Research progress of a mooring buoy system for sea surface and seafloor observation

Abstract

Because ocean observation of the sea surface and seafloor is in three dimensions, a new ocean observation system is established. This system synchronously collects hydrological, meteorological, and water quality information and video (seafloor and seafloor) data and can transmit this data to a shore monitoring center in a real-time mode. This system includes an ocean buoy (on the surface), seafloor junction box (on the seafloor), and electro-optical-mechanical (EOM) cable. The EOM cable, acting as a transmission medium for power and communication, connects the buoy and seafloor junction box. Power is transmitted from the buoy to the seafloor node through the EOM cable. The seafloor data is transmitted to the surface buoy via optical fiber communication. At last, the seafloor and sea surface observational data are transmitted to a shore monitoring center via satellite or wireless in real-time mode. Owing to the needs of buoy mooring, data transition, and power offering, the system is redesigned compared to traditional buoys. The communication link is constructed as follows: seafloor observation (underwater junction box)-Ethernet (underwater junction box)-optical Ethernet switch-EOM cable-optical Ethernet switch-Ethernet (buoy)-satellite (buoy). For mooring the surface buoy, a neutral buoyancy cable with optical fibers and electronic wires is designed. The load-bearing layer of the EOM cable comprises fibrous material that reduces the requirement of the buoy reserve buoyancy. Thus, the cable is neutral in seawater and can be deployed at great depth. A wind power generator and solar are combined to provide power to the buoy and seafloor node. A DC-DC boost/decrease inverter modular is utilized to adjust the voltage for power transmission via the EOM cable. To deploy the system in the deep sea, a winch is designed to launch the EOM cable and recover the EOM cable and seafloor node without a remote-operated-underwater-vehicle or wet plugging technology, which reduces the cost and the risk in sea trials. Through an offshore test, the reliability of the whole communication link and the feasibility of the launch and recovery process are verified. This system has long-term endurance and a stable power supply capabilities for sea surface and seafloor observation. Moreover, this system satisfies the requirements of real-time observation and information transmission of sea surface and seafloor. Particularly, the seafloor and surface video data can be transmitted to a shore monitoring center, which is of great significance in observation of sea acoustics, geology, and earthquakes.