Failure range identification system and failure range identification method for optical network

Abstract

The present invention facilitates the identification of a location where a failure has occurred in a case where a plurality of optical networks are directly connected to each other using an optical signal without an optical-electrical-optical signal conversion mechanism therebetween. This failure range identification system comprises: an error information transmission unit that transmits, to each of a plurality of optical networks, information about an error detected by a transponder at a transmission destination; an optical signal quality measurement unit that measures optical signal quality at least at an input location of each of the plurality of optical networks or at a boundary location between the plurality of optical networks; and an abnormality determination unit that determines, for each of the plurality of optical networks, whether there is an abnormality in the optical network on the basis of first optical signal quality measured at an input and second optical signal quality measured or estimated at an output. An estimated value of the optical signal quality is used as a normal value and compared with a measured value. The measured value when the optical signal quality is normal is compared with the measured value when an error occurred. Temporal changes of the optical signal quality are compared with a threshold value.

Description

Optical network fault range determination system and fault range determination method

[0001] The present invention relates to a system and method for fault scoping in optical networks.

[0002] For example, as in the optical network system 10A shown in Fig. 1, there is a case where multiple independent optical networks 11, 12, and 13 are interconnected to transmit information in the form of optical signals. A typical example is the case where optical networks 11, 12, and 13 operated by multiple different operating companies A, B, and C are interconnected, as shown in Fig. 1.

[0003] 1, within optical network 11, various information is transmitted in the form of optical signals using optical transmission line 14A, which is made up of optical fiber. Similarly, within optical network 12, various information is transmitted in the form of optical signals using optical transmission line 14B. Within optical network 13, various information is transmitted in the form of optical signals using optical transmission line 14C.

[0004] 1, transponders 15A and 15B are connected to one input end and the other output end of an optical network 11. Similarly, transponders 15C and 15D are connected to one input end and the other output end of an optical network 12. Transponders 15E and 15F are connected to one input end and the other output end of an optical network 13.

[0005] Each transponder 15A, 15C, and 15E on the input side of the optical network has the function of generating an optical signal modulated by an electrical signal containing information to be transmitted and transmitting the modulated optical signal to the optical fiber of the transmission path. Each transponder 15B, 15D, and 15F on the output side of the optical network converts an optical signal input from the optical fiber of the transmission path into an electrical signal and demodulates this electrical signal to obtain the received information. Each transponder 15B, 15D, and 15F on the output side also has the function of detecting errors in the transmitted information from the demodulated electrical signal.

[0006] In the optical network system 10A of Fig. 1, an optical signal output from the optical network 11 is converted into an electrical signal by transponder 15B and input to transponder 15C in the form of an electrical signal through the inter-network connection unit 16. Here, transponder 15B on the optical network 11 side can pass information about an error that has occurred on the optical network 11 side to transponder 15C on the downstream side. Also, an optical signal output from the optical network 12 is converted into an electrical signal by transponder 15D and input to transponder 15E in the form of an electrical signal through the inter-network connection unit 17. Transponder 15D on the optical network 12 side can pass information about an error that has occurred on the optical network 12 side to transponder 15E on the downstream side.

[0007] On the other hand, the technological concept of the All-Photonics Network (APN) aims to eliminate the optical-electrical-optical conversion that was previously required between networks in order to provide a low-latency, low-power-consumption end-to-end optical direct path between user terminals.

[0008] An example of the configuration of an optical network system 10B configured as an all-photonics network is shown in Fig. 2. In the optical network system 10B in Fig. 2, an optical signal output from an optical transmission line 14A of an optical network 11 passes through an inter-network connection unit 16 as an optical signal and is transferred to an optical transmission line 14B of the next optical network 12. Similarly, an optical signal output from an optical transmission line 14A of the optical network 12 passes through an inter-network connection unit 17 as an optical signal and is transferred to an optical transmission line 14C of the next optical network 13.

[0009] On the other hand, Non-Patent Document 1 discloses a technique related to a tool (GNPy) for estimating optical signal quality (GSNR: generalized signal-to-noise ratio) in an optical network.

[0010] A. Ferrari, et al., "GNPy: an open source application for physical layer aware open optical networks", Journal of Optical Communications and Networking, Vol. 12, No. 6, June 2020.

[0011] When a business company maintains and operates an optical network system, it is necessary to easily identify the location of a failure when a failure occurs. For example, when using the optical network system 10A shown in Figure 1, if a user transmits information via transponder 15A at the input of optical network 11 and delivers it to a terminal downstream of transponder 15F at the output of optical network 13, a situation such as that shown in Figure 3 may occur.

[0012] In the example of Figure 3, it is assumed that a failure has occurred at failure location 18 in optical network 12. Furthermore, due to the failure, "2" is detected as error count 15Fe at the position of transponder 15F. That is, transponder 15F can grasp the error based on the results of converting the received optical signal into an electrical signal and demodulating it. At the same time, "0", "0", "1", and "1" are detected as error counts 15Be, 15Ce, 15De, and 15E at the positions of the other transponders 15B, 15C, 15D, and 15E, respectively. In this case, because there is a difference between the two error counts 15Ce and 15De, it can be determined that a failure has occurred within optical network 12 and that no abnormalities exist in the other optical networks 11 and 13. In practice, the error count information detected by each transponder 15B, 15C, 15D, 15E, and 15F is transmitted to the downstream optical network, so that each optical network 11, 12, and 13 can determine whether or not there is an abnormality by comparing the error count at the input with the error count at the output.

