# US 11,309,971 B2 · Controller and control method

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- Number: US 11,309,971 B2
- Document ID: US11309971B2
- Status: Granted
- Kind: B2
- Application number: 17/135,593
- Filed: 2020-12-28
- Published: 2021-08-12
- Granted: 2022-04-19
- Earliest claimed: 2020-02-07
- Assignees: Fujitsu Optical Components Limited
- Applicants: Fujitsu Optical Components Limited
- Inventors: Tetsuji Yamabana; Tsuyoshi Morishita
- Web page: https://patentgrep.com/patent/US11309971B2

## CPC

- H04B 10/50575: {to control the modulator DC bias}
- H04B 10/50595: {to control the modulator DC bias}
- H04B 10/5561: {Digital phase modulation}
- H04B 10/564: Power control
- H04B: TRANSMISSION

## Abstract

Controller and control method are provided. In particular, a controller is disclosed as being configured to hold intensities of a monitor signal, which changes according to an output from a region in a device, before and after altering a state of a portion in the region and control the state of the portion based on a difference between the held intensities.

## Claims

### Claim 1

A controller for controlling a device in which an output from a region thereof including a first portion changes according to a first state of the first portion, the controller comprising:
a first hold unit that performs first sample-and-hold processing that includes changing a first output thereof according to an intensity of a monitor signal inputted thereto and thereafter holding the changed first output, the monitor signal changing according to the output;
a second hold unit that performs second sample-and-hold processing that includes changing a second output thereof according to an intensity of the monitor signal inputted thereto and thereafter holding the changed second output, the second hold unit differing from the first hold unit; and
a control unit that causes the first hold unit to perform the first sample-and-hold processing while holding the first state of the first portion constant and alters the first state of the first portion after the first sample-and-hold processing, then causes the second hold unit to perform the second sample-and-hold processing while holding the altered first state of the first portion, and furthermore controls the first state of the first portion based on a difference, between a first intensity of the first output held by the first hold unit and a second intensity of the second output held by the second hold unit, obtained by subtracting one of the first and second intensities from another thereof.

### Claim 2 (depends on 1)

The controller according to claim 1, wherein the control unit repeats processing thereof so that an average value for an intensity of the output before the altering and an intensity of the output after the altering approaches a target value for an intensity of the output.

### Claim 3 (depends on 1)

The controller according to claim 1, wherein
the region includes a second portion that differs from the first portion,
the output from the region further changes according to a state of the second portion,
the altering is processing in which the control unit alters a second state of the second portion together with the first state of the first portion so that a change in the output between before and after the altering of the first state of the first portion is magnified, and
the control unit controls the first state of the first portion and the second state of the second portion based on the difference.

### Claim 4 (depends on 3)

The controller according to claim 3, wherein the region of the device includes:
a splitter configured to split inputted light into a first split light and a second split light;
a first optical waveguide configured to modulate a phase of the first split light;
a second optical waveguide configured to modulate a phase of the second split light; and
a combiner configured to combine the modulated first split light and the modulated second split light and output from the region light generated by the combining, wherein
the first portion includes a heater configured to heat the first optical waveguide, and
the second portion includes a heater configured to heat the second optical waveguide.

### Claim 5

A method for controlling a device in which an output from a region thereof including a first portion changes according to a first state of the first portion, the method comprising:
generating a first signal that changes according to an intensity of the output while holding the first state of the first portion constant, and then holding the generated first signal;
thereafter, altering the first state of the first portion;
generating a second signal that changes according to an intensity of the output while holding the altered first state of the first portion constant, and then holding the generated second signal; and
controlling the first state of the first portion based on a difference, between a first intensity of the held first signal and a second intensity of the held second signal, obtained by subtracting one of the first and second intensities from another thereof.