Abstract: Various high loss loop back (HLLB) repeater architectures are disclosed that enable selectively monitoring (e.g., measuring, analyzing, etc) of Rayleigh signals from both inbound and outbound directions of an optical communication system. In one such embodiment, first and second optical test signal frequencies (or ranges) are used, in conjunction with selective filtering, for monitoring the outbound and inbound paths, respectively. The repeater architectures allow optical time domain reflectometry (OTDR) monitoring techniques to be employed, for example, in particularly long repeater spans, such as those in excess of 90 km in length.

Abstract: A data processing device is connectable to a communication network and operable to receive data associated with an attenuation characteristic of a transmission line of a cable in a cable communication subsystem, the subsystem comprising a transmitter and/or receiver coupled to the cable. The data processing device is responsive to the received data to initiate a security procedure.

Abstract: A 3 fiber line switched ring (3FLSR) provides protection for (optical) transmission networking wherein N nodes are connected via 3 lines (or optical fibers) in a ring topology. Two of the three fibers form a main transmission line and may transmit in one direction in the ring whereas the third might transmit in the opposite direction. This architecture of the 3FLSR provides a dual protection scheme, including a bi-directional line switching coupled with a unidirectional line switching. Traffic is categorized based on the level of protection available for the particular traffic type. The first two transmitting fibers form a bi-directional ring, carrying primary and secondary traffic which can survive 2 and 1 failures on the ring respectively. The third fiber may form a unidirectional ring, carrying additional traffic that can be pre-empted in case of multiple failures in the bi-directional ring. The 3FLSR enables reconfiguration of existing 2/4 fiber rings and conforms to applicable standards.

Abstract: A method and apparatus for controlling the power level of an optical signal includes detecting the loss of a supervisory signal counter-propagating in an optical fiber.

Abstract: Systems and methods for monitoring a data transmission link, especially an optical, bidirectional data transmission link, in which a digital transmit signal is transmitted on a first transmission path from a local end of the data transmission link toward a remote end of the data transmission link. A portion of the power of the transmit signal sent at the local end is transmitted, delayed by a non-zero delay time on a second transmission path as a control signal toward the remote end of the data transmission link. Both signals are received at the remote end and are tested for the presence of events of a predetermined type. A conclusion can be reached on the quality of the transmission link as a function of a time correlation and frequency of the appearance of events in the received transmit signal and in the received control signal.

Abstract: An apparatus and a method for accurately detecting Loss of Optical Power (LOS) by noise power cancellation effect and optical power is measured at two output ports of an athermal periodic filter, wherein one output port in the optical frequency domain, is aligned with the signal channels of an input WDM signal (on-grid port), whereas the second output port is aligned complementary to the first output port (off-grid port). In a preferred embodiment, the apparatus computes the ratio of the measured optical powers at the two output ports of the periodic filter, and comparing them to a threshold value that is determined from the overall common-mode rejection ratio (CMRR) of the detection apparatus. In an alternative embodiment, the apparatus additionally compares the optical power measured at the on-grid port to a threshold power that is determined from system design parameters.

Abstract: An optical element module, an optical node, an optical distribution system, and a management method are disclosed. The optical element module includes: at least one passive optical element, at least one fiber adapter, a power interface, and a state detecting unit, where the passive optical element is configured to distribute and/or process an optical signal that can proceed even without power supply; the fiber adapter is configured to connect a fiber connector and provide a fiber port to couple a fiber; the power interface is connected to a power cable or a power bus and configured to feed power from the power cable or power bus to the state detecting unit; and the state detecting unit, if powered, is configured to respond to a connection state change of the fiber in the fiber adapter and output a state indication that indicates the state of the fiber port.

Abstract: A bidirectional optical module according to the present invention comprises light emitting elements 110, 130 that emit light to enter an optical fiber 71, a light receiving element 190 that receives light having exited the optical fiber 71 and a light branching element 160 that guides the light having exited the optical fiber 71 onto the light receiving element 190. It further includes a stray light shielding member 185 disposed between the light branching element 160 and the light receiving element 190 and having formed therein an opening 186, through which the light to enter the light receiving element 190 passes. The stray light shielding member 185 blocks stray light 100b while light 100a having exited the fiber 71 passes through the opening 186. Therefore, any increase in the extent of error in the detection of the returning light level or the position of a reflecting point is prevented.

