Backward amplified spontaneous emission from erbium-doped fibers as a measure of amplifier efficiency

Optical amplifiers using erbium-doped fibers (EDF's) are attractive for lightwave communications, especially because of the high gain and high output power they can provide at 1.5 µm. The rapid progress in the development of erbium-doped-fiber amplifiers (EDFA's) has led to the planning of many lightwave systems, both undersea and terrestrial. EDF performance is a key element in designing these systems. Optimization of the fiber conversion efficiency is particularly critical for lowering the required pump power, which results in increased pump reliability and lower power consumption.