Abstract: A photonic switch uses a cost-effective DWDM optimized switch architecture allowing the introduction of DWDM into the metro network. In order to implement this architecture cost-effective ways of implementing the optical carrier frequency/wavelength precision required for a Dense Wavelength Division Multiplexing 100 GHz or 50 GHz on-grid solutions are needed. The photonic switch acts as an intermediary between the WDM density of the access portion of the metropolitan photonic network and the DWDM density of the core photonic network. The metro photonic switch introduces optical carriers that are all generated in the photonic layer adjacent to it and allocates them out to the photonic access nodes for modulation. This has the advantage of providing the optical carriers to be modulated from a centralized highly stable and precise source, thereby meeting the requirements for DWDM carrier precision, whilst generating these carriers in relatively close proximity to the modulators.

Abstract: A communications signal which carries a purely digital wrapper signal and a method and system for generating it and extracting overhead information therefrom. The wrapper signal can be received by a high-performance format-specific receiver at the end of the network as part of the overall payload, but can also be detected by a low-bandwidth payload-bit-rate-insensitive receiver at an intermediate node. This is achieved by using alternating payload and wrapper segments and providing special digital coding on the wrapper segments. Specifically, each wrapper segment consists of a contiguity of signal level sequences, each of which is a multi-bit symbol that encodes a bit in the overhead bit stream. Each of the symbols is thus a signal level sequence having one of two possible transition patterns, with the appropriate symbol being chosen depending on whether the overhead bit is a logic “zero” or a logic “one”.

Abstract: A variable dispersion compensation to a signal for compensating dispersion present in an optical signal. The invention can be embodied in a dispersion discrimination and compensation system comprising a feedback loop for regulating an amount of dispersion compensation applied by a controlable anti-dispersive element (CADE) to an incoming optical signal. To that effect, the feedback loop comprises a dispersion discriminator for accepting a portion of a signal outgoing form the CADE and to provide a measure of a dispersion characteristic to a processor which controls the amount of dispersion compensation applied by the CADE. The dispersion discrimination and compensation system can be stand-alone or integrated into an optical switch. Furthermore, dispersion compensation can be provided to multichannel optical signals or to partially or totally demultiplexed optical signals.

Abstract: The photonic network of the present invention uses a cost-effective DWDM optimized switch architecture allowing the introduction of DWDM into the metro network. In this invention the optical carriers are all generated in the photonic layer at the edge photonic switching node and are allocated out to the photonic access nodes or central core data switch for modulation. This has the advantage of providing the optical carriers to be modulated from a centralized highly stable and precise source, thereby meeting the requirements for DWDM carrier precision, whilst generating these carriers in relatively close proximity to the modulators. Sparse WDM components can be used in the access portion of the network without adversely affecting the ability of the signal to transit the DWDM portion of the core network, since the optical carrier frequency is fixed at the centralized source and is unaffected by these components.

Abstract: A protection arrangement for an optical switching system includes protection switching for switch planes in the optical core and for ports in the tributary cards. For a multiple layer switch core protection is also provided between layers. A first layer is for switching optical channels. The protection switches used may be 1×N, 2×N or 3×N MEMS optical switches. The 1×N MEMS provides for protection switching. The 2×N MEMS provides protection switching and testing capability. The 3×N MEMS provides for protection switching, testing and backup of the protection switching. Application of these protection switches is shown in lambda plane switch cores, multiple layer switch cores and combined switch cores.

Abstract: A system for detecting dispersion in an incoming optical signal centered about a channel center frequency. The system includes a splitter unit for separating the incoming signal into first and second groups of signals. The system further includes a first compensation region adapted to apply a desired positive dispersion characteristic to a signal in the first group and a second compensation region adapted to apply a desired negative dispersion characteristics to a signal in the second group. The splitter also includes a receiver unit connected to the first and second compensation regions, and adapted to compare the received signals and to detect the dispersion in the incoming optical signal on the basis of the comparison. The system can be selectively balanced at different optical frequencies by varying the amount of dispersion applied by the first and second compensation regions.

