Exercise 2. Complete the sentences with words from the text.

1. At the head end of the chain is the … .

2. Light pulses move easily down the fiber-optic line because of a principle known as … .

3. … is the light carrying element at the center of the optical fiber.

4. Surrounding the core is … made of pure silica.

5. The outer jacket is added to protect against … .

6. The transmitter accepts … coming from copper wire.

7. A light-emitting diode or an injection laser diode can be used for … .