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 3100m down to 5100m, in the southeast Ionian sea, at sites near Pylos, Peloponnese, Greece, are discussed.