Optical amplification is a fundamental concept and research area focused on increasing the power or intensity of an optical signal. It involves the physical process by which photons are added to a propagating light wave, typically through stimulated emission within a gain medium energized by an external pump source. As a research discipline, it investigates the underlying quantum mechanical principles, the properties and development of various gain media (such as rare-earth-doped fibers, semiconductors, or gases), the design and optimization of amplifier devices and systems, and the characterization of their performance metrics including gain, noise figure, bandwidth, and efficiency. Its significance lies in enabling critical technologies across numerous fields, most notably long-distance optical telecommunications, high-power laser systems, optical sensing, and spectroscopy, by allowing light signals to be strengthened without requiring conversion to electrical form.