For hundred of years man has communicated using flashes of reflected sunlight by day and lanterns by night.Navy signalmen
still use powerful blinker lights to transmit coded messages t o other ships during period of radio silence. Light
communication has not been confined to simple dots and dashes. It is an interesting but little known fact that Alexander Graham Bell invented a device known as"Photo Phone" shortly after his invention of telephone . Bell''s photo phone used a modulated beam of reflected sunlight, focussed upon a selenium detector several hundred meters away. With the device, Bell was able to transmit a voice message via a beam of light. The idea remained dormant for many years. During the recent post the idea of
transmission of light through thin optical fibers has been revived and is now bing used in communication technology.Point of Ponder.Each of the thin optical fibers is small enough to fit through the eye of a needle. why is the size of the fiber, important?"The use of light as a transmission carrier wave in fiber optics has several advantages over radio wave carriers such as much wider bandwidth capability and immunity from electromagnetic interference.It is also used to transmit light around corners and into inaccessible places so that the formerly unobservable could be viewed . The use of fiber optic tools in industry is now very common, and their importance as diagnostic tools in medicine has been proved. Recently the fiber optic technology has evolved into something much more important and useful; a communication system of enormous capabilities.