A fiber optic link provides a path for light signals to travel between a transmitter and a receiver. For proper performance, this path must be free of defects and installation errors; otherwise, these may interfere with the light pulses as they pass through the cable.
There are many different devices and methods used to assure the quality of a fiber optic link. Just as automobiles have gauges and warning lights to indicate different engine conditions and mechanical problems, the testers used by a fiber optic technician provide different measurements and indicators of the usability of the fiber link being tested.