Abstract: An optical network includes a plurality of subnets. The subnets each include a plurality of add/drop nodes coupled to the optical ring and operable to passively add and drop traffic to and from the optical ring. The network further includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets and to provide protection switching.

Abstract: An optical network includes an optical ring and at least three subnets. Each subnet includes a plurality of add/drop nodes coupled to the optical ring. The add/drop nodes are operable to passively add a first traffic stream in a first direction on the optical ring and a second traffic stream in a second direction on the optical ring. The first traffic stream comprises different content than the second traffic stream, and the first traffic stream and the second traffic stream are transmitted on the same wavelength. The network also includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and are operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets.

Abstract: A bit-rate-transparent electrical space-division switching matrix is employed in an optical cross-connect and the input/output stage is constructed from simple, broadband optical receivers and transmitters. Since the switching matrix operates in unclocked manner, i.e. its switching function is not based on internal bit timing and frame timing, arbitrary signals can be switched though transparently at almost any bit rate, independently of the protocol-type being used. The inputs and outputs likewise operate fully independently of bit rate and protocol, since they only implement an O/E conversion or O/E conversion. By virtue of this structure, a simply constructed but extremely powerful optical cross-connect is created that can be employed equally for all types of optical signals within the stipulated wavelength-range.

Abstract: A network is protected against interruption of service while one or more faulty switches or optical fiber transmission lines are repaired or replaced, by an interconnecting configuration of small N×N optical input/output switches, where N is 2 or greater than 2. The switches are configured among protection and working transmission lines. The small number of fibers for each switch improves repair and installation connection reliability and permits configurations that flexibly meet differing requirements. Also the fault is monitored with a fault check signal.

Abstract: A protection switching architecture is used in a telecommunications system such as a wavelength division multiplexed (WDM) telecommunications system to replace a failed transmission line or a failed wavelength processing device. A spare wavelength processing device transmitter replaces a failed service wavelength processing device transmitter. A spare transmission line replaces a failed service transmission line. A spare wavelength processing device receiver monitors the optical signals, one wavelength at a time, on either the spare transmission line or the service transmission line and replaces one of the service wavelength processing device receivers. Wavelength selection equipment routes either the service transmission line or the service transmission line to the service wavelength processing device receivers and selects wavelengths to be monitored by the spare wavelength processing device receiver.

Abstract: The method of pre-configuring the optical protect paths in an agile photonic network establishes a protection trail for each optical working path that may be set-up in the network. The pre-configuration is based on building an electrical layer (EXC) graph that takes into account all the connection demands in the network, and finding on this EXC graph a plurality of cycles. Next, the EXC cycles are validated at the optical layer, and are further validated against constraints. The method attempts to find an optimal cycles solution, without exhausting all possible variants.

Abstract: Optical amplifier which can eliminate the need for an optical detection section before an external attenuating medium, can prevent SN degradation, and can reduce power required for pumping light. An attenuation amount detection section detects an amount of signal light attenuation caused by a variable optical attenuator and the external attenuating medium connected in series, by means of a front optical detection section provided before the variable optical attenuator and the external attenuating medium and a back optical detection section provided thereafter. An attenuation amount control section controls the variable optical attenuator such that the amount of signal light attenuation detected by the attenuation amount detection section is kept constant. A connection detection section detects a connection or disconnection of the external attenuating medium in accordance with the amount of signal light attenuation obtained when the amount of attenuation caused by the variable optical attenuator is minimized.

Abstract: A monitoring system includes first and second evaluation sections for obtaining an averaged Q-factor parameter and a waveform distortion parameter from an optical signal amplitude histogram collected from optical signals under measurement. The monitoring system further includes a third evaluation section for determining both averaged Q-factor parameter and waveform distortion parameter, and for making a decision as to whether the main factor of the optical signal quality degradation is waveform distortion or not by comparing the averaged Q-factor parameter and waveform distortion parameter with their initial values or initial characteristics which are obtained when no optical signal quality degradation is present.

