An electrical connector crimping tool die set for crimping an asymmetrical electrical connector onto at least one electrical conductor. In certain embodiments, an optical fiber stub is pre-installed in a ferrule bore of a ferrule of a fiber optic connector sub-assembly, to provide the pre-terminated fiber optic connector sub-assembly. Then the configuration of the line of intersection is determined so that an amplitude and a phase as the generated quantity of higher mode such as the TM11 mode generated in the waveguide portion 5 conform to desired values with respect to each higher mode.