A driving device including a light emitter, a biasing circuit, a light receiver, an automatic control system, and an alternating current (AC) path is disclosed. The light emitter generates an optical signal. The biasing circuit generates a driving signal to activate the light emitter such that the light emitter operates in a working range. The light receiver detects the output power of the optical signal for generating a corresponding electrical signal. The automatic control system adjusts the driving signal according to the corresponding electrical signal such that the output power of the optical signal approaches a preset value. The AC path is coupled between the light emitter and an external signal source for receiving at least one AC modulated signal such that the light emitter generates at least one modulated optical signal.