Abstract: An optical network which is arranged to ensure communication between nodes in a lower-order loop and a higher-order loop when there is an interruption in the lower-order loop or in the event of hub failure. Each lower-order loop consists of a bus network with hubs and one or a plurality of nodes. Two optical fibers connect the nodes in each bus network and are used for communication in opposite directions between the nodes. Each bus network comprises precisely two hubs of which the first closes the bus network end at the first end thereof and the second closes the bus network at the other end. The hubs connect the bus networks in a lower-order loop and join this loop to a higher-order loop. Each node in the bus network is arranged to communicate with each hub. Channel allocation can be carried out so that channels received in one node are re-used for transmission on the same fiber from the same node.

Abstract: Channels are assigned in an optical bus network, including N nodes connected in series to one another by way of a pair of optical fibers, which facilitate simultaneous, two-way communication between all nodes of the bus network. A second pair of optical fibers, which directly connect the first and second nodes of the bus network, is adapted, after protective switching, to maintain the communication in the event of an interruption in the first pair of fibers. Each transmitter on the bus network transmits a certain network channel. Each receiver on the bus network receives a certain wavelength channel and allows other wavelength channels to pass to the next node. The channel which is received by a receiver in a node is entirely removed from the network, whereafter the channel can be re-used for transmission of information between two other nodes.

Abstract: In a method of determining the refractive index of a gaseous, liquid or solid sample, preferably a gaseous or liquid sample, there is used a waveguide resonator (1) which includes an open waveguide (4) and a closed waveguide (5) located adjacent the open waveguide. The sample is brought to the vicinity of the closed waveguide (5) so as to influence the proximal surroundings of the waveguide and therewith its effective refractive index. Light derived from a light source (9) is coupled to one end of the open waveguide (4) and transmitted light is measured at the other end of the open waveguide to establish the influence of the sample on the resonance wavelength and therewith determine the refractive index of the sample or a sample-related refractive index difference. A device for carrying out the method includes a waveguide resonator having a sample contact area (12) adjacent the closed waveguide (5) of the waveguide resonator.