JP5081726B2 - Optical transmission system - Google Patents

Description

  The present invention relates to an optical transmission system, and more particularly to an optical transmission that is applied to a communication network using a wavelength division multiplexing system and realizes a network in which optical transmission paths are duplicated or a network in which path control is performed according to wavelengths. About the system.

  Conventionally, an optical transmission line or a transmission apparatus has a duplex configuration of an active system and a standby system, or an N + 1 configuration having one standby system for a plurality of active systems, and the active system is changed to a standby system. Switching temporarily (hereinafter referred to as a protection function) is performed. This is because in an optical network in which multiple nodes are connected to each other, when an optical transmission path failure between nodes, a failure of the node itself, a new node is added, or an existing node is inserted or removed, communication is interrupted. This is because it is necessary to prevent.

  In the point-to-point network, the active system and the standby system are switched in the transmission apparatuses at the nodes at both ends. In point-multipoint networks, UPSR (Unidirectional Path Switched Ring) and BLSR (Bidirectional Line Switched Ring) are known as protection functions (see, for example, Non-Patent Document 1). UPSR and BLSR are protection functions provided in an SDH / SONET ring network based on a wavelength division multiplexing (WDM) transmission method.

  In a conventional optical transmission system, not only a parent node but also a child node requires an active optical switch and an advanced control system for switching between an active system and a standby system. For this reason, there has been a problem in miniaturization and low price of the transmission apparatus constituting the node. In order to solve this problem, a configuration is known in which an optical switch is used only for a parent node and a child node is connected to an active system and a standby system via a power splitter (Patent Document 1).

JP 2005-111552 A ITU-T, Recommendation G.841, Types and characteristics of SDH network protection architecture.

  However, in order for an optical transmission system to be applied from the backbone system to the access system region of a large-capacity transmission line such as a metro ring or a relay section, further downsizing and cost reduction of the transmission apparatus are required. In the access system, not only duplex transmission lines but also flexibility in network construction is required.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical transmission system that is easy to construct a network and excellent in economic efficiency.

In order to achieve such an object, the present invention is characterized in that the invention described in claim 1 includes two connections respectively connected to one end of the transmission line of the first system and one end of the transmission line of the second system. a parent node having a port, and a plurality of branch portions, which are cascade-connected to the transmission line of the first system and the second system, and a plurality of child nodes provided corresponding to each of the plurality of branch portions the provided, each of the plurality of child nodes which is communicably connected to an optical transmission system and the parent node through the corresponding branch portion, each branch portion is connected to a child node corresponding to the branch portion a port that, in mutually different first and second wavelength bands do not overlap between each of the branch portion, input and output optical signals with the respective transmission paths of the first system and the second system It has ports that is possible, the branch portions, the first In the wavelength band through a transmission path of the first system was only capable of communicating with the child node corresponding to the parent node and the branch portion, outside the first wavelength band, said first through a transmission line of the system and can communicate with with one of the child node corresponding to the parent node and the other branch portion, so as to be unable to communicate the with the child node corresponding to the branch portion configured, each branch portion is in said second wavelength band, only can communicate with the child node corresponding to the parent node and the branch portion through the transmission line of the second system, the wherein the second wavelength band, and can communicate with with one of the child node corresponding to the parent node and the other branch portion via a transmission path of the second system, corresponding to the branch portion between the child node is further configured to be unable to communicate, Kioya node and each child node, one of the transmission lines of the first system and the second system by setting one of the first and second wavelength band optical signals used for communication with each other It is configured to be able to communicate through the network.

The invention of claim 2 is an optical transmission system according to claim 1, wherein the first system and the second system, and characterized in that it is constituted by a transmission line of the bus type, respectively To do.

The invention according to claim 3 is the optical transmission system according to claim 1, wherein the first system and the second system are each configured by a ring-type transmission line, and the parent node is , And further comprising two ports respectively connected to the other end of the transmission line of the first system and the other end of the transmission line of the second system .

According to a fourth aspect of the present invention, there is provided the optical transmission system according to the first aspect of the present invention, which is connected to one end of the third system transmission path and one end of the fourth system transmission path, respectively. And further comprising another parent node having one port , and each branch section is cascade-connected to any two transmission paths of the first to fourth system transmission paths, and at least one branch section is the a first system transmission path and the second system of the transmission path either a transmission path, to one transmission line of any transmission line of the third transmission line and the fourth system of the system connected in cascade are provided corresponding to the branch portion, the child node connected to the branch unit is characterized in that both of the parent node is capable of communicating.

