Nortel Networks Corporation

Ucl Business Plc

Northern Telecom Limited

Stc, Inc

Paul Anthony Kirkby

K M Naga Srinivas Nadella

Peter G Hamer

David Ireland

Robin Angus Silver

Martin Biddiscombe

Radhakrishnan Kadengal

R Angus Silver

Subramanian Sabesan

Ernst A Munter

Richard E Epworth

Robert John Dean

Piers James Dawe

Martin Sabry

Michael Heffernan

John E Midwinter

Ian H White

KM Naga Srinivas Nadella

Methods and apparatus for optimising, improving or maximising the efficiency of an acousto-optic lens (AOL) system are disclosed. Data relating to efficiency is used to select drive frequencies of the acousto-optic devices (AODs) forming the AOL, thereby both increasing the usable field of view and reducing a prior art patternation problem. Preferably according to the invention, drive frequencies are selected that maximise efficiency of transmission through the AOL. When scanning, the centre of each scan is optimised to be of maximum efficiency.

Methods and apparatus for controling drive frequencies of acousto-optic  deflectors

Methods, systems and apparatus for manipulating electromagnetic radiation such as laser beams. A method and apparatus for correcting magnification chromatic aberration utilizes one or more dispersive lenses such that long wavelength components are magnified less than short wavelength components. A telecentric relay is preferred to achieve this aim. Further, the use of polarizers to block the undesired zeroth order components of diffraction emanating from acousto-optic deflectors (AODs) is disclosed. Furthermore, specific designs of AOD including narrow transducer AODs which produce a diverging acoustic wave and AODs having two transducers and a selection switch are disclosed. Further, the invention provides methods, systems and apparatus for allowing the wavelength of radiation to be changed, for providing a user selectable degree of compensation, for providing a scanning and/or a pointing system and for providing a compact system that does not require telecentric relays between adjacent acousto-optic deflectors.

Imaging apparatus and methods

The invention is directed to an acousto-optic lens (AOL) and corresponding method. The AOL of the invention comprises a first and second acousto-optic deflector, each being arranged to support a respective acoustic wave. The AOL includes a driver for synthesizing first and second drive signals for the respective first and second acousto-optic deflectors. The driver is arranged to synthesize the drive signals so as to be phase-modulated by functions that can be expressed as a Taylor series having one or more coefficients greater than second order. The functions are preferably non-sinusoidal and have sufficient magnitude at the higher orders to effect one or more of fixed aberration correction, dynamic aberration correction and Z-scanning.

Methods and apparatus to control acousto-optic deflectors

Admission of rapidly varying traffic flows to a communications network is controlled by sampling the traffic flows each at an ingress, and sampling an aggregate flow of said flows at some or all of the resources used by the aggregate flow. From this sampling, a mean bandwidth requirement for each traffic flow and a measure of the variance from that mean are determined. First and second prices for the mean and variance components of the controlled traffic flows that are calculated. These price calculations are used to determine an admission cost for each said flow so as to regulate the admission of that flow via a feedback price mechanism.

Traffic flow management in a communications network

A communications network has multiple resource-allocation layers and incorporates a management structure for allocating resources to allocate resources requested by a first layer of said layers from a second of said layers. At a first layer, the management structure provides an indication to a second layer of the required resources that are to be allocated from the second layer. The second layer automatically offers the required resource together with a condition for use of those resources. This condition includes a notional price factor which is dependent on current demand. Under the control of the manager, the first layer determines if the condition for use of the offered resources is acceptable and, if so, automatically accepts the offered resources from the second layer. In a preferred embodiment, ingress to an underlying multi-wavelength transport layer of the network is controlled via a virtual port which allocates traffic to real ports one for each wavelength supported by the transport layer.

Management and control of multi-layer networks

Internet protocol based transmissions have historically been transmitted on a best efforts basis. There are proposals to provide differentiated services to allow different packets to be delivered with different service qualities depending on the bandwidth requirements of a particular flow. By performing bandwidth monitoring within the core network and performing packet dropping and/or queuing at the network ingress, the need for packet dropping and/or queuing within the core network is removed and furthermore the core network resources are not used by packets which will not be delivered to their destination but will instead be dropped within the core network.

