Submarine optical cables are laid on the sea floor to establish telecommunication transmission between countries. There are not only submarine optical cables on the seabed, but also a large number of optical cables on the land. These fibre optic cables connect networks and telephone networks around the world. Thus, we can easily access the network of countries all over the world or make international long distance calls at home. Because the earth is a huge sphere, about 71% of its surface area is occupied by the sea. So most of the fibre optic cables we lay are at the bottom of the sea.

Why Fiber Optic Cable is so Important in International Communication？

At the bottom of the sea, the ecological environment is complex and there are many marine organisms. In order to ensure the reliability of submarine communication, it is necessary to select an appropriate transmission medium. Optical fiber transmission has become a good choice. Optical fiber transmission has many advantages, such as less energy loss, strong transmission ability, strong anti-interference, high security, small size and light weight, so it has incomparable advantages in long-distance transmission and special environment. Moreover, time delay is almost not felt in optical fiber communication. The design life of submarine optical cable is 25 years. Submarine optical cables are usually buried 1-2 metres below the seabed. But because the seabed is not very regular, optical cables sometimes inevitably come out. The cable may be destroyed when the fishing vessel anchors and trawls are used. Therefore, the place where the cable passes through the seabed is designated as a no-anchoring zone and the vessel is not allowed to berth.

As people's demand is more and more extensive, more and more information is transmitted in optical cable. In addition to our usual telephone, telegram, fax, there are now a large number of transmission of television signals, bank remittances, stock market prices and other information can not be interrupted for a moment.

A cable consists of several fibers. The transmission rate of optical fiber is much higher than that of copper wire. Optical fibers have large information capacity and high stability. Optical cables have great anti-interference ability to electromagnetic noise such as radio, motor or other adjacent cables.

In terms of current technological development, optical cable is the most powerful communication carrier in the world. Take China's first submarine optical cable as an example. It is 1252 km long from Pudong New Area in Shanghai to Miyazaki in Kyushu, Japan. It was officially opened in December 1993. This submarine optical cable system has a total communication capacity of 7560 call circuits, which is 15 times the capacity of China-Japan submarine coaxial cable built in 1976. The opening of this submarine optical cable increased China's international communication capacity by more than 80%.