Abstract: A network element including an active/standby pair of line units, an active/standby pair of switch fabric units, at least one service unit, and a management and control unit. Each line unit maintains data communications using a first communications protocol. Each switch fabric unit maintains data communications using a second communications protocol. Each service unit includes a first backplane interface supporting the first communications protocol, and a second backplane interface supporting the second communications protocol. The management and control unit provides a control infrastructure for selectively communicating data units between the active/standby pair of line units, the active/standby pair of switch fabric units, and the service unit, responsive to provisioning information or information contained within the respective data unit.

Abstract: A method is provided for providing protection of a local area network (LAN) connection that includes providing first and second LAN cards in a multi-service platform. The first and second LAN cards each include at least one port. The first and second LAN cards are coupled to a network edge device through their respective ports to communicate LAN traffic. The method also includes designating the first LAN card as an active card and the second LAN card as an inactive card. The method further includes detecting a network failure associated with the first LAN card. The method further includes protecting LAN traffic communicated between the second LAN card and the LAN by designating the second LAN card as an active card and the first LAN card as an inactive card.

Abstract: An Ethernet passive optical network (EPON) ring for providing protection against fiber failures. The optical network unit (ONU) is coupled to the ring fiber by a three-port passive optical splitting module that has three two-way optical passages. By the three two-way optical passages, the OUN receives/transmits data from/to the two ends of the optical line termination (OLT) to provide protection while the fiber failure. Moreover, it provides better authorization of users and simpler collision detection by the two-way transmission of the three-port passive optical splitting module to prevent hackers from invading and to reduce collisions.

Abstract: A modular cross connect system for optical telecommunication networks has the optical unit divided in at least two main bodies with one section for connection comprising the collimators and a main commutation section with MEMS devices. The first section is a fixed part while the second section is a readily removable section. The two sections face each other through a window and, in the first section, optics are provided for steering all or part of the optical signals from and to the main MEMS unit to a MEMS standby or protection plane to allow replacement of the main MEMS unit without interrupting service.

Abstract: Optical bypass node upgrade configurations are disclosed: (1) a configuration where optical taps are pre-positioned in wavelength division multiplex (WDM) line systems terminating at optical-electrical-optical (OEO) core switching nodes to allow for future upgrade of the nodes to degree-two or higher optical bypass; (2) a configuration where the taps are pre-positioned in a degree-two optical bypass node to allow for future upgrade to a degree-N optical bypass node; and (3) a configuration and procedure for upgrading OEO core switching nodes to optical bypass when the taps have not been pre-positioned in the WDM line systems. These configurations do not introduce bit errors for non-upgraded optical paths.

Abstract: A method and system provide capacity-efficient restoration within an optical fiber communication system. The system includes a plurality of nodes each interconnected by optical fibers. Each optical fiber connection between nodes includes at least three channel groups with different priority levels for restoration switching in response to a connection failure. The system maintains and restores full-capacity communication services by switching at least a portion of the channel groups from a first optical fiber connection to a second optical fiber connection system based on the priority levels assigned to the channel groups. Service reliability is effectively maintained without incurring additional costs for dedicated spare optical fiber equipment by improving idle capacity utilization.

Abstract: This invention concerns the field of telecommunication networks using optical fibres. The invention relates to a method of determining a connection path between two points in an optical network comprising several paths to connect said two points, each path comprising optical fibre spans and power amplifiers, said method comprising different steps depending on the degree of knowledge of network optical data. This data consists of the optical losses LI in optical fibre spans, the maximum allowable input power IP into said spans and the maximum output power PA from the amplifiers.

Abstract: The embodiments of the invention provide a method of routing convergence in a control plane of an intelligent optical network, which includes: a function unit perceiving a service link state transmitting an alarm notification message indicating a failure in a service link to a routing protocol unit when the service link is in failure; the routing protocol unit confirming a service link failure in the control plane according to the alarm notification message. The embodiments of the invention also provide an apparatus of routing convergence in a control plane of an intelligent optical network. According to the embodiments of the invention, the establishment of a new service or re-routing may be implemented within several seconds or even hundreds of milliseconds after the service link failure in the control plane occurs.