Abstract: A method and system of measuring the spectroscopic impedance of a sensor and its immediate surroundings. The sensor is disposed on an engineered structure and is coated with a protective coating. The method includes providing a first optical signal having a first modulation frequency and amplitude. The method also includes transmitting the first optical signal and a second optical signal from a first location to a sensor location. The method also includes modulating the second optical signal with a second modulation frequency and amplitude, the second modulation frequency and amplitude converted from the first optical signal. The method also includes comparing the first modulation frequency to the second modulation frequency to determine one of a phase difference and a time lag and calculating the electrochemical impedance spectroscopy of the sensor and its immediate surroundings as a function of frequency.

Abstract: An apparatus for measuring the characteristics of an optical fiber is provided. An optical pulse generator generates, from a coherent light, first and second optical pulses having a time interval which is equal to or shorter tan a life time of an acoustic wave in the optical fiber. A detector couples the coherent light with a Brillouin backscattered light which includes first and second Brillouin backscattered lights belonging to the first and second optical pulses respectively, thereby generating an optical signal. The detector further converts the optical signal into an electrical signal. A signal processor takes the sum of the electrical signal and a delay electrical signal which is delayed from the electrical signal by a delay time corresponding to the time interval, thereby generating an interference signal, and finds the characteristics of the optical fiber based on the interference signal.

Abstract: The subassembly includes a laser for emitting signals towards fibers to be monitored, a passive alignment carrier, a photodetector for monitoring reflected laser signals from the fibers and for monitoring laser output power, and an optical fiber. The laser is disposed within the passive alignment carrier. The optical fiber is embedded in the passive alignment carrier, and has an angled fiber facet. The laser emits signals toward and through the angled fiber facet, whereby a portion of the laser signal illuminates the photodetector, and another portion illuminates the fibers that are being monitored and reflects back to the photodetector such that faults on the fibers can be detected.

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 to incurring additional costs for dedicated spare optical fiber equipment by improving idle capacity utilization.

Abstract: An arrangement in a fiber optic network device for analyzing a set of optical signals traversing the fiber optic network device is provided. The arrangement includes a set of ports for receiving and outputting the set of optical signals. The arrangement also includes a set of photodiodes, which is configured at least for receiving and forwarding the set of optical signals. The arrangement further includes a splitter, which is configured at least for receiving the set of optical signals from a first photodiode, splitting the set of optical signals into at least a first part and a second part, and forwarding the first part to a second photodiode and the second part to a third photodiode. The set of optical signals is configured to traverse the fiber optic network device irrespective whether power is provided to circuitry of the fiber optic network device.

Abstract: The present invention provides a system and method for monitoring and providing settings to nodes in a telecommunications fiber network. The method and system reviews alarm and threshold settings of nodes and in the network. If the alarm and threshold settings a node are not within set standards, the standard alarm and threshold settings may be provided to the nodes. The method and system of the invention also calculates span loss between nodes in a telecommunications fiber network and the amplification levels of nodes in the network.

Abstract: A system and method using differential loop gain for fault analysis in line monitoring equipment. Differential loop gain data is calculated from loop gain data, and fault analysis is conducted using differential loop gain data, e.g. by comparing the differential loop gain data to predefined fault signatures.

Abstract: Methods, systems, and computer-readable media provide for notifying and determining a location of a fiber cut. According to embodiments, a method for determining a location of a fiber cut in a passive optical network (PON) including a plurality of optical network terminations (ONTs) is provided. According to the method, a plurality of base signatures are generated prior to the fiber cut. Each of the base signatures correspond to a known configuration of the plurality of ONTs. In response to the fiber cut, a current signature corresponding to a current configuration of the plurality of ONTs is generated. Whether the current signature matches one of the base signatures is determined. In response to finding a matching base signature, the location of the fiber cut is determined based on the known configuration of the plurality of ONTs corresponding to the matching base signature.

Abstract: A component for an optical communication network comprises a source (6) for an optical communication signal, an output port (11) for outputting the optical communication signal on an optical transmitting fiber (1), a light sensor (14; 15) and an optical circulator (9) for transmitting the optical communication signal from the source (6) to the output port (11) and for transmitting light reflected or received from outside at the output port (11) to the light sensor (14; 15). The light sensor (14, 15) has an evaluation circuit (13) connected to it for detecting a time delay between a time marker of a light signal from the source and the corresponding time marker of the light arriving at the light sensor (14; 15).

