Fiber lasers utilize an active gain medium that is an optical fiber doped with rare-earth elements such as erbium, dysprosium, holmium, neodymium, praseodymium, thulium, and ytterbium. Fiber laser advantages include:

• Light is already coupled into a flexible fiber: The fact that the light is already in a fiber allows it to be easily delivered to a movable focusing element. This is important for laser cutting, welding, and folding of metals and polymers.
• High output power: Fiber lasers can have active regions several kilometers long, and so can provide very high optical gain. They can support kilowatt levels of continuous output power because of the fiber's high surface area to volume ratio, which allows efficient cooling.
• High optical quality: The fiber's waveguiding properties reduce or eliminate thermal distortion of the optical path, typically producing a diffraction-limited, high-quality optical beam.
• Compact size: Fiber lasers are compact compared to rod or gas lasers of comparable power, because the fiber can be bent and coiled to save space.
• High peak power and nanosecond pulses enable effective marking and engraving.
• Lower cost of ownership.