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What is a Rare-Earth Doped Fiber?
A rare-earth doped fiber is an optical fiber whose glass core is doped with rare-earth ions to provide optical gain. These fibers act as the gain medium in fiber lasers and optical amplifiers, enabling light to be amplified or generated directly within the fiber.
Common rare-earth dopants include erbium, ytterbium, thulium, holmium, and neodymium, with each providing different absorption and emission characteristics and therefore targeting different wavelength ranges and applications.
HOW a Rare-Earth Doped Fiber Works
Rare-earth doped fibers work by absorbing energy from a pump source and transferring this energy to the optical signal through stimulated emission. The choice of rare-earth dopant determines the wavelength range and performance of the resulting laser or amplifier.
Pump absorption
Rare-earth ions embedded in the fiber core absorb energy from a pump laser at a suitable wavelength.
Energy transfer
The absorbed energy excites the rare-earth ions to higher energy levels, creating the conditions required for optical gain.
Stimulated emission
An optical signal passing through the fiber stimulates the excited ions to emit photons, amplifying the signal. In a laser cavity, the same process can generate laser light.