The invention described in Claim 5, a parent node having two ports connected to both ends of a heart of the ring-shaped transmission path, and a plurality of branch portions, which are cascade-connected to the transmission line, the A plurality of child nodes provided corresponding to each of the plurality of branch units, each of the plurality of child nodes is an optical transmission system that is communicably connected to the parent node via the corresponding branch unit Each branch unit is a port connected to a child node corresponding to the branch unit, and the first and second wavelength bands that do not overlap between the branch units are different from each other in the transmission path. A port capable of inputting and outputting an optical signal between a first system in which the ascending is clockwise and the descending is counterclockwise, and a second system in which the ascending is counterclockwise and the descending is clockwise . Each branching section has the first wavelength band In the region, through said transmission path only can communicate with the child node corresponding to the parent node and the branch portion, outside the first wavelength band by said first system, said first system so that via said transmission path communicable with with one of the child node corresponding to the parent node and the other branch portion, impossible communications between the child node corresponding to the branch unit by configured, each branch portion, within the second wavelength band, only to allow communication with the child node corresponding to said parent node and the branch portion through the transmission line by the second system the in the second wavelength band, and can communicate with with one of the child node corresponding to said parent node and the other branch portion through the transmission line by a second system, the branch portion the I impossible communication between the corresponding child node Further configured to, the parent node and each child node of the first system and the second system by setting one of the first and second wavelength band optical signals used for communication with each other It is configured to be able to communicate with either one.

The invention of claim 6 is an optical transmission system according to any one of claims 1 to 4, the optical branching unit transmits light signals to the cross side in the first wavelength band is allowed, a first 2 × 2 coupler for transmitting the through side otherwise, the optical signal is transmitted through the second cross side in the wavelength band of the second 2 × for transmitting to the through side in other cases A two-coupler, wherein one output of the first 2 × 2 coupler is connected to one input of the second 2 × 2 coupler.

Further, the invention according to claim 7, an optical transmission system according to claim 5, the optical branching section, the optical signal is transmitted through the first through-side in a wavelength band of, otherwise the a first 2 × 2 coupler for transmitting to the cross side, the optical signal is transmitted through the second through-side in the wavelength band, and a second 2 × 2 coupler for transmitting to the cross side in other cases And one output of the first 2 × 2 coupler is connected to one input of the second 2 × 2 coupler.

  According to the present invention, it is possible to switch between the active system and the standby system by providing a simple passive wavelength filter at the branch of the network and changing the communication wavelengths of the nodes on both sides. Therefore, an expensive optical switch is not required for either the parent node or the child node, and the transmission apparatus can be further reduced in size and price. In addition, since no power splitter is used in the branching section, optical loss in the branching section is small, and the number of optical amplifiers in the system can be reduced. Furthermore, a tree-type network composed of a plurality of nodes can be configured based on the same principle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration example of an optical transmission system according to an embodiment of the present invention. This optical transmission system 100 has a bus-type network configuration having two transmission lines of an active system and a standby system. As shown in the figure, in this optical transmission system 100, one parent node 102 and a plurality of child nodes 104-1 to 104-n are connected to the working transmission line 110 via a plurality of branch sections 106-1 to 106-n. It is connected to the standby transmission line 120.

  First, the working system will be described. The wavelength-multiplexed downstream optical signal from the parent node 102 enters the port P1 of the branching unit 106-1, and only the wavelength components allocated to the child node 104-1 are two couplers 132-1 and 134-1. To the port P5 and reach the child node 104-1. At this time, the signal in the wavelength band assigned to other than the child node 104-1 is guided to the port 4 and propagates to the next branching unit 106-2. The upstream signal from the child node 104-1 enters from the port P 5, is guided to the port P 1 via the two couplers 132-1 and 134-1, and reaches the parent node 102. For the other child nodes 104-2 to n, specific wavelength components are assigned to the downstream and upstream signals, and communication with the parent node 102 is possible via the branching units 106-2 to 106-n.

  Next, the operation of the branching section will be described in detail with reference to FIG. FIG. 2 shows the wavelength coupling characteristics of the two couplers in the branching section. Two couplers SP1-k and SP2-k are used for the k-th branch #k (k is an integer of 1 to n). In the figure, when the coupling ratio on the vertical axis is 0, it means that all power is transmitted to the through side of the coupler, and when the coupling ratio is 1, it means that all power is transmitted to the cross side of the coupler. Yes.

