Optical Nodes and Switches

Abstract

An optical node of the present disclosure provides optical connectivity between local users who utilize high-capacity services. A transponder aggregation apparatus (TPA) included in the optical node is provided with a path that connects only the local port of a transmitting-side TPA and the local port of a receiving-side TPA. The connection path between the transmitting-side and receiving-side in the TPA can provide an optical path with high capacity and low latency between local users without using an electrical switch. By incorporating an optical switch function that was not provided in the optical node of the ROADM system in the related art, it is possible to connect any end user under the optical node using only optical signals without using an electrical switch.

Description

[Technical Field]

[0001] The present invention relates to an optical node, and more particularly to an optical node having a switching function. [Background technology]

[0002] As the Internet and mobile terminals have spread widely throughout the world, the need for faster and larger capacity communication networks continues to grow. One way to meet these needs is through the All-Photonics Network (APN) (Non-Patent Document 1). APN extends the optical transmission currently used in relay networks to end-to-end, and is attracting attention as a technology that realizes ultra-high speed, large capacity communication using light for each user and application.

[0003] The APN mentioned above aims to extend wavelength multiplexing technology to end users, with each user using one wavelength, achieving ultra-high-speed, high-capacity communications of up to 100 Gbps. For example, a 60-minute full HD video can be uploaded in 0.1 seconds, with a latency of just microseconds. Furthermore, experiments on relay transmission of uncompressed 8K video content have also been demonstrated.

[0004] There is a need to realize new services that require high capacity and low latency between end users, and new functions and performance are being required from existing optical communication networks. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Nikkei Electronics, "One Person, One Wavelength" for 100Gbps TCP / IP-free Ultra-low Latency, Issue 3, 2021, p40-47 [Non-patent document 2] NTT Technical Journal, 2013, Vol. 25, No. 11, pp. 16-20 Summary of the Invention [Problem to be solved by the invention]

[0006] When attempting to connect users end-to-end via optical fiber for high-capacity transmission, the current node configuration is insufficient to meet new service needs. Optical nodes in the relay system are equipped with electrical switches (e.g., routers, exchanges, L2 / L3 switches, Ethernet switches, etc.) to process user packets, and these electrical switches are shared by many users. Connections between users belonging to an optical node have traditionally been made via electrical switches. However, when providing a service exceeding 100 Gbps to a single user, such as a high-capacity end-to-end service like the ANP mentioned above, an electrical switch shared by multiple users cannot process the large volume of traffic from many users. Furthermore, current optical nodes are not equipped with optical paths to connect users.

[0007] To solve these problems, the optical node disclosed in this paper provides a new network configuration that optically connects users for high-capacity, low-latency services. [Means for solving the problem]

[0008] One embodiment of the present invention is an optical node comprising: a first optical signal aggregation device having an input port for receiving an optical signal from a corresponding local user equipment and outputting the optical signal to at least one of a plurality of output ports; and a second optical signal aggregation device having an input port for receiving the optical signal from the first optical signal aggregation device and forwarding it to any output port; the optical node having a path connecting only between the first optical signal aggregation device and the second optical signal aggregation device; and an optical connection from one local user equipment to another local user equipment being established via the path. [Effects of the Invention]

[0009] The optical node disclosed in this paper provides a new network configuration that optically connects users for high-capacity, low-latency services. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a multi-ring network. [Figure 2] FIG. 1 illustrates a prior art optical node configuration for a multi-ring network. [Figure 3] FIG. 1 illustrates a simplified prior art optical node configuration of a ROADM system. [Figure 4] 10A and 10B are diagrams illustrating changes in the usage patterns of optical nodes of local users. [Figure 5] FIG. 2 is a diagram illustrating an optical node configuration capable of connecting local users according to the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating another configuration of a connection between an optical node and a local user in the first embodiment. [Figure 7] FIG. 10 is a diagram illustrating an optical node configuration capable of connecting local users according to a second embodiment. [Figure 8] FIG. 10 is a diagram illustrating an optical node configuration capable of connecting local users according to a third embodiment. [Figure 9] FIG. 10 is a diagram illustrating the configuration of an optical exchange that connects local users according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The optical node disclosed herein provides optical connections between local users using high-capacity services. A transponder aggregator (TPA) included in the optical node has a path connecting a local port of the transmitting TPA and a local port of the receiving TPA. The connection path between the transmitting and receiving sides of the TPA allows a high-capacity optical path to be provided between local users without the use of an electrical switch.

