Ocean Submarine Communication CablesHaving discovered the telegraph people started covering vast areas with telegraph lines. Initially the lines connected big cities and countries. Soon communication was established between all major areas within the continents. The same was with telephone communication. But what about communication between the continents? At that time it was possible only by post. Such communication was limited in speed and was conditioned by velocity of vessels sailing, for example, between North America and Europe. And air communication had not been established yet. Long-wave communication was not reliable. There was only one way out - to lay the cable across the ocean bed despite all difficulties and expenses.The first successful experience was laying of a 45-km long cable across Pas de Calais strait in 1850. Its design was later used while making many other submarine cables. So what are these cables?This is a coaxial cable with a continuous insulation, usually made of polyethylene. There are two types of submarine cables - shallow-water cables (up to 700 m) and deep-water cables.They have almost the same design. There are inner and outer copper conductors. The outer conductor has a diameter from several millimeters to several dozen millimeters. The diameter also depends on the number of communication channels.So what are their main differences? A deep-water cable has a steel-wire guiding cable messenger in the middle. This facilitates the cable's laying and prevents twisting. A shallow-water cable does not have such core. It has the inner conductor in the middle. Just like in the first case, it is insulated from the outer conductor by a polyethylene layer. The most important thing is that such cable is additionally protected by a steel-wire armor. You may ask why a shallow-water cable has such armor. Well, it protects the cable against possible physical effects of ship navigation such as contacts with trawls and anchors as well as against rubbing against the ground.Such cable may have a diameter of up to 48 mm and can weigh about 3 tons per kilometer. A deep-water cable is about 1.5 times thinner and lighter.The first transatlantic cable was laid at the third attempt between Ireland and Canadian Newfoundland. This happened in 1858. It was 3750 km long. The first telegraph messages were transmitted but the communication did not last long. Very soon the cable communication failed because of insulation fault. About 400 messages had been transmitted before the failure. The second cable was laid in 1865. But there was cable breakdown and the work came to nothing. But eventually the following year everything went fine and communication was established. Later the second previously broken cable was found and laid to Canada too. By the end of the 19th century already 15 cable junctions were laid.The first telephone cable ТАТ1 was laid in 1956. It had 36 communication channels. Later the number of connections and channels grew. For example, by the 90s ТАТ7 line was laid across the Atlantic. It provided a 40 000 channel communication.In the middle of the 20th century the cables were laid across the Pacific Ocean - between Australia and America. It is about 15 000 km long. There is also a worldwide cable route which is 50 000 km long.The cables are laid across the ocean bed at the depths of up to 7.5 km. Amplifiers may be installed along the line.Special cable layer vessels are used for laying the cable. These are quite big ships. The laying goes at the speed of 15 km/h. The continents can be connected in about 2 weeks' time.Nowadays, for transmitting data, telegraph and telephone lines are replaced by fiber-optic lines. They are also used for data exchange in the Internet. In general, such cable has a similar design. However, it has optical fiber inside instead of a copper conductor. For example, recently the Unity optical cable has been laid under the aegis of Google between Japan and the U.S. It is 10 000 km long. Its overall transmission capacity is 4.8 terabits per second. This type of communication will stay for a long time as so far despite the satellite communication only optical fiber can satisfy data communication demand.
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How do they do it - Undersea Fibre Optic Cables Internet Telecomsby ironheadtg201027,334 views
interesting
place910 1 year ago