The optical data transport system of the KM3NeT neutrino
telescope at the bottom of the Mediterranean Sea will provide more
than 6000 optical modules in the detector arrays with a
point-to-point optical connection to the control stations
onshore. The ARCA and ORCA detectors of KM3NeT are being installed
at a depth of about 3500 m and 2500 m, respectively and their
distance to the control stations is about 100 kilometers and
40 kilometers. In particular, the two detectors are optimised for
the detection of cosmic neutrinos with energies above about 1 TeV
(ARCA) and for the detection of atmospheric neutrinos with energies
in the range 1 GeV–1 TeV (ORCA). The expected maximum data rate
is 200 Mbps per optical module. The implemented optical data
transport system matches the layouts of the networks of
electro-optical cables and junction boxes in the deep sea. For
efficient use of the fibres in the system the technology of Dense
Wavelength Division Multiplexing is applied. The performance of the
optical system in terms of measured bit error rates, optical budget
are presented. The next steps in the implementation of the system
are also discussed.