Abstract: A lighting system for an interior of a building includes a device for collecting and converting sunlight into concentrated light consisting of a stack of fluorescent sheets. The collecting device is optically coupled, preferably by way of an optical joint to a channelling member such as an optical cable, so that the concentrated light passes to the channelling member and is channelled to a light emitting fitting for the interior of the building. The channelling members are formed such that their cross-sectional shape changes from the cross-section of the collecting device to the cross-section of the channelling members with an approximately constant cross-sectional area being maintained throughout the change of cross-sectional shape, whereby the coupling device is an optical joint created by a medium having a refractive index close to that of the collecting device and channelling members.