Abstract: Optical Time-Domain Reflectometer (OTDR) troubleshooting of a passive optical network (PON) can be enhanced by deploying cascaded splitters, at least some of which have multiple inputs. That is, at least some of the splitters in the PON have not only a first input coupleable to the optical line terminator (OLT) or output of another splitter but also a second input directly coupleable to an Optical Time-Domain Reflectometer (OTDR). Optical time-delay reflectometry can be performed upon a selected portion or segment of the PON by selecting a splitter and transmitting an optical test signal from the OTDR directly to the input of the selected splitter and analyzing the reflected signal.

Abstract: The present invention makes improvements in a mobile communication system that performs a communication via a communication network provided in a mobile body to execute a data transfer. The present system comprises a plurality of nodes, a path control device which receives data from the nodes respectively, selects a path for the data transfer on the communication network, and outputs the data, first optical fibers which connect each of the nodes and the path control device and transfer the data, and second optical fibers provided in parallel with the first optical fibers. In the present system, the path control device communicates with the node via the second optical fiber when a failure occurs in the first optical fiber.

Abstract: Embodiments are directed to fiber optic cable diagnostics using digital modulation. A contact of a RFID (radio frequency identification) device located in a cable is connected with a contact of an optical transceiver. Data through the cable is using digital modulation and monitored to determine if the fiber optic cable and the optical transceiver are properly functioning.

Abstract: One apparatus embodiment includes a first light source, a second light source, and a receiver having a photodetector. The first light source emits a first signal at a nonvisible wavelength for data transmission. The second light source emits a second signal at a visible wavelength for fault detection when combined with the first signal for transmission over a fiber optic path. The receiver converts the first signal from the nonvisible wavelength to an electrical signal.

Abstract: In a passive optical network system, a parent station includes a reception circuit that receives an optical signal from each of child stations using a threshold used to identify if the optical signal is 0 or 1; a bandwidth setting unit that determines a time at which each child station sends an optical signal; a storage unit that stores thresholds and intensities of optical signals received from the child stations; and a control unit that sets a threshold, stored corresponding to a sending time, in,the reception circuit to control a reception of an optical signal. The control unit has a function that compares an intensity of a signal received from each child station at an optical signal reception time with information stored in the storage unit to detect and determine a fault in the child station or in the optical fiber connected to the child station.

Abstract: An optical communication device for detecting a defect in a standby optical fiber. An active optical output unit converts an electrical signal to an optical signal, and a standby optical output unit is provided as a substitute for the active optical output unit. An optical router is connected to the active optical output unit by an active optical fiber, and is also connected to the standby optical output unit by a standby optical fiber. The optical router outputs the optical signal received from the active optical output unit to the subsequent stage, and also outputs part of the optical signal to the standby optical output unit. A defect detector detects a defect in the standby optical fiber on the basis of the light level of the optical signal output from the optical router to the standby optical output unit through the standby optical fiber.

Abstract: Provided is a method for confirming optical fibers connection in a connection part in an optical connector, including: allowing light to pass through a first optical fiber and allowing cladding mode light to disappear; and detecting a difference in light intensity in the connection part between before and after the light from the first optical fiber enters a second optical fiber disposed in the optical connector.

Abstract: A photonic integrated circuit having a plurality of circuit components, is disclosed, which may include an MMI for splitting signal power passing therethrough among first and second optical pathways coupled to first and second outputs, respectively, of the MMI, thereby directing first and second percentages of the signal power along the first and the second optical pathways, respectively; and a photodetector integrated into the photonic integrated circuit and coupled to said first optical pathway for measuring a signal power level on said first optical pathway.

Abstract: An apparatus for performing an optical line analysis of continuous data signals. The apparatus comprise a phase position processor for computing a phase early/late indicator; a phase control code processor for computing a difference phase indicator; a frequency extractor for computing a low frequency jitter indicator; and a statistical calculator for computing a plurality of statistical measures regarding frequency and amplitude components of a jitter of an input continuous data signal, wherein the statistical measures are computed based on one of the phase early/late information indicator, the difference phase indicator, or the low frequency jitter indicator.

