JP2014060626A - Optical network and node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple node of low power consumption which can deal with ring connection and cascade connection easily.SOLUTION: An optical signal of wavelength λ1 propagates on a ring transmission line counterclockwise and enters a node, an optical signal of wavelength λ2 propagates on a ring transmission line clockwise and enters the node, and the node is dropped or transmitted. The node adds the optical signal of wavelength λ1 to propagate counterclockwise, and adds the optical signal of wavelength λ2 to propagate clockwise. In order to perform such route operation, the node is configured of an FBG optical encoder, an FBG optical decoder, a router having an internal route being converted by a wavelength and an input port, a circulator, an optical isolator, and the like.

Description

  The present invention relates to an optical network and a node, and can be applied to, for example, an optical access network for wide area subscribers.

  If the capacity of the network is promoted in the future, traffic demand is unevenly distributed in time and space in an access network that receives various service requests from users. Therefore, in the future, a new network architecture for performing highly efficient network control is required also in the access network. Currently, a system that integrates an access network and a metro network is being studied as a network architecture that enables the provision of optimal communication capacity. Non-Patent Document 1 shows ROADM (Reconfiguration Optical Add / Drop Multiplexer) that is used in a metro network. The access network can be configured. Non-Patent Document 2 shows an example in which ROADM and metro access using a WDM (Wavelength Division Multiplexing) filter are integrated.

JP 2010-171684 A

http: // www. nec. co. jp / spectralwave / dw4200 / " Thomas Pfeiffer, “Converged Heterogeneous Optical Metro-Access Networks”, ECOC2010, Tu5. B. 1

  However, the current network has a problem that power consumption is large because an active device (ROADM) is attached to a metro network. In order to reduce power consumption, control by passive routing is necessary. As a passive routing method, there is a method of using optical wavelength multiplexing or optical code multiplexing technology in a hybrid manner. However, when an optical code decoder of the FBG (Fiber Bragg Grating) type is used as an optical passive product, as shown in Patent Document 1, an optical code signal or an optical decoded signal is output only as a reflected signal. Therefore, in order to realize add / drop in ring connection or cascade connection, it is necessary to make the optical passive product complicated. On the other hand, many of the optical passive products having a simple configuration cannot support passive routing, and cannot recover communication when a failure occurs between nodes.

  The present invention has been made in view of the above points, and a simple and low power consumption node that can easily cope with ring connection and cascade connection, and communication recovery when a failure occurs, having such a node. It is intended to provide an optical network that can be used.

  1st this invention intervenes in optical communication with the 1st communication apparatus which self accommodates, and the 2nd communication apparatus provided in the central station which terminates a ring-shaped transmission line, A plurality of the ring-shaped transmission lines that are added to the ring-shaped transmission line, drop an optical signal from the ring-shaped transmission line, and pass the incoming optical signal. In one node, (1) a first input / output port to which an optical signal having a first wavelength propagating counterclockwise through the ring-shaped transmission line is input; and (2) the ring-shaped transmission line is clocked. A third input / output port for receiving an optical signal having a second wavelength propagating around and (3) a third communication device for transmitting and receiving an optical signal between the first communication device housed therein; (4) encoded with the first code assigned to the node A first FBG optical decoder that decodes an optical signal having a first wavelength, and a second FBG that decodes an optical signal having a second wavelength encoded with a second code assigned to the node. Decoder group in which optical decoders are connected in cascade, (5) a first FBG optical encoder that encodes an optical signal having a first wavelength with the first code, and light having a second wavelength A group of encoders cascaded with a second FBG optical encoder that encodes a signal with the second code; and (6) allowing an optical signal to travel from the decoder group to the encoder group; An optical isolator that prevents the optical signal from traveling in the reverse direction, and (7) a PL1 port, a PR1 port, a PL2 port, and a PR2 port. When an optical signal having the first wavelength is input to the PL1 port, the PR1 port And an optical signal having the second wavelength at the PL1 port When it is input, it is output to the PR2 port, when an optical signal having the first wavelength is input to the PL2 port, it is output to the PR1 port, and when an optical signal having the second wavelength is input to the PL2 port, the PR2 port When the optical signal having the first wavelength is input to the PR1 port, the optical signal is output to the PL1 port. When the optical signal having the second wavelength is input to the PR1 port, the optical signal is output to the PL2 port. Is output to the PL1 port when an optical signal having the first wavelength is input to the PL2 port, and is output to the PL2 port when an optical signal having the second wavelength is input to the PR2 port. A first router connected to the first input / output port; and (8) a PL1 port, a PR1 port, a PL2 port, and a PR2 port. When an optical signal having a length is input, it is output to the PR1 port, when an optical signal having the second wavelength is input to the PL1 port, it is output to the PR2 port, and an optical signal having the first wavelength is input to the PL2 port. When it is input, it is output to the PR1 port, when an optical signal having the second wavelength is input to the PL2 port, it is output to the PR2 port, and when an optical signal having the first wavelength is input to the PR1 port, the PL1 port When the optical signal having the second wavelength is input to the PR1 port, the optical signal is output to the PL2 port. When the optical signal having the first wavelength is input to the PR2 port, the optical signal is output to the PL1 port. Is output to the PL2 port when an optical signal having the second wavelength is input, the PR2 port is connected to the second input / output port, and the PR1 port is the first A second router connected to the PR1 port of the router, the PL1 port being connected to the PL1 port of the first router, and (9) first to third circulators each having a plurality of ports, 10) The first circulator provides an optical signal input from the PR2 port of the first router to the decoder group, an optical signal input from the decoder group to the third circulator, (11) The second circulator applies the optical signal input from the third circulator to the encoder group, and supplies the optical signal input from the encoder group to the PL2 port of the second router. (12) The third circulator applies the optical signal input from the first circulator to the third input / output port, and inputs from the third input / output port. The optical signal, characterized in that applied to the second circulator.

  The optical network according to the second aspect of the present invention is characterized in that a plurality of nodes according to the first aspect of the present invention are arranged on a ring-shaped transmission line where a central station terminates.

  ADVANTAGE OF THE INVENTION According to this invention, the simple and low power consumption node which can respond easily to ring connection and cascade connection can be provided. Furthermore, according to the present invention, it is possible to provide an optical network that can easily perform communication recovery when a failure occurs by applying such a node.

It is a block diagram which shows the whole structure of the optical network of embodiment. It is explanatory drawing of the ring connection in the optical network of embodiment. It is explanatory drawing of the cascade connection in the optical network of embodiment. It is a block diagram which shows the detailed structure of the OHF node in the optical network of embodiment. It is explanatory drawing of the routing of the router in the OHF node in the optical network of embodiment. It is a block diagram which shows the detailed structure of the concentration station in the optical network of embodiment. It is a block diagram which shows the internal structure of the encoder in the route control part in the optical network of embodiment. It is a block diagram which shows the internal structure of the decoder in the route control part in the optical network of embodiment. It is a block diagram which shows the detailed structure of the signal converter which makes a pair with ONU in the optical network of embodiment. It is explanatory drawing which shows the normal-time communication operation | movement of the whole optical network of embodiment. It is explanatory drawing which arrange | positions and shows the operation | movement pattern of the OHF node in the optical network of embodiment. FIG. 12 is a block diagram showing a flow of an optical signal in the OHF node in the first operation pattern of FIG. 11. FIG. 12 is a block diagram showing a flow of optical signals in the OHF node in the second operation pattern of FIG. 11. FIG. 12 is a block diagram illustrating a flow of an optical signal in the OHF node in the third operation pattern of FIG. 11. FIG. 12 is a block diagram showing a flow of an optical signal in the OHF node in the fourth operation pattern of FIG. 11. FIG. 12 is a block diagram showing the flow of optical signals in the OHF node in the fifth operation pattern of FIG. 11. FIG. 12 is a block diagram illustrating a flow of an optical signal in an OHF node in the sixth operation pattern of FIG. 11. FIG. 12 is a block diagram showing a flow of an optical signal in an OHF node in the seventh operation pattern of FIG. 11. FIG. 12 is a block diagram illustrating a flow of an optical signal in an OHF node in the eighth operation pattern of FIG. 11. It is a block diagram which shows the flow of the optical signal in the concentration station in the optical network of embodiment. It is a block diagram which shows the flow of the optical signal in the encoder of the route control part in the optical network of embodiment. It is a block diagram which shows the flow of the optical signal in the decoder of the route control part in the optical network of embodiment. It is a block diagram which shows the flow of the optical signal in the signal converter which makes a pair with ONU in the optical network of embodiment. It is explanatory drawing of the communication recovery | restoration operation | movement at the time of the failure occurrence between the adjacent OHF nodes in the optical network of embodiment. It is explanatory drawing of the communication recovery | restoration operation at the time of failure of (lambda) 1 pulse generator in the route control part in the optical network of embodiment. It is explanatory drawing of the optical network of deformation | transformation embodiment.

(A) Main Embodiment Hereinafter, an embodiment of an optical network and a node according to the present invention will be described with reference to the drawings.

(A-1) Configuration of Embodiment (A-1-1) Overall Configuration of Optical Network FIG. 1 is a block diagram showing the overall configuration of the optical network 1 of the embodiment.

  In FIG. 1, an optical network 1 according to the embodiment is a network in which a metro network 2 and a plurality (N in FIG. 1) of access networks 3-1 to 3-N are integrated.

