Introduction

In the past the light was used only to see things but not to communicate.Now we know that use of optical(light) waves can carry large amount of information.The air(Atmosphere) is not a very good transmission medium for optical communication.There are many reason for make signal attenuate..optical communication become a reality with the development of optical fibers.The optical fiber communication belongs to the category of wired communication.To carry this optical frequencies over long distance we need a guiding device.This device is the optical fiber.