An optical fiber includes multiple cores and a cladding. At least one of the multiple cores forms an optical waveguide and has an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction. The cladding surrounds the multiple cores and has a refractive index that differs from at least one refractive index of the multiple cores. The multiple cores could be stacked such that a first of the multiple cores is located at least partially over a second of the multiple cores in the fast-axis direction. The optical fiber could include an additional core within the cladding and having a substantially circular cross-section. The cores could be used to transport a high-power laser beam, an illumination laser beam, and an alignment laser beam. The optical fiber could have a length of at least two meters.