EP4165800A1 - Emplacement de panne dans un réseau optique en anneau - Google Patents

Emplacement de panne dans un réseau optique en anneau

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Publication number
EP4165800A1
EP4165800A1 EP20733234.7A EP20733234A EP4165800A1 EP 4165800 A1 EP4165800 A1 EP 4165800A1 EP 20733234 A EP20733234 A EP 20733234A EP 4165800 A1 EP4165800 A1 EP 4165800A1
Authority
EP
European Patent Office
Prior art keywords
fault
parameter
node
event
fault event
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20733234.7A
Other languages
German (de)
English (en)
Inventor
Riccardo Ceccatelli
Giacomo AGOSTINI
Roberto Magri
Stefano Parodi
Luca Risso
Marina VALERI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of EP4165800A1 publication Critical patent/EP4165800A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0791—Fault location on the transmission path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0793—Network aspects, e.g. central monitoring of transmission parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07953—Monitoring or measuring OSNR, BER or Q
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07955—Monitoring or measuring power

Definitions

  • Examples of the present disclosure relate to methods and apparatus for locating a fault in an optical ring network.
  • Fronthaul networks are typically based on a single optical fiber infrastructure from a main node (Central Office) to remote nodes (radio antenna sites) using WDM technology for multiplexing multiple optical channels over the same optical fiber.
  • WDM Single Fiber Working
  • SFW Single Fiber Working
  • the optical channels are transported using different wavelengths for uplink and downlink transmission on the same optical fiber.
  • WDM pluggable modules are fitted in the radio access network, RAN, nodes (passive mode) or in transponders (active mode) and connected to passive optical filters.
  • Fronthaul network infrastructure typically reuses existing deployed fiber and can be based on point to point, P2P, topologies, point to multi-point, P2MP, topologies, such as star topologies with a remote feeder node, or a ring topology with a hub node communicating to all other nodes.
  • a ring network topology allows a main node to be connected to many remote nodes by means of a single optical fiber, offering traffic protection and limiting latency.
  • optical fiber is a valuable resource and network operators tend to minimize the number of fibers deployed in the fronthaul and backhaul network segments.
  • Each node may be allocated a different pair of wavelengths for downlink and uplink transmissions.
  • a fault in a ring network may result in some wavelengths becoming unavailable to their respective nodes. Protection schemes may switch the direction of some or all wavelengths to avoid the fault by using a part of the ring network that is still intact between the hub and node.
  • W02007/044939 describes a method of automatically determining a fault location by monitoring photodiodes at each node to detect a probe signal and to communicate this using an Optical Supervisory Channel (OSC). By analyzing which nodes can and cannot detect the probe signal, the location of the fault can be inferred.
  • OSC Optical Supervisory Channel
  • US2009/0074403 describes another method of automatically determining a fault location using the MAC layer to detect and control switching at each node. However, again this requires additional equipment and is protocol dependent.
  • a method of determining a fault location in an optical ring network having a number of nodes comprises monitoring a parameter of a traffic signal associated with each node of the optical ring network. In response to receiving an indication of a fault event, the method compares a value of the parameter of each node before and after the fault event to determine the fault location.
  • Parameters at different layers may be used, for example received power, round trip delay and traffic signal quality parameters such as bit error rate (BER).
  • BER bit error rate
  • the effect of the fault on each node can be determined and from this the location of the fault can be automatically determined without the need for additional equipment at the nodes.
  • This simple approach is applicable to passive as well as active or semi-active nodes and does not require any additional hardware but can be implemented using only new software.
  • a variety of different types of parameter may be monitored providing implementation flexibility depending on factors such as availability of monitoring of parameters.
  • apparatus for determining a fault location in an optical ring network having a number of nodes.
  • the apparatus comprises a processor and memory which contains instructions executable by said processor whereby the apparatus is operative to monitor a parameter of a traffic signal associated with each node of the optical ring network. In response to receiving an indication of a fault event, the apparatus is operable to compare a value of the parameter of each node before and after the fault event to determine the fault location.
  • a computer program comprising instructions which, when executed on a processor, causes the processor to carry out the methods described herein.
  • the computer program may be stored on a non transitory computer readable media.
  • an optical ring network having a number of nodes and apparatus as described herein.
