Optical path switching system and optical path switching method

Abstract

The present invention provides an optical path switching system and an optical path switching method in which an intramural node and one or more extramural nodes arranged on looped optical fiber are used. A terminal connected to the extramural node is connected to the intramural node via a first core extending from the intramural node in a first direction along the optical fiber, while power supply and control are carried out from the intramural node via a second core extending from the intramural node in a second direction going the opposite way along the optical fiber relative to the first direction. When communication via the first core is unavailable, the connection is switched from the first core to a third core extending from the intramural node in the second direction, and the terminal is connected to the intramural node via the third core.

Description

Optical path switching system and optical path switching method

[0001] The present disclosure relates to an optical path switching system and an optical path switching method.

[0002] Non-Patent Document 1 discloses a system in which an optical fiber network (multi-stage loop network) consisting of multiple loop networks is comprised of an optical node (in-station node) installed in an environment where commercial power is available within a communications building, and one or more optical nodes (out-station node) installed outdoors. Flexible configuration of optical fiber communication routes is achieved by remotely switching the core wires at the out-station node. It has also been proposed to use a self-holding optical switch, which maintains its state even if power is interrupted, as the optical switch used to switch the core wires. Therefore, the state of the optical switch is maintained even if power runs out for some reason.

[0003] Patent Document 1 discloses a serial connection method as a connection method of optical fiber cables for power supply and control signals for transmitting optical power supply light from an on-site node to an optical node (off-site node) and for transmitting and receiving control signals. In the serial connection method, a plurality of off-site nodes are connected from an on-site node in a beaded cascade, and the optical power supply light is sequentially taken in by a 1x2 optical switch in the off-site node. The optical fiber cables for power supply and control signals sequentially connect the off-site nodes arranged along the upper loop.

[0004] Non-patent document 2 discloses that in a serial connection method, in addition to a control signal for controlling a 1x2 optical switch in an off-site node, a control signal is sent and received to check communication with the off-site node or to check the capacitor voltage stored by optical fiber power supply.

[0005] International Publication No. 2022 / 102103

[0006] IEICE Optical Fiber Application Technology Study Group OFT2021-62, 2021, "Study on remote optical path switching nodes and optical cross-connect functions in multistage loop networks" IEICE Society Conference b-8-3, 2022, "Study on remote operation and management maintenance functions in remote optical path switching nodes"

[0007] According to the system described in Non-Patent Document 1, redundancy in the upper loop of a multi-stage loop network is used to restore a communication route in the event of an optical fiber break. However, if an optical fiber breaks, the optical fiber core wire for power supply and control signals may also be broken, which may make it impossible to remotely switch the core wire at the off-site node. As a result, there is a problem that a communication route to a terminal connected to the off-site node may not be secured.

[0008] The present disclosure has been made in view of the above-mentioned problems, and has as its object to provide an optical path switching system and an optical path switching method that can ensure communication with a terminal connected to an off-site node even if an optical fiber is broken.

[0009] In order to solve the above-mentioned problems, an optical path switching system and an optical path switching method according to the present disclosure use an on-site node and one or more off-site nodes arranged on a looped optical fiber. A terminal connected to the off-site node is connected to the on-site node via a first core wire extending from the on-site node in a first direction on the optical fiber, and is powered and controlled by the on-site node via a second core wire extending from the on-site node in a second direction on the optical fiber opposite to the first direction. When communication via the first core wire is not possible, the first core wire is switched to a third core wire extending from the on-site node in the second direction, and the terminal is connected to the on-site node via the third core wire.

[0010] According to the present disclosure, even if an optical fiber is broken, communication with a terminal connected to an off-site node can be ensured.

[0011] Fig. 1 is a diagram illustrating an example of the configuration of an optical path switching system according to an embodiment of the present disclosure; Fig. 2 is a diagram illustrating the topology of a communication path (main system) and the topology of a core wire for power supply and control; Fig. 3 is a diagram illustrating the topology of a communication path (subsystem) and the topology of a core wire for power supply and control; Fig. 4 is a diagram illustrating a modified example of the topology of a core wire for power supply and control; Fig. 5 is a diagram illustrating the topology of a communication path (main system) and the topology of a core wire for power supply and control according to a comparative example;

[0012] Next, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description, the same components are designated by the same reference numerals and redundant description will be omitted.