[0012] In the following description, we first explain the basic configuration of optical nodes in current trunk networks, and then explain the problems that arise when attempting to realize end-to-end high-capacity services through optical connections using current optical nodes. After that, we explain the configuration and operation of optical nodes and various variations of the disclosed optical nodes. In the following description, terms such as user, end user, and local user all refer to local user equipment at the end of an optical communication network, such as a user's home, a service provider's building, or industrial equipment. Local user equipment corresponds to communication devices, computers, computing devices, mobile terminals, remote terminals, etc. There are no limitations on the content of the services provided or used, but they can be, for example, ultra-high-speed, high-capacity communications up to 100 Gbps.

[0013] FIG. 1 is a diagram illustrating the configuration of a multi-ring network. In optical communication networks, ring networks are used in metro core networks that bundle access networks connected to users. As disclosed in Non-Patent Document 2, multi-ring networks that transfer optical signals between multiple rings without electrical regeneration are becoming mainstream. FIG. 1(a) schematically illustrates a multi-ring network 100. Optical nodes 200, 201, 202, and 203 are connected in this order in a ring shape to ring 100-1. Optical nodes 200, 205, 203, and 204 are connected in this order in a ring shape to ring 100-2, with the two rings intersecting at optical nodes 200 and 203.

[0014] Figure 1(b) shows the configuration of one optical node in a multi-ring network. Optical node 200 has four routes A, B, C, and D because two rings intersect, and corresponding optical fibers 211-214 are connected to them. In actual optical nodes, optical fibers connecting optical nodes are connected by two optical fibers corresponding to the two propagation directions of light (clockwise or counterclockwise within the ring). As shown in Figure 1(c), optical fibers A, B, C, and D entering optical node 200 and optical fibers A', B', C', and D' exiting optical node 200 are provided. Wavelength Division Multiplexing (WDM) signals are transferred over the optical fibers.

[0015] Figure 2 shows the configuration of an optical node in a multi-ring network. Metro core networks utilize a reconfigurable optical add-drop multiplexing (ROADM) system, which enables optical signal addition and subtraction at each optical node. The optical node 200 in Figure 2 is connected to four paths, A through D, and switches a WDM signal received from one path (input side) to another path (output side). Each optical fiber on the input side is connected to a wavelength selection switch (WSS) 216a via an optical amplifier 215a. The WSS 216a has a switching function (e.g., 1 × r port) that connects each wavelength to a different output port depending on the wavelength of the input WDM signal. Each optical fiber on the output side has a WSS 216b with a multiplexing function and an input / output configuration (r × 1 port) opposite to that of the WSS 216a. The WSS 216a on the input side and the WSS 216b on the output side configure the connections between the four paths. Note that a connection between the same routes, such as from route A (optical fiber A) to route A (optical fiber A'), is meaningless, and therefore such a setting is not normally made.

[0016] The optical node 200 of the ROADM system further includes an ADD function 221a that adds optical signals from users to the optical node 200 and a DROP function 221b that drops optical signals to the users. Optical signals from users (not shown) are input to a transmitting transponder 222a, where the necessary signal processing is performed. The transponder 222a includes an electrical-to-optical conversion function, and also performs signal processing such as multiplexing control and error control, as well as supervisory control functions and wavelength conversion / wavelength allocation functions. The output of the transponder 222a is connected to an optical signal aggregation device, i.e., a transponder aggregation switch (TPA) 223a. The optical signal aggregation device has an input port that receives an optical signal from a corresponding local user equipment (LOE) and outputs the optical signal to at least one of multiple output ports.

[0017] The TPA 223a functions as an optical switch that assigns any path to any transponder, has an input port that receives an optical signal from a corresponding local user device, and outputs the optical signal to at least one of multiple output ports. Note that "TPA" is a functional name, and the specific configuration of the TPA 223a can be realized, for example, by a multicast switch (MCS). The output port of the MCS 223a on the ADD side is connected to the WSS 216b on the output side, and the optical signal from the user is transferred as a WDM signal from the optical node 200 to any path.

