New technique doubles distance of error free data transmission over fibre optic cable
04 Feb 2015
A team of researchers has demonstrated a new way to process fibre optic signals that could double the distance at which data traveled error-free through transatlantic sub-marine cables, ANI reported.
The University College London research revealed that the new method had the potential to cut the costs of long-distance optical fibre communications as signals would not need to be electronically boosted on their journey, which was important when the cables were buried underground or at the bottom of the ocean.
Since the technique could correct the transmitted data if it was corrupted or distorted on the journey, it could also help to boost the useful capacity of fibres. This was done right the end of the link, at the receiver, without having to introduce new components within the link itself.
This kind of capacity increase was important as optical fibres carried 99 per cent of all data and demand was rising with increased use of the internet, which could not be matched by the fibres' current capacity, and changing the receivers was much cheaper and easier than re-laying cables.
To cope with the increased demand, more information was being sent using the existing fibre infrastructure with data signals created by different frequencies of light.
The large number of light signals being sent could interact with each other and distort, causing the data to be received with errors.
According to study author Dr Robert Maher (UCL Electronic & Electrical Engineering), by eliminating the interactions between the optical channels, the team was able to double the distance signals could be transmitted error-free, from 3190km to 5890km, which was the largest increase ever reported for this system architecture UCL News reported.
He added the challenge was to devise a technique to simultaneously capture a group of optical channels, known as a super-channel, with a single receiver. This made it possible to undo the distortion by sending the data channels back on a virtual digital journey at the same time.
The researchers used a '16QAM super-channel' comprising a set of frequencies which could be coded using amplitude, phase and frequency to create a high-capacity optical signal. The super-channel was then detected with the use of high-speed super-receiver and new signal processing techniques developed by the team allowed the reception of all the channels together and without error. The new method would be tested on denser super-channels commonly used in digital cable TV (64QAM), cable modems (256QAM) and Ethernet connections (1024QAM).