[0013] On the other hand, if a failure occurs in the optical network system 10B of FIG. 2 , a situation such as that shown in FIG. 4 is assumed. In the example of FIG. 4 , it is assumed that a failure occurs at the failure location 18 of the optical network 12. Furthermore, because a "1" is detected as the error count 15Fe at the position of the transponder 15F due to the failure, it is possible to confirm that a failure has occurred. However, because there is no transponder at the point connecting the multiple optical networks 11, 12, and 13, it is difficult to identify which section of the multiple optical networks 11, 12, and 13 is causing the error count 15Fe detected by the transponder 15F. Therefore, it is necessary to investigate whether there is an abnormality in each of the optical networks 11 and 13 that do not include the failure location 18, which requires time and effort to identify the failure location 18.

[0014] In particular, in a situation where multiple optical networks 11, 12, and 13 are managed by different business companies A, B, and C, each of the business companies A, B, and C cannot easily determine whether the location of the abnormality belongs to an optical network managed by their own company or an optical network managed by another company.

[0015] The present invention has been made in consideration of the above situation, and aims to provide a system and method for locating the fault area of ​​an optical network that makes it easy to identify the location of a fault when multiple optical networks are directly connected by optical signals without the intervention of an optical-electrical-optical signal conversion mechanism.

[0016] (1) The optical network fault range identification system of the present invention is a fault range identification system that diagnoses an optical network system in which multiple optical networks, each transmitting information in the form of an optical signal, are connected to each other and signals are passed between the multiple optical networks while maintaining the form of the optical signal at the connection points between the multiple optical networks, and is characterized by comprising: an error information transmission unit that transmits information of an error detected at the transmission destination to each of the multiple optical networks; an optical signal quality measurement unit that measures the optical signal quality at the input point of each of the multiple optical networks or at the boundary point of the multiple optical networks; and an abnormality identification unit that identifies the presence or absence of an abnormality for each optical network based on a first optical signal quality measured at the input and a second optical signal quality measured or estimated at the output for each of the multiple optical networks.

[0017] (2) The method for identifying the extent of a fault in an optical network of the present invention is a method for diagnosing an optical network system in which a plurality of optical networks, each transmitting information in the form of an optical signal, are connected to one another and signals are handed over at connection points between the plurality of optical networks while maintaining the form of the optical signal, and is characterized by the following: transmitting information of an error detected at the transmission destination to each of the plurality of optical networks; measuring optical signal quality at the input point of each of the plurality of optical networks or at the boundary point of the plurality of optical networks; when an error is detected at the transmission destination, obtaining a first optical signal quality measured at the input and a second optical signal quality measured or estimated at the output for each of the plurality of optical networks; and identifying the presence or absence of an abnormality in each optical network based on the first optical signal quality and the second optical signal quality.

[0018] The optical network fault range identification system and fault range identification method of the present invention make it easy to identify the location of a fault when multiple optical networks are directly connected by optical signals without the use of an optical-electrical-optical signal conversion mechanism. That is, because the optical signal quality actually measured for each optical network can be obtained, it is possible to identify the presence or absence of an abnormality for each optical network based on the obtained optical signal quality, making it easy to identify the fault range within the entire network.

[0019] 1 is a schematic diagram showing an example of the configuration of a general optical network system. FIG. 1 is a schematic diagram showing an example of an optical network system configured as an APN. FIG. 2 is a schematic diagram showing an example of a fault state in the optical network system of FIG. 1. FIG. 3 is a schematic diagram showing an example of a fault state in the optical network system of FIG. 2. FIG. 4 is a block diagram showing an example of the configuration of an optical network system in an embodiment of the present invention. FIG. 5 is a block diagram showing characteristic functions included in the optical network system of FIG. 5. FIG. 6 is a flowchart showing characteristic operations in the optical network system of FIG. 5. FIG. 7 is a block diagram showing the configuration of an optical network system of Variation-1. FIG. 8 is a block diagram showing the configuration of an optical network system of Variation-2. FIG. 9 is a block diagram showing the configuration of an optical network system of Variation-3. FIG. 10 is a block diagram showing the configuration of an optical network system of Variation-4. FIG. 11 is a block diagram showing Example 1 of a connection between an optical transmission line and an optical signal measuring device in an optical network system. FIG. 12 is a block diagram showing Example 2 of a connection between an optical transmission line and an optical signal measuring device in an optical network system. FIG. 13 is a graph showing an example of pre-acquired data used when acquiring a GSNR value. FIG. 14 is a flowchart showing Example 1 of a specific process for identifying an abnormality location. FIG. 15 is a flowchart showing Example 2 of a specific process for identifying an abnormality location. FIG. 16 is a flowchart showing Example 3 of a specific process for identifying an abnormality location. FIG. 17 is a time chart showing an example of changes in the Q value. FIG. 18 is a block diagram showing the configuration of an optical network system of Variation-5.

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. <Configuration of Optical Network System> An example configuration of an optical network system 100 including a fault range identification system according to an embodiment of the present invention is shown in FIG.

[0021] 5 includes a plurality of independent optical networks 11, 12, and 13. These optical networks 11, 12, and 13 are managed and operated by a plurality of different operating companies A, B, and C, respectively.

[0022] 5, information can be transmitted across multiple optical networks 11, 12, and 13 managed by multiple operating companies A, B, and C. To enable this, an output of optical network 11 and an input of optical network 12 are connected by an inter-network connection unit 16, and an output of optical network 12 and an input of optical network 13 are connected by an inter-network connection unit 17.

[0023] The optical network system 100 is also configured as an all-photonics network. That is, no optical-electrical-optical conversion is performed within each of the optical networks 11, 12, and 13, or in each of the inter-network connecting units 16 and 17. All transmission paths are directly connected while maintaining the optical signal transmission format, enabling information to be transmitted as an optical signal from the source to the destination.

[0024] A source user terminal (not shown) is connected to the transponder 15A. The transponder 15A receives information input from the source user terminal in the form of an electrical signal, generates an optical signal modulated by this electrical signal, and provides the optical signal to the input end of the optical network 11. The optical signal input to the optical network 11 is output from the optical network 11 via the internal optical transmission path 14A, passes through the inter-network connection unit 16 as an optical signal, and is input to the downstream optical network 12.

