An apparatus includes an optical data modulator, an electrical tuner located to control an operating wavelength of the optical data modulator, a photo-sensitive diode or photo-sensitive transistor, and an electronic feedback controller. The photo-sensitive diode or photo-sensitive transistor is connected to receive light from an optical output of the optical data modulator and is configured to output an electrical signal representative of a measured intensity of said received light. The electronic feedback controller is connected to receive the electrical signal from the optical intensity detector and to operate said electrical tuner based on an alternating current component of said measured intensity.