JPWO2011145218A1 - Optical communication system and communication apparatus - Google Patents

Abstract

The present invention relates to a ring network configured by nodes (ROT1, ring nodes 21 to 2n) having a ROADM function, a remote node accommodated in a node constituting the ring network, and one or more remote nodes. Of ONUs (10G-ONU510, 1G-ONU51, 10G and 1G-ONU5101) connected in a one-to-many manner via optical coupler 4, and in a node constituting a ring network Some nodes (OLT1) execute a PON control operation including uplink bandwidth allocation control for each ONU in the system.

Description

  The present invention relates to an optical communication system configured by one-to-many connection of a station side device and a subscriber side device (subscriber termination device).

  A PON (Passive Optical Network), which is one form of an optical communication system, includes a station side device (OLT: Optical Line Terminal) disposed at a central office and a subscriber termination device (ONU: Optical) disposed at a plurality of subscriber homes. Network Unit) is connected one-to-many with star couplers and optical fibers, and time division multiplexing communication is performed in the upstream direction (direction from the subscriber to the central office), and continuous communication is performed in the downstream direction. This PON is widely used as an economical communication system in which a plurality of ONUs are accommodated by one OLT by having a function of filtering a downstream signal with an ONU identifier given to a frame on the ONU side (for example, Non-patent document 1). In recent years, standardization of 10 Gbps class PON for the purpose of further increasing the communication capacity of the access network has been completed (see Non-Patent Document 2, for example). This standard is a 10 Gbps version of the 1 Gbps class PON defined by the conventional IEEE 802.3, and is accommodated in the OLT that can accommodate both the conventional 1 Gbps EPON and the 10 Gbps 10 G-EPON ONU, and this OLT. It defines the functions that the ONU should realize. Similarly, ITU-T is also standardizing 10 Gbps class PON.

  When these international standards are applied, the communication speed in the PON section becomes 10 times. In this case, two merits can be considered. The first merit is that the communication carrier operates with the same number of subscribers per OLT as the number of subscribers of a 1 Gbps class PON, so the communication capacity per subscriber increases and the subscribers It is to be able to benefit from the increased capacity of the section. The second advantage is that the communication carrier accommodates more subscribers per OLT than the 1 Gbps class PON, thereby lowering the operation cost and allowing the subscriber to be equal to or more than the 1 Gbps class PON. Service (communication capacity).

  In general, 1-Gbps class PON star couplers use a maximum of 32 to 64 branches, and the number of branches beyond that is almost realized due to the small communication capacity and loss of the optical transmission line due to the branching of the star coupler. Although not done, the number of ONUs accommodated by multi-branching has been studied conventionally. For example, in Patent Document 1, a plurality of PON signals with different wavelengths handled by a plurality of station side devices installed in a central office are coupled to a WDM coupler that multiplexes or demultiplexes each wavelength, and is multiplexed by a WDM coupler. The wavelength-division multiplexed signal is connected to a plurality of transponders capable of transmitting and receiving a PON signal having a wavelength corresponding to a specific station-side device using one optical fiber and a star coupler, and the transponder and the plurality of ONUs are connected to one light. There is disclosed a multi-branching method in which a fiber and a star coupler are connected and a PON signal is transmitted and received by time division multiplexing in the upstream direction.

JP 2008-206008 A

IEEE802.3 IEEE802.3av

  When considering the effective use of a 10 Gbps class PON device, the satisfaction of subscribers while increasing the number of subscribers per OLT and lowering the operating cost of the communication carrier, rather than just improving the communication speed per subscriber It is desirable to improve the operation mode.

  Applying this type of operation and sharing the OLT with a larger number of subscribers results in lowering the OLT power consumption (total power consumption of all OLTs on the station side) and spreading it all over the world. This is in line with the trend toward lower power consumption.

  However, only with the provisions stipulated in the international standard of 10 Gbps class (Non-Patent Document 2 above), the transmission quality deteriorates due to multi-branching, so that the distance between the currently served central office and the subscriber's home is not reduced. It is difficult to realize branching. For example, it is possible to achieve both service distance and multi-branching by increasing the power of OLT and ONU transmitters or inserting an amplifier in the fiber, but the transmission power of OLT and ONU is high. Then, operation and technical problems occur, such as a higher hazard level for access fiber laying workers and difficulty in amplifying an upstream burst signal with an amplifier.

  Further, in the method disclosed in Patent Document 1, the configuration of the station-side device is not changed from the conventional configuration, and a transponder is newly inserted, so that multi-branching is possible, but low power consumption is achieved. The problem that is difficult. Further, as a problem common to the conventional system, when a service is provided to a larger number of subscribers with one OLT, the central office device and the subscriber device are connected by a single fiber. When a fiber (especially a trunk line) breaks down, the problem that a failure area expands arises.