[0018] The operation of dropping the WDM signal into a user's optical signal on the node side opposite to the ADD side described above is performed by the DROP function 221b, i.e., the receiving-side TPA 223b and transponder 222b. The receiving-side TPA 223b can be realized by an MCS with an input / output configuration opposite to that of the transmitting side. The dropped optical signal is sent to the user from the receiving-side transponder 222b, which includes functions corresponding to the transmitting side. The transmitting-side MCS 223a and receiving-side MCS 223b in Figure 2 together constitute a TPA. For simplicity, Figure 2 shows only one transponder per MCS, but all ports (local ports) that send and receive user signals can be equipped with a transponder.

[0019] While the optical node 200 of the ROADM system shown in FIG. 2 is connected to four paths, the number of paths is not limited to this. The configuration of the TPAs ​​223a and 223b may also have other variations. Regarding the transponders 222a and 222b, the TPA-side port (local port) is in the form of an optical signal, but the user-side port may be in the form of an electrical signal or an optical signal depending on the transponder function. The optical signal format uses a signal speed of 100 Gbps or the like. Wavelength-multiplexed signals are transmitted through each of the optical fibers 211a-214a and 211b-214b of the transmission path, and for example, signals of 80 different wavelengths are multiplexed. Therefore, if the signal speed of the TPA is 100 Gbps and the number of wavelengths multiplexed in each of the optical fibers 211a-214a and 211b-214b is 80, the transmission capacity of each optical fiber is 8 Tbps.

[0020] FIG. 3 is a simplified diagram illustrating the configuration of an optical node in a ROADM system. Because FIG. 2, which shows all connections when the number of paths is four, is difficult to visualize, FIG. 3(a) illustrates the configuration of the optical node 200, focusing on only two of the four paths. Here, we focus on the TPAs ​​223a and 223b. FIG. 3(b) illustrates a more specific configuration in which the TPA 223a on the transmitting side is implemented as a multicast switch. In the MCS 223a on the transmitting (ADD) side, a one-input, multiple-output switch 230 selects a predetermined output path for the optical signal transmitted from the transponder 222a. Optical signals of different wavelengths are multiplexed by a multiple-input, single-output coupler 231. After being multiplexed, the optical signals are connected to the WSS 216b on the output side. This configuration of the MCS 223a allows a transmission signal of any wavelength to be output to any path. For simplicity, only four 1-input 4-output switches 230-1 and four 4-input 1-output couplers 231-1 are shown in FIG. 3(b). Generally, the MCS 223a is configured to have p input ports and q output ports. p is the number of ports on the transponder side, and q is the number of ports on the path side. That is, the MCS 223a is made up of p 1-input q-output switches 230-1 and q p-input 1-output couplers 231-1, and the output ports of the 1-input q-output switches 230-1 and the input ports of the p-input 1-output couplers 231-1 are connected in a mesh configuration. By providing L MCSs, M = p × L local ports are obtained.

[0021] Figure 3(c) shows a more specific configuration in which the receiving (DROP) side TPA 223b is implemented using MCS. The input and output of the transmitting side MCS 223a are swapped, allowing it to selectively receive optical signals of any wavelength input from any path on the input side. The receiving side MCS 223a is configured with an input port q and an output port p, symmetrical to the transmitting side. The TPA has L MCSs 223a on the transmitting side and L MCSs 223b on the receiving side, each arranged in parallel, providing M local ports required for local users. The output port 224a of the transmitting side TPA 223a is connected to the output side WSS 216b via connection 261. Similarly, the input port 224b of the receiving side TPA 223b is connected to the input side WSS 216a via connection 262. Therefore, the number of ports required on the path side of the MCS, q, is the number of paths, N. As described above, in the conventional optical node 200, the ports of the TPAs ​​223a and 223b facing the respective paths are connected only to the WSSs 216a and 216b connected to the respective paths.

[0022] FIG. 4 is a diagram illustrating changes in the usage patterns of optical nodes for local users. FIG. 4(a) shows the usage pattern of optical nodes in the prior art. Typically, electrical switches 241a and 241b in the same central office 240 are connected to an optical node 200 in ring 100-1. Conventionally, since the communication capacity required by end users was relatively low, local users were first connected to electrical switches 241a and 241b. Communication between users accommodated in the same electrical switch, for example, between users 250a and 250c, is established by switching processing in this electrical switch 241a. Typically, the electrical switch 241a and the electrical switch 241b are connected by a relatively large-capacity connection path 242, for example, 100 Gbps, in which communication signals from multiple users are multiplexed. Communication between users accommodated in different electrical switches is established by the two electrical switches 241a and 241b. For example, communication between user 250a accommodated by electrical switch 241a and user 250b accommodated by electrical switch 241b is exchanged by the two electrical switches 241a and 241b and established via connection path 242.