  • Figure 1 is a schematic illustration of an optical ring network according to an example
  • Figure 2 is a schematic illustration of example parameter monitoring approaches according to an embodiment
  • Figure 3 is a flow chart of a method of locating a fault in an optical ring network according to an embodiment
  • Figures 4A, 4B and 4C illustrate example fault location scenarios in the optical ring network of Figure 1 ;
  • Figure 5 is a schematic illustration of an apparatus for locating a fault in an optical ring network according to an embodiment.
  • Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analogue) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • FIG. 1 shows an example of an optical ring network 100 according to an embodiment.
  • the network 100 comprises a hub or central office 105 coupled to a number of remote nodes
  • the optical fiber 103 may be a single working fiber (SFW) over which wave division multiplexing (WDM) technology is used to communicate between the nodes and hub.
  • SFW single working fiber
  • WDM wave division multiplexing
  • references to the optical fiber 103 may indicate a plurality of fibers.
  • Each node 110A, 110B, 110C may be allocated a different pair of wavelengths for downlink and uplink transmissions.
  • the optical fiber 103 can be divided into links L1 , L2, L3, L4 between two nodes 110A,
  • downstream traffic signals 170D may propagate in a first direction D1 around the ring network and upstream traffic 170U may propagate in a second direction D2.
  • upstream traffic 170U may propagate in a second direction D2.
  • dual or multiple optical fibers may be employed, and downstream and upstream traffic may travel in different directions to those indicated.
  • protection switching in which some of the traffic signals may propagate in different directions to ensure continued communication with nodes downstream of the fault. For example if a fault were to occur in link L3, downstream signals intended for node 110C would no longer be able to propagate in direction D1 and protection switching may instead be arranged to propagate these traffic signals in direction D2 where there is no fault between the hub and node 110C.
  • protection switching may couple an isolated node to another fiber.
  • the nodes 110A, 110B, 110C may be radio access network, RAN, nodes connected to passive optical add/drop filters (not shown) on the SFW to form a Centralized Radio Access Network (CRAN) network domain.
  • the nodes 110A, 110B, 110C are remote radio units.
  • the hub 105 may comprise a baseband processing unit.
  • the RAN nodes may provide Third Generation Partnership Project (3PPG) wireless services to mobile subscribers. However other types of deployment may also be catered for such as Fiber to the Home for direct optical fiber provision to home and/or business subscribers.
  • 3PPG Third Generation Partnership Project
  • the hub 105 comprises an optical transponder and multiplexing/demultiplexing unit 145 which converts between electronics signals in baseband circuitry 150 and optical signals in the fiber 103.
  • a pair of wavelengths are allocated for the downstream and upstream traffic for each node 110A, 110B, 110C and a splitter 140 splits the wavelengths into the two ends of the fiber so that they may propagate in either direction D1 , D2 around the ring network.
  • the traffic signals carried on the respective wavelengths propagate through one end of the optical fiber 103, for example as shown the end connected to L1.
  • an optical protection module (OPM) 130 may be arranged to switch the signals to and from the splitter through the other end of the fiber as well, that is the end connected to L4. As such, in the event of the protection scheme being used, a direction of propagation around the optical fiber 103 ring is reversed for at least one of the nodes 110A,
  • the last link L4 of the fiber is connected to secondary port 135-2 of the OPM which is not coupled to the splitter 140. However, upon protection switching, the secondary port 135-2 is coupled to the splitter to enable wavelengths to circulate the fiber in both directions D 1 , D2.
  • a loss of a pilot tone on a wavelength separate from the traffic wavelengths may be used.
  • the pilot tone (or pilot signal) is on a same wavelength as the traffic.
  • a pilot tone generator 125 is connected to an optical add/drop multiplexer 120X to inject the pilot tone onto the optical fiber 103.
  • Another optical add/drop multiplexer 120Y at the other end of the fiber 103 drops or isolates the pilot tone from the other signals on the fiber and directs this to a first port 135-1 of the OPM 130.
  • Loss of the pilot tone signal at the first port of the OPM may trigger the above described protection switching where the splitter 140 is coupled to both ends of the fiber 103.
  • loss of traffic carrying wavelengths may be used to trigger protection switching, or a signal indicating that a protection switching event has occurred may be used. The occurrence of a protection switching event is indicative of detection of a prior fault event by some mechanism.
  • the hub 105 also comprises an apparatus 155 for determining a fault location in the optical ring network.
  • the apparatus 155 may be located in a different location.
  • the apparatus 155 monitors one or more parameters of a traffic signal 170D, 170U associated with each node 110A, 110B, 110C.
