Undirected cross connects are provided based on wavelength-selective switches A demand d={i, j} is routed over a path pd between ports i and j in a multi-layer network based on one or more wavelength selective switches, by determining a middle layer node n in the multi-network for which there is a first path pi between the port i and the middle layer node n and a second path pj between the port j and the middle layer node n; identifying a node n′, wherein the node n′ is a first node starting from port i that path pi shares with path pj; and concatenating the path pd comprised of a subpath p′i of the first path pi from the port i to the node n′ with a subpath of p′j of the second path pi from the node n′ to the port j. An undirected Cantor network is disclosed where the switch nodes are wavelength selective switches. An undirected Clos cross connect is also disclosed where one or more undirected switches are undirected Cantor networks having at least one wavelength selective switch.