[0023] Communications between users across different offices, for example, communications between user 250a accommodated by electrical switch 241a in office 240 and user 350a accommodated by electrical switch 341a in office 340, are switched by electrical switch 241a and electrical switch 341a. That is, users 250a and 350a are connected via these two electrical switches and optical nodes 200 and 300. On paths 243a and 343a connecting the two electrical switches to the corresponding optical nodes, relatively large-capacity signals, for example, 100 Gbps, in which communications from multiple users are multiplexed, flow. In this way, communications between distant users across different offices have been carried out using optical nodes 200 and 300, which are a type of large-capacity transmission device.

[0024] In FIG. 4(a), users 250a and 250b are connected to electrical switches 241a and 241b via transmission lines 251a and 251b. The transmission lines 251a and 251b may be optical fibers or metal wiring such as ADSL. The electrical switches 241a and 241b in the central office 240 are shared by many users, and for conventional services requiring relatively low communication capacity, such as Internet connections, route switching using the electrical switches is sufficient. In addition, a connection 242 between the two electrical switches enables connections between local users under the optical node 200. Although switches such as WSS in the optical node 200 are responsible for switching the routes of large bundles of signals, such as WDM signals multiplexed from multiple user signals from the electrical switches, from the perspective of flexible operation and maintenance of the transmission network, they are basically used as transmission devices.

[0025] Figure 4(b) shows a usage pattern of optical nodes that is expected to emerge in the future as new services emerge. The communication capacity used by end users continues to increase year by year, and in the near future, it will be necessary to provide end-to-end services exceeding 100 Gbps per user. This new demand for communication capacity is comparable to the communication capacity of the multiplexed high-capacity signals flowing on the path 243a connecting the electrical switch to the optical node in the conventional usage pattern shown in Figure 4(a). In other words, a usage pattern is expected in which the electrical switches 241a and 241b are moved from the optical node side and installed in the building of a local user.

[0026] In this type of usage, there are two possible methods for connecting the electrical switch 241a of a local user 250a to the electrical switch 241b of another local user 250b, as shown in Figure 4(b). One method is to replace the conventional connection path 242 that connected the electrical switches 241a and 241b in Figure 4(a) with a new optical fiber transmission path between the users and the central office. However, this method requires that optical fibers be installed between all users accommodated in one central office 240. This type of connection is a configuration called a mesh connection, and is not practical because it requires (N-1) x N / 2 connections for the number of users N.

[0027] The other is a method of connecting via optical node 203. That is, this is a method of configuring the connection shown by dotted line 243 between transmission lines 251a and 251b such as optical fibers and optical node 203.

[0028] However, as shown in Figure 3(a), the current optical node 200 does not have a means for connecting the TPA 223a on the transmitting side, where a local user signal is added, and the TPA 223b on the receiving side, where a local user signal is dropped. The TPA's ports facing the path are connected only to the WSSs 216a and 216b, which are connected to each path. Therefore, the current optical node does not have a configuration for connecting the local ports of the TPAs ​​connected to local users. The optical node 200 does not have the functionality of a switching system connecting users accommodated in the central office 140, and therefore does not have a means for connecting local users end-to-end using optical signals to meet the new needs for ultra-high-speed, high-capacity communication services up to 100 Gbps. Therefore, the current optical node cannot support new services that require high-capacity, low-latency communication between end users, i.e., from one local user to another.

[0029] The optical node disclosed herein provides end-to-end optical connections between local users under the optical node. By incorporating optical switching functionality, which was not provided in optical nodes in conventional ROADM systems, it is possible to connect any end users under the optical node using only optical signals without using electrical switches. In the following description, the optical node will be described as an optical node in a multi-ring network, but please note that the optical node disclosed herein does not necessarily have paths to other optical nodes. That is, the optical node is characterized by the connection configuration between TPAs ​​to which local users are connected, and as long as it provides connections between local users, connection with other optical nodes is not required. Because the optical node disclosed herein is not directly related to connections between different optical nodes, it also has the aspect of an invention of a TPA, i.e., an optical switch, that does not include connection functionality with external optical nodes.

