Various things affect the way the light is transmitted - including the quality of the original light source, the exact composition of the transmitting fibre, and the material used for the walls of the fibre. Each of these qualities must be understood in order to predict what the light will do under differing circumstances. To send a flash or 'pulse' of light along an optical fibre you need something to generate the light in the first place. You could use a hand-held torch but this would be very slow and inefficient. The optical fibre communications network uses lasers to generate a suitable light source.
Lasers can produce very tightly focused pulses of light and they can do it many times a second.
The pulses are then picked up at the other end of the fibre by a light-sensitive cell which can convert the pulses of light into pulses of electricity. These pulses of electricity are then fed into a computer and decoded to reveal the message. Using the flashes of light to carry a message Simply flashing messages down an optical fibre on the 'one flash for yes, two flashes for no' principle would take a very long time. In fact, using a combination of codes, many messages can be sent along an optical fibre at the same time. In many ways, optical fibre systems work in the same way as electrical cables but they are cheaper, more reliable and much, much faster.