Differentiated services in packet-switched networks

A packet scheduling scheme schedules packets from a plurality of queues onto outgoing link. The scheme associates a weight and a virtual start time with each of the queues. Queues are selected, in order of the virtual start time, until a non-empty queue is selected. One or more packets are sent from the selected queue and then the virtual start time is updated, based on the length of the transmitted packet and the weight associated with the selected queue.

Scheduling and reservation for dynamic resource control systems

In order to provide price information to customers quickly a fast reflector switch is used. This helps to ensure that price information provided to customers is as up-to-date as possible. To determine a price for use of a particular route in a communications network, the available resources at each node in that route are assessed. The most congested node in that route is selected and a price determined on the basis of the available capacity at that node. This price is then delivered to the customer via the fast reflector switch. In another example, the average amount of available resources at each node in the route is determined over a specified time period. The standard deviation of the resource level values at each node over the specified time period is also determined. A price is then set on the basis of the sum of the average amounts and the sum of the standard deviations. In this way a price which takes into account recent variation in traffic levels as well as average traffic levels is provided.

Pricing mechanism for resource control in a communications network

A network is disclosed for carrying calls between entities. Network resources which generate charges include means arranged to determine the charging rate for their use dynamically, and to transmit charging rate or tariff data representing a proposed or actual charging rate or tariff, or a change or proposed change thereto, through the network before and/or during the call to the entity or entities liable to the resource for the charges.

Method for charging in a data communication network

The Invention provides a distributed resource allocation Method. The distributed resource allocation method is based on the concept of proportional fairness. In this method, users express their willingnesses to pay to the local distributed controller which is associated with those users. The bandwidth allocated to each user is determined by the local controller with which they are associated and the allocation takes into account the relative demands on all the resources in the network and the time taken for those demands to reach the distributed local controllers. The distributed controllers each use only locally available information at their respective nodes, but take into account the delays between nodes. The locally available resource (i.e. bandwidth) is divided in proportion to the willingnesses to pay expressed by the various users entering their particular node. On a ring (and in other networks where the only place that traffic streams are multiplexed is at the periphery) this guarantees that no data will be lost (due to cell/packet collision) once it has been launched.

Method of allocating resources in a telecommunications network

The invention provides a resource allocation method which is based on the concept of proportional fairness. In this method, users express their willingnesses to pay for network resources. A controller determines how the users' willingnesses to pay are to be divided between the resources in order to determine the relative demands for the resources. Each resource is then divided between those users using it in proportion to how much they are willing to pay for the use of their share of it. The allocation takes into account the relative demands on all the resources in the network. A user may increase his share of the network resources allocated to him by increasing the value of his willingness to pay. The method may be applied either by a central controller (network manager), or it may be delegated to controllers (network element managers/customer premises equipment managers) distributed across the network.

A communication network with a set of nodes each arranged to extract signals received on orthogonal input paths when there is a predetermined correlation between them, and to retransmit the signals on orthogonal output paths when the predetermined correlation is absent. Each node is further arranged to launch signals intended for a particular destination node on orthogonal paths with a phase difference such that the signals arrive at the destination node with the predetermined correlation. Thus local processing of the signals is sufficient to extract a signal intended for a particular node. There is no need for centralized control or for the separate transmission of signaling data.

Communications network

A communication system having (a) an access layer in which local access networks give access to entities, (b) a packet switching layer providing switched communication between the local access networks, and (c) a cut through layer providing guaranteed quality of service communication between the local access networks. The entities signal selection of the packet switching network and/or the cut through network to its access network. The cut-through network can be selected when the packet switching network is congested and the user attributes priority to the communication. Preferably the local access networks are arranged to transmit tariff data to user entities which are arranged to display tariff data for a cut-through network.

Growing community of inventors

Old Harlow, United Kingdom

Paul Anthony Kirkby