Subsea long-haul transponder

A branch system connecting a transponder to a subsea optical communication trunk cable carrying data outbound from a terminus and inbound data to the terminus, the branch system comprising a trunk node connected via a branch cable to a transponder node, where:

• a. the trunk node comprises a trunk splitter coupled to an outbound fiber of the trunk cable, the trunk splitter diverting a portion of a multi-channel signal traveling on the outbound fiber to the transponder node via a receive fiber in the branch cable;
• b. the trunk node further comprises a trunk coupler coupled to an inbound fiber of the trunk cable, the trunk coupler combining a multi-channel signal traveling along an inbound fiber of the trunk cable with a transponder signal at a first wavelength, where the first wavelength is received via a transmit fiber in the branch cable;
• c. the trunk node further comprises a trunk filter, the trunk filter removing a second wavelength from the multi-channel signal traveling along the inbound fiber of the trunk cable;
• d. where the first wavelength is selected from a first sub-band and the second wavelength from a second sub-band, where the first sub-band is separate from the second sub-band;
• and
• e. where the transponder node comprises a transceiver, the transceiver comprising a receiver connected to the receive fiber and a transmitter connected to the transmit fiber.