Abstract: A system and method for operating a plurality of eVOAs in an optical network is provided. The system comprises a number of eVOAs, each eVOA coupled to one or more optical taps and connected to a microcontroller. The microcontroller comprises a monitor signal processing controller for measuring the power of the optical signal at the eVOAs; a scheduler for continuously cycling and checking the eVOAs operating attenuations; a microprocessing controller for determining, setting, adjusting and updating the eVOA operating attenuation and a means for communications between the microprocessor and the other controller within the system. The microcontroller cycles through the plurality of eVOAs and controls one eVOA at a time according to a predetermined method of the eVOA operation. Individual eVOAs may be controlled according to the same or different methods of controlling operations thereof as required.

Abstract: This invention describes a method for controlling attenuation for a variable optical attenuator (VOA) inserted in an optical path of an optical signal propagating in an optical network, comprising the steps of measuring power of the optical signal at the VOA; comparing the measured power with a target power; and if the measured power differs from the target power, changing the attenuation of the VOA in one or more variable size intervals (VSI) so that the power of the optical signal substantially equals to the target power, wherein the VSI being a function of the measured power and target power.

Abstract: A method and apparatus are provided for improving redundancy and load sharing in control cards in the control plane of a communication node. An active control card which receives a request passes the request to the inactive control card for processing if and only if the inactive control card is synchronized with the active control card and the inactive control card is able to process the request. Redundancy and load sharing are further improved if the active control card separates the processing of managing the request and the determination of a response to the request onto separate processors on the control card. In one embodiment, the control cards are OSPF modules in a router. Redundancy is effected by more accurately synchronizing the link state database of each OSPF module, and by allowing the state of each neighboring router to be determined only by the active OSPF module and not independently by any inactive OSPF module.

Abstract: A packet routing/switching system and method are provided by which label switched routing is performed within a hierarchy of LSP/FA-LSPs defined/provisioned in a network of interconnected nodes. Rather than transmitting an entire label stack with an LSP label for each LSP/FA-LSP in the hierarchy, at a given node in the network, a single LSP label is transmitted together with a components label which contains a list of component identifiers which do not inherently identify LSP/FA-LSPs, but from which the full LSP/FA-LSP labels can be determined locally at each node using previously distributed information described in detail below. The list of component identifiers is a shorthand way identifying to adjacent nodes the identity of the LSP/FA-LSP hierarchy without transmitting the entire LSP labels and thus significantly reducing overhead. The single label which is transmitted is the label of the LSP/FA-LSP of which the given node forms a part.

Abstract: A method for transmission of digital data in a form of data packets through links carrying data packets with error correction, includes the steps of enveloping a sent packet data, first with an error detection scheme, and secondly with an error correction scheme. The error correction applies to both the sent packet data and to the error detection field. If an error in either of these fields occurs, the error correction scheme attempts to correct it. Error correction may fail in which case the packet is dropped. If error correction does not fail, there is still a possibility that there was an error which error correction did not correct correctly, or did not detect at all because the power of the correction scheme was exceeded. In these cases, the error detection scheme provides a method or means to detect such errors and drop the packet. Corresponding interconnect system with error correction, encode and decode for such are also provided.

Abstract: The invention describes a method for traffic management in a packet network using random early marking. For each packet flow, packets are randomly marked at the ingress of the network, while discard of the packets at the egress of the network is performed deterministically, i.e. in accordance with the predetermined rules. The step of random marking includes measuring parameters of the data flow, calculating marking probability by applying a mathematical function to the measured parameters, and generating a mark by applying a random logic function to the calculated marking probability. The packets are dropped at the egress of the network if the corresponding queues where the packets have to be stored are congested or full. A corresponding system for traffic management in packet networks is also provided.

