Abnormal location narrowing device and abnormal location narrowing method for optical transmission system

Abstract

To narrow down a suspected portion even in a case where an abnormality occurs at a plurality of locations at the same time in a plurality of optical paths.SOLUTION: An abnormal location narrowing-down device 10 of an optical transmission system includes: a path degradation determination part 11 that determines whether or not there is a section in which all degraded paths, which are optical paths with degraded quality, commonly pass when an abnormality occurs at a plurality of locations at the same time; and a suspected portion estimation part 12 that, when there is no section through which all the degraded paths commonly pass, executes a matching determination process of determining whether or not all the degraded paths match all assumed degraded paths in which the selected candidate section is a suspected portion, repeats the matching determination process while changing the combination of the candidate sections when the selected candidate sections do not satisfy the condition, and estimates each of the selected candidate sections as a suspected portion when the selected candidate sections satisfy the condition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for narrowing down an abnormality in an optical transmission system. [Background technology]

[0002] Transmission equipment in optical transmission systems constantly measures various conditions, such as signal quality, and stores the information as PM (Performance Metric) information. However, there are also abnormalities that do not change the PM information. For example, a silent fault is a fault in which no equipment in the network notifies the network operator, etc., despite the occurrence of a fault. Conventionally, in optical networks, in response to silent faults and the like in optical transmission equipment, there have been proposed techniques for narrowing down suspected sections based on the accommodation relationships of affected optical paths and ODU (Optical channel Data Unit) paths (see Patent Document 1 and Non-Patent Document 1), and techniques for narrowing down suspected sections based on the accommodation relationships of OTU (Optical channel Transport Unit) paths (see Patent Document 2). These techniques enable early identification of the faulty part using optical signal characteristic data and optical path accommodation relationships. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-064160 [Patent Document 2] Japanese Patent Publication No. 2020-088628 [Non-patent literature]

[0004] [Non-Patent Document 1] Takuki Date, Hiroshi Yamamoto, Aki Fukuda, Shohei Kamamura, Rie Hayashi, Yoshihiko Uematsu, "Efficient Method for Identifying Fault Location in Optical Networks by Complementing Information Between Layers," IEICE Technical Report, NS2016-99, pp.57-62, October 2016. Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional technology, the detection of optical path degradation is used as a trigger to find the section that all optical paths that simultaneously detected degradation pass through in common, and the found section is then determined to be the suspect location. There is no problem if the abnormality occurs in one section, but if abnormalities occur in multiple locations at the same time, there is a possibility that there is no section that all optical paths that detected degradation (degraded paths) pass through in common. If there is no section that all degraded paths pass through in common, conventional technology cannot narrow down the suspect location.

[0006] Furthermore, in conventional technology, when simultaneous degradation is detected, if the section shared by multiple degraded paths is extracted and the section with the largest number of shared degraded paths is determined to be the suspected section, there is a possibility that the wrong section will be determined to be the suspected section.

[0007] Therefore, an object of the present invention is to solve the above problem and narrow down the suspected locations even in cases where abnormalities occur at multiple locations simultaneously in multiple optical paths. [Means for solving the problem]

[0008] The abnormality location narrowing device for an optical transmission system of the present invention is characterized by comprising: a path degradation determination unit that, when abnormalities occur at multiple locations simultaneously, determines whether there is a section through which all of the degraded paths, which are optical paths with degraded communication quality, pass in common, based on the network topology and optical path route and wavelength setting information; and a suspected location estimation unit that, if it is determined that there is no section through which all of the degraded paths pass in common, selects multiple different candidate sections and performs a matching determination process to determine whether the condition is met under which all of the assumed degraded paths, which are optical paths that are assumed when each of the selected candidate sections is considered to be a suspected location, match all of the degraded paths; if the condition is not met in the matching determination process, repeats the matching determination process while changing the combination of multiple different candidate sections; and if the condition is met in the matching determination process, estimates that each of the multiple different candidate sections selected at that time is a suspected location. [Effects of the Invention]

