Optical Modules and Readout Scheme for the KM3NeT Neutrino Telescope

The KM3NeT consortium has completed a Technical Design Report (TDR) for a proposed multi-cubic-kilometer sized underwater neutrino telescope that will be deployed in the Mediterranean Sea. The basic unit of an underwater neutrino telescope is the Optical Module (OM), a pyrex glass sphere capable of withstanding the great pressure of the deep sea (up to 5 km water depth) where the telescope will be deployed. The glass spheres house photomultipliers (PMTs), either a single large PMT or many smaller ones, which register the Cherenkov light arising from the secondaries of neutrino interactions. The front-end electronics, installed off-shore, will be based on an ASIC implementing a time-over-threshold signal processing. For the readout scheme, the preferred solution is a fully optical fibre-based approach with point-to-point connections between OMs and shore. All signals above an adjustable noise-rejection threshold will be transferred to shore.