Optical transmitter and method of controlling optical modulator
AssigneeFujitsu Optical Components Limited
InventorHiroshi Nishimoto
Life of this patent
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Abstract
An optical transmitter has an optical modulator with a Mach-Zehnder interferometer, a pilot signal generator configured to generate a pilot signal to be superimposed on a drive signal for driving the optical modulator or on a substrate bias voltage applied to the optical modulator, and a controller configured to detect a ratio between a pilot component and a direct current component contained in a light output from the optical modulator and control at least one of an amplitude of the drive signal and a level of the substrate bias voltage such that the ratio becomes a constant value.
Claims7
An optical transmitter comprising:
- an optical modulator with a Mach-Zehnder interferometer,
- a pilot signal generator configured to generate a pilot signal to be superimposed on a drive signal for driving the optical modulator or on a substrate bias voltage applied to the optical modulator,
- a monitor circuit that detects a ratio between a pilot component and a direct current component contained in a light output from the optical modulator;
- and
- a processor that controls at least one of an amplitude of the drive signal for driving the optical modulator and a level of the substrate bias voltage applied to the optical modulator such that the ratio becomes a constant value,
- wherein the ratio between the pilot component and the direct current component is maintained constant so as to achieve a predetermined optical phase modulation depth of a main signal output from the optical modulator, the ratio being determined according to a modulation scheme of the optical transmitter.
A method of controlling an optical modulator, comprising:
- superimposing a pilot signal onto a drive signal for driving an optical modulator with a Mach-Zehnder interferometer or onto a substrate bias voltage applied to the optical modulator;
- detecting a ratio between a pilot component and a direct current component contained in a light output from the optical modulator;
- and
- controlling an amplitude of the drive signal or a level of the substrate bias voltage such that the ratio becomes a constant value,
- wherein the ratio between the pilot component and the direct current component is maintained constant so as to achieve a predetermined optical phase modulation depth of a main signal output from the optical modulator, the ratio being determined according to a modulation scheme of the optical transmitter.
Dependencies are inferred from the claim text.