  • the parameter or parameters monitored may include received power of a wavelength carrying the traffic signal, a round trip delay of the traffic signal, and/or a quality parameter of the traffic signal, for example bit error rate (BER) or code violations (CV). Any or a combination of these parameters may be monitored depending on what is available within the network 100. Further additional or different parameters may be used which relate to traffic signals to respective nodes.
  • BER bit error rate
  • CV code violations
  • the apparatus compares a value of the parameter or parameters of each node before and after the fault event in order to determine the fault location as described in more detail below.
  • Figure 2 illustrates two methods of determining a value of a parameter before and after a fault event. Depending on the circumstances, one method may be more suitable for some types of monitored parameters than the other method.
  • a timeline t is shown together with a fault event time 215 and a protection switching time 220. Protection switching of an optical ring network and settling of transient conditions will normally reliably follow fault event detection 215 within an expected time period, for example after a few seconds to 2 minutes. This is indicated by time period 232 which follows detection of the fault event and includes protection the switching event 220 and the settling time.
  • Values of the parameter 205 may be determined during predetermined or sequential time intervals 210 and recorded for later analysis.
  • a predetermined time interval may be for example 15 minutes long.
  • the determined value of the parameter 205 for each time interval 210 may be an average, median, a maximum or minimum or any suitable analysis of measurements of the parameter occurring during the time interval 210.
  • a measurement of the parameter 205 may be taken fifteen times during each time interval and the average taken as the value of the parameter to be used for later analysis.
  • Valid and invalid time intervals and hence values of the parameter may be determined based for example on the variation of the measurements. If the measurements vary too much, for example over a threshold, then the time interval may be declared invalid. In Figure 2, invalid time intervals are indicated using horizontal lines and valid time intervals are indicated by diagonal lines. Transients associated with a fault event may cause parameter measurements to vary widely resulting an invalid time interval.
  • the comparison of the value of the parameter before and after the fault event 215 may be based on the respective value of the parameter stored for a valid time interval 225 before the fault event and a valid time interval 240 after the fault event.
  • This approach to comparing values of the parameter before and after the fault event may be suitable for received power and/or return trip delay parameters. This may be because the length of optical fiber over which the traffic signals travel between the hub 105 and one or more nodes 110B, 110C changes when the direction D1 , D2 of the traffic signals changes. For example, traffic signals to node 110C travel via links L1 , L2, L3 during normal operation but following protection switching travel via only link L4 which may be much shorter than the combination of links L1 , L2, L3. Therefore, the attenuation of the wavelengths and the time to propagate to node 110C changes following a fault event. This change is shown by the change in the value of the parameter(s).
  • Values of the parameter may additionally or alternatively be determined during a sliding window 230 spanning the fault event 215.
  • one or more measurements of a parameter before the fault event 215 but within the sliding window 230 may be taken, and one or more measurements of the parameter may be taken after fault event 215 but still within the sliding window 230.
  • the measurement(s) of the parameter taken after the fault event 215 may be within a post fault time period 235 following the settling time 232 but still within the sliding window 230.
  • the post fault time period 235 may be at least 2 minutes of a 10 minute sliding window 230, although both of these time periods are configurable.
  • measurements after the fault event may alternatively or additionally be taken within the settling time 232.
  • the comparison of a value of the parameter before or after the fault event may be based on a maximum or minimum measurement, for example a maximum measurement before the fault event and a minimum measurement after the fault event, or vice versa; although other options are available such as an average of the measurements before and after the fault event and within the sliding window.
  • This approach to comparing values of a parameter before and after a fault event may be suitable for traffic quality parameters such as BER or CV as once the transients associated with protection switching subside the BER or other traffic quality parameter values may revert to similar levels and so significant differences in the value of such a parameter may not be seen in sequential time intervals 225 and 240 for example.
  • measurements of received power may be taken during the sequential time periods 210 as described above and additionally during the sliding window.
  • Measurements taken during the post fault time period 235 may then be used to determine the value of the parameter after the fault event and compared with the value of the parameter before the fault event determined from measurements during a valid sequential time period 225 before the fault event. This allows for a faster comparison of values of the parameter before and after the fault event and therefore a faster determination of the location of the fault.
  • the embodiment may fall back to using measurements in the next valid sequential time period 240 as described above.
  • An analysis of the difference or change in the value of one or more parameters before and after the time of a fault event can be used to infer or determine the location of the fault.
