Abstract: By using submarine cable and junction box to wire the science instruments deployed on the seafloor or in the water column into a network and combining with the terrestrial Internet and power gird to form the seafloor observation network that enables long-term, continual, real-time and in-situ ocean observing has become an important platform for ocean science research. The key technologies for designing junction box are studied and presented, including power transmission and conversion; high bandwidth communication and precise timing; power fault detection and isolation; and sealing and construction design. Based on the studied technologies, some prototypes of the junction box are built. Tests like water tank and high pressure simulative tests, shallow sea operation trial, and deep sea operation trial are carried out successfully and validated the relative technologies: Power distribution and management method based on DC power conversion can be applied on seafloor observation network; point to point communication on trunk cable via optical fibers and multi-stage tree communication structure could satisfy its requirement; detecting and isolating over-voltage, over-current and ground faults on individual port can enhance the reliability of the system; and modularized design and detachable structure could lower the cost and make it maintainable.

Key words: DC power, fault detection and isolation, seafloor observation network, timing