Submarine optical communication system

A submarine optical communication system comprising:

• a first terminal station;
• a second terminal station;
• a third terminal station;
• a first branching device;
• and a first branching/insertion device, wherein
• the first terminal station is capable of transmitting a first optical signal including a first main signal and a first control signal to the first branching device,
• the second terminal station is capable of transmitting a second optical signal including a second main signal and a second control signal to the first branching/insertion device,
• the first branching device includes
• first branching circuit configured to be capable of splitting the first optical signal from the first terminal station,
• first reception circuit configured to be capable of receiving the first control signal from the first optical signal being split by the first branching circuit, and
• first output circuit configured to be capable of outputting the first optical signal being split by the first branching circuit to the first branching/insertion device,
• the first branching/insertion device includes
• second branching circuit configured to be capable of splitting the first optical signal from the first output circuit,
• second reception circuit configured to be capable of receiving the first control signal included in the first optical signal being split by the second branching circuit,
• third branching circuit configured to be capable of splitting the second optical signal from the second terminal station,
• third reception circuit configured to be capable of receiving the second control signal included in the second optical signal being split by the third branching circuit, and
• first multiplexing circuit configured to be capable of multiplexing the first optical signal being split by the second branching circuit with the second optical signal being split by the third branching circuit, and outputting first multiplexed light acquired by multiplexing to the first branching device,
• wavelength bands of the first control signal and the second control signal are an identical control wavelength band,
• the first terminal station and the second terminal station transmit each of the first control signal and the second control signal at different times from each other, and
• the first branching device further includes
• fourth branching circuit configured to split the first multiplexed light from the first multiplexing circuit,
• fourth reception circuit configured to receive an optical signal in the control wavelength band being included in one piece of the first multiplexed light being split by the fourth branching circuit, and
• second output circuit configured to output another piece of the first multiplexed light being split by the fourth branching circuit to one of the third terminal station and a second branching device.