  The coupler SP1-k has a coupling characteristic with a center wavelength λk and a width Δλk, and the coupler SP2-k is coupled with a center wavelength λ′k and a width Δλ′k in a wavelength band adjacent to the coupler SP1-k. It has characteristics. For the k-th child node #k, a wavelength within the range of the width Δλk is assigned to the active system in advance, such as λdnk or λupk. On the other hand, a wavelength within the range of the width Δλ′k, such as λ′dnk and λ′upk, is assigned to the standby system.

  In the case of the active system, the downstream optical signal λdnk within Δλk is assigned to the child node #k. When this downstream optical signal enters the port P1 of the branching section #k, the downstream optical signal is guided to the port P5 through the cross side of the coupler SP1-k and the through side of the coupler SP2-k. On the other hand, when an optical signal not within Δλk is incident on the port P1 of the branching section #k, it is guided to the port P4 through the through side of the coupling SP1-k and propagates to other nodes.

  On the other hand, the upstream optical signal λupk within Δλk is assigned to the child node #k. When the upstream signal enters the port P5 of the branching section #k, the upstream signal is guided to the port P1 through the through side of the coupler SP2-k and the cross side of the coupler SP1-k. Now, when the upstream optical signal λupk is changed to λ′upk by temperature control or the like at the child node #k, this optical signal is guided from the port P5 to the port P3 through the cross side of the coupler SP2-k. It is burned. In this way, by changing the wavelength of the upstream optical signal on the child node side, the upstream optical signal transmission path can be switched from the active system to the standby system.

  In the case of the standby system, the downstream optical signal λ′dnk in Δλ′k is assigned to the child node #k. When this downstream optical signal enters the port P3 of the branching section #k, it passes through the cross side of the coupler SP2-k and is guided to the port P5. On the other hand, when an optical signal not within Δλ′k is incident on the port P3 of the branching section #k, it is guided to the port P6 through the through side of the coupling SP2-k and propagates to other nodes. The wavelength change of the downstream optical signal can be realized at the parent node by temperature control or the like, and the active system and the standby system may be selected for the two wavelengths λdnk and λ′dnk. That is, the parent node outputs the data to one of the working side port and the standby side port according to the wavelength.

  By setting the band (Δλk and Δλ′k) of the wavelength coupling characteristics in FIG. 2 so that they do not overlap at each child node, communication is performed exclusively between all child nodes and the parent node, In addition, switching of transmission lines can be realized by wavelength temperature control or the like. By switching between such transmission paths, when one transmission path (for example, the active system) fails, simultaneous switching to the other transmission path (for example, the standby system) becomes possible. Further, it is possible to arbitrarily select one of the two transmission paths that is convenient for each child node. Furthermore, in principle, both wavelengths can be used simultaneously, and two transmission paths can be used together to increase the transmission capacity. However, in this case, it is necessary to provide two light sources in the parent node and the child node. The characteristic shown in FIG. 2 is an example, and the characteristic of the coupler may be reversed as in the branching part shown in FIG. That is, in FIG. 2, when the coupling ratio on the vertical axis is 0, all the power is transmitted to the cross side of the coupler, and when the coupling ratio is 1, the total power is transmitted to the through side of the coupler. Bifurcations can also be used.

  FIG. 3 shows a configuration example of an optical transmission system according to another embodiment of the present invention. This optical transmission system 300 has a ring type network configuration having two transmission lines of an active system and a standby system. As shown in the figure, in this optical transmission system 300, one parent node 302 and a plurality of child nodes 304-1 to 30-n are connected to the active transmission line 310 via a plurality of branch sections 306-1 to 306-1-n. It is connected to the standby transmission line 320.

  The configuration of the network in FIG. 3 differs from the configuration in FIG. 1 in the way of wiring between the ports of the branch units 306-1 to 306-1. Specifically, the port P3 of each branch unit is connected not to the parent node 302 but to the port P6 of the next branch unit. Thereby, a double ring transmission line is formed. In this network configuration, for the active system, the downstream optical signal propagates clockwise and the upstream optical signal propagates counterclockwise. On the other hand, for the standby system, the downstream optical signal propagates counterclockwise and the upstream optical signal propagates clockwise. By configuring in this way, even if a failure occurs in both the active system and the standby system, the parent node and the child node are switched to one of the transmission paths in either the active system or the standby system. The communication can be continuously maintained while avoiding the location where the error occurs.

