British Telecommunications Public Limited Company

British Telecommunications Corporation

Alan M Hill

David B Payne

Derek Nesset

Mark Edward Scopes

Albert Rafel Porti

Albert Rafel

Kevin J Blyth

The present invention relates to the introduction of an outstation into an optical network. The optical network has a central station, and a plurality of previously introduced outstations which are optically connected to the central station. The network is operable in: a normal operating state in which data traffic is received from previously introduced outstations at a normal data rate; and, a set-up state in which the transmission of data traffic from the previously introduced outstations is restricted relative to the normal state, the method including the step of: when the network is in the set-up state, performing a set-up operation for introducing the outstation into the optical network, the set-up operation involving the transmission of set-up data from the outstation being introduced, wherein the set-up data is transmitted at a reduced rate relative to the normal operating rate.

Method of introducing an outstation into an optical network and outstation therefor

A protected passive optical communications system includes terminals, a main head end, and a back up head end allowing communication with the terminals when a fault occurs. The main and back up head ends transmit frames that include header and payload portions to the terminals. The main head end normally transmits control instructions in the header and user data in the payload. The back up head end, in response to a fault, transmits control instructions in the payload, and a control message in the header. The control message indicates control instructions in the payload. If a control message is in the header, each terminal interprets the payload as control instructions for changing operational attribute(s) of a terminal. If a control message is not in the header, each terminal interprets the payload as user data that it forwards to external user(s) external based on an address from the user data.

Optical communication

A method of allocating switch requests within a packet switch, the method comprising the steps of collecting switch request data at each input port; processing the switch request data for each input port to generate request data for each input port-output port pairing: comparing the number of requests from each input port and to each output port with the maximum request capacity of each input port and each output port; satisfying all requests for those input-output pairs where the total number of requests is less than or equal to the maximum request capacity of each input port and each output port; reducing the number of requests for those input-output pairs where the total number of requests is greater than the maximum request capacity of each input port and each output port such that the number of requests is less than or equal to the maximum request capacity of each input port and each output port; and satisfying the remaining requests. Packets may be switched from an input port to a specified output port in accordance with the allocations obtained with the above method.

Packet switching

Available time slot(s) in a packet switch are identified in order to route a packet from an input port to a designated output port. The status of each time slot is logically combined with regard to the input port and with regard to the output port to generate the status of the time slot with regard to the given input port-output port pair. The status of input port-output port pairs is logically combined in pairs to determine whether one of the input port-output port pairs is available and the step of pair-wise logically combining the status of input port-output port pairs is repeated to determine input port-output port pair availability until one available input port-output port has been identified.

Method and apparatus for parallel packet switching

A passive optical network employs wavelength-dependent routing, and terminals that transmit request packets (requesting a data transmission slot) in a common signalling time slot. Different delays are then applied to packets on different wavelength channels, allowing a number of request packets to be processed in sequence by a single optical receiver at the network controller.

Optical communications system

A passive optical network employing wavelength dependent routing uses two-phase signalling between a network controller and terminals. In a first phase, terminals are informed of the wavelength channel allocated to them for a second signalling phase, groups of terminals being allocated to each channel. In the second signalling phase, control signals indicate to the terminal the wavelength and time slots allocated to the terminal in the following data transmission phase.

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Ipswich, United Kingdom

Alan M Hill