[0025] The optical signal input to the optical network 12 is output from the optical network 12 via the internal optical transmission path 14B, and is input as an optical signal to the downstream optical network 13 via the inter-network connection unit 17. The optical signal input to the optical network 13 is output from the optical network 13 via the internal optical transmission path 14C and input to the transponder 15F.

[0026] The transponder 15F converts the optical signal output from the optical network 13 into an electrical signal, performs demodulation processing, and provides the received information in the form of an electrical signal to the destination user terminal. Furthermore, the transponder 15F can detect errors that have occurred in the information transmitted via the optical networks 11, 12, and 13 based on the results of the demodulation processing.

[0027] On the other hand, because the output of optical transmission line 14A and the input of optical transmission line 14B are directly connected by optical fiber at inter-network connection unit 16, optical network 11 itself cannot detect information about an error occurring due to a fault on optical transmission line 14A, and cannot pass that error information to optical network 12. Similarly, because the output of optical transmission line 14B and the input of optical transmission line 14C are directly connected by optical fiber at inter-network connection unit 17, optical network 12 itself cannot detect information about an error occurring due to a fault on optical transmission line 14A, and cannot pass that error information to optical network 13.

[0028] The optical network 11 is provided with a control unit 25A for managing the network, the optical network 12 is provided with a control unit 25B for managing the network, and the optical network 13 is provided with a control unit 25C for managing the network.

[0029] 5, optical signal measuring instruments 21A and 22A are connected to the input and output ends, respectively, of optical network 11. Each of optical signal measuring instruments 21A and 22A has the function of measuring the optical signal quality, such as GSNR, of the optical signal at the point where they are connected.

[0030] As in the above, optical signal measuring instruments 21B and 22B are connected to the input and output ends, respectively, of optical network 12. Furthermore, optical signal measuring instruments 21C and 22C are connected to the input and output ends, respectively, of optical network 13.

[0031] In the present invention, either the optical signal measuring device 22A at the output of the optical network 11 or the optical signal measuring device 21B at the input of the optical network 12 can be omitted. Also, either the optical signal measuring device 22B at the output of the optical network 12 or the optical signal measuring device 21C at the input of the optical network 13 can be omitted.

[0032] The host control unit 30 is provided to manage the entire optical network system 100. The host control unit 30 can communicate with the transponder 15F, which is the transmission destination. The host control unit 30 can also communicate with the control units 25A, 25B, and 25C of each optical network.

[0033] <Characteristic Functions> Figure 6 shows characteristic functions included in the optical network system 100 in Figure 5. As shown in Figure 6, the optical network system 100 includes an error information transmission unit 41 and optical signal quality measurement units 42A and 42B. Furthermore, an abnormality identification unit 43 is arranged in each of the control units 25A, 25B, and 25C.

[0034] The error information transmission unit 41 is disposed in, for example, the upper level control unit 30 shown in Fig. 5. The error information transmission unit 41 has a function of transmitting information about an error detected in the transponder 15F at the transmission destination to the control units 25A, 25B, and 25C of each optical network.

[0035] 5, and has a function of acquiring information on the optical signal quality measured at the input of the optical network 11 and notifying the abnormality identifying unit 43. Also, optical signal quality measuring unit 42B is arranged, for example, in optical signal measuring device 22A shown in Fig. 5, and has a function of acquiring information on the optical signal quality measured at the output of the optical network 11 and notifying the abnormality identifying unit 43. Also, functions similar to those of the optical signal quality measuring units 42A and 42B are provided in each of the optical networks 12 and 13.

[0036] 5, and has a function of identifying the presence or absence of an abnormality in the optical network 11 based on the information on the optical signal quality acquired by the optical signal quality measuring units 42A and 42B. Similarly, the control units 25B and 25C also have an abnormality identifying unit 43 arranged therein to identify the presence or absence of an abnormality in each of the optical networks 12 and 13.

[0037] In the optical network system 100, when a failure occurs in the optical transmission line or the like at any point in the optical networks 11, 12, or 13, the transponder 15F at the transmission destination detects the error based on the result of demodulating the electrical signal obtained by converting the received optical signal. The error detected by the transponder 15F is notified to the control units 25A, 25B, and 25C of each optical network via the error information transmission unit 41.

[0038] In this case, in the optical network 11, the abnormality identification unit 43 identifies the presence or absence of an abnormality in the optical network 11 based on the optical signal quality at the input and output of the optical network 11 acquired by the optical signal quality measurement units 42A and 42B. Similarly, the abnormality identification unit 43 can identify the presence or absence of an abnormality in the other optical networks 12 and 13. Therefore, it is possible to identify which of the optical networks 11, 12, or 13 is causing the error detected in the destination transponder 15F.

[0039] <Characteristic Operations> Characteristic operations in the optical network system 100 shown in Figures 5 and 6 are shown in Figure 7. The operations shown in Figure 7 will be described below.

[0040] The error information transmission unit 41 of the upper control unit 30 communicates with the transponder 15F of the transmission destination to grasp the error occurrence status in the transponder 15F (step S11). Then, each control unit 25A, 25B, 25C determines whether or not an error occurrence has been detected (step S12). If an error occurrence in the transponder 15F is detected (Yes), the process proceeds to step S13. If an error occurrence in the transponder 15F is not detected (No), the process of FIG. 7 is completed.

[0041] In step S13, optical signal measuring instruments 21A and 22A each measure the optical signal quality at the input and output of optical network 11. In addition, optical signal quality measuring units 42A and 42B acquire information on the optical signal quality at the input and output of optical network 11 and notify the abnormality identifying unit 43.

