THEORETICAL AND EXPERIMENTAL INVESTIGATIONS ON ERBIUM-DOPED FIBER AMPLIFIERS

A comprehensive model of erbium-doped fiber amplifiers (EDFA) is propo sed in this paper, taking exited-state absorption (ESA), amplified spo ntaneous emission (ASE), background absorption, mode field, and Erbium ion radial distribution into account. Computer programs capable of ha ndling forward, backward, and different wavelength bidirectional pumpi ng are developed. Among other things, it is found that under typical c onditions, Gaussian field approximations may cause considerable errors . The optimum V-value for small signal gain is much smaller than that for minimum Gaussian or Desurvire spot size; ASE propagating opposite to the pump beam can be several times higher than at propagating along the pump beam, resulting in a faster-than-linear decrease of the pump power at its beginning portion. Experimental results of domestic-made erbium-doped fibers pumped by 980 nm and 1480 nm laser diodes are als o given.