OPTICAL TRANSMISSION DEVICE AND TRANSMISSION OPTICAL POWER CONTROL METHOD

1 . An optical transmission device comprising:

an optical transmission amplifier for each band configured to optically amplify signal light of the band of a plurality of different wavelength bands;

output level adjuster arranged at a post-stage of the optical transmission amplifier for each band, and configured to adjust an output of the optical transmission amplifier for each band and output the adjusted output to the transmission path;

a memory; and

a processor coupled to the memory and configured to make the output level adjuster for the each band to reduce a difference in a generalized signal to noise ratio (GSNR) between the bands.

2 . The optical transmission device according to claim 1 , wherein the output level adjuster is a variable optical attenuator.

3 . The optical transmission device according to claim 2 , wherein the plurality of different wavelength bands are a C-band and an L-band.

4 . The optical transmission device according to claim 3 , wherein the processor is configured to make an output level of the L-band higher than an output level of the C-band.

5 . The optical transmission device according to claim 4 , wherein the processor is configured to make the output level to change according to a span loss of the transmission path.

6 . The optical transmission device according to claim 5 , wherein the processor is configured to make the output level to reduce as the span loss decreases.

7 . The optical transmission device according to claim 6 ,

wherein target values of output levels of the C-band and the L-band are stored in the memory in advance, and

wherein the processor is configured to make the output levels to become to the target values.

8 . The optical transmission device according to claim 7 , wherein one of the target values and a target value of a difference between the output levels is a value according to the span loss.

9 . An optical transmission device comprising:

an optical transmission amplifier configured to optically amplify signal light of a band of different wavelength bands;

an output level adjuster arranged at a post-stage of the optical transmission amplifier for each band, and configured to adjust an output level of the optical transmission amplifier for each band and output the signal light of the adjusted output level to the transmission path;

a memory; and

a processor coupled to the memory and configured to make an output level adjuster for the each band to equalize a generalized signal to noise ratio (GSNR), based on a difference in generalized signal to noise ratios (GSNRs) generated between the outputs of the optical transmission amplifier for the each band.

10 . The optical transmission device according to claim 9 ,

wherein the each band includes one of a C-band and an L-band, and

wherein the processor is configured to make the output level adjuster of the L-band higher than an output level of the C-band, based on a noise figure of the optical transmission amplifier and a nonlinear noise for the each band.

11 . The optical transmission device according to claim 9 ,

wherein the processor is configured to:

calculate an average output level of the optical transmission amplifier different for the each band, based on the noise figure of the optical transmission amplifier and a nonlinear noise of the transmission path, and

determine a control target value to equalize the GSNR of the each band by using the average output level.

12 . The optical transmission device according to claim 10 ,

wherein a control target value for the each band is held in the memory in advance, the control target value corresponding to equalization of the GSNRs of the C-band and the L-band at a time of a transmission state of a maximum number of wavelengths, and

wherein the processor is configured to make the output level adjuster for the each band to adjust the output level, with reference to the control target value for the each band, which is held in the memory.

13 . The optical transmission device according to claim 12 ,

wherein the control target values for the each band of the optical transmission amplifier and the output level adjuster are held in the memory, the control target value corresponding to a span loss of the transmission path, and

wherein the processor is configured to make, based on the span loss, the output level adjuster to adjust the output level, with the control target value corresponding to the span loss, which is held in the memory.

14 . The optical transmission device according to claim 13 , wherein, the control target value for the each band of the output level adjuster causes the smaller the span loss of the transmission path, the lower the output level and optical attenuation.

15 . The optical transmission device according to claim 13 , wherein the processor is configured to acquire the span loss of the transmission path by a user input.

16 . The optical transmission device according to claim 13 , further comprising:

an optical power monitor configured to detect output power of each band, the optical power monitor that detects input power of each band being included in a reception side node,

wherein the processor is configured to acquire the span loss of the transmission path, based on the detected output power of the optical power monitor.

17 . The optical transmission device according to claim 9 , further comprising:

a wavelength selective switch configured to attenuate input power of the optical transmission amplifier for each band,

wherein the processor is configured to make the wavelength selective switch to attenuate the input power, and to control an amplifier gain tilt amount for a gain tilt of the optical transmission amplifier for each band.

18 . An transmission optical power control method of an optical transmission device including an optical transmission amplifier to optically amplify optical signal light of a band of a plurality of different wavelength bands, an output level adjuster to adjust an output of the optical transmission amplifier for each band and output the adjusted output to the transmission path, and a processor, the transmission optical power control method comprising:

making the output level adjuster for the each band to reduce a difference in a generalized signal to noise ratio (GSNR) between the bands, by the processor.