Optical transmission system and fault location identification method

Abstract

An optical transmission system (1) includes nodes (31, 32, 35, and 51 to 55) that are connected to each other by an optical transmission path (2), monitoring units (7a, 7b, 7c, and 71 to 75) that sample, in time sequence, signal information in at least one signal sampling point between a transmission / reception end of each node and equipment within the node, and an OpS (8) that performs control thereof. The OpS (8) extracts a component (50a) estimated to include a failure site by causing the monitoring units (7a, 7b, and 7c) to observe signal information of reception ends of components, and identifies the failure site by causing the monitoring units (72 to 75) to observe temporal change of the signal information at the signal sampling point to detect the abnormality at the component (50a).

Description

[Technical Field]

[0001] The present invention relates to a technique for an optical transmission system and a fault location method. [Background technology]

[0002] In an optical transmission system, multiple nodes (devices) serving as communication devices are interconnected via optical transmission paths (optical fibers). Specifically, as shown in FIG. 1, the optical transmission system 10 has a hierarchical structure in which a lower layer L0 / L1 network, in which a large number of various devices are interconnected, and upper layers L2 / L1.5 and L3 networks, in which these networks are further interconnected (see FIG. 1). In an optical transmission system, optical physical characteristics and analog control characteristics interact in complex ways, making it difficult to identify the location and cause of a failure (abnormality) when it occurs. In recent years, optical transmission systems have become increasingly larger in capacity and wider in area, which increases the scale of the impact of a failure and makes it more difficult to identify the location of the failure. Therefore, in the maintenance and operation of optical transmission systems, there is a demand for early detection of failures and accurate identification of their location.

[0003] Therefore, methods have been developed for automatically detecting faults in optical transmission systems and identifying their locations. For example, Patent Document 1 discloses a method for narrowing down the range of suspected fault locations based on packet loss information in upper layers and the accommodation relationship of Optical-Channel Data Unit (ODU) paths. Patent Document 2 discloses a method for narrowing down the range of suspected fault locations on an optical path basis based on the optical signal characteristics of the receiving end of an optical path such as an Optical Multiplex Section (OMS) and the accommodation relationship of Optical Transport Unit (OTU) paths, and further identifying the suspected location in this optical path based on optical signal characteristic information. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-64160 [Patent Document 2] Japanese Patent Publication No. 2020-88628 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 can only narrow down the range of suspected locations to the OMS section (the area surrounded by the dotted line in Figure 1) where there is an add / drop of an optical channel of a specific wavelength and the accommodation relationship changes.The method described in Patent Document 2 identifies suspected locations in an optical path based on the optical signal characteristics only at the receiving end, so its accuracy is insufficient.

[0006] In view of the above problems, an object of the present invention is to identify a fault location in an optical transmission system with high accuracy. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following features. The optical transmission system according to the present invention has a plurality of nodes interconnected by optical transmission paths, and comprises a monitoring means provided in each of the nodes for collecting signal information in time series at a transmitting / receiving end of the node and at least one signal collection point between devices in the node, and a control means for controlling the monitoring means, wherein the control means is a component consisting of one or more nodes and optical transmission paths between the nodes. two The signal information at the receiving end of the optical path is observed by the monitoring means, and a deterioration in signal quality is detected at the receiving end. In two or more optical paths, the route of a common optical path The method executes a suspected fault component extraction process that extracts components within a range as components that are suspected to contain a fault location, and a fault location identification process that identifies the fault location in the extracted components by having the monitoring means observe temporal changes in signal information at the signal collection points of each node and detect abnormalities in the temporal changes in the signal information. [Effects of the Invention]

