Optical communication network management device and communication device

Abstract

To provide a technique for determining the path of signal light in an optical communication network.SOLUTION: In an optical communication network, a management device 1 includes: holding means for holding path information indicating group delay given to signal light received by a second communication device for each of paths of the signal light from a first communication device (optical node 3) to the second communication device (other optical node 3); acquisition means for acquiring, from the second communication device, group delay information indicating the group delay given to the signal light received by the second communication device; and determination means for determining a path of the signal light based on the group delay indicated by the group delay information and the path information.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for determining a path of signal light in an optical communication network. [Background technology]

[0002] FIG. 1 shows an example of an optical communication network. The terminal devices 5-1 and 5-2 are optical communication devices that transmit and receive signal light to transmit and receive predetermined data. The optical node 3 is an optical communication device that relays the signal light transmitted and received between the terminal devices 5-1 and 5-2. The optical node 3 is, for example, an optical cross connect (OXC) or an optical add-drop multiplexer (OADM), and is configured to be able to set an interface that outputs an input signal light of a predetermined wavelength. In the following description, when distinguishing between the four optical nodes 3, they are represented as optical nodes #1 to #4. In FIG. 1, the optical node #1 and the optical node #2 are connected by an optical link 12, the optical node #2 and the optical node #4 are connected by an optical link 24, the optical node #1 and the optical node #3 are connected by an optical link 13, and the optical node #3 and the optical node #4 are connected by an optical link 34. Further, in Fig. 1, the terminal device 5-1 is connected to the optical node #1 by an optical link, and the terminal device 5-2 is connected to the optical node #4 by an optical link. Each optical link may include one or more optical amplifiers. Fig. 1 also shows the interfaces (IFs) of the optical node 3 to which each optical link is connected. For example, the optical link 12 is connected to the IF #3 of the optical node #1 and the IF #1 of the optical node #2.

[0003] In the configuration of Fig. 1, there are two paths for the signal light from the terminal device 5-1 to the terminal device 5-2: a path via optical node #2 and a path via optical node #3. When using the path via optical node #2, the optical node #1 is set to output the signal light from the terminal device 5-1 to IF #3, and when using the path via optical node #3, the optical node #1 is set to output the signal light from the terminal device 5-1 to IF #4. This setting is input from a management device (not shown).

[0004] Patent Document 1 discloses a configuration in which, when a fault occurs in an optical link, the path of the signal light accommodated in the failed optical link is switched by changing the settings of an optical node. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3972664 Summary of the Invention [Problem to be solved by the invention]

[0006] The switching of the path of the signal light by the optical node 3 is also used when the optical link is disconnected in a planned manner for maintenance reasons. For example, in the configuration of FIG. 1, it is assumed that the path via the optical node 2 is used as the path of the signal light of a predetermined wavelength from the terminal device 5-1 to the terminal device 5-2 (hereinafter, the signal light of a predetermined wavelength from the terminal device 5-1 to the terminal device 5-2 is referred to as the first signal light). In this case, when it becomes necessary to disconnect the optical link 24 for a predetermined period of time for maintenance work, the maintenance person of the optical communication network transmits a control signal to each of the optical nodes #1, #3, and #4 via the management device in order to switch the path of the first signal light to the path via the optical node #3. The control signal to the optical node #1 includes a command for setting the output destination of the first signal light input to IF#1 to IF#4. The control signal to the optical node #3 includes a command for setting the output destination of the first signal light input to IF#2 to IF#3. The control signal to the optical node #4 includes a command for setting the output destination of the first signal light input to IF #1 to IF #3.

[0007] However, if the control signal does not reach the optical nodes #1, #3, and #4 for some reason, the path of the first signal light may not be switched and may remain the same. In this case, if a maintenance person who recognizes that the optical link 24 does not accommodate the first signal light due to the previous path switching disconnects the optical link 24, an unexpected failure may occur.

[0008] The present invention provides a technique for determining the path of signal light in an optical communication network. [Means for solving the problem]

[0009] According to one aspect of the present invention, a management device for an optical communication network is characterized in that it comprises: a holding means for holding, for each path of signal light from a first communication device to a second communication device, route information indicating a group delay imparted to the signal light received by the second communication device; an acquisition means for acquiring from the second communication device group delay information indicating the group delay imparted to the signal light received by the second communication device; and a determination means for determining the path of the signal light based on the group delay indicated by the group delay information and the route information. Effect of the Invention