  The metro network 2 includes the route control unit 6 of the centralized station 4 and the same number of optical hybrid filter (hereinafter referred to as OHF) nodes 7-1 to 7- as the number of access networks 3-1 to 3-N. A ring network in which N is connected in a ring shape through an optical fiber.

  The central station 4 has the same number of OLTs (Optical Line Terminals) 5-1 to 5-N as the number of access networks 3-1 to 3-N and the route control unit 6 described above. The OLTs 5-1 to 5-N are connected to the metro network 2 via the route control unit 6. The route control unit 6 connects the OLTs 5-1 to 5-N to an ONU (Optical Network Unit; optical subscriber line, which will be described later under the access networks 3-1 to 3-N (corresponding to the OLTs 5-1 to 5-N). It controls whether to connect to the subscriber side device)). Here, the OLT 5-n (n is 1 to N) corresponds to the access network 3-n.

  The OHF node 7-n is a component of both the metro network 2 and the access network 3-n, and an optical signal circulating around the metro network 2 is dropped on the access network 3-n. An optical signal from the access network 3-n is added to the metro network 2.

  In addition to the OHF node 7-n, the access network 3-n includes an optical coupler 8-n, a plurality (M in FIG. 1) of ONUs 9-n1 to 9-nM, and a signal converter 10- corresponding to each ONU. n1-10-nM. The number of ONUs may be different depending on the access networks 3-1 to 3-N (that is, M may be a value different depending on the access networks 3-1 to 3-N; The number of ONUs in the network is represented by M). The OHF node 7-n and the M ONUs 9-n1 to 9-nM have a one-to-M communication configuration via the optical coupler 8-n, and the ONUs 9-n1 to 9-nM optical coupler 8-n. Signal converters 10-n1 to 10-nM corresponding to the side are provided. The signal converters 10-n1 to 10-nM convert between an NRZ (Non-Return to Zero) optical signal and an RZ (Return to Zero) optical signal, as will be described later. The OHF node 7-n and the optical coupler 8-n, and the signal converters 10-n1 to 10-n and the optical coupler 8-n are respectively connected by optical fibers (hereinafter referred to as “optical fibers”). An optical fiber in an access network is sometimes called a feeder line.

  In addition, although components other than the optical coupler are interposed between the OLT 5 (5-1 to 5-N) and the ONU 9 (9-11 to 9-NM), the optical network 1 according to the embodiment has a function. Specifically, the same communication as that of a PON (Passive Optical Network) system is possible.

(A-1-2) Ring Connection and Cascade Connection The metro network 2 in the optical network 1 of the embodiment can take a ring connection and a cascade connection as a communicable connection form. Hereinafter, the ring connection and the cascade connection will be described from the plane of the optical signal traveling direction in the OHF node 7 (7-1 to 7-N).

  The OHF node 7 has three ports P1 to P3 as input / output ports. Hereinafter, an optical signal from the OLT 5 to the ONU 9 is referred to as a downstream optical signal, and an optical signal from the ONU 9 to the OLT 5 is referred to as an upstream optical signal. When the downstream optical signal is output counterclockwise from the central station 4, the input / output port of the OHF node 7-n to which the downstream optical signal is input is P1, and the input / output port opposite to the input / output port P1 is P2. And the input / output port to which the feeder line is connected is P3.

  As shown in FIG. 2, the ring connection refers to an input / output port pair of the OHF node 7 that inputs / outputs a downstream optical signal from the OLT 5 and an input / output port pair of the OHF node 7 that inputs / outputs an upstream optical signal from the ONU 9. However, even if the traveling direction is not a problem, the connection form is different.

  In the ring connection, the OHF node 7 drops the downstream optical signal from the metro network 2 to the ONU 9 side (dashed arrow AR1), and adds the upstream optical signal from the ONU 9 side to the metro network 2 (dashed arrow AR2). Either the downstream optical signal or the upstream optical signal transmitted (broken arrow AR3) is processed. When dropping, the port P1 is an input port and the port P3 is an output port. When adding, the port P3 is an input port and the port P2 is an output port, and the input / output port pair is different in the two processes. When transmitting, the port P1 is an input port and the port P2 is an output port.

  The ring-shaped metro network 2 in the optical network 1 according to the embodiment can be used for both a counterclockwise optical signal circulation and a clockwise optical signal circulation. (Refer to FIG. 2 shows the case of a counterclockwise optical signal circulation).

  As shown in FIG. 3, the cascade connection includes an input / output port pair of the OHF node 7 that inputs / outputs a downstream optical signal from the OLT 5 and an input / output port pair of the OHF node 7 that inputs / outputs an upstream optical signal from the ONU 9. However, when the traveling direction is not a problem, the connection form is the same.

  Cascade connection is a connection form when the metro network 2 is no longer ring-shaped. In the cascade connection, the OHF node 7 drops the downstream optical signal from the metro network 2 to the ONU 9 side (dashed arrow AR4), and adds the upstream optical signal from the ONU 9 side to the metro network 2 (dashed arrow AR5). The downstream optical signal is transmitted (broken arrow is omitted in FIG. 3) and the incoming upstream optical signal is transmitted (broken arrow is omitted in FIG. 3). The OHF node 7 that has been positioned at the end because it is no longer ring-shaped performs two types of processing, drop and add. When dropping, the port P1 is an input port and the port P3 is an output port. When adding, the port P3 is an input port and the port P1 is an output port, and the input / output port pair is the same in the two processes.

(A-1-3) Detailed Configuration of OHF Node FIG. 4 is a block diagram showing a detailed configuration of the OHF node 7 (7-1 to 7-N). All the OHF nodes 7-1 to 7-N have the same detailed configuration shown in FIG.

  In FIG. 4, the OHF node 7 includes three circulators 20 to 22, an FBG optical encoder 23 for wavelength λ1, an FBG optical encoder 24 for wavelength λ2, and an FBG optical decoder for wavelength λ1. And an optical isolator 29, an FBG optical decoder 26 for wavelength λ2, two routers 27 and 28, and an optical isolator 29.

  Each of the routers 27 and 28 has four input / output ports PL1, PL2, PR1, and PR2, and performs routing as shown in FIG. The routers 27 and 28 are configured by, for example, one optical multiplexer / demultiplexer or a combination of a plurality of optical multiplexers / demultiplexers, and do not include active components.

  When an optical signal with wavelength λ1 is input to port PL1, it is output from port PR1, and when an optical signal with wavelength λ1 is input to port PR1, it is output from port PL1. When an optical signal with wavelength λ1 is input to port PL2, it is output from port PR2, and when an optical signal with wavelength λ1 is input to port PR2, it is output from port PL2.

  On the other hand, when an optical signal with wavelength λ2 is input to port PL1, it is output from port PR2, and when an optical signal with wavelength λ2 is input to port PR1, it is output from port PL2. When an optical signal with wavelength λ2 is input to port PL2, it is output from port PR1, and when an optical signal with wavelength λ2 is input to port PR2, it is output from port PL1.

  Depending on the internal configuration of the routers 27 and 28, the optical signal does not necessarily travel straight or staggered in the interior, but from an image point of view, the optical signal of wavelength λ1 travels straight through the routers 27 and 28, and the light of wavelength λ2 The signal travels inside the routers 27 and 28.

  Each of the circulators 20 to 22 has three input / output ports. As shown in FIG. 4, the circulators 20 and 22 have a clockwise relationship between the input port and the output port, and the circulator 21 has a counterclockwise relationship between the input port and the output port.

  The above-described input / output port P1 of the OHF node 7 is connected to the port PL2 of the router 27. The above-described input / output port P2 of the OHF node 7 is connected to the port PR2 of the router 28. The above-described input / output port P3 of the OHF node 7 is connected to the input / output port of the circulator 21.

  Between the circulators 20 and 22, from the circulator 20 side, an FBG optical decoder 26 for wavelength λ2, an FBG optical decoder 25 for wavelength λ1, an optical isolator 29, an FBG optical encoder 23 for wavelength λ1, and FBG type optical encoders 24 for wavelength λ2 are connected in cascade. The arrangement of the FBG optical decoder 26 for the wavelength λ2 and the FBG optical decoder 25 for the wavelength λ1 may be reversed, and the FBG optical encoder 23 for the wavelength λ1 and the wavelength λ2 The arrangement of the FBG optical encoder 24 may be reversed.

  The port PR2 of the router 27 is connected to the input / output port of the circulator 20. The circulator 20 gives the optical signal from the router 27 (port PR2) to the FBG optical decoder 26 for the wavelength λ2, and gives the optical signal from the FBG optical decoder 26 for the wavelength λ2 to the circulator 21. The optical signal from 21 is given to the router 27 (port PR2 thereof).

  The port PL2 of the router 28 is connected to the input / output port of the circulator 22. The circulator 22 gives an optical signal from the router 28 (port PL2 thereof) to the circulator 20, gives an optical signal from the circulator 21 to the FBG optical encoder 24 for wavelength λ2, and an FBG optical encoder for wavelength λ2. The optical signal from 24 is given to the router 28 (port PL2 thereof).

  The circulator 21 supplies the optical signal from the circulator 20 to the input / output port P3 and supplies the optical signal from the input / output port P3 to the circulator 22.