[0008] According to the present invention, it is possible to identify a fault location with high accuracy in an optical transmission system. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an example of a configuration of an optical transmission system. [Figure 2] FIG. 1 is a diagram illustrating a model of an optical transport network. [Figure 3] FIG. 1 is a diagram of a portion of an optical transmission system including a suspected faulty component. [Figure 4A] 10 is a graph showing an example of changes over time in signal quality at the receiving end of a suspected faulty component. [Figure 4B] 10 is a graph showing an example of changes over time in signal quality at the receiving end of a suspected faulty component. [Figure 5] 10A and 10B are diagrams illustrating changes over time in optical signal power at each signal collecting terminal in a suspected fault component. [Figure 6A] 10 is a graph showing an example of the change over time in normal signal power at a signal collection terminal of a suspected faulty component. [Figure 6B] 10 is a graph showing an example of the change over time in abnormal signal power at a signal collection terminal of a suspected faulty component. [Figure 6C] 10 is a graph showing an example of the change over time in abnormal signal power at a signal collection terminal of a suspected faulty component. [Figure 7A] 10 is a graph showing an example of the change over time in normal signal power at a signal collection terminal of a suspected faulty component. [Figure 7B] 10 is a graph showing an example of the change over time in abnormal signal power at a signal collection terminal of a suspected faulty component. [Figure 7C] 10 is a graph showing an example of the change over time in abnormal signal power at a signal collection terminal of a suspected faulty component. [Figure 8]10A and 10B are diagrams illustrating changes over time in optical signal power at each signal collecting terminal in a suspected fault component. [Figure 9] 10A and 10B are diagrams illustrating changes over time in optical signal power at each signal collecting terminal in a suspected fault component. [Figure 10] 10A and 10B are diagrams showing the state of temporal changes in optical signal power, waveform, and OSNR for each signal collection terminal in a suspected faulty component. [Figure 11A] 10 is a graph showing an example of an optical spectrum of a normal signal at a signal collection terminal of a suspected faulty component. [Figure 11B] 10 is a graph showing an example of an optical spectrum of an abnormal signal at a signal collecting terminal of a suspected faulty component. [Figure 12] 10A and 10B are diagrams showing the state of temporal changes in optical signal power, waveform, and OSNR for each signal collection terminal in a suspected faulty component. [Figure 13A] 10 is a graph showing an example of an optical spectrum of a normal signal at a signal collection terminal of a suspected faulty component. [Figure 13B] 10 is a graph showing an example of an optical spectrum of an abnormal signal at a signal collecting terminal of a suspected faulty component. [Figure 14A] 10A and 10B are diagrams showing the state of temporal changes in optical signal power, waveform, and OSNR for each signal collection terminal in a suspected faulty component. [Figure 14B] 10A and 10B are diagrams showing the state of temporal changes in optical signal power, waveform, and OSNR for each signal collection terminal in a suspected faulty component. [Figure 15] 10A and 10B are diagrams showing the state of temporal changes in optical signal power, waveform, and OSNR for each signal collection terminal in a suspected faulty component. [Figure 16] 10A and 10B are diagrams showing the state of temporal changes in optical signal power, waveform, and OSNR for each signal collection terminal in a suspected faulty component. [Figure 17] FIG. 1 is a diagram of a portion of an optical transmission system including a suspected faulty component. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0011] [Optical transmission system] The configuration of an optical transmission system will be described with reference to FIG. 1. FIG. 1 is a configuration diagram of an optical transmission system 10. The optical transmission system 10 is hierarchically organized in the order of L0 / L1 network, L2 / L1.5 network, L3 network, and service network (not shown) from the bottom up, and is composed of equipment groups arranged in each layer and optical transmission paths 2 connecting these to each other. Nodes (equipment) arranged in the lower layer L0 / L1 network include, for example, optical cross connects (OXC), repeaters (REP), and transponders (TRPD). In FIG. 1, the transponders are denoted by the symbol "3," and the OXC and REP are denoted by the symbol "5." The OXC incorporates an optical multiplexer / demultiplexer (MUX / DMUX), a wavelength selective switch (WSS), and an optical amplifier (AMP). Alternatively, the OXC may incorporate a Colorless, Directionless, Contentionless (CDC) device instead of a MUX / DMUX. The REP incorporates an optical amplifier. Optical channels (OCh) of each wavelength are formed between the transponder devices. A node in the L2 / L1.5 network is, for example, a Multi-Protocol Label Switching-Transport Profile (MPLS-TP) device 91, which is connected to a TRPD in the L0 / L1 network. A node 92 in the L3 network is, for example, a router. A node in the service network is, for example, a server. The present invention identifies faults in the L0 / L1 network, which is a lower layer of an optical transmission system, on a node-by-node basis or even on a device-by-device basis within the node. First, components consisting of one or more nodes that may contain a fault are extracted, and the fault location in the extracted component is identified.

[0012] The configuration of components will be described with reference to Figure 2. As shown in Figure 2, the L0 / L1 network is further hierarchically organized, from the bottom up, as follows: Optical Transmission Section (OTS), Optical Multiplex Section (OMS), Optical Physical Section (OPS), Optical Channel (OCh), Optical Transport Unit (OTU), and Optical-channel Data Unit (ODU). The OMS represents a logical communication path (path connection) for wavelength-multiplexed optical signals (corresponding to multiple OChs), and is terminated at OXC nodes and Add / Drop nodes each time a wavelength-multiplexed signal is multiplexed or demultiplexed. Therefore, by configuring the OMS in a component, it is possible to identify a fault location on a component-by-component basis with relatively high accuracy (see Patent Document 2).

[0013] An optical transmission system according to this embodiment will be described with reference to FIG. 3. FIG. 3 is a diagram illustrating the configuration of a portion of an optical transmission system in an L0 / L1 network. In FIG. 3, components (suspected fault components) estimated to contain fault locations and parts related to their extraction are illustrated in a simplified manner. Specifically, the optical transmission system 1 illustrated in FIG. 3 includes transponder devices 31, 32, and 35, optical multiplexers / demultiplexers 41, 42, and 45, and nodes 51, 52, 53, 54, and 55, which are interconnected by an optical transmission path 2. In addition, FIG. 3 represents the transmitting side (upstream) on the left and the receiving side (downstream) on the right. The optical transmission system 1 according to this embodiment further includes monitoring units (monitoring means) 7a, 7b, 7c, and 71 to 75 provided in the transponder devices 31, 32, and 35 and the nodes 51 to 55, which perform PM (Performance Monitoring) collection, and an OpS (Operation System, control means) 8 which controls the monitoring units 7a, 7b, 7c, and 71 to 75. 3, the optical transmission system 1 has logical optical paths (represented by thick arrows in the figure) of optical channels λ10, λ11, and λ20. The optical channels are represented by numbers λ01, λ02, λ03, ... in the order of wavelength.

