A fiber laser is a type of laser in which the active medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, and thulium. It is a type of solid-state laser whose active medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, and thulium. Fiber lasers are highly efficient, reliable, and compact, and are used in many applications, such as cutting, welding, and marking.