[0030] [Embodiment 1] First, as a first embodiment, an example of the configuration of an optical signal aggregation device that functions as an optical switch between local users, that is, a TPA, as an optical node realized by MCS will be described.

[0031] FIG. 5 is a diagram illustrating the configuration of an optical node capable of operating as a switch between local users according to the first embodiment. The optical node 400-1 includes an input optical fiber 211a, which is a path to an external optical node, and an output optical fiber 211b. For simplicity, only two paths are shown in FIG. 5, but the number of paths N may be greater. Switching between paths is performed by the input and output WSSs 216a and 216b, as described with reference to FIGS. 2 and 3. The ADD function for adding an optical signal from a user and the DROP function for dropping an optical signal to a user are also performed by a TPA consisting of an MCS 223a on the ADD side and an MCS 223b on the DROP side, as described with reference to FIGS. 2 and 3. FIG. 5 illustrates only two paths, and only two MCSs arranged in parallel on the ADD side and the DROP side.

[0032] The first difference from conventional optical nodes is the provision of a path 260 connecting the port on the route side of MCS223a and MCS223b. In conventional optical nodes, the TPA that aggregates transponders is used to add local user signals to the route side and drop signals from the route side to the local user side, but it cannot switch paths between local users. However, as explained in FIG. 4(b), there is an emerging need to realize ultra-high-speed, large-capacity communications between local users that exceed the communication capacity of electrical switches. In optical node 400-1, by providing connection path 260 connecting the port on the route side of MCS223a and MCS223b, connection at any optical level is possible between local ports.

[0033] Therefore, the present invention can be implemented as an optical node 400-1 comprising: a first optical signal concentrating device 223a having an input port 221a that receives an optical signal from a corresponding local user equipment 241 and outputs the optical signal to at least one of a plurality of output ports; and a second optical signal concentrating device 223b having an input port that receives the optical signal from the first optical signal concentrating device and forwards the optical signal to any output port 221b, and having a path 260 that connects only between the first optical signal concentrating device and the second optical signal concentrating device, and an optical connection is set from one local user equipment 241 to another local user equipment 242 via the path. Here, the optical signal concentrating device can be a transponder aggregation device (TPA) that aggregates transponders, and specifically can be configured with an MCS.

[0034] FIG. 5 shows an example in which the optical node 400-1 and the local user 250 are connected by two optical fibers, an upstream optical fiber 251a and a downstream optical fiber 252b. The local user 250 exclusively uses the high-capacity electrical switch 241 without sharing it with other local users. The electrical switch 241 and a transmitting Tx transponder 252a are located on the local user 250 side, allowing high-capacity services to be provided to one or more local users using, for example, time division multiplexing. The upstream optical fiber 251a is connected to the TPA on the ADD side, i.e., the local port of the MCS 223a. The downstream optical fiber 251b is connected to the TPA on the DROP side, i.e., the local port of the MCS 223b. One wavelength can be assigned to the local user 250 through the upstream optical fiber 251a and the downstream optical fiber 251b.

[0035] 5, the electrical switch 241 of the local user 250 is connected to the receiving Rx transponder 252b via the downstream optical fiber 251b, forming an upstream and downstream optical connection. The connection path 260 between the two MCSs allows the local user 250 to establish an optical connection with any other local user.

[0036] Here, a more specific configuration of the optical node 400-1 of the first embodiment will be illustrated. Input side WSS216a Number of ports: 1 x r Output WSS216b Number of ports: r x 1 Number of routes: N Tx side MCS223a Number of ports: p×q Rx side MCS223b Number of ports: q×p Number of MCS223a on the Tx side: L Number of MCS223b units on the Rx side: L Total number of Tx side local ports M:p×L Total number of Rx side local ports M:p×L Required number of ports on the MCS node side: q:N+L WSS required number of ports: N-1+L

[0037] The second difference between the configuration of the optical node 400-1 of the first embodiment described above and the optical node 200 of the prior art described in FIGS. 2 and 3 is the number of ports q required on the node side of the MCS. q=N+L formula (1)

[0038] In the optical node of the present disclosure, for connection paths 250 that interconnect L MCSs, the number of ports q on the node side of the MCS increases by the number L of MCSs, as shown in equation (1). Therefore, for connection paths 250 that interconnect MCSs, the MCS needs to have slightly more ports than the optical node configuration of the prior art.