  The FBG type optical decoder 26 for the wavelength λ2 decodes the optical signal from the circulator 20 when the wavelength is λ2 and is encoded with a code unique to the OHF node 7 to the circulator 20 side. The optical signal that does not satisfy the above condition is transmitted.

  The FBG optical decoder 25 for the wavelength λ1 is used when the optical signal from the FBG optical decoder 26 for the wavelength λ2 has a wavelength of λ1 and is encoded with a code unique to the OHF node 7. The optical signal is decoded and returned to the side of the FBG optical decoder 26 for the wavelength λ2, and an optical signal that does not satisfy the above condition is transmitted.

  Here, if the OHF node 7 is the OHF node 7-i, the FBG optical decoder 26 for the wavelength λ2 decodes using the unique code λ2codei, and if the OHF node 7 is the OHF node 7-j. The FBG optical decoder 26 for wavelength λ2 decodes using the unique code λ2codej. Similarly, if the OHF node 7 is the OHF node 7-i, the FBG optical decoder 25 for the wavelength λ1 decodes using the unique code λ1codei, and if the OHF node 7 is the OHF node 7-j. The FBG optical decoder 26 for wavelength λ1 decodes using the unique code λ1codej.

  The optical isolator 29 transmits the optical signal from the side of the FBG optical decoder 25 for the wavelength λ1, but blocks the transmission of the optical signal from the side of the FBG optical encoder 23 for the wavelength λ1.

  The FBG type optical encoder 24 for the wavelength λ2 encodes and returns the optical signal from the circulator 22 to the circulator 22 side when the optical signal from the circulator 22 has the wavelength λ2, and transmits the optical signal that does not satisfy the above conditions. It is.

  The FBG optical encoder 23 for the wavelength λ1 encodes the optical signal from the FBG optical encoder 24 for the wavelength λ2 to the side of the FBG optical encoder 24 for the wavelength λ2 when the optical signal is the wavelength λ1. The optical signal that does not satisfy the above condition is transmitted. Even if it is transmitted, it is discarded by the optical isolator 29.

  Here, if the OHF node 7 is the OHF node 7-i, the FBG optical encoder 24 for the wavelength λ2 encodes using the unique code λ2codei, and if the OHF node 7 is the OHF node 7-j. The FBG optical encoder 24 for the wavelength λ2 performs encoding using the unique code λ2codej. Similarly, if the OHF node 7 is the OHF node 7-i, the FBG optical encoder 23 for the wavelength λ1 encodes using the unique code λ1codei, and if the OHF node 7 is the OHF node 7-j. The FBG optical encoder 23 for wavelength λ1 encodes using the unique code λ1codej.

  The unique codes applied by the FBG optical encoder 23 and the FBG optical decoder 25 for the wavelength λ1 are the same. The unique codes applied by the FBG optical encoder 24 and the FBG optical decoder 26 for the wavelength λ2 are the same.

  In the two routers 27 and 28 described above, some ports are directly connected to the ports of the other router. That is, port PL1 of router 27 is connected to port PL1 of router 28, and port PR1 of router 27 is connected to port PR1 of router 28.

  As will be apparent from the operation description to be described later, the OHF node 7 having the configuration shown in FIG. 4 can cope with the connection state of the optical network 1 that is either ring connection or cascade connection.

(A-1-4) Detailed Configuration of Central Station FIG. 6 is a block diagram showing a detailed configuration of the central station 4, particularly a detailed configuration of the route control unit 6.

  As described above, the central station 4 includes the number of OLTs 5-1 to 5-N equal to the number of access networks and the route control unit 6.

  The route control unit 6 includes a network state management unit 30, a λ1 pulse generator 31, a λ2 pulse generator 32, N wavelength selection units (λsel units) 33-1 to 33-N, and N NRZ / RZ conversion units. 34-1 to 34-N, N encoders 35-1 to 35-N, wavelength multiplexer / demultiplexer 36, two circulators 37 and 38, optical coupler 39, N decoders 40-1 to 40-N , N RZ / NRZ converters 41-1 to 41-N.

  The network state management unit 30 receives fault information and the like regarding the metro network 2 from the OLTs 5-1 to 5-N, monitors the current state of the metro network 2, and uses the OLT (1 And communication with the ONU is determined by ring connection or cascade connection. The network state management unit 30 determines to apply the same connection form to all sets when there are a plurality of sets of OLTs and ONUs used for communication. The determination method will be clarified in the description of the operation described later. The network state management unit 30 transmits a wavelength selection control signal to the wavelength selection units 33-1 to 33-N according to the determined contents, or from the OLTs 5-1 to 5-N to the subordinate ONUs. A control signal indicating the wavelength of the optical pulse selected by the corresponding signal converter is transmitted.

  The NRZ / RZ conversion unit 34-n converts the NRZ optical signal from the corresponding OLT 5-n (the transmission unit (Tx) thereof) into an RZ optical signal having the wavelength selected by the corresponding wavelength selection unit 33-n. To do. Here, the wavelength of the NRZ optical signal from the corresponding OLT 5-n is not questioned. The NRZ / RZ conversion unit 34-n may be an all-optical processing unit or may use an electrical signal processing. For example, when the NRZ optical signal from the corresponding OLT 5-n is converted into an electrical signal, converted into an RZ signal at the stage of the electrical signal, and the electrical RZ signal is converted into an optical signal, the corresponding wavelength selection unit 33 You may make it have the wavelength selected by -n.

  In this embodiment, the optical signals from the OLTs 5-1 to 5-N are NRZ signals, but the optical signals from the OLTs 5-1 to 5-N may be RZ signals or RZ signals. Instead of the NRZ / RZ conversion unit, a wavelength conversion unit that converts only the wavelength without converting the signal format is applied.

  The λ1 pulse generator 31 and the λ2 pulse generator 32 generate short pulses (hereinafter referred to as λ1 pulse and λ2 pulse) having wavelengths λ1 and λ2, respectively.

  The wavelength selection unit (λsel unit) 33-n selects a λ1 pulse or a λ2 pulse in accordance with a wavelength selection control signal from the network state management unit 30, and gives it to the corresponding NRZ / RZ conversion unit 34-n. is there.

  The encoder 35-n encodes the RZ optical signal given from the corresponding NRZ / RZ conversion unit 34-n. The encoders 35-1 to 35-N have the same configuration, and only the applied codes are different.

  FIG. 7 is a block diagram showing an internal configuration of the encoder 35-1 as a representative. The encoder 35-1 includes a circulator 50, an FBG optical encoder 51 for wavelength λ2, and an FBG optical encoder 52 for wavelength λ1. The arrangement of the FBG optical encoder 51 for the wavelength λ2 and the FBG optical encoder 52 for the wavelength λ1 may be the reverse of FIG.

  The circulator 50 provides the optical signal from the NRZ / RZ conversion unit 34-n to the FBG optical encoder 51 for the wavelength λ2, and the encoded optical signal from the FBG optical encoder 51 side for the wavelength λ2. This is given to the wavelength multiplexer / demultiplexer 36 (see FIG. 6). The FBG optical encoder 51 for the wavelength λ2 transmits when the wavelength of the optical signal from the circulator 50 is λ1, and encodes it using the code λ2code1 determined for the OHF node 7-1 when the wavelength is λ2. To return to the circulator 50. The FBG optical encoder 52 for the wavelength λ1 encodes the optical signal of the wavelength λ1 transmitted through the FBG optical encoder 51 for the wavelength λ2 by using the code λ1code1 determined for the OHF node 7-1. To return to the circulator 50 side. The FBG optical encoder 51 for the wavelength λ2 and the FBG optical encoder 52 for the wavelength λ1 are the FBG optical decoder for the wavelength λ2 (see reference numeral 26 in FIG. 4) and the wavelength λ1 at the OHF node 7-1. This corresponds to the FBG type optical decoder (see reference numeral 25 in FIG. 4).

  Returning to FIG. 6, the wavelength multiplexer / demultiplexer 36 gives the optical signal of the wavelength λ1 from the encoders 35-1 to 35 -N to the circulator 37, and the optical signal of the wavelength λ2 from the encoders 35-1 to 35 -N. This is given to the circulator 38.

  The circulators 37 and 38 are provided at positions where the ring-shaped transmission line of the metro network 2 is terminated. The circulator 37 introduces an optical signal having a wavelength λ1 from the wavelength multiplexer / demultiplexer 36 so as to circulate counterclockwise to the metro network 2, and an optical signal that has been circulated clockwise from the metro network 2 (this The wavelength of the optical signal gives λ2) to the optical coupler 39. The circulator 38 introduces the optical signal having the wavelength λ2 from the wavelength multiplexer / demultiplexer 36 so as to circulate in the clockwise direction to the metro network 2, and the optical signal that has been circulated counterclockwise from the metro network 2 (this The wavelength of the optical signal gives λ1) to the optical coupler 39.

  The optical coupler 39 combines the optical signal having the wavelength λ2 from the metro network 2 side via the circulator 37 and the optical signal having the wavelength λ1 from the metro network 2 side via the circulator 38 to the decoder 40-1. Give.

  The N decoders 40-1 to 40-N decode and input the corresponding RZ / NRZ conversion units 41-1 to 41-N when the input optical signal is encoded with a code assigned to itself. When the input optical signal is not encoded with the code assigned to itself, the input optical signal is transmitted to the next stage decoder (however, the final stage decoder 40-N). Terminates the input optical signal if it is not encoded with the code assigned to it). The decoders 40-1 to 40-N have the same configuration, and only the applied codes are different.

