The KM3NeT consortium ( - supported through the European Union's 6th framework programme in a 3-year Design Study - aims at the construction of a cubic kilometre-scale neutrino telescope for the Northern hemisphere to complement the sky coverage of IceCube and have an unsurpassed sensitivity and angular resolution - better than 0.1º at 100TeV. This challenging project will require the installation of thousands of photon detectors with their related electronics and calibration systems several kilometres below the sea level. Several hundred vertical detection units containing photomultipliers will be deployed on a seafloor site up to km far from the shore below several kilometres the sea level. T HE S EA B ED P OWER AND D ATA T RANSMISSION N ETWORK FOR THE KM3N E T N EUTRINO T ELESCOPE Abstract The KM3NeT EU-funded consortium, pursuing a cubic kilometre scale neutrino telescope in the Mediterranean Sea, is developing technical solutions for the construction of this challenging project, to be realized several kilometres below the sea level. The power supply system, the data transmission and distribution network will be presented with focus on: main electro-optical cable, deep sea power conversion, subsea data and power distribution network, connection systems issue. Nuclear Science Symposium – IEEE 2009 – October 2009, Orlando, Florida, USA Riccardo Papaleo*, for the KM3NeT Consortium INFN – Laboratori Nazionali del Sud - Catania * T HE B AR FLOOR D ETECTION U NIT C ONCEPT T HE S LENDER S TRING D ETECTION U NIT C ONCEPT T HE S TRING D ETECTION U NIT C ONCEPT E XAMPLE OF THE LAYOUT OF THE SEA - FLOOR NETWORK Underwater connection systems technologies, available from telecommunication and oil and gas market, including deep-sea wet-mateable optical, electro-optical and hybrid electro-optic connectors, have been adapted and developed to fulfil the project requirements ROV UNDERWATER MATEABLE CONNECTORS DC/DC C ONVERTER FOR THE POWER SUPPLY OF THE UNDERWATER TELESCOPE. I T WILL BE INSTALLED INSIDE THE MAIN JUNCTION BOX The long distance from the deep-sea site to shore ( km) forces the use of single-mode optical fibres. The conversion of the electrical signals to optical signals can be implemented at different locations along the detection lines, or at other points in the local seabed network. The copper-to-fibre transition point is determined not only from considerations of length/bandwidth capabilities for the two media but also from the relative reliability of the deep-sea mateable connectors that are required for remotely-operated submarine interconnection of the bases of the detection lines to the junction boxes that will relay data onto the main site-to-shore fibreoptic telecommunications cable. Such deep-sea connectors have been developed for the oil industry and military applications and can be mated in seawater at ambient pressures of more than 400 bar. All signals passing certain OM-internal criteria (e.g. charge threshold) will be uploaded to shore. An total effective photocathode area of around 50m2 will generate an overall data rate (signal + background) of~ 100Gb/s, based on 8 bytes (including timestamp) per recorded photon. This data rate to shore can be accommodated on a small number of optical fibres within a single, standard fibre- optic deep-sea telecommunications cable using either coarse or dense wavelength division multiplexing (CWDM or DWDM) transfer protocols. E XAMPLE OF DATA TRANSMISSION SCHEME FOR THE FULL TELESCOPE To shore Cable In VDC 10 kV Cable Out VDC 10 kV DC/DC 5-10 kW 400 Vdc Out Fibre Out 400 Vdc Out Fibre Out ROV connector JB DC/AC DC/DC 5-10 kW The sea-floor network, necessary for the connection between the shore station and the underwater telescope, will consist of several junction boxes linked by electro-optical cables to the telescope detection units and satellite ocean sciences nodes. The final design of the network is still under development and will incorporate extensive redundancy to mitigate single point failures. The design requirements, in terms of power distribution, data transmission system and interlink connection, for an ocean observatory site-to-shore cable are compatible with the standard capabilities of telecommunications cables, for which a wide range of industry-approved standard, connection boxes, couplings and penetrators exist, which can be adapted to interface with scientific equipment The main characteristics of the data transmission system are: All data to shore: Full information on each hit satisfying local condition (threshold) sent to shore Overall data rate ~ Gbit/s Data transport: Optical point-to-point connection shore-OM, Optical network using DWDM and multiplexing, Served by lasers on shore, Allows also for time calibration of transmission delays Deep-sea components: Fibres, modulators, mux/demux, optical amplifiers (all standard and passive)