Researchers from University College London's (UCL) Optical Networks Group have demonstrated a 1.125 Tb/s data transmission rate as part of their investigation into the capacity limits of optical transmission systems.
The academics had reportedly used "techniques from information theory and digital signal processing" to create for themselves a comms system with multiple transmitting channels and a single receiver.
The project was part of the EPSRC-funded UNLOC programme, and investigated ways to "improve the optical network infrastructure to support the explosion of digital content, cloud and e-health services, as well as the ubiquitous connectivity of smart devices referred to as the Internet of Things (IoT)."
The lead researcher and first author, Dr Robert Maher, 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).”
Dr Maher continued: “For comparison, this is almost 50,000 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.”
Assessing the limitations of the transmitter and receiver, the boffins determined the best techniques of encoding information for their transmission system were those most commonly used in wireless communications, to ensure the transmitted signals are adapted to distortions in the system electronics.
Using UNLOC’s state-of-the-art lab facilities, the researchers built the new optical system and measured its performance. Fifteen channels, each carrying an optical signal of different wavelength were modulated using the 256QAM format typically used in cable modems, combined and sent to a single optical receiver for detection. By grouping the channels together, the team created a ‘super-channel’ which although not yet commercially available, is widely believed to be a way forward for the next generation of high-capacity communication systems.
“Using high-bandwidth super-receivers enables us to receive an entire super-channel in one go. Super-channels are becoming increasingly important for core optical communications systems, which transfer bulk data flows between large cities, countries or even continents,” said Dr Maher.
“However, using a single receiver varies the levels of performance of each optical sub-channel so we had to finely optimise both the modulation format and code rate for each optical channel individually to maximise the net information data rate. This ultimately resulted in us achieving the greatest information rate ever recorded using a single receiver,” added the boffin.
While this time around the electrical engineers had connected the transmitter directly to the receiver to achieve their record data rate, the next step is to see how the rates hold up and avoid distortion when beamed through thousands of kilometres in fibre. ®