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Nokia Bell Labs makes submarine cables go blinkin' fast

Finnish vendor Nokia has broken some submarine speed records using technology that doesn't require replacing the cables.

Nick Wood

October 10, 2023

3 Min Read
Fiber optics abstract background - Purple Blue Data Internet Technology Cable
Close up of fiber optic cables.

Finnish vendor Nokia has broken some submarine speed records using technology that doesn’t require replacing the cables.

Its Bell Labs unit, working out of its lab in Paris-Saclay, has developed a clever bit of kit that increases an optical network’s Baud (Bd) rate, which refers to the number of signalling events that are sent down the line every second. It differs slightly from bitrate, because with today’s modern networking gear, multiple bits can be transmitted during one signalling event – so one Bd per second normally equates to more than one bit per second.

When it comes to optical networking, the signalling event is the laser that switches on and off, sending data down the fibre. The faster the laser ‘blinks’, the higher the Bd rate.

That’s what Nokia Bell Labs has been working on, and this week it used it to set two new speed records.

The first one saw it reach 800 Gbps over a single optical wavelength at a distance of 7,865 km – roughly the distance between Tokyo and Seattle. According to Nokia, today’s technology can only achieve that throughput over half that distance.

Nokia said its breakthrough represents a tidy upgrade path for trans-Pacific and trans-Atlantic cable capacity that doesn’t require extra cable deployments.

The second speed record, set by Nokia Bell Labs in partnership with its Alcatel Submarine Networks (ASN) division, weighed in at 41 Tbps over 291 km, on a C-band unrepeated transmission system. These cables, Nokia explained, tend to be used to connect islands and offshore platforms back to the mainland. The previous record stood at 35 Tbps.

In both cases, Nokia was keen to emphasise the sustainability implications of higher Bd-rate technologies.

“These research advances show that that we can achieve better performance over the existing fibre infrastructure. Whether these optical systems are criss-crossing the world or linking the islands of an archipelago, we can extend their lifespans,” said Hans Bissessur, leader of ASN’s unrepeated systems group.

According to TeleGeography, there were an estimated 1.4 million km of submarine cables in service globally at the beginning of this year.

That number is going up, rapidly.

Recent highlights include Orange and ASN agreeing in July to construct the new Medusa cable system between multiple locations in North Africa and Southern Europe. In late September, Telecom Egypt agreed to extend Medusa all the way to the Red Sea.

On a slightly smaller scale, early last month, Telecom Italia Sparkle began offering commercial services on a stretch of the Blue cable system, linking Palermo with Genoa to Milan. It is part of the larger Blue and Raman system, being built in partnership with Google. Once completed, the Blue part will connect various locations on the Med – including Greece and Israel in addition to Italy – while the Raman part will connect Jordan, Saudi Arabia, Oman and eventually India.

These are just the developments in the last few months. With all that cable being laid and money being spent, there is a clear interest in getting the best out of it for as long as possible.

“With these higher baud rates, we can directly link most of the world’s continents with 800 Gbps of capacity over individual wavelengths. Previously, these distances were inconceivable for that capacity,” said Sylvain Almonacil, research engineer at Nokia Bell Labs. “Furthermore, we’re not resting on our achievement. This world record is the next step toward next-generation Terabit-per-second submarine transmissions over individual wavelengths.”


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About the Author(s)

Nick Wood

Nick is a freelancer who has covered the global telecoms industry for more than 15 years. Areas of expertise include operator strategies; M&As; and emerging technologies, among others. As a freelancer, Nick has contributed news and features for many well-known industry publications. Before that, he wrote daily news and regular features as deputy editor of Total Telecom. He has a first-class honours degree in journalism from the University of Westminster.

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