Abstract: An optical switching system includes multiple layers for switching optical signals. A first layer is for switching optical channels. A second layer is for switching groups of optical channels. A third layer is for switching composite optical signals. Between layers demultiplexing and multiplexing of signals allows switching within a single switch core at any level from fiber to wavelength group to optical wavelengths. Optical amplifiers between layers compensate for losses within the switch and within demultiplexers and multiplexers. One configuration provided additional multiplexing and demultiplexing to allow direct connection between the first and third layers. Another configuration shares optical switching matrices between the first and third layers.

Abstract: An optical switch is equipped with a set of optical intensity controllers at its input, each intensity controller being driven to vary a corresponding WDM input traffic signal with a low power test signal. The switch is also equipped with optical splitters at its output and a path integrity analyzer connected to the splitters and to the intensity controllers. The path integrity analyzer generates or controls generation of the test signals applied by the intensity controllers. The path integrity analyzer also receives the tapped portions of the WDM output signals and separates them into their single-carrier components in order to recover a set of switched single-carrier optical signals. The path integrity analyzer is further provided with test signal detectors used to detect the presence of a test signal in each recovered switched single-carrier optical signal.

Abstract: A system for detecting dispersion in an incoming optical signal centered about a channel center frequency. The system includes a splitter unit for separating the incoming signal into first and second groups of signals. The system further includes a first compensation region adapted to apply a desired positive dispersion characteristic to a signal in the first group and a second compensation region adapted to apply a desired negative dispersion characteristics to a signal in the second group. The splitter also includes a receiver unit connected to the first and second compensation regions, and adapted to compare the received signals and to detect the dispersion in the incoming optical signal on the basis of the comparison. The system can be selectively balanced at different optical frequencies by varying the amount of dispersion applied by the first and second compensation regions.

Abstract: A photonic switch uses a cost-effective DWDM optimized switch architecture allowing the introduction of DWDM into the metro network. In order to implement this architecture cost-effective ways of implementing the optical carrier frequency/wavelength precision required for a Dense Wavelength Division Multiplexing 100 GHz or 50 GHz on-grid solutions are needed. The photonic switch acts as an intermediary between the WDM density of the access portion of the metropolitan photonic network and the DWDM density of the core photonic network. The metro photonic switch introduces optical carriers that are all generated in the photonic layer adjacent to it and allocates them out to the photonic access nodes for modulation. This has the advantage of providing the optical carriers to be modulated from a centralized highly stable and precise source, thereby meeting the requirements for DWDM carrier precision, whilst generating these carriers in relatively close proximity to the modulators.

Abstract: In a communications network comprising a plurality of interconnected nodes, each node comprises at least one network device requiring allocated transmission channels, a switch connected to the network device for configuring transmission channels connected to other nodes, and a configuration controller connected to the network device and to the switch for controlling configuration of the transmission channels. The configuration controller receives signals from the network device indicative of traffic load on the network device, processes the received signals to determine that reconfiguration of the transmission channels is favoured and determines a favoured reconfiguration of the transmission channels.

Abstract: A switch for optical signals, including a plurality of external inputs, a plurality of external outputs, a wavelength conversion entity and a plurality of core switching entities. Each core switching entity is associated to a respective set of at least two wavelengths. The approach is based on switching groups of at least two wavelengths in each core switching entity, while still maintaining per-wavelength switching granularity but sharing the provided capacity for wavelength conversion connections across the group. Thus, wavelength conversion resources assigned to a group of wavelengths are usable by any wavelength in that group. In this way, the blocking statistics in the node as a whole are improved with respect to a single-wavelength-plane configuration. In addition, the resulting switch is modular as it can be upgraded by adding or removing one or more switching modules as required.

Abstract: A switching unit, equipped with a plurality of port cards and a plurality of switch cards connected in a non-parallel fashion to the port cards. Each port card has a first M-way commutator and a second M-way commutator, wherein the total number of first M-way commutators over all the port cards is N and wherein the total number of second M-way commutators over all the port cards is also N. Each switch card has a first N-way commutator and a second N-way commutator, wherein the total number of first N-way commutators over all the switch cards is M and wherein the total number of second N-way commutators over all the switch cards is also M. Each switch card further has a unit for controllably time switching a plurality of signals output by each first N-way commutator and providing a plurality of switched signals to the corresponding second N-way commutator.

