Text № 15 b Modern Light-Wave Communications Technology Read the text. Try to understand all details. Use a dictionary if necessary:

A few decades ago, the concept of using light pulses instead of electrical signals to transmit information was only that — a concept. Today, lightwave communications systems are among the most sophisticated transmission systems in the telecommunications network. They are at once efficient, versatile and relatively inexpensive to install and maintain.

The efficiency of lightwave systems is perhaps their most renowned quality. They carry enormous amounts of information over long distances at very high speeds. Consider, for example, the speed and capacity of the Bell System's long distance lightwave system. Light pulsing through a single, hair-thin glass fiber in this system can transmit the entire contents of Webster's unabridged dictionary — more than 2700 pages — over thousands of miles in only six seconds.

No less impressive than this tremendous speed and capacity is the versatility of light-wave systems. Because they are digital systems they can transmit easily any of these types of information: voice signs, high-speed data signals, and television signals. Without undermining quality or efficiency, a single system can accommodate thousands of telephone conversations, and alternately handle data or video signals.

Finally, lightwave systems are inexpensive to install and operate compared to their wire-and-cable counterparts. Moreover, they allow considerable savings.

The reasons for such savings stem from the technology of lightwave communications. Conventional telecommunications transmission is based on the conduction of electrons through metal (usually copper wires). Lightwave systems, however, substitute protons for electrons and glass fibers for copper. These technological differences translate into big savings, the most significant of which is in construction costs. Because lightguide cables are only a fraction of the diameter and weight of copper cables, they are easy to handle and take up far less space. They can be installed in existing underground ducts and rights-of-way sometimes right next to copper cables.

In addition, lightwave systems eliminate certain equipment and operating costs. They are immune to electromagnetic interference and therefore require no protection from it. Also, light can travel much farther through lightwave cables without regeneration than can electrons through copper carrier systems. This is because the light encounters little resistance from the very pure glass fibers through which it travels. Lightwave systems require significantly fewer signal regenerators than do electrical digital carrier systems: typically one every ten miles instead of one every mile.

Notes

1. their most renowned quality — їх найвідоміша властивість

2. translate into big savings — дають велику економію

3. right-of-way — полоса відчуження

4. are immune to electromagnetic interference — не чутливі до електромагнітної інтерференції