Exercise 29. Read the text quickly and choose the best title, A, B, or C

A. The history of cabling and telecommunications.

B. A short introduction to optical fibres.

С. Uses of glass in industry and technology.

Optical fibres started to replace some uses of copper cables in the 1970s. They are made from glass and are usually about 120 micrometres in diameter. Some of the most common everyday uses are in telecommunications, close-circuit television (CCCTV), and cable television.

1____________________________________________________________Optical fibres carry signals more efficiently than copper cable and with a much higher bandwidth. This means that fibres can carry more channels of information over longer distances.

2 ____________________________________________________________

Optical fibre cables are much lighter and thinner than copper cables with the same bandwidth. This means less space is needed in underground cabling ducts.

3 ____________________________________________________________

It is difficult to steal information from optical fibres. They are not harmed by electromagnetic interference, for example from radio signals or lightning. They don't ignite so they can be used safely in flammable atmospheres, for example in petrochemical plants.

4____________________________________________________________ Optical fibres are more expensive per metre than copper. However, one optical fibre can carry many more signals than a single copper cable and the longer transmission distances mean that fewer expensive repeaters are required. Also, copper cable uses more electrical power to deliver the signals.

5____________________________________________________________

Optical fibres can't be spliced as easily as copper cable. Employees need special training to handle the expensive splicing and measurement equipment.

Exercise 30. Read the text again and match the headings (A-E) with the paragraphs (1-5).

A Training and skills D Price

B Size and weight E Capacity

C Security

Exercise 31. Which paragraphs describe advantages of optical fibres and which describe disadvantages?