Optical transmission device, optical transmission system, and optical transmitting power control method

1. An optical transmission system that transmits a WDM (wavelength division multiplexed) signal from a first optical transmission device to a second optical transmission device via an optical fiber transmission line, the optical transmission system comprising:

a first optical channel monitor that detects optical power of each wavelength channel of the WDM signal in the first optical transmission device;

a second optical channel monitor that detects optical power of each wavelength channel of the WDM signal in the second optical transmission device;

a first processor that calculates a linear SNR (signal-to-noise ratio) of each wavelength channel of the WDM signal based on the optical power of each wavelength channel detected by the second optical channel monitor;

a second processor that calculates a non-linear SNR of each wavelength channel of the WDM signal based on the optical power of each wavelength channel detected by the first optical channel monitor;

a third processor that calculates a GSNR (generalized SNR) for each wavelength channel of the WDM signal using the linear SNR calculated by the first processor and the non-linear SNR calculated by the second processor; and

a fourth processor that controls transmission power of each wavelength channel of the WDM signal transmitted from the first optical transmission device based on the GSNR of each wavelength channel calculated by the third processor.

2. The optical transmission system according to claim 1 , wherein

the fourth processor controls transmission power of each wavelength channel of the WDM signal transmitted from the first optical transmission device so as to reduce variations in the GSNR of each wavelength channel calculated by the third processor.

3. The optical transmission system according to claim 1 , wherein

the first optical transmission device includes:

an optical circuit that controls optical power of each wavelength channel of the WDM signal in accordance with an instruction given from the fourth processor; and

an optical amplifier circuit that controls optical power of the WDM signal in accordance with an instruction given from the fourth processor.

4. The optical transmission system according to claim 1 , wherein

the second processor calculates a non-linear noise by multiplying a cube of the optical power detected by the first optical channel monitor by a specified proportionality coefficient for each wavelength channel, and calculates the non-linear SNR by calculating a ratio between the optical power detected by the first optical channel monitor and the non-linear noise.

5. The optical transmission system according to claim 4 , wherein

the second processor corrects the proportionality coefficient based on a fiber loss coefficient of the optical fiber transmission line, an occurrence position of a ramp loss, and a level of the ramp loss.

6. An optical transmission device that transmits a WDM (wavelength division multiplexed) signal to a reception node via an optical fiber transmission line, the optical transmission device comprising:

an optical channel monitor that detects transmission power of each wavelength channel of the WDM signal; and

a processor that

acquires information indicating a linear SNR (signal-to-noise ratio) of each wavelength channel of the WDM signal, the linear SNR being calculated based on received optical power of each wavelength channel of the WDM signal detected at the reception node,

calculates a non-linear SNR of each wavelength channel of the WDM signal based on optical power of each wavelength channel detected by the optical channel monitor,

calculates a GSNR (generalized SNR) of each wavelength channel of the WDM signal using the linear SNR and the non-linear SNR, and

controls the transmission power of each wavelength channel of the WDM signal based on the GSNR of each wavelength channel.

7. The optical transmission device according to claim 6 , wherein

the linear SNR of each wavelength channel of the WDM signal is calculated at the reception node, and

the processor acquires the information indicating the linear SNR of each wavelength channel of the WDM signal from the reception node.

8. The optical transmission device according to claim 6 , wherein

the linear SNR of each wavelength channel of the WDM signal is calculated in a network control device connected to the optical transmission device and the reception node, and

the processor acquires the information indicating the linear SNR of each wavelength channel of the WDM signal from the network control device.

9. A method for controlling optical transmitting power of each wavelength channel of a WDM (wavelength division multiplexed) signal in an optical transmission system that transmits the WDM signal from a first optical transmission device to a second optical transmission device via an optical fiber transmission line, the method comprising:

detecting optical transmitting power of each wavelength channel of the WDM signal by using a first optical channel monitor in the first optical transmission device;

detecting received optical power of each wavelength channel of the WDM signal by using a second optical channel monitor in the second optical transmission device;

calculating a linear SNR (signal-to-noise ratio) of each wavelength channel of the WDM signal based on the received optical power of each wavelength channel detected by the second optical channel monitor;

calculating a non-linear SNR of each wavelength channel of the WDM signal based on the optical transmitting power of each wavelength channel detected by the first optical channel monitor;

calculating a GSNR (generalized SNR) of each wavelength channel of the WDM signal using the linear SNR and the non-linear SNR; and

controlling the optical transmitting power of each wavelength channel of the WDM signal based on the GSNR of each wavelength channel in the first optical transmission device.