[0010] According to the present invention, it is possible to determine the path of signal light in an optical communication network. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an optical communication network. [Diagram 2] FIG. 1 is a configuration diagram of an optical communication network according to an embodiment. [Diagram 3] 1A and 1B are diagrams showing examples of group delays imparted by a group delay filter and group delays imparted to signal light. [Figure 4] FIG. 2 is a configuration diagram of a terminal device according to an embodiment. [Diagram 5] 4A and 4B are explanatory diagrams of a method for determining a group delay given to a signal light according to an embodiment. [Figure 6]FIG. 2 is a configuration diagram of a terminal device according to an embodiment. [Figure 7] FIG. 2 is a configuration diagram of a management device according to an embodiment. [Figure 8] FIG. 2 is a configuration diagram of an optical node according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. In addition, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0013] First Embodiment FIG. 2 is a configuration diagram of an optical communication network according to this embodiment. The same components as those described in FIG. 1 are given the same reference symbols and their description will be omitted. In this embodiment, a group delay filter is provided in each interface of each optical node 3. In FIG. 1, a group delay filter NM is provided in IF#M (M is an integer from 1 to 4) of optical node #N (N is an integer from 1 to 4). In addition, a management device 100 controls the terminal devices 5-1 and 5-2 and each optical node 3. In FIG. 2, for the sake of simplicity, only the signal lines for the management device 100 and the terminal device 5-2 to transmit and receive control signals are shown by dotted lines, but the management device 100 is configured to be able to transmit and receive control signals to and from the terminal devices 5-1 and 5-2 and each optical node 3.

[0014] A group delay filter is a filter that imparts a group delay to the signal light passing through it. When the signal light passes through multiple group delay filters, the group delay imparted to the signal light is the sum of the group delays imparted by each group delay filter through which the signal light passes. For example, the first group delay filter imparts group delay 60 shown in Fig. 3(A), and the second group delay filter imparts group delay 61 shown in Fig. 3(B). In this case, the signal light that has passed through both the first and second group delay filters is imparted with group delay 62 shown in Fig. 3(C).

[0015] In this embodiment, the group delay that each group delay filter NM imparts to the signal light is determined so that the total group delay imparted to the signal light from the transmitting terminal device to the receiving terminal device differs for each possible route of the signal light. For example, in the configuration shown in Fig. 2, the possible routes of the first signal light from the terminal device 5-1 to the terminal device 5-2 are the first route via the optical node 2 and the second route via the optical node 3. Therefore, the group delay that each group delay filter NM imparts to the signal light passing therethrough is determined so that the group delay imparted to the first signal light received by the terminal device 5-2 when the first signal light passes through the first route differs from the group delay imparted to the first signal light received by the terminal device 5-2 when the first signal light passes through the second route. The same applies to the other signal lights.

[0016] In addition to the group delay filter, a group delay specific to the path is given to the signal light. The group delay specific to the path is given to the signal light when the signal light passes through components such as an optical link or an optical switch in an optical node. Therefore, when the first signal light passes through the first path, the first signal light is given a group delay due to the group delay filters 1-1, 1-3, 2-1, 2-4, 4-2, and 4-3 in addition to the group delay specific to the first path that is given when no group delay filter is provided.

[0017] In this embodiment, the group delay given to the signal light is determined for each possible route of the signal light, and route information indicating the relationship between the route and the group delay given to the signal light for each route is stored in the management device 100. The group delay for each route can be obtained, for example, by actually performing measurements before the start of the service. Alternatively, it can be determined by calculation based on the optical parameters of the optical links and optical nodes and the characteristics of the group delay filters.

[0018] 4 is a configuration diagram of the receiving side of the terminal device 5 according to this embodiment. The terminal device 5 is a general term for the terminal devices 5-1 and 5-2 in FIG. 2. The receiving unit 51 receives the signal light, for example, coherently, and outputs an analog electrical signal to an analog-to-digital (AD) conversion unit 52. The AD conversion unit 52 converts the analog electrical signal into digital data and outputs it to a compensation demodulation unit 53.

[0019] The compensation demodulation unit 53 has a processor, performs various compensation processes on the digital data, and performs demodulation based on the compensated data. Here, the compensation process usually includes a process of compensating for the group delay given to the signal light. In other words, the terminal device 5 determines the group delay given to the signal light in order to demodulate the signal light. In response to a request from the management device 100, the compensation demodulation unit 53 transmits group delay information indicating the group delay given to the signal light, which is determined in order to compensate for the group delay, to the management device 100. Alternatively, the compensation demodulation unit 53 transmits the group delay information to the management device 100 at predetermined intervals or each time a predetermined condition is satisfied, such as when the signal light is disconnected and then the signal light is detected again.

[0020] The management device 100 can determine the path of the signal light received by the terminal device 5 based on the path information. For example, the management device 100 can determine the error between the group delay given to the first signal light indicated by the group delay information received from the terminal device 5-2 and the group delay of each possible path of the first signal light indicated by the path information, and can determine that the path corresponding to the group delay with the smallest error from the group delay given to the first signal light is the path of the first signal light among the possible paths of the first signal light. The error can be a least square error. That is, for example, the group delay as shown in FIG. 3 can be regarded as a waveform, and the error can be a value obtained by integrating the square of the delay time difference at the same frequency of the two group delays in the frequency domain. Therefore, for example, when the management device 100 transmits a control signal for switching the first signal light from the first path to the second path to each optical node 3, it can determine whether the path of the first signal light has switched from the first path to the second path based on the group delay given to the first signal light received from the terminal device 5-2.

