Alcatel-Lucent and BT said speeds of 1.4 terabits per second were achieved during their joint test - enough to send 44 uncompressed HD films a second.
The test was conducted on a 410km (255-mile) link between the BT Tower in central London and Ipswich.
However, it may be many years before consumers notice any effect.
But the breakthrough is being seen as highly important for internet service providers (ISPs), as it means a greater amount of information can be sent through existing broadband infrastructure, reducing the need for costly upgrades.
"BT and Alcatel-Lucent are making more from what they've got," explained Oliver Johnson, chief executive of broadband analyst firm Point Topic.
"It allows them to increase their capacity without having to spend much more money."
Alcatel-Lucent told the BBC that the demand for higher bandwidth grew by around 35% every year, making the need for more efficient ways to transfer data a massively pressing issue for ISPs, particularly with the growing popularity of data-heavy online services, such as film-streaming website Netflix.
There are faster methods of transmitting data -such as the use of complex laser technology - but this is the first test to achieve such high speeds in "real world" conditions, outside testing labs.
Rush-hour traffic
The high speeds were achieved using existing fibre cable technology that has already been installed in much of the UK and other parts of the world.
Kevin Drury, optical marketing leader at Alcatel-Lucent, likened the development to reducing space between lanes on a busy motorway, enabling more lanes of traffic to flow through the same area.
He said flexibility meant some could be adapted to specific needs - like opening an extra lane during the morning rush hour.
In internet terms, this would mean, for example, streaming video would get a large, wide lane, while accessing standard web pages would need only a small part of the fibre's capacity.
However, pushing more data through fibre cables presents a challenge.
"The trade-off is, the more you squeeze into a fibre line, the more potential there is for interference and for error," explained Mr Johnson.
"What has got better is the fact they are able to pack these channels closer together and into the same space."
Alcatel-Lucent and BT said their test demonstrated "stable, error-free operation".
Source: BBC News