Abstract: In an optical WDM network, each optical channel is modulated with a respective channel identity. Detectors, conveniently at multiplex ports of optical band filters, detect the channel identities of all of the optical channels in an optical signal at the respective points to produce respective channel lists. A network management system determines channel lists for through ports of the optical band filters, identifies matching pairs of channel lists to determine a topology of each node and to identify optical paths entering or leaving each node, and identifies matching pairs of channel lists for these paths to determine an inter-node topology of the network. The channel identity detector points can alternatively be at the optical paths entering or leaving each node.

Abstract: A method and apparatus for performing a fast Fourier transform (FFT) computation on large data sizes in real time is provided. The speed at which a FFT is performed is increased by reducing the number of times a Direct Memory Access (DMA) unit must transfer data between an internal memory and an external memory. This is achieved through an algorithm in which data is imported from the external memory into the internal memory and having the CPU perform several calculations on the imported data before it is exported back to the external memory. The imported data in the internal memory has a structure that results in a reduction of the number of times the imported data is swapped between different layers of the internal memory during the FFT computation. Furthermore, the DMA unit import/exports data between the internal memory and the external memory while at the same time having the CPU perform calculations on other data in the internal memory.

Abstract: An extension of a Link Aggregation Protocol (LAP) over the network allows current Ethernet point-to-point LAPs to operate across a Metropolitan Area Network (MAN). A maximum disjoint path algorithm allows selection of a plurality of alternative end-to-end physical routes between two data terminals. These physical routes share a minimum number of nodes and physical links. End-to-end logical links are then formed by a plurality of successive physical links between nodes containing protocol compatible devices, the physical links being selected based on their physical characteristics such as bandwidth and delay. Multiple logical links can be provisioned, without dedicating, between any two data terminals over the network. The logical links provide the virtual point-to-point links that the edge LAP devices require.

Abstract: Apparatuses and methods are provided for chromatic dispersion compensation of wavelength division multiplexed (WDM) optical signals within an optical add/drop multiplexer (OADM) and especially within a remotely reconfigurable add/drop multiplexer (RROADM). The arrangement is especially useful in metro or regional networks where RROADMs can be dynamically reconfigured to deliver signals from any node to any other node. A dispersion compensation module (DCM) is located in the multiplexed through path of the RROADM between the drop module and the add module such that only wavelengths passing through the RROADM are compensated and shorter optical paths traversing only one span between adjacent nodes are not compensated. This allows lower cost static DCMs to be used, allows more flexibility in DCM values and allows fewer DCMs to be used while maintaining dispersion limits.

Abstract: A routing system and method are provided which use a composite cost in identifying routes. This allows a simple way of identifying the best route taking multiple metrics into account for each link simultaneously. The system allows for the inclusion of pruning constraints, and allows for various objectives such as bin packing or load balancing to be achieved.

Abstract: Optical interconnects and methods for wavelength management are provided to interconnect optical rings while overcoming color-blocking and allowing for wavelength re-use within optical rings. The optical inter-connects having a wavelength selective element such as a reconfigurable add/drop demultiplexer (ROADM) and a band-modulo demultiplexer having a free spectral range (FSR) combined with a pool of wavelength conversion resources. More flexible interconnect systems can use a photonic cross-connect (PXC) to allow sharing of a pool of wavelength conversion resources among several optical rings.

Abstract: An apparatus and method for minimizing channel gain excursion in an optical system with automatic gain control is provided. The apparatus includes a feedback control loop which dynamically regulates the target gain of an automatic gain controlled (AGC) amplifier so as to compensate for the action of the AGC amplifier to maintain a constant linear average gain without accounting for the distribution of channels that carry signals across the amplifier spectral gain profile, which causes gain excursion of individual channels. The feedback control loop measures gain of individual channels and uses these measurements to regulate the target gain of the amplifier so as to minimize gain excursion of individual channels. If required, the apparatus may be integrated into a package. In one embodiment, the method for regulating the target gain is to maintain constant gain for all channels irrespective of the number of channels that carry a signal. This method is simple and guarantees no gain excursion.