Abstract: The position and amount of localized polarization dependent anomalies such as polarization mode dispersion and/or polarization dependent loss may be measured by applying a polarization modulated probe signal to an optical transmission line. The polarization modulated probe signal is returned via optical feedback paths positioned along the line, and is detected by a probe signal receiver to identify the position and strength of the anomaly.

Abstract: A method, apparatus and computer program are disclosed for managing the distribution of optical power to a plurality of optical data devices. The devices can be data storage drives, data replicators, fast optical search devices, or other components that use optical or laser power for their operation. A power management system provides the increased flexibility of monitoring and redirecting optical power (e.g., to provide higher or lower power on demand), which increases the fault-tolerance and performance (e.g., through higher data transfer rates) of a data management system.

Abstract: A method, a system and a module are proposed for detecting and locating faults in an optical multi channel network composed of network nodes. The method includes assigning different sub-carrier pilot tones to a number of the nodes comprising Network Elements (NE), applying the different sub-carrier pilot tones to any signal added to the network via the respective nodes, checking presence of one or more of the sub-carrier pilot tones at one or more points of the network, and, based on results of the checking, locating a faulty section of the network in case a fault occurred.

Abstract: The spectrum of a received WDM band or subband is analyzed to detect failure of, e.g., fiber or amplifiers along a line. In one implementation, measurements are taken within the optical spectrum at locations of expected data-carrying optical signals and at two locations just outside the wavelength range occupied by these signals. Magnitudes of adjacent measurements are compared to obtain differences. If none of the differences exceed a threshold, a fault may be determined.

Abstract: Method and apparatus for fault localization in an optical network using time trend correlation of end node performance parameters and intermediate node performance parameters, such as QoS and quasi-Q factors, respectively. The method and apparatus are bit-rate and protocol independent, enabling testing for each channel of a diverse dense wavelength division multiplexed traffic system using a single set of hardware.

Abstract: A method for diverting communication traffic in an optical network from a first optical link extending between a first and a second locations, to a second optical link extending either directly between the first and the second locations or via a third location, which method comprises the steps of switching traffic at said first location from said first optical link to said second optical link. After determining at the second location that traffic has not been received along the first optical link for a pre-determined period of time, traffic is diverted at the second location to the second optical link.

Abstract: A method and system for multi-level power management in an optical network is provided. They include three levels of power management. The first level of power management dynamically changes equipment settings in each module of equipment so that required module setpoint values in each module are achieved. The second level of power management determines module setpoint values for each module of equipment within each node in the optical link so that required node setpoint values are achieved. The third level of power management determines node setpoint values at each node in the optical link so that the optical link meets predetermined power specifications. If any of the three levels cannot achieve the required setpoint values, an error signal is generated by that level of power management and sent to the level of power management above it, thus initiating a higher level of power management.

Abstract: If a repeater supervisory control (SV), a pre-emphasis automatic adjustment (PE), a receiving side threshold value automatic adjustment (Vth), a transmitting side dispersion compensation value setting (VDC(T)), and a receiving side dispersion compensation value setting (VDC(R)) are executed for an optical main signal, these controls are executed in the above described priority order. Accordingly, if the controls are independently executed, or if two or more controls simultaneously occur, a control with a higher priority is executed. In this way, a transmission quality of an optical signal is prevented from being badly influenced as a result that the controls are simultaneously executed.

Abstract: A system for detecting faults in an optical network having switching nodes and amplifier nodes is provided. According to one aspect of the system, one or more amplifier nodes are coupled between two switching nodes. Each amplifier node is capable of detecting a fault condition, such as a loss-of-signal (LOS) condition, on an incoming line. Upon detecting the LOS condition, the amplifier node generates a fault report which is then forwarded to a switching node. The switching node uses information from the fault report to initiate switching actions, if any, to restore traffic. According to another aspect of the system, each amplifier node is configured to receive a fault report received from another amplifier node and forward such fault report to a switching node. Each amplifier node is further configured to prioritize a fault condition identified in a fault report received from another amplifier node and the fault condition detected on its incoming line.