  FIG. 8 is a block diagram showing the internal configuration of the decoder 40-1 as a representative. The decoder 40-1 includes a circulator 60, an FBG optical decoder 61 for wavelength λ1, and an FBG optical decoder 62 for wavelength λ2. The arrangement of the FBG optical decoder 61 for the wavelength λ1 and the FBG optical decoder 62 for the wavelength λ2 may be the reverse of FIG.

  The circulator 60 gives the optical signal from the optical coupler 39 to the FBG optical decoder 61 for wavelength λ1, and the RZ / NRZ converter 41 receives the decoded optical signal from the FBG optical decoder 61 side for wavelength λ1. -1 (see FIG. 6). The FBG optical decoder 61 for the wavelength λ1 transmits when the wavelength of the optical signal from the circulator 60 is λ2, and is encoded with the code λ1code1 determined for the OHF node 7-1 when the wavelength is λ1. If it is decoded, it is returned to the circulator 51. If it is not encoded with the code λ1code1 determined for the OHF node 7-1 even though it has the wavelength λ1, it is transmitted. The FBG optical decoder 62 for the wavelength λ2 is encoded with the code λ2code1 determined for the OHF node 7-1 in which the wavelength of the optical signal from the FBG optical decoder 61 for the wavelength λ1 is λ2. If so, it is decoded and returned to the FBG optical decoder 61 for wavelength λ1, and otherwise it is transmitted. The FBG optical decoder 61 for the wavelength λ1 and the FBG optical decoder 62 for the wavelength λ2 are the FBG optical encoder for the wavelength λ1 (see reference numeral 23 in FIG. 4) and the wavelength λ2 at the OHF node 7-1. This corresponds to the FBG type optical encoder (see reference numeral 24 in FIG. 4).

  Returning to FIG. 6, the RZ / NRZ conversion unit 41-n converts the optical signal (RZ optical signal) from the corresponding decoder 40-n into an NRZ optical signal and sends it to the reception unit (Rx) of the corresponding OLT 5-n. Give. The RZ / NRZ conversion unit 41-n can perform conversion processing regardless of whether the wavelength of the incoming optical signal is λ1 or λ2. Here, the wavelength of the NRZ optical signal to the corresponding OLT 5-n is not questioned. The RZ / NRZ conversion unit 41-n may be an all-optical process, or may use a process with an electric signal. For example, when an input RZ optical signal is converted into an electrical signal, converted into an NRZ signal at the stage of the electrical signal, and an electrical NRZ signal is converted into an optical signal, it has a wavelength to the corresponding OLT 5-n. You may do it.

  In this embodiment, the optical signals to the OLTs 5-1 to 5-N are NRZ signals, but the optical signals to the OLTs 5-1 to 5-N may be RZ signals or RZ signals. Instead of the RZ / NRZ conversion unit, a wavelength conversion unit that converts only the wavelength without converting the signal format is applied.

(A-1-5) Detailed Configuration of Signal Converter FIG. 9 shows a detailed configuration of the signal converter 10 (10-11 to 10-NM) paired with the ONU 9 (9-11 to 9-NM). FIG. In the case of this embodiment, it can be seen that the ONU 9 and the signal converter 10 constitute a new ONU.

  The signal converter 10 includes a λ1 pulse generator 70, a λ2 pulse generator 71, an NRZ / RZ conversion unit 72, a circulator 73, and an RZ / NRZ conversion unit 74.

  The NRZ / RZ conversion unit 72 converts the NRZ optical signal from the (transmitting unit (Tx)) of the ONU 9 into an RZ optical signal by applying the optical pulse from the λ1 pulse generator 70 or the λ2 pulse generator 71. Is.

  Each of the λ1 pulse generator 70 and the λ2 pulse generator 71 generates optical pulses having wavelengths λ1 and λ2 based on a signal (consisting of an electrical signal) from the transmission unit (Tx) of the ONU 9. The ONU 9 is substantially the same as the configuration of the existing ONU, but further includes a transmission wavelength indication configuration. Some control signals from the corresponding OLT indicate the transmission wavelength. When receiving the control signal, the ONU 9 sends an optical pulse from the λ1 pulse generator 70 if the instruction is the wavelength λ1. If the instruction is a wavelength λ2, an optical pulse is generated from the λ2 pulse generator 71. As described above, since the λ1 pulse generator 70 or the λ2 pulse generator 71 performs a generation operation alternatively, no wavelength selection unit is provided. Incidentally, the signals from the route control unit 6 are given to a plurality of access networks, and there are access networks that transmit optical signals of wavelength λ1 and access networks that transmit optical signals of wavelength λ2. The optical component is generated at the same time, and the wavelength component is selected for each access network (accordingly, OHF node) of the transmission destination.

  The ONU 9 may switch the λ1 pulse generator 70 or the λ2 pulse generator 71 generated when receiving the control signal from the OLT 5 regardless of the upstream optical signal transmission operation. Alternatively, one of the λ1 pulse generator 70 and the λ2 pulse generator 71 may be instructed to generate.

  As the λ1 pulse generator 70 and the λ2 pulse generator 71, a variable wavelength pulse generator may be applied to switch the generation wavelength.

  The circulator 73 gives the RZ optical signal from the NRZ / RZ conversion unit 72 to the metro network 2 side, and gives the optical signal (RZ optical signal) arriving from the metro network 2 side to the RZ / NRZ conversion unit 74.

  The RZ / NRZ conversion unit 74 converts an optical signal (RZ optical signal) that has arrived from the metro network 2 side into an NRZ optical signal and provides the signal to the corresponding ONU 9. The RZ / NRZ conversion unit 74 can execute conversion processing regardless of whether the wavelength of the incoming optical signal is λ1 or λ2.

(A-2) Operation | movement of embodiment Next, operation | movement of the optical network 1 of embodiment is demonstrated.

(A-2-1) Normal communication operation of the entire optical network 1 First, a normal communication operation of the entire optical network 1 according to the embodiment in which no failure has occurred will be described with reference to FIG.

  In normal times, the centralized station 4 transmits a downstream optical signal having the wavelength λ1 regardless of which access network 3-1 to 3-N the destination belongs to. As in the internal operation of the central station 4 to be described later, the downstream optical signal having the wavelength λ1 is sent to the metro network 2 so as to circulate counterclockwise.

  Like the internal operation of the OHF node 7 described later, the OHF node 7-n drops the downstream optical signal of the wavelength λ1 to the ONUs 9-n1 to 9-nM belonging to the access network 3-n related to the OHF node 7-n (see FIG. 13), the downstream optical signal with wavelength λ1 and the upstream optical signal with wavelength λ1 are transmitted to ONUs belonging to other access networks (see FIGS. 14 and 15).

  The OLT 5-n in the central station 4 sends an upstream optical signal at a wavelength λ1 to the ONUs 9-n1 to 9-nM under the corresponding access network 3-n by a control signal in normal times. The ONUs 9-n1 to 9-nM instruct the corresponding signal converters 10-n1 to 10-nM to generate a pulse with the wavelength λ1. As a result, an upstream signal having the wavelength λ1 is transmitted from the signal converters 10-n1 to 10-nM.

  As in the internal operation of the OHF node 7 to be described later, the OHF node 7-n circulates the upstream optical signal of the wavelength λ1 from the access network 3-n related to itself in the metro network 2 counterclockwise. Add (see FIG. 12).

(A-2-2) Operation of OHF Node Next, the operation of the OHF node 7-n will be described with respect to eight patterns.

  Each operation pattern can be switched by selecting the wavelength of the downstream optical signal and the wavelength of the upstream optical signal within the centralized station 4. FIG. 11 is an explanatory diagram showing the differences in the eight operation patterns. In FIG. 11, the eight operation patterns are distinguished from the aspects of “input optical signal wavelength”, “operation type”, “communication direction”, “input port”, “output port”, and “encoding / decoding”. Can do.

  The first to fourth operation patterns in which the wavelength of the optical signal is λ1 are the operation patterns related to the normal state or when communication is restored due to the occurrence of a failure, but the fifth to eighth operations in which the wavelength of the optical signal is λ2. The operation pattern is an operation pattern related to communication restoration accompanying the occurrence of a failure, and the operations of the fifth to eighth operation patterns are not executed in normal times.

(A-2-2-1) First Operation Pattern of OHF Node Next, the signal flow in the first (first in FIG. 11) operation pattern of the OHF node 7-n will be described with reference to FIG. explain.

  The upstream optical signal having the wavelength λ1 from the corresponding access network 3-n is input to the port P3 and passes through the circulators 21 and 22 and the FBG optical encoder 24 for the wavelength λ2, and the FBG optical encoder for the wavelength λ1. 23. Since the wavelength of the inputted optical signal is λ1, the code λ1coden assigned to the FBG type optical encoder 23 for wavelength λ1 is applied to the inputted optical signal in the FBG type optical encoder 23 for wavelength λ1. And encoded while being reflected. The encoded upstream optical signal is input to the port PL 2 of the router 28 via the FBG optical encoder 24 for wavelength λ 2 and the circulator 22. Since the optical signal having the wavelength λ1 is input to the port PL2, the router 28 outputs the optical signal from the port PR2, and this optical signal is added to the metro network 2 via the port P2.

