In some implementations, a fiber optic combiner may comprise an enclosing tube having a geometric shape and multiple optical fibers bundled within the enclosing tube. In some implementations, the multiple fibers comprise at least one optical fiber having a core and a non-circular cladding surrounding the core. The non-circular cladding may cause the multiple optical fibers to have a larger tube fill factor and a lower expected beam parameter product increase factor relative to the multiple optical fibers all having circular claddings.