In this paper, we present an all-optical network architecture and a routing protocol for it. The coloured sparse optical torus network (CSOT ) consists of an n × n torus for which n = b 2 for some b ∈ {2, 3, 4, . . .}. Processors of the network are deployed at nodes for which (i + j) mod b ≡ 0, where i and j are row and column indices of a node and b is the block size and the number of wavelengths used. The number of processors is P = b 3 . Routing is based on scheduled transmission of packets and wavelength-division multiplexing. The routing protocol ensures that no electro-optical conversion is needed at the intermediate nodes and all the packets injected into the routing machinery reach their targets without collisions. A work-optimal routing of h-relations is achieved for a reasonable size of h ∈ Θ(P log P ).