[0014] Transponder devices 31, 32, and 35 incorporate the necessary transponders for each optical channel. In Fig. 3, transponder device 31 incorporates transponders 31a and 31b for λ10 and λ11, transponder device 32 incorporates transponders 32b and 32c for λ11 and λ20, and transponder device 35 incorporates transponders 35a and 35c for λ10 and λ20. When there is no need to distinguish between transponder devices 31, 32, and 35, they will be referred to as transponder device 3 as appropriate.

[0015] Nodes 51, 52, and 55, together with optical multiplexers / demultiplexers 41, 42, and 45, constitute an OXC. Node 53 is also part of the OXC, and the optical multiplexer / demultiplexer is omitted from FIG. 3. Nodes 51, 52, 53, and 55 each incorporate a WSS and an optical amplifier. Node 54 is a REP and incorporates an optical amplifier 64a. Nodes 51 to 55 also incorporate a power supply, a fan (cooling means), and the like. The optical amplifiers of nodes 51 to 55 use an automatic gain control (AGC) system. Nodes 51, 52, 53, 54, and 55 will be referred to as node 5 when no distinction is needed.

[0016] The monitoring units 7a, 7b, and 7c collect signal quality in time series from the receiving ends of the optical paths in the transponder devices 31, 32, and 35, and detect degradation of the signal quality.

[0017] The monitoring units 71, 72, 73, 74, and 75 (when not distinguished, will be referred to as the monitoring unit 7 as appropriate) collect optical signal power (transmission power, reception power) from the transmitting and receiving ends of the node 5 and between devices within the node 5 (the transmitting and receiving ends of each device) in time series at the nodes 51, 52, 53, 54, and 55, and store it for a certain period of time. Then, under control of the OpS 8, they determine whether there is an abnormality in the temporal change of the stored signal output, i.e., the signal output collected immediately before. The signal data storage period is set to be equal to or longer than the time required to determine whether the temporal change is normal or abnormal, and the shorter the storage period, the less data there is stored, which can reduce the load on the optical transmission system 10.

[0018] Furthermore, in order for the monitoring unit 7 to collect signal outputs, the node 5 is provided with photodetectors (Photodiodes: PDs, not shown) at the transmitting and receiving ends and between devices within the node 5 (when no distinction is made, these will be referred to as signal collection terminals (signal collection points) p as appropriate). In FIG. 3, the signal collection terminals p are represented by white circles "○". The number of signal collection terminals p in each node 5 is not particularly specified, but it is preferable to provide one at least at the receiving end, and more preferably at both the transmitting and receiving ends. Furthermore, depending on the components (devices) and their number of components of the node 5, it is preferable to provide signal collection terminals p between devices as well.

[0019] Node 54, which is an REP equipped with an optical amplifier 64a having a high priority for fault localization, has signal collection terminals p41 and p42 on both sides of the optical amplifier 64a, i.e., on the transmitting and receiving ends (see FIG. 5). Nodes 51 and 55, which also have a high priority for fault localization and a WSS and optical amplifier connected in series, have signal collection terminals p on the transmitting and receiving ends. Nodes 52 and 53 have signal collection terminals p on both sides of the set of WSS and optical amplifier connected in series. Node 52 also has signal collection terminals p on the two branched outputs of WSS 62b. In this way, in node 5, each of the high-priority WSSs and optical amplifiers has a signal collection terminal p on at least one of its transmitting and receiving ends. Node 51 is designated as signal collecting terminals p11 and p12, node 52 as signal collecting terminals p21, p22, p23, . . . , and node 53 as signal collecting terminals p31, p32, p33, . . . (see FIG. 5).

[0020] OpS8 is connected to monitoring units 7a, 7b, 7c, 71 to 75 via a data communication network and controls them. OpS8 extracts components (suspected fault components) that are likely to contain a fault location from the route of the optical path where monitoring units 7a, 7b, 7c have detected degradation in signal quality. OpS8 also has monitoring units 7 installed in nodes 5 included in the suspected fault components determine an abnormality from the accumulated signal output, and identifies the fault location in the suspected fault components.

[0021] [Fault location identification process] In the optical transmission system according to the present invention, the monitoring units 7a, 7b, 7c, 7 collect signal information in chronological order from the transponder devices 3 in which the monitoring units 7a, 7b, 7c, 7 are installed and the receiving ends of the nodes 5, and in parallel, the OpS 8 executes a suspected fault component extraction process to extract components (suspected fault components) that are estimated to contain fault locations, and further executes a fault location identification process to identify the fault location in the suspected fault components.

[0022] (How to identify the fault location) The fault location identification method according to the present invention executes a collection step in which monitoring units 7a, 7b, 7c, 7 collect signal information in chronological order from the transponder device 3 in which the monitoring units 7a, 7b, 7c, 7 are installed and the receiving end of the node 5, and in parallel with this collection step, executes a suspected fault component extraction step in which a component (suspected fault component) that is estimated to contain a fault location, and a fault location identification step in which a fault location in the suspected fault component is identified.