[0013] [Configuration of Optical Path Switching System] Figure 1 is a diagram illustrating an example of the configuration of an optical path switching system according to an embodiment of the present disclosure. The optical path switching system 1 has an on-site node ND0 and off-site nodes ND1 to ND4 arranged on a loop-shaped optical fiber FB. The on-site node ND0 and the off-site nodes ND1 to ND4 are arranged in order on the optical fiber FB. One end and the other end of the optical fiber FB are connected to the on-site node ND0, forming a loop.

[0014] 1 shows the optical path switching system 1 having four off-site nodes, but the present invention is not limited to this. The optical path switching system 1 may have one or more off-site nodes.

[0015] The terminals TM0 to TM4 are connected to the on-site node ND0 and the off-site nodes ND1 to ND4, respectively. As an example, Figure 1 shows the state in which the terminals TM1 to TM4 and the off-site nodes ND1 to ND4 are connected by a multistage loop made of optical fiber. The connections between the terminals and the nodes are made by optical fiber.

[0016] [Configuration of the communication path (main system)] Next, the communication path between the terminals TM1 to TM4 connected to the off-site nodes ND1 to ND4 and the terminal TM0 connected to the on-site node ND0 will be described. In addition, the core wires for power supply and control to the off-site nodes ND1 to ND4 will be described.

[0017] 2 shows the topology of the communication path (main system) and the topology of the power supply and control cores. The off-site nodes ND1 to ND4 are connected to the on-site node ND0 by the optical fiber FB via first cores extending from the on-site node ND0 in the first direction AR1 on the optical fiber FB.

[0018] The first core provides a primary communication path to the off-site nodes ND1 to ND4, and passes through the off-site nodes ND1, ND2, ND3, and ND4 in this order in a first direction AR1.

[0019] More specifically, terminal TM0 is connected to terminal TM1 via on-site node ND0 and off-site node ND1, and communicates with terminal TM1. Terminal TM0 is connected to terminal TM2 via on-site node ND0 and off-site nodes ND1 and ND2, and communicates with terminal TM2. Terminal TM0 is connected to terminal TM3 via on-site node ND0 and off-site nodes ND1, ND2, and ND3, and communicates with terminal TM3. Terminal TM0 is connected to terminal TM4 via on-site node ND0 and off-site nodes ND1, ND2, ND3, and ND4, and communicates with terminal TM4.

[0020] On the other hand, the off-site nodes ND1 to ND4 are powered and controlled by the on-site node ND0 via a second core wire extending from the on-site node ND0 in a second direction AR2 opposite to the first direction AR1 on the optical fiber FB. One end of the second core wire is connected to the on-site node ND0.

[0021] As shown in the range PW in Figure 2, the second fiber passes through the off-site nodes ND4, ND3, ND2, and ND1 in the second direction AR2 to supply optical power to each off-site node. The off-site nodes ND1 to ND4 perform photoelectric conversion based on the optical power and charge storage batteries (not shown). In addition, the off-site nodes ND1 to ND4 use the power generated by photoelectric conversion based on the optical power to drive devices (not shown).

[0022] The second core transmits a control signal to each off-site node via the off-site nodes ND4, ND3, ND2, and ND1 in that order. The off-site nodes ND1 to ND4 switch the communication paths provided to the terminals TM1 to TM4 based on the control signal. For example, the off-site nodes ND1 to ND4 switch the communication path between the primary system and the secondary system. The switching of the communication path between the primary system and the secondary system is performed for each of the terminals TM1 to TM4.

[0023] The off-site nodes ND1 to ND4 may transmit a response signal based on the control signal. The second core may transmit the response signal from the off-site nodes ND1 to ND4 to the on-site node ND0.

[0024] 3 shows the topology of the communication path (subsystem) and the topology of the power supply and control cores. The off-site nodes ND1 to ND4 are connected to the on-site node ND0 by the optical fiber FB via third cores extending from the on-site node ND0 in the second direction AR2 on the optical fiber FB.