Abstract: A photonic switch uses a cost-effective DWDM optimized switch architecture allowing the introduction of DWDM into the metro network. In order to implement this architecture cost-effective ways of implementing the optical carrier frequency/wavelength precision required for a Dense Wavelength Division Multiplexing 100 GHz or 50 GHz on-grid solutions are needed. The photonic switch acts as an intermediary between the WDM density of the access portion of the metropolitan photonic network and the DWDM density of the core photonic network. The metro photonic switch introduces optical carriers that are all generated in the photonic layer adjacent to it and allocates them out to the photonic access nodes for modulation. This has the advantage of providing the optical carriers to be modulated from a centralized highly stable and precise source, thereby meeting the requirements for DWDM carrier precision, whilst generating these carriers in relatively close proximity to the modulators.

Abstract: A dispersion discriminator and method for determining the amount of dispersion in an optical signal. The discriminator includes first and second dispersion arms for causing first and second additional amounts of dispersion to be added in first and second portions of the optical signal, respectively. The first and second additional amounts are of opposite polarities and preferably of substantially equal magnitude. The discriminator includes a detector capable of receiving the first and second portions of the optical signal from the arms; detecting, for each of a plurality of frequencies, a difference in a characteristic of the first and second portions; determining a particular frequency at which the difference falls outside a predetermined range; and mapping the particular frequency and the difference at that frequency to a magnitude of dispersion in the optical signal.

Abstract: A cross-connect switch for switching optical signals, in particular, Dense Wavelength Division Multiplexed (DWDM) signals is disclosed. The switch includes a switching matrix for each of the predetermined wavelengths of the DWDM signals. The switching matrices include Micro-Electro-Mechanical (MEM) systems which have optically reflective elements, typically mirrors, arranged in rows and columns for switching an incoming optical signal travelling along a row of such elements to an output port aligned with a column of the elements. The switch has input demultiplexers to split an incoming DWDM signal into its component channel wavelengths, each of which is directed to a switching matrix where it is switched to an output port and recombined into an outgoing DWDM signal by a multiplexer before being transmitted out of the switch. A wavelength-converting switch, connected across the switching matrices, is also included for switching channels between wavelengths.

Abstract: A cross-connect switch for switching optical signals, in particular, Dense Wavelength Division Multiplexed (DWDM) signals is disclosed. The switch includes a switching matrix for each of the predetermined wavelengths of the DWDM signals. The switching matrices include Micro-Electro-Mechanical (MEM) systems which have optically reflective elements, typically mirrors, arranged in rows and columns for switching an incoming optical signal travelling along a row of such elements to an output port aligned with a column of the elements. The switch has input demultiplexers to split an incoming DWDM signal into its component channel wavelengths, each of which is directed to a switching matrix where it is switched to an output port and recombined into an outgoing DWDM signal by a multiplexer before being transmitted out of the switch. A wavelength-converting switch, connected across the switching matrices, is also included for switching channels between wavelengths.

Abstract: A chromatic dispersion discriminator for determining the amount of chromatic dispersion in optical signals used by optical transmission systems is described. The discriminator provides a means of detecting the polarity and magnitude of dispersion in optical signals received over a dispersive optical link, thereby allowing the correct amount of dispersion compensation to be applied to each optical signal.

Abstract: An optical wavelength plan for metropolitan photonic networks uses a cost-effective DWDM optimized architecture allowing the introduction of DWDM into the metro network. In order to implement this architecture cost-effective ways of implementing the optical carrier frequency/wavelength precision required for a Dense Wavelength Division Multiplexing 100 GHz or 50 GHz on-grid solutions are needed. The optical wavelength plan provides WDM density to the access portion of the metropolitan photonic network and DWDM density to the core photonic network. The optical wavelength distribution methods allocate wavelength in the access network in order to optimize non-blocking traffic throughput to the core network.

Abstract: The invention is an optical network unit (ONU) connectable between an optical fiber and a plurality of twisted pairs, the optical fiber carrying downstream traffic elements from a host digital terminal (HDT) to the ONU, each downstream traffic element having a header and a body, the header indicating a destination twisted pair and a service type associated with the traffic element. The ONU comprises means for determining, from the header of each traffic element, the service type associated with the traffic element; means for determining, from the header of each traffic element, the destination twisted pair associated with the traffic element; and means for processing the traffic elements and transmitting at least the body of each traffic element to the associated destination twisted pair in a data format dependent on the associated service type.