[0009] According to the present invention, even in cases where abnormalities occur at multiple locations simultaneously in multiple optical paths, it is possible to narrow down the suspected locations. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of an optical transmission system including an abnormality location narrowing down device according to an embodiment of the present invention; [Figure 2] 10 is a flowchart showing a flow of processing by the abnormality location narrowing down device. [Figure 3] (a) is an example of a network structure, and (b) is an example of an optical path. [Figure 4] 10 is a flowchart showing a processing flow according to a comparative example. [Figure 5] FIG. 1 is a schematic diagram illustrating an example of deterioration of an optical path. [Figure 6] FIG. 6 is an explanatory diagram of a process for narrowing down suspected locations from the degradation paths shown in FIG. 5. [Figure 7] FIG. 10 is a schematic diagram showing another example of deterioration of an optical path. [Figure 8]FIG. 10 is an explanatory diagram of a process for narrowing down suspected parts using a comparative example. [Figure 9] FIG. 10 is an explanatory diagram of a first match determination process performed by the abnormality location narrowing down device. [Figure 10] FIG. 10 is an explanatory diagram of the n-th match determination process performed by the abnormality location narrowing down device. [Figure 11] FIG. 2 is a hardware configuration diagram illustrating an example of a computer that realizes the functions of the abnormality location narrowing down device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The abnormality location narrowing down device according to this embodiment will be described in detail below with reference to the drawings. [System configuration overview] As shown in FIG. 1, the optical transmission system 1 includes a network controller 2 that monitors an optical network 3 . The optical network 3 comprises a plurality of nodes 5 in which optical paths are set, and links 7 connecting the nodes 5. Here, the nodes 5 are configured, for example, with optical cross-connects (ROADM: Reconfigurable Optical Add / Drop Multiplexer), and the links 7 are configured with optical fiber cables. Note that the nodes that are the end points of the optical paths are equipped with transponders in addition to optical cross-connects. The number of nodes is arbitrary. When the nodes shown in FIG. 1 are to be distinguished, they are written as nodes A to L, and when they are not to be distinguished, they are written as node 5.

[0012] Like a general network controller, the network controller 2 stores network topology, optical path routes, wavelength setting information, etc., and has an optical path setting function, etc. In addition, the network controller 2 of this embodiment has a function as an abnormality location narrowing down device 10.

[0013] In this embodiment, the degraded path detection unit that detects degradation of the optical path may be installed either inside or outside the abnormality location narrowing down device 10, but as an example, it is assumed that the degraded path detection unit is installed in node 5 (however, in the transponder of the node that is the end point of the path). When the degraded path detection unit (not shown) detects degradation, it issues an alarm to the network controller 2. The abnormality location narrowing down device 10 determines the degradation of the path by receiving this alarm. Note that the nodes that are either end points of the optical path (for example, node A, node B, node D, node E, node I, node K, and node L) each represent a node equipped with both an optical cross connect and a transponder. Each of the other nodes represents a node equipped with an optical cross connect.

[0014] [Configuration of the anomaly location narrowing down device] The abnormality location narrowing device 10 includes a path degradation determining unit 11 and a suspected location estimating unit 12. When abnormalities occur at multiple locations simultaneously, the path degradation determination unit 11 determines whether there is a section through which all of the degraded paths, which are optical paths with degraded communication quality, pass in common, based on the network topology and the optical path route and wavelength setting information.

[0015] When it is determined that there is no section through which all the degraded paths pass in common, the suspected section estimation unit 12 performs a process to estimate a suspected section. The suspected section estimation unit 12 selects a plurality of different candidate sections and uses the optical paths (hereinafter referred to as assumed degraded paths) that are assumed when each of the selected candidate sections is deemed to be a suspected section to estimate the suspected section. Note that an optical path in which degradation has actually been detected for an assumed degraded path is referred to as a detected degraded path or simply a degraded path. The suspected section estimation unit 12 performs a match determination process to determine whether a match condition is met between all of the assumed degraded paths and all of the degraded paths. If the condition is not met in the match determination process, the suspected section estimation unit 12 repeats the match determination process while changing the combination of the different plurality of candidate sections, and if the condition is met in the match determination process, it estimates that each of the different plurality of candidate sections selected at that time is a suspected section.