  FIG. 4 shows a configuration example of an optical transmission system according to still another embodiment of the present invention. The optical transmission system 400 has a ring type network configuration having a single transmission line for the active system and the standby system. As shown in the figure, in this optical transmission system 400, one parent node 402 and a plurality of child nodes 404-1 to 404-n are used together in the active system and the standby system via a plurality of branch sections 406-1 to 406-1. Connected to the transmission line 310.

  In FIG. 4, the configuration of the branching portion is different from that in FIGS. Specifically, the branch sections 406-1 to 406-n in FIG. 4 are configured such that the ports P2 and P3 of the branch sections in FIGS. 1 and 3 are directly connected internally. In FIG. 4, the characteristics of the coupler are different from those in FIGS. 1 and 3. Specifically, the couplers ISP1-k and ISP2-k (k is an integer of 1 to n) in FIG. 4 have characteristics inverted from the wavelength coupling characteristics of the couplers SP1-k and SP2-k shown in FIG. belongs to. That is, the coupler ISP1-k has a coupling rate of 0 in the interval of Δλk and a coupling rate of 1 outside the zone. The coupler ISP2-k has a coupling rate of 0 in the interval Δλ′k and a coupling rate of 1 outside the zone.

  In this network configuration, for the working system, the downstream optical signal propagates clockwise from P1 to P4 at the branching unit, and the upstream optical signal propagates counterclockwise from P4 to P1 at the branching unit. For the standby system, the downstream optical signal propagates counterclockwise from P6 to P4 at the branch, and the upstream optical signal propagates clockwise from P4 to P6 at the branch. With this configuration, as in the case of FIG. 3, the ring propagation direction can be switched between the active system and the standby system, and even when one connection disconnection occurs in the transmission line, the ring is transmitted via the transmission line in the opposite direction. Communication between the parent node and the child node. In this way, even if a single-core transmission line is used, the active and standby networks can be configured, which is more economical than the case of two-core.

  FIG. 5 shows a configuration example of functions inside the node in the above embodiment. FIG. 5A is a configuration example of a child node, and FIG. 5B is a configuration of a parent node.

  The child node 510 receives a downstream optical signal and converts it into an electrical signal, a transmission unit 514 that receives a transmission signal and converts it into an upstream optical signal, and combines the downstream optical signal and upstream optical signal according to wavelength. And a wavelength multiplexer / demultiplexer 516 for demultiplexing.

  The downstream optical signal from the parent node is demultiplexed by the wavelength multiplexer / demultiplexer 516 and enters the receiving unit 512. The downstream optical signal is converted into an electrical signal by a receiving unit 512 configured with a photodiode (PD) or the like and output.

  On the other hand, a transmission signal from the child node 510 is input to a transmission unit 514 configured by a laser diode (LD) or the like and converted into an upstream optical signal. This upstream optical signal is multiplexed by the wavelength multiplexer / demultiplexer 516 and sent to the transmission path. At this time, the oscillation wavelength of the transmission unit 514 can be changed by giving a temperature change or the like to the LD by a control signal. As a result, it is possible to switch between the active system and the standby system according to the characteristics of the branch section described in FIG.

  The parent node 520 receives a plurality of upstream optical signals having different wavelengths and converts them to a plurality of electrical signals, and receives a plurality of transmission signals and converts them to a plurality of downstream optical signals having different wavelengths. Transmitter 524, wavelength multiplexer / demultiplexer 526 that multiplexes and demultiplexes a plurality of upstream optical signals and a plurality of downstream optical signals, and a wavelength that multiplexes a plurality of pairs of upstream optical signals and downstream optical signals in the active system A multiplexer 528 and a wavelength multiplexer 530 that wavelength-multiplexes a plurality of pairs of upstream and downstream optical signals are provided.

  A plurality of upstream optical signals having different wavelengths from a plurality of child nodes are demultiplexed by the active wavelength multiplexer 528 or the standby wavelength multiplexer 530. Each of the demultiplexed upstream optical signals is route-selected by the wavelength multiplexer / demultiplexer 526 and enters the reception unit 522. The plurality of upstream optical signals having different wavelengths are converted into electrical signals by the receiving unit 522 configured by a PD array or the like and output. By using the wavelength multiplexer / demultiplexer 526 in this manner, the receiving unit 522 and the transmitting unit 524 can be shared with the active system and the standby system. Note that the wavelength multiplexer / demultiplexer 526 may not be used, and a separate reception unit and transmission unit may be provided for each of the active system and the standby system.

