Patent ID: 11888526
Assignee: FUJITSU LIMITED
Field: Optics (Instruments)
Classification: CPC H  G | IPC G  H

Claim 8:
9. A method of controlling a bias voltage of an electro-optic modulator, comprising:
superimposing a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency onto the bias voltage of the electro-optic modulator in a time sharing manner;
monitoring an output light of the electro-optic modulator;
calculating a first control error based on a first component oscillating at the first frequency, and a second control error based on a second component oscillating at the second frequency from a monitoring result; and
determining a control value for controlling the bias voltage using the first control error and the second control error,
wherein the monitoring of the output light of the electro-optic modulator includes extracting the first component from the output light of the electro-optic modulator by a first filter, and extracting the second component from the output light of the electro-optic modulator by a second filter, and
switching between the first dither signal and the second dither signal is synchronized with switching between the first filter and the second filter.