[0016] The suspected portion estimation unit 12 preferably sets the initial value of the control variable for the repeated processing to 2, selects the same number of candidate sections as the control variable, and executes the match determination processing. If the conditions are not satisfied in the match determination processing, the match determination processing is repeated while increasing the control variable by 1 up to a predetermined upper limit value. Hereinafter, the control variable for the repeated processing is represented as k, and the predetermined upper limit value is represented as the maximum number of multiple faults K. The maximum number of multiple faults K is a parameter that is given in advance based on the failure rate of the network or device. The maximum number of multiple faults K is expected to be, for example, 2 (double faults) or 3 (triple faults). Note that upper and lower case letters are distinguished.

[0017] [Operation of the anomaly location narrowing down device] Next, the operation of the abnormality location narrowing down device will be described with reference to Fig. 2 (and Fig. 1 as needed). Fig. 2 is a flowchart showing the flow of processing by the abnormality location narrowing down device. In the anomaly location narrowing device 10, the path degradation determination unit 11 detects degradation of an optical path (step S101). Then, the path degradation determination unit 11 performs a process of extracting a section through which all optical paths with degraded communication quality (detected degraded paths) commonly pass (step S102). Here, when abnormalities occur at multiple locations simultaneously, the path degradation determination unit 11 determines whether there is a section through which all degraded paths commonly pass, based on the network topology and the optical path route and wavelength setting information. Then, if the path degradation determination unit 11 determines that there is a section through which all degraded paths commonly pass (step S103: Yes), it determines that the extracted section is a suspected location (step S104). On the other hand, if the path degradation determination unit 11 determines in step S103 that there is no section through which all degraded paths commonly pass (step S103: No), it passes the process to the suspected location estimation unit 12.

[0018] The suspected location estimation unit 12 first extracts all sections through which the optical path passes (step S110). Then, the suspected location estimation unit 12 repeats the following matching determination process while increasing the control variable k from 2 to 1 up to the maximum number of multiple faults K, until the condition that the assumed degraded path and the detected degraded path match is satisfied (step S120).

[0019] In this matching process, the suspected portion estimation unit 12 selects k different sections from all the extracted sections and compares the assumed degradation path and the detected degradation path when the selected sections are determined to be suspected portions (step S121). If the suspected portion estimation unit 12 determines that the assumed degradation path and the detected degradation path do not match (step S122: No), it changes the combination of the k different sections and executes the process of step S121. On the other hand, if the suspected portion estimation unit 12 determines that the assumed degradation path and the detected degradation path match (step S122: Yes), it determines that the k different sections selected at that time are suspected portions (step S130).

[0020] Next, a specific example (example) of the method for narrowing down an abnormality location according to this embodiment will be described. First, specific examples of the underlying network configuration, optical paths, and locations where abnormalities occur will be described. (Network configuration) FIG. 3(a) shows an example of a network structure, and FIG. 3(b) shows an example of an optical path. In the optical network 3, the nodes 5 are connected by optical fibers (links 7) as shown in Figure 3(a). For the sake of convenience, let us assume that the nodes 5 are arranged in a matrix of 4 rows and 3 columns.

[0021] In the first row of the matrix, node A is connected to node B via optical fiber, node B is connected to node C, and node C is connected to node D. Hereinafter, link 7 connecting node A and node B will be referred to as section A / B. In the first row of the matrix, sections A / B, B / C, and C / D are set.

[0022] From the first row to the second row of the matrix, node A is connected to node E, node B is connected to node F, node C is connected to node G, and node D is connected to node H. From the first row to the second row of the matrix, intervals A / E, B / F, C / G, and D / H are set.

[0023] In the second row of the matrix, node E is connected to node F, node F is connected to node G, and node G is connected to node H. In the second row of the matrix, intervals E / F, F / G, and G / H are set.

[0024] From the second to third row of the matrix, node E is connected to node I, node F is connected to node J, node G is connected to node K, and node H is connected to node L. From the second to third row of the matrix, intervals E / I, F / J, G / K, and H / L are set.

[0025] In the third row of the matrix, node I is connected to node J, node J is connected to node K, and node K is connected to node L. In the third row of the matrix, intervals I / J, J / K, and K / L are set. In this example, a total of 17 intervals are set as above.