[0042] Similarly to the above, optical signal measuring instruments 21B and 22B each measure the optical signal quality at the input and output of optical network 12. Optical signal measuring instruments 21C and 22C each measure the optical signal quality at the input and output of optical network 13. Anomaly identification units 43 of each of optical networks 12 and 13 acquire information on the optical signal quality at the input and output of the optical network.

[0043] The anomaly identifying unit 43 estimates the output optical signal quality from the input optical signal quality measured for each optical network (step S14). The anomaly identifying unit 43 compares the measured and estimated values ​​of the output optical signal quality for each optical network to identify the presence or absence of an anomaly (step S15).

[0044] The host controller 30 acquires the comparison results from the anomaly identification unit 43 of each optical network and identifies the location of the failure (step S16). For example, if the comparison results from the anomaly identification unit 43 are "no anomaly", "anomaly present", and "no anomaly" for the optical networks 11, 12, and 13, respectively, the host controller 30 recognizes that the failure location is within the optical network 12. Then, when step S16 is completed, the processing of FIG. 7 ends.

[0045] <Modification 1> The configuration of an optical network system 100A of Modification 1 is shown in Fig. 8. The configuration of the optical network system 100A of Fig. 8 will be described below.

[0046] The optical network system 100A includes a control unit 51 that manages the optical network 11, a control unit 52 that manages the optical network 12, and a control unit 53 that manages the optical network 13. The control units 51, 52, and 53 of the optical networks have the function of communicating data with each other and the function of the abnormality identification unit 43. The control unit 53 also has a built-in function equivalent to the error information transmission unit 41.

[0047] Therefore, the optical network system 100A shown in Fig. 8 can operate in the same manner as the optical network system 100 shown in Fig. 5 and Fig. 6. That is, when the transponder 15F at the transmission destination detects an error, the error information is notified to the abnormality identification units 43 in each of the control units 51, 52, and 53 via the error information transmission unit 41 in the control unit 53. In addition, since the optical networks 11, 12, and 13 can share the "abnormality" information detected by the abnormality identification units 43 in each of the control units 51, 52, and 53 with each other, the location of the failure in the entire optical network can be easily identified.

[0048] <Modification 2> The configuration of an optical network system 100B of Modification 2 is shown in Fig. 9. The configuration of the optical network system 100B of Fig. 9 will be described below.

[0049] 9, an optical return path 64 is formed along each of the optical transmission lines 14A, 14B, and 14C between the transponder 15F and the input of the optical network 11. The optical return path 64 is a return path for returning an optical signal received by the transponder 15F to the source side at the destination transponder 15F, and is formed of a dedicated optical fiber or an optical fiber common to the optical transmission lines 14A, 14B, and 14C.

[0050] The optical signal sent by the transponder 15F to the optical return path 64 is a newly generated optical signal that is modulated to include error information obtained as a result of demodulating the optical signal received by the transponder 15F.

[0051] Each optical signal measuring device 65A, 66A, 65B, 66B, 65C, 66C connected to the input / output of each optical network 11, 12, 13 receives the optical signal sent back via the optical return path 64, converts it into an electrical signal, and demodulates this electrical signal to grasp the error information transmitted by the transponder 15F.

[0052] The abnormality identification unit 43 in the control unit 61 that manages the optical network 11 acquires error information for the transponder 15F from the optical signal measuring instrument 65A, and identifies whether or not an abnormality exists based on the measured optical signal quality values ​​from the optical signal measuring instruments 65A and 66A.

[0053] Similarly, the abnormality identification unit 43 in the control unit 62 that manages the optical network 12 acquires error information for the transponder 15F from the optical signal measuring instrument 65B, and identifies whether or not an abnormality exists based on the measured optical signal quality values ​​of the optical signal measuring instruments 65B and 66B.

[0054] The abnormality identification unit 43 in the control unit 63 that manages the optical network 13 acquires error information for the transponder 15F from the optical signal measuring instrument 65C, and identifies whether or not an abnormality exists based on the optical signal quality measurements made by the optical signal measuring instruments 65C and 66C.

[0055] <Modification 3> The configuration of an optical network system 100C of Modification 3 is shown in Fig. 10. The configuration of the optical network system 100C of Fig. 10 will be described below.

[0056] In the optical network system 100C of FIG. 10, an optical signal measuring device 21 is connected to each of the boundary positions of a plurality of optical networks 11, 12, and 13, such as the above-mentioned inter-network connecting sections 16 and 17.

[0057] Therefore, also in the optical network system 100C, the abnormality identification unit 43 of the control unit 25A that manages the optical network 11 can acquire measured values ​​of the optical signal quality at the input and output of the optical network 11 from the optical signal measuring instruments 21 that are located on both the input and output sides of the optical network 11. Then, based on these measured values ​​of the optical signal quality, the abnormality identification unit 43 can identify the presence or absence of an abnormality in the optical network 11.

[0058] Similarly, the abnormality identification unit 43 of the control unit 25B that manages the optical network 12 can acquire measurement values ​​of the optical signal quality at the input and output of the optical network 12 from the optical signal measuring instruments 21 that are located on both the input and output sides of the optical network 12. Then, based on these measurement values ​​of the optical signal quality, the abnormality identification unit 43 can identify the presence or absence of an abnormality in the optical network 12.

[0059] The fault identification unit 43 of the control unit 25C that manages the optical network 13 can acquire measurement values ​​of the optical signal quality at the input and output of the optical network 13 from the optical signal measuring instruments 21 that are located on both the input and output sides of the optical network 13. Then, the fault identification unit 43 can identify the presence or absence of a fault in the optical network 13 based on these measurement values ​​of the optical signal quality.

