Abstract: An optical transmission apparatus includes a modulation unit that generates modulated light by modulating light while bias on which a low-frequency signal is superimposed is applied thereto; an optical amplification unit that generates amplified light by amplifying the modulated light while holding an intensity of the amplified light at a changeable target value; an optical detection unit that generates an electric signal by performing photoelectric conversion on a part of the amplified light; an amplification unit that amplifies the electric signal while suppressing variation in the amplified electric signal, the variation being due to a change of the target value; and a control unit that detects a low-frequency component from the amplified electric signal the variation of which is suppressed and controls the bias on a basis of the detected low-frequency component, the low-frequency component being generated by the low-frequency signal.

Abstract: An optical transmission apparatus includes a modulation unit that generates modulated light by modulating light while bias on which a low-frequency signal is superimposed is applied thereto; an optical amplification unit that generates amplified light by amplifying the modulated light while holding an intensity of the amplified light at a changeable target value; an optical detection unit that generates an electric signal by performing photoelectric conversion on a part of the amplified light; an amplification unit that amplifies the electric signal while suppressing variation in the amplified electric signal, the variation being due to a change of the target value; and a control unit that detects a low-frequency component from the amplified electric signal the variation of which is suppressed and controls the bias on a basis of the detected low-frequency component, the low-frequency component being generated by the low-frequency signal.

Abstract: An optical module includes: an optical modulator, a superimposing unit, an offset adding unit, a detector, and a bias controller. The optical modulator includes a first modulator to generate a first optical signal, a second modulator to generate a second optical signal and a phase shifter to provide a specified phase difference between the first optical signal and the second optical signal so as to generate a modulated optical signal. The superimposing unit superimposes a low frequency signal on a DC bias of the first modulator. The offset adding unit adds an offset to a DC bias of the second modulator. The detector detects a low frequency component from output light of the optical modulator. The bias controller controls a DC bias that is applied to the phase shifter based on the low frequency component detected by the detector.

Abstract: An optical module includes: an optical modulator, a superimposing unit, an offset adding unit, a detector, and a bias controller. The optical modulator includes a first modulator to generate a first optical signal, a second modulator to generate a second optical signal and a phase shifter to provide a specified phase difference between the first optical signal and the second optical signal so as to generate a modulated optical signal. The superimposing unit superimposes a low frequency signal on a DC bias of the first modulator. The offset adding unit adds an offset to a DC bias of the second modulator. The detector detects a low frequency component from output light of the optical modulator. The bias controller controls a DC bias that is applied to the phase shifter based on the low frequency component detected by the detector.

Abstract: An optical transmitter has an optical modulator having Mach-Zehnder interferometers, modulator drivers configured to drive the optical modulator by a drive signal, a low frequency generator configured to generated a low frequency signal that changes a ratio of a driving amplitude with respect to a half-wave voltage of the optical modulator, a photodetector configured to detect a portion of output light of the optical modulator, a detector configured to detect a low frequency component contained in a detected signal from the photodetector using the low frequency signal, and a bias voltage controller configured to control a bias voltage for the optical modulator such that the detected low frequency component becomes the maximum and in-phase with the superimposed low frequency signal.

Abstract: An optical transmitter has an optical modulator having Mach-Zehnder interferometers, modulator drivers configured to drive the optical modulator by a drive signal, a low frequency generator configured to generated a low frequency signal that changes a ratio of a driving amplitude with respect to a half-wave voltage of the optical modulator, a photodetector configured to detect a portion of output light of the optical modulator, a detector configured to detect a low frequency component contained in a detected signal from the photodetector using the low frequency signal, and a bias voltage controller configured to control a bias voltage for the optical modulator such that the detected low frequency component becomes the maximum and in-phase with the superimposed low frequency signal.