Compact two-stage optical amplifier

The apparatus of claim Error! Reference source not found, further comprising:

• a first span of optical fiber or optical fiber cable coupled to the optical coupler;
• and
• a second span of optical fiber or optical fiber cable coupled to the optical coupler;
• wherein the optical amplifier is configured to amplify signals propagating between the first span and the second span.

A method of amplifying space division multiplexed (SDM) optical channels, comprising:

• receiving a plurality of SDM optical channels;
• coupling the plurality of SDM optical channels into a first plurality of cores of in a multicore rare-earth doped optical fiber at a first end of the multicore rare-earth doped optical fiber;
• pumping laser light into the multicore rare-earth doped optical fiber;
• coupling the SDM optical channels in the first plurality of cores into a second plurality of cores in the doped multicore fiber at a second end of the multicore rare-earth doped optical fiber;
• coupling the plurality of SDM optical channels from the second plurality of cores in multicore rare-earth doped optical fiber at the first end;
• and
• outputting the coupled plurality of SDM optical channels from the second plurality of cores.