OPTICAL MODULATOR AND OPTICAL MODULATION CONTROL METHOD

摘要

An optical modulator includes: a modulator including an optical waveguide provided in a semiconductor substrate having an electro-optical effect and an electrode to apply an electric field depending on a bias voltage and a modulation signal to the optical waveguide; a driver circuit to generate a modulation signal in accordance with an input signal; a superimposer to superimpose a reference signal on the bias voltage, the reference signal having lower frequency than the modulation signal; and a controller to control a bias voltage in a direction orthogonal to a modulation direction of the modulator based on the frequency component of the reference signal extracted from a modulated optical signal generated by the modulator.

主权项

1. An optical modulator comprising:
a modulator including an optical waveguide provided in a semiconductor substrate having an electro-optical effect and an electrode to apply an electric field depending on a bias voltage and a modulation signal to the optical waveguide; a driver circuit configured to generate a modulation signal in accordance with an input signal; a superimposer configured to superimpose a reference signal on the bias voltage, the reference signal having lower frequency than the modulation signal; and a controller configured to control a bias voltage in an orthogonal direction orthogonal to a modulation direction of the modulator based on the frequency component of the reference signal extracted from a modulated optical signal generated by the modulator, wherein the optical waveguide includes first and second optical waveguides forming a Mach-Zehnder interferometer, the electrode includes first and second electrodes to apply an electric field to the first and second optical waveguides, respectively, the modulation signal and a first bias voltage are provided for the first electrode, a reversed signal of the modulation signal and a second bias voltage are provided for the second electrode, the modulator provided in the semiconductor substrate has a configuration in which an intensity of output light of the modulator changes by shifting the first bias voltage and the second bias voltage in the same direction, the controller controls the bias voltage in the orthogonal direction by shifting the first bias voltage and the second bias voltage in the same direction based on the frequency component of the reference signal extracted from the modulated optical signal generated by the modulator.