"when we use Light is a transmission medium to send our information during communication so it,s called optical communication"
Optical Fiber ---- Optical mean_ Radiation of light &------Fiber mean_ Thread -----Light in Thread
The system of the optical fiber is very simple there is a transmitter so the job of the transmitter is to encodes these signals in to optical signals after sending these signals at the speed of 3x10^8 m/s now it,s the duty of the receiver to decode these optical signals and recover the original signal.
Laser Diode = Transmitter
Photo detector = Receiver
we can use many sources to generate light but most of the time Engineer chose Laser diode as a source of light the reason is that laser diode size is very small and it,s weight is very low, not a power hungry, low intensity with wide beam angle .
you can use other sources like Led, visible light and infrared light it,s depend upon on your requirements.
we can send information in the form of light pulses like when Light recevied at the receiver it,s mean 1 and if there is no light it,s mean 0 a binay data.
Light = 1 1 1 1 1 1 1
No light =0 0 0 0 0 0
At the receiving side we simply use Photo detector the job of photo detector is to convert those light pulses in to stream of electronics and then pass through a threshold device like if received signal amplitude is greater then 3 it,s mean "1" or else "0"
with the help of optical communication we achieve more and more speed like more bandwidth so this is the reason all of the countries in the world are connected with each other using Optical fiber under the sear like submarine cable .
Optical fibers are very sensitive it,s need more protection like coating to protect it from any kind of damages .
Disadvantages : Scattering, absorption of pulses and bent