Distortion compensator, optical receiver, distortion compensator and optical receiver controlling methods, and optical transmission system

1. A distortion compensator inputting an electric signal obtained by photoelectric-converting an optical signal received from an optical transmission line, comprising:

a plurality of distortion compensating sections, each having compensators configured to compensate for linear waveform distortion exerted on the optical signal; and

at least one of the compensators configured to alternately compensate for nonlinear waveform distortion exerted on the optical signal, which are cascade-connected with one another, where a signal outputted is subjected to linear and non-linear waveform distortion compensation.

2. The distortion compensator according to claim 1 , wherein

at least one of the linear distortion compensators compensates for chromatic dispersion of the optical signal.

3. The distortion compensator according to claim 1 , wherein

at least one of the non-linear distortion compensators compensates for phase modulation distortion exerted on the input electric signal based on an intensity of the received optical signal and information obtained by arithmetically operating information with respect to the intensity.

4. The distortion compensator according to claim 1 , wherein

at least one of the nonlinear distortion compensators inputs electric signals corresponding to a plurality of optical signals included in the optical signal to compensate for phase modulation distortion exerted on at least one of the plurality of signals based on the intensity of each of the plurality of signals.

5. The distortion compensator according to claim 1 , wherein

the plurality of distortion compensators compensate for waveform distortion induced by the optical transmission line in accordance with a given coefficient.

6. The distortion compensator according to claim 1 , wherein

the plurality of distortion compensators compensate for linear waveform distortion and nonlinear waveform distortion generated in a plurality of transmission spans of the optical transmission line.

7. The distortion compensator according to claim 1 , comprising:

a control section changing a parameter used in at least one of distortion compensating operations performed using the linear distortion compensators and the nonlinear distortion compensators based on information on residual distortion in a signal output from the distortion compensator.

8. An optical reception device, comprising:

a distortion compensator inputting an electric signal obtained by photoelectric-converting an optical signal received from an optical transmission line, and

wherein the distortion compensator includes a plurality of distortion compensators, at least one of the plurality of distortion compensators configured to compensate for linear waveform distortion exerted on the optical signal and alternatively compensate for nonlinear waveform distortion exerted on the optical signal, which are cascade-connected with one another, and

where a signal outputted is subjected to linear and non-linear waveform distortion compensation.

9. The optical reception device according to claim 8 , wherein

at least one of the linear distortion compensators compensates for chromatic dispersion of the optical signal.

10. The optical reception device according to claim 8 , wherein

at least one of the nonlinear distortion compensators compensates for phase modulation distortion exerted on the input signal based on an intensity of the input signal.

11. The optical reception device according to claim 8 , wherein

at least one of the nonlinear distortion compensators inputs electric signals corresponding to the plurality of optical signals included in the optical signal to compensate for the phase modulation distortion exerted on one of the plurality of signals based on the intensity of each of the plurality of signals.

12. The optical reception device according to claim 8 , wherein

each of the plurality of distortion compensators compensates for the waveform distortion induced by the optical transmission line in accordance with a given coefficient.

13. The optical reception device according to claim 8 , wherein

the plurality of distortion compensators compensate for linear waveform distortion and nonlinear waveform distortion generated in a plurality of transmission spans of the optical transmission line.

14. The optical reception device according to claim 8 , comprising:

a control section changing a parameter used in at least one of distortion compensating operations performed using the linear distortion compensators and the nonlinear distortion compensators based on information on residual distortion in a signal output from the distortion compensator.

15. A distortion compensator controlling method, comprising:

a distortion compensating operation including:

compensating for linear waveform distortion exerted on an optical signal; and

alternately compensating for nonlinear waveform distortion exerted on the optical signal, respectively based on an electric signal obtained by photoelectric-converting the optical signal received from an optical transmission line; and

executing the distortion compensating operation a plurality of times, where a signal outputted is subjected to linear and non-linear waveform distortion compensation.

16. An optical reception device controlling method,

an optical transmission system controlling a distortion compensator using the controlling method according to claim 15 .

17. A distortion compensator controlling method, comprising:

a distortion compensating operation including:

executing a linear distortion compensating operation compensating for linear waveform distortion exerted on an optical signal; and

alternately executing a nonlinear distortion compensating operation compensating for nonlinear waveform distortion exerted on the optical signal, respectively based on an electric signal obtained by photoelectric-converting the optical signal received from an optical transmission line and information obtained from an optical transmission line channel network control unit; and

executing the distortion compensating operation a plurality of times, where a signal outputted is subjected to linear and non-linear waveform distortion compensation.

18. An optical reception device controlling method, comprising:

compensating for linear waveform distortion exerted on an optical signal based on an electric signal obtained by photoelectric-converting the optical signal received from an optical transmission line;

alternately compensating for nonlinear waveform distortion exerted on the optical signal based on the electric signal; and

executing an operation of combining the linear waveform distortion compensating operation with the nonlinear waveform distortion compensating operation a plurality of times, where a signal outputted is subjected to linear and non-linear waveform distortion compensation.

19. An optical transmission system controlling an optical reception device using the controlling method according to claim 18 .

20. An optical reception device controlling method, comprising:

a distortion compensating operation including:

compensating for linear waveform distortion exerted on an optical signal; and

alternately compensating for nonlinear waveform distortion exerted on the optical signal, respectively based on an electric signal obtained by photoelectric-converting the optical signal received from an optical transmission line and information obtained from an optical transmission line network control unit; and

executing the distortion compensating operation a plurality of times, where a signal outputted is subjected to linear and non-linear waveform distortion compensation.