MODELING OF ION-PAIRS IN ERBIUM-DOPED FIBER AMPLIFIERS

The effects of Er-Er pairs on the characteristics of Er-doped fiber am plifiers are analyzed theoretically. Pairs are found to have little ef fect on the amplifier optimum length, signal saturation power, and noi se figure (at constant gain) but to cause significant reduction in the gain, even at residual levels, quantitatively consistent with fiber l aser measurements. A maximum tolerable fraction of paired ions near 8% , corresponding to approximately 400 mole pats in 10(6) Er2O3, is pred icted for near-optimum gain efficiency in Al-Ge silica fibers.