Connection system and connection method

Abstract

A connection system and a connection method according to the present invention use an in-facility node installed on a loop-shaped optical fiber and optical cross-connects in a plurality of external nodes arranged at different positions on the optical fiber. Among the optical cross-connects, with respect to a first optical cross-connect and a second optical cross-connect, a first optical fiber core included in the optical fiber passes through the in-facility node and the first optical cross-connect, and does not pass through the second optical cross-connect.

Description

Connection system and connection method

[0001] The present disclosure relates to a connection system and a connection method.

[0002] Non-Patent Document 1 discloses a system in an optical fiber network (multi-stage loop network) consisting of multiple loop networks, which is composed 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 fiber at the out-station node. It also discloses that the optical node (out-station node) is equipped with an optical cross-connect unit and a port monitoring unit attached to the optical cross-connect unit.

[0003] Non-patent document 2 discloses a configuration in which an optical cross-connect unit mounted in an optical node (off-site node) located at the point where an upper loop and a lower loop of a multi-stage loop network meet is composed of multiple optical switches.

[0004] Non-patent document 3 discloses a system in which the same core wire is shared by all off-site nodes in the upper loop of a multi-stage loop network, and the optical fiber core wire is accommodated via an optical cross-connect unit installed in the off-site node.

[0005] 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 Optical Fiber Application Technology Study Group OFT2022-6, 2022, "Study on Multi-Core Cylindrical Ferrules for Remotely Controlled Optical Fiber Rotary Switches," IEICE General Conference b-13-15, 2021, "Optimization of Multistage Loop Optical Access Network Configurations to Reduce Expansion Construction Work,"

[0006] According to the system described in Non-Patent Document 3, the same core wire is shared by all off-site nodes in the upper loop of the multi-stage loop network to accommodate the optical fiber core wire in the lower loop, so there is a problem that the optical loss occurring in the communication route increases as the number of off-site nodes that are passed through increases.

[0007] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a connection system and a connection method that can prevent an increase in optical loss occurring in a communication route when optical fiber cores are accommodated through a multistage loop network, and that can estimate the magnitude of optical loss occurring in the communication route and switch the target optical fiber cores used in the communication route.

[0008] In order to solve the above-mentioned problems, a connection system and a connection method according to the present disclosure use an on-site node installed on a looped optical fiber and optical cross connects in a plurality of off-site nodes arranged at different positions on the optical fiber, and for a first optical cross connect and a second optical cross connect among the optical cross connects, a first optical fiber core included in the optical fiber passes through the on-site node and the first optical cross connect, but does not pass through the second optical cross connect.

[0009] According to the present disclosure, when optical fiber cores are accommodated in a multistage loop network, it is possible to suppress an increase in optical loss occurring in a communication route. Furthermore, it is possible to estimate the magnitude of optical loss occurring in a communication route and realize switching of the target optical fiber cores used in the communication route.

[0010] 1 is a diagram illustrating an example of the configuration of a connection system according to the present disclosure; FIG. 2 is a diagram illustrating a first example of the topology of optical fiber cores; FIG. 3 is a diagram illustrating a first example of the configuration of an optical cross connect; FIG. 4 is a diagram illustrating a second example of the configuration of an optical cross connect; FIG. 5 is a schematic diagram illustrating components of an optical cross connect and port monitoring along the path of communication light; FIG. 6 is a diagram illustrating a second example of the topology of optical fiber cores; and FIG. 7 is a diagram illustrating a third example of the topology of optical fiber cores.

[0011] 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.

[0012] 1. Configuration of a Connection System (First Example) Figure 1 is a diagram showing an example of the configuration of a connection system according to the present disclosure. The connection 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 to form a loop.

[0013] 1 shows the connection system 1 having four off-site nodes, but the number of off-site nodes included in the connection system 1 is not limited to four. The number of off-site nodes included in the connection system 1 may be one or more.

[0014] 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.

[0015] An optical cross connect XC is installed in each of the off-site nodes ND1 to ND4, and multiple optical cross connects XC are arranged on the optical fiber FB. One on-site node may have one or multiple optical cross connects XC.

