DRIVING CIRCUIT FOR ELECTRIC FIELD ABSORPTION TYPE OPTICAL MODULATOR AND OPTICAL TRANSMITTER USING THE SAME

摘要

PROBLEM TO BE SOLVED: To stabilize the bias voltage of an optical modulator and to prevent wavelength deterioration at the time of long-distance transmission by supplying a bias current controlling an applied voltage according to the difference between a value detected by a peak value detecting circuit and a specific value. SOLUTION: A bias stabilizing circuit 4 compares the peak value voltage of the anode type voltage Vm of the electric field absorption type optical modulator AE detected by a peak detecting circuit 3 with a reference voltage (0V). A bias current supply circuit 5 to which the difference voltage from the bias stabilizing circuit 4 is inputted converts the difference voltage into a corresponding current. The bias current supply circuit 5 supplies the converted current in the opposite direction from the driving current outputted from a driving circuit so that the current converted corresponding to the difference voltage is subtracted from the driving current outputted from the driving circuit composed of a differential couple of FETs J1 and J6. Therefore, the current flowing to a resistance RL is brought under feedback control so that the anode-side voltage Vm of the electric field absorption type optical modulator EA becomes 0.