A regenerative amplifier is a device which is used for strong amplification of light pulses, usually with ultrashort pulse durations in the picosecond or femtosecond domain (→ ultrafast amplifiers). Multiple passes through the laser gain medium (nearly always a solid-state medium) are achieved by. Optical signals propagating in fiber-optic transmission systems are affected by several effects, namely amplified spontaneous emission (ASE) from optical amplifiers, chromatic dispersion, polarization-mode dispersion, and nonlinear phenomena. It is based on a pulse trapped in a laser resonator, which stays in there until it extracts all of the energy stored in the amplification medium. In-line amplifiers: Periodically amplify signal due to fiber attenuation, high G, high Psat. An illustration of the effective gainis given below. Note the presence of a gain peak around 1530nm and a semi-flat gain. Optical amplifiers are used to create laser guide stars which provide feedback to the adaptive optics control systems which dynamically adjust the shape of the mirrors in the largest astronomical telescopes.