  • the value of the parameter(s) changes due to the use of the protection mechanism, i.e. protection switching to route the traffic signals on a different route or direction around the ring.
  • the protection mechanism i.e. protection switching to route the traffic signals on a different route or direction around the ring.
  • the protection mechanism affects the one or more parameters of the traffic, e.g. received power, round trip delay and/or signal quality parameter received at the nodes or hub.
  • This effect of the protection mechanism which is operating, following the fault, is used to determine the location of the fault.
  • References to comparing a value of a parameter before and after a fault event may alternatively be considered as comparing a value of a parameter before and after a protection mechanism is operated.
  • the fault location 480B may be a break in the fiber between node 110C and the hub 105.
  • the distances the traffic signals travel between each node 110A, 110B, 110C and the hub are unaffected and therefore parameters such as received power and return trip delay will also be unaffected.
  • a 480A fault is located in a link L2 between two nodes 110a and 110B.
  • the traffic signals 175U and 175D to the nodes 110B and 110C downstream of the fault location 480A propagate in a different direction.
  • traffic signals 170U and 170D to and from the node 110A upstream of the fault propagate in the same direction.
  • the analysis may indicate a fault location 480C1 in L2 between nodes 110a and 110B or fault 480C2 located between node 110C and the hub 105. This may occur when the difference in values of a parameter at node 110B downstream of the first potential fault location 480C1 is above the predetermined threshold but where the difference in the value of the parameter at the or each node 110C further downstream of the first potential fault location 480C1 is or are below the predetermined threshold.
  • Figure 3 illustrates a flowchart of a method of determining a fault location in an optical ring network according to an embodiment.
  • the method 300 may be implemented by any suitable apparatus and optical ring network, for example apparatus 155 and optical ring network 100 of Figure 1.
  • the apparatus 155 may be a dedicated hardware module forming part of the hub 105, software running on a generic processing platform, or the apparatus may be implemented at a remote location for example in a cloud computing environment where parameter values and fault indication signals are forwarded from the hub to the remote location.
  • the method 300 monitors a parameter of a traffic signal associated with each node of the optical ring network.
  • One or more parameters may be monitored, including for example received power, round trip delay and/or a signal quality parameter such as BER or CV.
  • the parameter(s) may be monitored using either or both of the approaches described with respect to Figure 2.
  • a value for the or each parameter 205 is determined for each sequential time interval 210. This may be an average of measurements taken over the time interval for example. These values are stored for subsequent analysis but comparing a value in a (valid) time interval before the fault event and a time interval after the fault event.
  • measurements of the or each parameter are taken over a sliding window 230 which moves with time. When a fault event is indicated, a measurement within the sliding window taken before and after the fault event are used in the subsequent fault location determination analysis.
  • measurements from one of the sequential time intervals 225 before the fault event may be compared with measurements from a time period 235 within the sliding window but after the fault event.
  • the method determines an indication of a fault event and if so, moves onto 315. If no fault event is indicated, the method moves back to 305 to continue monitoring the parameter(s).
  • the indication of a fault event may be a loss of a pilot tone added to the optical ring network. Other mechanisms for indicating a fault event may alternatively and/or additionally be used, for example a loss of a traffic signal or a protection switching event which implies a fault has been detected. Activation of protection switching may indicate that a fault event has occurred a few milliseconds prior.
  • the indication of a fault event may be a signal from an OPM to the apparatus 155.
  • the method compares a value of the or each parameter of each node before and after the fault event.
  • this may be implemented by calculating a change or difference between the respective values before and after the fault event so that this can be compared with a threshold.
  • the difference in values for each parameter is calculated for each node in the optical ring network.
  • the method then compares the differences in parameter values of each node with a predetermined threshold.
  • the method determines whether the different in the values of the or each parameter do not exceed the threshold in any of the nodes.
  • the fault location 480B is determined to be between the last node 110C in the downstream direction (D1) and the hub 105, as shown in Figure 4B. If this is not the case, the method moves to 330.
  • the downstream direction is a first direction D1 corresponding to the direction of propagation of downstream traffic signals 170D as illustrated in Figure 1. This contrasts in the embodiment with an upstream or second direction D2 corresponding to the direction of propagation of upstream traffic signals 170U in normal operation, but which may carry some downstream traffic signals (175D) in the second direction D2 following protection switching; depending on the location of the fault.
