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==History== |
==History== |
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After [[William Cooke]] and [[Charles Wheatstone]] had introduced their working [[telegraph]] in [[1839]], the idea of a submarine line across the [[Atlantic Ocean]] began to be thought of as a possible triumph of the future. [[Samuel Morse]] proclaimed his faith in it as early as the year [[1840]], and in [[1842]] he submerged a wire, insulated with tarred [[hemp]] and [[india rubber]], in the water of [[New York harbour]], and telegraphed through it. The following autumn Wheatstone performed a similar experiment in [[Swansea]] Bay. A good insulator to cover the wire and prevent the electricity from leaking into the water was requisite for the success of a long submarine line. India rubber had been tried by Jacobi, the Russian electrician, as far back as [[1811]]. |
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The first submarine communications cable was a telegraph cable laid between England and France in August [[1850]] by the [[Anglo-French Telegraph Company]]. In [[1852]], a cable laid by the Submarine Telegraph Company linked London to Paris for the first time. |
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Luckily another gum which could be melted by heat, and readily applied to the wire, made its appearance. [[Gutta-percha]], the adhesive juice of the ''Isonandra Gutta'' tree, was introduced to Europe in [[1842]] by Dr. Montgomerie, a Scots surveyor in the service of the [[British East India Company]]. Twenty years before he had seen whips made of it in [[Singapore]], and believed that it would be useful in the fabrication of surgical apparatus. Faraday and Wheatstone soon discovered its merits as an insulator, and in [[1845]] the latter suggested that it should be employed to cover the wire which it was proposed to lay from [[Dover]] to [[Calais]]. It was tried on a wire laid across the [[Rhine]] between [[Deutz]] and [[Cologne]]. In [[1849]] [[C.V. Walker]], [[electrician]] to the [[South Eastern Railway Company]], submerged a wire coated with it, or, as it is technically called, a gutta-percha core, along the coast off Dover. |
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In August [[1850]], [[John Watkins Brett]]'s [[Anglo-French Telegraph Company laid the first line across the [[English Channel]]. It was simply a copper wire coated with gutta-percha, without any other protection. The experiment served to keep alive the concession, and the next year, on [[November 13]], [[1851]], a protected core or true cable was laid from a government hulk, the ''Blazer'', which was towed across the Channel. Next year [[Great Britain]] and [[Ireland]] were linked together. In [[1852]], a cable laid by the [[Submarine Telegraph Company]] linked [[London]] to [[Paris]] for the first time. In May, [[1853]], England was joined to [[The Netherlands]] by a cable across the [[North Sea]], from [[Orfordness]] to [[The Hague]]. It was laid by the ''Monarch'', a [[paddle steamer]] which had been fitted for the work. |
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The first [[transatlantic telegraph cable]] was laid in [[1858]] ([[Cyrus Field]]), but was in operation for only a month. Subsequent attempts in [[1865]] and [[1866]] were more successful. |
The first [[transatlantic telegraph cable]] was laid in [[1858]] ([[Cyrus Field]]), but was in operation for only a month. Subsequent attempts in [[1865]] and [[1866]] were more successful. |
Revision as of 16:41, 27 July 2005
A submarine communications cable is a cable laid beneath the sea to carry telecommunications between countries.
The first submarine communications cables carried telegraphy traffic. Subsequent generations of cables carried first telephony traffic, then data communications traffic. All modern cables use fiber optic technology to carry digital payloads, which are then used to carry telephone traffic as well as Internet and private data traffic.
As of 2002, submarine cables link all the world's continents except Antarctica.
It is designed to factor out general communications cable issues from transatlantic / telephone / telegraph special cases
History
After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as the year 1840, and in 1842 he submerged a wire, insulated with tarred hemp and india rubber, in the water of New York harbour, and telegraphed through it. The following autumn Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the electricity from leaking into the water was requisite for the success of a long submarine line. India rubber had been tried by Jacobi, the Russian electrician, as far back as 1811.
