Optical transmission system, optical device, and optical transmission method

An optical transmission system comprising:

• a first optical device configured to change a transmission line of a wavelength band signal propagating through a first optical transmission line to a second optical transmission line being a same path as the first optical transmission line, in a stage before a failure part in the first optical transmission line;
• and
• a second optical device configured to change the transmission line of the wavelength band signal from the second optical transmission line to the first optical transmission line, in a stage after the failure part;
• wherein
• the first optical transmission line includes a plurality of first optical fibers, and
• the first optical device determines a priority band signal as the wavelength band signal for each of the plurality of first optical fibers among a plurality of first wavelength band signals constituting a first wavelength multiplexing optical signal propagating through each of the plurality of first optical fibers, based on priority degrees of the plurality of first wavelength band signals, and changes each transmission line of the priority band signals to the second optical transmission line.