Optical transmission system and fiber type determination method

1. An optical transmission system that includes a first optical node, a second optical node, and an optical fiber provided between the first optical node and the second optical node, the optical transmission system comprising:

a signal generator provided in the first optical node and configured to generate an optical signal including a plurality of wavelength channels and an empty channel;

an optical transmission circuit provided in the first optical node and configured to output the optical signal to the optical fiber;

an optical channel monitor provided in the second optical node and configured to measure reception powers of each wavelength channel of the plurality of wavelength channels in the optical signal received through the optical fiber; and

a processor configured to

calculate crosstalk in a wavelength in which the empty channel is provided, the crosstalk occurring due to the plurality of wavelength channels in the optical fiber, based on a ratio between the reception powers of the plurality of wavelength channels and a reception power of the empty channel, and

determine a type of the optical fiber based on a level of the crosstalk.

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

the empty channel is provided in a zero-dispersion wavelength of a dispersion shifted single-mode optical fiber or near the zero-dispersion wavelength of the dispersion shifted single-mode optical fiber, and

the processor determines whether the optical fiber is the dispersion shifted single-mode optical fiber based on the reception power of the empty channel.

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

the empty channel is provided in a zero-dispersion wavelength of a non-zero dispersion shifted single-mode optical fiber or near the zero-dispersion wavelength of the non-zero dispersion shifted single-mode optical fiber, and

the processor determines whether the optical fiber is the non-zero dispersion shifted single-mode optical fiber based on the reception power of the empty channel.

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

the signal generator includes: an ASE light source configured to generate ASE light; and

a wavelength selective switch configured to generate the optical signal from the ASE light.

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

the processor is provided in the first optical node,

the second optical node reports a result of measurement by the optical channel monitor to the first optical node, and

the processor determines the type of the optical fiber based on the result of the measurement reported from the second optical node.

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

the first optical node further includes an optical measuring device configured to emit to the optical fiber a first optical pulse in a first wavelength and a second optical pulse in a second wavelength and to detect reflected light of the first optical pulse from a discontinuity on the optical fiber and reflected light of the second optical pulse from the discontinuity on the optical fiber, and

the processor determines whether the optical fiber is a single-mode optical fiber based on a difference between a first propagation time and a second propagation time, the first propagation time indicating a period from a transmission of the first optical pulse to a detection of the reflected light of the first optical pulse from the discontinuity and the second propagation time indicating a period from a transmission of the second optical pulse to a detection of the reflected light of the second optical pulse from the discontinuity.

7. The optical transmission system according to claim 1 , further comprising

an optical relay station provided between the first optical node and the second optical node, wherein

the optical relay station blocks the empty channel in relaying the optical signal to the second optical node.

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

the second optical node includes:

a second signal generator configured to generate a second optical signal including a plurality of wavelength channels and an empty channel; and

a second optical transmission circuit configured to output the second optical signal to the optical fiber,

the first optical node includes a second optical channel monitor configured to measure reception power of each channel in the second optical signal received through the optical fiber, and

the processor determines the type of the optical fiber based on the reception power of the empty channel in the optical signal measured by the optical channel monitor, and the reception power of the empty channel in the second optical signal measured by the second optical channel monitor.

9. The optical transmission system according to claim 8 , wherein

when the reception power of the empty channel in the optical signal measured by the optical channel monitor is different from the reception power of the empty channel in the second optical signal measured by the second optical channel monitor, the processor

determines that the optical fiber includes a first optical fiber and a second optical fiber that is different in type from the first optical fiber, and

determines a type of the first optical fiber and a type of the second optical fiber based on the reception power of the empty channel in the optical signal measured by the optical channel monitor and the reception power of the empty channel in the second optical signal measured by the second optical channel monitor.

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

the processor is provided in the first optical node and controls transmission power of each wavelength channel in a wavelength division multiplexing signal to be transmitted to the second optical node in accordance with the determined type of the optical fiber.

11. A fiber type determination method for determining a type of an optical fiber provided between a first optical node and a second optical node, the fiber type determination method comprising:

transmitting an optical signal including a plurality of wavelength channels and an empty channel from the first optical node to the second optical node through the optical fiber;

measuring, in the second optical node, reception powers of each wavelength channel of the plurality of wavelength channels in the optical signal received through the optical fiber;

calculating crosstalk in a wavelength in which the empty channel is provided, the crosstalk occurring due to the plurality of wavelength channels in the optical fiber, based on a ratio between the reception powers of the plurality of wavelength channels and a reception power of the empty channel; and

determining a type of the optical fiber based on a level of the crosstalk.