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What’s changed in subsea cable communications after 130 years?

What’s changed in subsea cable communications after 130 years?

On a cold winter morning, I was walking on the beach in Eastham (Cape Cod), Massachusetts and noticed something sticking out of a sand dune. Taking a closer look, I thought it could be a water pipe uncovered by recent storms. But then it occurred to me that I was standing near the point where an old submarine telegraph cable between France and the United States made landfall.

This stretch of beach is constantly changing, with sand washing out sections of dunes as winter storms pound the fragile coastline. Lighthouses, buildings, parking lots—anything manmade—have all fallen to the Atlantic’s battering. Yet this cable was prominently obvious, and it looked old but in remarkably good condition.


Segment of 1891 cable at Eastham, Mass.The French cable

Certainly, this was part of the French Cable. The French transatlantic telegraph cable was built in 1879, stretching from Brest, France to North Eastham, Massachusetts (US). Around 1891, the US landing site was moved to a more accessible location, several miles away in Orleans, requiring a connecting cable directly over where I stood in Eastham. This cable was in service until 1959, operated by La Compagnie Française du Télégraphe (referred to locally as The French Cable Company), offering telegraph services spanning 5,878 km (3,174 nautical miles). 

By today’s standards, the French cable provided impossibly low capacity. But consider that in 1891, we had no internet, smart phones, voice phones, TV or even radio. Wireless radio transmission was just an idea in the minds of Tesla and Marconi.

1891 cable on display at French Cable Station MuseumPrior to subsea cables, information traveled by written letters, carried on a ship. Telegraph cables meant news could be relayed in minutes instead of weeks. This had profound economic effect on government, business and individual lives. By 1890, telegraph cable transmission speeds had evolved greatly compared to earlier cables. But it would take a long time to reach speeds approaching just 100 words per minute.

Fast forward to fiber optics

Skipping ahead to 2022, we no longer use electrical impulses to span the world’s oceans. Long ago we adapted much of that early ocean engineering to laying cables with optical fibers at the core, using light to vastly increase capacity. We’ve also consumed capacity with powerful computer and communication systems and data centers spread to all corners of the world. 

In addition to the challenges of installing and operating a modern subsea cable, operators face the need to meet capacity demand and optimize economics—in many ways, just like the French Cable Company. 

What’s changed after 130 years?

Modern subsea cable in manufacturingVast increases in capacity and reach mean that we routinely build subsea cable systems that operate at 400 Gbps per wavelength and higher over transpacific spans. We can optimize fiber utilization through modulation techniques that optimize capacity for any particular optical span characteristics. We can better integrate submarine cables with terrestrial networks, making communication more reliable and flexible. And we also can use spatial division multiplexing (SDM) to further reduce transmission cost per bit.

The cables may look similar at first glance—but the capabilities they deliver today are hard to grasp.

Learn more!

On May 26, 2022 Olivier Courtois from Nokia-ASN will lead a Lightwave webinar presentation on these recent advances in subsea cable and submarine line termination equipment (SLTE) design. Specifically, Olivier will discuss how SDM can push the limits of theoretical design capacity by minimizing fiber nonlinear effects, how fine-tuning transmission baud rate offers substantial improvements in spectral efficiency, and how coherent optical digital signal processing enhances SLTE capabilities.

Chris Janson

About Chris Janson

Chris Janson follows trends in optical networking technology and its application to enterprise and other network operators. He has long contributed to the communications equipment and semiconductor fields through engineering and marketing roles. Chris enjoys giving back to the community through teaching engineering courses and serving on volunteer boards. In between that, he can be found running, riding bikes or windsurfing on Cape Cod or Maui.

Tweet me at @cj01950

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