Abstract: In a ring network communication structure for communication on an optical carrier (3A, 3B), a plurality of nodes (2A, . . . , 2E) are interconnected by means of connections comprising at least a first (3A) and a second (3B) optical carrier, such as an optical fiber. Transmission occurs on the ring according to a WDM scheme, by utilizing a first wavelength (.lambda..sub.1) for communication in one direction on the first carrier (3A) of said pair, while communication in the opposite direction occurs by employing a second wavelength (.lambda..sub.2) on the other optical carrier (3B). In the presence of a failure on one of the connections, the nodes adjacent (2B, 2C) to the failed connection reconfigure themselves to ensure the continuation of communication on the alternative path provided by the ring, by utilizing the first wavelength (.lambda..sub.1) on the second carrier (3B) and the second wavelength (.lambda..sub.2)on the first carrier (3A). Preferential application to SDH optical fiber ring networks.

Abstract: Within an optical ATM node, an ATM cell to be synchronized is sent into a segment of pre-determined length of an optical fiber with a high time dispersion (FD), after having been associated, in a tunable wavelength converter (CL), to an optical carrier with a wavelength that is different from that with which the cell itself was received and such that, as an effect of the transit the fiber (FD), the cell reaches the input side of a switching element (Eml . . . Emh) of the node (NC) at a predetermined instant.

Abstract: The device includes a first optical circulator connected in series with the line (1e, 1u) in order to receive a signal stream including a carrier to be extracted, modulated by an information signal, and to transmit a signal stream including the same carrier, re-inserted into the stream after having being modulated with another information signal, and a second optical circulator connected to local information processing means, to which it supplies the extracted carrier and from which it receives the carrier to be re-inserted. Between the two circulators there is an optical-fibre bandpass filter that can be tuned to the carrier wavelength.

Abstract: The device includes a first and a second optical circulator (C1, C2) having an input port and an output port that are the inputs and the outputs of the switch, as well as an optical bandpass filter (FP) placed between the two circulators (C1, C2) and connected with means for switching its state so that the filter either reflects or transmits a given wavelength, thus allowing a carrier with this wavelength at the input port of one of the circulators (C1, C2) to reach the output port of the same circulator or the output port of the other circulator.