Abstract: In an optical transmitting or receiving apparatus, a plurality of replaceable electro-optic converters or a plurality of replaceable opto-electric converters are provided in correspondence with optical transmission lines.

Abstract: A method to facilitate recovery of a node in a communications network is disclosed. The method comprises receiving one or more messages from at least another node in the communications network and restoring connectivity of a recovering node based at least in part on the received messages.

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: A self-healing WDM (Wavelength Division Multiplexing)-PON (Passive Optical Network) system is disclosed and includes a CO (Central Office), a RN (Remote Node) and a plurality of subscriber units. The system includes a trunk working fiber and a trunk protection fiber for connecting the CO with the RN, a distribution working fiber, and a distribution protection fiber for connecting the RN with the subscriber units. The CO is connected to the trunk working fiber and the trunk protection fiber, and contains an optical switching unit switched when an error or communication failure occurs, an upstream working optical receiver and an upstream protection optical receiver for receiving upstream data, and a downstream working light source and a downstream protection light source for transmitting downstream data.

Abstract: An optical transmitter for generating a modulated optical signal for transmission over a fiber optic link to a remote receiver including a laser; a modulator for externally modulating the optical output signal with a RF signal to produce an optical signal including a modulated information-containing component; and a phase modulator coupled either to the output of the modulator or directly to the output of the laser for canceling the noise signals generated in the laser.

Abstract: A network component (3d) for an optical network (1) is described, including a coupling device (2; 4, 5) for optical coupling of the network component (3d) to the optical network (1), the coupling device (2; 4, 5) having a receiving module (4) and a transmitting module (5); a first data processing device (8, 9) which is unidirectionally connected to the receiving module (4); a second data processing device (10, 11) which is unidirectionally connected to the transmitting module (5); the first data processing device (8, 9) being unidirectionally connected to the second data processing device (10, 11) for transmitting data to the second data processing device; a detection device (4) for detecting the network status; and a two-way switch (23) for switching of the input of the first data processing device (8, 9) between the receiving module (4) and the output (19) of the second data processing device (10, 11) as a function of the network status detected.

Abstract: An optical, multi-channel, Differential Phase Shift Keying (DPSK) receiver demodulates multiple Wavelength Division Multiplexed (WDM) channels using a single interferometer. This distributes expense of the interferometer over all channels of an optical signal, allowing for deployment of cost-effective, scalable, wideband, WDM DPSK systems. For example, for an 80 channel WDM link, the receiver uses a single interferometer instead of eighty interferometers and associated stabilization hardware, dramatically reducing size, weight, power, and cost. The receiver is architecturally compatible with existing interferometer technologies so previous development and qualification efforts can be leveraged. This allows for expedited technology insertion into existing optical communications networks, including terrestrial and space-based optical networks.

Abstract: A redundant optical signal transmission and reception system enables information exchange via an optical communications network without data loss in the event of optical transmitter or receiver failure. In one embodiment, the redundant optical signal system includes a primary transmission link comprising a plurality of optical transmitters and a multiplexor for modulating and combining electrical signals into a primary multiplexed optical signal. In the event of failure of an optical transmitter, a backup transmission link is activated to compensate for the malfunctioning transmitter. The backup transmission link utilizes a backup optical transmitter to modulate the electric signal formerly received by the malfunctioning optical transmitter. The backup transmission link combines the backup optical signal with the primary multiplexed optical signal to form a complete optical signal for transmission over the optical network.

Abstract: The invention describes a two-stage optical amplifier adapted for inserting OADM in the mid-stage, and an integrated assembly designed for implementing the amplifier in a way suitable for forming unidirectional and bi-directional configurations useful in optical networks. One of them is a so-called east-west configuration for a bi-directional transmission, where each direction of the optical transmission is served by the two-stage optical amplifier the 1st stage of which belongs to one integrated assembly, and the 2nd stage—to another assembly.

Abstract: A method and system for providing tandem protection in a communication system. Path protection is provided using at least two redundant communication paths and selecting the communication path having a higher signal quality. Interface protection is provided through a protection transceiver. The interface protection may be delayed while the path protection attempts to restore communication.

