Submarine optical communication system

1 . 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.

2 . The submarine optical communication system according to claim 1 , further comprising:

a second branching device; a second branching/insertion device; and a fourth terminal station, wherein

the second output circuit outputs the first multiplexed light being split by the fourth branching circuit to the second branching device,

the second branching device includes

fifth branching circuit configured to further split the first multiplexed light from the second output circuit,

fifth reception circuit configured to receive an optical signal in the control wavelength band from the first multiplexed light being split by the fifth branching circuit, and

third output circuit configured to output another piece of the first multiplexed light being split by the fifth branching circuit to the second branching/insertion device,

the second branching/insertion device includes

sixth branching circuit configured to be capable of splitting the first multiplexed light from the third output circuit,

sixth reception circuit configured to be capable of receiving an optical signal in the control wavelength band from the first multiplexed light being split by the sixth branching-circuit,

seventh branching circuit configured to be capable of splitting a third optical signal including a third main signal and a third control signal that are output from the fourth terminal station,

seventh reception circuit configured to be capable of receiving the third control signal from the third optical signal being split by the seventh branching circuit, and

fourth multiplexing circuit configured to be capable of multiplexing the third optical signal being split by the seventh branching circuit with the first multiplexed light being split by the sixth branching circuit, and outputting second multiplexed light acquired by multiplexing to the second branching device,

the third control signal is an optical signal in the control wavelength band, and

the second branching device further includes

eight branching circuit configured to split the second multiplexed light from the fourth multiplexing circuit,

eighth reception circuit configured to receive the third control signal in the control wavelength band from one piece of the second multiplexed light being split by the eighth branching circuit, and

fourth output circuit configured to output another piece of the second multiplexed light being split by the eighth branching circuit to the third terminal station.

3 . The submarine optical communication system according to claim 2 , wherein

the second branching device includes

ninth branching circuit configured to be capable of splitting a fourth optical signal including a fourth main signal and a fourth control signal from the third terminal station,

ninth reception circuit configured to be capable of receiving the fourth control signal from one piece of the fourth optical signal being split by the ninth branching circuit, and

fifth output circuit configured to be capable of outputting another piece of the split fourth optical signal to the second branching/insertion device,

the second branching/insertion device includes

tenth branching circuit configured to be capable of splitting the fourth optical signal from the fifth output circuit,

tenth reception circuit configured to be capable of receiving the fourth control signal from the fourth optical signal being split by the tenth branching circuit,

eleventh branching circuit configured to be capable of splitting a fifth optical signal including a fifth main signal and a fifth control signal from the fourth terminal station,

eleventh reception circuit configured to be capable of receiving the fifth control signal from one piece of the fifth optical signal being split by the eleventh branching circuit, and

sixth multiplexing circuit configured to be capable of multiplexing the fourth optical signal being split by the tenth branching circuit with the fifth optical signal being split by the eleventh branching circuit, and outputting third multiplexed light acquired by multiplexing to the second branching device,

wavelength bands of the fourth control signal and the fifth control signal are the identical control wavelength band,

the third terminal station and the fourth terminal station transmit each of the fourth control signal and the fifth control signal at different times from each other,

the second branching device further includes

twelfth branching circuit configured to split the third multiplexed light from the sixth multiplexing circuit,

twelfth reception circuit configured to receive an optical signal in the control wavelength band from one piece of the third multiplexed light being split by the twelfth branching circuit, and

sixth output circuit configured to output another piece of the third multiplexed light being split by the twelfth branching circuit to the first branching device,

the first branching device includes

nineteenth branching circuit configured to further split the third multiplexed light from the sixth output circuit,

thirteenth reception circuit configured to receive an optical signal in the control wavelength band from one piece of the third multiplexed light being split by the thirteenth branching circuit, and

seventh output circuit configured to output another piece of the third multiplexed light being split by the thirteenth branching circuit to the first branching/insertion device,

the first branching/insertion device includes

fourteenth branching circuit configured to be capable of splitting the third multiplexed light from the seventh output circuit,

fourteenth reception circuit configured to be capable of receiving an optical signal in the control wavelength band from the third multiplexed light being split by the fourteenth branching circuit,

fifteenth branching circuit configured to be capable of splitting a sixth optical signal including a sixth main signal and a sixth control signal from the second terminal station,

fifteenth reception circuit configured to be capable of receiving the sixth control signal from the sixth optical signal being split by the fifteenth branching circuit, and

eighth multiplexing circuit configured to be capable of multiplexing the sixth optical signal being split by the fifteenth branching circuit with the third multiplexed light being split by the fourteenth branching circuit, and outputting fourth multiplexed light acquired by multiplexing to the first branching device,

the first branching device further includes

sixteenth branching circuit configured to split the fourth multiplexed light from the eighth multiplexing circuit,

sixteenth reception circuit configured to receive the sixth control signal in the control wavelength band from one piece of the fourth multiplexed light being split by the sixteenth branching circuit, and

eighth output circuit configured to output another piece of the fourth multiplexed light being split by the sixteenth branching circuit to the first terminal station.