Measurement device, measurement method, transfer device, and optical network

A measurement method, comprising:

• obtaining a first power ratio that indicates a ratio of optical signal power of a first wavelength in a first spectrum at a reception device to optical signal power of a second wavelength different from the first wavelength in the first spectrum;
• obtaining a second power ratio that indicates a ratio of optical signal power of a first wavelength in a second spectrum at a transmission device to optical signal power of a second wavelength in the second spectrum;
• calculating an optical signal-to-noise ratio (“OSNR”) of the optical signal at the reception device using the obtained first power ratio and the obtained second power ratio;
• and
• outputting the calculated OSNR.

A transfer device, comprising:

• a first obtaining unit configured to obtain a first power ratio that indicates a ratio of optical signal power of a first wavelength in a first spectrum of an optical signal received from a transmission device to optical signal power of a second wavelength different from the first wavelength in the first spectrum;
• a second obtaining unit configured to obtain, from the transmission device, a second power ratio that indicates a ratio of optical signal power of the first wavelength in a second spectrum of the optical signal at the transmission device to optical signal power of the second wavelength in the second spectrum;
• a calculation unit configured to calculate an optical signal-to-noise ratio (“OSNR”) of the received optical signal using the first power ratio obtained by the first obtaining unit and the second power ratio obtained by the second obtaining unit;
• and
• an output unit outputs the OSNR that is calculated by the calculation unit.