Abstract: A link based network protection path calculation mechanism wherein a protection route is calculated that is guaranteed not to traverse the link it is intended to protect. The mechanism takes advantage of the fact that the same color cannot pass twice through the same optical fiber. The protection path is determined by eliminating all colors from the logical topology of the network except for the color corresponding to the link to be protected before executing the search algorithm. This serves to guarantee that the protection path calculated will not traverse the same physical fiber as the link to be protected. Virtual colors can be assigned to the links running through fiber bundles such that they do not pass through the same fiber/bundle twice.

Abstract: A method for triggering an optical protection event in an optical layer of a network comprising the following steps: i) monitoring the optical performance of an optical signal transmitted within the optical layer of the network; ii) provisioning optical protection in the event the monitored optical performance falls below a first threshold level; and iii) triggering an optical protection event, in the event the monitored optical performance falls further to below a second threshold level. The monitoring step is performed within the optical layer of the network by using a proxy to determine an optical performance characteristic which corresponds to the transmission quality of electronic signals extracted from said optical layer signal.

Abstract: There is provided a wavelength division multiplex transmission system with satisfactory transmission characteristics and extensive functions for avoidance of defects. Transmission signals to be transmitted by an optical transmission device are distributed among a plurality of wavelength components, converted into WDM signals, and sent to a WDM transmission network, and WDM signals from the WDM transmission network are restored to the transmission signals by an optical receiving device. This system includes a wavelength component-specific route setting device which sets routes for transmission on the WDM transmission network for each wavelength component.

Abstract: An optical communication network, an optical information transmission method and network node devices for use in an optical communication network, in which optical signals are exchanged via a first data link between a first network node device and a second network node device with interposition of a number of further interconnected network node devices, in which, after a disturbance on the first data link, a third network node device sends a signaling signal to a fourth network node device connected to the third network node device for setting up a second data link which acts at least partially as a standby for the first data link, which signaling signal contains a parameter (NRR, n) determined by the third network node device on the basis of which it is determined whether the fourth network node device is responsible for setting up the second data link or not.

Abstract: An all optical network for optical signal traffic has at least a first ring with at least one transmitter and one receiver. The first ring includes a plurality of network nodes. At least a first add/drop broadband coupler is coupled to the first ring. The broadband coupler includes an add port and a drop port to add and drop wavelengths to and or from the first ring, a pass-through direction and an add/drop direction. The first add/drop broadband coupler is configured to minimize a pass-through loss in the first ring and is positioned on the first ring.

Abstract: An apparatus having n-number of working cross-connects for cross-connecting an n-bit input signals arriving from a plurality of input paths on a per-bit basis; n-number of first logic circuits for calculating the exclusive-ORs of each said n-bit and applying outputs to a standby cross-connect for providing outputs; n-number of second logic circuits for calculating the exclusive-ORs of said output signals from each of said working cross-connects and from the single standby cross-connect; and third logic circuits for selecting output signals of said working cross-connects and outputs of the second logic circuits. The apparatus detects the occurrence of an abnormality in working cross-connects by monitoring the outputs of the second logic circuits, identifies the faulty cross-connect by successively turning off one of the n-inputs to the first and second logic circuits, and select outputs from the second logic circuits instead of from the faulty cross-connect by using the third logic circuits.

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: A communication device for interconnection of first and second networks, of which at least the first network is a bidirectional ring network, includes first and second interconnect modules, each such module adapted to receive outgoing data traffic on the first network at a data rate not substantially greater than a predetermined maximum rate for one of the ring directions, and to convey the outgoing data traffic to the second network. When a fault occurs in one of the first and second modules, the other module is reconfigured to receive substantially all of the outgoing data traffic and to convey the outgoing data traffic to the second network regardless of whether the outgoing data traffic is transmitted on the first network in the clockwise or in the counterclockwise direction.

Abstract: An apparatus and method for fault detection and isolation in an optical network is disclosed in which each node determines an appropriate response to a line fault or an equipment fault, obviating the need for a central computer to coordinate the actions of each node in response to a fault. Each network node includes a local controller and restoration elements for detecting and responding to faults. Each local controller correllates a first set of optical characteristics measured by optical detectors with the local node with a second set of optical characteristics for the channels reported to the local node from an upstream optical element, such as a neighboring upstream node, to determine if a line switch or equipment switch is required. In a preferred embodiment, each node is communicatively coupled to its neighboring node via an optical supervisory channel, with the neighboring nodes communicating status messages and data on channel characteristics via the optical supervisory channel.

