A light intensity measuring system for sedimentation measurements on KM3NeT optical modules

To measure variations of zenith dependence of sedimentation/bio-fouling on the optical modules (OMs) as considered by the KM3NeT consortium in the deep sea, we have used a grid of photodiodes distributed inside the glass sphere to measure the light intensity of two light sources located outside the glass sphere on a fixed position. The method is described and the data collected during the last three years in depths from 3100 m down to 5100 m, in the southeast Ionian sea, at sites near Pylos, Peloponnese, Greece, are discussed.