[0021] It should be noted that Fourier analysis can be used to determine the path. For example, while FIG. 3(C) actually shows the relationship between frequency and delay amount, the waveform shown in FIG. 3(C) is treated as a waveform on the time axis and a Fourier transform is performed. By the Fourier transform, as shown in FIG. 5, a signal component corresponding to group delay 60 shown in FIG. 3(A) and a signal component corresponding to group delay 61 shown in FIG. 3(B) are obtained. The path can be determined by comparing the signal components after the Fourier transform. It should be noted that in this case, the path information can indicate, for example, the relationship between the signal components after the Fourier transform and the path.

[0022] Any group delay filter can be used. For example, a ring resonator filter, a multilayer thin film filter, a multistage Mach-Zehnder interferometer type optical waveguide filter, etc. can be used as the group delay filter. When using a ring resonator filter, it is possible to give the signal light a group delay that varies sinusoidally on the frequency axis as shown in Figures 3(A) and 3(B) by adjusting the resonator length of the ring resonator and the coupling amount between the ring resonator and the input / output waveguide. A group delay with such characteristics is advantageous when using the above-mentioned Fourier analysis.

[0023] Also, instead of providing the group delay filter in the interface of the optical node, it is possible to provide it in the optical switch section of the optical node. The optical switch section has a port corresponding to the interface of the optical node. For example, some optical switch sections use liquid crystal on silicon (LCoS) devices that control the phase characteristics of optical signals. In such optical switch sections, it is possible to give different phase delays to each frequency of the signal light, and therefore it is possible to make it function as a group delay filter.

[0024] As described above, according to this embodiment, the path of the signal light is determined based on the group delay given to the signal light. Note that, in this embodiment, the management device 100 determines the path of the signal light based on the path information and the group delay information, but the path information may be stored in the terminal device 5, and the terminal device 5 may determine the path.

[0025] Second Embodiment Next, the second embodiment will be described, focusing on the differences from the first embodiment. In this embodiment, as shown in Fig. 6, a filter unit 54 that imparts a group delay to the signal light is provided upstream of a receiving unit 51 of the terminal device. The filter unit 54 uses a device that can dynamically configure the group delay to be imparted to the signal light, such as the above-mentioned liquid crystal on silicon (LCoS) device. The management device 100 controls the group delay that the filter unit 54 imparts to the signal light by transmitting a control signal to the terminal device 5.

[0026] The management device 100 controls the group delay given to the signal light by the filter unit 54 so as to cancel out the group delay given to the signal light. Specifically, similar to the first embodiment, the group delay given to the signal light is obtained in advance for each possible route for the signal light. Then, information indicating the group delay given to the signal light for each possible route for the signal light is stored in the management device 100 as compensation information so as to cancel out the group delay given to the signal light. Note that the compensation information in this embodiment is substantially the same as the route information in the first embodiment.

[0027] For example, when the first signal light passes through the first path, the management device 100 configures the filter unit 54 of the terminal device 5-2 so that the filter unit 54 of the terminal device 5-2 imparts to the signal light a group delay associated with the first path in the compensation information. Furthermore, when normal demodulation is not possible, the compensation demodulation unit 53 notifies the management device 100 of an alarm. For example, data carried by the signal light is usually protected by an error correction code or an error detection code. The compensation demodulation unit 53 detects the frequency of error occurrence using the error correction code or the error detection code, and can determine whether or not demodulation is normal by comparing it with a threshold value.

[0028] For example, when the first signal light passes through the first path and the filter unit 54 of the terminal device 5-2 cancels the group delay given to the first signal light, the group delay detected by the compensation demodulation unit 53 has a substantially flat characteristic. Moreover, the compensation demodulation unit 53 can normally demodulate the first signal light and does not issue an alarm.

[0029] When the management device 100 switches the path of the first signal light from the first path to the second path, it transmits a first control signal for path switching to each optical node 3 and transmits a second control signal to the terminal device 5-2 so that the filter unit 54 of the terminal device 5-2 gives the first signal light a group delay associated with the second path in the compensation information. If the path of the first signal light does not switch from the first path to the second path, the filter unit 54 cannot compensate for the group delay given to the first signal light. In this case, the group delay detected by the compensation demodulation unit 53 fluctuates significantly from the approximately flat characteristic, and the compensation demodulation unit 53 issues an alarm until the compensation demodulation unit 53 compensates for the group delay in response to this large fluctuation. On the other hand, when the path of the first signal light switches from the first path to the second path, the group delay detected by the compensation demodulation unit 53 becomes approximately flat. Even in this case, the compensation demodulation unit 53 may issue an alarm momentarily, but the period during which the alarm is issued is much shorter than when the path of the first signal light does not switch from the first path to the second path. Therefore, the management device 100 can determine whether the path has been switched normally or not based on the state of the terminal device 5-2 after transmitting the first control signal and the second control signal, for example, the duration of the alarm.