Abstract: A data storage system includes controller nodes and a storage component. The controller nodes couple the storage component to a host. The storage component includes a controller and sleds with disk drives. The host and the storage component form an arbitrated loop. When the arbitrated loop is down, the controller removes the storage component from the arbitrated loop so the controller, the sleds, and the disk drives form an internal loop. When the internal loop is also down, the controller tests each of the sleds individually and marks those that are not responding properly. If a sled is responding properly the controller tests each of the drives in that sled individually and marks those that are not responding properly. The controller adds back into the internal loop the sleds and the drives that are not marked as bad, and then the storage component back into the arbitrated loop.

Abstract: A sub-network of a communication network includes four nodes, with each node having two input ports and two output ports. The first node and the fourth node each link both of their input ports and one of their output ports to other nodes of the sub-network, with each of their remaining output ports operable to send signals outside of the sub-network. The second and third nodes link both of their output ports and one of their input ports to other nodes of the sub-network while each of their remaining input ports is operable to receive signals from outside of the sub-network.

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: An optical one-to-one protection switching apparatus exchanges signals between a transmit node and a receive node. If a fault is detected in the first transmission line (down-stream), a controller in the node controls a drive circuit so as to shut off a gate. Then, the controller in the transmit node upon receiving a switching request from the receive node, controls the drive circuit so as to shut off the gate. Thereby, the optical switch is switched. The transmitter of the client terminal is thus connected to the second transmission line (down-stream). Upon receiving the switching request from the transmit node, the optical switch in the receive node is switched. Thereby the receiver in the client terminal is connected to the second transmission line (down-stream).

Abstract: Methods, apparatus and systems for regenerating, monitoring and bridging optical signals through an optical cross-connect switch to provide increased reliability. A self testing method, apparatus and system for an optical cross-connect switch. An optical-to-electrical-to-optical converter (O/E/O) is provided in an optical cross-connect switch to provide optical-electrical-optical conversion. I/O port cards having an optical-to-electrical-to-optical converter are referred to as smart port cards while I/O port cards without an optical-to-electrical-to-optical converter are referred to as passive port cards. Test port/monitor cards are also provided for testing optical cross-connect switches. Methods, apparatus and systems for performing bridging, test access, and supporting redundant optical switch fabrics are also disclosed.

Abstract: A collapsed ring fiber optic system includes a service path and a protection path provides at a shallow water portion of the fiber optic system, to deal with any fiber cuts that may occur at the shallow water portion without loss of main trunk bandwidth. The service and protection paths meet at a branch point, which is preferably located at a deep water portion of the fiber optic system. A passive combiner or a 1×2 switch is provided at the branch unit, 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. At another shallow water portion of the fiber optic system, nearby where a destination is located, the signal provided on the optical path over the deep water portion is split into a service path and a protection path, to provide redundancy to deal with any fiber cuts that may occur.

Abstract: An optical communication system comprising plural optical communication paths, a passive optical coupler, and at least one optical node. The passive optical coupler has a plurality of inputs coupled through the passive optical coupler to an output of the passive optical coupler, and each input is coupled in a corresponding one of the optical communication paths. Each optical node comprises plural optical line terminals, each of which is interposed in a corresponding at least one of the optical communication paths. Each optical line terminal is operable to either (a) substantially prevent an optical signal propagating in that corresponding at least one optical communication path from reaching a corresponding input of the passive optical coupler through the at least one optical communication path, or (b) permit the optical signal to propagate in that corresponding at least one optical communication path towards the corresponding input of the passive optical coupler.

Abstract: A branching unit, for use in optical communication systems, has three branches A, B and C each including a connection for a power feed and several inputs/outputs for optical fibers. Optical switches are provided for selectively coupling inputs/outputs of different branches to enable a routeing of optical signals through the unit. The routeing is effected in dependence upon the way in which each of the three branch connections are provided with an electrical power feed.