[0025] The third core provides a secondary communication path to the off-site nodes ND1 to ND4, and passes through the off-site nodes ND4, ND3, ND2, and ND1 in this order in the second direction AR2.

[0026] The secondary communication path is used when communication is not possible through the primary communication path, i.e., when communication is not possible through the first core line, switching is made from the first core line to the third core line.

[0027] More specifically, terminal TM1 is connected to on-site node ND0 via off-site nodes ND1, ND2, ND3, and ND4, and communicates with terminal TM0. Terminal TM2 is connected to on-site node ND0 via off-site nodes ND2, ND3, and ND4, and communicates with terminal TM0. Terminal TM3 is connected to on-site node ND0 via off-site nodes ND3 and ND4, and communicates with terminal TM0. Terminal TM4 is connected to on-site node ND0 via off-site node ND4, and communicates with terminal TM0.

[0028] [Restoration Method in Case of Disconnection] Next, a restoration method in the case where the optical fiber FB is disconnected for some reason while communication is being performed on the communication path of the main system will be described.

[0029] In the looped optical fiber FB, when traveling in the first direction AR1, the section between on-site node ND0 and off-site node ND1 is designated as section SC1. The section between off-site node ND1 and off-site node ND2 is designated as section SC2. The section between off-site node ND2 and off-site node ND3 is designated as section SC3. The section between off-site node ND3 and off-site node ND4 is designated as section SC4. The section between off-site node ND4 and on-site node ND0 is designated as section SC5.

[0030] If a break occurs in section SC1, the communication path is broken at terminals TM1 to TM4. On the other hand, the power supply and control cores are not broken, as shown by the range PW in FIG.

[0031] Therefore, a control signal is sent to the off-site nodes ND1 to ND4 to switch the communication path provided to the terminals TM1 to TM4 from the primary system to the secondary system. Specifically, the communication path shown in FIG. 2 is switched to the communication path shown in FIG.

[0032] If a break occurs in section SC2, the communication path will be broken at terminals TM2 to TM4. The communication path at terminal TM1 will not be broken. On the other hand, the power supply and control core will be broken, and control signals will no longer be able to be sent to off-site node ND1. Control signals will still be able to be sent to off-site nodes ND2 to ND4.

[0033] Therefore, a control signal is sent to the off-site nodes ND2 to ND4 to switch the communication path provided to the terminals TM2 to TM4 from the primary system to the secondary system. Because the communication path to the terminal TM1 is not broken, the communication path remains the primary system. In particular, if the off-site nodes use self-holding optical switches that maintain the switched state even if power is interrupted, the communication path will not be changed.

[0034] If a break occurs in section SC3, the communication path is broken at terminals TM3 and TM4. The communication path at terminals TM1 and TM2 is not broken. On the other hand, the power supply and control core is broken, and control signals cannot be sent to off-site nodes ND1 and ND2. Control signals can be sent to off-site nodes ND3 and ND4.

[0035] Therefore, a control signal is sent to the off-site nodes ND3 and ND4 to switch the communication path provided to the terminals TM3 and TM4 from the primary system to the secondary system. Since the communication path to the terminals TM1 and TM2 is not broken, the communication path remains the primary system.

[0036] If a break occurs in section SC4, the communication path at terminal TM4 is broken. The communication paths between terminals TM1 to TM3 are not broken. However, the power supply and control core is broken, and control signals cannot be sent to off-site nodes ND1 to ND3. Control signals can still be sent to off-site node ND4.

[0037] Therefore, a control signal is sent to the off-site node ND4 to switch the communication path provided to the terminal TM4 from the primary system to the secondary system. Since the communication paths of the terminals TM1 to TM3 are not broken, the communication paths remain as the primary system.

[0038] If a break occurs in section SC5, the communication paths of terminals TM1 to TM4 will not be broken, but the power supply and control core will be broken, making it impossible to transmit control signals to off-site nodes ND1 to ND4.

[0039] Since the communication paths of the terminals TM1 to TM4 are not broken, the communication paths remain as the main system.

