The present invention relates to an integrated apparatus for monitoring the separation of the solid and liquid phases in a centrifugal by measuring at least one parameter of a filling material inside a centrifugal, the integrated apparatus comprising at least one light source for illuminating at least part of a surface of the filling material, and a light detector arrangement being a adapted to receive light reflected from the filling material. The present invention also relates to an associated method for monitoring and controlling separation of solid and liquid phases in a centrifugal.