Abstract: A system and method for forwarding fault information in an optical network is disclosed. Responsive to a fault being detected at a node, the fault information is forwarded to the destination node in the form of a loss-of-signal condition by turning off laser transmitters used to propagate the signal towards its destination. Thus, a node or other network element not capable of generating an alarm signal consistent with an established alarm signaling protocol, such as a SONET alarm indication signal (AIS) or an SDH multiplexer section alarm indication signal MS-AIS, may still forward the fault condition to a downstream element.

Abstract: A wavelength division multiplex transmission system with substantial functions for avoidance of defects is provided. The system comprises an optical transmission device and an optical receiving device. The optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit, and distributes transmission signals to be transmitted among a plurality of wavelength components, converts the signals into WDM signals, and transmits the WDM signals to a WDM transmission network. The optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit, and restores WDM signals from the WDM transmission network into transmission signals.

Abstract: The invention is systems and methods for determining a fundamental route between central offices in a telecommunications network. The invention receives a “request for service” as location names or location information associated with the two selected locations. The location names or location information are correlated with one or more corresponding SONET carrier identification codes (SCID). If the two selected locations have intermediate locations between them, the invention determines a set of intermediate locations. Location information associated with each intermediate location can then be correlated with one or more corresponding SONET carrier identification codes (SCID). A set of routes can then be generated between the two user-selected locations, including routes between locations and sub-locations, and between sub-locations, each based upon fundamental route criteria.

Abstract: A method is provided for using optical time-domain reflectometry (OTDR) with a bi-directional optical transmission system that includes a plurality of terminals interconnected by first and second unidirectional optical transmission paths having at least one repeater therein. The method begins by transmitting a probe signal from a first terminal through the repeater over the first optical transmission path. A returned OTDR signal is received over the first optical transmission path in which status information concerning the first optical transmission path is embodied. The returned OTDR signal is transformed to a digitized electrical signal and the digitized electrical signal is transformed to an optical data signal. Finally, the optical data signal is transmitted over the second optical transmission path to the first terminal for extracting the status information embodied therein.

Abstract: A bit-rate-transparent electrical space-division switching matrix is employed in an optical cross-connect and the input/output stage is constructed from simple, broadband optical receivers and transmitters. Since the switching matrix operates in unclocked manner, i.e. its switching function is not based on internal bit timing and frame timing, arbitrary signals can be switched though transparently at almost any bit rate, independently of the protocol-type being used. The inputs and outputs likewise operate fully independently of bit rate and protocol, since they only implement an O/E conversion or O/E conversion. By virtue of this structure, a simply constructed but extremely powerful optical cross-connect is created that can be employed equally for all types of optical signals within the stipulated wavelength-range.

Abstract: A communication network includes first and second terminals, nodes, and links. The first node is coupled to the first terminal through the first link, and coupled to the second terminal through the second link and the second node. The first node preferably includes communication paths, each coupled to one corresponding first link and to the second link, through a multiplexing device, and routing signals between the links. The first node also preferably includes an alternate communication path coupled through the multiplexing device to the second link, a switch coupled to the alternate path, and a detector detecting failure of a communication path. A controller is responsive to the detector detecting a failure in a communication path and controls the switch to couple the alternate path to a corresponding first link, thereby enabling a signal to be routed between that first and second links through the alternate path.

Abstract: The present invention implements open fiber control in an optical transceiver. During normal operation, the transceiver transmits signals through a connection to an optical network. When the connection is intact, the total power transmitted can be greater than the eye-safety limit. When the connection breaks, the transceiver detects the loss of signal and disables transmissions over all channels except for one. The transceiver continues transmission on the single enabled channel at an eye-safe level. When the connection is fixed and a signal reappears, the transceiver detects the signal reappearance and re-enables all channels that had previously been disabled. By allowing the transceiver to transmit with greater optical power when the connection is intact, an increased data rate and longer transmission distances can be achieved. At the same time, safety is preserved, because transmissions drop to acceptable power levels whenever a break is detected.

