UK Scientists Squeeze 1.125Tbps Through a Single Fibre Optic Receiver

A team of researchers working out of the University College London have given fibre optic communications technology a further boost by achieving the highest data throughput ever reported (1.125 Terabits per second) for a single coherent optical receiver.

Some reports have perhaps characterised this record incorrectly and indeed we have seen significantly faster fibre optic networks before, such as the effort in 2014 by Dutch scientists to push an astonishing 255Tbps (Terabits per second) over a single 1km long link (here). But that required a completely new network and a 7 core fibre optic cable.

However the key piece of information in today’s news is that a new bit rate of 1.125Tbps was attained by using a single receiver, which in reality represents a modest increase of 12.5% relative to the previous record that achieved 1Tbps. The previous record harnessed a spectrally sliced transmitter and a digital coherent receiver with an optical bandwidth of 125GHz.

The latest achievement made use of a 15 sub-carrier 8 GBd DP-256QAM super-channel (15 channels of data) and the total bandwidth of this “super-channel” came out as 121.5GHz, which was within the 125GHz capability of their digital coherent receiver.

Dr Robert Maher, UCL Electronic & Electrical Engineering, 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).

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.

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.

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.”

Granted the improvement of 12.5% over the last record might not seem all that huge, although when multiplied via a bigger network it could become much more significant and even on a single receiver you’re still talking about pushing an extra 125Gbps (Gigabits per second), which is nothing to sniff about.

The team further claims that there is room for “significant future increases,” although this is reliant on the continual development of Digital-to-Analogue Converters (DAC), Analogue-to-Digital Converters (ADC) and implementable capacity-approaching FEC codes.

However it appears as if the performance achieved above was only shown when directly connecting the transmitter and receiver, which is good for a lab test but kind of ignores the need that most networks have for a long piece of fibre optic cable.

The next approach will thus be to test all of these improvements and measure the achievable data rates in a long distance transmission scenario, where optical signals can become distorted as they travel through thousands of kilometres of optical fibres (e.g. international sub-sea fibre optic links).