Active components: devices based on semiconductor laser technology that provide the light in a fiber optic network. They require the integration of electronics and wiring into a package using traditional assembly technologies. Receivers, transmitters, modulators, amplifiers and switches are examples of active components. These devices are generally easier to assemble than passive components.

Attenuation: the loss of optical energy a signal experiences as it travels through optical fiber. It determines the spacing of repeaters needed to maintain acceptable signal levels. Attenuation is one of the key factors that determine the cost of a fiber optic telecommunication network.