[0026] (Optical Path) As shown in FIG. 3(b), it is assumed here that four optical paths, ie, a path 9-1, a path 9-2, a path 9-3, and a path 9-4, are set. The path 9-1 passes through node A, node B, node C, node G, node H, and node L. That is, the path 9-1 passes through sections A / B, B / C, C / G, G / H, and H / L. The path 9-2 passes through the node E, the node F, the node G, the node H, and the node D. That is, the path 9-2 passes through the sections E / F, F / G, G / H, and D / H. The path 9-3 passes through the node I, the node J, the node F, and the node B. That is, the path 9-3 passes through the sections I / J, F / J, and B / F. The path 9-4 passes through the node E, the node F, the node J, and the node K. That is, the path 9-4 passes through the sections E / F, F / J, and J / K.

[0027] (Comparative Example) Here, for comparison with the embodiment of the abnormality location narrowing down device 10, a device (comparative example) not including the suspected location estimation unit 12 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the flow of processing in the comparative example. As shown in Fig. 4, in the comparative example, if there is no section through which all degraded paths pass in common (step S103: No), the section through which the most commonly passed degraded optical paths pass is extracted (step S201), and the extracted section is determined to be the suspected location (step S104). Note that the processing other than step S201 in Fig. 4 is the same as the processing shown in Fig. 2, and therefore description thereof will be omitted.

[0028] (When the abnormality occurs in one location) An example in which an anomaly occurs in one location will be described with reference to Fig. 5. As shown in Fig. 5, when an anomaly occurs in section G / H, degradation of path 9-1 passing through section G / H is detected, and degradation of path 9-2, which also passes through section G / H, is also detected. In other words, degradation of paths 9-1 and 9-2 may be detected simultaneously. In this case, paths 9-1 and 9-2 each become degraded paths. Note that X in Fig. 5 indicates a degraded path. When degradation of optical paths is detected simultaneously, the section in which the anomaly occurred is unknown, so the anomaly location narrowing device 10 estimates the suspected location (the section in which the anomaly occurred) based on the network topology and the optical path route and wavelength setting information.

[0029] The process of narrowing down the sections through which paths 9-1 and 9-2 (degraded paths) commonly pass by the anomaly location narrowing device 10 will be described with reference to FIG. 6. In FIG. 6, each column lists all the sections in the optical network 3 shown in FIG. 3(a), and each row lists all the optical paths shown in FIG. 3(b). A cell containing "1" means that the optical path represented in that row passes through the section represented in that column, and a blank cell means that the optical path represented in that row does not pass through the section represented in that column. The thick lines in the rectangles indicate that paths 9-1 and 9-2 are detected degraded paths. Note that in this example, paths 9-3 and 9-4 are not degraded paths. In FIG. 6, suspected locations are indicated by hatching.

[0030] From Figure 6, it can be seen that the section through which paths 9-1 and 9-2 (degraded paths) pass in common is section G / H. In this way, even if degradation is detected in paths 9-1 and 9-2 at the same time, if an abnormality occurs in only one section as shown in Figure 5, the suspected location will match the correct answer (Figure 5) in both the embodiment (Figure 2) and the comparative example (Figure 4). However, if abnormalities occur in multiple locations at the same time, there is a possibility that there is no section through which all optical paths in which degradation is detected pass in common.

[0031] (When the abnormality occurs in two places) An example in which anomalies occur in two locations will be described with reference to Fig. 7. As shown in Fig. 7, if anomalies occur in section F / J in addition to section G / H at the same time, paths 9-1, 9-2, 9-3, and 9-4 will all become degraded paths. Also, there is no section through which all the degraded paths pass.

[0032] Under the conditions shown in Fig. 7, in the comparative example (Fig. 4), as described above, if there is no section through which all degraded paths pass in common (step S103: No), the section through which the most commonly passed degraded optical paths pass is extracted (step S201), and the extracted section is determined to be a suspected location (step S104). The processing by this comparative example (Fig. 4) will be described with reference to Fig. 8. Note that the thick lines in the rectangles indicate that paths 9-1, 9-2, 9-3, and 9-4 are detected degraded paths, respectively. In the comparative example (Fig. 4), as shown by the hatching in Fig. 8, three sections are estimated to be suspected locations, and the suspected locations cannot be correctly narrowed down.

[0033] On the other hand, in the embodiment (Figure 2), as described above, if there is no section through which all degradation paths pass in common (step S103: No), the suspected area estimation unit 12 repeats the matching determination process until the condition for matching between the assumed degradation path and the detected degradation path is met (step S120). This match determination process will be described with reference to Fig. 9 and Fig. 10 under the conditions shown in Fig. 7. Fig. 9 is an explanatory diagram of the first match determination process performed by the abnormal part narrowing down device 10. Fig. 10 is an explanatory diagram of the nth match determination process performed by the abnormal part narrowing down device 10, where n is a predetermined natural number.

