Optical amplifier to increase optical power

An optical amplifier is a device which receives some input signal light and generates an output signal with higher optical power. Typically, inputs and outputs are laser beams (very rarely other types of light beams), either propagating as Gaussian beams in free space or in a fiber. Light underpins much of today's technology, from televisions and satellites to the fiber optic cables that transmit internet data across continents. An illustration of the effective gainis given below. Credit: Jim Gensheimer for Stanford. [pdf]