History | The History of Submarine Cables

Submarine Cable History

Submarine Cable System History
150 Year History of Submarine Cables
Copyright © 2012 Bill Burns - All rights reserved

Laying and maintaining long undersea cables has now been a routine operation for almost 150 years, but when New York businessman Cyrus Field proposed an Atlantic cable in 1854, it was only four years since the first-ever cable had been laid between England and France, a mere 20 miles. The quality of the materials used to make the first cables was inconsistent, their theory of operation was unwritten, and the transmitting and receiving instruments were primitive.

Yet only a few years after that first cable, financiers and engineers were plotting a route across the Atlantic from Ireland to Newfoundland, a run one hundred times longer than that first cable to Europe. Just four years later, in 1858, the project achieved its first success, and in 2008 we celebrated the 150th anniversary of the first Atlantic cable.

"Atlantic Telegraph Cable Map"

With the limited technology of the time, how did the early cable engineers determine the best route, design their very long cable (the first of its kind), and get it safely to the sea bed? And in the 150 years from those first attempts to today’s routine cable laying expeditions, what has changed and what has stayed the same?

It’s generally accepted that the possibility of an Atlantic telegraph cable was first raised in 1843, when Samuel Morse, in a totally unwarranted yet eventually accurate fit of optimism, wrote "... a telegraphic communication on the electromagnetic plan may with certainty be established across the Atlantic Ocean! Startling as this may now seem, I am confident the time will come when this project will be realized."

Perhaps it was just that the time was right, but the beginnings of the submarine cable industry came about in the late 1840s from a series of unrelated events. Copper wire to conduct the signals was readily available, although of uncertain quality. For underwater use an insulator was needed, and gutta percha, the rubber-like sap of a tree found only in the British Empire and introduced to Britain a few years earlier, was the perfect material. The method of armoring the cable to give it strength during laying and protection afterwards was adapted from the recently introduced iron wire ropes developed to work the hoisting machinery in Germany’s deep mines. And in 1849, American naval vessels began systematic deep-sea soundings in the Atlantic. Based on their findings hydrographer Mathew Fontaine Maury, Superintendent of the Naval Observatory, suggested that there was an undersea plateau between Newfoundland and Ireland which would be the ideal route for laying a telegraph cable.

Custom-built cable ships have been used since 1874, when the Faraday was launched by Siemens Brothers. These highly specialized vessels are instantly recognizable by the cable sheaves at the bow and/or stern, over which the cable descends to the depths, and the elaborate machinery used to control the paying out of the cable. Before that, standard merchant ships were adapted for cable use, the very first cable ship being a small paddle steamer named Goliath, which with a drum of cable mounted on deck laid the cross-Channel cable of 1850. At the other end of the spectrum, the Great Eastern, the largest ship ever built at the time, was used for the Atlantic cables of 1865 and future years.

"Goliath laying the 1850 Channel submarine cable"

For the first Atlantic cable expeditions of 1857 and 1858 the British government lent HMS Agamemnon and the US government provided its new warship USS Niagara. These were fitted with cable gear designed largely by trial and error, from which has evolved the paying out gear used today. The experience gained in laying cables on the three Atlantic expeditions of 1857/58 was used to good effect in adapting the Great Eastern for its cable voyages in the 1860s and beyond.

The cable expeditions of the 1850s were dogged by repeated failures, particularly in the attempts to lay long cables such as the Atlantic run, but each time more money was raised and new expeditions mounted. The 1858 Atlantic cable, successfully laid on its third attempt, worked for only a few weeks, and there was another expensive failure on a different route the next year. Part of the problem was that insufficient attention had been paid to the design and manufacturing of long cables, and their operation was not based on any sound theory.

"Agamemnon laying the 1858 Atlantic submarine cable"

Despite its early failure, the 1858 Atlantic cable was a significant milestone. It showed that a long cable could be successfully laid and operated, and proved it could be financially viable. Even with the cable’s very slow transmission speed of just a few words per hour at best, messages sent by the British Government to its commanders in Canada countermanding orders for regiments to return to England saved the Government over £50,000, and the commercial possibilities of instant messages between New York and London were obvious to every international trader.

The publication in 1861 of the report of a government enquiry into the failure of the 1858 cable marked a turning point, and led to the beginnings of the modern cable industry. The importance was realized of using high quality materials and carefully controlled manufacturing and storage of the cable, the theory of signal transmission on long cables was worked out, and instruments and techniques for efficiently sending messages were devised.

Further work on the Atlantic cable was hindered by the Civil War in America, but in 1865 the Great Eastern was converted for cable laying, a new cable designed and manufactured on more rigorous principles was ordered, and the adventure was resumed. Despite a setback that year when the cable broke just 600 miles from Newfoundland and was lost in 12,000 feet of water, it was obvious that complete success was in reach. A second Great Eastern expedition in 1866 not only laid the cable without incident from Ireland to Newfoundland, but recovered and completed the lost cable of the previous year, providing two circuits for messages between Europe and America.