[0039] Similar to the transponders 222a and 222b in the conventional optical node, the transponders 252a and 252b, even when located on the local user side, include wavelength tuning / wavelength assignment functions, allowing conversion to any other wavelength between the input and output of the transponder. However, the number of tunable wavelengths available in a transponder is generally limited. For this reason, the following relationship must be satisfied for the number p of local ports in the MCS: Number of variable wavelengths of transponder ≧ p Equation (2)

[0040] If the TPA configured by the MCS can satisfy the above formulas (1) and (2), a connection between local users can be made non-blocking from the ADD-side MCS to the DROP-side MCS. For the sake of explanation, FIG. 5 shows the signal flow in one direction, with the upstream optical fiber 251a and the downstream optical fiber 251b shown as if they were installed on separate routes, but they are treated as a single optical fiber pair. The Tx transponder 252a and the Rx transponder 252b are also configured as a single Tx / Rx transponder device. The electrical switches 241, which are shown as two separate units in FIG. 5, can also be configured as a single device. While the optical node 400-1 shown in FIG. 5 shows an example of a configuration in which two optical fibers are used to connect to a local user, a single optical fiber can also be used to connect to a local user.

[0041] Fig. 6 shows the configuration of another optical node that can operate as a switch between local users. Optical node 400-2 also has a connection path 260 that connects the port on the route side of MCS 223a and MCS 223b, allowing connection at any optical level between local ports. A building, for example, for local user 250 includes an electrical switch 241 and a transponder 252, and the configuration is the same as in Fig. 5 except for the display. The difference from optical node 400-1 in Fig. 5 is that a single optical fiber 251 connects to local user 250.

[0042] The optical node 400-2 in Figure 6 uses two different wavelengths to transmit upstream and downstream signals over a single optical fiber 251. To use the different wavelengths, wavelength-tunable transponders 222a and 222b are provided at the local ports of MCSs 223a and 223b. A multiplexer / demultiplexer 253 on the local side of the wavelength conversion transponder multiplexes two waves (upstream and downstream) of different wavelengths and transmits them over a single optical fiber 251. In this way, the only difference from the configuration in Figure 5 is the form of optical transmission between the local user and the optical node 400-2; the local user is connected to the optical node by an optical connection. The optical node 400-2 also has a connection path 260 connecting the port on the route side of MCSs 223a and 223b, allowing connections at any optical level between local ports.

[0043] In the two configuration examples in the first embodiment described above, the connection between local users is realized by TPA using MCS, but TPA can also be realized by other methods.

[0044] [Embodiment 2] Fig. 7 is a diagram showing the configuration of an optical node capable of operating as a switch between local users in embodiment 2. In order to show the differences from the optical node in embodiment 1, the optical node 500 in Fig. 7 shows only the optical node, and does not show the connection to the local users. Therefore, it is optically connected to the local users using the connection method in Fig. 5 or Fig. 6.

[0045] The optical node 500 differs from the optical node 400-1 of the first embodiment in that the TPA, which connects local users, is configured with a WSS. The optical node 500 replaces the MCS 223a on the ADD side and the MCS 223b on the DROP side in the optical node 400-1 of FIG. 5 with a WSS 225a with a p×q configuration and a WSS 225b with a q×p configuration. In FIG. 7, the WSS 216a with a 1×r configuration and the WSS 216b with an r×1 configuration are already used for switching between paths. By combining WSSs with different configurations, it is possible to achieve the same path switching and optical switching functions as the MCS 223a and MCS 223b described above. The WSS with a p×q configuration has zero theoretical loss. Because the MCS splits the signal, a theoretical splitting loss of 10×log(1 / p) (unit: dB) occurs, where p is the number of splits. For example, splitting the input into 8 signals results in a theoretical output loss of 9 dB, while splitting into 16 signals results in a theoretical output loss of 12 dB. On the other hand, p×qWSS is lossless in principle, which is more advantageous than realizing TPA by MCS.

[0046] In the optical node 500 of the second embodiment, by using a WSS as a TPA, even if the number of local ports p is increased, optical signal loss does not increase, and it is possible to increase the scale of the TPA. In other words, it is possible to increase the total number of local ports M. In the configuration of the second embodiment in FIG. 7, the wavelength-tunable transponders 222a and 222b are provided on the local port side of the MCS 223a and MCS 223b. Therefore, the optical connection from the optical node 500 to one local user can be implemented by a single optical fiber, as in the configuration shown in FIG. 6. If two optical fibers are used, as in the configuration shown in FIG. 5, the wavelength-tunable transponders 222a and 222b on the optical node side may be unnecessary.