[0060] <Modification 4> The configuration of an optical network system 100D of Modification 4 is shown in Fig. 11. The configuration of the optical network system 100D of Fig. 11 will be described below. In the optical network system 100D of Fig. 11, an optical signal measuring instrument 21 is connected to the input position of each of multiple optical networks 11, 12, and 13.

[0061] Therefore, also in the optical network system 100D, the abnormality identification unit 43 of the control unit 25A that manages the optical network 11 can obtain the measurement value of the optical signal quality at the input of the optical network 11 from the optical signal measuring instrument 21 located on the input side of the optical network 11. Furthermore, the measurement value of the optical signal quality at the output of the optical network 11 can be obtained via the control unit 25B from the optical signal measuring instrument 21 connected to the input side of the downstream optical network 12. Then, based on the measurement value of the optical signal quality at the input and output of the optical network 11, the abnormality identification unit 43 in the control unit 25A can identify the presence or absence of an abnormality in the optical network 11.

[0062] Similarly, the abnormality identification unit 43 of the control unit 25B that manages the optical network 12 can obtain the measured value of the optical signal quality at the input of the optical network 12 from the optical signal measuring instrument 21 present on the input side of the optical network 12. Furthermore, the measured value of the optical signal quality at the output of the optical network 12 can be obtained via the control unit 25C from the optical signal measuring instrument 21 connected to the input side of the downstream optical network 13. Then, based on the measured value of the optical signal quality at the input and output of the optical network 12, the abnormality identification unit 43 in the control unit 25B can identify the presence or absence of an abnormality in the optical network 12.

[0063] The abnormality identification unit 43 of the control unit 25C that manages the optical network 13 can obtain the measurement value of the optical signal quality at the input of the optical network 13 from the optical signal measuring instrument 21 present on the input side of the optical network 13. In addition, the measurement value of the optical signal quality at the output of the optical network 13 can be obtained via the upper level control unit 30 as the measurement value of the optical signal quality detected by the downstream transponder 15F. Then, based on the measurement value of the optical signal quality at the input and output of the optical network 13, the abnormality identification unit 43 in the control unit 25C can identify the presence or absence of an abnormality in the optical network 13.

[0064] <Examples of Connections Between Optical Transmission Lines and Optical Signal Measuring Instruments in an Optical Network System> - <Connection Example 1> Connection Example 1 between an optical transmission line and an optical signal measuring instrument in an optical network system is shown in Fig. 12. In the example shown in Fig. 12, a coupler 71 is connected midway along optical transmission line 14, which connects two transponders 15X and 15Y. In addition, an optical signal measuring instrument 21 is connected to optical fiber 72 of the optical transmission line branched by coupler 71. Therefore, the optical signal quality of the branched optical signal can be measured by optical signal measuring instrument 21 without significantly affecting the transmission of the optical signal passing through optical transmission line 14.

[0065] 5, for example, it is assumed that couplers 71 are disposed at the inlet and outlet of optical transmission line 14A, and that optical signal measuring devices 21A and 22A are connected to these couplers 71 via optical fibers 72. Similarly, it is assumed that couplers 71 are disposed at the inlet and outlet of optical transmission line 14B, and that optical signal measuring devices 21B and 22B are connected to these couplers 71 via optical fibers 72. It is also assumed that couplers 71 are disposed at the inlet and outlet of optical transmission line 14C, and that optical signal measuring devices 21C and 22C are connected to these couplers 71 via optical fibers 72.

[0066] -<Connection Example 2> Connection Example 2 between an optical transmission line and an optical signal measuring instrument in an optical network system is shown in Fig. 13. In the example shown in Fig. 13, an all-optical wavelength converter 73 is connected midway along the optical transmission line 14 connecting two transponders 15X and 15Y. Based on the input optical signal, the all-optical wavelength converter 73 can separate and output both the wavelength-converted optical signal and the original wavelength light having the same wavelength as before the wavelength conversion.

[0067] Of the optical signals of the two wavelengths separated by the all-optical wavelength converter 73, the optical component used for transmission is input to the transponder 15Y via the downstream optical transmission path 14. Furthermore, of the optical signals of the two wavelengths separated by the all-optical wavelength converter 73, the optical component not used for transmission is input to the optical signal measuring instrument 21 via an optical fiber 74 that is separate from the one used for transmission.

[0068] Therefore, the optical signal quality can be measured by optical signal measuring instrument 21 using the optical signal output from all-optical wavelength converter 73 without significantly affecting the transmission of the optical signal passing through optical transmission line 14 .

[0069] 5, for example, it is assumed that all-optical wavelength converters 73 are disposed at the inlet and outlet of optical transmission line 14A, and that optical signal measuring devices 21A and 22A are connected to these all-optical wavelength converters 73 via optical fibers 74. Similarly, it is assumed that all-optical wavelength converters 73 are disposed at the inlet and outlet of optical transmission line 14B, and that optical signal measuring devices 21B and 22B are connected to these all-optical wavelength converters 73 via optical fibers 74. It is also assumed that all-optical wavelength converters 73 are disposed at the inlet and outlet of optical transmission line 14C, and that optical signal measuring devices 21C and 22C are connected to these all-optical wavelength converters 73 via optical fibers 74.

[0070] <Specific Example of Acquired Optical Signal Quality> With regard to the optical signal quality used by the optical network system 100, it is necessary to know the change in signal quality at each transit point on the optical transmission path. Therefore, it is necessary to use a parameter that can grasp the signal quality in more detail than the error count obtained after demodulating the optical signal. Therefore, for example, each of the optical signal measuring instruments 21A, 22A, 21B, 22B, 21C, and 22C shown in Fig. 5 is configured to acquire at least one of the PreFEC-BER, Q factor, and GSNR as the optical signal quality.

[0071] PreFEC-BER is the bit error rate before error correction, and FEC stands for Forward Error Correction. PreFEC-BER can be measured using existing optical signal measuring equipment.

