Method for assignment of wavelength channels in an optical bus network

Method for assigning wavelength channels in an optical bus network comprising N optical nodes and two pairs of optical fibres, the first of which is adapted to facilitate simultaneous, two-way communication between all nodes of the bus network, whilst the second is adapted, after protective switching, to maintain the said communication in the event of an interruption in the first pair of fibres, wherein

• the channel assignment is performed with re-use of channels, transmitters and receivers respectively being assigned a total of (N.sup.2 -1)/4 different wavelength channels on the bus network if N is an odd number and a total of N.sup.2 /4 different wavelength channels if N is an even number;
• N-1 channels are assigned to each node on the network;
• the bus network is regarded for channel assignment purposes as a ring network comprising an optical fibre intended for transmission in one direction, the channels in each node being reserved in pairs for communication with other nodes in one direction of the bus network in such a way that each of the channels reserved for any node is re-used at least once if N is an even number and at least twice if N is an odd number;
• that each wavelength channel occurs just once on each section of the ring network;
• and
• that each channel on the bus network assigned to the ring network is used for transmission to and from a node.

Method for assigning wavelength channels in an optical bus network comprising N optical nodes and two pairs of optical fibres, the first of which is adapted to facilitate simultaneous, two-way communication between all nodes of the bus network whilst the second is adapted, after protective switching to maintain the said communication in the event of an interruption in the first pair of fibres, wherein

• the same channels are assigned to the final nodes of the bus network as are assigned in the initial nodes of the bus network, so that the bus network, for the purpose of channel assignment, is regarded as a ring network;
• in a first node N-1 different wavelength channels are reserved in pairs in common with the other nodes arranged downstream on the bus network, up to the distance (N-1)/2 nodes if N is an odd number and (N/2)-1 nodes if N is an even number, together with a further channel for communication with the node at the distance N/2 if N is an even number;
• in a second node, for which one or two common communication channels have been reserved in the first node and which are situated at the greatest distance from the first node, the same channel or channels are reserved in common with a third node in the same direction on the bus network, which third node is, at most, situated at the same distance from the second node as the latter is from the first node
• the channel assignment is performed in the same way for the third node and nodes following this until the first node of the bus network is reached;
• channels are in the same way reserved in common between each of the nodes following the first node on the bus network until each node has been assigned N-1 wavelength channels and a total of (N.sup.2 -1)/4 separate wavelengths have been assigned to all nodes if N is an odd number and a total of N.sup.2 /4 separate wavelengths have been assigned to all nodes if N is an even number;
• and
• the channels assigned to each node are distributed for transmitting and receiving on respective fibres so that two channels of the same wavelength are never used on any common section of an optical fibre on the bus network in a network configuration and that a node never both transmits and receives information from a certain other node by way of the same wavelength channels.