[0016] 2 is a diagram showing a first example of the topology of optical fiber cores. Focusing on a first optical cross-connect and a second optical cross-connect, which are located at different positions among a plurality of optical cross-connects arranged on an optical fiber FB, the first optical fiber core included in the optical fiber FB passes through the in-house node ND0 and the first optical cross-connect, but does not pass through the second optical cross-connect. Port monitoring units installed in association with the first and second optical cross-connects are not shown.

[0017] For example, the optical fiber core TP1 passes through the on-site node ND0 and the optical cross-connect installed in the off-site node ND1. On the other hand, the optical fiber core TP1 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND2 to ND4. Therefore, with respect to the optical fiber core TP1, the optical cross-connect installed in the off-site node ND1 corresponds to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND2 to ND4 correspond to the second optical cross-connect.

[0018] The optical fiber core TP2 passes through the on-site node ND0 and the optical cross-connect and port monitor installed in the off-site node ND2. On the other hand, the optical fiber core TP2 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND1, ND3, and ND4. Therefore, with respect to the optical fiber core TP2, the optical cross-connect installed in the off-site node ND2 corresponds to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND1, ND3, and ND4 correspond to the second optical cross-connect.

[0019] The optical fiber core TP3 passes through the on-site node ND0 and the optical cross-connect and port monitor installed in the off-site node ND3. On the other hand, the optical fiber core TP3 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND1, ND2, and ND4. Therefore, with respect to the optical fiber core TP3, the optical cross-connect installed in the off-site node ND3 corresponds to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND1, ND2, and ND4 correspond to the second optical cross-connect.

[0020] The optical fiber core TP4 passes through the on-site node ND0 and the optical cross-connect and port monitor installed in the off-site node ND4. On the other hand, the optical fiber core TP4 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND1 to ND3. Therefore, with respect to the optical fiber core TP4, the optical cross-connect installed in the off-site node ND4 corresponds to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND1 to ND3 correspond to the second optical cross-connect.

[0021] Thus, according to the topology of optical fiber cores shown in FIG. 2, optical fiber cores are not shared between a specific off-site node and other off-site nodes.

[0022] On the other hand, if a failure occurs in the communication route on the optical fiber FB, the interruption of the communication service can be resolved by switching to a communication route in the opposite direction. For example, assume that the terminals TM0 and TM1 shown in Fig. 1 are communicating with each other in the optical fiber core topology shown in Fig. 2. In this case, if a failure occurs in the communication route in the first direction AR1 on the optical fiber FB, the interruption of the communication service can be resolved by switching to a communication route in the second direction AR2, which is opposite to the first direction AR1.

[0023] Furthermore, both the communication route in the first direction AR1 and the communication route in the second direction AR2 pass only through the optical cross-connect and port monitor of the off-site node ND1, which reduces optical loss in the communication route compared to a communication route that passes through multiple optical cross-connects and port monitors.

[0024] Fig. 3 is a diagram showing a first example of the configuration of an optical cross connect. Fig. 4 is a diagram showing a second example of the configuration of an optical cross connect. Optical cross connects XC as shown in Figs. 3 and 4 are installed in off-site nodes ND1 to ND4. Note that the form of the installed optical cross connect XC is not limited to that shown in Figs. 3 and 4.

[0025] 3 has two ports for each of the routes D1 to D4, for a total of eight ports. For example, routes D1 and D2 are connected to an optical fiber FB that constitutes an upper loop, and routes D3 and D4 are connected to an optical fiber that constitutes a lower loop.

[0026] Ports P11, P12, P21, P22, P31, P32, P41, and P42 are provided with optical switches SW11, SW12, SW21, SW22, SW31, SW32, SW41, and SW42, respectively. Each optical switch has six channel outputs, and the channels of the optical switches are pre-connected to each other in a mesh configuration. Switching cores (switching ports) at an off-site node requires switching two optical switches.

[0027] 4 has one port for each of the routes D1 to D4, for a total of four ports. For example, routes D1 and D2 are connected to an optical fiber FB that constitutes an upper loop, and routes D3 and D4 are connected to an optical fiber that constitutes a lower loop.

[0028] Optical switches SW1, SW2, SW3, and SW4 are provided at ports P1, P2, P3, and P4, respectively. Each optical switch has three channel outputs, and the channels of the optical switches are mesh-connected to each other in advance. Switching the core wires (switching ports) at an off-site node requires switching two optical switches.