[0072] For example, the amplitude of "1" and "0" in a binary signal varies due to noise, etc. The Q (Quality Factor) value can be defined from the difference between the magnitude of this spread (standard deviation) and the average amplitude.

[0073] The Q value of the optical signal quality can be obtained by conversion from the PreFEC-BER error rate (BER) based on the following equation (1).

[0074] The GSNR value of the optical signal quality can be calculated from the Q-factor using, for example, pre-acquired data 81 shown in Fig. 14. The pre-acquired data 81 shown in Fig. 14 is data representing an OSNR (Optical Signal to Noise Ratio) vs. Q-factor characteristic 82 obtained by actual measurement in advance on the optical transmission path of the optical network system 100. When the pre-acquired data 81 in Fig. 14 is used, if the measured Q-factor is 20.3 [dB], a GSNR value of 21.2 [dB] is obtained based on the OSNR vs. Q-factor characteristic 82.

[0075] <Specific Processing for Identifying the Location of an Anomaly on an Optical Network> -<Processing Example 1> A specific processing example 1 for identifying the location of an anomaly is shown in Fig. 15. The processing shown in Fig. 15 corresponds to the detailed contents of steps S13 to S15 in Fig. 7. The processing shown in Fig. 15 will be described below.

[0076] 6 acquires a measurement value Din of the optical signal quality at the input to the optical network 11 from the optical signal quality measurement unit 42A (step S21). The abnormality identification unit 43 acquires an estimate value D1 of the optical signal quality at the output of the optical network 11 based on the measurement value Din of the optical signal quality acquired in step S21 and the transmission route of the optical signal from the input to the output of the optical network 11 (step S22). For example, by providing the measurement value Din and information on the transmission route as input to a tool using the technology disclosed in Non-Patent Document 1, the estimate value D1 of the optical signal quality representing the GSNR can be acquired.

[0077] Next, the anomaly identifying unit 43 acquires a measurement value D2 of the optical signal quality at the output of the optical network 11 from the optical signal quality measuring unit 42B (step S23). The anomaly identifying unit 43 compares the difference (D1-D2) between the estimated value D1 and the measurement value D2 with a threshold value (step S24). The anomaly identifying unit 43 then determines whether the deterioration of the optical signal quality is significant based on the result of comparing the difference (D1-D2) with the threshold value (step S25). If the deterioration of the optical signal quality is significant (Yes), the anomaly identifying unit 43 detects an "abnormality" in the optical network 11 (step S26), and the process of FIG. 7 ends. If the deterioration of the optical signal quality is small (No), the process of FIG. 7 ends.

[0078] The same operation as above is performed in the anomaly identifying units 43 of the other optical networks 12 and 13. Therefore, it is possible to identify in which of the optical networks 11 to 13 an anomaly has occurred.

[0079] <Processing Example 2> A specific processing example 2 for identifying the location of an abnormality is shown in Figure 16. The processing shown in Figure 16 is described below. When normal connectivity is confirmed before the actual start of communication services in the optical network system 100, the optical signal quality measurement unit 42B of each optical network 11 to 13 executes step S31. The optical signal quality measurement unit 42B of each optical network 11 to 13 actually measures the optical signal quality, for example the Q factor, at the output of each optical network 11 to 13, and registers and stores this as a normal optical signal quality value D20 for each optical network (step S31).

[0080] The destination transponder 15F detects the occurrence of an error (step S32) and determines whether or not an error exists (step S33). If the destination transponder 15F detects the occurrence of an error in step S33 (Yes), the process proceeds to step S34. In step S34, the optical signal quality measurement unit 42B of each optical network 11-13 actually measures the optical signal quality, for example, the Q factor, at the output of each optical network 11-13, and sets this as the current optical signal quality measurement value D2.

[0081] The anomaly identifying unit 43 compares the difference (D20 - D2) between the normal value D20 and the measured value D2 with a threshold value (step S35). Then, based on the result of comparing the difference (D20 - D2) with the threshold value, the anomaly identifying unit 43 determines whether the deterioration of the optical signal quality is significant (step S36). If the deterioration of the optical signal quality at the output of the optical network 11 is significant (Yes), the anomaly identifying unit 43 detects an "abnormality" in the optical network 11 (step S37). If the deterioration of the optical signal quality at the output of the optical network 12 is significant (Yes), the anomaly identifying unit 43 detects an "abnormality" in the optical network 12 (step S37). If the deterioration of the optical signal quality at the output of the optical network 13 is significant (Yes), the anomaly identifying unit 43 detects an "abnormality" in the optical network 13 (step S37). Therefore, it is possible to identify which of the multiple optical networks 11 to 13 has experienced a failure.

[0082] -<Processing Example 3> A specific processing example 3 for grasping the location of an abnormality is shown in Fig. 17. The processing shown in Fig. 17 will be described below.

[0083] The optical signal quality measurement unit 42B of each of the optical networks 11 to 13 constantly and repeatedly acquires the latest optical signal quality measurement value (e.g., Q factor) D1 at the output of each of the optical networks 11 to 13 (step S41). Then, the optical signal quality measurement unit 42B determines whether or not an error has been detected (step S42).

[0084] If the destination transponder 15F does not detect an error (No), the process proceeds to step S43, where the optical signal quality measuring unit 42B holds the latest measurement value D1 as the normal optical signal quality Dref.

[0085] On the other hand, if the destination transponder 15F detects an error (Yes), the process proceeds to step S44. Then, the anomaly identification unit 43 of each optical network 11 to 13 compares the change in the measurement value between when the transponder 15F does not detect an error and when it detects an error, i.e., the difference between the latest measurement value D1 and the normal optical signal quality Dref, with a threshold value (step S44).

