Optical relay apparatus, optical transmission system, and optical relay method

Patent metadata

Field	Value
Publication number	US-12574120-B2
Application number	US-202118277732-A
Country	US
Kind code	B2
Filing date	Feb 26, 2021
Priority date	Feb 26, 2021
Publication date	Mar 10, 2026
Grant date	Mar 10, 2026

Abstract

An optical transceiver ( 101 ) of an optical relay apparatus includes: a coherent reception front-end unit ( 110 ) that coherently detects an input optical signal to be input, based on local oscillation light, and outputs the coherently detected first analog electric signal; a coherent transmission front-end unit ( 120 ) that coherently modulates a second analog electric signal acquired by turning around the first analog electric signal, based on transmission light, and outputs the coherently modulated output optical signal; and an analog compensation unit ( 130 ) that performs analog signal processing on the first analog electric signal in such a way as to compensate for signal quality according to a signal characteristic between an input of the coherent reception front-end unit ( 110 ) and an output of the coherent transmission front-end unit ( 120 ), and thereby generates the second analog electric signal.

First claim

What is claimed is:

1 . An optical relay apparatus comprising:
a coherent optical reception front-end unit configured to coherently detect an input optical signal to be input, based on local oscillation light, and to output the coherently detected first analog electric signal; a coherent optical transmission front-end unit configured to coherently modulate a second analog electric signal acquired by turning around the first analog electric signal, based on transmission light, and to output the coherently modulated output optical signal; and an analog compensator configured to perform analog signal processing on the first analog electric signal in such a way as to compensate for signal quality according to a signal characteristic between an input of the coherent optical reception front-end unit and an output of the coherent optical transmission front-end unit, and thereby generate the second analog electric signal, wherein the analog compensator comprises:
an analog signal processor configured to perform the analog signal processing;
a monitor configured to monitor a signal characteristic of any of the input optical signal, the first analog electric signal, the second analog electric signal, and the output optical signal; and
a controller configured to control an operation of the analog signal processing, based on a result of the monitoring.

2 . The optical relay apparatus according to claim 1 , wherein the signal characteristic comprises a characteristic of a polarization signal or a characteristic of a complex signal.

3 . The optical relay apparatus according to claim 1 , wherein the signal quality compensation comprises any of band compensation, frequency offset compensation, skew compensation, and amplitude compensation.

4 . The optical relay apparatus according to claim 1 , wherein:
the monitor is configured to monitor a frequency characteristic of the second analog electric signal, and the controller is configured to control output power of each band in the analog signal processing, based on the monitored frequency characteristic.

5 . The optical relay apparatus according to claim 4 , wherein:
the monitor is configured to monitor power of a first band and power of a second band in the second analog electric signal, and the controller is configured to control output power of the first band or the second band of the analog signal processing in such a way that the power of the first band and the power of the second band become equal.

6 . The optical relay apparatus according to claim 1 , wherein:
the monitor is configured to monitor a frequency offset of the local oscillation light by the first analog electric signal or the input optical signal, and the controller is configured to control a frequency of the local oscillation light, based on the monitored frequency offset.

7 . The optical relay apparatus according to claim 6 , wherein:
the monitor is configured to monitor bilateral asymmetry with respect to a center frequency of a frequency spectrum of the first analog electric signal, and the controller is configured to control a frequency of the local oscillation light in such a way that the frequency spectrum is bilaterally symmetrical with respect to a center frequency.

8 . The optical relay apparatus according to claim 7 , wherein the monitor comprises:
an AD convertor configured to convert the first analog electric signal into a digital signal; a complex signal generator configured to generate a complex signal from the converted digital signal; a FFT processor configured to perform FFT processing on the generated complex signal; and an asymmetry monitor configured to monitor asymmetry of a frequency spectrum acquired by the FFT processing.

9 . The optical relay apparatus according to claim 7 , wherein the monitor comprises:
a power monitor configured to monitor power of each band of the first analog electric signal; a spectrum generator configured to generate a frequency spectrum, based on the monitored power; and an asymmetry monitor configured to monitor asymmetry of the generated frequency spectrum.

10 . The optical relay apparatus according to claim 9 , wherein:
the monitor is configured to monitor asymmetry of the frequency spectrum, based on power of a first band and power of a second band in the first analog electric signal, and the controller is configured to control a frequency of the local oscillation light in such a way that the power of the first band and the power of the second band become equal.

11 . The optical relay apparatus according to claim 6 , wherein the monitor is configured to monitor a frequency offset of the local oscillation light, based on a spectrum of the input optical signal and a spectrum of the local oscillation light.

12 . The optical relay apparatus according to claim 11 , wherein the monitor comprises:
an input optical power monitor configured to monitor power of each band of the input optical signal; an input optical spectrum generator configured to generate a frequency spectrum, based on the monitored power of the input optical signal; a local oscillation light power monitor configured to monitor power of each band of the local oscillation light; a local oscillation light spectrum generator configured to generate a frequency spectrum, based on the monitored power of the local oscillation light; and a spectrum comparator configured to compare a frequency spectrum of the generated input optical signal with a frequency spectrum of local oscillation light, and monitoring a frequency offset.

13 . The optical relay apparatus according to claim 1 , wherein:
the monitor is configured to monitor an amplitude of the first analog electric signal, and the controller is configured to control an output amplitude in the analog signal processing, based on the monitored amplitude.

14 . The optical relay apparatus according to claim 1 , wherein:
the monitor is configured to monitor skew of the second analog electric signal or the output optical signal, and the controller is configured to control a delay of a signal in the analog signal processing, based on the monitored skew.

15 . The optical relay apparatus according to claim 14 , wherein:
the monitor is configured to monitor a constellation of the second analog electric signal, and the controller is configured to control a delay of a signal in the analog signal processing, based on a pattern of the constellation.

16 . The optical relay apparatus according to claim 14 , wherein:
the monitor is configured to monitor power of the output optical signal, and the controller is configured to control a delay of a signal in the analog signal processing, based on an amount of variation in the power.

17 . The optical relay apparatus according to claim 14 , further comprising a superimposer configured to superimpose a dither signal on the first analog electric signal being output from the coherent optical reception front-end unit,
wherein the monitor is configured to monitor skew, based on the dither signal extracted from the second analog electric signal.

18 . An optical transmission system comprising a plurality of optical relay apparatuses, wherein the plurality of optical relay apparatuses comprise:
a coherent optical reception front-end unit configured to coherently detect an input optical signal to be input from the optical relay apparatus in a preceding stage, based on local oscillation light, and to output the coherently detected first analog electric signal; a coherent optical trans

Assignees

• Nec Corp

Inventors

• Noguchi Hidemi

Classifications

• H04B10/6162

  Compensation of polarization related effects, e.g., PMD, PDL · CPC title

• H04B10/40

  Transceivers · CPC title

• H04B10/2507

  for the reduction or elimination of distortion or dispersion · CPC title

• H04B10/29

  Repeaters · CPC title

• H04B10/532 Primary

  Polarisation modulation · CPC title