Optical signal quality monitoring apparatus, optical signal quality monitoring method and optical repeater

1. An optical signal quality monitoring apparatus comprising:

a bandpass filter configured to perform a filtering operation to thereby output a noise power of light input to the optical signal quality monitoring apparatus;

an optical power monitor configured to measure an optical power of the light input to the optical signal quality monitoring apparatus; and

an optical signal-to-noise ratio (OSNR) controller configured to

calculate a plurality of optical signal-to-noise ratios, based on the optical power measured by the optical power monitor and the noise power output by the bandpass filter, by using a relational expression and a plurality of calibration coefficients used in the relational expression, wherein the relational expression represents a relationship among an optical signal intensity, a noise intensity, and an optical signal-to-noise ratio,

select one optical signal-to-noise ratio from the plurality of optical signal-to-noise ratios, based on a magnitude relationship of the plurality of optical signal-to-noise ratios, and

output the selected optical signal-to-noise ratio as the optical signal-to-noise ratio of the light input to the optical signal quality monitoring apparatus.

2. The optical signal quality monitoring apparatus according to claim 1 , wherein

a range for measuring the optical power of the light input to the optical signal quality monitoring apparatus and the noise power in the light input to the optical signal quality monitoring apparatus is divided into a plurality of areas, and

the OSNR controller is further configured to

calculate the magnitude relationship of the plurality of optical signal-to-noise ratios for each of the plurality of areas,

store the calculated magnitude relationship of the plurality of optical signal-to-noise ratios for each of the plurality of areas in a table, and

select the one optical signal-to-noise ratio with reference to the table.

3. The optical signal quality monitoring apparatus according to claim 2 , wherein the OSNR controller is further configured to:

optimize the plurality of calibration coefficients so that differences between reference optical signal-to-noise ratios and the calculated plurality of optical signal-to-noise ratios in the plurality of areas are minimized.

4. The optical signal quality monitoring apparatus according to claim 2 , wherein the OSNR controller is further configured to:

optimize the table such that the OSNR controller selects, in a respective area of the plurality of areas, a smallest or largest optical signal-to-noise ratio among the plurality of optical signal-to-noise ratios in the respective area as the one optical signal-to-noise ratio.

5. The optical signal quality monitoring apparatus according to claim 2 ,

wherein the table includes area information to specify the plurality of areas, and

wherein the OSNR controller selects the one optical signal-to-noise ratio, based on the area information and the magnitude relationship of the plurality of optical signal-to-noise ratios for each of the plurality of areas stored in the table.

6. The optical signal quality monitoring apparatus according to claim 1 , wherein the optical signal quality monitoring apparatus is included in a node of an optical network.

7. The optical signal quality monitoring apparatus according to claim 6 , wherein the node is an optical repeater.

8. The optical signal quality monitoring apparatus according to claim 6 , wherein the selected optical signal-to-noise-ratio output by the OSNR controller is transmitted by the node to a network control apparatus.

9. An optical signal quality monitoring method to calculate an optical signal-to-noise ratio of input light, the method comprising:

storing a relational expression representing a relationship among an optical signal intensity, a noise intensity, and an optical signal-to-noise ratio, and a plurality of calibration coefficients used in the relational expression;

performing, by a bandpass filter, a filtering operation to thereby output a noise power of the input light;

measuring, by an optical power monitor, an optical power of input light;

calculating, by an optical signal-to-noise ratio (OSNR) controller, a plurality of optical signal-to-noise ratios, based on the optical power measured by the optical power monitor and the noise power output by the bandpass filter, by using the stored relational expression and the stored plurality of calibration coefficients;

selecting, by the OSNR controller, one optical signal-to-noise ratio from the plurality of optical signal-to-noise ratios, based on a magnitude relationship of the plurality of optical signal-to-noise ratios; and

outputting, by the OSNR controller, the selected optical signal-to-noise ratio as the optical signal-to-noise ratio of the input light.

10. The optical signal quality monitoring method according to claim 9 , wherein a range for measuring the optical power of the input light and the noise power in the input light is divided into a plurality of areas, and the method further comprising:

determining, by the OSNR controller, one calibration coefficient for each area of the plurality of areas, so as to obtain the plurality of calibration coefficients, and so that differences between reference optical signal-to-noise ratios and the calculated plurality of optical signal-to-noise ratios in the plurality of areas are minimized.

11. The optical signal quality monitoring method according to claim 10 , further comprising:

calculating the magnitude relationship of the plurality of optical signal-to-noise ratios for each of the plurality of areas; and

storing, in a table, the calculated magnitude relationship of the plurality of optical signal-to-noise ratios for each area of the plurality of areas,

wherein the OSNR controller selects the one optical signal-to-noise ratio based on the table.

12. The optical signal quality monitoring method according to claim 9 , wherein the bandpass filter, the optical power monitor and the OSNR controller are included in a node of an optical network, and the method further comprises:

transmitting, by the node, the selected optical signal-to-noise-ratio output by the OSNR controller to a network control apparatus.

13. The optical signal quality monitoring method according to claim 12 , wherein the node is an optical repeater.

14. An optical signal quality monitoring apparatus comprising:

means for measuring an optical power of light input to the apparatus and a noise power in the light input to the apparatus;

means for calculating a plurality of optical signal-to-noise ratios, based on the measured optical power and the measured noise power, by using a relational expression and a plurality of calibration coefficients used in the relational expression, wherein the relational expression represents a relationship among an optical signal intensity, a noise intensity, and an optical signal-to-noise ratio;

means for selecting one optical signal-to-noise ratio from the plurality of optical signal-to-noise ratios, based on a magnitude relationship of the plurality of optical signal-to-noise ratios, and for outputting the selected optical signal-to-noise ratio as the optical signal-to-noise ratio of the light input to the apparatus.