[0040] In this way, by installing communication paths for the main system and the secondary system and core wires for power supply and control as shown in Figures 2 and 3, even if a break occurs in any of sections SC1 to SC5, a communication path can be secured for terminals TM1 to TM4 after the break.

[0041] In the above example, the optical path switching system 1 has four off-site nodes, but is not limited to this. Even if there is one or more off-site nodes, a communication path can be secured for a terminal connected to the off-site node after a line break in a similar manner.

[0042] [Modification of the topology of the power supply / control core wire] Figure 4 is a diagram showing a modification of the topology of the power supply / control core wire. Unlike the topology of the power supply / control core wire shown in the range PW in Figures 2 and 3, in addition to one end of the second core wire, the other end of the second core wire may be connected to the on-site node ND0. Figure 4 shows that in section SC1, the second core wire is extended from the off-site node ND1 and connected to the on-site node ND0.

[0043] The in-station node ND0 may include a photodetector and a receiver. The photodetector receives light input to one end of the second core and output from the other end. Specifically, when light transmitting power supply light and a control signal is input to one end of the second core, the photodetector may receive light output from the other end of the second core.

[0044] The receiver may also receive a response signal from each of the off-site nodes ND1 to ND4, the response signal being output from one end of the second core line. The receiver receives a response signal from each of the off-site nodes ND1 to ND4.

[0045] According to a modified topology of the power supply and control core wire, it is possible to detect a broken section on the optical fiber FB.

[0046] In order to detect the disconnected section, it is determined whether or not the off-site nodes ND1 to ND4 are controllable based on the presence or absence of a response signal from the off-site nodes ND1 to ND4.

[0047] If there is no response signal from the off-site nodes ND1 to ND4, it can be determined that the off-site nodes ND1 to ND4 cannot be controlled, and in this case, it can be detected that the section SC5 is broken.

[0048] If there is a response signal from the off-site node ND4 but no response signals from the off-site nodes ND1 to ND3, it can be determined that the off-site nodes ND1 to ND3 cannot be controlled. In this case, it can be detected that the section SC4 is broken.

[0049] If there are response signals from the off-site nodes ND3 and ND4 but no response signals from the off-site nodes ND1 and ND2, it can be determined that the off-site nodes ND1 and ND2 cannot be controlled. In this case, it can be detected that the section SC3 is broken.

[0050] If there are response signals from the off-site nodes ND2 to ND4 but no response signal from the off-site node ND1, it can be determined that the off-site node ND1 cannot be controlled. In this case, it can be detected that the section SC2 is broken.

[0051] When a response signal is received from the off-site nodes ND1 to ND4, the off-site nodes ND1 to ND4 are controlled so that the power supply light is not used for power generation at the off-site nodes ND1 to ND4 but is instead circulated backward in the second direction AR2. If light cannot be received via the light receiving element in this state, it can be detected that the section SC1 is broken.

[0052] In addition, if light can be received via the light receiving element, it can be determined that there is no disconnected section.

[0053] For example, the detection of the broken section on the optical fiber FB may be performed by a controller connected to the in-house node ND0. For example, the controller may be mounted on the terminal TM0. The controller identifies the broken location of the optical fiber based on whether or not light is received via a light receiving element and whether or not a response signal is received.

[0054] The controller (an example of a control unit or a processing unit) is a general-purpose computer including a CPU (Central Processing Unit), a memory, and an input / output unit. A computer program (optical path switching program) for functioning as a part of the optical path switching system 1 is installed in the controller.

[0055] It is also possible to configure the information processing circuit by preparing dedicated hardware for executing each of the information processes described below. Also, multiple information processing circuits may be configured with individual hardware.

[0056] The controller transmits a control signal to the off-site nodes ND1 to ND4 via the on-site node ND0 and receives a response signal from the off-site nodes ND1 to ND4. The controller also controls the off-site nodes ND1 to ND4 so that the power supply light is not used for photoelectric conversion at the off-site nodes ND1 to ND4 but flows backward in the second direction AR2. In this state, the controller determines whether light can be received via the light receiving element.

[0057] In addition, the controller may store data such as the time when the control signal was transmitted, the destination off-site node, and whether or not a response signal was received. Furthermore, the controller may store data such as the time when light was received via the light receiving element.

