Optical modulator, light source module, and optical modulation method

Abstract

The present invention provides an optical modulator, a light source module, and an optical modulation method that offer excellent responsiveness and stability, enabling high-speed and stable control of the output light of the optical modulator. [Solution] The optical modulator 101 according to the present invention comprises an optical modulation element 11 having a plurality of optical waveguides formed in a thin film made of a material having an electro-optic effect, electrodes arranged on the thin film and applying an electric field to the plurality of optical waveguides, a drive unit (drive circuit 120) that applies a modulation voltage to the electrodes, a bias application unit (bias application circuit 130) that applies a bias voltage to the electrodes, and a feedforward control unit (feedforward control circuit 150) that compensates for DC drift occurring in the plurality of optical waveguides, wherein the feedforward control unit changes the bias voltage output by the bias application unit over time based on a transfer function set in advance according to the characteristics of the DC drift.

Claims

1. An optical modulation element having multiple optical waveguides formed in a thin film made of a material having an electro-optic effect, An electrode disposed on the thin film and applying an electric field to the plurality of optical waveguides, A drive unit that applies a modulated voltage to the electrode, A bias application unit that applies a bias voltage to the electrode, The system includes a feedforward control unit that compensates for DC drift occurring in the plurality of optical waveguides, An optical modulator characterized in that the feedforward control unit changes the bias voltage output by the bias application unit over time based on a transfer function set in advance according to the characteristics of the DC drift.

2. The optical modulator according to claim 1, characterized in that the feedforward control unit monotonically increases the bias voltage over time.

3. The optical modulator according to claim 1 or 2, characterized in that the feedforward control unit, at the timing when the modulation voltage changes, returns the bias voltage to a predetermined value and then continues to monotonically increase the bias voltage.

4. The optical modulator according to claim 1 or 2, characterized in that the plurality of optical waveguides constitute a Mach-Zehnder type optical waveguide.

5. The aforementioned plurality of optical waveguides constitute a plurality of Mach-Zehnder type optical waveguides, The optical modulator according to claim 1 or 2, characterized in that each of the plurality of Mach-Zehnder type optical waveguides is provided with the feedforward control unit.

6. In each of the aforementioned multiple Mach-Zehnder type optical waveguides, visible light of a different wavelength is propagated. The optical modulator according to claim 5, characterized in that the feedforward control unit corresponding to each of the plurality of Mach-Zehnder type optical waveguides changes the bias voltage over time based on the transfer function set in advance according to each wavelength.

7. The optical modulator according to claim 4, characterized in that the Mach-Zehnder type optical waveguide comprises an input optical waveguide, a demultiplexer that branches the input optical waveguide, a first optical waveguide and a second optical waveguide extending parallel to each other from the demultiplexer, a combiner that couples the first optical waveguide and the second optical waveguide, and an output optical waveguide extending from the combiner.

8. The optical modulator according to claim 1 or 2, characterized in that the parameters of the transfer function are set based on measurement results in an actual optical modulator.

9. The optical modulator according to claim 1 or 2, characterized in that the parameters of the transfer function are set based on the analysis results of an equivalent circuit that models the optical modulator.

10. The optical modulator according to claim 1 or 2, A light source module characterized by comprising multiple light sources that each emit visible light of different wavelengths.

11. An optical modulation method for modulating light propagating through a plurality of optical waveguides, using an optical modulator comprising an optical modulation element having a plurality of optical waveguides formed in a thin film made of a material having an electro-optic effect, and electrodes for applying an electric field to the plurality of optical waveguides, wherein the optical modulation is performed using the plurality of optical waveguides. The process involves setting a transfer function corresponding to the characteristics of the DC drift generated in the plurality of optical waveguides, and calculating the parameters of the transfer function. A step of applying a modulation voltage and a bias voltage to the electrode to modulate the light propagating through the plurality of optical waveguides, A step of performing feedforward control to change the bias voltage over time based on the transfer function to compensate for DC drift occurring in the plurality of optical waveguides, A method for optical modulation characterized by having the following:

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