Optoelectronic transmitter having an improved power control circuit for

Abstract

An optoelectronic transmitter is provided including a laser diode. A control circuit for driving the laser diode includes a current source which provides a DC bias current to the laser diode, and the laser diode emits an optical signal having an average power determined by the magnitude of the bias current. A voltage regulator establishes a regulated supply voltage which is input to a first reference circuit and a feedback monitor circuit. The first reference circuit establishes a first fixed reference voltage. The feedback monitor circuit includes a monitor device for measuring the optical power emitted by the laser diode, and the monitor circuit establishes a variable monitor voltage proportional to the optical power measured by the monitor device. An op-amp compares the first fixed reference voltage and the feedback monitor voltage, and the output voltage of the op-amp controls the magnitude of the bias current output by the current source. A disable switch is incorporated for selectively blocking the bias current to the laser upon receipt of a DISABLE signal. A second reference circuit is provided for developing a second derived reference voltage, and an analog switch which is also actuated by the DISABLE signal connects the second derived reference voltage to the feedback monitor circuit while the DISABLE signal is active. Otherwise, the analog switch connects the regulated supply voltage to the feedback monitor circuit at all other times.