(A-2-2-2) Second Operation Pattern of OHF Node Next, the signal flow in the second (second operation in FIG. 11) operation pattern of the OHF node 7-n will be described with reference to FIG. explain.

  A downstream optical signal having a wavelength λ1 that circulates counterclockwise in the metro network 2 and is addressed to any one of the ONUs 9-n1 to 9-nM in the access network 3-n under the OHF node 7-n. The downstream optical signal is input to the port P1 and input to the port PL2 of the router 27. Since the optical signal having the wavelength λ1 is input to the port PL2, the router 27 outputs the optical signal from the port PR2, and this optical signal passes through the circulator 20 and the FBG optical decoder 26 for wavelength λ2. To the FBG type optical decoder 25. Since the wavelength of the input optical signal is λ1 and is encoded with the code λ1coden assigned to the FBG optical decoder 25 for wavelength λ1, the input optical signal is FBG optical recovery for wavelength λ1. In the encoder 25, the code λ1code is applied and decoded while being reflected. The decoded downstream optical signal is dropped from the port P3 to the access network 3-n via the wavelength λ2 FBG optical decoder 26 and the circulators 20 and 21.

(A-2-2-3) Third Operation Pattern of OHF Node Next, the signal flow in the third (third in FIG. 11) operation pattern of the OHF node 7-n will be described with reference to FIG. explain.

  An upstream optical signal having a wavelength λ1 that has already been added to the metro network 2 by the front OHF node in the counterclockwise circulation direction may be input to the OHF node 7-n. Such an upstream optical signal is input to the port P1 and input to the port PL2 of the router 27. Since the optical signal having the wavelength λ1 is input to the port PL2, the router 27 outputs the optical signal from the port PR2, and this optical signal passes through the circulator 20 and the FBG optical decoder 26 for wavelength λ2. To the FBG type optical decoder 25. Since the input optical signal is not encoded with the code λ1coden assigned to the wavelength λ1 FBG optical decoder 25, the optical signal is transmitted through the wavelength λ1 FBG optical decoder 25, and then the optical isolator 29, The signal is input to the port PL 2 of the router 28 via the FBG optical encoder 23 for wavelength λ 1, the FBG optical encoder 24 for wavelength λ 2, and the circulator 22. Since the optical signal having the wavelength λ1 is input to the port PL2, the router 28 outputs the optical signal from the port PR2, and this optical signal is transmitted to the metro network 2 via the port P2.

  As described above, in the third operation pattern, the upstream optical signal input to the port P1 goes out from the port P2 as it is.

(A-2-2-4) Fourth Operation Pattern of OHF Node Next, the signal flow in the fourth (fourth operation pattern in FIG. 11) operation pattern of the OHF node 7-n will be described with reference to FIG. explain.

  One of the ONUs in the access network under the OHF node that is a downstream optical signal having a wavelength λ1 that circulates in the counterclockwise direction in the metro network 2 and is located in the circulation direction before the OHF node 7-n The downstream optical signal destined for is also input to the port P1 and input to the port PL2 of the router 27. Since the optical signal having the wavelength λ1 is input to the port PL2, the router 27 outputs the optical signal from the port PR2, and this optical signal passes through the circulator 20 and the FBG optical decoder 26 for wavelength λ2. To the FBG type optical decoder 25. Since the input optical signal is not encoded with the code λ1coden assigned to the wavelength λ1 FBG optical decoder 25, the optical signal is transmitted through the wavelength λ1 FBG optical decoder 25, and then the optical isolator 29, The signal is input to the port PL 2 of the router 28 via the FBG optical encoder 23 for wavelength λ 1, the FBG optical encoder 24 for wavelength λ 2, and the circulator 22. Since the optical signal having the wavelength λ1 is input to the port PL2, the router 28 outputs the optical signal from the port PR2, and this optical signal is transmitted to the metro network 2 via the port P2.

  As described above, in the fourth operation pattern, the downstream optical signal input to the port P1 goes out from the port P2 as it is.

  In the third operation pattern and the fourth operation pattern, the input optical signal is an upstream optical signal added by the OHF node before the OHF node 7-n in the cyclic direction, or the OHF node 7- Although there is a difference in whether the OHF node ahead in the cyclic direction from n is a downstream optical signal to be dropped, the same is true in that the OHF node 7-n transmits the input optical signal as it is.

(A-2-2-5) Fifth Operation Pattern of OHF Node Next, the signal flow in the fifth (fifth operation pattern in FIG. 11) operation of the OHF node 7-n will be described with reference to FIG. explain.

  The upstream optical signal having the wavelength λ2 from the corresponding access network 3-n is input to the port P3, and is input to the FBG optical encoder 24 for wavelength λ2 via the circulators 21 and 22. Since the wavelength of the input optical signal is λ2, the code λ2coden assigned to the FBG optical encoder for wavelength λ2 is applied to the input optical signal in the FBG optical encoder for wavelength λ2. And encoded while being reflected. The encoded upstream optical signal is input to the port PL2 of the router 28 via the circulator 22. Since the optical signal having the wavelength λ2 is input to the port PL2, the router 28 outputs the optical signal from the port PR1, and thereby input to the port PR1 of the router 27. Since the optical signal having the wavelength λ2 is input to the port PR1, the router 27 outputs the optical signal from the port PL2, and this optical signal is added to the metro network 2 via the port P1.

(A-2-2-6) Sixth Operation Pattern of OHF Node Next, the flow of signals in the sixth (sixth operation pattern in FIG. 11) operation of the OHF node 7-n will be described with reference to FIG. explain.

  A downstream optical signal of wavelength λ2 that circulates in the metro network 2 in the clockwise direction, and is destined for any one of the ONUs 9-n1 to 9-nM in the access network 3-n under the OHF node 7-n. The downstream optical signal is input to the port P2 and input to the port PR2 of the router 28. Since the optical signal having the wavelength λ2 is input to the port PR2, the router 28 outputs the optical signal from the port PL1L, and thereby input to the port PL1 of the router 27. Since the optical signal having the wavelength λ2 is input to the port PL1, the router 27 outputs the optical signal from the port PR2, and this optical signal is input to the FBG optical decoder 26 for wavelength λ2 via the circulator 20. The Since the wavelength of the input optical signal is λ2 and is encoded by the code λ2coden assigned to the FBG optical decoder 26 for wavelength λ2, the input optical signal is FBG optical recovery for wavelength λ2. In the encoder 26, the code λ2code is applied and decoded while being reflected. The decoded downstream optical signal is dropped from the port P3 to the access network 3-n via the circulators 20 and 21.

(A-2-2-7) Seventh Operation Pattern of OHF Node Next, the signal flow in the seventh (seventh operation pattern in FIG. 11) operation of the OHF node 7-n will be described with reference to FIG. explain.

  An upstream optical signal having a wavelength λ2 that has been added to the metro network 2 by the OHF node on the front side in the clockwise direction may be input to the OHF node 7-n. Such an upstream optical signal is input to the port P2 and input to the port PR2 of the router 28. Since the optical signal having the wavelength λ2 is input to the port PR2, the router 28 outputs the optical signal from the port P1L, and thereby input to the port PL1 of the router 27. Since the optical signal having the wavelength λ2 is input to the port PL1, the router 27 outputs the optical signal from the port PR2. Since this optical signal is a signal encoded by another OHF node, the circulator 20, the FBG optical decoder for wavelength λ2, the FBG optical decoder for wavelength λ1, the optical isolator 29, and the FBG for wavelength λ1 Is input to the port PL 2 of the router 28 via the optical encoder 23, the FBG optical encoder 24 for wavelength λ 2, and the circulator 22. Since the optical signal having the wavelength λ2 is input to the port PL2, the router 28 outputs the optical signal from the port PR1, and thereby input to the port PR1 of the router 27. Since the optical signal having the wavelength λ2 is input to the port PR1, the router 27 outputs the optical signal from the port PL2, and the optical signal is transmitted to the metro network 2 via the port P1.

  As described above, in the seventh operation pattern, the upstream optical signal input to the port P2 goes out from the port P1 as it is.

(A-2-2-8) Eighth Operation Pattern of OHF Node Next, the flow of signals in the eighth (eighth in FIG. 11) operation pattern of the OHF node 7-n will be described with reference to FIG. explain.

  One of the ONUs in the access network under the OHF node that is a downstream optical signal of wavelength λ2 that circulates in the metro network 2 in the clockwise direction and that is located earlier in the circulation direction than the OHF node 7-n. The downstream optical signal as the destination is also input to the port P2 and input to the port PR2 of the router 28. Since the optical signal having the wavelength λ2 is input to the port PR2, the router 28 outputs the optical signal from the port P1L, and thereby input to the port PL1 of the router 27. Since the optical signal having the wavelength λ2 is input to the port PL1, the router 27 outputs the optical signal from the port PR2. Since this optical signal is a signal directed to the previous OHF node, the circulator 20, the FBG optical decoder for wavelength λ2, the FBG optical decoder for wavelength λ1, the optical isolator 29, and the FBG optical for wavelength λ1 The signal is input to the port PL 2 of the router 28 via the encoder 23, the FBG optical encoder 24 for wavelength λ 2, and the circulator 22. Since the optical signal having the wavelength λ2 is input to the port PL2, the router 28 outputs the optical signal from the port PR1, and thereby input to the port PR1 of the router 27. Since the optical signal having the wavelength λ2 is input to the port PR1, the router 27 outputs the optical signal from the port PL2, and the optical signal is transmitted to the metro network 2 via the port P1.