  • the method determines whether a series of nodes have a difference in values of the or each parameter above the threshold. In other words, the method determines whether all nodes 110C in the downstream direction after a first node 110B in the downstream direction have a parameter difference above the threshold. In this case, at 335, the fault location 480a is determined to be before the first node 110B in the downstream direction with a parameter difference above the threshold as shown in Figure 4A.
  • the method determines the fault location 480C1 , 480C2 to be either before the first node 110B in the downstream direction with a parameter difference above the threshold or after the last node in the downstream direction as shown in Figure 4C.
  • the likelihood of a single fault location being determined may be improved by using differences in values for two or more parameters. This may minimize the number of times the method arrives at 340. Furthermore, using two parameters increases robustness, for example, if measurement of one parameter fails, or accuracy.
  • the predetermined threshold used to compare the difference in values of the parameter before and after the fault event may be determined experimentally and/or calibrated depending on the parameter used as noted below and/or certain aspects of the optical ring network such as its size
  • a combined change score may be derived from changes the values of a plurality of parameters, with the change score used to determine the fault location. This may provide more accurate localization and reduce the likelihood of ambiguity between two possible fault locations; the situation of Figure 4C.
  • Table 1 illustrates calculating a change score for a number of nodes SG A - SG in an optical ring network. Columns for respective scores for change of difference in values before and after a fault event for received power DR, return trip delay ARTD, and bit error rate ABER are shown. These scores may be added to provide a change score, with an example provided for node SG A .
  • the change scores for each parameter may be determined based on the level of difference between the values of the parameter before and after a fault event, for example whether they fall within certain ranges, e.g. above and/or below one or more thresholds. Table 2 below illustrates how the change score may be determined for each parameter.
  • a Service Group refers to the wavelengths added/dropped to a node and used for uplink and downlink communications between the node and the hub. In an SFW system this may be two wavelengths, one for the uplink and one for the downlink.
  • the change in value of each parameter may be determined by averaging the change in values from each wavelength in the node’s SG, or by selecting the largest change in value in the SG and comparing this with the threshold.
  • Alternative calculations of the values used to calculate the change scores could be used, for example medium and aggregate.
  • the change score for each parameter may be determined according to whether the difference in values of the parameter before and after the fault event exceed one or more change score thresholds. For example a change score of 0 is allocated to the received power parameter if the change in values is below a first received power change parameter threshold PwThrl , change score is 1 if it is between PwThrl and a second higher received power change parameter threshold PwThr2 and change score is 2 where this is above the second threshold PwThr2.
  • the change scores for other parameters can be allocated depending on respective thresholds. These may be determined experimentally and/or based on expert experience with other optical ring networks.
  • Example change score threshold may be:
  • These thresholds may calibrated case by case, for example according to the accuracy of the measurements available.
  • the Round Trip Delay (RTD) parameter is the time taken by a special packet sent in the frame at Hub to reach a node and return to the Hub.
  • RTD Round Trip Delay
  • the use of a second parameter like RTD may resolve the fault location determination.
  • RTD measurements may be implemented with high accuracy, that is in terms of tens of nanoseconds. Considering that 5 ns corresponds to 1 meter of optical fiber, we can say that differences of 100 meters in the optical paths can be well measured and, based on this assumption, the following threshold may be used in an example implementation:
  • RTDThn 500 ns (corresponding to a path length variation of ⁇ 100 m)
  • RTDThr 2 2500 ns (corresponding to a path length variation of ⁇ 500 m)
  • these thresholds may be refined according to the RDT measurement accuracy available and to the actual lengths of the links L1 - L4 in the optical ring network which are known by design.
  • the traffic signal quality is usually measured in terms of Bit Error Rate, deduced from FEC (when available) or from CV (Code Violations counter for 8B/10B frames) or in terms of a Hi BER (in case of 64B/66B frames).
  • An example change score threshold for BER is:
  • ABERThr 6 (i.e. 6 decades of differences in BER)
  • the threshold should be calibrated on this parameter. For example, a score of 2 if a loss of signal alarm has been detected or 0 if not.
  • the change scores for each parameter may be added together to generate a combined change score for each node.
  • the combined changes scores of each node may then be compared against a predetermined score threshold S TH r corresponding to the predetermined threshold described with respect to Figure 3.
  • S TH r a predetermined score threshold
  • the comparison of the combined change scores for each node with this score threshold may then be used to determine the fault location as described with respect to Figure 3.
  • nodes 110B and 110C both have change scores which exceed the threshold and therefore correspond to a fault location before node 110B.
