Optical systems and devices for processing spectral groups, and optical methods for forming spectral groups, the optical system including at least one sub-network including at least one spectral group router configurable to route a plurality of optical signal channels within a spectral group, when contained within said sub-network and terminate optical channels within a spectral group, when bounding said sub-network, each optical signal channel being transmitted from one node within said sub-network to another node in said sub-network.