The present invention relates to the design and operation of a frequency selective electrooptic source. In accordance with one embodiment of the present invention, the electrooptic source comprises an optical signal generator, optical circuitry, and at least one optical/electrical converter wherein the optical signal generator comprises a plurality of optical outputs characterized by distinct output frequencies and the optical circuitry is configured to permit the selection and combination of different ones of the distinct-frequency optical outputs to generate a modulated optical signal, which is converted to a millimeter or sub-millimeter wave. Additional embodiments are disclosed and claimed.