DELAY CONTROL CIRCUIT, OPTICAL TRANSMISSION APPARATUS, AND DELAY CONTROL METHOD

A delay control circuit includes a delay circuit configured to provide a predetermined delay to signals input to a plurality of electrode segments provided in series along one or both of two waveguides forming a Mach-Zehnder interferometer of an optical modulator, a control circuit configured to select two electrode segments from the plurality of electrode segments, and control a delay amount between the two electrode segments that are selected, a frequency filter configured to extract a predetermined frequency component from output light of the Mach-Zehnder interferometer, in a state where identical signals that vary at random are input to the two electrode segments, and a monitor configured to monitor a power of the extracted predetermined frequency component. The control circuit controls the delay amount between the two electrode segments based on a monitored result of the extracted predetermined frequency component.