# US 11,121,778 B1 · Phase variation compensation device, phase variation compensation method and communication device

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- Number: US 11,121,778 B1
- Document ID: US11121778B1
- Status: Granted
- Kind: B1
- Application number: 17/255,156
- Filed: 2019-07-22
- Published: 2021-09-02
- Granted: 2021-09-14
- Earliest claimed: 2018-07-24
- Assignees: NTT Electronics Corporation; Nippon Telegraph and Telephone Corporation
- Applicants: NTT Electronics Corporation
- Inventors: Tomohiro Takamuku; Mitsuteru Yoshida; Tsutomu Takeya; Katsuichi Oyama; Hiroyuki Nouchi; Atsushi Suenaga
- Web page: https://patentgrep.com/patent/US11121778B1

## CPC

- H04B 10/6164: {Estimation or correction of the frequency offset between the received optical signal and the optical local oscillator}
- H04L 25/03885: {adaptive}
- H04B 10/612: {for optical signals modulated with a format different from binary or higher-order PSK [X-PSK], e.g. QAM, DPSK, FSK, MSK, ASK}
- H04B 10/6163: {Compensation of non-linear effects in the fiber optic link, e.g. self-phase modulation [SPM], cross-phase modulation [XPM], four wave mixing [FWM]}
- H04B 10/6165: {Estimation of the phase of the received optical signal, phase error estimation or phase error correction}
- H04L 25/03006: {Arrangements for removing intersymbol interference}
- H04L 27/066: {Carrier recovery circuits (H04L27/2271 takes precedence)}
- H04L 2025/03522: {Frequency domain}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A known pattern comparison type phase difference detection unit (12) detects a phase difference between a known pattern extracted from a received signal and a true value of the known pattern as a first phase difference. M indicates the number of modulation phases in a phase modulation method of the received signal. An M-th power type phase difference detection unit (13) removes a modulation component by raising the received signal to M-th power, and detects phase variation from a modulation phase point used for mapping on a transmission side, as a second phase difference. A phase compensation unit (11) compensates phase variation of the received signal based on an addition result of the first phase difference and the second phase difference.

## Claims

### Claim 1

A phase variation compensation device comprising:
first phase difference detection circuitry configured to detect a phase difference between a known pattern extracted from a received signal and a true value of the known pattern as a first phase difference;
second phase difference detection circuitry configured to remove a modulation component by raising the received signal to M-th power, and detect phase variation from a modulation phase point used for mapping on a transmission side, as a second phase difference, wherein M indicates the number of modulation phases in a phase modulation method of the received signal; and
phase compensation circuitry configured to compensate phase variation of the received signal based on an addition result of the first phase difference and the second phase difference.

### Claim 2 (depends on 1)

The phase variation compensation device according to claim 1, further comprising compensation circuitry configured to compensate phase variation of the received signal inputted to the second phase difference detection circuitry or the received signal raised to the M-th power, with a first phase difference.

### Claim 3 (depends on 1)

The phase variation compensation device according to claim 1, further comprising frequency offset compensation circuitry configured to compensate a frequency offset of the received signal based on the addition result before supplying the received signal to the first phase difference detection circuitry and the second phase difference detection circuitry.

### Claim 4 (depends on 1)

The phase variation compensation device according to claim 1, wherein the first phase difference detection circuitry includes:
known pattern timing detection circuitry configured to detect a timing of the known pattern from the received signal;
known pattern extraction circuitry configured to extract the known pattern from the received signal based on the timing;
a reference signal memory configured to store the true value; and
phase difference calculation circuitry configured to calculate a phase difference between the known pattern extracted from the received signal and the true value as the first phase difference.

### Claim 5 (depends on 4)

The phase variation compensation device according to claim 4, wherein the known pattern timing detection circuitry detects a timing of the known pattern from the received signal phase-compensated by the phase compensation circuitry, and
the known pattern extraction circuitry detects the known pattern from the received signal before being phase-compensated by the phase compensation circuitry, based on the timing.

### Claim 6 (depends on 1)

The phase variation compensation device according to claim 1, wherein by performing linear interpolation using the phase difference between the known pattern extracted from the received signal and the true value and a phase difference between a next known pattern and a true value of the next known pattern, the first phase difference detection circuitry calculates a phase difference for each symbol between the known pattern and the next known pattern as the first phase difference.

### Claim 7

A communication device comprising a phase variation compensation device comprising:
first phase difference detection circuitry configured to detect a phase difference between a known pattern extracted from a received signal and a true value of the known pattern as a first phase difference;
second phase difference detection circuitry configured to remove a modulation component by raising the received signal to the M-th power, and detect phase variation from a modulation phase point used for mapping on a transmission side, as a second phase difference, wherein M indicates the number of modulation phases in a phase modulation method of the received signal; and
phase compensation circuitry configured to compensate phase variation of the received signal based on an addition result of the first phase difference and the second phase difference.

### Claim 8

A phase variation compensation method performed by a phase variation compensation device comprising:
detecting a phase difference between a known pattern extracted from a received signal and a true value of the known pattern as a first phase difference;
removing a modulation component by raising the received signal to M-th power, and detecting phase variation from a modulation phase point used for mapping on a transmission side, as a second phase difference, wherein M indicates the number of modulation phases in a phase modulation method of the received signal; and
compensating phase variation of the received signal based on an addition result of the first phase difference and the second phase difference.

### Claim 9 (depends on 8)

The phase variation compensation method according to claim 8, wherein when the phase variation compensation device is started, a timing of the known pattern is detected from the received signal whose phase variation is compensated based on only the second phase difference, and the known pattern is extracted from the received signal before being phase-compensated, based on the timing, and
after the first phase difference is detected from the known pattern extracted at startup of the phase variation compensation device, a timing of the known pattern is detected from the received signal whose phase variation is compensated based on the addition result of the first phase difference and the second phase difference, and the known pattern is extracted from the received signal before being phase-compensated, based on the timing.