  • none of the nodes have change scores which exceed the threshold and therefore correspond to a fault location after node 110C.
  • FIG. 5 illustrates an apparatus according to an embodiment.
  • the apparatus 500 may be the apparatus 155 for locating a fault in an optical communication link of Figure 1 or any other suitably configured apparatus. This may be implemented in dedicated hardware in the hub 105 or in software operating on a generic processing environment within the hub. In a further alternative, the apparatus may be configured in a cloud environment communicable with the hub.
  • the apparatus 500 may be configured to perform the method 400 of Figure 4 or other methods for determining the location of a fault by comparing values of one or more parameters of a traffic signal of each node before and after a fault event.
  • the apparatus 500 comprises processing circuitry 510 (e.g. a processor) and a memory 530 in communication with the processing circuitry 510.
  • the memory 530 contains instructions 535 which when executed by the processor 510 cause the processor to carry out methods of the embodiments.
  • the memory 530 may also be used to store values and/or measurements of the parameters. At example method is illustrated which may be performed by the apparatus 500 to determine a location of a fault in an optical ring network.
  • the method monitors one or more parameters of a traffic signal associated with each node in optical ring network. Examples parameters include one or more of the following: received power, round trip delay, signal quality parameters such as BER.
  • the method determines whether there has been an indication of a fault event. This may be indicated by loss of a pilot tone or wavelength used for traffic signals, and/or a protection switching event. If there is no such indication, the method continues to monitor the parameters, otherwise the method moves onto step 560.
  • the method determines the location of the fault by comparing a value of the or each parameter before and after the fault event. This may be achieved by determining a difference between the values before and after the fault event and comparing these to respective thresholds.
  • change scores may be determined for a plurality of parameters and combined to calculate a combined change score which may be used to determine the fault location. The differences and/or change scores may be used to determine which parameters have been affected by the fault event and subsequent protection switching.
  • the location of the fault can be determined by analyzing which nodes have been sufficiently affected by the fault as indicated by their parameter values before and after the fault event changing by a threshold amount. If no nodes have been significantly affected this indicates that only the last link in the optical ring network has been affected and therefore the fault may be determined to be in this link. If a series of nodes along the ring between the hub and intermediate node have been sufficiently affected, this indicates that the fault is in the link immediately upstream of the intermediate node most distant from the hub. Where only some or none of the nodes between the intermediate node and the hub have been affected, then the fault may be immediately upstream of the intermediate node but may also be in the last link.
  • Embodiments may provide a number of other advantages including not requiring any additional hardware and being suitable for passive as well as active and semi-active nodes.
  • the solution may be implemented in software and therefore easily installed on existing optical ring network equipment, may be installed in one location only such as the hub, and does not require complex monitoring and/or signaling at remote nodes. By being able to use different types of parameter, the solution is adaptable to whatever monitoring may be available at respective networks and where available can utilize two or more parameters to add robustness. Whilst the embodiments have been described with respect to a SFW Fronthaul system, they are not restricted to such an application and may, for example, equally be applied to dual fiber working optical ring networks.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
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  • Optical Communication System (AREA)

Abstract

Des modes de réalisation de la présente invention concernent des procédés et un appareil permettant de déterminer l'emplacement d'une panne dans un réseau optique en anneau. L'invention concerne un procédé permettant de déterminer l'emplacement d'une panne dans un réseau optique en anneau (100) comportant un certain nombre de nœuds (110A, 110B, 110C). Le procédé consiste à surveiller un paramètre (205) d'un signal de trafic (170D, 170U) associé à chaque nœud du réseau optique en anneau (305) et, en réponse à la réception d'une indication d'un événement de panne (215, 220, 310), comparer une valeur du paramètre de chaque nœud avant et après l'événement de panne pour déterminer l'emplacement de la panne (315, 325, 335, 340).
EP20733234.7A 2020-06-10 2020-06-10 Emplacement de panne dans un réseau optique en anneau Withdrawn EP4165800A1 (fr)

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CN115361312B (zh) * 2022-10-21 2023-01-24 之江实验室 一种基于链路流量的环网节点间链路状态监测方法和装置
CN116545529B (zh) * 2023-07-06 2023-09-12 国网浙江省电力有限公司湖州供电公司 基于光缆运维路径的故障数据处理方法
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JP2004248316A (ja) * 2004-04-05 2004-09-02 Nippon Telegr & Teleph Corp <Ntt> 故障箇所同定方法
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