  The present invention has been made in view of the above, and allows power saving while permitting an increase (multi-branch) of the number of subscribers accommodated per station-side device (accommodated number of subscriber-side devices). It is another object of the present invention to obtain an optical communication system capable of improving reliability.

  In order to solve the above-described problems and achieve the object, the present invention provides a ring network configured by nodes having a ROADM function, a remote node accommodated in a node configuring the ring network, The remote node and a star network in which one or more ONUs are connected one-to-many via an optical coupler, and some of the nodes constituting the ring network operate as an OLT And performing a PON control operation including uplink bandwidth allocation control for each ONU in the system.

  The optical communication system according to the present invention has an effect that the power consumption of the system can be reduced.

FIG. 1 is a diagram illustrating a configuration example of a first embodiment of an optical communication system according to the present invention. FIG. 2 is a diagram illustrating a configuration example of the station side device (OLT). FIG. 3 is a diagram illustrating a configuration example of a remote node (RN). FIG. 4 is a diagram illustrating an example of a downlink communication control operation in the optical communication system according to the first embodiment. FIG. 5 is a diagram illustrating a configuration example of an OTU frame. FIG. 6 is a diagram illustrating an example of an uplink communication control operation in the optical communication system according to the first embodiment. FIG. 7 is a diagram illustrating an operation example in the case where the optical communication system according to the first embodiment is communicating on an active communication path. FIG. 8 is a diagram illustrating an operation example when an optical fiber fails in the optical communication system according to the first embodiment. FIG. 9 is a diagram illustrating an example of the transfer operation of the supervisory control signal in the optical communication system according to the first embodiment. FIG. 10 is a diagram illustrating an example of an operation for measuring a transmission line delay in a ring network. FIG. 11 is a diagram illustrating a measurement operation example of the transmission line delay between the ring node and the RN. FIG. 12 is a sequence diagram illustrating an example of a redundancy switching control procedure. FIG. 13 is a diagram illustrating an example of a downlink communication control operation in the optical communication system according to the second embodiment. FIG. 14 is a diagram illustrating an example of an uplink communication control operation in the optical communication system according to the second embodiment. FIG. 15 is a diagram illustrating a configuration example of the optical communication system according to the third embodiment. FIG. 16 is a diagram illustrating an example of a downlink communication control operation in the optical communication system according to the third embodiment. FIG. 17 is a diagram illustrating an example of an uplink communication control operation in the optical communication system according to the third embodiment. FIG. 18 is a diagram illustrating a configuration example of a conventional OLT-IF.

  Embodiments of an optical communication system and a communication apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In each embodiment, a network that supports two different speeds of 1 Gbps and 10 Gbps will be described, but this is merely an example to simplify understanding of the gist of the invention and limits the scope of the invention. is not. Further, a high-speed subscriber accommodation system can be included.

Embodiment 1 FIG.
<System configuration>
First, the overall configuration of the system will be described. FIG. 1 is a diagram illustrating a configuration example of a first embodiment of an optical communication system according to the present invention. As shown in the figure, the optical communication system of the present embodiment is a ring type having a configuration in which a plurality of nodes (OLT1 and ring nodes 2 ₁ to 2 _n ) are connected by a duplexed optical fiber (trunk optical fiber). A remote node (RN) 3 _{11 to} 3 _1p , 3 _{21 to} 3 _2q ,..., 3 _{n1 to} 3 _nr connected to the ring nodes 2 ₁ to 2 _n via a duplexed optical fiber; An ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G-ONU5 ₁₀₁ ) connected to the RN via an optical fiber and an optical coupler (32-branch coupler) 4 is configured. Incidentally, 10G-ONU 5 ₁₀ is capable of uplink and downlink bidirectional 10Gbps communication ONU (e.g., those defined in IEEE802.3av), 1G-ONU5 ₁ is capable of uplink and downlink bidirectional 1Gbps communication ONU 10G · 1G-ONU5 ₁₀₁ is an ONU (for example, specified in IEEE802.3av) that can communicate at an uplink of 1 Gbps and a downlink of 10 Gbps. In the following description, when “ONU” is simply described, 10G-ONU5 ₁₀ , 1G-ONU5 ₁ and 10G · 1G-ONU5 ₁₀₁ are indicated. Further, an RN may be connected to the OLT 1 and various ONUs may be connected to the RN. In this embodiment, the case where the optical coupler 4 is a 32-branch coupler will be described, but other branch numbers may be used.