Abstract: A method is provided for isolating faults in an optical network having a plurality of partial regenerators. The method includes: transmitting an optical signal through the optical network; determining an error rate for the optical signal at an egress point of the optical network; sequentially introducing a dither control signal into the optical signal at each of the plurality of partial regenerators; and monitoring the error rate for the optical signal at the egress point of the optical network; thereby isolating where a fault occurs in the optical network.

Abstract: An optical transmission device in which optical signal switching is performed to allow the device to be reduced in size and also which is capable of efficient recovery from fault, thereby improving system expansibility and communication quality. Overhead terminating section converts an optical signal to an electric signal and performs an overhead process including extraction of fault information and setting of status information. Optical switch section performs a process of switching the optical signal between active and standby lines, and switching control section provides a switching command to the optical switch section in accordance with the fault information.

Abstract: A method for the protection of fiber optic ring-shaped transport networks, the networks including network elements connected by spans, optical paths being installed between the network elements, the method including the steps of providing each network element with information concerning the network architecture; providing each network element with information concerning configuration data of the network elements; providing each network element with information concerning criteria for triggering the mechanism; establishing an information exchange protocol comprising a set of messages and of rules; establishing a traffic rerouting method, wherein the configuration data include the ring map, the traffic map, the wavelength and the bit rate concerning every path.

Abstract: Methods and apparatus for detecting degradation of a fiber optic connector. In a preferred embodiment, the method includes transmitting a optical pulse in a first direction along the fiber optic cable such that a first portion of the optical pulse is either absorbed or reflected by the degradation. The method also includes determining the degradation's location within at most two connectors of the cable based on the first portion of the optical pulse. If the at most two connectors is two connectors then the method includes transmitting a second optical pulse in a second direction along the cable so that a portion of the second optical pulse is either absorbed or reflected by the degradation. A determination is made of the location of the degradation within one of the two connectors based on the first portion and the second portion of the optical pulses.

Abstract: In a router with redundant central arbiters, a set of control processors (CPs) determines which arbiter is active, which is standby, and when to switch between them. In normal operation ingress ASICs issue requests to the active central arbiter ASIC and keep-alive requests cyclically once per chunk period to the passive arbiter ASIC, which then returns keep-alive grants through the same links to the ingress ASICs and sends standby configuration information to the optical switch ASICs. The arbiter ASICs pass a switch-over decision simultaneously to the optical switch ASICs and ingress ASICs, which empty all queues of outstanding requests, and then resend all of those requests to the new active central arbiter after all queues are empty, such that no router traffic is lost. Mechanisms ensure that during the transition the ASICs properly recognize which data links are healthy and which arbiter is active.

Abstract: A branch unit for a fiber optic system that includes a service path and a protection path, whereby the branch unit provides switching to account for problems due to fiber cuts and/or equipment failures that may occur in the fiber optic system. The service and protection paths meet at a branch point of the fiber optic network, or at a network protection equipment (NPE) that is located near a customer interface equipment. A plurality of switches are provided at the branch unit or NPE, along with a detector and a processor, to determine whether any signals are being received from the service path, and if not, to reconfigure the system to accept signals from the protection path.

Abstract: The detection light reflection function is given to PLC type LD, PD or LD/PD modules having light guides and optoelectronic chips (LD, LED, PD or APD) by forming a grating on the light guides which selectively reflects only the detection light.

Abstract: An on-chip parallel data generator, including a Built In Self Test (BIST) generator, is integrated into a laser driver array of a parallel optical communication transmitter so that all optical outputs switch simultaneously. The BIST generator requires only one clock input which clocks the BIST generator for all channels. The optical outputs respond to either the on-chip BIST generator or the electrical inputs if a valid signal is present on the inputs.

