Counterpropagating multicore optical fiber amplifier assembly

A fiber amplifier, comprising:

• a pump source, to generate a pump radiation;
• a fiber assembly, comprising a first input multi-core fiber and a first output multi-core fiber, disposed along a first optical path, and a second input fiber and a second output fiber, disposed along a second optical path;
• and
• a multi-core fiber amplifier assembly, arranged along the first optical path and the second optical path, and disposed between the first input multi-core fiber and the first output multi-core fiber, and further disposed between the second input fiber and the second output fiber,
• the multi-core fiber amplifier assembly comprising a plurality of optical isolators, wherein a given optical isolator of the plurality of optical isolators comprises:
• a non-reciprocal optical element;
• a first reciprocal element, disposed on a first side of the non-reciprocal optical element;
• a second reciprocal element, disposed on a first side of the non-reciprocal optical element;
• and
• a patterning element to selectively direct light through the given optical isolator according to a polarization of the light.