  In the optical communication system shown in FIG. 1, an OLT 1 is a communication device that connects an upper network and a ring network, and includes a demultiplexing unit, two redundant OLT-IFs, a monitoring control unit, a ROADM ( Reconfigurable Optical Add / Drop Multiplexer) section. Each ring node is a communication device having the same configuration, and has a ROADM unit and a transponder. Each RN is a communication device having the same configuration, and includes a transponder and a monitoring control unit. The OLT 1 is a communication device having a function of operating as a PON OLT in addition to the function of each ring node. Conventionally, the optical communication system of the present embodiment is a communication device under each ring node (FIG. 1). The OLT functions (functions that operate as OLTs) possessed by the communication device at the location where each RN is located in are integrated into one ring node to form OLT 1.

  The demultiplexing unit of OLT 1 outputs the downstream signal light (frame) received from the upper network to one of the two OLT-IFs, and outputs the upstream signal light received from the OLT-IF to the upper network. To do. The OLT-IF executes various processes for the OLT 1 to operate as a station-side device of the PON. Details will be described separately. One of the two OLT-IFs is set as the active system and the other is set as the standby system. The monitoring control unit performs monitoring (failure detection) in the communication system, path switching when a failure is detected, and the like. The ROLT unit of the OLT 1 and each ring node extracts and adds a specific wavelength (output to the ring network) for a signal (light) flowing on the ring network. The transponder of each ring node performs wavelength conversion of the received signal light. Each RN transponder also converts the wavelength of the received signal light. In the upstream direction, a plurality of optical burst signals having different communication speeds are terminated, and light of at least one wavelength for RN and OLT 1 to communicate with each other. A process of converting to a continuous signal is also performed. On the other hand, in the downlink direction, a signal for each transponder is extracted from a signal having a predetermined communication wavelength predetermined for each RN, and a communication signal is transmitted in a predetermined frame format at a wavelength specific to the PON defined by the standard. To do.

OLT1 and RN3 ₁₁ ~3 _1p (p is the number RN which is connected under the ring node _{2 1), RN3 21 ~3 2q} (q is the number RN which is connected under the ring node _{2 2), RN3 n1 ~3 nr} ( r is the number of RNs connected under the ring node 2 _n ) is connected via one or more ring nodes 2 ₁ to 2 _n (n is the number of ring nodes constituting the ring network), and RN OTU (Optical-channel Transport Unit) frame transmission by continuous optical WDM at a higher transmission speed than the communication speed between the network and the ONUs under its control (10G-ONU, 1G-ONU, 10G / 1G-ONU) Communicate by On the other hand, the transponders accommodated in each RN and the ONUs connected to the transponders are connected in a star topology like the conventional PON and communicate by the conventional TDMA-PON system.

  As shown in the figure, the optical communication system according to the present embodiment is characterized in that the OLT function is concentrated in one of the nodes (communication devices) constituting the ring network. However, the OLT function is consolidated into one node for the sake of simplification, and it is not essential to consolidate into one. The OLT function may be distributed to some nodes.

<Configuration of OLT>
Next, the configuration of the OLT 1 will be described. FIG. 2 is a diagram illustrating a configuration example of the OLT 1 illustrated in FIG. Here, as an example, it is assumed that the OLT 1 performs PON control conforming to the IEEE standard. As illustrated, the OLT 1 includes a demultiplexing unit 11, OLT-IFs 12A and 12B, a monitoring control unit 13 including an active monitoring control unit 13A and a standby monitoring control unit 13B, and a ROADM unit 14. The OLT-IFs 12A and 12B and the monitoring control unit 13 (the active system monitoring control unit 13A and the standby system monitoring control unit 13B) are connected by a monitoring control bus. The OLT-IFs 12A and 12B and the monitoring control unit 13 constitute an OLT processing unit.

  The demultiplexing unit 11 outputs the received signal light to either one of the two OLT-IFs when receiving the downstream signal light (frame) from the upper network via the NNI (Network Network Interface). Further, the upstream signal light received from the OLT-IFs 12A and 12B is transmitted to the upper network.

  The OLT-IFs 12A and 12B have the same configuration, and either one is set as the active system and the other is set as the standby system. In FIG. 2, the OLT-IF 12A is set as the active system. The OLT-IFs 12A and 12B include a CPU 12-1, a memory 12-2 necessary for the operation of the CPU 12-1, a highly integrated PON control unit 12-3, an optical transceiver (Optical TRx) 12-4, and a packet buffer memory 12- 5, the highly integrated PON control unit 12-3 includes an L2 bridge 121, a PON control unit 122, a multiplexer (MUX) 123, a demultiplexer (DEMUX) 124, a local timer management unit 125, a PON-TS adding unit 126, and an OTN. A mapper / demapper 127 and a SER / DES 128 are provided.

