Nokia Bell Labs Makes Submarine Cables Go Blinkin' Fast

Nokia Bell Labs achieves 800 Gbps speed over a single optical wavelength on a 7,865 km submarine cable, offering a sustainable upgrade path.By Nick Wood,
October 10, 2023

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.

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