Abstract: Methods, systems and apparatus for manipulating electromagnetic radiation such as laser beams include a first acousto-optic deflector optimised for efficient transmission at the input beam angle and a second acousto-optic deflector of lower peak efficiency than the first acousto-optic deflector but which accepts beams from a wider range of angles at better transmission efficiency than the first acousto-optic deflector by passing a beam optimised for efficient transmission through the first acousto-optic deflector at the input beam angle, deflecting the beam using the first acousto-optic deflector, passing the deflected beam through the second acousto-optic deflector, which has a lower peak efficiency than the first acousto-optic deflector and accepts beams from a wider range of angles at better transmission efficiency than the first acousto-optic deflector, and deflecting the beam using the second acousto-optic deflector.

Abstract: 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.

Abstract: Methods, systems and apparatus for manipulating electromagnetic radiation such as laser beams. A method and apparatus for correcting magnification chromatic aberration utilises 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 polarisers 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.

Abstract: 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.

Abstract: Methods, systems and apparatus for manipulating electromagnetic radiation such as laser beams. A method and apparatus for correcting magnification chromatic aberration utilises 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 polarisers 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.

Abstract: 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.

Abstract: Methods, systems and apparatus for manipulating electromagnetic radiation such as laser beams. A method and apparatus for correcting magnification chromatic aberration utilises 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 polarisers 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A communications network is provided in which switching nodes configure periodically. There is a plurality of shortest paths having equal propagation delays between two switching nodes between which there is at least one intermediate node.

Abstract: A conventional construction of light emissive III-V semiconductor device is modified by the inclusion in the active region of the device of not more than 5 atomic percent of a group III or group V substituent of significantly different atomic radius than that of the element for which it is substituted. The microstress field in the neighborhood of dislocation in the active region produces local modification of the concentration of the substituent causing a reduction in the magnitude of the microstress field associated with these dislocations.