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FIBRE OPTICS AND COMMUNICATION



Key terms: fibre optics, optical signals, ultrapure glass fibre, total internal reflection, light pipe, image, transparent, light signal transmission, glass fibre technology, jamming, signal leaking

 

1. Fibre optics is the transmission of optical signals through strands of ultrapure glass fibre the thickness of human hair. The main principle of fibre optics is total internal reflection through a curved fibre. Special plastic and glass fibres a few micrometers in diameter have recently been developed to transmit light from one place to another. A bundle of these fibres is called a light pipe. Light can be transmitted through a light pipe for several kilometres with little loss in intensity. Light pipes can be used to illuminate inaccessible places, to transmit telephone calls and other modulated signals, and to carry out internal examination of the body. The finer the fibres and the greater their number, the clearer and more detailed the image being transmitted.

2. The idea of using light to transmit information is not new. In 4880, Alexander Graham Bell invented a «photophone» that used a narrow sunbeam to transmit voices over a short dis­tance. He said, «I have heard articulate speech produced by sunlight! I have heard a ray of the sun laugh and cough and sing!» However, Bell's other invention, the telephone, was con­sidered more promising at the time and the photophone was set aside. Light sign al transmission has become practical today due to advantages in laser and glass fibre technology.

3. Optical fibres have several advantages over traditional tele­phone cable. Glass fibres deliver a clean signal because they are immune to electrical interference, jamming and signal leaking. They also prevent eavesdropping. As well, glass fibres carry more information per square centimetre of cross-sectional area than do copper telephone cables. Twelve hair-thin optical fibres, inside a protective sheathing, can carry 48,000 two-way phone calls at the same time. Transmitting this number electrically would require a bulky coaxial cable the thickness of a man's arm.

4. Fibre optics can integrate two separate industries - tele­phone and cable television. Unlike electrical signals on a cable, light waves can pass right through one another without affect­ing each other. As a result, many kinds of information can be sent simultaneously along a single fibre. Because both telephone and television signals can be sent on the same fibre, we may ябоп not need two separate cable systems.

5. To transmit across the Atlantic Ocean, American and Euro­pean telecommunications administrations have plans to install the first Trans-Atlantic fibre optic cable. This cable will handle 560 million bits of information each second. This is equivalent to 40,000 simultaneous conversations taking place along the same line.

6. Compared to traditional telephone cable, fibre optic cable is cheaper, more reliable, and can transmit not only voice, but data and visual images as well. Who knows — you too may be using this modern medium soon.

 

 

Exercise 1. Find the synonyms to the following words in the text:

1. super clean (1)                                           6. conventional (3)

2. complete (adj.), entire (1)                          7. wire (3)  

3. leakage (1)                                                 8. to stop (3)

4. unavailable (1)                                           9. demand (3, 4) 

5. distinct (2)                                                 10. big, clumsy (3).

 

Exercise 2. Make up the word-combinations:

traditional                                                              sunbeam

optical                                                                    sheathing

light                                                                       pipe

narrow                                                                   industries 

protective                                                              cable  

separate                                                                  image 

visual                                                                     signal.

 

Exercise 3. Say if the statements are true or false:

1. Transmitting light through a light pipe avoids signal leaking.

2. As light waves do not interfere in fibres, much information can be sent along a single fibre at the same time.

3. Glass fibres deliver a clean signal, because they are not affected by signal leaking.

4. It is impossible to transmit across the oceans.

5. Traditional telephone cable can transmit voices, data, visual images.

 


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