[0029] The optical loss that occurs when passing through optical cross-connects and port monitors will now be described in more detail. Figure 5 is a schematic diagram showing the components of optical cross-connects and port monitors along the path of communication light.

[0030] Inside the optical cross connect, two optical switches SW are arranged along the path of the communication light. Also, two port monitoring modules MD are arranged outside the optical cross connect as port monitoring associated therewith. In addition, an optical connector CN and a fusion splicer ML connecting the optical switches SW are arranged along the path of the communication light. However, using the optical connector CN and the fusion splicer ML to connect the optical switches SW and port monitoring modules MD is just one example, and other configurations are also possible.

[0031] Each time a communication route passes through one off-site node, i.e., an optical cross-connect and a port monitor, it passes through two optical switches SW and two port monitor modules MD. Therefore, each time a communication route passes through one off-site node, optical loss occurs due to passing through the components of these off-site nodes.

[0032] For example, if an optical loss of 0.5 dB occurs for each pass through the optical switch SW and 0.75 dB for each pass through the port monitoring module MD, the optical loss for each pass through the off-site node will be at least 2.5 dB. The optical loss for each pass through the optical cross-connect is large compared to the loss of the optical fiber in the communication route (generally 0.2 dB to 0.3 dB / km).

[0033] Therefore, by reducing the number of off-site nodes through which the communication route passes, it is possible to suppress optical loss occurring in the communication route.

[0034] For example, assume that communication is performed along a communication route between terminals TM0 and TM1 in the connection system shown in Fig. 1. The communication route in the first direction AR1 passes through off-site node ND1, and therefore optical loss equivalent to that of one off-site node occurs in the communication route.

[0035] On the other hand, if the communication route in the second direction AR2 passes through the optical cross-connects of the off-site nodes ND1 to ND4, optical loss equivalent to four off-site nodes will occur in the communication route. Therefore, there is a problem that optical loss is more likely to be large in the communication route in the second direction AR2 than in the communication route in the first direction AR1. Another problem is that the optical loss values ​​of the selectable communication routes are limited.

[0036] Therefore, in this disclosure, the optical fiber core TP1 is configured to pass through the optical cross-connect and port monitor installed in the off-site node ND1, but not through the optical cross-connect and port monitor installed in the off-site nodes ND2 to ND4.

[0037] [2. Configuration of the Connection System (Second Example)] Fig. 6 is a diagram showing a second example of the topology of the optical fiber core wire. The topology of the optical fiber core wire shown in Fig. 6 is different from the topology of the optical fiber core wire shown in Fig. 2, but the connection system 1 itself has an on-site node ND0 and off-site nodes ND1 to ND4 arranged on a loop-shaped optical fiber FB, as shown in Fig. 1.

[0038] The optical fiber core TPA (two optical fiber cores indicated by solid and dashed lines) passes through the on-site node ND0 and all the optical cross-connects and port monitors installed in the off-site nodes ND1 to ND4.

[0039] The optical fiber core TP12 passes through the on-site node ND0 and the optical cross-connects and port monitors installed in the off-site nodes ND1 and ND2. The optical fiber core TP12 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND3 and ND4. Therefore, with respect to the optical fiber core TP12, the optical cross-connects installed in the off-site nodes ND1 and ND2 correspond to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND3 and ND4 correspond to the second optical cross-connect.

[0040] The optical fiber core TP34 passes through the on-site node ND0 and the optical cross-connects and port monitors installed in the off-site nodes ND3 and ND4. The optical fiber core TP34 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND1 and ND2. Therefore, with respect to the optical fiber core TP34, the optical cross-connects installed in the off-site nodes ND3 and ND4 correspond to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND1 and ND2 correspond to the second optical cross-connect.

[0041] For example, assume that the terminals TM0 and TM1 shown in Fig. 1 are communicating with each other in the optical fiber core topology shown in Fig. 6. The optical fiber core TP12 is shared by the optical cross-connects related to the off-site nodes ND1 and ND2 and for port monitoring, and the number of optical cross-connects that the communication route via the optical fiber core TP12 passes through is limited to a maximum of two. Therefore, optical loss equivalent to four optical cross-connects related to the off-site nodes installed on the optical fiber FB does not occur in the communication route, and optical loss is reduced.