[0023] The monitoring units 7a, 7b, 7c, and 7 collect signal information from the transponder devices 3 in which the monitoring units 7a, 7b, 7c, and 7 are installed and the receiving end of the node 5, etc. The monitoring units 7a, 7b, and 7c collect signal quality from the receiving ends of the transponder devices 31, 32, and 35, and the monitoring unit 7 collects optical signal power from the signal collection terminal p of the node 5. The time granularity for storing the information collected by the monitoring units 7a, 7b, and 7c and the monitoring unit 7 and the OpS 8 via them is preferably shorter (higher) to improve the accuracy of identifying the fault location in the fault location identification process; specifically, an interval of one minute or less (t1≦1 min) is preferable, and several seconds to several tens of seconds (less than 60 seconds) is more preferable.

[0024] The OpS 8 causes the monitoring units 7a, 7b, and 7c to detect degradation of the collected signal quality at predetermined intervals t2 (t2≧t1). Specifically, when the monitoring units 7a, 7b, and 7c detect an abnormality or change in the time-series data of the Pre-FEC BER (Pre-Forward Error Correction Bit Error Rate) of the monitored transponder devices 31, 32, and 35, they identify the degradation mode based on a correlation analysis between the Pre-FEC BER time-series data and time-series data of analog information related to optical physical characteristics monitored by a digital signal processor (DSP) (see Patent Document 2). An abnormality in the Pre-FEC BER time-series data indicates degradation of the quality of the signal flowing through the logical optical path. Hereinafter, this analog information related to optical physical characteristics will be referred to as DSP-based OPM (Digital Signal Processing-based Optical Performance Monitoring).

[0025] 4A and 4B, this method enables early detection of signal quality degradation (shown by a solid line in the figures) before it reaches the FEC (Forward Error Correction) limit, which is the limit at which signal errors are introduced. Here, the monitoring unit 7c detects degradation in the signal quality of the wavelengths λ10 (FIG. 4A) and λ20 (FIG. 4B) from the transponder device 35. Therefore, it is highly likely that a fault exists in component 50a (encircled by a dotted line in FIG. 3) from WSS 62b of node 52 to downstream node 55, which constitutes the common optical path for λ10 and λ20 with transponder device 35 as the receiving end. Therefore, OpS 8 identifies this component 50a as a suspected fault component.

[0026] The time granularity of the suspected fault component extraction process is, for example, 15-minute intervals (t2=15 min), and shorter intervals are preferable for early detection of faults, but on the other hand, this puts a strain on the processing by OpS 8. Alternatively, the monitoring units 7a, 7b, and 7c may check the degradation of signal quality at a time granularity shorter than 15 minutes and notify OpS 8 of the detection of the degradation of signal quality, thereby starting the suspected fault component extraction process.

[0027] When the suspected-fault component 50a is extracted in the suspected-fault component extraction process, the OpS8 executes a fault location identification process to identify the fault location (fault portion) from the nodes 5 (52, 53, 54, 55) included in the suspected-fault component 50a and the optical transmission path 2. The OpS8 detects the abnormality at the time τ F (See Figures 4A and 4B) and the time variations in the optical signal power (received power, transmitted power) of the nearby wavelengths λ10 and λ20 before and after the abnormality are judged in order from the downstream signal collection terminal p52. If the signal is normal, the time variations in the optical signal power will be within the steady fluctuation range, as shown in Figure 6A. If the signal quality is degraded, the optical signal power will be within the normal fluctuation range from the abnormality detection time τ F 5, the received power is abnormal up to the transmitting end p41 of node 54 (represented by a black rectangle), and normal from the relay point p33 of node 53 upstream (represented by a white rectangle). On the other hand, the transmitted power is abnormal up to the receiving end p34 of node 53, and normal from the relay point p32 of node 53 upstream. Therefore, the area between signal collection terminals p33 and p34 (represented by a double-headed arrow in the figure) is identified as the fault location, and it is found that either or both of the WSS 63c and the optical amplifier 63d of node 53 are faulty.

[0028] While a failure in the optical amplifier is likely to affect power fluctuations across all wavelengths, a failure in the WSS may result in an abnormality that affects only one wavelength, and therefore abnormalities can be more clearly identified by observing the temporal changes in the optical signal power of each of the relevant wavelengths, λ10 and λ20, rather than the total optical signal power of all wavelengths.

[0029] As shown in FIGS. 7A and 7B, the change in optical signal power over time is F It is preferable to make the determination within a predetermined period before and after the failure of the suspected component 50a. By making the predetermined period short enough to allow determination, the processing load can be reduced. Specifically, it is preferable to make the determination based on temporal changes using multiple sets of data over the predetermined period. For example, if t1=10 seconds and the predetermined period is 15 minutes, the determination can be made based on temporal changes using 90 sets of data. Furthermore, since the monitoring unit 7 and OpS8 only need to store signal data up to the predetermined period, the data storage load can be reduced. Note that old signal data that has exceeded the storage period of the monitoring unit 7 and OpS8, and signal data collected from a signal collection terminal p outside the suspected component 50a, may be converted into statistical information and stored by the OpS8, for example.

