June 11, 2020
The transmission medium in fiber-optic communications systems is an optical fiber.The optical fiber is the transparent flexible filament that guides light from a transmitter to a receiver. An optical information signal entered at the transmitter end of a fiber-optic communications system is delivered to the receiverend by the optical fiber. So, as with any communications link, the optical fiber provides the connection between a transmitter and a receiver and ,very much the way copper wire and coaxial cable conduct an electrical signal, optical fiber "conducts" light .
The optical fiber is generally made from a type of glass called silica or, less commonly nowadays, from plastic. It is about a human hair in thickness. To protect very fragile optical fiber from hostile environments and mechanical damage. it is usually enclosed in a specific structure. Bare optical fiber , Shielded by its protective coating , is encasulated in several other layers that , all together, make up fiber-optic calbe ---the structure dinding widespread used in a host of applications .many of which will be covered in subsequent chapters.