OPTICAL MODULATING DEVICE AND OPTICAL TRANSMITTING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical modulating device capable of correcting a shift of the operation point of a controlled optical modulator from the optimum point by an ABC circuit to which a monitor signal having a bias shift is input, and an optical transmitting device.

SOLUTION: An adding circuit 103 logic-inverts the monitor signal input from the optical modulator 101 and a low-frequency signal input from a variable ATT 108 and output from a low-frequency generating circuit 110, and adds them to an offset signal attenuated by an arbitrary amount. The adding circuit 103 adds the monitor signal and offset signal to each other and outputs the addition signal to a synchronous detection circuit 104. The synchronous detection circuit 104 detects the low-frequency signal component superposed on the addition signal and outputs it to an integrating circuit 106 through an LPF 105. The integrating circuit 106 generates an operation point control signal based upon the low-frequency signal component detected from the addition signal, and an adding circuit 107 adds the operation point control signal and low-frequency signal to each other and applies the resulting signal to the optical modulator 101.

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