А. Заполните пропуски словами.

Optical fibres are made of glass and use light (usually from a laser) to transmit messages. There is no doubt optical fibre systems have enormous advantage over conventional transmission systems. They have a much higher capacity than copper wires, can carry much more information and have a potentionally lower material cost. Besides, optical fibres occupy far less space. The quality of transmission is high as well. The signal soes not need to be amplified as often as with existing cables. Optical fibres do not suffer from interference.

B. Заполните пропуски словами.

Nowadays, lasers are used to identify targets in military uses. In engineering, powerful laer beams can be focused on a small area. They can melt, vaporize or heat material in a very precise way. Lasers are ideal for communication in space. Laser light can travel long distance without losing signal strength. In medicine, laser beams can be used for the treatment of damaged tissue in a fraction of a second without causing harm to healthy tissue. In the arts. lasers can provide fantastic displays of light. Pop concerts are often accompanied by laser displays.