A method and apparatus for switching an optical data stream via an optical network node, capable of switching optical data received at input ports to output ports. The method includes the following steps performed by a processing chain upon detection of a stream at a given wavelength by a given input port: determining a resource of the node based on a predetermined routing policy such that, for a given wavelength common to source and destination nodes of the stream, routing within the network is carried out according to a routing tree covering the network, a root of the tree being the destination node; consulting an occupancy table for the resource, indicating if at least one possible preceding stream is using the resource; determining a delay to be applied by the processing chain to prevent a collision between the stream and the possible preceding stream; and configuring the processing chain to apply the delay.