Abstract: An optical wavelength stabilizing system including a laser diode for emitting signal light, a Peltier element for controlling a temperature of the laser diode, and a drive circuit for driving the Peltier element. The signal light is branched into two components by an optical coupler. In an optical path of one of the two components obtained by the optical coupler, there is inserted an optical filter having a portion whose transmittance continuously changes according to wavelength. The signal light component passed through the portion of the optical filter is detected by a photodetector. An output current from the photodetector is converted into a voltage, which is then input into a comparator. The comparator compares the voltage output from the photodetector and a reference voltage to input a voltage difference therebetween into the drive circuit.

Abstract: An optical transmitter for optimizing the duty ratio of a high-speed optical transmission signal has an output unit for providing an optical output signal according to an electric signal, a monitor circuit for providing an output representative signal related to the output of the output unit, a driver for determining the logical value of each bit of an input data signal according to a reference voltage and driving the output unit according to the determination, an input signal detector for providing an input representative signal according to the input data signal, and a duty ratio controller for comparing the input and output representative signals with each other and controlling the reference voltage to the driver so that the difference between the input and output representative signals is reduced, to thereby optimize the duty ratio of the optical output signal.