[0030] In addition, the abnormality detection time τ F Outside (abnormality detection time τ F By judging an abnormality based on the fluctuation range in a predetermined period (before the abnormality detection time τ), it is possible to reduce erroneous judgments. In addition, it is possible to check transient changes when control is applied to the optical amplifier or WSS upstream of the signal collection terminal p. For example, there are cases where a decrease in optical signal power is not visible due to ALC control of the optical amplifier in response to the decrease in optical signal power. Examples of temporal changes in optical signal power due to ALC control are shown in Figures 6C and 7C. Furthermore, the fluctuation range used as the judgment standard is set based on the time τ F It is preferable to use the fluctuation range outside the predetermined period (before the predetermined period) for determining the temporal change before and after the predetermined period.

[0031] Figure 8 shows the change in optical signal power over time when another WSS 63b and / or optical amplifier 63a fails in the same node 53 as in Figure 5. As described above, depending on the configuration of node 5, the location of the failure can be identified with high accuracy by providing a signal collection terminal p not only at the transmitting and receiving ends but also at the relay points.

[0032] 9 shows the change in optical signal power over time when a fault occurs in the optical transmission line 2 connecting the nodes 53 and 54. In this way, by providing a signal collection terminal p at the transmitting and receiving ends of the node 5, it is possible to identify the location of the fault, either in the node 5 or in the optical transmission line 2.

[0033] (Variation) In the optical system according to the present invention, it is preferable that the monitoring unit 7 has an optical spectrum analysis function. By collecting the optical signal spectrum together with the optical signal power from the signal collection terminal p of the node 5, the monitoring unit 7 can identify the fault location that is difficult to identify using only the optical signal power, and can identify the fault location with higher accuracy.

[0034] As shown in Figure 10, the fault location process determines whether the waveform and optical signal-to-noise ratio (OSNR) change over time in addition to the optical reception power. If the optical amplifier downstream of the fault location uses the AGC method, as described above, the signal downstream of the fault location will experience a continuous abnormality in the temporal change in optical signal power, as shown in Figures 5, 8, and 9. However, if the optical amplifier uses the automatic level control (ALC) method, the decrease in optical signal power downstream of the fault location will be temporary, and it may be impossible to detect an abnormality in the temporal change in optical signal power even near the fault location (shown by a rectangle with a dotted pattern). Figure 10 shows the case where the optical amplifier in node 5 uses the ALC method and a filter abnormality has occurred in the WSS 63c of node 53. This may cause slight power fluctuations, making it difficult to determine whether the temporal change in optical signal power is abnormal. On the other hand, in the optical spectrum, if the signal is normal, the temporal change in the shape of the signal waveform containing the wavelengths λ10 and λ20 is small (within the steady-state fluctuation range) as shown in FIG. 11A. If the signal is abnormal, the abnormality detection time τ F (See Figures 4A and 4B)

[0035] In FIG. 10, the waveform is abnormal up to the transmitting end p41 of node 54, but becomes normal from the relay point p33 of node 53 upstream. Meanwhile, abnormalities in optical signal power can only be detected in the received power at the transmitting end p41 of node 54 and the transmitted power at the receiving end p34 of node 53. It is highly likely that an abnormality will not be detected in the OSNR. If an abnormality is detected in the optical signal power, the fault location can easily be identified between the signal collecting terminals p33 and p34. However, even if no abnormality is detected in the temporal change in optical signal power—in other words, if no abnormality is detected in the temporal change in optical signal power or if an abnormality is detected only at the signal collecting terminals p34 and p41—the only WSS between the signal collecting terminals p33 and p41 where the temporal change in the waveform can be distinguished as abnormal or normal—can be identified as the fault location. Even if an abnormality is detected in the OSNR, if an abnormality is detected in the waveform, the WSS can also be identified as the fault location.

[0036] FIG. 12 shows a case where the optical amplifier of node 5 is an ALC type, as in FIG. 10, and a noise abnormality occurs in the optical amplifier 63d of node 53. This can cause instantaneous power fluctuations when amplification loss temporarily leaks out, making it difficult to determine whether the abnormality is in the temporal change in optical signal power. On the other hand, in the optical spectrum, if the signal is normal, the temporal change in noise (OSNR) generated along with the signal waveform containing the wavelengths λ10 and λ20 is small (within the steady-state fluctuation range) as shown in FIG. 13A, and if the signal is abnormal, the abnormality detection time τ F (See Figures 4A and 4B) The degradation of OSNR increases.

[0037] In FIG. 12, the OSNR is abnormal up to the transmitting end p41 of node 54, but becomes normal from the relay point p33 of node 53 upstream. On the other hand, abnormalities can be detected in the optical signal power only in the received power at the transmitting end p41 of node 54 and the transmitted power at the receiving end p34 of node 53. However, no abnormalities can be detected in the waveform. If an abnormality is detected in the optical signal power, the fault location can easily be identified between the signal collecting terminals p33 and p34. However, even if no abnormality is detected in the temporal change in the optical signal power, in other words, if no abnormality is detected in the temporal change in the optical signal power or if an abnormality is detected only at the signal collecting terminals p34 and p41, the optical amplifier 63d, which is the only optical amplifier between the signal collecting terminals p33 and p41 where the temporal change in the OSNR can be distinguished as abnormal or normal, can be identified as the fault location.

