Patent ID: 7277632

Claim:
A method for assigning a predetermined wavelength between two different nodes in a wavelength division multiplexing (WDM) ring communication network that has an N number of nodes and at least one pair of optical fibers sequentially connecting the N number of nodes, the method comprising the steps of: forming a matrix that represents optical-path configuration and wavelength assignment for an N−1 number of nodes; extending the matrix by adding a column at any position of the matrix and then assigning X to locations of the added column; adding an N/2 number of rows in the matrix; tracking along each row toward the left, from the added column, to find a first encountered numeral and increasing the found numeral by one; assigning numerals 1, 2, . . . , N/2 sequentially to locations corresponding to the added column in the added rows, and assigning X to locations next to the numeral-assigned locations, the number of X-assigned locations being equal to a hop-number corresponding to the assigned numeral minus 1; and tracking along each of the added rows toward the right to find an empty location and assign thereto a numeral not used, among the numerals 1, 2, . . . , N/2, in the same column as the empty location and assigning X to locations next to the empty location, the number of X-assigned locations being equal to a hop-number corresponding to the assigned numeral minus 1, where N being an even number, and X representing that an optical path of the corresponding node is not formed, wherein the matrix provides a new path between the N number of nodes when a failure occurs in any one node of WDM ring communication network.