An optical fiber amplifier includes a length of silica optical fiber having a
core doped with neodymium, a first cladding and a second cladding each with succeeding
lower refractive indices, where the first cladding diameter is less than 10 times
the diameter of the core. The doping concentration of the neodymium is chosen so
that the small signal absorption for 816 nm light traveling within the core is
less than 15 dB/m above the other fiber losses. The amplifier is optically pumped
with one laser into the fiber core and with another laser into the first cladding.