The fiber laser uses a rare earth doped fiber as the gain medium, and the pump light forms a high power density in the core, resulting in a "particle number reversal" of the doped ion level. When a positive feedback loop (constituting a resonant cavity) is properly added, A laser output is produced.

Fiber lasers are used in a wide range of applications, including fiber optic communications, laser space telecoms, shipbuilding, automotive manufacturing, laser engraving machines, laser marking machines, laser cutting machines, printing rolls, metal non-metallic drilling/cutting/welding (Bronze welding, quenching, cladding and deep welding), military defense security, medical equipment and equipment, large-scale infrastructure construction.

A fiber laser, like other lasers, consists of a working medium that generates photons, a photon that is fed back and resonantly amplified in the working medium, and a pump source that excites the optical transition, but the working medium of the fiber laser. It is a doped fiber that acts as a waveguide at the same time. Therefore, the fiber laser is a waveguide type resonance device.

The fiber laser is generally optically pumped. The pump light is coupled into the fiber. The photons at the pump wavelength are absorbed by the medium to form a population inversion. Finally, the excited radiation is generated in the fiber medium to output the laser. Therefore, the fiber laser Essentially a wavelength converter.

The cavity of a fiber laser generally consists of two sides and a pair of plane mirrors, and the signals are transmitted in the cavity in the form of a waveguide.