Current cabling will hold up high-speed internet

Remember the furore over plans to replace Australia’s aging copper-wire-based internet infrastructure with more copper wire? In 2013, the Liberal-National Coalition federal government of Tony Abbott announced that the country’s National Broadband Network (NBN) would see the installation of 55,911 kilometres of copper wire, thus abandoning plans to use more expensive, but more modern and higher bandwidth, fibre cables.

New UK-based research has shown why this was short-sighted. Engineers at the University of Cambridge and BT (formerly British Telecom) have found that, while current copper infrastructure may allow for some improvement in speed, there’s a limit.

The findings, published today in Nature Communications, look at the UK’s existing copper network cables. The wires currently in use are ‘twisted pair’ copper cables. The study found that the cables’ physical makeup and geometry limits their ability to support higher frequencies, which are needed to support greater data transfer rates.

Using a combination of computer modelling and experiments, the Cambridge-led team found the copper wires can carry a maximum frequency of about 5 GHz. The current spectrum used is lower than 1 GHz. The researchers found that, above 5 GHz, the twisted pair cables start to radiate and behave like an antenna.

The remaining wiggle room offered by copper wire does mean data rates can increase to above several Gigabits per second on short ranges. However, optical fibre cables have hundreds of thousands of times more bandwidth, and are able to carry at least hundreds of Terabits every second.

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Study co-author Dr Anas Al Rawi from Cambridge’s Cavendish Laboratory says: “Any investment in existing copper infrastructure would only be an interim solution.” Rawi added that the findings “show that eventual migration to optical fibre is inevitable”.

“High-speed internet is a necessity of 21st century life,” notes lead author Dr Ergin Dinc. “Internet service providers have been switching existing copper wires to high-speed fibre-optic cables, but it will take between 15 and 20 years for these to reach every house in the UK and will cost billions of pounds. While this change is happening, we’ve shown that existing copper infrastructure can support higher speeds as an intermediate solution.

“No one had really looked into the physical limitations driving the maximum internet speed for twisted pair cables before. If we used these cables in a different way, would it be possible to get them to carry data at higher speeds?”

But, as demand for and on high-speed internet are only increasing, copper cables cannot indefinitely supply the greater data rates required by modern life. “The way that the cables are twisted together defines how high a frequency they can carry,” says team leader Dr Eloy de Lera Acedo, also from the Cavendish Laboratory. “To enable higher data rates, we’d need the cables to carry a higher frequency, but this can’t happen indefinitely because of physical limitations. We can improve speeds a little bit, but not nearly enough to be future-proof.”

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