  On the other hand, a plurality of transmission signals from the parent node 520 are input to a transmission unit 524 configured by an LD array or the like, and converted into a plurality of downstream optical signals, respectively. Here, the oscillation wavelength of each LD is set so that the wavelength bands do not overlap as described with reference to FIG. Then, depending on the oscillation wavelength of the LD array, the wavelength multiplexer / demultiplexer 526 selects a path to the wavelength multiplexer / demultiplexer 528, 530 of either the active system or the standby system. In the setting of the working system, the plurality of downstream optical signals are route-selected by the wavelength multiplexer / demultiplexer 526, enter the working wavelength multiplexer 528, and are wavelength-multiplexed and then sent to the working transmission line. The Further, in the standby system setting, the plurality of downstream optical signals are route-selected by the wavelength multiplexer / demultiplexer 526, are incident on the standby wavelength multiplexer 530, and are wavelength-multiplexed and then transmitted to the standby transmission line. Sent out. At this time, the oscillation wavelength of the transmission unit 524 can be changed by giving a temperature change or the like to the LD array by a control signal. As a result, the settings of the active system and the standby system can be changed, and the active system and the standby system can be switched according to the characteristics of the branching section described with reference to FIG. It should be noted that control such as temperature change may be performed for each LD, not for the entire LD array.

  Next, the configuration and operation of the optical transmission system according to the present invention will be described with reference to FIG. The optical transmission system 600 includes two parent nodes 602-1 and 602-2, seven child nodes 604-1 to 604-7, and seven branching units 606-1 to 606-7.

  First, considering a downstream route, the parent node 602-1 is communicably connected to the child nodes 604-1, 604-2, 604-3, and 604-7. In the first system, the parent node 602-1 can communicate with only the child node 604-1 therein through the optical transmission path 610. In the second system, the parent node 602-1 is connected to other child nodes 604-2, 604-3, and 604-7 according to the wavelength settings of the branching units 606-1, 606-2, and 606-3. Communication becomes possible.

  At this time, the optical signal wavelength group of another parent node 602-2 is set so as not to partially overlap the optical signal wavelength group of the parent node 602-1 so that the same wavelength is not mixed on the transmission path. Therefore, when the child node 604-2 receives the optical signal from the parent node 602-1, the wavelength of the optical signal from the parent node 602-2 is changed to the child node 604-2 in the branching unit 606-2. Will not reach. Thus, if the optical transmission system is configured with no overlapping wavelengths, each child node can independently receive the downstream optical signal of any parent node.

  In the upstream path, as shown in FIG. 2, when the upstream optical signal having the same wavelength band as that of the downstream optical signal is used, the child node can communicate with the target parent node by passing through the branching unit. For example, among the wavelength bands received from the child node 604-7 to the parent node 602-1 and allocated in advance to the child node 604-7, the uplink band belonging to the wavelength band of the second system of the parent node 602-1 If a wavelength is used, it will pass through the branch parts 606-7, 606-3, 606-2, and 606-1 on the way, and will reach | attain the parent node 602-1. When the upstream wavelength belonging to the wavelength band of the first system of the parent node 602-2, which is the other wavelength band allocated in advance, is used, the branching units 606-7, 606-6, and 606-5 in the middle are used. Pass through and reach the parent node 602-2.

  In this way, by assigning the wavelength of the band corresponding to the first and second systems of each parent node to each child node, bidirectional communication becomes possible, and the wavelength is changed between the parent node and the child node. Thus, it is possible not only to make the transmission path redundant, but also to switch routes in various network forms and switch parent nodes for communication.

  While the present invention has been described with respect to several specific embodiments, the embodiments described herein are merely illustrative in view of the many possible embodiments to which the principles of the present invention can be applied. It is not intended to limit the scope of the invention. For example, in the above embodiment, separate wavelengths are assigned to the upstream and downstream optical signals, but the present invention assigns the same wavelength to the upstream and downstream optical signals and performs bidirectional communication in time division. Is also applicable. As described above, the configuration and details of the embodiment exemplified here can be changed without departing from the gist of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

It is a figure which shows the structural example of the optical transmission system by one Embodiment of this invention. It is a figure which shows the wavelength coupling characteristic in two couplers of the branch part which can be used for the optical transmission system by this invention. It is a figure which shows the structural example of the optical transmission system by other embodiment of this invention. It is a figure which shows the structural example of the optical transmission system by further another embodiment of this invention. FIG. 5A is a diagram illustrating a configuration example of a node that can be used in the optical transmission system according to the present invention, FIG. 5A is a configuration example of a child node, and FIG. 5B is a configuration example of a parent node. is there. It is a figure for demonstrating the structure and operation | movement of the optical transmission system by this invention.

