An optical modulator for generating an optical information signal includes a first modulator that modulates an optical carrier with a clock signal. The insulating sheet has windows therethrough at positions corresponding to those of connection pads of the wiring substrate and has leads, one end of each of the leads being fixed on the sheet and the other end of each of the leads protruding from the opposite surface of the sheet through a window. If an overcurrent is recognized, the overcurrent indication portion is operated, and the base current of the output transistor circuit is controlled to perform protection of the output circuit from the overcurrent.