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, and include a spherical particle material that is interior to the fiber cladding material and different than the fiber cladding material. To produce particles, a drawn fiber, having a longitudinal-axis fiber length and including at least one fiber core that has a longitudinal core axis parallel to the longitudinal fiber axis and that is internally disposed to at least one outer fiber cladding layer along the fiber length, is heated for a time that is sufficient to cause a fiber core to break-up into droplets sequentially disposed along the fiber core axis. Fiber cooling solidifies droplets into spherical particles interior to fiber cladding.