[0058] Furthermore, the controller may acquire data on the transmission of control signals to off-site nodes ND1 to ND4, the reception of response signals, and the presence or absence of light reception by the light-receiving elements within a predetermined time interval to determine the presence or absence of a break in each section (sections SC1 to SC5) of the optical fiber FB. The controller may then determine the presence or absence of a break at the predetermined time interval based on the acquired data. Here, the predetermined time interval may be determined based on the time required to transmit control signals and receive response signals between the on-site node ND0 and the off-site nodes ND1 to ND4. The predetermined time interval may also be determined based on the number of off-site nodes installed.

[0059] The controller may switch the communication path from the primary system to the secondary system based on the result of determining whether or not there is a break in each section (sections SC1 to SC5) of the optical fiber FB. When switching the communication path, the controller may transmit a control signal to the off-site nodes ND1 to ND4.

[0060] [Comparative Example] Fig. 5 is a diagram showing the topology of the communication path (main system) and the topology of the power supply and control core wires according to a comparative example. Unlike the topology shown in Fig. 2, the topology shown in Fig. 5 may result in cases where the communication path cannot be restored if the optical fiber FB is disconnected.

[0061] Terminal TM0 is connected to terminal TM1 via on-site node ND0 and off-site node ND1, and communicates with terminal TM1. Terminal TM0 is connected to terminal TM2 via on-site node ND0 and off-site nodes ND1 and ND2, and communicates with terminal TM2.

[0062] As a sub-system communication path, the terminal TM1 is connected to the on-site node ND0 via the off-site nodes ND1, ND2, ND3, and ND4, and communicates with the terminal TM0. The terminal TM2 is connected to the on-site node ND0 via the off-site nodes ND2, ND3, and ND4, and communicates with the terminal TM0.

[0063] On the other hand, the terminal TM0 is connected to the terminal TM3 via the on-site node ND0 and the off-site nodes ND4 and ND3, and communicates with the terminal TM3. The terminal TM0 is connected to the terminal TM4 via the on-site node ND0 and the off-site node ND4, and communicates with the terminal TM4.

[0064] As a secondary communication path, the terminal TM3 is connected to the on-site node ND0 via the off-site nodes ND1, ND2, and ND3, and communicates with the terminal TM0. The terminal TM4 is connected to the on-site node ND0 via the off-site nodes ND1, ND2, ND3, and ND4, and communicates with the terminal TM0.

[0065] According to the topology shown in Figure 5, the communication paths to the off-site nodes ND1 and ND2 are provided by core wires extending in the first direction AR1, while the communication paths to the off-site nodes ND3 and ND4 are provided by core wires extending in the second direction AR2. In optical communications, the shortest possible communication path length is generally desirable, taking into account attenuation of the power of the communication light and communication delays. Generally, communication paths are sometimes provided by the topology shown in Figure 5, rather than the topology shown in Figure 2.

[0066] Furthermore, as shown in the range PW of Figure 5, it is assumed that power supply light is supplied to each off-site node via a core wire passing through the off-site nodes ND1, ND2, ND3, and ND4 in the first direction AR1 in that order, and a control signal is transmitted.

[0067] In the topology shown in Figure 5, let us assume that a break occurs in the optical fiber FB in section SC2. In this case, the communication path between terminals TM0 and TM2 is cut. Furthermore, the core wire for power supply and control to off-site node ND2 is also cut. As a result, control of off-site node ND2 becomes impossible.

[0068] In this case, the off-site node ND2 cannot be controlled to switch the communication path to the terminal TM2 from the primary system to the secondary system, and the communication path cannot be restored.

[0069] The above problems exist in the topology shown in Fig. 5. Therefore, it is necessary to install communication paths for the main system and the secondary system, and core wires for power supply and control, as shown in Figs.

