ring transmission network with reconfigurable wavelength-division multiplexing for semi-permanent connections

. The ring reconfigurable user connection has several nodes (12), in which each node is associated with one of the sites (13), in which the site has at least one user unit. The sites are connected by a fibre optic ring (18,20), passing successively by the nodes, with a predetermined information progression direction. . Each site has a transmitter and receiver (EN,ES,RN,RS) set to a given wavelength, with each node having optical insertion and extraction (IN,IS,XN,XS) mechanisms to connect the site to the ring network, or to optically isolate the site. A controller sets up temporary optical connections between two users at two sites.