[0034] Here, as an example, it is assumed that the maximum number of multiple faults K is 2. Furthermore, the initial value of the control variable k is 2. The suspected portion estimation unit 12 of the abnormal portion narrowing down device 10 selects two sections as candidate sections according to the value of the control variable k. In the first iteration, the suspected portion estimation unit 12 selects sections A / B and B / C as candidate sections for the suspected portion, as shown by hatching in Fig. 9. In this case, only path 9-1 is assumed to be degraded, so it does not match all of the detected degraded paths.

[0035] From the second iteration onwards, although not shown in the figure, the suspected area estimation unit 12 similarly selects two sections as candidate sections corresponding to the value of the control variable k, and determines whether all of the expected degraded paths that are expected to degrade paths passing through the selected sections match all of the detected degraded paths.

[0036] Then, in the nth iteration, the suspected section estimation unit 12 selects sections G / H and F / J as candidate sections for the suspected section, as shown by hatching in FIG. 10. In this case, the assumed degraded paths that are assumed to be paths passing through the selected sections are path 9-1, path 9-2, path 9-3, and path 9-4. In other words, since all paths are assumed to be degraded, all of the assumed degraded paths match all of the detected degraded paths. As a result, the suspected section estimation unit 12 determines sections G / H and F / J as suspected sections, thereby correctly narrowing down the suspected sections.

[0037] In the description of the embodiment (FIG. 2) above, all sections through which the optical paths pass are extracted in step S110 before the suspected section estimation unit 12 repeats the matching determination process, but this embodiment is not limited to this. In step S110, the suspected section estimation unit 12 may select candidate sections from only all sections arranged on the routes of the group of optical paths whose communication quality has deteriorated, and then perform the matching determination process. Specifically, of the total 17 sections set in the optical network 3 shown in FIG. 3(b), five sections, namely section C / D, section A / E, section E / I, section G / K, and section K / L, are not routes of degraded paths. Therefore, in this case, the suspected section estimation unit 12 can exclude these five sections in advance in the matching determination process and extract the remaining 12 sections. By doing so, the amount of calculation can be significantly reduced compared to when all 17 sections are determined to be suspected sections of multiple faults. For example, if the number of sections in the network is L and the number of sections through which any of the degraded optical paths pass is generalized to M (M < L), the amount of calculation to extract all sections is O(L 2 ), but the computational complexity of extracting only the sections through which any of the degraded optical paths pass is O(M 2 ) can be used.

[0038] [Hardware configuration] The abnormality location narrowing down device according to the embodiment is realized by, for example, a computer 900 configured as shown in Fig. 11. Fig. 11 is a hardware configuration diagram showing an example of the computer 900 that realizes the functions of the abnormality location narrowing down device 10 according to the embodiment. The computer 900 has a CPU (Central Processing Unit) 901, a ROM (Read Only Memory) 902, a RAM (Random Access Memory) 903, an HDD (Hard Disk Drive) 904, an input / output I / F (Interface) 905, a communication I / F 906, and a media I / F 907.

[0039] The CPU 901 operates based on a program stored in the ROM 902 or the HDD 904. The ROM 902 stores a boot program executed by the CPU 901 when the computer 900 is started up, programs related to the hardware of the computer 900, and the like.

[0040] The CPU 901 controls an input device 910 such as a mouse or keyboard, and an output device 911 such as a display or printer, via an input / output I / F 905. The CPU 901 acquires data from the input device 910 via the input / output I / F 905, and outputs generated data to the output device 911. Note that a GPU (Graphics Processing Unit) or the like may be used as a processor together with the CPU 901.

[0041] The HDD 904 stores programs executed by the CPU 901 and data used by the programs, etc. The communication I / F 906 receives data from other devices via the communication network 920 and outputs the data to the CPU 901, and also transmits data generated by the CPU 901 to other devices via the communication network 920.

