The present invention relates to light curtains and, in particular, to safety light curtains for monitoring a protective field and to optical units of such light curtains which comprise optoelectronic components interconnected by a communication bus and to a method for allocating individual addresses to each of a plurality of optoelectronic components. The optical unit comprises a controller unit, a plurality of optoelectronic components interconnected by means of a communication bus, each of said optoelectronic components having a transmission input terminal for receiving a transmission signal and a transmission output terminal for outputting a transmission signal, and a receiving terminal for receiving a control signal from said control unit. An individual address is allocated to each of said optoelectronic components depending on a position of the respective optoelectronic component with respect to the other optoelectronic components.