A fiber is provided, including a cladding material that is disposed along a longitudinal-axis fiber length. A plurality of spherical particles are disposed as a sequence along a longitudinal line parallel to the longitudinal fiber axis in at least a portion of the fiber length. Each spherical particle is of a spherical particle material that is interior to and different than the fiber cladding material. The spacing between adjacent spherical particles in the sequence of particles is greater than the spherical particle diameter. Each spherical particle can be provided as a core- shell particle that includes a spherical core that is surrounded by at least one spherical shell. Each spherical particle can be provided with a plurality of azimuthal sections of at least two distinct materials.