[0070] [Effects of the Embodiments] As described in detail above, the optical path switching system and optical path switching method according to the present disclosure use an on-site node and one or more off-site nodes arranged on a looped optical fiber. A terminal connected to the off-site node is connected to the on-site node via a first core wire extended from the on-site node in a first direction on the optical fiber. Power is supplied and controlled from the on-site node via a second core wire extended from the on-site node in a second direction on the optical fiber that is opposite to the first direction. When communication via the first core wire is not possible, the first core wire is switched to a third core wire extended from the on-site node in the second direction, and the terminal is connected to the on-site node via the third core wire.

[0071] This ensures communication with terminals connected to off-site nodes even if the optical fiber is broken. In particular, because primary and secondary communication paths can be prepared, communication paths with each off-site node can be ensured even if a break occurs in any section of the optical fiber.

[0072] In the optical path switching system and the optical path switching method according to the present disclosure, one end and the other end of the second core may be connected to an in-station node, and the in-station node may include a light receiving element that receives light input to the second core from one end and output from the other end, and a receiver that receives a response signal from the out-station node that is output from the one end.

[0073] This makes it possible to detect the section of the optical fiber where a break has occurred based on whether or not the light is received by the light-receiving element and whether or not a response signal has been received from the off-site node.As a result, no matter which section of the optical fiber a break has occurred in, it is possible to select a restoration method that suits the condition of the break, thereby reducing the work time and procedures required for restoration.

[0074] Furthermore, in the optical path switching system and optical path switching method according to the present disclosure, the in-house node may be connected to a controller, and the controller may identify a break in the optical fiber based on the presence or absence of reception of light via the light receiving element and the presence or absence of a response signal.

[0075] This makes it possible to automate the process of detecting broken sections on optical fiber. As a result, no matter which section of the optical fiber a break occurs in, a restoration method appropriate to the condition of the break can be automatically selected, reducing the time and steps required for restoration. This also improves convenience for users who manage and use the optical path switching system.

[0076] Each of the functions described in the above embodiments may be implemented by one or more processing circuits, including programmed processors, electrical circuits, and even devices such as application specific integrated circuits (ASICs), or circuit components arranged to perform the described functions.

[0077] Although the contents of the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these descriptions, and various modifications and improvements are possible, which will be apparent to those skilled in the art. The descriptions and drawings that form part of this disclosure should not be understood as limiting the present disclosure. Various alternative embodiments, examples, and operating techniques will be apparent to those skilled in the art from this disclosure.

[0078] Of course, the present disclosure includes various embodiments not described herein. Therefore, the technical scope of the present disclosure is defined only by the invention-specifying matters according to the scope of the claims that are appropriate from the above description.

[0079] 1 Optical path switching system AR1 First direction AR2 Second direction FB Optical fiber ND0 In-station node ND1 to ND4 Out-station node SC1 to SC5 Section TM0 to TM4 Terminal

Claims

1. An optical path switching system having an on-site node and one or more off-site nodes arranged on a looped optical fiber, wherein a terminal connected to the off-site node is connected to the on-site node via a first core wire extended from the on-site node in a first direction on the optical fiber, power is supplied and controlled by the on-site node via a second core wire extended from the on-site node in a second direction on the optical fiber opposite to the first direction, and when communication via the first core wire is not possible, the optical path switching system switches from the first core wire to a third core wire extended from the on-site node in the second direction, and is connected to the on-site node via the third core wire.

2. The optical path switching system according to claim 1, wherein one end and the other end of the second core wire are connected to the on-site node, and the on-site node comprises: a photodetector that receives light input to the second core wire from the one end and output from the other end; and a receiver that receives a response signal from the off-site node that is output from the one end.

3. The optical path switching system according to claim 2, wherein the in-house node is connected to a controller, and the controller identifies a break in the optical fiber based on whether or not the light is received via the light receiving element and whether or not the response signal is received.

4. An optical path switching method for an optical path switching system having an on-site node and one or more off-site nodes arranged on a looped optical fiber, wherein a terminal connected to the off-site node is connected to the on-site node via a first core wire extended from the on-site node in a first direction on the optical fiber, power is supplied and controlled by the on-site node via a second core wire extended from the on-site node in a second direction on the optical fiber opposite to the first direction, and when communication via the first core wire is not possible, the method switches from the first core wire to a third core wire extended from the on-site node in the second direction, and is connected to the on-site node via the third core wire.

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