[0042] The media I / F 907 reads a program or data stored in the recording medium 912 and outputs it to the CPU 901 via the RAM 903. The CPU 901 loads a program related to a target process from the recording medium 912 onto the RAM 903 via the media I / F 907, and executes the loaded program. The recording medium 912 is an optical recording medium such as a DVD (Digital Versatile Disc) or a PD (Phase Change Rewritable Disc), a magneto-optical recording medium such as an MO (Magneto Optical Disk), a magnetic recording medium, or a semiconductor memory.

[0043] For example, when the computer 900 functions as the abnormality location narrowing down device 10 according to the embodiment, the CPU 901 executes a program (abnormality location narrowing down program) loaded onto the RAM 903, thereby realizing the functions of the abnormality location narrowing down device 10. Furthermore, the HDD 904 stores data in the RAM 903. The CPU 901 reads and executes a program relating to a target process from the recording medium 912. In addition, the CPU 901 can also read a program relating to a target process from another device via the communication network 920.

[0044] [effect] As described above, the abnormality location narrowing device 10 of the optical transmission system 1 is characterized by comprising: a path degradation determination unit 11 that, when abnormalities occur at multiple locations simultaneously, determines whether there is a section through which all of the degraded paths, which are optical paths with degraded communication quality, pass in common, based on the network topology and the optical path route and wavelength setting information; and a suspected location estimation unit 12 that, if it is determined that there is no section through which all of the degraded paths pass in common, selects multiple different candidate sections and performs a match determination process to determine whether the condition is met where all of the assumed degraded paths, which are optical paths that are assumed when each of the selected candidate sections is considered to be a suspected location, match all of the degraded paths; if the condition is not met in the match determination process, repeats the match determination process while changing the combination of multiple different candidate sections; and, if the condition is met in the match determination process, estimates that each of the multiple different candidate sections selected at that time is a suspected location.

[0045] In this way, the anomaly location narrowing device 10 can use an assumed degraded path, which is an assumed path with multiple assumed abnormalities on the optical path, to compare it with a detected degraded path, which is an optical path in which degradation has actually been detected, to determine the impact of degradation on the optical path when multiple sections on the assumed degraded path have abnormalities. This allows the anomaly location narrowing device 10 to narrow down all abnormalities even when multiple failures occur. Therefore, by narrowing down the sections through which a group of paths whose quality has simultaneously deteriorated due to an abnormality in the optical transmission system 1 pass in common, the anomaly location narrowing device 10 can narrow down the abnormality even when the abnormality cannot be clearly detected by a device alarm, etc.

[0046] The abnormality location narrowing device 10 of the optical transmission system 1 is characterized in that the suspected location estimation unit 12 selects candidate sections from only all sections located on each route of the optical path group in which communication quality has deteriorated, and performs a matching determination process.

[0047] By doing this, the anomaly location narrowing down device 10 performs the match determination process by excluding in advance, from among the multiple sections that the suspected location estimation unit 12 assumes as anomaly locations when determining path degradation, sections that do not pass through the actually detected degraded path. In other words, the suspected location estimation unit 12 performs the match determination process only on the routes of the actually detected degraded paths, thereby reducing the number of brute-force determinations. Therefore, the anomaly location narrowing down device 10 can reduce the amount of calculation, thereby shortening the determination process time, reducing the processing load, and further improving scalability for candidate sections.

[0048] The abnormality location narrowing device 10 of the optical transmission system 1 is characterized in that the suspected location estimation unit 12 sets the initial value of the control variable to 2, selects the same number of candidate sections as the control variable, and performs a match determination process, and if the conditions are not met in the match determination process, repeats the match determination process while increasing the control variable by 1 up to a predetermined upper limit value.

[0049] In this way, the anomaly location narrowing-down device 10 has the suspected location estimation unit 12 check the control variables in ascending order of values, thereby reducing the time required and ensuring that no checks are overlooked. Furthermore, the suspected location estimation unit 12 executes a match determination process for all combinations of suspected locations up to a predetermined upper limit (maximum number of multiple faults K), with combinations of paths that are suspected to be degraded as the judgment target. Therefore, the anomaly location narrowing-down device 10 can narrow down the suspected locations even when anomalies occur at multiple locations simultaneously and there is no section through which all of the degraded optical paths pass in common.

