1. Context

Optical amplification is a process in which photons from an intense light source known as a "pump" are transferred to a less intense light signal, which is then amplified. This process enables "all-optical" amplification of light signals without the need for optical-to-electronic conversion, and therefore without the use of conventional electronic amplification techniques. There are several types of optical amplification based on different physical effects. These include rare-earth ion-doped fiber amplifiers