[0030] In this embodiment, even when the path of the signal light is switched due to a fault in the optical link, the management device 100 configures the filter unit 54 of the terminal device 5 so as to cancel the group delay imparted to the signal light after the path is switched.

[0031] FIG. 7 is a configuration diagram of the management device 100 according to this embodiment. The holding unit 10 holds the route information in the first embodiment, and holds the compensation information in the second embodiment. The communication unit 14 transmits and receives control signals to and from each terminal device 5 and each optical node 3, and receives alarms from each terminal device 5 and each optical node 3. The acquisition unit 11 is provided in the first embodiment, and acquires group delay information indicating the group delay given to the signal light received by the terminal device 5 from the terminal device 5 via the communication unit 14. The determination unit 12 is provided in the first embodiment, and determines the route of each signal light based on the group delay given to each signal light indicated by the group delay information acquired from each terminal device 5 and the route information. The control unit 13 transmits a control signal to each optical node 3 via the communication unit 14 when setting and switching the route of each signal light. In the second embodiment, when the control unit 13 transmits a control signal to each optical node 3 to set up and switch the path of the signal light, the control unit 13 transmits a control signal to the terminal device 5 receiving the signal light, based on the compensation information, for configuring the filter unit 54 of the terminal device 5 to compensate for the group delay imparted to the signal light.

[0032] FIG. 8 is a configuration diagram of an optical node 3 according to the first embodiment. The optical node 3 includes an interface unit 31 and an optical switch unit 32. The interface unit 31 includes a plurality of interfaces for connecting to a plurality of optical links. The plurality of interfaces are connected to corresponding ports of the optical switch unit 32. The optical switch unit 32 has a so-called wavelength switch function, and outputs a plurality of wavelength-multiplexed signal lights input via each interface (each port) from another interface (port). The interface (port) that outputs the input signal light is configured to be changeable based on a control signal from the management device 100. Each interface is configured to be able to individually implement any one of group delay filters with various characteristics. It is also possible to configure the group delay filter to be provided in the optical port corresponding to each optical interface of the optical switch unit 32, rather than in the interface.

[0033] The management device 100 according to the present invention can be realized by a program that, when executed by one or more processors of a computer, causes the computer to operate as the above-mentioned management device 100. These programs can be stored in a device-readable storage medium or distributed via a network.

[0034] The above configuration makes it possible to determine the current path of each optical signal in an optical communication network, which will contribute to Goal 9 of the United Nations Sustainable Development Goals (SDGs) to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0035] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention. [Explanation of symbols]

[0036] 10: Holding section, 11: Acquisition section, 12: Judgment section

Claims

1. A management device for an optical communication network, a storage means for storing path information indicating a group delay applied to the signal light received by the second communication device for each path of the signal light from the first communication device to the second communication device; an acquisition unit for acquiring, from the second communication device, group delay information indicating a group delay imparted to the signal light received by the second communication device; a determination unit that determines a path of the signal light based on the group delay indicated by the group delay information and the path information; A management device comprising:

2. The management device further comprises: a control unit configured to transmit a control signal to a device of the optical communication network to set a path of the signal light from the first communication device to the second communication device as a first path; The management device described in claim 1, characterized in that the determination means determines whether the path of the signal light is the first path based on the group delay information and the route information obtained from the second communication device after the control means transmits the control signal.

3. A management device for an optical communication network, a storage unit for storing compensation information for compensating for a group delay imparted to the signal light received by the second communication device for each path of the signal light from the first communication device to the second communication device; a control means for transmitting a first control signal to a device of the optical communication network for setting the path of the signal light from the first communication device to the second communication device as a first path, and for transmitting a second control signal to the second communication device for configuring a group delay filter provided in the second communication device so as to compensate for a group delay given to the signal light that has passed through the first path based on the compensation information; a determination means for determining whether or not the path of the signal light is the first path based on a state of the second communication device after the control means has transmitted the first control signal and the second control signal; A management device comprising:

4. A management device as described in any one of claims 1 to 3, characterized in that for each path of the signal light from the first communication device to the second communication device, the group delay imparted to the signal light received by the second communication device is different.

5. A communication device for an optical communication network, comprising: a storage means for storing path information indicating a group delay given to the signal light received by the communication device for each path of the signal light from another communication device to the communication device; a determination unit that determines a group delay given to the received signal light and determines a path of the signal light based on the determined group delay and the path information; A communication device comprising:

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