A transmitter comprises a complex mixer to generate a single I analog drive signal and a single Q analog drive signal, and a single multi-dimensional optical modulator configured to modulate an optical carrier light using the single I analog drive signal and the single Q analog drive signal to produce a modulated optical signal for transmission. Alternatively, a transmitter comprises a complex mixer to generate two I analog drive signals and two Q analog drive signals, and a single multi-dimensional multiple-electrode optical modulator configured to modulate an optical carrier light using the analog drive signals to produce a modulated optical signal for transmission. In both transmitters, the optical carrier light is produced by a single laser, and frequency components of the first data signal are located in a different portion of a spectrum of the modulated optical signal than frequency components of the second data signal.