Apparatus for optically pumping a clad amplifier fiber includes one or
more transmission fibers arranged and configured to insert pump-light
from a pump light source such as a diode-laser into the cladding of the
amplifier fiber. The pump light propagates through the cladding and a
portion of the pump light is absorbed in the doped core of the amplifier
fiber. At least one of the transmission fibers is arranged to receive an
unabsorbed portion of the propagated pump light from the amplifier
cladding and re-insert the unabsorbed portion of the pump-light into the
cladding for re-propagation through the cladding. This provides that pump
light that would otherwise be wasted is circulated through the amplifier
fiber for further absorption by the amplifier core.