Abstract: An optical network, which may be an all-optical network, including passive wavelength routers is described. Methods for implementing such networks as well as different router configurations which may be used in optical networks are also disclosed. The routing functionality in the all-optical network can be done in the optical domain without switching elements at the nodes. This is achieved by routers which are passive and preferably operative to route wavelength bands. A mesh can be used as the network configuration. The optical networks described can be used to facilitate the transmission of higher network protocols, such as internet protocol (IP) packets or ATM-cells, purely in the optical domain.