“While current state-of-the-art commercial optical transmission systems are capable of receiving single channel data rates of up to 100Gbit/s, we are working in our lab to design the next generation core networking and communications systems that can handle data signals at rates in excess of 1Tbit/s,” said UCL researcher Dr Robert Maher.
The study, published in Scientific Reports, used techniques from information theory and digital signal processing to custom build an optical communications system with multiple transmitting channels and a single receiver.It is part of the EPSRC-funded UNLOC programme.
Working in UCL’s UNLOC lab, the researchers used fifteen wavelength channels, modulated using 256QAM, 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, according to UCL.
“Using high-bandwidth super-receivers enables us to receive an entire super-channel in one go,” said 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.”
256QAM, normally used in cable modems but not widely used in optical comms, said UCL, was chosen as the best way of encoding to take into account the limitations of the transmitter and receiver.
The transmitter was directly connected to the receiver for the record attempt. Researchers will now analyse achievable data rates in long fibres – up to transcontinental length.