| 摘要 |
An optical transmitter includes an optical modulator with a first waveguide and a second waveguide to modulate carrier light using a driving signal with 2*n intensity levels (n is an integer 1 or greater) at each of the waveguides; and a phase shifter to cause a phase difference between a first optical signal and a second optical signal output from the first waveguide and the second waveguide, respectively. A photodetector converts a portion of a multilevel optical modulation signal acquired by combining the first optical signal and the second optical signals into an electrical signal. A monitor detects a change in an alternating current component in the detected modulation signal. A controller controls at least one of a first bias voltage and a second bias voltage being supplied to the first waveguide and the second waveguide, respectively, so as to increase the power value of the alternating current component. |
