Abstract: A communications network includes an optical waveguide to which is connected a head-end station and at lest one optical network unit (ONU). An ONU provides an interface to the communications system for connected user equipment. Data received by an ONU from connected user equipment are stored in a buffer prior to transmission to the head-end station. The head-end station is arranged to implement, in conjunction with the ONUs a demand-assignment protocol for the transfer of data upstream from the ONUs to the head-end station according to which an ONU demands upstream capacity based upon a prediction of its future capacity requirements, calculated using at least one record of earlier granted capacity by the head-end station and at least one measurement of a quantity of data awaiting transmission to the head-end station in the buffer of the ONU.

Abstract: Disclosed is a digital communications network comprising a branched passive optical network connecting a head-end with a plurality of optical network units. The time taken to synchronize by ranging, all optical network units and the head-end, when the network needs to be initialized from scratch, has been minimized using the disclosed method. The synchronization time has been minimized by making all bandwidth in the upstream direction of the network available for the purpose of course ranging. Once the whole network is ranged, the bandwidth is made available, in a normal way, to combined data communications and operations and management functions.

Abstract: An optical network includes a head-end station connected to a plurality of optical network units via an optical fiber network having a plurality of split levels. One level of split is constituted by a n:1 repeater provided with a monitor for ranging and leveling transmissions from the optical network units.