Explanation of symbols

100, 300, 400, 600 Optical transmission system 102, 302, 402, 602-1, 602-2 Parent node 104-1 to n, 304-1 to n, 404-1 to n, 604-1 to 7 Child node 106-1 to n, 306-1 to n, 406-1 to n, 606-1 to 7 branching unit 110, 120, 310, 320, 410, 610, 620, 630, 640 transmission path 510 child node 512 receiving unit 514 Transmitter 516 Wavelength multiplexer / demultiplexer 520 Parent node 522 Receiver 524 Transmitter 526 Wavelength multiplexer / demultiplexer 528, 530 Wavelength multiplexer SP1-1 to n, SP2-1 to n, ISP1 to n, ISP2-1 to n coupler P1-P6 port

Claims (4)

A parent node having a bus type first system transmission path end and the bus type second system the two ports respectively connected to one end of a transmission path of the of the first system and the second system A plurality of branch portions connected in cascade to the transmission path, and a plurality of child nodes provided corresponding to each of the plurality of branch portions, each of the plurality of child nodes via a corresponding branch portion An optical transmission system communicably connected to the parent node,
Each branch part is connected to the first and second couplers and the parent node or branch part adjacent in the upstream direction via the transmission lines of the first system and the second system, respectively. A first port and a second port, a third port connected to a child node corresponding to the branching unit, a branching unit adjacent in the downstream direction, and the transmission lines of the first system and the second system, respectively. A fourth port and a fifth port connected to each other ,
In each branching unit, among the optical signals input from the first port by the first and second couplers, an optical signal in a first wavelength band assigned to the corresponding child node is transmitted to the first branching unit . 3, an optical signal outside the first wavelength band is guided to the fourth port, and the optical signal input from the second port is assigned to the corresponding child node. said second optical signal in the wavelength band is guided to the third port, said second optical signal outside the wavelength band consists as guided to the fifth port,
The first and second wavelength bands assigned to each child node are different from each other and set so as not to overlap each other between the child nodes;
The parent node and each child node set the first system and the second system by setting an optical signal used for communication to one of the first and second wavelength bands assigned to the child node. is configured capable of communicating via any of the transmission path,
The first coupler transmits an optical signal to the cross side within the first wavelength band assigned to the child node corresponding to the branching unit, and transmits the optical signal to the through side otherwise. And
The second coupler transmits an optical signal to the cross side within the second wavelength band assigned to the child node corresponding to the branching unit, and transmits to the through side otherwise. And
The first port is connected to a first input / output end of the first coupler;
The second port is connected to a first input / output terminal of the second coupler;
The fourth port is connected to a second input / output terminal which is a through side with respect to the first input / output terminal of the first coupler;
The fifth port is connected to a second input / output terminal which is a through side with respect to the first input / output terminal of the second coupler;
The third port is connected to a third input / output terminal that is crossed with respect to the first input / output terminal of the second coupler;
A third input / output terminal that is crossed with respect to the first input / output terminal of the first coupler is a fourth side that is a through side with respect to the third input / output terminal of the second coupler. An optical transmission system connected to the input / output terminal of A parent node having a ring-shaped first system two ports connected to both ends of the transmission line on both ends of the transmission path of the second system of respective two connected ports and the ring of the first Each of the plurality of branch nodes, and a plurality of branch nodes connected in cascade to the transmission lines of the second system and the second system, and a plurality of child nodes provided corresponding to each of the plurality of branch sections, Is an optical transmission system communicably connected to the parent node via a corresponding branching unit,
Each branch section is connected to the first and second couplers and the parent node or branch section adjacent in the counterclockwise direction via the transmission lines of the first system and the second system, respectively. A first port and a fifth port; a third port connected to a child node corresponding to the branch; the parent node or branch adjacent to the clockwise direction; and the first system and the second, respectively. A fourth port and a second port connected via a transmission line of
In each branching unit, among the optical signals input from the first port by the first and second couplers, an optical signal in a first wavelength band assigned to the corresponding child node is transmitted to the first branching unit . 3, an optical signal outside the first wavelength band is guided to the fourth port, and the optical signal input from the second port is assigned to the corresponding child node. said second optical signal in the wavelength band is guided to the third port, said second optical signal outside the wavelength band consists as directed to the fifth port of
The first and second wavelength bands assigned to each child node are different from each other and set so as not to overlap each other between the child nodes;