[0047] By using WSS, it is possible to effectively deal with an increase in the number of local ports in a TPA, but it is also possible to take an approach that deals with branch loss while maintaining the configuration using MCS.

[0048] [Embodiment 3] Fig. 8 is a diagram showing the configuration of an optical node capable of operating as a switch between local users according to the third embodiment. In the optical node 600, the TPA that connects between local users is configured by MCS, similar to the optical node 400-2 of the first embodiment shown in Fig. 6. Fig. 8 also does not show the connection to the local users, and optical connection to the local users is made by the connection method shown in Fig. 5 or 6.

[0049] 6 in that the optical node 600 includes an optical amplifier 226a and a wavelength-tunable optical bandpass filter (Optical BPF) 227a between the transponder 222a and the MCS 223a on the ADD side, and an optical amplifier 226b and wavelength-tunable OBPFs 227b and 228b between the MCS 223b on the DROP side and the transponder 222b.

[0050] The optical amplifiers 226a and 226b can be inexpensive single-channel optical amplifiers, and compensate for the fundamental loss that occurs in the MCS. The wavelength-tunable optical beamforming filters 227a and 227b can remove background noise from local users' optical transmitters and optical amplifiers, and suppress the accumulation of background noise while the signal passes through the two MCSs 223a and 223b of the TPA.

[0051] As shown in Figures 3(b) and (c), MCSs 223a and 223b use optical couplers 231 internally, and the output light may contain signals of multiple wavelengths. If the receiver of transponder 222b on the receiving (DROP) side has a wavelength selection function, such as a coherent demodulator, it can receive only the signal of the relevant wavelength even if multiple wavelengths are input to the receiver. On the other hand, if the receiver does not have a wavelength selection function, such as a direct receiver, the wavelength-tunable OBPF 227b located downstream of optical amplifier 226b also performs this wavelength selection function. Also, if optical amplifier 226b is a single-channel amplifier, the wavelength-tunable OBPF 228b located upstream performs the function of selecting only the relevant signal. These wavelength-tunable OBPFs 228b and 227b may be provided as needed.

[0052] In any of the optical nodes of Embodiments 1 to 3, by providing a path 260 connecting the local ports of the TPAs, it is possible to realize an ultra-high-speed, high-capacity optical connection exceeding the communication capacity of an electrical switch, only via the TPAs ​​of the optical nodes, without using a path in the core network. The optical nodes of the above-described embodiments can be expanded in accordance with an increase in the communication capacity handled by the optical nodes. It is possible to add TPAs ​​in opposing MCS units 261 shown in FIG. 5 or opposing WSS units 262 shown in FIG. 7, and it is not necessary to provide L MCSs and WSSs from the start of service. Therefore, capital investment according to the demand for ultra-high-speed, high-capacity communication services between local users is possible (pay-as-you-grow).

[0053] In the optical nodes of the first to third embodiments, a local user's electrical switch can be connected to other local users by optical signals using the optical switching function of the TPA. Although this optical connection route passes through several transponders along the way, the entire route is essentially optical. Furthermore, between local users, a fixed MCS or WSS of the TPA is set as the route for providing a predetermined service within a certain period of time. Therefore, rather than using the packet switching function of the electrical switch, the TPA operates as a circuit switch.

[0054] In the above-described embodiment, the first optical signal aggregation device (TPA) has a connection path to another optical node in the ring network, and the second optical signal aggregation device (TPA) has a connection path to another optical node in the ring network, and they are described as optical nodes in a ROADM system. The optical nodes disclosed herein do not necessarily need to be connected to other optical nodes, i.e., to a multi-ring network or a core network. The above-described embodiment is based on the configuration of an existing TPA in an optical node in a ROADM system, and connection to a core network is not a necessary condition, as in the case of the use example in a data center described below. Conventional optical nodes route WDM signals, which are multiplexed signals from multiple users, between other optical nodes as large bundles of, for example, 400 Gbps. In this case, the optical node simply switches signals at a very large granularity and can be regarded as a transmission device from the perspective of the local user. As described in FIG. 4, the optical node was not involved in switching between local users.

