ABSTRACT
The optical fiber carries the optical signal between the transmitter and receiver. Although free space transmission can be used, fiber offers a number of advantages. Fiber carries light around comers, so that fiber optic systems are not limited to line–of–sight transmission, and alignment of transmitter and receiver is not required. The fiber must have good optical coupling of light from the transmitter and into the receiver. A fiber is constructed of a core surrounded by a cladding. The core and cladding are both made from glass, with only a small difference in doping. The fiber is characterized by its optical characteristics, which are determined by the glass doping. The step–index fiber is made from a higher index rod of glass surrounded by a lower index glass coating. The graded–index fiber has a core made from many layers of glass. Bending losses occur when the fiber is bent.