[0038] Figure 14A shows the state of optical signal power, waveform, and time-varying OSNR when an optical fiber in node 53 has a fault. In Figure 14A, the optical amplifier in node 5 uses the AGC method. Therefore, as in Figure 9, the abnormality / normality of the time-varying optical signal power can be determined between signal collection terminals p32 and p33 on the transmitting and receiving sides of the optical fiber where the fault occurs. On the other hand, if the optical amplifier downstream of the faulty location uses the AGC method, no abnormality will be detected in the time-varying waveform and OSNR.

[0039] Like FIG. 14A, FIG. 14B shows the state of optical signal power, waveform, and temporal changes in OSNR when an optical fiber in node 53 has failed. However, in FIG. 14B, the optical amplifier in node 5 uses the ALC method. In this case, an abnormality in the temporal change in optical signal power is detected only at signal collection terminal p33 near the receiving side (downstream side) of the optical fiber where the failure occurs. On the other hand, if the optical amplifier downstream of the failed location uses the ALC method, an abnormality in the temporal change in OSNR is detected downstream from signal collection terminal p41, which is downstream of optical amplifier 63d, the first optical amplifier downstream of the failed optical fiber, due to a power decrease caused by the failed optical fiber. However, no abnormality is detected in the temporal change in the waveform.

[0040] Like FIG. 12, FIG. 15 illustrates a case where a noise abnormality occurs in an optical amplifier within node 53. However, the abnormality occurs in the upstream optical amplifier 63a. If the amplification loss of the optical amplifier 63a temporarily leaks out and the WSS 63b downstream of the optical amplifier 63a does not adjust the attenuation or there is a control lag, instantaneous power fluctuations occur. As a result, if the optical amplifier 63a uses the AGC method, an abnormality in the temporal change in optical signal power is detected only at the signal collection terminals p32 and p33 near the downstream side of the WSS 63b. Furthermore, an abnormality in the temporal change in OSNR is detected downstream from the signal collection terminal p33. On the other hand, if the optical amplifier 63a uses the ALC method, no abnormality is detected in the temporal change in optical signal power.

[0041] Like Fig. 10, Fig. 16 shows a case where a filter abnormality occurs in a WSS within node 53. However, the abnormality occurs in the upstream WSS 63b. If the attenuation adjustment of WSS 63b does not cause even slight power fluctuations, no abnormality in the temporal change in optical signal power is detected at signal collection terminals p32 and p33 located downstream of WSS 63b. However, like Fig. 10, an abnormality in the temporal change in waveform is detected downstream from signal collection terminal p33 located downstream of WSS 63b.

[0042] In this way, by observing the change over time in the optical signal power, or further the change over time in the waveform and OSNR, it is possible to identify the fault location from the suspected fault component 50a. Note that here, the change over time in the optical signal power etc. at the signal collection terminal p is observed sequentially from the downstream side of the suspected fault component 50a, but it may also be observed from the upstream side, or may be observed simultaneously at two or more locations in parallel.

[0043] In addition, in the suspected-fault component extraction process, a component that does not contain a fault location may be extracted as a suspected-fault component. For example, as shown in FIG. 3, when degradation of the signal quality of the wavelengths λ10 and λ20 is detected, component 50a, which constitutes a common optical path for λ10 and λ20, is extracted as a suspected-fault component. However, if the fault location cannot be identified in this component 50a, that is, if an abnormality is detected in the temporal change of optical signal power, etc., at all signal collection terminals p of component 50a, the fault location may be located upstream of component 50a, in the range from node 51 to WSS 62c of node 52, which constitutes the optical path for λ10. Therefore, this range is extracted as a second suspected-fault component, and the fault location identification process is executed. In this way, in the suspected-fault component extraction process, first, the component that shares the most optical paths of the wavelengths where degradation of signal quality is detected is extracted as the most likely suspected-fault component. If the fault location identification process cannot identify the fault location, the component that shares the next most optical paths is extracted as the second suspected-fault component. In this case, if an abnormality is detected in the temporal change of optical signal power, etc. at all signal collection terminals p in the previous fault location identification process, the upstream side is extracted, and if no abnormality is detected, the downstream side is extracted.

[0044] Furthermore, there are cases where degradation in signal quality is not detected at the wavelength of the optical path passing through the fault location, but is detected at an adjacent wavelength. Here, we will explain an example in which the monitoring unit 7c detects degradation in signal quality at the wavelength λ20 from the transponder device 35 in the optical transmission system 1A shown in Figure 17. If the fault location cannot be identified from component 50a constituting the optical path of λ20, even if degradation in signal quality at the wavelength λ21 adjacent to λ20 is not detected, the fault may be contained in component 50b constituting the optical path of this λ21. Therefore, component 50b is extracted as the next suspected fault component, and fault location identification processing is performed. Such degradation in signal quality at an adjacent wavelength can be detected, for example, when power increases due to a WSS failure.

