Optical network device and method for monitoring transmission line

Patent metadata

Field	Value
Publication number	US-11742978-B2
Application number	US-202117554096-A
Country	US
Kind code	B2
Filing date	Dec 17, 2021
Priority date	Dec 25, 2020
Publication date	Aug 29, 2023
Grant date	Aug 29, 2023

Abstract

An optical network device includes a receiver that receives a polarization multiplexed optical signal and a processor. The processor separates an electric field information signal indicating the polarization multiplexed optical signal into first and second polarization components orthogonal to each other, generates third and fourth polarization components by controlling the first and second polarization components, calculates an evaluation value corresponding to a power of the third or fourth polarization component for each of a plurality of positions on a transmission line, calculates a variation in the evaluation value for a control amount for each of the plurality of positions, and decides whether a first position is a position to be detected based on a result of comparing a variation in an evaluation value for the first position with a variation in an evaluation value for a second position adjacent to the first position.

First claim

What is claimed is:

1. An optical network device comprising:
a receiver configured to receive a polarization multiplexed optical signal transmitted from a transmitter node; and
a processor configured to
separate an electric-field-information signal indicating an electric field of the polarization multiplexed optical signal into a first polarization component and a second polarization component orthogonal to each other,
generate a third polarization component and a fourth polarization component orthogonal to each other by controlling the first polarization component and the second polarization component in a coordinate system indicating a first polarization direction and a second polarization direction orthogonal to each other,
calculate an evaluation value corresponding to at least either a power of the third polarization component or a power of the fourth polarization component for each of a plurality of positions on an optical transmission line between the transmitter node and the optical network device,
calculate, for each of the plurality of positions, a variation in the evaluation value that is associated with a control amount in the controlling, and
decide whether a first position among the plurality of positions is a position to be detected based on a result of comparing a variation in an evaluation value calculated for the first position with a variation in an evaluation value calculated for a second position adjacent to the first position among the plurality of positions.

2. The optical network device according to claim 1 , wherein
the processor generates the third polarization component and the fourth polarization component by rotating the first polarization component and the second polarization component in the coordinate system, and
the processor calculates, for each of the plurality of positions, a variation in the evaluation value that is associated with a rotation amount in the rotating.

3. The optical network device according to claim 1 , wherein
the second position is adjacent to, and located on a transmitter-node side of, the first position, and
the processor decides that the first position is a position to be detected when the variation in the evaluation value calculated for the first position is larger than the variation in the evaluation value calculated for the second position.

4. The optical network device according to claim 1 , wherein
the variation in the evaluation value is a difference between a maximum value and a minimum value of the evaluation value obtained when the first polarization component and the second polarization component are rotated in the coordinate system.

5. The optical network device according to claim 1 , wherein
the processor outputs information indicating the first position when a difference between the variation in the evaluation value calculated for the first position and the variation in the evaluation value calculated for the second position is larger than a specified threshold.

6. The optical network device according to claim 1 , wherein
the processor
compensates for a first chromatic dispersion in a chromatic dispersion of the transmission line in the electric-field-information signal so as to generate a first compensated signal,
compensates for a nonlinear distortion of the transmission line in the first compensated signal so as to generate a second compensated signal,
compensates for a remaining chromatic dispersion in the chromatic dispersion of the transmission line in the second compensated signal so as to generate a third compensated signal,
calculates an evaluation value corresponding to a combination of the first chromatic dispersion and the remaining chromatic dispersion based on the third compensated signal, and
calculates evaluation values for the plurality of positions on the transmission line by calculating the evaluation values while changing an amount of the first chromatic dispersion.

7. The optical network device according to claim 6 , wherein
the evaluation value indicates a correlation between a reference signal indicating the electric field of the polarization multiplexed optical signal in the transmitter node and the third compensated signal.

8. The optical network device according to claim 7 , wherein
the processor controls a polarization of the reference signal in the coordinate system by a control amount for generating the third polarization component and the fourth polarization component from the first polarization component and the second polarization component, and
the evaluation value indicates a correlation between a reference signal on which the polarization is controlled and the third compensated signal.

9. The optical network device according to claim 1 , wherein
the processor performs, in parallel, a plurality of rotational processing operations for rotating the first polarization component and the second polarization component by different rotation amounts in the coordinate system, and
the processor calculates evaluation values corresponding to results of the plurality of rotational processing operations.

10. The optical network device according to claim 1 , wherein
the receiver is a coherent receiver that generates an electric-field-information signal indicating the electric field of the polarization multiplexed optical signal,
the processor
generates a second electric-field-information signal for which chromatic dispersion of the optical transmission line has been compensated for, by correcting the electric-field-information signal generated by the coherent receiver,
extracts the first polarization component and the second polarization component from the second electric-field-information signal, and
recovers transmission data based on the first polarization component and the second polarization component.

11. The optical network device according to claim 1 , wherein
the receiver is a coherent receiver that generates an electric-field-information signal indicating the electric field of the polarization multiplexed optical signal,
the processor
generates a second electric-field-information signal for which chromatic dispersion of the optical transmission line has been compensated for, by correcting the electric-field-information signal generated by the coherent receiver,
extracts the first polarization component and the second polarization component from the second electric-field-information signal, and
generates a third electric-field-information signal for which residual dispersion has been compensated for, by adaptively correcting the second electric-field-information signal, and
recovers transmission data based on the third electric-field-information signal.

12. The optical network device according to claim 1 , wherein
the receiver is a coherent receiver that generates an electric-field-information signal indicating the electric field of the polarization multiplexed optical signal,
the processor
extracts the first polarization component and the second polarization component from the electric-field-information signal generated by the coherent receiver,
generates a second electric-field-information signal for which chromatic dispersion of the optical transmission line has been compensated for, by correcting the electric-field-information signal generated by the coherent receiver,
generates a third electric-field-information signal for which residual dispersion has been compensated for, by adaptively correcting the second electric-field-information signal, and
recovers transmission data based on the third electric-field-information signal.

13. The optical network device according to claim 1 , wherein

Assignees

• Fujitsu Ltd

Inventors

• Tajima Kazuyuki
• Tanimura Takahito
• Yoshida Setsuo
• Katayama Eri
• Sugitani Kiichi

Classifications

• H04J14/06 Primary

  Polarisation multiplex systems · CPC title

• H04B10/2513

  due to chromatic dispersion · CPC title

• H04B10/2572

  due to forms of polarisation-dependent distortion other than PMD · CPC title

• H04B10/07951

  Monitoring or measuring chromatic dispersion or PMD · CPC title

• H04B10/6162

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