Nortel Networks Corporation

Northern Telecom Limited

Ciena Corporation

Adrian Paul Sparks

Robert William Spagnoletti

Robert Friskney

Peter David Roorda

Robin Paul Rickard

Peter D Roorda

Frederick J Lalonde

William A Crossland

Simon P Parry

Alan Robinson

Nigel Robert Davis

Nigel Baker

Duncan John Forbes

Peter Jeremy Anslow

Piers James Dawe

Gordon D Henshall

Martin J Birch

George J Cannell

Douglas W Fisher

Robert W Scarr

Alan T R Briggs

H D Wade Macleod

Stephen Richard Foster

A method of encrypting an optical communications signal involves determining an encryption function, filtering an electrical input signal using the encryption function to generate an encrypted electrical signal, and modulating an optical source using the encrypted electrical signal to generate a corresponding encrypted optical signal. This is then transmitted through an optical communications system. The encryption is selected such as to substantially remove symbol definition from the optical signal. This method provides digital signal processing of an electrical input signal in order to derive a signal for controlling an optical modulator in such a way that the optical signal transmitted over the link is a continuous analogue signal rather than a series of discrete symbols which alternate between well-defined signal values. This makes it difficult for a third party to derive the binary bit sequence encoded by the optical signal.

Data security in optical communications systems

A method of transmitting packet traffic between first and second network nodes in a shared protection optical transmission network, the method comprising defining first and second traffic paths between said nodes, at least one of said paths being a shared protection path, and allocating traffic along said paths utilising link aggregation.

Load sharing nodes in a network utilising shared optical protection

An optical communications system has a transmitter which uses modulation using multiple level phase and/or amplitude modulation, and is adaptable to provide modulation for different signals using different selections of the multiple levels. A receiver is able to perform demodulation from the multiple level phase and/or amplitude modulation, and is adaptable to provide demodulation of signals modulated using the different selections of the multiple levels. This provides an adaptive modulation system, so that different bit rates can be employed for different links.

Optical communication system

A system for monitoring a communications network generates a total value figure, using a store of value information. The system can identify which of the monitored flows of traffic rely on a given one or more of the components of the network, and generate a total value of all the identified flows. This type of value information can be easier for network operators to interpret because the information is more direct, and more explicit. Also, many specific rules/warnings about reconfigurations need not be provided. Values can be sent to remote field workers, or used for network configuration, network planning, and financial reporting.

Determining and using value of traffic relying on a given component of a communications network

A system for hybrid electronic/photonic switching of traffic in a node of a communications network includes a plurality of interfaces; an electronic cross-connect (EXC); and a photonic cross-connect (PXC). Each interface is designed to translate a respective traffic stream between corresponding electronic and optical signals. The EXC selectively maps an electronic signal through a selected one of the interfaces, and the PXC selectively couples an optical signal between the selected interface and a selected one of at least two optical channels of the communications network.

Hybrid photonic/electronic switching in a multi-channel network

To provide improved protection bandwidth efficiency for a fast recovery from a fault in an optical network, a protection ring for sharing between some of the protection paths has a pre-configured route so as to overlap on a given one of the links, with other protection paths or other rings. A selector for the given link selects which of the overlapping secondary paths is allocated to the given link at any time. Thus, two types of sharing of protection paths are combined to achieve more efficient use of protection bandwidth. The link selector can be controlled locally and so can operate more rapidly. The local control, essentially independent of the switches used to set up the secondary path through the network, makes the combination easier to scale to larger, more complex networks than shared rings alone.

Constrained optical mesh protection for transmission systems

An optical switch comprising switching means arranged to switch an optical signal by redirection of the optical beam path of said signal, wherein said optical switch is arranged to misalign the optical beam path so as to provide a predetermined optical output power. Thus a switch can be directly used to attenuate a signal, instead of utilising separate attenuators.

Optical switch attenuator

An optical switch comprising two segments at least partially separated by a surface that is partially reflective and partially transmissive to the optical signals being switched, each segment having at least one optical input and at least one optical output, the segments being arranged such that an optical signal can be switched from said input to said output by reflection from said surface, with the optical signal that is generated by transmission through said surface being directed to an output of the other segment.

Optical switching device

A method and apparatus suitable for testing the operation of a photonic switch are described. The photonic switch includes switching means arranged to redirect (and hence switch) an incident optical signal. Operation of the switching means can be verified by providing a test optical signal arranged to be incident upon the switching means, the test optical signal path being distinct from the switched optical signal path.

Testing operation of a photonic switch

In optical communication switching equipment there is a need to set up optical paths through the switch before there is an optical signal present. The present invention provides an optical switching apparatus comprising: an optical switch having a number of optical paths for switching optical channels; a demultiplexer coupled to said switch; a broadband light source coupled to said demultiplexer which distributes said light in said channels to enable correct alignment of said optical paths.

Optical switch alignment apparatus and method

An optical switch comprising at least two segments, each segment having a respective input and a respective output, arranged such that in use if a first segment is removed, a second segment can operate as a pass-through device.

Distributed optical switching device

The invention provides an improved method and apparatus for detecting the phase difference between a digital data signal and a clock signal. By ensuring that no pulse in the output phase signal is narrow enough to introduce a non-linearity, the present invention avoids a source of non-linearity exhibited in existing phase detectors. In addition, by ensuring that critical timing paths through the circuit contain similar circuit blocks, with similar propagation delays, relative time relationships are preserved from clock and data inputs to XOR inputs. The circuit is therefore largely insensitive to changes in the characteristics of the components so long as they all move together, as they would in an integrated circuit implementation.

Method and apparatus for phase detection in digital signals

The invention seeks to provide an improved, bandwidth-efficient method and apparatus for acquiring and tracking bursts of data, or continuous data, of varying and unpredictable amplitude, extinction ratio, and phase. The system avoids the use of digital signal processing which is not practical at high data signal rates. The system also obviates encoding of the data signal using a line code, thereby extending the existing technology to give a significant increase in data throughput for the same available bandwidth. The system may treat acquisition of each data burst, comprising alternate synchronisation parts and data parts, ab initio.

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Ongar, United Kingdom

Adrian Paul Sparks