An optical transmission device that is provided at a first site includes: an optical transmitter that transmits a first optical signal that includes first ID information to a second site using a first wavelength; and an optical receiver that receives a second optical signal that includes second ID information and that is transmitted using the first wavelength from the second site. When the first ID information matches the second ID information, the optical transmitter transmits a wavelength report that indicates a second wavelength to the second site using the first wavelength. When the optical receiver receives a completion report that indicates the wavelength report has been received at the second site, the optical transmitter transmits an optical signal to the second site using the second wavelength, and the optical receiver ceases to receive an optical signal of the first wavelength from the second site.