Abstract: An optical signal division transmission system in which an input optical signal is divided into N parts (termed as “N-part optical signals”) and transmitted at a transmission rate of 1/N, wherein an additional optical wave path is provided separately from an optical wave paths for transmitting said N-part optical signals, and even if a malfunction occurs in any one of said optical wave paths for transmitting said N-part optical signals, transmission of said N-part optical signals is continued, using said additional optical wave path.

Abstract: The present invention relates to a method for protecting an optical telecommunication network against possible failures and signal degrades, the network comprising at least two nodes; working resources and protecting resources connecting the nodes; a first protection mechanism operating at a first protection layer; and a second protection mechanism operating at a second protection layer, characterized by a) the step, carried out by a node detecting a failure that could be managed by said first mechanism, of sending downstream an in-band Forward Protection Indication signalling in order to instruct the second protection mechanism not to operate, or b) the step, carried out by a node detecting a Bit Error Rate between a certain range, of sending downstream an in-band Link Degradation Indication signalling in order to instruct the second protection mechanism to operate.

Abstract: An optical path switching device includes compact and unpackaged components; the components are mounted onto a single platform; and the components are coupled by luminous flux. Connection between optical fibers is negated. In particular the optical path switching device includes an optical input, an optical output, an optical branching device and an optical signal detection device. At least two of the optical input, the optical output, the optical branching device and the optical signal detective device are mounted onto a single platform.

Abstract: The present invention provides an automatic power restoring method capable of reliably detecting continuity by the dissolution of a line fault, to restore the optical power, even in a structure including an optical amplification medium on an optical transmission path and an optical communication system using the method. To this end, in an optical communication system to which the automatic power restoring method of the invention is applied, a pilot signal having a low transmission rate, a wavelength of which is set based on loss wavelength characteristics obtained by combining loss wavelength characteristics of an optical fiber used for the optical transmission path and loss wavelength characteristics of the optical amplification medium on the optical transmission path, is transmitted and received between an optical transmitting station and an optical receiving station when a line fault occurs, and a detection of continuity is thus performed.

Abstract: A dual structure for a multiplexing section extended to an OSU is obtained without adding a dynamic function, such as an optical switch, to a W-MULDEM. The W-MULDEM of an optical wavelength division multiplexing access system divides, among ports corresponding to the individual ONUs, downstream optical signals having wavelengths ?d1 to ?dn, which are received along a current-use optical fiber, or downstream optical signals having wavelengths ?d1+?? to ?dn+??, which are received along a redundant optical fiber. The W-MULDEM also multiplexes, for the port that corresponds to the current-use optical fiber or the redundant optical fiber, upstream optical signals having wavelengths ?u1 to ?un or wavelengths ?u1+?? to ?un+??, which are received along optical fibers corresponding to the ONUs. A wavelength difference between the downstream optical signal and the upstream optical signal that are consonant with each ONU is defined as an integer times the FSR of an AWG.

Abstract: Systems and methods for verifying performance at an intermediate point in an optical link are provided by virtue of one embodiment of the present invention. One application is locating a fault along a long optical link while minimizing the need for trained personnel to inspect and monitor the link at numerous widely separated locations. At an intermediate point in the link, a portion of the optical signal present is tapped off and demodulated. By use of error correction decoding techniques on the demodulated data, the performance of the link up until that intermediate point may be verified.

Abstract: A fiber optic protection apparatus includes a first optical switch, a first fault detection device, and first switch control device. The first optical switch is placed at the reception node of an optical link and has a primary input port connected to a primary optical transmission path. A secondary input port is connected to one secondary optical transmission path. The first fault detection device is in communication with the primary optical transmission path to identify a fault within the primary optical transmission path and to generate a fault signal indicating type or location of the fault. The fault signal is transferred to the first switch control device that is in communication with the optical switch. This causes the optical switch to connect one of the secondary optical transmission paths to the reception node when the fault signal indicates that the primary optical transmission path has a fault.

