| 摘要 |
PURPOSE:To keep an optical output signal to be constant by executing the bias control of an electrooptical converting circuit based on the monitor voltage of an optical output, a reference voltage and control information to be stored to a storing circuit in advance. CONSTITUTION:An A/D converting circuit 4 A/D converts the monitor output voltage to correspond to the optical output of an electrooptical converting circuit 2. An A/D converting circuit 5 A/D converts a mark rate output voltage to correspond to the mark rate of a pulse signal which is inputted to a driving circuit 1. These outputs are inputted to an input and output port circuit 6 together with a referring digital voltage. An arithmetic circuit 7 compares the outputs of the A/D concerting circuits 4 and 5 and the referring digital voltage with the information to be stored to a storing circuit 8 in advance in correspondence to the electrooptical converting circuit 2 and generates a control signal. A bias control circuit 3 controls a bias so as to keep the optical signal from the electrooptical converting circuit 2 to be constant based on this control signal. |