  As described above, in the eighth operation pattern, the downstream optical signal input to the port P2 goes out from the port P1 as it is.

  In the seventh operation pattern and the eighth operation pattern, the input optical signal is an upstream optical signal added by an OHF node before the OHF node 7-n in the cyclic direction, or the OHF node 7- Although there is a difference in whether the OHF node ahead in the cyclic direction from n is a downstream optical signal to be dropped, the same is true in that the OHF node 7-n transmits the input optical signal as it is.

(A-2-3) Operation of Central Station Next, the operation of the central station 4 will be described with reference to FIG. FIG. 20 mainly shows the flow of optical signals in the route control unit 6 when the OLT 5-1 communicates. Hereinafter, the operation of the central station 4 will be described on the assumption that the OLT 5-1 communicates, but the same operation is executed even when other OLTs communicate.

(A-2-3-1) Downstream processing in the central station When the network state management unit 30 determines that the current network state is a state in which no failure has occurred in the metro network 2 or the like, When the OLT 5-1 has a transmission request for the downstream optical signal, the network state management unit 30 gives a wavelength selection control signal for instructing the wavelength λ1 to the wavelength selection unit 33-1. In response to this, the wavelength selector 33-1 supplies the NRZ / RZ converter 34-1 with the optical pulse of the wavelength λ1 generated by the λ1 pulse generator 31.

  The NRZ / RZ conversion unit 34-1 converts the NRZ optical signal (downstream optical signal) from the corresponding OLT 5-1 (the transmission unit (Tx) thereof) into the wavelength λ1 selected by the corresponding wavelength selection unit 33-1. The RZ optical signal is converted and provided to the encoder 35-1, and the encoder 35-1 encodes the input optical signal using the code λ1code1 associated with the wavelength λ1 assigned to the encoder 35-1. The encoded optical signal having the wavelength λ1 is supplied to the wavelength multiplexer / demultiplexer 36, output from the port for the wavelength λ1, and introduced into the metro network 2 in the counterclockwise direction via the circulator 37. .

  In the encoder 35-1, when the optical signal with the wavelength λ1 arrives at the input port (the operation when the optical signal with the wavelength λ2 arrives at the input port is shown in FIG. 21, it will be referred to). The FBG optical encoder 52 for wavelength λ1 is supplied to the FBG optical encoder 52 for wavelength λ1 via the circulator 50 and the FBG optical encoder 51 for wavelength λ2, and the FBG optical encoder 52 for wavelength λ1 in the FBG optical encoder 52 for wavelength λ1. The code λ1code1 assigned to is applied and encoded while being reflected. The encoded optical signal having the wavelength λ1 is transmitted from the output port via the wavelength λ2 FBG optical encoder 51 and the circulator 50.

  On the other hand, when the network state management unit 30 receives a downstream optical signal transmission request from the OLT 5-1, the current network state is not normal, and the OLT 5-1, so as to go around the metro network 2 clockwise. When it is determined that the downstream optical signal should be transmitted, the network state management unit 30 gives the wavelength selection control signal instructing the wavelength λ2 to the wavelength selection unit 33-1. In response to this, the wavelength selector 33-1 supplies the NRZ / RZ converter 34-1 with the optical pulse having the wavelength λ2 generated by the λ2 pulse generator 32.

  The NRZ / RZ conversion unit 34-1 converts the NRZ optical signal (downstream optical signal) from the corresponding OLT 5-1 (the transmission unit (Tx) thereof) into the wavelength λ2 selected by the corresponding wavelength selection unit 33-1. The RZ optical signal is converted and provided to the encoder 35-1, and the encoder 35-1 encodes the input optical signal using the code λ2code1 associated with the wavelength λ2 assigned to the encoder 35-1. The encoded optical signal having the wavelength λ2 is given to the wavelength multiplexer / demultiplexer 36, output from the port for the wavelength λ2, and introduced into the metro network 2 through the circulator 37 in the clockwise direction.

  In the encoder 35-1, when an optical signal of wavelength λ2 arrives at the input port, as shown in FIG. 21, it is given to the FBG optical encoder 51 for wavelength λ2 via the circulator 50, and the FBG for wavelength λ2 In the optical encoder 51, the code λ2code1 assigned to the FBG optical encoder 51 for wavelength λ2 is applied and encoded while being reflected. The encoded optical signal having the wavelength λ 2 is sent from the output port via the circulator 50.

(A-2-3-2) Upstream processing in the centralized station The upstream optical signal of wavelength λ1 is input to a port to which an optical signal that circulates counterclockwise in the metro network 2 is input. Even if a failure occurs in the metro network 2 and it is not a ring network, it is input to the same port as when it was a ring network.

  The upstream optical signal having the wavelength λ1 addressed to the OLT 5-1 is input from the metro network 2 to the circulator 38, and further passes through the optical coupler 39 that combines the upstream optical signal having the wavelength λ1 and the upstream optical signal having the wavelength λ2. , Provided to the decoder 40-1. The decoder 40-1 decodes the input optical signal by using the code λ1code1 related to the wavelength λ1 assigned to itself. The decoded optical signal of wavelength λ1 (RZ optical signal) is given to the RZ / NRZ conversion unit 41-1, converted into the NRZ optical signal by the RZ / NRZ conversion unit 41-1, and then converted to the OLT 5-1 (of To the receiving unit (Rx).

  In the decoder 40-1, when the optical signal with the wavelength λ1 arrives at the input port (note that the operation when the optical signal with the wavelength λ2 arrives at the input port is shown in FIG. 22 and will be referred to). The signal λ1code1 assigned to the wavelength λ1 FBG optical decoder 61 is applied to the wavelength λ1 FBG optical decoder 61 via the circulator 60. It is decoded while being reflected. The decoded optical signal having the wavelength λ1 is sent from the output port via the circulator 60.

  The upstream optical signal having the wavelength λ2 addressed to the OLT 5-1 is input from the metro network 2 to the circulator 38, and further passes through the optical coupler 39 that combines the upstream optical signal having the wavelength λ1 and the upstream optical signal having the wavelength λ2. And supplied to the decoder 40-1. The decoder 40-1 decodes the input optical signal by using the code λ2code1 related to the wavelength λ2 allocated to itself. The decoded optical signal of wavelength λ2 (RZ optical signal) is supplied to the RZ / NRZ conversion unit 41-1, converted into the NRZ optical signal by the RZ / NRZ conversion unit 41-1, and then converted to the OLT 5-1 (of To the receiving unit (Rx).

  When the optical signal having the wavelength λ2 arrives at the input port in the decoder 40-1, as shown in FIG. 22, the FBG optical decoder for wavelength λ2 is passed through the circulator 60 and the FBG optical decoder 61 for wavelength λ1. The code λ2code1 assigned to the wavelength λ2 FBG optical decoder 62 is applied and decoded in the FBG optical decoder 62 for wavelength λ2. The decoded optical signal having the wavelength λ2 is transmitted from the output port via the wavelength λ1 FBG optical decoder 61 and the circulator 60.

(A-2-4) Operation of ONU and Signal Converter Next, the operation of the pair of ONU 9 and signal converter 10 will be described with reference to FIG.

  The downstream optical signal (RZ optical signal) dropped at the OHF node 7 that is an element of the same access network 3 is given to the RZ / NRZ conversion unit 74 via the circulator 73 of the signal converter 10 and is converted to RZ / NRZ. After being converted into the NRZ optical signal in the unit 74, it is given to the ONU 9 (the receiving unit (Rx) thereof).

  The ONU 9 (the transmission unit (Rx) thereof) instructs one of the λ1 pulse generator 70 and the λ2 pulse generator 71 to generate a pulse in response to an instruction from the corresponding OLT 5.

  The upstream optical signal (NRZ signal) transmitted from the ONU 9 (the transmission unit (Rx) thereof) is given to the NRZ / RZ conversion unit 72, where the λ1 pulse generator 70 or the λ2 pulse generator The optical pulse from 71 is applied and converted into an RZ optical signal, and the converted upstream optical signal is transmitted to the OHF node 7 which is an element of the same access network 3 via the circulator 73.

(A-2-5) Communication recovery operation when failure occurs between adjacent OHF nodes Next, a failure occurs between adjacent OHF nodes (referred to as OHF nodes 7-i and 7- (i + 1) in this section). The communication recovery operation when this occurs will be described with reference to FIG.

  As described above, in normal times, the downstream optical signal from the OLT 5 to the ONU 9 and the upstream optical signal from the ONU 9 to the OLT 5 are transferred so as to circulate counterclockwise in the metro network 2.

  When the normal state changes to a state where a failure occurs between the OHF nodes 7-i and 7- (i + 1), the upstream optical signal from the ONUs connected to the OHF nodes 7-1 to 7-i. Cannot reach the OLTs 5-1 to 5-i, and the downstream optical signals to the ONUs connected to the OHF nodes 7- (i + 1) to 7-N cannot reach the ONUs.