[0042] In addition, if the optical fiber core wires are not shared among some off-site nodes, there is a risk that the number of available optical fiber core wires will be insufficient, making it impossible to flexibly provide optical fiber core wires. However, the probability of an occurrence in which optical fiber core wires cannot be provided is low. According to the optical fiber core wire topology shown in Figure 6, the maximum number of communication routes that can be connected to the optical fiber FB, which is the upper loop, for each lower loop connected via the off-site nodes ND1 to ND4 is six. In contrast, if the optical fiber core wires are shared among all off-site nodes, the maximum number of communication routes that can be connected to each lower loop is eight.

[0043] Assuming that user demand occurs with equal probability in each lower loop, the probability that a situation will arise in which seven or eight communication routes must be secured in a specific lower loop is 4 × (1 / 4) ８ +4 x 3 x 8 x (1 / 4) ８ Therefore, in order to deal with the remaining 99.85% of situations, a maximum of six communication routes can be set for each lower loop, which is sufficient.

[0044] In other words, if some off-site nodes do not share optical fiber cores, there may be a shortage of available optical fiber cores, but this rarely occurs and is unlikely to cause operational problems. The benefit of not sharing optical fiber cores among some off-site nodes is the significant reduction in optical loss.

[0045] Next, it is assumed that the terminal TM0 and the terminal TM2 shown in FIG. 1 are communicating with each other in the topology of the optical fiber core wire shown in FIG.

[0046] In this case, when the optical fiber core TP12 is used as the communication route, the number of optical cross connects that the communication route passes through is 1 or 2. When the optical fiber core TPA is used as the communication route, the number of optical cross connects that the communication route passes through is 2 or 3. The number of optical cross connects that the communication route passes through varies depending on whether the communication route in the first direction AR1 or the second direction AR2 is adopted.

[0047] The number of optical cross-connects and port monitoring ports through which the optical fiber core wire passes can be determined based on information about which optical fiber core wire is used to establish a communication route. Therefore, the optical loss occurring in the communication route in the optical fiber core wire can be calculated based on the number of optical cross-connects and port monitoring ports through which the optical fiber core wire passes.

[0048] For example, a controller installed in terminal TM0 may identify the optical fiber core (target optical fiber core) used in the communication route between terminal TM0 and terminal TM2, and calculate the optical loss occurring in the communication route in the target optical fiber core based on the number of optical cross-connects and port monitoring ports through which the target optical fiber core passes.

[0049] Furthermore, the controller installed in the terminal TM0 may switch the target optical fiber core wire to change the optical loss value occurring in the communication route. Conversely, it is possible to select a desired route from among a plurality of communication routes having different optical loss values, or to switch to the selected route, depending on the required optical loss value for the communication route that enables communication between the terminal TM0 and the terminal TM2.

[0050] 3. Configuration of the Connection System (Third Example) Figure 7 is a diagram showing a third example of the topology of the optical fiber core wire. The topology of the optical fiber core wire shown in Figure 7 is different from the topology of the optical fiber core wire shown in Figure 2, but the connection system 1 itself has an on-site node ND0 and off-site nodes ND1 to ND4 arranged on a loop-shaped optical fiber FB, as shown in Figure 1.

[0051] The optical fiber core TPA (two optical fiber cores indicated by solid and dashed lines) passes through the on-site node ND0 and all the optical cross-connects and port monitors installed in the off-site nodes ND1 to ND4.

[0052] The optical fiber core TP13 passes through the on-site node ND0 and the optical cross-connects and port monitors installed in the off-site nodes ND1 and ND3. The optical fiber core TP13 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND2 and ND4. Therefore, with respect to the optical fiber core TP13, the optical cross-connects installed in the off-site nodes ND1 and ND3 correspond to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND2 and ND4 correspond to the second optical cross-connect.

[0053] The optical fiber core TP24 passes through the on-site node ND0 and the optical cross-connects and port monitors installed in the off-site nodes ND2 and ND4. The optical fiber core TP24 does not pass through the optical cross-connects and port monitors installed in the off-site nodes ND1 and ND3. Therefore, with respect to the optical fiber core TP24, the optical cross-connects installed in the off-site nodes ND2 and ND4 correspond to the first optical cross-connect, and the optical cross-connects installed in the off-site nodes ND1 and ND3 correspond to the second optical cross-connect.