Luckily another gum which could be melted by heat, and readily applied to the wire, made its appearance. Gutta-percha, the adhesive juice of the Isonandra Gutta tree, was introduced to Europe in 1842 by Dr. Montgomerie, a Scots surveyor in the service of the British East India Company. Twenty years before he had seen whips made of it in Singapore, and believed that it would be useful in the fabrication of surgical apparatus. Faraday and Wheatstone soon discovered its merits as an insulator, and in 1845 the latter suggested that it should be employed to cover the wire which it was proposed to lay from Dover to Calais. It was tried on a wire laid across the Rhine between Deutz and Cologne. In 1849 C.V. Walker, electrician to the South Eastern Railway Company, submerged a wire coated with it, or, as it is technically called, a gutta-percha core, along the coast off Dover.
In August 1850, John Watkins Brett's [[Anglo-French Telegraph Company laid the first line across the English Channel. It was simply a copper wire coated with gutta-percha, without any other protection. The experiment served to keep alive the concession, and the next year, on November 13, 1851, a protected core or true cable was laid from a government hulk, the Blazer, which was towed across the Channel. Next year Great Britain and Ireland were linked together. In 1852, a cable laid by the Submarine Telegraph Company linked London to Paris for the first time. In May, 1853, England was joined to The Netherlands by a cable across the North Sea, from Orfordness to The Hague. It was laid by the Monarch, a paddle steamer which had been fitted for the work.
The first transatlantic telegraph cable was laid in 1858 (Cyrus Field), but was in operation for only a month. Subsequent attempts in 1865 and 1866 were more successful.
Transatlantic cables of the 19th century consisted of steel wire, wrapping india rubber, wrapping gutta-percha, which actually surrounded the multi-strand copper wire. The portions for a distance from each shore had additional protective armor wires. Gutta-percha, a natural polymer similar to rubber, had nearly ideal properties for insulating submarine cables, aside from a rather high dielectric constant which made cable capacitance high. Gutta-percha was not replaced as a cable insulation until polyethylene was introduced in the 1930s. Gutta-percha was so critical to communications that in the 1920s the American military experimented with rubber-insulated cables, since American insterests controlled significant supplies of rubber but no gutta-percha manufacturers.
Long-haul submarine telegraph cables had tremendous electrical problems. Unlike modern submarine cables, the technology of the 19th century did not allow for in-line repeater amplifiers in the cable. The cables used huge voltages to overcome the resistance of their tremendous length. They also have extreme amounts of capacitance and inductive reactance. The distributed resistance, capacitance and inductive reactance operate in combination to slow down and disperse the telegraph pulses in the line, distorting them and limiting the speed of telegraph operation.
As early as 1823, Francis Ronalds had observed that electric signals were retarded in passing through an insulated wire or core laid under ground, and the same effect was noticeable on cores immersed in water, and particularly on the lengthy cable between England and The Hague. Michael Faraday showed that the effect was caused by induction between the electricity in the wire and the earth or water surrounding it. A core, in fact, is an attenuated capacitor.
Early cable designs failed to correctly analyze these facts. Famously, there was a showdown between E.O.W. Whitehouse of the Atlantic Telegraph Company and William Thomson (Lord Kelvin). Whitehouse believed that with enough voltage, any cable could be driven. Because of the excessive voltages recommended by Whitehouse, Cyrus Field's first transatlantic cable never worked reliably, and eventually shorted to the ocean when Whitehouse increased the voltage beyond the cable design limit. William Thomson designed a complex electric field generator that minimized current by resonating the cable, and a sensitive light-beam galvanometer for detecting the faint telegraph signals. He became rich on the royalties of these and several related inventions. William Thomson was elevated to baron Lord Kelvin for his contributions in this area, chiefly an accurate mathematical model of the cable using Lagrange transforms, which permitted design of the equipment for accurate telegraphy. The effects of atmospheric electricity and the geomagnetic field on submarine cables also motivated many of the early polar expeditions.