Abstract: Devices and methods are provided for a re-configurable optical add/drop multiplexer (ROADM) having a static circulator, a selectable grating and a reversible circulator. The use of a reversible circulator in a known optical drop multiplexer configuration allows the selectable grating to be used for selecting both the add-wavelength and the drop-wavelength while maintaining an East/West architectural split to allow for SONET compliant maintenance. This invention provides a cost-effective enhancement to a duplex reflective wavelength selective ROADM.

Abstract: A method and system for determining location and value of dispersion compensating modules (DCMs) in an optical network is provided. The method comprises evaluating possible DCM values and locations and successively adding selected combinations to the network until the dispersion limits of the network are met. This systematic method is applicable to a variety of network topologies. In one embodiment, the method for determining the location and value of the DCMs uses the amount of compensated effective dispersion over all lightpaths that pass through the DCM to select the combinations. In another embodiment, the method is repeated a number of times with different selections of DCM value and location combinations, and the method providing the least number of DCMs and the lowest DCM values is chosen.

Abstract: In a WDM optical network, optical components of optical add/drop multiplexers (OADMs) at different nodes are made independent of the optical channel wavelengths to be dropped and added. Groups of optical channels each comprise a respective channel in each of a plurality of optical bands of channels having adjacent wavelengths, and the OADMs use tunable optical filters to drop and add channels in a selected group. A remote source supplies unmodulated optical carriers at channel wavelengths via an optical carrier fiber to each node, and at least one, conveniently all, of the optical carriers in a respective optical band is/are modulated with a signal to be transmitted via the add filter.

Abstract: A digital signal processor DSP for bit-reversal of a large data array of a size has a direct memory access (DMA) controller for performing in-place bit reversal routines on an external memory during a first stage, and a central processing unit (CPU) for swapping small sub-arrays on internal memory in a second stage. The two stage method according to the invention importantly reduces the real-time implementation for sorting large size data arrays on uni-processor DSP platforms, by extensively using the external memory and avoiding a random access to the internal memory. As well, the invention provides for improved dense integration and reduced costs when used in dense wavelength division multiplexing (DWDM) systems.

Abstract: The present invention provides an all-optical dynamic gain equalizer of an open-loop design using nonlinear optical materials for equalizing channel power without the need of complex electronics and close-loop control, and provides pulse reshaping and in some embodiments noise reduction at no extra cost. The invention achieves restoration of spectral power uniformity by employing nonlinear optical limiters with desirable power transfer function curves to each of the optical signals to be equalized. The invention provides the highly desirable functions of dynamic gain equalization, and optical pulse reshaping. Some embodiments constructed according to the invention provide signal dynamic range control by biasing the nonlinear optical limiter with a biasing optical signal.

Abstract: Methods and components are provided which ensure both the improved use of network resources and adequate performance of best effort (BE) traffic by intelligently distributing the BE traffic demands at connection level with corresponding scaling weights, and without reserving bandwidth. A weighted sum of the best effort (BE) class connections (or LSPs in MPLS context) in a link is used as a path selection criterion, where each BE connection is weighted by its service volume. Path selection for a requested BE service volume is performed by creating a virtual topology in which all links in a network have weighted BE metrics updated to include the effects of the requested BE service volume, and identifying a best path through the virtual topology taking into account the weighted BE metrics.

Abstract: A method for determining optimal locations and values of dispersion compensating modules (DCMs) in an optical network is provided. The method comprises repeatedly evaluating possible combinations of DCM values and locations and adding to the combination having the lowest score until a solution of DCMs is formed that satisfies the dispersion limits of the network. This method provides an optimal solution with, for example, the lowest value of DCMs necessary to meet dispersion specifications. In one embodiment, the method for determining the optimal location and value of the DCMs uses a priority queue to store the different combinations of DCM values and locations. Modifications to the method include variations in the score function, for example to minimize the total cost of the DCMs. In another embodiment, a series of priority queues are used to improve the efficiency of the method by reducing the amount of processing required to sort the priority queues.