Abstract: A fast packet and frequency switch, with inputs and outputs connected to optical fibers, each allowing the transit of a certain number of different-wavelength optical carriers, modulated by serial information flows organized into packets. The packets are phase-realigned and their labels are converted under the control of external processors designed to set-up and break connections. Then a frequency conversion of the optical carriers allotted to packets is carried out and the packets are recombined into a single fiber by a passive recombination network in order to be stored into an optical loop memory, which is an optical fiber delay line. Each optical packet flow is extracted at suitable times, is frequency-converted and, among the various frequencies obtained, there are selected only those to be sent to corresponding output fibers outgoing from the switch, after having been recombined with those of the other converted flows.