An implantable device for optically stimulating a brain of a human being or animal, including: a multi-channel biocompatible catheter including a plurality of channels extending substantially parallel to each other relative to a longitudinal axis of the multi-channel catheter a light guide, extending into one channel, for optically stimulating the brain, the multi-channel catheter acting as a sheath totally enveloping the light guide a functional element, extending into another channel, to measure light injected into a surrounding medium at a distal end of the light guide and/or an element acting on the shape of the multi-channel catheter.