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: An optical-fiber-network (OFN) radio-frequency identification (RFID) system for deploying and/or maintaining and/or provisioning service and/or locating faults in an OFN. The system includes a plurality of OFN components, and at least one RFID tag that includes RFID tag data that has at least one property of the OFN component associated with the RFID tag. The RFID tag data is written to and read from the RFID tags using one or more mobile RFID readers either prior to, during or after deploying the OFN components. An OFN-component-data database unit is used to store and process the RFID tag data and is automatically updated by the one or more mobile RFID readers. This allows for different maps of the OFN to be made, such as an inventory map and a maintenance map, and for the maps to be automatically updated. The OFN-RFID system allows for mobile automated operations and management of OFN components by service personnel, and provides for faster and more accurate OFN system deployment and maintenance.

Abstract: A Gigabit Ethernet passive optical network (GE-PON) having a double link structure is disclosed. The GE-PON includes an optical line terminal (OLT), a plurality of optical couplers, and a plurality of optical network units (ONUs). The OLT sets up an active link and a standby link in response to a registration request message received over an optical cable. Each of the ONUs is doubly connected with the OLT via the optical cable and is adapted to transmit the registration request message to the OLT, form the active link with the OLT via the optical cable if it receives an active registration message transmitted from the OLT in response to the registration request message, and form the standby link with the OLT via the optical cable if it receives a standby message from the OLT. The optical couplers are disposed between the OLT and each of the ONUs to doubly interconnect them via different optical cables.

Abstract: A system and method for embedding or multiplexing an in-service optical time domain reflectometry (ISOTDR) or in-service insertion loss (ISIL) session. A preferred embodiment embeds the sessions using the same wavelength as the data traffic for point-to-point or point-to-multipoint optical fiber networks without interrupting or affecting the primary data transmission process.

Abstract: An optical test termination device (100) for use in optical network comprising a passive optical element (102) and a first optical coupler (104) and a second optical coupler (106) for coupling the optical test termination device (100) to an optical fiber (108, 110, 202). The passive optical element (102) comprises an input for receiving a test signal from the network and an output for outputting a response signal towards the network, wherein in response to the test signal the passive optical element (102) is operable to output the response signal, wherein said response signal differs from said test signal.

Abstract: Technology is proposed for estimating one or more characteristics of a main signal transmitted via a communication link, wherein the main signal is composed from a number of component signals possibly comprising respective data signals and transmitted via a number of respective communication channels. The technology comprises providing an analyzing circuit independent from the communication link, transmitting a probe data signal in the analyzing circuit, monitoring a bit error rate (BER) parameter associated with the probe data signal and introducing into the analyzing circuit at least a portion of energy of the main signal as an interference signal. The technology allows judging about characteristics of the main signal based on changes in the monitored BER parameter of the probe data signal.

Abstract: An optical transmission system includes an optical signal transmitter to output optical signal, a monitoring light transmitter to generate monitoring light, an optical multiplexer to output a multiplexed signal light by multiplexing the optical signal and monitoring light, an optical relay transmission path to amplify the multiplexed signal light by using a Raman amplification effect, an optical demultiplexer to demultiplex the multiplexed signal light, a monitoring light receiver to receive the monitoring light output from the optical demultiplexer, and a pumping light source stopping device to continuously monitor a transmission state of the monitoring light and, when the transmission of the monitoring light is interrupted, to stop emission of the pumping light from the pumping light source to be used for distributed Raman amplification.

Abstract: An Ethernet PHY hardware device supports Ethernet MAC SDH/SONET Automatic Protection Switching (APS) functionality for managing protection from failures and recovery from failures on an Ethernet network. An Ethernet PHY sublayer stored on the Ethernet PHY hardware device is configured to monitor working and protect channels and generate an interrupt upon detection of a hard failure or a soft failure. Upon detection of port failures or link failures, the Ethernet PHY sublayer generates the interrupt to invoke an Ethernet MAC Client APS Controller configured to generate and terminate APS requests on working and protect channels to manage protection of working and protect channels from failures and recovery from failures on the Ethernet network. The Ethernet PHY hardware device is configurable for use with a plurality of different network topologies to manage protection from hard or soft failures and recovery from hard or soft failures on the Ethernet network using the Ethernet PHY sublayer.

