Broadband internet: copper telephone wire could be almost as fast as fiber
Many homes in the UK rely on repurposed phone lines to access the internet, which slows down download speeds, but there may be a solution
April 26, 2022
Fiber optic cable is being laid across the UK at great expense to speed up people’s internet connections, but researchers say the copper telephone wire already in use across the country can achieve data speeds three times higher than those currently seen at a fraction of the price, at least over short distances. Their technique for increasing speeds can help ease the transition to nationwide fiber optics, and can also be used in countries that use similar twisted-pair copper wire.
Ergin Dinc at the University of Cambridge and his colleagues say that twisted pairs of copper wire, the type used for decades as telephone lines and now being repurposed for broadband internet, can support five times the frequency of currently used, which would greatly improve data transmission rates. Beyond this limit, the researchers found that the wire essentially acted as an antenna and turned any signal sent along it into radio waves that dissipated before reaching their destination.
“These cables are actually very old, invented by Alexander Graham Bell, and since then nobody has looked at the theoretical limits,” says Dinc.
He and his colleagues say their findings could allow homes near fiber optic cables to achieve higher speeds than they currently enjoy without having to run fiber to their homes.
Fiber optic cables carry groups of photons to represent data, and large numbers of these groups can be sent down the line one after another without waiting for the first one to arrive. The fiber connections used today typically operate at 1 gigabit per second, but theoretical speeds could be several thousand times that.
But in copper cabling, the signal is sent by an electric current flowing the length of the cable, and the data transmission rate is limited by how quickly the current can be changed.
Existing copper broadband connections operate at a frequency below 1 gigahertz, where the current is changed a billion times per second, but researchers have found that this can theoretically be boosted to 5 gigahertz using a small, inexpensive component called balun.
Dinc doesn’t believe this will translate directly to a five-fold increase in data transmission, as the error rate increases at higher frequencies. More research is needed to determine how much of a boost is actually possible, but Dinc believes 3 gigabits per second is achievable. This is triple the current theoretical maximum, although in practice most people with copper wire broadband in the UK only reach maximum speeds of 80 megabits per second.
Journal reference: Nature Communication, DOI: 10.1038/s41467-022-29631-8
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