Design optimization for efficient erbium-doped fiber amplifiers

The gain and pumping efficiency of aluminosilicate erbium-doped fiber amplifiers (EDFAs) are analyzed as a function of guiding parameters and Er-doping profile for two pump wavelengths of lambda /sub p/=980 nm and lambda /sub p/=1.47 mu m. Three designs of fiber-amplifier waveguides are considered: one with the same mode size as standard 1.5- mu m communication fibers (type 1); one with the same mode size as standard 1.5- mu m dispersion-shifted fibers (type 2); and one with mode size smaller than those of communication fibers (type 3). For the 1.47- mu m pump, fundamental LP/sub 01/ mode excitation is assumed, while for the lambda /sub p/=980-nm pump, concurrent excitation of LP/sub 11/ modes is considered. It is shown that excitation of higher-order pump modes at 980 nm does not significantly affect the amplifier gain performance. The effect of concentrating the Er/sup 3+/ doping near the center of the fiber core is shown to increase the amplifier gain coefficients by a factor of 1.5 to 2.<
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