Optical communication apparatus and correcting method

1. An optical communication apparatus comprising:

a level detector that detects level information that discriminates a change in a multi-value level based on an input signal used in a multi-value amplitude modulation system;

an FIR filter that compensates a signal band of the input signal in accordance with tap coefficients of a plurality of multipliers;

a digital to analog converter that performs analog conversion on an output signal of the FIR filter;

a driver that outputs a driving signal in accordance with the output signal that has been subjected to analog conversion;

an optical modulator that performs optical conversion on the output signal in accordance with the driving signal of the driver; and

an adjustor that corrects, based on the level information detected in the level detector, the tap coefficient of each of the multipliers included in the FIR filter so as to compensate nonlinear static characteristics of the digital to analog converter, the driver, and the optical modulator.

2. The optical communication apparatus according to claim 1 , wherein

the optical modulator is an electro-absorption modulation laser (EML), and

the adjustor corrects the tap coefficient of each of the multipliers included in the FIR filter so as to compensate transmission distortion generated due to a bias voltage-vs-chirp characteristic of the EML.

3. The optical communication apparatus according to claim 1 , wherein

the optical modulator is a directly modulated laser (DML), and

the adjustor corrects the tap coefficient of each of the multipliers included in the FIR filter so as to compensate skew between levels generated due to an input current-vs-delay characteristic of the DML.

4. The optical communication apparatus according to claim 1 , wherein the level detector detects the level information that discriminates a signal logic indicating a change transition of the multi-value level of the input signal.

5. The optical communication apparatus according to claim 1 , wherein the level detector detects the level information that discriminates a level reached due to the change in the multi-value level of the input signal.

6. The optical communication apparatus according to claim 1 , further comprising:

a photodetector that performs photoelectric conversion on the input signal used in the multi-value amplitude modulation system; and

an analog to digital converter that performs digital conversion on an input signal that has been subjected to photoelectric conversion by the photodetector, wherein

the adjustor corrects the tap coefficient of each of the multipliers included in the FIR filter that compensates the signal band of the input signal that has been subjected to digital conversion and that is received from the analog to digital converter so as to compensate nonlinear static characteristics of the photodetector and the analog to digital converter.

7. A correcting method performed by an optical communication apparatus, the correcting method comprising:

detecting level information that discriminates a change in a multi-value level based on an input signal used in a multi-value amplitude modulation system;

compensating a signal band of the input signal in accordance with tap coefficients of a plurality of multipliers included in an FIR filter;

performing analog conversion on an output signal of the FIR filter;

outputting a driving signal in accordance with the output signal that has been subjected to analog conversion;

performing optical conversion on the output signal in accordance with the driving signal of the outputting; and

correcting the tap coefficient of each of the multipliers included in the FIR filter based on the detected level information so as to compensate nonlinear static characteristics of the performing analog conversion, the outputting, and the performing optical conversion.

8. An optical communication apparatus comprising:

a level detector that detects level information that discriminates a change in PAM-N symbol levels based on an input signal used in a N-level pulse amplitude modulation system, where N is any integer that is the nth power of 2;

an FIR filter that compensates a signal band of the input signal in accordance with tap coefficients of a plurality of multipliers;

a digital to analog converter that performs analog conversion on an output signal of the FIR filter;

a driver that outputs a driving signal in accordance with the output signal that has been subjected to analog conversion;

an optical modulator that performs optical conversion on the output signal in accordance with the driving signal of the driver; and

an adjustor that corrects, based on the level information detected in the level detector, the tap coefficient of each of the multipliers included in the FIR filter so as to compensate nonlinear static characteristics of the digital to analog converter, the driver, and the optical modulator.

9. A correcting method performed by an optical communication apparatus, the correcting method comprising:

detecting level information that discriminates a change in PAM-N symbol levels based on an input signal used in a N-level pulse amplitude modulation system, where N is any integer that is the nth power of 2;

compensating a signal band of the input signal in accordance with tap coefficients of a plurality of multipliers included in an FIR filter;

performing analog conversion on an output signal of the FIR filter;

outputting a driving signal in accordance with the output signal that has been subjected to analog conversion;

performing optical conversion on the output signal in accordance with the driving signal of the outputting; and

correcting the tap coefficient of each of the multipliers included in the FIR filter based on the detected level information so as to compensate nonlinear static characteristics of the performing analog conversion, the outputting, and the performing optical conversion.