[0055] On the other hand, the optical node disclosed herein can switch signals from an electrical switch at a local user to other local users by utilizing the TPA configuration of an existing optical node. It can also be understood that the optical node, which previously only played the role of a transmission device, is now also given the role of a switch for local users. The following embodiment shows a configuration as an optical switch that does not involve connection to a core network.

[0056] [Embodiment 4] 9 is a diagram illustrating the configuration of an optical switch connecting local users according to the fourth embodiment. The optical switch 700 in FIG. 9 is the optical node 400-1 in FIG. 5 without the WSS for path switching, and includes only the MCSs constituting the TPAs. The optical switch 700 includes four MCSs 223a arranged in parallel as Tx-side TPAs ​​221a to which signals from local users are input, and four MCSs 223b arranged in parallel as Rx-side TPAs ​​221b to which signals to local users are output. Transponders 222a and 222b are connected to the local port sides of each MCS. Therefore, in the optical switch 700, the first optical signal concentrating apparatus (TPA) and the second optical signal concentrating apparatus (TPA) are not connected to other optical nodes in the ring network, and operate as an optical switch between multiple local user equipment.

[0057] Since the optical switch 700 does not include a WSS that was responsible for connecting to the directional path side, there is naturally no connection between the MCSs 223a and 223b and the core network. On the other hand, local user signals can be optically connected between any combination of local users via connection paths between the four MCSs 223a and the four MCSs 223b. In this case, optical connection 243 between local users shown in Figure 4(b) can be realized. The optical switch 700 in Figure 9 can also be placed in an environment where the optical node of the ROADM system shown in Figure 1 is not connected to other optical nodes and is not connected to a multi-ring network.

[0058] For example, the optical switch 700 can be used in a data center to connect electrical switches of local users who provide or use ultra-high-speed, large-capacity communication services. The optical switch 700 is connected to transponders that interface between the local user's signals (optical signals, electrical signals) and larger-format optical signals. The optical switch 700 is a transponder aggregation device (TPA) that aggregates transponders. If the definition of an optical node is considered to be a node (assembly point) connecting communication devices via transmission lines / optical fibers, the optical switch 700 can also be considered an optical node.

[0059] As explained in detail above, the optical nodes and optical switches disclosed herein make it possible to adapt optical communication networks to new services that require high-capacity, low-latency connections between end users. [Industrial Applicability]

[0060] The present invention can be used in optical communications.

Claims

1. An optical node, a plurality of first optical signal aggregation devices each having an input port for receiving an optical signal from a corresponding local user equipment external to the optical node, and for outputting the optical signal to at least one of a plurality of output ports; a plurality of second optical signal aggregation devices each having an input port for receiving the optical signal from the first optical signal aggregation device and transferring the optical signal to an arbitrary output port; Equipped with Each of the plurality of first optical signal aggregation devices has a route connecting only with each of the plurality of second optical signal aggregation devices, and an optical connection is established from one local user equipment to another local user equipment via the route. Optical node.

2. the local user equipment transmits or receives optical signals via a transponder that interfaces between optical and electrical signals; The system includes a plurality of first transponder aggregation devices (TPAs) that are multicast switches (MCSs), and a plurality of second TPAs ​​that are MCSs having a symmetrical input / output relationship with the MCSs, or The system includes a plurality of first TPAs ​​that are wavelength selective switches (WSSs) and a plurality of second TPAs ​​that are WSSs having a symmetrical configuration in terms of input / output relationship with the WSSs. The optical node of claim 1 .

3. the first TPA has p input ports and q output ports; the second TPA has q input ports and p output ports; The number of variable wavelengths of the transponder is equal to or greater than p. The optical node of claim 2 .

4. an optical amplifier and a tunable BPF between the transponder and the first TPA; an optical amplifier and a tunable BPF between the second TPA and the transponder; The optical node of claim 2 .

5. the plurality of first optical-signal aggregation devices have connection paths to optical nodes other than the optical node in the ring network; the plurality of second optical-signal aggregation devices have connection paths from optical nodes other than the optical node in the ring network; 10. The optical node of claim 1, wherein the optical node is an optical node of a Re-configurable Optical Add Drop Multiplexing (ROADM) system.

6. the plurality of first optical signal aggregation devices and the plurality of second optical signal aggregation devices are not connected to other optical nodes; Acts as an optical switch between multiple local user equipment The optical node of claim 1 .

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