[0045] 〔effect〕 The effects of the optical transmission system according to the present invention will be described below. The optical transmission system 1 according to the present invention has a plurality of nodes 3 and 5 interconnected by an optical transmission path 2, and includes monitoring units 7a, 7b, 7c, and 71-75 provided in each of the nodes 3 and 5 for collecting signal information in time series at the transmitting and receiving ends of the node and at least one signal collection terminal p between devices within the node, and an OpS 8 for controlling the monitoring units 7a, 7b, 7c, and 71-75. The OpS 8 executes a suspected-fault component extraction process for extracting a component 50a that is suspected to contain a fault location by having the monitoring units 7a, 7b, and 7c observe signal information at the receiving ends of a component consisting of one or more nodes 5 and the optical transmission path 2 between the nodes 5 and 5, and a fault location identification process for identifying the fault location in the extracted component 50a by having the monitoring units 72-75 observe temporal changes in the signal information at the signal collection terminals p of the nodes 52-55 and detecting abnormalities in the temporal changes in the signal information.

[0046] In this way, according to the optical transmission system 1 of the present invention, the fault location is first narrowed down on a component-by-component basis, and the fault location is identified by limiting it to these suspected faulty components, so that the fault location can be identified with high accuracy and scalability can be improved.

[0047] Furthermore, in the optical transmission system 1 according to the present invention, the monitoring units 71 to 75 perform optical spectrum analysis to acquire the waveform and optical signal-to-noise ratio of the collected signals, and in the fault location identification process, the OpS 8 identifies the fault location by having the monitoring units 72 to 75 detect an abnormality in the temporal change of at least one of the signal output, signal input, waveform, and optical signal-to-noise ratio.

[0048] In this way, the monitoring units 71 to 75 have an optical spectrum analysis function, so that it is possible to identify a fault location that is difficult to identify using only the optical signal power, and also possible to identify the fault location with higher accuracy.

[0049] Furthermore, in the optical transmission system 1 according to the present invention, when the OpS8 does not identify a fault location from the suspected-fault component 50a through the fault location identification process, it executes the fault location identification process in a component other than the component 50a that includes at least one optical transmission path of the wavelength of the signal that the component 50a has determined through the suspected-fault component extraction process to contain a fault location, and at least one optical transmission path of a wavelength adjacent to the wavelength.

[0050] In this way, if the fault location cannot be identified through the fault location identification process, the suspected fault components to be targeted for the fault location identification process are extracted in sequence, and the fault location identification process is executed again, thereby enabling the fault location to be identified.

[0051] In the optical transmission system 1 according to the present invention, the monitoring units 72 to 75 monitor the time change of the signal information in the fault location identification process based on the abnormality detection time τ when the component 50a collected the signal that the component 50a determined to include the fault location. F Observation is carried out for a predetermined period before and after the event.

[0052] In this way, by limiting the time change in the signal information to a shorter time period in which an abnormality can be detected, the load on the fault location identification process can be reduced.

[0053] In the optical transmission system 1 according to the present invention, the monitoring units 72 to 75 detect an abnormality in the time variation of the signal information in the fault location identification process by detecting an abnormality at an abnormality detection time τ when the component 50a collects the signal that is determined to include a fault location. F The judgment is based on the range of time fluctuations in the period not including the above.

[0054] In this way, by determining whether a change in signal information over time is normal or abnormal based on the range of fluctuation during steady state, it is possible to reduce erroneous determinations.

[0055] Furthermore, in the optical transmission system 1 according to the present invention, the OpS 8 executes the suspected-fault component extraction process at a time granularity of less than 15 minutes, and the monitoring units 7a, 7b, 7c, 71 to 75 collect signal information at the signal collection terminal p at a time granularity that is the same as or shorter than the time granularity of the suspected-fault component extraction process.

[0056] In this way, by collecting signal information and extracting suspected faulty components in short time periods, faults can be detected early, and the accuracy of fault location identification in the fault location identification process is improved.

