Abstract: The present invention relates to communications network design, and in particular the use of passive optical networks (PONs) for optimising an existing large network infrastructure such as a backhaul network.

Abstract: In order to satisfy requests for a connection path having a specified capacity between two specified terminations (21, 29) of a telecommunications network, a plurality of distinct subsidiary networks are defined (30, 31, 32, 33, 34, 35), each comprising a subset of the nodes making up the complete network (20), and the connections between the subset of nodes. A connection path is determined by identifying connection path elements between interface nodes (312, 324; 334, 345), etc in each subsidiary network (31, 33 etc), identifying connections (302-312, 324-334, 345-355), between the subsidiary networks, and selecting a complete connection path (21, 302, 312, 324, 334, 345, 355, 29) by combining the connection path elements so identified. By partitioning the problem to be solved in this way, the processing time is reduced and any changes to part of the system only require adjustment of that part.