Abstract: To automate fiber connectivity management in optical systems, a dedicated low bit-rate communications channel unique to each fiber connection in an optical system is provided. The dedicated communications channel simplifies fiber connectivity management by supporting the exchange of port identification information from one optical component to another after which processing determines if the specific connection is a desired association. The dedicated communications channel supports optical interconnection surveillance for all card-to-card optical connections within a group of related cards or within an optical network link. Automating fiber connectivity management in this manner will enhance future products by simplifying the fiber connection validation process and ensuring that any specific connection between optical components is the required association.

Abstract: A system and method are provided for transporting FTFL messages in a G.709 network-connected simplex device. The method comprises: receiving messages from a first source in a digital wrapper frame format with overhead bytes in every frame; recovering FTFL information from the received message overhead bytes; and, selectively supplying modified FTFL information for transmit message overhead bytes to the first source. Recovering FTFL information from the received message overhead bytes includes recovering a 256 byte FTFL message, including a 128-byte forward message and a 128-byte backward message.

Abstract: A method of managing a free-space optical network includes monitoring environmental and weather conditions in the vicinity of one or more free-space optical links in the network. Data is gathered by environmental condition instruments, such as visibility meters, and is used to assess whether atmospheric conditions have deteriorated to the point where operation of one or more free-space links might be in jeopardy. If data from an environmental condition instrument falls below a predetermined level, network data traffic is routed over an alternate communication path, which may include radio frequency (RF) paths, fiber optic cables, wire cables, or other free-space links.

Abstract: A signal router is described. The signal router includes a switching matrix, an error detector and a controller. The switching matrix includes a first number of inputs and a second number of outputs, and is configured to receive an information stream. The error detector is coupled to one of the second number of outputs, and is configured to generate error information by virtue of being configured to detect errors in the information stream. Likewise, the controller is coupled to the switching matrix and error detector. The controller is configured to select one of the first number of inputs, receive error information from the error detector, and configure the switching matrix to couple the selected input to one of the outputs.

Abstract: A communication path impairment detection module for connection to a duplex optic communication link is provided. The duplex optic communication link includes an outgoing communication path and an incoming communication path, each being characterized by a data channel and an optical service channel. The communication path impairment detection module includes a first port and a second port suitable for coupling to the outgoing and incoming communication paths respectively. The communication path impairment detection module is responsive to impairment of the data channel and of the optical service channel in the incoming communication path to impair the data channel and the optical service channel in the outgoing communication path.

Abstract: In a semiconductor device comprising photo-transceiver arrays constructed on silicon substrates with underlying supporting CMOS circuitry in the substrate interfacing with a source of software control, a method is provided for mapping and reconfiguring the global data transfer channel map of optical interconnect lines and intra-nodal routing links. An initial mapping procedure identifies all possible connections. The silicon circuitry provides for sensing optical connections and light levels, for testing or sensing of routing links, and for controlling gain and power, as well as forming and reforming routing links between detectors and emitters. A rule-based routing, mapping and re-mapping scheme, utilizing over-sampling techniques and effectuated by the silicon circuitry and software, accommodates limited misalignment of mating photo-arrays, faults occurring in data transmission channels after the initial mapping, and provides additional security, performance and power management capabilities.

Abstract: Disclosed is a WDM network which has: a lightwave path which connects between clients and each of which is provided with an overhead, and a sub-network which is defined by dividing the WDM network. In this WDM network, the sub-network has a partial lightwave path to go through the sub-network, the overhead has a partial lightwave path supervisory control information region which is terminated at both nodes of the partial lightwave path, and when a fault occurs on a lightwave path, the fault information of partial lightwave path including the position information of fault occurred is added to the partial lightwave path supervisory control information region of the overhead.

