  The JUNO observatory is a medium baseline experiment in construction in
China. A large liquid scintillator volume detects the antineutrinos issued from
nuclear reactors. The liquid scintillator detector is instrumented with 17000
large photomultiplier tubes. Two veto systems are added to reduce the
backgrounds. The front-end electronics system performs analog signal processing
(the underwater electronics) and after about 100 m cables, the back-end
electronics system, outside water, consists of the DAQ and the trigger. One of
the main challenges of the whole electronics system is the fast data link (250
Mb/s) combined with the power delivery over 100 m Ethernet cables. Three
different options are considered to connect the front-end and the back-end
systems, depending on the DAQ data volume and the way to deliver the power to
the underwater system. In order to test the three options in an efficient and
fast way, a common baseboard with interfaces to different mezzanine boards is
designed.