Abstract: The invention relates to an optical telecommunications network comprising several nodes (N1 to N4) connected to one another by optical transmission paths that form several working rings (R1 to R4), each of which passes via each node. Information is transmitted in the network at several different wavelengths. To ensure that the network can be implemented as cost-effectively as possible, it comprises a group of nodes (N1 to N4) including N nodes, a group of working rings (R1 to R4) including N rings, and a group of wavelengths (?1 to ?4) including N wavelengths in such a way that each node in the group of nodes is configured to transmit signals at one wavelength in the group of wavelengths to all rings in the group of rings except to the ring from which it receives signals, and to receive signals at all wavelengths in the group of wavelengths except for its own transmitting wavelength from both directions in only one of the rings in the group of rings.

Abstract: Fault tolerance is provided in a cross-connect system having only duplicated switch fabrics, instead of the triplicated switch fabrics of the prior art. In addition to the two information switch fabrics, the cross-connect system has a relatively small code switch fabric which switches check-code signals generated at each input interface for each input signal sent to an information switch fabric. Fault-detection and error-recovery components in each output interface (1) generate local check-code signals for each outgoing signals received from an information switch fabric and (2) compare those local check-code signals to the corresponding check-code signal received from the code switch fabric to detect a failure and to select a healthy signal as the output signal for that output interface. In one embodiment, input and output interfaces are clustered, and the corresponding input and output check-code signals are multiplexed, for even greater savings in overhead (e.g.

Abstract: A polarization scrambler unit includes a plurality of polarization scramblers, a switching unit for coupling one of the polarization scramblers to a transmission line fiber, a detection unit for detecting an output signal from the polarization scrambler coupled to the transmission line fiber, and a controlling unit for switching, via the switching unit, between the polarization scramblers and another polarization scrambler whenever a false output signal is detected by the detection unit. Thus, the polarization scrambler unit has a redundant structure.

Abstract: Techniques for providing normal operation and service restoration capability in the event of failure of terminal equipment or transmission media in a heterogeneous network, such as a hybrid network containing single- and multi-wavelength lightwave communications systems. An optical switching node (OSN) is placed at each node in the ring network to provide the required connections between various fibers and terminal equipment, but having switch states that allow signals on the protection fibers to bypass the terminal equipment at that node. Ring-switched signals propagate around the ring on protection fibers without encountering the terminal equipment at the intervening nodes. To the extent that the protection fiber links between any given pair of nodes are incapable of supporting all the relevant communication regimes, such links are modified to provide such support.

Abstract: The band management circuit of the present invention is utilized in a fiber-optic network that uses, for example, ATM-PDS, in order for an SLT to control the transmissions of a plurality of ONU, which are accommodated by this SLT. The band management circuit of the present invention stores one time in a table an identification number, which specifies a multi-point device for which transmission is authorized. An identification number stored in a table is generated by a table generating portion. The table generating portion sequentially generates the identification number of a number of transmission authorizations determined in accordance with a transmission band provided to respective multi-point devices. A write/read control portion sequentially writes to a table identification number data generated by the table generating portion.

Abstract: An OC3 to three DS3 SONET multiplexer is provided employing a field programmable gate array and other components in a single Type 400 mechanics card to achieve a form factor that is substantially reduced when compared to existing SONET multiplexers. The OC3 to three DS3 SONET multiplexer has integral optical redundancy and automated provisioning. Manual switches are provided to select continue/drop and line build out for each DS3. Switches are also provided for loopback options. The face plate for the multiplexer provides front access to all of the OC3 and DS3 connectors. The multiplexer is interchangeable with DS3 to DS1 multiplexer cards and WDM cards in a compact M13 SONET enclosure that is particularly useful at wireless cell sites.

Abstract: To provide a system in which a configuration is simple and a switching of an optical line can be performed at a high speed. A protection unit for performing optical line protection by using K1-K2 information inserted into a payload is provided for each physical interface. The protection unit includes a filter for separating a payload of user data and a payload including K1-K2 information according to a control signal in a received payload, a selector for switching user data to be transmitted or K1-K2 information to be transmitted after adding a control signal of a value corresponding thereto, and a control unit for controlling an output buffer to a switch block and creating K1-K2 information to be transmitted and communicating with a physical interface card of another system on the basis of K1-K2 information.

