Patent ID: 9014572
Filing Date: 2015-04-21
Classification: H04B

Abstract:
1. An optical transmitter comprising: an optical modulator including a first waveguide and a second waveguide and configured to modulate carrier light with a modulation driving signal having 2*n intensity levels (where n is an integer 1 or greater) at each of the first and second waveguides; a phase shifter configured to cause a predetermined phase difference between a first optical signal output from the first waveguide and a second optical signal output from the second waveguide; a photodetector configured to detect a portion of a multilevel optical modulation signal acquired by combining the first optical signal and the second optical signal having the phase difference and perform optical-to-electrical conversion on the detected modulation signal; a monitor configured to detect an integrated power spectrum of an alternating current component in the detected modulation signal; and a controller configured to control at least one of a first bias voltage being supplied to the first waveguide and a second bias voltage being supplied to the second waveguide, independently from a third bias voltage being supplied to the phase shifter, so as to increase a power value of the integrated power spectrum of the alternating current component.