[0050] 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. For example, in the optical transmission system 1 shown in Fig. 1, the network controller 2 that monitors all the nodes 5 functions as the abnormality location narrowing-down device 10, but the present invention is not limited to this. If there are different network controllers for each node group (for example, a controller for nodes A to D, a controller for nodes E to H, and a controller for nodes I to L in Fig. 1), an integrated network controller may be provided above these controllers, and the integrated network controller may have the function of the abnormality location narrowing-down device 10.

[0051] Furthermore, in the above embodiment, the path degradation detection unit is provided in the transponder that is the end point of the path, but it is also possible to use the following first, second, and third modified examples. (First Modification) When the degraded path detection unit is provided in the network controller 2 (abnormality location narrowing device 10), the network controller 2 periodically collects path quality information (PM information such as error rate) from the transponder (or the transponder via the node controller) and analyzes changes in the quality information to detect and determine path degradation.

[0052] (Second Modification) When implemented as an independent path degradation detection unit separate from the network controller 2, the independent path degradation detection unit periodically collects path quality information (PM information such as error rates) from the transponder (or the transponder via the node controller) and analyzes changes in the quality information to detect path degradation. At this time, the independent path degradation detection unit may perform advanced analysis such as machine learning. The independent path degradation detection unit may also perform processing such as excluding path degradation that is not clearly a failure by linking with a planned construction management system. When the independent path degradation detection unit detects degradation, it issues an alarm to the network controller 2. The network controller 2 receives this alarm and determines path degradation.

[0053] (Third Modification) A management system for customer anomaly reports may detect path degradation. When the management system for customer anomaly reports receives an anomaly report (a complaint about signal outages) from a customer, it determines that degradation has occurred in the path in question and issues an alarm to the network controller 2. Upon receiving this alarm, the network controller 2 determines that the path has deteriorated. [Explanation of symbols]

[0054] 1 Optical transmission system 2 Network Controller 3 Optical Network 5 nodes 7 Links 9-1, 9-2, 9-3, 9-4 Optical Path 10. Abnormality location narrowing device 11 Path degradation determination unit 12 Suspected location estimation section

Claims

1. a path degradation determination unit that, when abnormalities occur at multiple locations simultaneously, determines whether there is a section through which all of the degraded paths, which are optical paths with degraded communication quality, pass in common, based on the network topology and the optical path route and wavelength setting information; a suspected location estimation unit that, when it is determined that there is no section through which all of the degraded paths pass in common, selects a plurality of different candidate sections, and executes a matching determination process to determine whether a condition is met under which all of the assumed degraded paths, which are assumed optical paths when each of the selected candidate sections is assumed to be a suspected location, match all of the degraded paths; if the condition is not met in the matching determination process, repeats the matching determination process while changing the combination of the different plurality of candidate sections, and if the condition is met in the matching determination process, estimates that each of the different plurality of candidate sections selected at that time is a suspected location; 1. An abnormality location narrowing-down device for an optical transmission system, comprising:

2. The abnormality location narrowing device for an optical transmission system described in claim 1, characterized in that the suspected location estimation unit selects the candidate section from only all sections located on each route of a group of optical paths with degraded quality and performs the matching determination process.

3. The suspected location estimation unit sets the initial value of the control variable to 2, selects the same number of candidate sections as the control variable, and executes the matching determination process, and if the condition is not satisfied in the matching determination process, repeats the matching determination process while increasing the control variable by 1 up to a predetermined upper limit value, characterized in that the abnormality location narrowing down device for an optical transmission system described in claim 1 or claim 2.

4. An abnormality location narrowing method for an abnormality location narrowing device in an optical transmission system, comprising: The abnormality location narrowing down device is a step of determining, when abnormalities occur at multiple locations simultaneously, whether there is a section through which all of the quality-degraded optical paths pass in common, based on the network topology and the optical path route and wavelength setting information; When it is determined that there is no section through which all of the degraded paths pass in common, a process of selecting a plurality of different candidate sections and executing a matching determination process to determine whether or not a condition is met in which all of the assumed degraded paths, which are assumed optical paths when each of the selected candidate sections is assumed to be a suspected location, match all of the degraded paths; when the condition is not met in the matching determination process, the process of repeating the matching determination process while changing the combination of the different plurality of candidate sections; when the condition is met in the matching determination process, the process of estimating that each of the different plurality of candidate sections selected at that time is a suspected location; A method for narrowing down an abnormality in an optical transmission system, comprising:

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