Abstract: A high speed optical routing apparatus and method, in which data traffic, such as an IP packet, an Ethernet frame, etc., is switched in an optical frame unit at a high speed. The apparatus is provided with a plurality of input and output ports, and with one add port for adding data received from a lower IP router, and one drop port for dropping processed data toward the lower IP router. A header wavelength dividing unit extracts the header wavelength signals from among input optical signals inputted through the input ports and the add port. The header wavelength signals contain header information on data wavelength signals contained in the input optical signals. An optical signal inputting section demultiplexes optical signals having the data signals according to the wavelength, and for dividing and inputting the wavelength-based demultiplexed data wavelength signals according to a frame.

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: Various embodiments of apparatus and various embodiments of methods to communicate between a first circuit board and a second circuit board using one or more open air communication channels are provided. A plurality of light transmitters and light receivers are attached to a first circuit board; and a corresponding plurality of light receivers and light transmitters are attached to a second circuit board. The light receivers on both circuit boards are disposed to receive data transmitted by the corresponding light transmitters on each circuit board. In one embodiment, where the light transmitters are laser diodes, different colors may be used to increase adjacent signal rejection. In another embodiment, the light transmitters may be laser, radio, microwave, digital, ultraviolet, or infrared light transmitters. The light transmitters may transmit data across open spaces between circuit boards, including through apertures in boards placed between the light transmitter and light receiver.

Abstract: An optical transmission system formed from a plurality of nodes interconnected in a ring configuration via at least two transmission media provides protection capacity for each optical channel. If a channel signal does not meet predetermined criteria, then a loss of signal indication is declared for the channel and one of a plurality of protection switching states is invoked to re-route service traffic carried by the impaired channel to its destination via corresponding protection capacity. The switching states include particular transmission states and at least “keep-alive” and “protection access” states.

Abstract: A dual-output Mach-Zehnder modulator (MZM2) and configurations of optical transmitters based on the MZM2 which obviate the optical splitter that is typically used to provide keep-alive functionality in redundantly-connected, protected optical networks, SONET add-drop multiplexers, and optical IP routers. The configurations provide equivalent keep-alive utility at a reduced system cost relative to the prior art. The configurations also support enhanced Operations, Administration, Maintenance, and Provisioning (OAM&P) functionality at little to no additional cost relative to the prior art. Instead of being a direct copy of the service signal, the keep-alive of this configuration is an inverted version of the service signal. This inverted version of the service signal is supported at a client by utilization of means for detecting and righting the inverted signal.

Abstract: A node for use in a WDM optical network, the node comprising a tributary receiver unit for receiving a data signal distributed via the WDM optical network and destined for said node, a path protection switching unit for switching receipt of said data signal at the tributary receiver unit from a working path to a protection path of the WDM optical network, and a control unit for the path protection unit, wherein the control unit comprises a multi rate clock data recovery (CDR) device arranged, in use, to detect a loss of lock (LOL) in the data signal received at the tributary receiver unit based on a comparison of an actual data rate received and a pre-programmed reference rate for said data signal.

Abstract: A redundant optical signal transmission and reception system is disclosed to enable information exchange via an optical communications network without data loss in the event of optical transmitter or receiver failure. In one embodiment, the redundant optical signal system includes a primary transmission link comprising a plurality of optical transmitters and a multiplexor for modulating and combining electrical signals into a primary multiplexed optical signal. In the event of failure of an optical transmitter, a backup transmission link is activated to compensate for the malfunctioning transmitter. The backup transmission link utilizes a backup optical transmitter to modulate the electric signal formerly received by the malfunctioning optical transmitter. The backup transmission link combines the backup optical signal with the primary multiplexed optical signal to form a complete optical signal for transmission over the optical network.

Abstract: A arrangement is described for transmitting, radiating and receiving high-frequency signals. The arrangement is comprised of a system connected to a transmitting and receiving device (3) which includes at least one high-frequency element (1) capable of guiding electromagnetic waves and a first signal cable (5) extending parallel thereto. To improve the service reliability of the arrangement, a second signal cable (6) which is also connected to the transmitting and receiving device (3), is arranged parallel to the high-frequency element (1) and maintains a significant spatial separation to the first signal cable (5).