  The network state management unit 30 collects network state information from each of the OLTs 5-1 to 5-N to recognize that a failure has occurred between any adjacent OHF nodes. Each OLT 5-1 to 5-N monitors whether or not the upstream optical signal transmitted in response to the downstream optical signal arrives, and notifies the network state management unit 30 when it does not reach. Even if the ONU fails, the upstream optical signal may not reach. In this case, only one OLT notifies the non-delivery, so the network state management unit 30 distinguishes from the occurrence of a failure between adjacent OHF nodes. be able to.

  Hereinafter, the communication restoration operation will be specifically described. The network state management unit 30 causes all the OLTs 5-1 to 5-N to include a command signal for switching the wavelength of the upstream optical signal of the subordinate ONU to λ2 in the downstream signal from the OLT. Also at this time, all the wavelength selectors 33-1 to 33-N maintain the state of selecting the optical pulse having the wavelength λ1. That is, the downstream optical signals from all the OLTs 5-1 to 5-N including the command to switch to the wavelength λ2 are transmitted so as to circulate the metro network 2 counterclockwise.

  However, the ONUs to which the downstream optical signal reaches are only ONUs under the OHF nodes 7-1 to 7-i, and these ONUs switch to the optical pulse having the wavelength λ2 with respect to the paired signal converters. . As a result, the upstream optical signals from the ONUs under the OHF nodes 7-1 to 7-i travel around the metro network 2 in the clockwise direction and reach the corresponding OLTs 5-1 to 5-i.

  At this time, the ONUs under the OHF nodes 7-1 to 7-i can receive the downstream optical signal, and the upstream optical signal from itself reaches the corresponding OLTs 5-1 to 5-i, so that the communication is restored. It turns out that.

  The network state management unit 30 recognizes that a failure has occurred between the OHF nodes 7-i and 7- (i + 1) based on the OLTs 5-1 to 5-i that have received the upstream optical signal.

  Therefore, for the ONUs under the OHF nodes 7- (i + 1) to 7-N whose communication has not been restored, the network state management unit 30 sends the downstream optical signal of wavelength λ2 clockwise with respect to the metro network 2. Introduced to patrol. The downstream optical signal of wavelength λ2 at this time includes a command signal for switching the upstream transmission wavelength to λ1. As described above, the immediately downstream optical signal includes the command signal for switching the upstream transmission wavelength to λ2, but the ONU that is the transmission destination of the current downstream optical signal is the command signal for switching the upstream transmission wavelength to λ2. Are not received, and the upstream transmission wavelength remains λ1. Therefore, even if the current downstream optical signal includes a command signal for switching the upstream transmission wavelength to λ1, the transmission wavelength λ1 is maintained at the time of reception.

  The wavelength of the upstream optical signal from the ONU under the OHF nodes 7- (i + 1) to 7-N becomes the wavelength λ1 based on the command signal, and is added to the metro network 2 so as to be counterclockwise. .

  At this time, the ONUs under the OHF nodes 7- (i + 1) to 7-N can receive the downstream optical signal, and the upstream optical signal from itself reaches the corresponding OLTs 5- (i + 1) to 5-N. Communication is restored.

  As described above, when a failure occurs between the adjacent OHF nodes 7-i and 7- (i + 1), the connection form of the OHF nodes 7-1 to 7-N is switched from the ring connection to the cascade connection. Thus, by selecting the wavelengths of the downstream optical signal and the upstream optical signal, it is possible to restore a state in which all ONUs under the OHF nodes 7-1 to 7-N can communicate.

  As described above using the parameter “i”, which is an arbitrary integer, communication can be restored regardless of where the failure occurs in the metro network (ring network) 2.

  Here, the downstream optical signal including the command signal for switching the upstream transmission wavelength may be destined for all ONUs under the OHF node 7-n that drops the downstream optical signal, and the OHF node 7-n. A command signal for switching the upstream transmission wavelength may be given by a downstream optical signal for each subordinate ONU.

(A-2-6) Communication Restoration Operation at Failure of λ1 Pulse Generator of Route Control Unit Next, the communication restoration operation when a failure occurs in the λ1 pulse generator 31 of the route control unit 6 is shown in FIG. The description will be given with reference.

  As described above, in normal times, the downstream optical signal from the OLT 5 to the ONU 9 is transferred so as to circulate the metro network 2 counterclockwise. In order to do this, all the wavelength selectors 33-1 to 33-N in the route controller 6 select the optical pulse having the wavelength λ1 generated by the λ1 pulse generator 31. However, when a failure occurs in the λ1 pulse generator 31, the wavelength of the downstream optical signal cannot be set to λ1, and a normal downstream optical signal cannot be transmitted to the metro network 2.

  Therefore, the network state management unit 30 switches all the wavelength selection units 33-1 to 33-N to select the optical pulse having the wavelength λ2 generated by the λ2 pulse generator 32, and the normal wavelength is λ2. The downstream optical signal is introduced into the metro network 2 so as to circulate clockwise.

  Further, the network state management unit 30 instructs the OLTs 5-1 to 5-N to incorporate a command signal for switching the upstream transmission wavelength to λ2 in the downstream signal. As a result, the wavelength of the upstream optical signal from the ONU side is also switched to λ2, and the upstream optical signal having the wavelength of λ2 is added to the metro network 2 so as to circulate clockwise, and reaches the centralized station 4.

  In other words, through the control of the network state management unit 30, it switches to a clockwise ring network configuration, and all communications are restored.

  Although not shown in FIG. 6, for example, a monitor unit for monitoring the optical pulse from the λ1 pulse generator 31 is provided, and the monitor output is given to the network state management unit 30, so that the network state management unit 30 may The occurrence of a failure in the generator 31 is detected.

(A-3) Effect of Embodiment The OHF node of the embodiment is a simple and low power consumption node that can easily cope with ring connection and cascade connection.

  The OHF node according to the embodiment has a three-port configuration, and two of the OHF nodes are connected to the metro network 2, so that it is easy to add or remove the metro network 2. Further, in the route control unit 6 of the centralized station 4, a wavelength selection unit 33-n, an NRZ / RZ conversion unit 34-n, an encoder 35-n, a decoder 40-n, and an RZ / NRZ conversion unit 41 provided for each OLT unit. By preparing a unit on which all of -n are mounted, it is possible to easily add or remove.

  Since the optical network of the embodiment is obtained by connecting the OHF nodes of such an embodiment in a ring shape, the entire network can achieve low power consumption.

  In addition, since an optical network is configured by connecting a plurality of OHF nodes of the embodiment that can easily cope with ring connection and cascade connection in a ring shape, each OHF node can be appropriately switched to cascade connection. Communication can be restored by easily switching the route.

(B) Other Embodiments In the description of the above-described embodiment, various modified embodiments have been referred to. However, modified embodiments as exemplified below can be cited.

  In the above embodiment, the normal operation is shown in which all the OHF nodes 7-1 to 7-N perform the ring connection operation, but in normal operation, all the OHF nodes 7-1 to 7-N are connected in cascade. It is also possible to perform the operation. FIG. 26 is an explanatory diagram of an optical network according to such a modified embodiment.

  Under normal circumstances, for ONUs under the OHF nodes 7-1 to 7-i, λ1 is applied to the wavelength of the downstream optical signal and λ2 is applied to the wavelength of the upstream optical signal, and the OHF nodes 7- (i + 1) to 7-N For the ONU, λ2 is applied to the wavelength of the downstream optical signal and λ1 is applied to the wavelength of the upstream optical signal. In other words, for communication with the ONUs under the OHF nodes 7-1 to 7-i, the downstream optical signal circulates counterclockwise in the metro network 2, and the upstream optical signal circulates in the metro network 2 clockwise. On the other hand, for communication with ONUs under the OHF nodes 7- (i + 1) to 7-N, the downstream optical signal circulates in the metro network 2 clockwise, and the upstream optical signal circulates in the metro network 2 counterclockwise. .

  According to the modified embodiment as described above, the boundary positions (OHF nodes 7-i and OHF) on the metro network 2 where the wavelengths of the upstream optical signal and the downstream optical signal are different depending on the usage situation of the metro network 2 or the like. Node 7-(i + 1)) can be changed even in normal times. For example, many ONUs communicate using a downstream optical signal having a wavelength λ1 and an upstream optical signal having a wavelength λ2, while communicating using a downstream optical signal having a wavelength λ2 and an upstream optical signal having a wavelength λ1. If there are few ONUs, the boundary position is advanced counterclockwise to reduce the number of ONUs that are communicating using the downstream optical signal with wavelength λ1 and the upstream optical signal with wavelength λ2, while the downstream optical signal with wavelength λ2 and The number of ONUs performing communication using the upstream optical signal having the wavelength λ1 may be increased to balance the bands.

  Also in the optical network of the modified embodiment described above, the communication recovery operation when a failure occurs in the metro network 2 is the same as that in the above embodiment.

  The communication restoration operation described above is to switch all the OHF nodes 7-1 to 7-N so as to perform the cascade connection operation. However, the above-described modified embodiment can be applied to all the OHF nodes even in normal times. Since 7-1 to 7-N perform the cascade connection operation, it is possible to actually reduce the number of OHF nodes 7-1 to 7-N that execute switching. This means that even if a failure occurs, there are more ONUs that can continue communication regardless of the failure.

  In the above embodiment, the cyclic direction of the upstream optical signal and the downstream optical signal is the same in the normal state, but the cyclic direction of the upstream optical signal and the downstream optical signal may be reversed in the normal state. For example, the upstream optical signal may propagate counterclockwise and the downstream optical signal may propagate clockwise. However, when a failure occurs between adjacent OHF nodes, the state shown in FIG. 24 is finally formed as in the above embodiment.

