transatlantic cable

3 Articles

TAT-8 — The First Transatlantic Fiber — Rises Again

February 24, 2026 by 25 Comments

While you may have never heard of TAT-8, there is a good chance you sent some data through it. TAT-8 was the 8th transatlantic communications cable and the first transatlantic fiber-optic cable, carrying 560 Mbit/s on two fibers between Tuckerton, New Jersey, and, thanks to an underwater splitting device, Widemouth Bay, England, and Penmarch, France. Construction of the cable began in 1998. Later that year, the first call, made by [Issac Asimov] took place. The cable was retired in 2002. Now, Subsea Environmental Services is recovering the cable for recycling.

The 6,000 km cable was built by a consortium of companies including AT&T, France Télécom, and British Telecom. The 1.3 micron fiber used special optical repeaters about 40 km apart and cost about $335 million (just shy of a billion dollars today). Designers were optimistic, with some claiming the cable would end the need for future cables or, at least, that the cable would not reach capacity for ten years or more. In reality, the cable was saturated within 18 months. Turns out, the equivalent of 40,000 phone lines wasn’t enough.

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Under The Sea: Optical Repeaters For Submarine Cables

August 8, 2023 by 25 Comments

Once a month or so, I have the privilege of sitting down with Editor-in-Chief Elliot Williams to record the Hackaday Podcast. It’s a lot of fun spending a couple of hours geeking out together, and we invariably go off on ridiculous tangents with no chance of making the final cut, except perhaps as fodder for the intro and outro. It’s a lot of work, especially for Elliot, who has to edit the raw recordings, but it’s also a lot of fun.

Of course, we do the whole thing virtually, and we have a little ritual that we do at the start: the clapping. We take turns clapping our hands into our microphones three times, with the person on the other end of the line doing a clap of his own synchronized with the final clap. That gives Elliot an idea of how much lag there is on the line, which allows him to synchronize the two recordings. With him being in Germany and me in Idaho, the lag is pretty noticeable, at least a second or two.

Every time we perform this ritual, I can’t help but wonder about all the gear that makes it possible, including the fiber optic cables running beneath the Atlantic Ocean. Undersea communications cable stitch the world together, carrying more than 99% of transcontinental internet traffic. They’re full of fascinating engineering, but for my money, the inline optical repeaters that boost the signals along the way are the most interesting bits, even though — or perhaps especially because — they’re hidden away at the bottom of the sea.

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Loading Coils, The Heaviside Condition, And Pupin Coils

June 19, 2020 by 27 Comments

When we draw schematics, we have the luxury of pretending that wire is free. There are only a few cases where you have to account for the electrical characteristics of wire: when the wire is very long or the frequency on the wire is relatively high.

This became apparent after the first transatlantic cable went into service for telegraph communications. Even though the wire was linear, there was still distortion on the line so severe that dots and dashes would overlap each other. The temporary solution was to limit speeds so slow that operators had trouble sending and receiving at those speeds. How slow? An average character took two minutes to send! That’s not a typo. Two minutes per character. By custom, Morse code assumes a word is five characters, so you could send a word every 10 minutes.

The first transatlantic cable went into service in 1858 and was virtually the moon landing of its day. Frustrated with how slow the communications were, an electrician by the name of Whitehouse decided to crank up the voltage to over 1,000 volts which caused the cable to fail after only three weeks in service. Whoops. Later analysis showed the cable was probably going to fail quickly anyway, but Whitehouse took the public blame.

The wire back then wasn’t as good as what we have today, which led to some of the problems. The insulation was made from multiple coats of a natural latex, gutta percha, which is what dentists use to fill root canals. The jackets were made from tarred hemp and bound with iron wire. There was no way to build an underwater amplifier in 1858, so the cables were just tremendous wires laying on the ocean floor between Newfoundland and Ireland.

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