[0086] As a result of the comparison in step S44, the anomaly identifying unit 43 determines whether the deterioration of the optical signal quality is significant (step S45). If the deterioration of the optical signal quality is significant (Yes), the process proceeds to step S46, where the anomaly identifying unit 43 detects an "anomaly" in the corresponding optical network. If the deterioration of the optical signal quality is small (No), the process of FIG. 17 ends.

[0087] An example of changes in the Q-factor, which represents optical signal quality, is shown in Fig. 18. As shown in Fig. 18, it is generally assumed that the Q-factor of optical signal quality drops sharply at error occurrence time t0. Therefore, in the process shown in Fig. 17, immediately after error occurrence time t0, the transponder 15F detects the occurrence of an error, the process proceeds from step S42 to S44, and because the fluctuation in the measurement value (D1 - Dref) is large, the anomaly identification unit 43 detects "the presence of an anomaly" in step S46.

[0088] <Modification 5> The configuration of an optical network system 100E of Modification 5 is shown in Figure 19. The optical network system 100E of Figure 19 assumes a situation in which multiple optical networks 11A, 12A, and 13A managed by a common operator are connected to one another. In this case, since the multiple optical networks 11A, 12A, and 13A are managed by the same operator, the multiple optical networks 11A to 13A can all be managed by a single control unit 91. This control unit 91 has the functions of the error information transmission unit 41 and the anomaly identification unit 43 for each optical network shown in Figure 6.

[0089] 19, the optical signal measuring instrument 21 is connected to the inputs of the optical networks 11A, 12A, and 13A and to the output of the optical network 13A. Therefore, when an error occurs in the transponder 15F at the transmission destination, the control unit 91 can identify at which point in the optical networks 11A to 13A the failure has occurred.

[0090] <Features of Optical Network System> The following items [1] to [8] are characteristic features of the optical network fault range identification system and fault range identification method of the present invention.

[0091] [1] A fault range identification system for diagnosing an optical network system in which a plurality of optical networks (11-13), each transmitting information in the form of an optical signal, are connected to one another and signals are handed over at connection points (inter-network connection units 16, 17) between the plurality of optical networks while maintaining the form of the optical signals, the system comprising: an error information transmission unit (41) that transmits information on errors detected at the transmission destination to each of the plurality of optical networks; optical signal quality measurement units (42A, 42B) that measure optical signal quality at the input point of each of the plurality of optical networks or at the boundary point of the plurality of optical networks; and an abnormality identification unit (43) that identifies the presence or absence of an abnormality for each optical network based on a first optical signal quality measured at the input and a second optical signal quality measured or estimated at the output for each of the plurality of optical networks.

[0092] According to the optical network fault range identification system having the configuration described above in [1], the presence or absence of an abnormality can be identified for each of the plurality of optical networks, so that the location where the fault has occurred can be easily identified.

[0093] [2] The anomaly identification unit (43) obtains the optical signal quality of the output of each optical network estimated based on the transmission route from the input to the output of the optical network and the first optical signal quality (measured value Din) as the second optical signal quality (estimated value D1) (step S22), and identifies the presence or absence of an anomaly for each optical network based on the difference between the second optical signal quality and the measured value (D2) of the optical signal quality detected at the same location (steps S24, S25), a system for identifying the fault range of an optical network described in [1] above.

[0094] According to the optical network fault range detection system having the configuration described in [2] above, even in a situation where the transmission route from the input to the output of each optical network fluctuates, the correct optical signal quality estimated based on the latest transmission route can be acquired as the second optical signal quality each time. Therefore, the presence or absence of an abnormality can be easily identified without having to previously store a large amount of data representing the optical signal quality under normal conditions.

[0095] [3] The anomaly identification unit (43) measures the optical signal quality at the output of each optical network when connectivity is confirmed normally in advance and stores it as a normal value (step S31), obtains the latest measurement value of the optical signal quality at the output of each optical network after an error is detected at the transmission destination (step S34), and identifies the presence or absence of an anomaly for each optical network based on the difference between the measurement value and the normal value (steps S35, S36), a system for identifying the fault scope of an optical network described in [1] above.

[0096] According to the optical network fault range identification system configured as described above in [3], the latest measurement value of optical signal quality is compared with a normal value stored in advance, so that the presence or absence of an abnormality can be easily identified for each optical network.

[0097] [4] The anomaly identification unit (43) constantly repeats measurements of the optical signal quality at the output of each optical network (step S41), monitors fluctuations in the measured values ​​of the optical signal quality (step S44), and, when it detects a significant decrease in the measured values ​​of the optical signal quality, detects the presence of an anomaly in the corresponding optical network (steps S45, S46), in the optical network fault range identification system described in [1] above.

[0098] According to the optical network fault range identification system having the configuration described above in [4], the change in the measured optical signal quality over time is monitored, so that in the event of a sudden deterioration in optical signal quality due to a fault, it is possible to easily identify whether or not a fault has occurred for each optical network.

[0099] [5] The optical network fault range identification system described in [1] above, wherein the anomaly identification unit (43) acquires and stores characteristic data (pre-acquired data 81) representing the correspondence between the OSNR value and Q value of the optical signal quality in advance, and calculates the GSNR value of the optical signal quality using the characteristic data based on the Q value of the optical signal quality measured by the optical signal quality measurement unit.

[0100] According to the optical network fault range identification system configured as described above in [5], the presence or absence of an abnormality can be easily identified for each optical network based on the GSNR value of the optical signal quality converted from the measured value.

[0101] [6] The optical network fault range identification system described in [1] above, wherein each of the optical signal quality measurement units (42A, 42B) measures the quality of the extracted optical signal using a coupler (71) or an all-optical wavelength converter (73) arranged midway along the optical transmission path through which the transmitted optical signal passes.

