Abstract: An optical network is provided which comprises a plurality of optical network units (19) and optical source means (3) connected and arranged to transmit light signals to each of the plurality of optical network units (19). The optical source means (3) are capable of transmitting light signals at one or more of a plurality of different wavelengths and at least one optical network unit (19) is operable to accept more than one of the said wavelengths. Further, each wavelength of the plurality is accepted by at least one of the optical network units (19) such that each such wavelength is accepted by a different subset of optical network units (19). The optical network further comprises control means (18) operable to cause the optical source means (3) to transmit light signals at one or more selected such wavelengths corresponding to respective desired subsets of the optical network units (19).