"Great Eastern laying the 1866 Atlantic submarine cable"

The early commercial promise was amply fulfilled by these cables. Transmitted at six to eight words per minute, messages were charged at $5 a word – in 1866 dollars! Despite the great cost of laying a long cable – over a million dollars at the time – the high return on investment led to a boom in cable laying worldwide. Other Atlantic cables followed, as did cables linking many parts of the world, and by the end of the century there were ten Atlantic cables, with two more in course of construction, and thirty-six cable ships employed in laying new lines and repairing the 130,000 miles of cable already at the bottom of the sea.

"Submarine Cable Map"

The engineers had not been idle during this time. One of their main concerns was the speedy and efficient transmission of signals over the cable, as this was directly related to revenue. There were continual improvements in the mechanical and electrical design of the cables, and automated transmitting and receiving equipment replaced manual operation. Multiplexing allowed a cable to carry more than one message at the same time, and complex electro-mechanical relays permitted signals to be forwarded directly from the undersea cable to the connecting landlines without re-keying. Messages could now be sent at 40 words per minute, and despite a significant reduction in the charges caused mainly by competition, the cable industry continued to be very profitable.

The repair of deep sea cables had also by now become routine. Before laying a cable on a new route, an accurate survey was made to establish the bottom conditions and find a safe path for the cable, and careful records were kept as the cable was laid. Precision measuring equipment allowed engineers to locate the position of a break from their test stations on shore, and a damaged cable could then be recovered and repaired. As we learned from the cable breakages in the Mediterranean a few years ago, little has changed in this area – damaged cables are still hauled up from the depths, breaks repaired on board the cable ship, and the cable sent back into the ocean. Perhaps the main difference is that the route surveys and positioning of repair ships are now done with the aid of satellite navigation systems.

By the 1920s cable had to meet the challenge of radio. Some felt that cables were now obsolete, but the lack of security on wireless transmissions left many customers uneasy, and cables continued to prosper. With further technical advances in the design of the cables and equipment, speeds reached 400 words per minute across the Atlantic by 1928. But this was still just for telegraph messages.

Although telephone conversations had been transmitted on short underwater cables as early as 1891, even the advances of the 20th century could not conquer the problem of carrying voices under the Atlantic and the other great oceans. Unlike on land lines, the signal level of voice transmissions on an undersea cable falls off very quickly, and without amplification nothing is received at the other end. It was not until the early 1950s that amplifiers capable of being spliced into the cable and paid out from a cable ship could be made reliable enough to justify the vast expense of using them every 20 miles along a 2000 mile Atlantic cable.

The first transatlantic telephone cable, TAT-1, went into service in 1956 – actually two cables, one to carry the eastbound traffic, the other the westbound. This cable carried 36 telephone channels, each of which was the equivalent of 22 telegraph circuits. A call cost £3 for three minutes, about $3 a minute at the time, which would be over $20 a minute in today’s dollars.

Again, once this breakthrough had been made, progress was rapid. Further Atlantic telephone cables followed at short intervals, together with others all round the world. Just ten years later, TAT-6 had 4000 telephone channels.

Another challenge to the supremacy of cables as the long distance message medium came with the advent of communications satellites, which initially took away a considerable amount of traffic. The main disadvantage of satellites, then and now, is the time delay in round-trip transmission. This is a source of discomfort when used for voice, as it disrupts the verbal cues that we all use on the phone to know when to stop and start talking, and also introduces large delays into the transmission of data – a signal across the Atlantic takes about eight times as long to arrive when sent by satellite.

Fortunately, fiber optic cable came to the rescue, and here we enter the present era of cable communications. 1988 saw the introduction of TAT-8, the first fiber optic cable across the Atlantic. This provided 40,000 telephone channels, and cable capacity has increased many fold since then, to the point where there is for all practical purposes unlimited bandwith to almost every part of the world at a very low cost.

Despite all the changes, many things have stayed the same in 150 years. Cables still have a conductor to carry the signal (glass instead of copper), an insulator to protect the circuits against water (polyethylene instead of gutta percha), and a strength member (steel instead of iron). Cable routes are surveyed with the aid of satellite navigation instead of celestial navigation, but cables are still laid by dropping them off a ship while steaming ahead, using a cable engine to regulate the paying out speed. Repairs are made as they always have been, by hauling the cable up from the depths and splicing as needed.

"Submarine Cable Images"

As for the future, I believe cable will always be the backbone of the global network. Land-based fiber optic technology will continue to expand high-speed delivery of data, audio, and video direct to the end user, and wireless will let us connect to the Internet and make phone calls wherever we go, but submarine cables will carry all this traffic around the world.

The early cable engineers would no doubt be impressed by our modern technology, but I’m sure they would also be amazed to see how much of what they pioneered remains the same today.

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