One of the optical transmission device (1-1), at least one of the other optical transmission devices (1-3) and an optical repeater (1-2) is, compensates for the chromatic dispersion at a wavelength path before switching, one optical transmission equipment, or other optical transmission devices, so as to compensate for the chromatic dispersion at a wavelength path after switching, as well as changing the wavelength dispersion compensation amount at one of the optical transmission equipment, or other optical transmission devices, optical repeater device, so as not to substantially change due to a change of the wavelength dispersion compensation amount at the wavelength dispersion compensation amount of the sum is one of an optical transmission device or other optical transmission device receiving the signal light transmitting the optical path before switching, optical After changing the wavelength dispersion compensation amount at the relay device, it is changed to the value which the wavelength dispersion compensation amount at one of the optical transmission equipment, or other optical transmission devices can compensate for chromatic dispersion at a wavelength path after switching, before switching switching to the wavelength path after switching to be implemented from the wavelength path.
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