A link connectivity verification message to recognize a physical link connection state is transmitted from the WDM to the PXC on a C-plane. The PXC transmits a link connectivity verification ACK message including information representing a physical link connection state, and the WDM transmits a cross-connect instruction message to cross-connect a transmission side and a reception side of a port (port 1) of the PXC. Probe light transmitted from the port (port a) of the WDM is turned back by a cross-connect of the port (port 1) of the PXC. The WDM receives the probe light to verify a link connectivity.