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).

Abstract: An optical line termination (OLT) device (12) generates a plurality of optical signals having different respective wavelengths (&lgr;1, &lgr;2), each optical signal carrying data, and wavelength-division-multiplexes the optical signals. A plurality of optical network units (ONUs 141-145) are connected to the OLT device (12) by way of a passive optical network (6) so as to receive the wavelength-division-multiplexed optical signals. Each ONU (14) has a wavelength selection unit operable in dependence upon control information sent from the OLT (12) to the ONU (14) concerned by way of the passive optical network (6) to select one of the optical signals of the plurality, and also has a detector for processing the selected optical signal to derive therefrom the data carried thereby.