Disclosed are an optical beam delivery device, systems, and methods for sequentially adjusting, with respect to members of a set of confinement regions, a propagation path for establishing a controllable, temporally apparent intensity distribution. The disclosed techniques entail applying to a variable beam characteristics (VBC) fiber different states perturbation to change the propagation path and the members of the set of confinement regions through which a confined portion of an adjusted optical beam propagates, thereby establishing at an output end of the VBC fiber the controllable, temporally apparent intensity distribution.