OPTISCHES WAHLNETZWERK

Signals from transmitter stations are connected to receiver stations by a switched optical network. To provide a readily expandable, non-blocking network for a large network, groups of transmitter signals are formed into distinct optical wavelength multiplexes each of which is coupled by an optical fibre bus (4) to one input of each of several optical space switches (SW). Each receiver station is connected to an optical heterodyne receiver optically coupled to an output of one of the optical switches (SW). The required signal from the multiplex switched to an optical receiver is demultiplexed by combining with the multiplex an optical source (O) which has been frequency shifted by a frequency shifter (12). This is achieved by means of a secondary optical space switch (SW min ) and an optical combiner (14). The optical space switches (SW, SW min ) are controlled by a controller (6) to effect the desired connection.