Lord Kelvin had produced a mathematical analysis of propagation of electrical signals into telegraph cables based on their capacitance and resistance, but since long submarine cables operated at slow rates, he did not include the effects of inductance. By the 1890's, Oliver Heaviside had produced the modern general form of the telegrapher's equations which included the effects of inductance and which were essential to extending the theory of transmission lines to higher freqeuncies required for high-speed data and voice.
While laying a transatlantic telephone cable was seriously considered from the 1920s, a number of technological advances were required for cost-efficient telecommunications that did not arrive until the 1940s.
In 1942, Siemens Brothers, in conjunction with the British National Physical Laboratory, adapted submarine communications cable technology to create the world's first submarine oil pipeline in Operation Pluto.
TAT-1 (Transatlantic No. 1) was the first transatlantic telephone cable system. Between 1955 and 1956, cable was laid between Gallanach Bay, near Oban, Scotland and Clarenville, Newfoundland. It was inaugurated on September 25, 1956, initially carrying 36 telephone channels.
- British Pacific Cable: October 31, 1902
In the 1960s, transoceanic cables were waveguides transmitting frequency-multiplexed radio signals. The repeaters were the most reliable vacuum tube amplifers ever designed. A high voltage direct current wire powered the repeaters. Many of these cables still exist and are usable, but abandoned because their capacity is too small to make money. Some have been used as scientific instruments to measure earthquake waves and other geomagnetic events.
In the 1980s, optic fiber cables were developed. Modern optic fiber repeaters use a solid-state optical amplifier, usually an Erbium-doped fiber amplifier. A solid-state laser is powered by the voltage difference between the ocean and a wire carrying high voltage direct current. The solid-state laser excites a short length of doped fiber that itself acts as a laser amplifier. As the light passes through the fiber, it is amplified. This system also permits wave-division multiplexing, which dramatically increases the capacity of the fiber.
The optic fiber used in undersea cables is chosen for its exceptional clarity, permitting runs of more than 100 kilometres between repeaters to minimize the number of amplifiers and the distortion they cause.
The fibers are usually arranged in a self-healing ring to increase their redundancy.
The first transatlantic telephone cable to use optical fiber was TAT-8, which went into operation in 1988.
Technology of submarine communications cables
- electromagnetic issues
- mirror galvanometer
- coaxial cable
- frequency division multiplexing
- reliability
- repeaters
- power distribution for repeaters
- fiber optics
- optical amplifiers, Erbium-doped fiber amplifier
- self-healing ring
- SONET
- wavelength division multiplexing
to be written
Economics of submarine communications cables
- national telco partnerships
- opening to third parties
- indefeasible rights of use (IRUs)
- venture capital
- boom and bust
- FLAG, Project Oxygen
- exponential rise in capacity over time makes value of IRUs implode
to be written
Owners and operators of submarine communications cables
to be written
Owners and operators of cable-laying ships
- TYCO
- ASN Marine
- Elettra
- FT Marine
- Global Marine Systems Limited
- NTT World Engineering Marine Corporation (NTT-WEM)
- S. B. Submarine Systems
- YIT Primatel Ltd.
See also
- Communications satellite
- Internet
- transatlantic telegraph cable
- transatlantic telephone cable
- optical fiber
- Public switched telephone network
- John Griesemer, Signal and Noise: A Novel, (2003), Picador, New York, ISBN 0312300824
External links
- http://gallery.colofinder.net/cableships -- Photo gallery of cable laying ships and other equipment
- http://www.atlantic-cable.com/Article/WireRope/wirerope.htm
- http://www.iscpc.org/ - The International Cable Protection Committee -- includes a register of submarine cables worldwide (though not always updated as often as one might hope)
- Cableships of the World
- FLAG telecom network summary
- A short history of telegraphy
- An Oversimplified Overview of Undersea Cable Systems
- SAT3 WASC SAFE Undersea Cable