliant on optical fibre there is still a place for copper. It remains a compelling medium for the last point-to-point connection to a device. However, limitations of copper solutions in terms of bandwidth, power handling and distance mean networks should be designed to push the fibre to copper transition point."

But in the PSTN, copper's time is almost up

Meanwhile, while the UK’s old copper-based network will be "switched-off" completely in 2025, a range of Wholesale Line Rental (WLR) voice and broadband products that rely and are supported by good old copper will be removed from the market within the next two years.

British regulator, Ofcom says the "retirement of copper services is an important part of the business case for the roll-out of fibre networks. Openreach, BT's semi-detached wholesale division, is upgrading its copper network to fibre on an exchange-by-exchange basis and, as each one is upgraded, Openreach will transition customers to the new network and then withdraw copper services.

That's why Ofcom's 2020 "Wholesale Fixed Telecoms Market Review" announced that, as part of the promotion of fibre investment over copper retirement proposals, it would refocus regulation away from the copper network and over to fibre. As part of the refocus Ofcom will permit Openreach to increase the price of copper services to to premises wherever and whenever fibre optic technology is available.

Recently, Openreach announced that ultrafast fibre-based services will be available to 75 per cent of premises sited within each exchange area from 168 BT exchanges (plus Salisbury, which has been the nerve centre for the testing tof he copper/fibre transition, if you'll forgive the bad taste Novichok pun) allowing the carrier to stop selling new copper services in those exchanges as early as this year.

In the Market Review, Ofcom did not propose removing the general and specific network access obligations on Openreach that apply to existing copper service because Openreach originally said the earliest it would withdraw legacy copper services would be April 2026. However as the roll-out of fibre has accelerated it is possible that the end of copper in the PSTN could come some time before that date.

So, although copper's days in the national network are numbered, it will remain a viable, comparatively inexpensive, tried and tested technology in data centres, with ISPs and wireless networks, in enterprises, intelligent buildings and domestic premises into the indefinite future. The's life in the copper yet and, after all. Mark Twain soldiered on for years after the premature publishing of his obituary.

And finally, talking of conductors, a joke. A superconductor walks into a bar. The landlord, who'd had previous trouble with him after a couple of Sidecars and a Whisky Sour or two, said, "I've told you before, we don't serve superconductors in here." The barkeep was expecting a comeback and perhaps even some violence but the superconductor simply turned on his heel and left without resistance. Thank you very much.

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