  In the above-described embodiment, the access network 3-n and the OLT 5-n are one-to-one, but the pair of the access network 3-n and the OLT 5-n used for communication can be dynamically switched. Also good. For example, an N × N optical cross switch is provided between the route control unit 6 and a group of OLTs 5-1 to 5-N, and route control is performed according to a communication partner signal from the OLTs 5-1 to 5-N. The network state management unit 30 of the unit 6 may switch the optical cross switch so that the access network and the OLT pair can be switched dynamically.

  In the above embodiment, the wavelength (center wavelength) of the downstream optical signal to the ONU is the same in normal times, but the wavelength (center wavelength) of the downstream optical signal differs depending on the access networks 3-1 to 3-N. May be. However, it is necessary that the counterclockwise wavelength and the clockwise wavelength can be distinguished. For example, a group of N wavelengths λ1-1 to λ1-N related to a counterclockwise downstream optical signal to the access networks 3-1 to 3-N and a clockwise direction to the access networks 3-1 to 3-N It is preferable that the wavelength band with the group of N wavelengths λ2-1 to λ2-N related to the downstream optical signal does not overlap.

  Similarly, the wavelength (center wavelength) of the upstream optical signal may be different depending on the access networks 3-1 to 3-N (accordingly, the ONU). Here, the wavelengths λ1-i of the counterclockwise downstream optical signal to the access network 3-n and the counterclockwise upstream optical signal from the access network 3-n are equal, and the clockwise direction to the access network 3-n It is preferable that the wavelength λ2-i of the downstream optical signal and the clockwise upstream optical signal from the access network 3-n are equal.

  In the above embodiment, what is accommodated in the OHF nodes 7-1 to 7-N is the access networks 3-1 to 3-N, but a part of the OHF nodes 7-1 to 7-N is shown. Alternatively, all may accommodate only one ONU (not an access network).

  The method for the network state management unit 30 to recognize the occurrence of a failure between adjacent OHF nodes is not limited to the method of the above embodiment. For example, the network state management unit 30 may control to send an upstream optical signal for monitoring from the ONU and monitor the presence or absence of a failure.

  The flow of processing for recovering communication when a failure occurs between adjacent OHF nodes is not limited to the flow of the above-described embodiment. In short, the flow of processing for restoring communication that can be finally achieved in the state shown in FIG. For example, the change to the cascade connection of the OHF nodes 7- (i + 1) to 7-N may be executed before the change to the cascade connection of the OHF nodes 7-1 to 7-i.

  In the said embodiment, although the communication apparatus used for communication was what was OLT and ONU, the communication apparatus is not limited to this.

DESCRIPTION OF SYMBOLS 1 ... Optical network, 2 ... Metro network, 3-1 to 3-N ... Access network, 4 ... Toll station, 5-1 to 5-N ... OLT, 6 ... Route control part, 7, 7-1 to 7- N ... OHF node, 8-1 to 8-N ... optical coupler, 9-11 to 9-NL ... ONU, 10-11 to 10-NL ... signal converter,
20-22 ... circulator, 23 ... FBG optical encoder for wavelength λ1, 24 ... FBG optical encoder for wavelength λ2, 25 ... FBG optical decoder for wavelength λ1, 26 ... FBG optical decoder for wavelength λ2, 27, 28 ... router, 29 ... optical isolator,
DESCRIPTION OF SYMBOLS 30 ... Network state management part, 31 ... (lambda) 1 pulse generator, 32 ... (lambda) 2 pulse generator, 33-1-33-N ... wavelength selection part, 34-1-34-N ... NRZ / RZ conversion part, 35-1 35-N ... encoder, 36 ... wavelength multiplexer / demultiplexer, 37, 38 ... circulator, 39 ... optical coupler, 40-1 to 40-N ... decoder, 41-1 to 41-N ... RZ / NRZ converter, DESCRIPTION OF SYMBOLS 50 ... Circulator, 51 ... FBG type optical encoder for wavelength [lambda] 2, 52 ... FBG type optical encoder for wavelength [lambda] 1, 60 ... Circulator, 61 ... FBG type optical decoder for wavelength [lambda] 1, 62 ... FBG type optical decoder for wavelength [lambda] 2 vessel,
70 ... λ1 pulse generator, 71 ... λ2 pulse generator, 72 ... NRZ / RZ converter, 73 ... circulator, 74 ... RZ / NRZ converter.

Claims (6)

Intervene in the optical communication between the first communication device accommodated by itself and the second communication device provided in the central station terminating the ring-shaped transmission path, and then enter the ring-shaped transmission path. In one of the plurality of nodes arranged in the ring-shaped transmission path, which performs any one of addition of an optical signal, drop of a downstream optical signal from the ring-shaped transmission path, and passage of an incoming optical signal,
A first input / output port to which an optical signal having a first wavelength propagating counterclockwise through the ring-shaped transmission line is input;
A second input / output port to which an optical signal having a second wavelength propagating clockwise in the ring-shaped transmission path is input;
A third input / output port for transmitting and receiving an optical signal to and from the first communication device side accommodated by the device;
A first FBG optical decoder that decodes an optical signal having a first wavelength encoded with a first code assigned to the node; and encoded with a second code assigned to the node A decoder group in which a second FBG optical decoder for decoding an optical signal having a second wavelength is connected in cascade;
A first FBG optical encoder that encodes an optical signal having a first wavelength with the first code, and a second FBG light that encodes an optical signal having a second wavelength with the second code. A group of encoders connected in cascade with encoders;
An optical isolator that allows the optical signal to travel from the decoder group to the encoder group and prevents the optical signal from traveling in the reverse direction;
It has a PL1 port, a PR1 port, a PL2 port, and a PR2 port. When an optical signal having the first wavelength is input to the PL1 port, it is output to the PR1 port, and an optical signal having the second wavelength is input to the PL1 port. Output to the PR2 port when the optical signal having the first wavelength is input to the PL2 port, and output to the PR1 port when the optical signal having the second wavelength is input to the PL2 port. When the optical signal having the first wavelength is input to the PR1 port, the optical signal is output to the PL1 port. When the optical signal having the second wavelength is input to the PR1 port, the optical signal is output to the PL2 port. When an optical signal having the first wavelength is input, it is output to the PL1 port. When an optical signal having the second wavelength is input to the PR2 port, it is output to the PL2 port. Be one that, a first router PL2 port is connected to said first input-output port,
It has a PL1 port, a PR1 port, a PL2 port, and a PR2 port. When an optical signal having the first wavelength is input to the PL1 port, it is output to the PR1 port, and an optical signal having the second wavelength is input to the PL1 port. Output to the PR2 port when the optical signal having the first wavelength is input to the PL2 port, and output to the PR1 port when the optical signal having the second wavelength is input to the PL2 port. When the optical signal having the first wavelength is input to the PR1 port, the optical signal is output to the PL1 port. When the optical signal having the second wavelength is input to the PR1 port, the optical signal is output to the PL2 port. When an optical signal having the first wavelength is input, it is output to the PL1 port. When an optical signal having the second wavelength is input to the PR2 port, it is output to the PL2 port. The PR2 port is connected to the second input / output port, the PR1 port is connected to the PR1 port of the first router, and the PL1 port is connected to the PL1 port of the first router. Two routers,
First to third circulators each having a plurality of ports,
The first circulator provides an optical signal input from the PR2 port of the first router to the decoder group, an optical signal input from the decoder group to the third circulator,
The second circulator provides an optical signal input from the third circulator to the encoder group, an optical signal input from the encoder group to a PL2 port of the second router,
The third circulator applies an optical signal input from the first circulator to the third input / output port, and supplies an optical signal input from the third input / output port to the second circulator. A node characterized by that.   An optical network characterized in that a plurality of nodes according to claim 1 are arranged on a ring-shaped transmission line where a central station terminates.   The central station determines the wavelengths of the upstream optical signal and downstream optical signal to be used for communication between the first communication device and the second communication device, and uses the downstream optical signal to transmit the upstream optical signal to the first communication device. The optical network according to claim 2, further comprising a communication wavelength determining unit that notifies the determined wavelength. The communication wavelength determination unit, as a normal communication wavelength,
The wavelength of the upstream optical signal is determined to be the first wavelength for the first communication device accommodated in the node interposed in the ring-shaped transmission line that reaches the boundary point counterclockwise from the centralized station. And determining the wavelength of the downstream optical signal as the second wavelength,
For the first communication device accommodated in the node interposed in the ring-shaped transmission line portion that reaches the boundary point clockwise from the centralized station, the wavelength of the upstream optical signal is determined as the second wavelength. The optical network according to claim 3, wherein the wavelength of the downstream optical signal is determined as the first wavelength.   The optical network according to claim 4, wherein the communication wavelength determination unit switches the position of the boundary point according to a communication situation. The communication wavelength determining unit is
As the normal communication wavelength, both the upstream optical signal and downstream optical signal are determined to be the first or second wavelength,
When the generation unit that generates the optical signal having the determined wavelength that is the base of the downstream optical signal fails, the communication wavelength of all upstream optical signals and downstream optical signals is switched to the other wavelength. The optical network according to claim 3.

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