Submarine cable and satellite are two indispensable communications systems in use in the modern world. The economic prosperity enjoyed in the Republic of China has led to a considerable increase in its international communications activities. As well as advancing its satellite communications system, the ROC has set up three submarine cables connecting Okinawa, Luzon and Guam, thereby allowing its communications enterprises to enter a new era.
Rapid development of science and technology has led to progress in several telecommunications services, including telegraph, telephone, telex, television and data processing. The satellite communications system has been integrated with the submarine cable system to bridge the gap between nations and people.
Satellite. The first submarine cable was laid between England and France across the straits of Dover 115 years earlier than the first satellite was launched in 1965. The story goes that the cable was so fragile that a fishing boat severed it and the crew mistook it for a rare type of seaweed. After a century of research and improvement, the cables of today consist of a steel tube two inches wide known as a "single coaxial cable."
Problems posed by war and economic recession since the start of the 20th century prohibited the rapid development of the submarine cable system. The development of communications satellites, on the other hand, proceeded rapidly. Today, submarine cable systems crossing the three oceans connect continents in conjunction with well-established satellite systems in an integrated telecommunications network.
Commercial international satellite communications were first introduced in 1965 when the INTELSAT I (Early Bird) satellite was successfully launched. At present, there are nine such satellites, five over the Atlantic Ocean, and two each over the Pacific and Indian Oceans. The INTELSAT system uses geostationary satellites in orbit above the earth's equator at 36,000 Km (23,000 miles). Members of INTELSAT organization entrust the U.S. National Aeronautics and Space Administration (NASA) to launch these satellites with a maximum capacity of 5,000 voice channels.
Satellite communication has the merits of large capacity in transmission power, convenient installation of transoceanic TV terminals, and low cost. After they have set up ground stations with transmitters and receivers, several countries and areas may share a satellite. So far, the Republic of China has rented 343 satellite voice channels--265 stationed above the Pacific Ocean and 78 above the Indian Ocean. Two huge parabolic dish type antennas have been installed at the ground station in Yangmingshan.
Submarine cable. Though it is more expensive to lay submarine cable, its communication system is more stable and transmission is faster. It is free from the threat of typhoons or the danger of being bugged. When the satellite system is out of order, submarine cable can readily take its place to continue telecommunications operations.
In order to provide high-quality and efficient service, the international Telecommunications Administration (ITA) of the Republic of China has allocated NT$3 billion (US$83 million) since 1977 to lay cables between Taiwan and Okinawa, Guam and Luzon respectively to connect with major global submarine cables leading to Japan, Korea, Hong Kong, Singapore, the Philippines, Hawaii, the Continental U.S., Canada, New Zealand, Australia and New Guinea.
Before submarine cables can be laid, tests must be conducted to decide on the most suitable route. A flat and solid sea bed, stable sea temperatures, and a lack of strong tides or currents are considered ideal conditions for cable laying. Deep trenches and geological fault lines are avoided to prevent damage.
Work begins with the installation of equipment and cables at terminal stations on land. The so-called land operation gets under way when a cable engineering boat drops anchor several miles out to sea. Plastic float balls are attached to the cable at a distance of every two meters. A trawler with high horsepower engine then tows the heavy cable out. Buoyed by the plastic balls, it looks like a centipede creeping toward the shore. Simultaneously, an earthmover is digging out a deep trench leading toward the terminal station.
After the cable is placed in the trench and covered with earth, it is connected to equipment at the base of the terminal station and then to communications systems in the ITA. Divers then cut off the floating balls to allow the cable to sink to the sea bed, and land operations are finished.
Sea operation is totally mechanical. The cable ship automatically drops a machine to the sea bed to dig out a trench. When the cable is in place, it is covered with concrete. Engineers watch the operation from on board ship and operate the machines by remote control.
Structure. The cable is made of steel wires covered by an inner conductor, dielectric outer conductor and sheath. If the cable is laid in shallow sea, it is armored, in deep sea, this is not necessary. The cables have repeater amplifiers attached at intervals of several nautical miles to boost the strength of signals. Another important device is an equalizer in the shape of rocket which eliminates static and stabilizes voice transmission.
Through the successful installation of submarine cable systems, the Republic of China has reached a new milestone in communications which will eventually help overall economic development and international cultural exchanges.
[Picture Caption]
Submarine cable is one of the most advanced communications systems in us e in the modern world. Laying it involves complex and challenging engineering work. Picture left shows land operation. Below is a chart showing submarine cable networks around the Pacific Ocean.
To begin the land operation, plastic float balls are attached to the cable, before a trawler with high horse power engine tows the heavy cable out.
Engineers on board the cable boat are busy tying float balls to a cable. Buoyed by the plastic balls, the cable will not sink to the sea bed in the first stage of operation.
Submarine cable is one of the most advanced communications systems in us e in the modern world. Laying it involves complex and challenging engineering work. Picture left shows land operation. Below is a chart showing submarine cable networks around the Pacific Ocean.
To begin the land operation, plastic float balls are attached to the cable, before a trawler with high horse power engine tows the heavy cable out.
Engineers on board the cable boat are busy tying float balls to a cable. Buoyed by the plastic balls, the cable will not sink to the sea bed in the first stage of operation.
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