[0054] 7, the number of optical cross-connects and port monitoring ports through which the optical fiber core wire passes can be determined based on information about which optical fiber core wire is used to establish a communication route. Therefore, the optical loss occurring in the communication route in the optical fiber core wire can be calculated based on the number of optical cross-connects and port monitoring ports through which the optical fiber core wire passes.

[0055] For example, a controller installed in terminal TM0 may identify the optical fiber core (target optical fiber core) used in the communication route between terminal TM0 and terminal TM2, and calculate the optical loss occurring in the communication route in the target optical fiber core based on the number of optical cross-connects and port monitoring ports through which the target optical fiber core passes.

[0056] Furthermore, the target optical fiber core may be switched by a controller installed in the terminal TM0 to change the value of the optical loss occurring in the communication route.

[0057] As described above in detail, the connection system and connection method according to the present disclosure use an on-site node installed on a looped optical fiber and optical cross connects in a plurality of off-site nodes arranged at different positions on the optical fiber. With regard to the first and second optical cross connects among the optical cross connects, the first optical fiber core included in the optical fiber passes through the on-site node and the first optical cross connect, but does not pass through the second optical cross connect.

[0058] This makes it possible to prevent an increase in optical loss occurring in a communication route when optical fiber cores are accommodated through a multistage loop network. In particular, optical loss occurring in a communication route can be reduced compared to a communication route that passes through all of the multiple optical cross-connects provided in the optical fiber that constitutes the upper loop. Furthermore, it is possible to estimate the magnitude of optical loss occurring in the communication route and switch the target optical fiber cores used in the communication route.

[0059] In the connection system and connection method according to the present disclosure, the in-house node may be connected to a controller, and the controller may calculate optical loss occurring in a communication route of a target optical fiber core line based on the number of optical cross-connects and port monitorings through which the target optical fiber core line included in the optical fiber passes. This makes it possible to estimate the magnitude of optical loss occurring in the communication route and perform processing such as switching the target optical fiber core line used in the communication route.

[0060] In the connection system and connection method according to the present disclosure, the second optical fiber core wire included in the optical fiber may pass through an intra-office node, a first optical cross connect, and a second optical cross connect, and the controller may change the optical loss value by switching the target optical fiber core wire between the first optical fiber core wire and the second optical fiber core wire. This makes it possible to improve convenience when accommodating optical fiber core wires while ensuring the quality required for the communication route.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 1 Connection system AR1 First direction AR2 Second direction ND0 In-station node ND1 to ND4 Out-station node CN Optical connector FB Optical fiber MD Port monitoring module ML Fusion splicer SW Optical switch TP1 to 4, TPA, TP12, TP34, TP13, TP24 Optical fiber core TM0 to TM4 Terminal XC Optical cross connect

Claims

1. A connection system comprising an on-site node installed on a looped optical fiber, and optical cross-connects in a plurality of off-site nodes arranged at different positions on the optical fiber, wherein, for a first optical cross-connect and a second optical cross-connect among the optical cross-connects, a first optical fiber core included in the optical fiber passes through the on-site node and the first optical cross-connect, but does not pass through the second optical cross-connect.

2. The connection system according to claim 1, wherein the in-house node is connected to a controller, and the controller calculates the optical loss occurring in the communication route of the target optical fiber core based on the number of optical cross-connects and port monitoring ports through which the target optical fiber core included in the optical fiber passes.

3. The connection system described in claim 2, wherein a second optical fiber core included in the optical fiber passes through the in-house node, the first optical cross connect, and the second optical cross connect, and the controller switches the target optical fiber core between the first optical fiber core and the second optical fiber core to change the value of the optical loss.

4. A connection method for a connection system comprising an on-site node installed on a looped optical fiber and optical cross-connects in a plurality of off-site nodes arranged at different positions on the optical fiber, wherein, for a first optical cross-connect and a second optical cross-connect among the optical cross-connects, a first optical fiber core wire included in the optical fiber is installed via the on-site node and the first optical cross-connect, but not via the second optical cross-connect.

Images