Researchers in the Optical Networks Group at University College London announced the breakthrough this week. The team is investigating the capacity limits of current optical transmission systems such as the fibre optic cables used to connect homes to broadband Internet.
Techniques derived from information theory and digital signal processing were combined to build a specialist optical network sending signals from multiple transmitters to a single receiver. The setup created a new world record for the fastest data transfer rate ever observed for digital information, an ultra-quick 1.125Tb/s.
Dr Robert Maher of UCL Electronic & Electrical Engineering and lead researcher on the project said: “While current state-of-the-art commercial optical transmission systems are capable of receiving single channel data rates of up to 100 gigabits per second (Gb/s), we are working with sophisticated equipment in our lab to design the next generation core networking and communications systems that can handle data signals at rates in excess of 1 terabit per second (Tb/s).”
Current broadband networks tend to operate at sub-100Mb/s speeds. The average UK connection is only 24Mb/s, a standard defined as “superfast” by the government. The system developed at UCL is therefore almost 50,000 times quicker as 1.125Tb/s equals 1,125,000Mb/s.
Maher explained: “For comparison this is almost 50,000 times greater than the average speed of a UK broadband connection of 24 megabits per second (Mb/s), which is the current speed defining “superfast” broadband. To give an example, the data rate we have achieved would allow the entire HD Games of Thrones series to be downloaded within one second.”
The system works by using a very high bandwidth receiver to process several lower speed channels at one time. By using 15 optical transmitters and a single large receiver, the team could increase the data transfer rate by processing more data at once. The technology also results in a more accurate transfer as the data from each transmitter can be verified against the others. If one of the 15 streams is found to differ from the others it can be corrected more quickly, leading to less packet loss in the cable.
“This is beneficial in a number of different ways: If you grab a lot of little channels in one go, you can use common information across all these to make up for various transmission impairments that arise from lasers, or from the optical fibre itself,” said Maher.
The approach also introduces unique challenges though. The receiver leads to variations in the performance of each optical sub-channel from the transmitters. The team had to optimise the modulation and code rate for each channel individually to correct this characteristic. It succeeded in its efforts though, “achieving the greatest information rate ever recorded using a single receiver.”
There is still a lot of work to do before this technology is deployed in datacentres and broadband networks around the world. The team has only tested it in laboratory conditions and now needs to scale it up for in use in longer stretches of cable using thousands of kilometres of optical fibre.
1 terabit speeds may still be several years in the future but they are likely to become as widespread as megabit connections over time. As more devices are brought online, whether they be smartphones, computers or intelligent “things”, new network infrastructures will need to be developed to support them all simultaneously, making this breakthrough in optical technology an important milestone for the Internet.
