A review of the fabrication and properties of erbium-doped fibers for optical amplifiers

Erbium-doped fiber has become the central component of nearly all optical amplifiers. Applications reported include repeaters, power amplifiers, preamplifiers, and distributed amplifiers. To date, nearly all the fiber used in these devices has been silica based and fabricated by variations on the major telecommunications fiber technology. Disadvantages of the silica-based host glass, such as low solubility of the rare-earth ions and narrowband fluorescence, have been carefully addressed and solutions have been found to overcome these potential drawbacks. Details of the current status of fabrication methods, matching particular fibers for specific applications, together with optimizing the fiber for high efficiency, are presented