DOUBLE-CLAD RARE EARTH DOPED OPTICAL FIBERS

摘要

An optical fiber (10) made with a central core (12), a first cladding layer (16), and a second cladding layer (18) having a series of perturbations or irregularities formed into the otherwise generally circular outer boundary of the first cladding layer. The irregularities in the first cladding layer interrupt the propagation of skew rays and encourage coupling into the core. The irregularities are formed by drilling holes (44-58) in the fiber preform, which are parallel with its longitudinal axis, and inserting rods therein. An intermediate cladding layer (14) is provided for suppressing higher order core modes. The optical fibers are used in cladding pumped fiber lasers and amplifiers.