Abstract: The optical communication system of the present invention is constructed with a data plane and a control plane, and includes a first monitor for monitoring a path alarm on the data plane, a second monitor for monitoring a path alarm on the control plane, and an alarm comparator for comparing alarm statuses of the optical paths that the first monitor and the second monitor preserve, wherein an optical communication apparatus, of which the first monitor and the second monitor both are in a status of having detected the alarm, operate so as to start an operation of avoiding a fault. Such a configuration makes it possible to make a detour only around an appropriate section including a fault location without performing an erroneous operation when a fault has occurred in an optical path, in which a plurality of detour sections, in an all-optical communication system.

Abstract: A system and method for performing an in-service optical time domain reflectometry (OTDR) and/or insertion loss (IL) measurement(s) using the same wavelength as the data traffic for point-to-point or point-to-multipoint optical fiber networks. The OTDR or IL sessions are multiplexed in accordance with the network protocol in use to avoid any distortion of data transmissions.

Abstract: An optical transmission-path fault-detection system for detecting a fault in an optical-transmission path connecting an optical communications apparatus and an optical amplifier corresponding to the communications apparatus is disclosed.

Abstract: Intrusion detection for a multimode fiber optic cable uses a light signal launched into the fiber through the low ratio leg of a tap coupler to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes at the remote end is monitored for transient changes in the mode field power distribution which are characteristic of fiber intrusion to activate an alarm. The active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.

Abstract: Intrusion detection of one section only of a multimode fiber uses a light signal launched into the fiber at a location spaced from the source through a single mode fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the fiber. A small portion of the higher order signal modes at the a second location also spaced from the destination is sampled by a tap coupler and monitored for transient changes in the mode field power distribution which are characteristic of intrusion to activate an alarm. A fiber being used for data transmission can be monitored for intrusion by introducing a monitor wavelength different from that of the data signal. Central to this invention is the use of a bulk optic (commonly referred to as a pass/reflect) wavelength division multiplexer, one which maintains the modal distribution within the fiber.

Abstract: A network is maintained functional in the presence of a wide range of faults, including physical fiber cuts, transmission impairments creating signal quality degradation, and failure of equipment modules, for example, transceivers, using a common control and backup channel, either alone or in combination with fiber loopback protection or wavelength loopback protection, or fiber loopback protection or wavelength loopback protection alone. Systems constructed according to the invention require only a single transceiver per wavelength at each node that accesses that wavelength. The invention is equally applicable to type 1 nodes, which drop and add a single, predetermined wavelength, and to type 2 nodes which have the capability to drop and add any subset of the wavelengths employed in the network.

Abstract: A transmission apparatus that receives an optical signal by selecting any one of a plurality of provided optical signal transmission paths through protection control is configured to include a plurality of optical signal outputting sections that output the optical signals transmitted through said optical signal transmission paths respectively as optical signals having wavelengths that are different from each other, a wavelength selective optical switch capable of selectively outputting light of a wavelength corresponding to any one of the optical signals coming from the optical signal outputting sections on the basis of the frequency of a controlling frequency signal, and an optical switch controlling section that supplies said controlling frequency signal to the wavelength selective optical switch so as to output the optical signal coming from the optical signal transmission path side that is selected by said protection control among the optical signals coming from the optical signal outputting sections.

Abstract: An embodiment of the invention provides a method and apparatus for restoring a connection in a network. The connection is typically a sub network connection (SNC). In an embodiment, a failed line in a link connecting a first node and a second node is detected, where the failed line is associated with a sub network connection (SNC). The sub network connection (SNC) is then mapped to an alternate line in the link. The first node will change cross connections in a switch fabric in the first node, while the second node will change cross connections in a switch fabric in the second node, so that both nodes can transmit data on the selected alternate line, in order to restore the SNC.

Abstract: The control of the transmission of useful optical signals on different line paths of an optical transmission device is accomplished via at least one of the following features: using signal sources and signal sinks, the useful optical signals are coupled into the line paths, or are coupled out of them; at least one portion of the optical line paths is configured as normal line paths having coupling nodes via which a switchover to an alternative line path can be undertaken if a normal line path is disturbed; in addition to the useful optical signals, test signals, whose evaluation is used for the switchover between the line paths, are transmitted bidirectionally section-by-section; at least two types of test signals can be transmitted, of which a first type is used as an indicator for an intact line path and a second type as an indicator for a disturbed line path; and any switchover to an alternative line path is only undertaken if, before the detection of the disturbance, a test signal of the first type has be