[0102] According to the optical network fault range identification system having the configuration described above in [6], the quality of an optical signal can be easily measured midway along the optical transmission path without causing a significant effect such as attenuation on the transmitted optical signal.

[0103] [7] The optical transmission paths of the plurality of optical networks have an optical return path (64) that returns the optical signal that has reached the information transmission destination to the opposite side and delivers it to the position of each of the optical signal quality measurement units (42A, 42B). [8] The optical network fault range determination system described in [1] above.

[0104] According to the optical network fault range identification system having the configuration described above in [7], the control unit of each optical network can grasp errors that have occurred at other locations on the network without the need for special data communication lines connecting the control units of the multiple optical networks.

[0105] [8] A fault range identification method for diagnosing an optical network system in which a plurality of optical networks, each transmitting information in the form of an optical signal, are connected to each other and signals are passed between the connection points between the plurality of optical networks while maintaining the form of the optical signal, the method comprising: transmitting information of an error detected at a transmission destination to each of the plurality of optical networks; measuring optical signal quality at an input point of each of the plurality of optical networks or at a boundary point of the plurality of optical networks; when an error is detected at the transmission destination, obtaining a first optical signal quality measured at the input for each of the plurality of optical networks and a second optical signal quality measured or estimated at the output; and identifying the presence or absence of an abnormality in each optical network based on the first optical signal quality and the second optical signal quality.

[0106] According to the method for identifying the fault range in an optical network in [8] above, the presence or absence of an abnormality can be identified for each of the plurality of optical networks, so that the location where the fault has occurred can be easily identified.

[0107] 10A, 10B Optical network system 11, 12, 13 Optical network 14, 14A, 14B, 14C Optical transmission path 15A, 15B, 15C, 15D, 15E, 15F Transponder 15X, 15Y Transponder 16, 17 Inter-network connection unit 18 Fault location 21, 21A, 21B, 21C Optical signal measuring instrument 22A, 22B, 22C Optical signal measuring instrument 25A, 25B, 25C Control unit 30 Upper control unit 41 Error information transmission unit 42A, 42B Optical signal quality measuring unit 43 Abnormality identification unit 51, 52, 53 Control unit 62, 62, 63 Control unit 64 Optical loop-back path 65A, 65B, 65C Optical signal measuring instrument 66A, 66B, 66C Optical signal measuring instrument 71: Coupler 72, 74: Optical fiber 73: All-optical wavelength converter (AO-WC) 81: Pre-acquired data 82: OSNR vs. Q-factor characteristic 91: Control unit 100, 100A, 100B, 100C, 100D: Optical network system

Claims

1. A fault scoping system for diagnosing an optical network system in which multiple optical networks, each transmitting information in the form of an optical signal, are connected to one another and signals are handed over at connection points between the multiple optical networks while maintaining the optical signal form, the system comprising: an error information transmission unit that transmits information on errors detected at the transmission destination to each of the multiple optical networks; an optical signal quality measurement unit that measures optical signal quality at the input point of each of the multiple optical networks or at the boundary point of the multiple optical networks; and an abnormality identification unit that identifies the presence or absence of an abnormality for each optical network based on a first optical signal quality measured at the input and a second optical signal quality measured or estimated at the output for each of the multiple optical networks.

2. The optical network fault range identification system according to claim 1, wherein the anomaly identification unit acquires as the second optical signal quality the optical signal quality of the output of each optical network estimated based on the transmission route from the input to the output of that optical network and the first optical signal quality, and identifies the presence or absence of an anomaly for each optical network based on the difference between the second optical signal quality and a measured value of the optical signal quality detected at the same location.

3. The optical network fault range identification system according to claim 1, wherein the anomaly identification unit measures in advance the optical signal quality at the output of each optical network when communication is confirmed to be normal and stores it as a normal value, and after an error is detected at the transmission destination, obtains the latest measured value of the optical signal quality at the output of each optical network, and identifies the presence or absence of an anomaly for each optical network based on the difference between the measured value and the normal value.

4. The optical network fault range identification system described in claim 1, wherein the anomaly identification unit constantly repeats measurements of the optical signal quality at the output of each optical network, monitors fluctuations in the measured values ​​of the optical signal quality, and when it detects a significant drop in the measured values ​​of the optical signal quality, detects the presence of an anomaly in the corresponding optical network.

5. The optical network fault range identification system according to claim 1, wherein the anomaly identification unit acquires and stores characteristic data in advance that indicates the correspondence between the OSNR value and Q value of the optical signal quality, and calculates the GSNR value of the optical signal quality using the characteristic data based on the Q value of the optical signal quality measured by the optical signal quality measurement unit.

6. The optical network fault range identification system according to claim 1, wherein each of the optical signal quality measurement units measures the quality of an optical signal extracted using a coupler or an all-optical wavelength converter placed along the optical transmission path through which the transmitted optical signal passes.

7. The optical network fault range determination system according to claim 1, wherein the optical transmission paths of the plurality of optical networks have optical return paths that return optical signals that arrive at the information transmission destination in the opposite direction and deliver them to the position of each of the optical signal quality measurement units.

8. A fault range identification method for diagnosing an optical network system in which multiple optical networks, each transmitting information in the form of an optical signal, are connected to each other and signals are passed between the multiple optical networks while maintaining the optical signal form at connection points between the multiple optical networks, the method comprising: transmitting information of an error detected at the transmission destination to each of the multiple optical networks; measuring optical signal quality at the input point of each of the multiple optical networks or at the boundary point of each of the multiple optical networks; when an error is detected at the transmission destination, obtaining a first optical signal quality measured at the input for each of the multiple optical networks and a second optical signal quality measured or estimated at the output, and identifying the presence or absence of an abnormality in each optical network based on the first optical signal quality and the second optical signal quality.

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