Transmission apparatus, transmission system, and method of controlling average optical input power

1. A transmission apparatus, comprising:

an amplifier controller configured to determine a target value for an average optical input power of a transmitting amplifier in a transmitting-side apparatus of the transmission apparatus, based on an index based on a quality of transmission from an output of the transmitting amplifier to a receiving amplifier in a receiving-side apparatus of another transmission apparatus; and

a pre-emphasis controller configured to determine amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the receiving amplifier.

2. The transmission apparatus according to claim 1 ,

wherein the amplifier controller calculates an amount of tilt based on the per-wavelength reception optical powers at the receiving amplifier, and when the amount of tilt is larger than a present pre-emphasis controllable amount, the amplifier controller sets the target value to a smaller value than a present average optical input power of the transmitting amplifier.

3. The transmission apparatus according to claim 1 , further comprising:

an amplified spontaneous emission (ASE) calculator configured to calculate a cumulative ASE from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus; and

an optical signal-to-noise ratio (OSNR) calculator configured to calculate an OSNR from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus, based on the cumulative ASE,

wherein the amplifier controller uses the OSNR as the index.

4. The transmission apparatus according to claim 3 ,

wherein each of the transmitting-side apparatus of the transmission apparatus, the receiving-side apparatus of the another transmission apparatus, and a relay apparatus placed therebetween adds an ASE calculated by the each apparatus to an ASE received from a corresponding upstream apparatus and transfers a resulting ASE to a downstream apparatus, and the ASE calculator uses, as the cumulative ASE, an ASE transferred from the receiving-side apparatus.

5. The transmission apparatus according to claim 3 ,

wherein each of the transmitting-side apparatus of the transmission apparatus, the receiving-side apparatus of the another transmission apparatus, and a relay apparatus placed therebetween adds an ASE calculated by the each apparatus to an ASE received from a corresponding downstream apparatus and transfers a resulting ASE to a corresponding upstream apparatus, and the ASE calculator uses, as the cumulative ASE, an ASE transferred from an upstream apparatus immediately preceding the transmission apparatus.

6. The transmission apparatus according to claim 3 ,

wherein a network monitoring system adds ASEs calculated by the transmission apparatus, the receiving-side apparatus, and a relay apparatus placed therebetween and reports a resulting ASE to the ASE calculator, and the ASE calculator uses, as the cumulative ASE, the ASE reported from the network monitoring system.

7. The transmission apparatus according to claim 1 , further comprising a span-loss calculator configured to calculate a total span loss by adding span losses from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus,

wherein the amplifier controller uses the total span loss as the index.

8. A transmission system, comprising:

a transmitting-side apparatus, a receiving-side apparatus, and one or more relay apparatuses placed therebetween, the receiving-side apparatus monitoring per-wavelength reception optical powers at a receiving amplifier in the receiving-side apparatus and reporting the per-wavelength reception optical powers to the transmitting-side apparatus, and

the transmitting-side apparatus including:

an amplifier controller configured to determine a target value for an average optical input power of a transmitting amplifier, based on an index based on a quality of transmission from an output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus; and

a pre-emphasis controller configured to determine amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the receiving amplifier.

9. The transmission system according to claim 8 , wherein

the amplifier controller calculates an amount of tilt based on the per-wavelength reception optical powers at the receiving amplifier, and when the amount of tilt is larger than a present pre-emphasis controllable amount, the amplifier controller sets the target value to a smaller value than a present average optical input power of the transmitting amplifier.

10. The transmission system according to claim 8 , further comprising:

an amplified spontaneous emission (ASE) calculator configured to calculate a cumulative ASE from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus; and

an optical signal-to-noise ratio (OSNR) calculator configured to calculate an OSNR from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus, based on the cumulative ASE,

wherein the amplifier controller uses the OSNR as the index.

11. The transmission system according to claim 10 , wherein

each of the transmitting-side apparatus, the receiving-side apparatus, and the relay apparatus adds an ASE obtained by the each apparatus to an ASE received from a corresponding upstream apparatus and transfers a resulting ASE to a corresponding downstream apparatus, and the transmitting-side apparatus uses, as the cumulative ASE, an ASE transferred from the receiving-side apparatus.

12. The transmission system according to claim 10 , wherein

each of the transmitting-side apparatus, the receiving-side apparatus, and the relay apparatus adds an ASE obtained by the each apparatus to an ASE received from a corresponding downstream apparatus and transfers a resulting ASE to a corresponding upstream apparatus, and the transmitting-side apparatus uses, as the cumulative ASE, an ASE transferred from an upstream apparatus immediately preceding the transmitting-side apparatus.

13. The transmission system according to claim 10 , further comprising a network monitoring system, wherein

the transmission apparatus, the receiving-side apparatus, and the relay apparatus reports ASEs calculated by the respective apparatuses to the network monitoring system,

the network monitoring system adds the reported ASEs and reports a resulting ASE to the ASE calculator in the transmitting-side apparatus, and

the ASE calculator uses, as the cumulative ASE, the ASE reported from the network monitoring system.

14. The transmission system according to claim 8 , wherein

the transmitting-side apparatus further comprises a span-loss calculator configured to calculate a total span loss by adding span losses from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus, and

the amplifier controller uses the total span loss as the index.

15. A method of controlling average optical input power of a transmitting amplifier in a transmission apparatus, the method comprising:

determining, by an amplifier controller in the transmission apparatus, a target value for an average optical input power of the transmitting amplifier, based on an index based on a quality of transmission from an output of the transmitting amplifier to a receiving amplifier in a receiving-side apparatus; and

determining amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the receiving amplifier.

16. The method according to claim 15 , wherein,

in the determining the target value, the amplifier controller sets the target value to a smaller value than a present average optical input power, as the quality of transmission indicated by the index decreases.

17. The method according to claim 15 , wherein

an amplified spontaneous emission (ASE) calculator in the transmission apparatus calculates a cumulative ASE from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus;

an optical signal-to-noise ratio (OSNR) calculator in the transmission apparatus calculates an OSNR from the output of the transmitting amplifier to the receiving amplifier in the receiving-side apparatus, based on the cumulative ASE; and

the amplifier controller uses the OSNR as the index.

18. The method according to claim 17 , wherein

each of the transmission apparatus, the receiving-side apparatus, and a relay apparatus placed therebetween adds an ASE obtained by the each apparatus to an ASE received from a corresponding upstream apparatus and transfers a resulting ASE to a corresponding downstream apparatus, and

the ASE calculator uses, as the cumulative ASE, an ASE transferred from the receiving-side apparatus.

19. The method according to claim 17 , wherein

each of the transmission apparatus, the receiving-side apparatus, and a relay apparatus placed therebetween adds an ASE obtained by the each apparatus to an ASE received from a corresponding downstream apparatus and transfers a resulting ASE to a corresponding upstream apparatus; and

the ASE calculator uses, as the cumulative ASE, an ASE transferred from an upstream apparatus immediately preceding the transmission apparatus.

20. The method according to claim 17 , wherein

a network monitoring system adds ASEs calculated by the transmission apparatus, the receiving-side apparatus, and a relay apparatus placed therebetween and reports a resulting ASE to the ASE calculator; and

the ASE calculator uses, as the cumulative ASE, the ASE reported from the network monitoring system.