What happens to a ray of light incident on a boundary between two transparent?

Question

explain the operation principle of an optical
fibre, and how it has changed the world of communication

Answer 1

An optical fibre uses total internal reflection. What it does is it takes a signal from any device (lets say, from speakers) and converts it into digital format. This is then pressed on a carrier frequency, produced by either LED light or Laser light, and is sent through the fibre.
Some energy is lost along the way, so often there are booster stations to regenerate the signal.
Once the signal reaches its destination - ie, the other end, it is demodulated and processed as required by the user.

It has changed the world of communication because now huge amounts of data can be sent in very small amounts of time at high speeds.

Answer 2

This should explain everything you need to know....

http://en.wikipedia.org/wiki/Optical_fiber#Principle_of_operation