The parent node and each child node set the first system and the second system by setting an optical signal used for communication to one of the first and second wavelength bands assigned to the child node. is configured capable of communicating via any of the transmission path,
The first coupler transmits an optical signal to the cross side within the first wavelength band assigned to the child node corresponding to the branching unit, and transmits the optical signal to the through side otherwise. And
The second coupler transmits an optical signal to the cross side within the second wavelength band assigned to the child node corresponding to the branching unit, and transmits to the through side otherwise. And
The first port is connected to a first input / output end of the first coupler;
The second port is connected to a first input / output terminal of the second coupler;
The fourth port is connected to a second input / output terminal which is a through side with respect to the first input / output terminal of the first coupler;
The fifth port is connected to a second input / output terminal which is a through side with respect to the first input / output terminal of the second coupler;
The third port is connected to a third input / output terminal that is crossed with respect to the first input / output terminal of the second coupler;
A third input / output terminal that is crossed with respect to the first input / output terminal of the first coupler is a fourth side that is a through side with respect to the third input / output terminal of the second coupler. An optical transmission system connected to the input / output terminal of The optical transmission system according to claim 1,
Further comprising another parent node with a bus-type third system transmission path end and the bus-type fourth system transmission path two ports respectively connected to one end of the of the,
Each branch section is cascade-connected to any two transmission paths of the first to fourth transmission paths,
The at least one branching unit includes any one of the transmission line of the first system and the transmission line of the second system, and any of the transmission line of the third system and the transmission line of the fourth system. An optical transmission system characterized in that a child node connected in cascade to one of the transmission paths and corresponding to the branching unit is configured to be communicable with both parent nodes. . A parent node having two ports respectively connected to both ends of a single ring-shaped transmission line, a plurality of branch parts connected in cascade to the transmission line, and provided corresponding to each of the plurality of branch parts A plurality of child nodes, each of the plurality of child nodes is an optical transmission system that is communicably connected to the parent node via a corresponding branch unit,
Each branch unit corresponds to the first and second couplers, the first port connected to the parent node or branch unit adjacent in the counterclockwise direction via the transmission line, and the branch unit. A second port connected to the child node, and a third port connected to the parent node or branching portion adjacent to each other in the clockwise direction via the transmission path ,
Each branching unit receives the optical signal in the first wavelength band assigned to the corresponding child node among the optical signals input from the first port by the first and second couplers . 2, the optical signal outside the first wavelength band is guided to the third port, and the optical signal input from the third port is assigned to the corresponding child node. optical signal in the second wavelength band is guided to said second port, said second optical signals outside the wavelength band consists as is guided to the first port,
The first and second wavelength bands assigned to each child node are different from each other and set so as not to overlap each other between the child nodes;
The parent node and each child node set the optical signal used for communication with each other to one of the first and second wavelength bands assigned to the child node, so that the downlink in the transmission path is clockwise. Is configured to be communicable by either the first system in which the counterclockwise is counterclockwise and the second system in which the descending is counterclockwise and the upward is clockwise ,
The first coupler transmits an optical signal to the through side in the first wavelength band assigned to the child node corresponding to the branching unit, and transmits to the cross side otherwise. And
The second coupler transmits an optical signal to the through side in the second wavelength band assigned to the child node corresponding to the branch unit, and transmits to the cross side otherwise. And
The first port is connected to a first input / output end of the first coupler;
The third port is connected to a first input / output terminal of the second coupler;
The second port is connected to a second input / output terminal that is a through side with respect to the first input / output terminal of the first coupler;
A third input / output end that is crossed with respect to the first input / output end of the first coupler is second crossed with respect to the first input / output end of the second coupler. Connected to the input / output end of the
A fourth input / output end that is a cross side with respect to the second input / output end of the first coupler is a third side that is a through side with respect to the first input / output end of the second coupler. An optical transmission system connected to the input / output terminal of

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