Symmetric optical fiber layout to mitigate group delay mismatch in multi-core fiber

A coherent beam combining optical fiber, comprising:

• a fiber medium comprising an input facet configured to receive seed light and an output facet configured to output amplified light;
• and
• a plurality of cores arranged in the fiber medium, wherein each core of the plurality of cores is configured to guide a respective portion of the seed light and includes a respective gain medium for amplifying the respective portion of the seed light into a respective portion of the amplified light,
• wherein the input facet and the output facet are parallel surfaces that face in opposite directions such that a travel direction of the seed light entering the input facet is parallel to a travel direction of the amplified light exiting the output facet,
• wherein the fiber medium has a plurality of bends, including one or more left-handed bends and one or more right-handed bends,
• wherein a number of the one or more left-handed bends is equal to a number of the one or more right-handed bends,
• wherein a sum of bending angles of the plurality of bends is zero, wherein left-handed bending angles and right-handed bending angles have opposite signs, and
• wherein group delays of the plurality of cores are substantially matched as a result of an arrangement of the input facet and the output facet, and as a result of the sum of bending angles being zero.

A coherent beam combining assembly, comprising:

• a cold plate comprising a groove;
• and
• a multicore optical fiber mounted to the cold plate, inside the groove,
• wherein the multicore optical fiber comprises:
• a fiber medium comprising an input facet configured to receive seed light and an output facet configured to output amplified light;
• and
• a plurality of cores arranged in the fiber medium, wherein each core of the plurality of cores is configured to guide a respective portion of the seed light and includes a respective gain medium for amplifying the respective portion of the seed light into a respective portion of the amplified light,
• wherein the input facet and the output facet are parallel surfaces that point in opposite directions such that a travel direction of the seed light entering the input facet is the same as a travel direction of the amplified light exiting the output facet,
• wherein the fiber medium has a plurality of bends, including one or more left-handed bends and one or more right-handed bends,
• wherein a number of the one or more left-handed bends is equal to a number of the one or more right-handed bends such that an integrated bending angle of the fiber medium is zero, and
• wherein group delays of the plurality of cores are substantially matched as a result of an arrangement of the input facet and the output facet, and as a result of the integrated bending angle of the fiber medium being zero.