Abstract: Optical communications networks are provided that allow network maintainers to monitor or control subsystems using communications links other than optical telemetry links. The communications links may be wireless links or may be based on any other suitable communications links such as links using Ethernet cables or telephone lines. Network subsystems may be provided that include communications circuitry for communicating over the communications links. A network maintainer may use network control and management software implemented on computer equipment at a different location than the subsystems to communicate with the subsystems over the communications links. Because the communications links may function independently from the optical telemetry channels in the network, new subsystems may be added to the network without disturbing the existing network management software or telemetry arrangement.

Abstract: An arrangement and a method for testing a telecommunications circuit over Dense Wavelength Division Multiplexing (DWDM). A transmitter, which is optically coupled to the circuit, transmits a test-drive signal on the circuit. Through a network, a performance of the circuit is monitored at points along the circuit based on the transmitted test-drive signal.

Abstract: The first step in isolating a soft fault within a transparent network is to determine which OMS trail is causing the fault. This can be accomplished by forcing regeneration at a flexibility point, which permits the estimation of the signal quality using a BER measurement. The preferred mechanism for segmenting Och faults to an OMS/trail is eavesdropping, using dedicated tunable filters and receivers or spare test tunable filters and receivers at network flexibility sites. Once the fault has been isolated to a specific OMS trail, analog tools are used to further isolate the fault down to a single replaceable module or fiber, using rapid measurement and correlation of relevant measured and pre-calculated expected performance data. In case of hard faults, to avoid superfluous alarm reports at connection termination points, the optical channel fault detector provides fault indications to downstream nodes using Forward Defect Indications (FDI) over the optical supervisory channel (OSC).

Abstract: A method for identifying faults in a branched optical network having a central office optically connected to a plurality of optical network units by a plurality of optical paths. The method involves transmitting an optical signal from the central office to the optical network units reflecting a portion of the transmitted optical signal back to the central office. This reflected signal is then used to determine whether a fault exists in the branched optical network.

Abstract: An apparatus and method is disclosed for protecting access to a shared medium in an optical communications system which has plural remote terminals coupled to a central terminal over the shared medium. According to one aspect, if an optical transmitter for an individual remote terminal is active for a first prescribed time interval when it has not been enabled for such transmission, the optical transmitter is disabled. According to another aspect, the continuous time that an individual terminal is enabled to transmit onto the shared medium is monitored. If the enabled transmission for the individual terminal exceeds a second prescribed time interval, the optical transmitter for the individual terminal is disabled.

Abstract: A method for checking a ring optical network line for data transmission between a plurality of network subscribers in a motor vehicle, wherein one network subscribers carries out a master function, wherein, apart from the optical network line, there is a further communication line which has a star structure. The network subscribers having the master function is arranged in the centre of the star structure and is connected directly via the communication line to every other network subscribers. The optical network line is checked by the network subscriber having the master function outputting a start signal to the individual network subscribers. The individual network subscribers acknowledge the start signal for the network subscribers the master function via the communication line. After the start signal, the network subscriber having the master function outputs an initialization signal via the optical network line.

Abstract: Vulnerability of an optical network to channel impairments or the like, is addressed by utilizing real-time monitoring and control of prescribed optical channel impairments. The impairments are compensated for by employing an optimization process in the optical network such that the optical signals from the source or sources of the impairments are controllably adjusted at any particular node in the network. The optical signals are attenuated more or less at the source node of the associated optical channel in order to optimize performance of the corresponding optical channel in the network. A variable optical attenuator (VOA) is used at the &lgr; laser source of optical channel having the impairment to obtain the attenuation. The optical signal impairment is measured at a receiving node and the source node of the associated optical channel is determined.

Abstract: Each piece of WDM light transmitted via the first and second line is demultiplexed for each wavelength by the first and second optical demultiplexer, and is selected by n optical selectors. Each selected optical signal is split by n optical splitters and is input to one set of optical switches. Each one of optical signals from the set of optical switches is selected by n optical selectors. Furthermore, each selected optical signal is regenerated by n wavelength converters. Each regenerated optical signal is split by n optical splitters, and is multiplexed by the first and second optical multiplexers.