Abstract: Ultrashort pulse time hopping code-division-multiple-access (CDMA) and time-division-multiple-access (TDMA) RF IR and optical communications systems in the time-frequency domain comprises a transmitter including a short duration pulse/packet generator for generating a short duration pulse/packet in the femtosecond to microsecond range and a controller for controlling the generator, code means connected to the controller for varying the time position of each short pulse/packet in frames of pulses/packets in orthogonal superframes of ultrafast time hopping code and time division multiple access format, precise oscillator-clock for controlling such timing, encoding modems for transforming intelligence into pulse/packet position modulation form, antenna/amplifier system. Preferably, the codes are orthogonal codes with the temporal coding of the sequence of ultrafast pulses/packets constituting the carrier for transmission by the antenna system.