[0057] The present invention is not limited to the above-described embodiments, and many modifications can be made by a person having ordinary skill in the art within the technical concept of the present invention. The following additional notes are provided regarding the above-described embodiment. [Note] (Additional note 1) An optical transmission system having a plurality of nodes interconnected by optical transmission lines, a monitoring means provided in each of the nodes for collecting signal information in time series at at least one signal collection point between a transmitting / receiving end of the node and a device within the node, and a control means for controlling the monitoring means; The control means executes a suspected fault component extraction process that extracts components that are presumed to contain a fault location by having the monitoring means observe signal information at the receiving end of a component consisting of one or more nodes and optical transmission paths between the nodes, and a fault location identification process that identifies the fault location in the extracted component by having the monitoring means observe temporal changes in signal information at the signal collection point of each node and detect abnormalities in the temporal changes in the signal information. (Additional note 2) the monitoring means performs optical spectrum analysis to obtain waveforms and optical signal-to-noise ratios of the collected signals; The optical transmission system according to claim 1, wherein the control means, in the fault location identification process, causes the monitoring means to detect an abnormality in a temporal change in at least one of signal output, signal input, waveform, and optical signal-to-noise ratio, thereby identifying the fault location. (Additional note 3) The optical transmission system according to claim 1 or 2, wherein, when the fault location identification process does not identify the fault location from the component, the control means executes the fault location identification process in a component other than the component, including at least one optical transmission path of a signal wavelength determined in the suspected-fault component extraction process to contain the fault location in the component, and at least one optical transmission path of a wavelength adjacent to the wavelength. (Additional note 4) The optical transmission system according to any one of claims 1 to 3, wherein the monitoring means, in the fault location identification process, observes the temporal change in the signal information for a predetermined period before and after the time when the component collected the signal that was determined to contain the fault location. (Additional note 5) The optical transmission system according to any one of appendix 1 to appendix 4, wherein the monitoring means, in the fault location identification process, determines abnormalities in the temporal changes of the signal information based on the width of time fluctuations in a period that does not include the time when the component collected the signal that was determined to contain the fault location. (Additional note 6) 1. A fault location method for identifying a fault location in an optical transmission system having a plurality of nodes interconnected by optical transmission paths, comprising: a collection step of collecting signal information in time series at at least one signal collection point between the transmitting and receiving ends of each node and devices within the node; a suspected fault component extraction step of observing signal information at a receiving end of a component consisting of one or more nodes and optical transmission paths between the nodes, and extracting a component that is estimated to include a fault location; a fault location identification step of observing temporal changes in signal information at the signal collection point of each node in the extracted component and detecting abnormalities in the temporal changes in the signal information to identify the fault location. (Additional note 7) A fault location identification method according to appended claim 6, in which, if the fault location is not identified in the fault location identification step, the fault location identification step is executed in a component other than the component that includes at least one optical transmission path of the wavelength of the signal determined in the suspected-fault component extraction step that the component contains the fault location, and at least one optical transmission path of a wavelength adjacent to the wavelength. [Explanation of symbols]

[0058] 10 Optical Transmission Systems 1,1A Optical Transmission System (L0 / L1 Network) 2. Optical transmission line (optical fiber) 3, 31, 32, 35, 36 Transponder device 31a, 31b, 32b, 32c, 35a, 35c, 35d, 36d transponders 41,42,45,46 Optical multiplexer / demultiplexer 50a, 50b Suspected faulty component 5,51,52,53,54,55,56,57 nodes 7a, 7b, 7c Monitoring unit (monitoring means) 7,71,72,73,74,75,76,77 Monitoring unit (monitoring means) 8 OpS (Control Measures)

Claims

1. An optical transmission system having a plurality of nodes interconnected by optical transmission lines, a monitoring means provided in each of the nodes for collecting signal information in time series at at least one signal collection point between a transmitting / receiving end of the node and a device within the node, and a control means for controlling the monitoring means; The control means executes a suspected fault component extraction process in which the control means causes the monitoring means to observe signal information at the receiving ends of two or more optical paths of a component consisting of one or more nodes and optical transmission paths between the nodes, and in two or more optical paths in which degradation of signal quality has been detected at the receiving ends, extracts components within the route range of a common optical path as components presumed to contain a fault location, and a fault location identification process in which the monitoring means observes temporal changes in signal information at the signal collection point of each node in the extracted components to detect abnormalities in the temporal changes in the signal information, thereby identifying the fault location.

2. the monitoring means performs optical spectrum analysis to obtain waveforms and optical signal-to-noise ratios of the collected signals; 2. The optical transmission system according to claim 1, wherein the control means locates the fault location by causing the monitoring means to detect an abnormality in a temporal change in at least one of a signal output, a signal input, a waveform, and an optical signal-to-noise ratio in the fault location identification process.

3. 3. The optical transmission system of claim 1, wherein, when the fault location identification process does not identify the fault location from the component, the control means executes the fault location identification process on a component other than the component that includes at least one optical transmission path of a signal wavelength determined in the suspected-fault component extraction process to contain the fault location in the component, and at least one optical transmission path of a wavelength adjacent to the wavelength.

4. 4. The optical transmission system according to claim 1, wherein the monitoring means, in the fault location identification process, observes the temporal changes in the signal information for a predetermined period before and after the time when the component collected the signal that was determined to contain the fault location.

5. 5. The optical transmission system according to claim 1, wherein the monitoring means, in the fault location identification process, determines whether an abnormality in the temporal change of the signal information is detected based on the width of time fluctuation in a period that does not include the time when the component collected the signal that was determined to contain the fault location.

6. 1. A fault location method for identifying a fault location in an optical transmission system having a plurality of nodes interconnected by optical transmission paths, comprising: a collection step of collecting signal information in time series at at least one signal collection point between a transmitting / receiving end of each node and a device within the node; a suspected fault component extraction step of observing signal information at receiving ends of two or more optical paths of a component consisting of one or more nodes and optical transmission paths between the nodes, and extracting components within a range of a common optical path route in two or more optical paths in which degradation of signal quality has been detected at the receiving ends as components estimated to include a fault location; a fault location identification step of observing temporal changes in signal information at the signal collection point of each node in the extracted component and detecting abnormalities in the temporal changes in the signal information to identify the fault location.

7. 7. The fault location method according to claim 6, wherein, if the fault location is not identified in the fault location identification step, the fault location identification step is executed in a component other than the component that includes at least one optical transmission path of a wavelength of a signal determined in the suspected fault component extraction step to contain the fault location in the component, and at least one optical transmission path of a wavelength adjacent to the wavelength.

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