  The L2 bridge 121 performs processing for bridging signals input from a plurality of NNIs via the demultiplexing unit 11 and processing for a VLAN tag. The PON control unit 122 supports a super link (LLID: Logical Link ID) in order to support a plurality of transponders, MPCP (Multi-Point Control Protocol) control, RTT (Round Trip Time) management, uplink bandwidth Performs control such as allocation control. The MUX 123 multiplexes an Ethernet (registered trademark) frame (hereinafter referred to as an Ethernet frame) input from the downstream NNI side and an Ethernet frame generated by the PON control unit 122. The DEMUX 124 sorts the upstream frame into an Ethernet frame necessary for PON control (a frame processed by the PON control unit 122) and an Ethernet frame to be transmitted to the NNI side. The local timer management unit 125 manages a 16-ns granular 32-bit counter that is normally used in PON control. The PON-TS adding unit 126 adds a time stamp to the MPCP frame. The OTN mapper / demapper 127 maps the Ethernet frame input from the NNI or the PON control unit 122 via the MUX 123 and the PON-TS adding unit 126 to the OTU frame and transmits it via the SER / DES 128. A process of demapping (decapsulating) the OTU frame to the Ethernet frame is performed. The SER / DES 128 is a serializer / deserializer necessary for an interface with an optical transceiver 12-4 connected to an OTN (Optical Transport Network) -IF. An OTU frame is a frame used in OTN.

  The optical transceiver 12-4 transmits the signal light having the wavelengths λ111 to λ1nk output from the SER / DES 128 to the ROADM unit 14 and receives the signal light having the wavelengths λ511 to λ5nk from the ROADM unit 14 to the SER / DES 128. Output.

  The active monitoring control unit 13A and the standby monitoring control unit 13B of the monitoring control unit 13 have the same configuration, and perform optical path switching control, failure detection / notification of OLT-IF, switching of OLT-IF, and the like. The active system monitoring control unit 13A and the standby system monitoring control unit 13B include a CPU 131, a memory 132 necessary for the operation of the CPU 131, a management frame transmission / reception unit 133, a TS addition unit 134, a time synchronization unit 135, an RTT calculation unit 136, An OTN mapper / demapper 137 and an optical transceiver (Optical TRx) 138 are provided.

  The management frame transmission / reception unit 133 transmits / receives a management frame via the ROADM unit 14. When a management frame is received, an OUT frame to which the management frame is mapped is input from the optical transceiver 138 to the OTN mapper / demapper 137, converted into a management frame in the ether frame format by the OTN mapper / demapper 137, and then subjected to RTT calculation. Received via the unit 136. On the other hand, at the time of transmission, the management frame transmission / reception unit 133 generates a management frame in the ether frame format and outputs it to the OTN mapper / demapper 137, where the ether frame (management frame) is mapped to the OTU frame, and then the optical transceiver 138.

  When the management frame transmission / reception unit 133 generates and transmits a management frame, the TS adding unit 134 receives information on the current time from the time synchronization unit 135 as necessary, and writes it as a time stamp in the management frame. The time synchronization unit 135 is a counter (timer) with a precision of 16 ns, and manages time, like the local timer management unit 125 of the OLT-IF described above. When the RTT calculation unit 136 confirms the contents of the management frame received via the OTN mapper / demapper 137 and determines that the RTT (delay) needs to be calculated, that is, the time information for RTT measurement is included. RTT is calculated based on the received time information and information managed by the time synchronization unit 135 (time information indicating the current time). The TS adding unit 134, the time synchronization unit 135, and the RTT calculation unit 136 realize a function (details of this function will be described later) for measuring a transmission line delay with each ring node.

  The OTN mapper / demapper 137 encapsulates the Ethernet frame input from the management frame transmission / reception unit 133 in the same process as the above-described OTN mapper / demapper 127, that is, in the downstream direction (the direction toward the ROADM unit 14). Generate an OTU frame. In the upstream direction, an OTU frame input from the optical transceiver 138 is decapsulated to extract an Ethernet frame. The optical transmitter / receiver 138 transmits / receives signal light having the wavelength λ 611 to / from the ROADM unit 14.

  The ROADM unit 14 performs extraction processing and addition processing of signal light having a specific wavelength with respect to signal light flowing through the ring network. Note that the ROADM unit 14 includes a conventional optical switch and a transponder having general functions.

<Configuration of RN>
Next, the configuration of the remote nodes (RN) 3 _{11 to} 3 _1p , 3 _{21 to} 3 _2q ,..., 3 _{n1 to} 3 _nr will be described. Each RN shown in FIG. 1 has the same configuration. Therefore, here it will be described the configuration of each RN as an example RN3 _11. Figure 3 is a diagram showing the RN3 ₁₁ configuration example of that shown in FIG. As shown, RN3 ₁₁ includes a WDM coupler 31, the monitor control unit 32 composed of a working system monitoring control unit 32A and the standby system monitoring control unit 32B, OTN transponders 33A and transponder 33 comprising a transponder 33B ₁ ~33B _n With. The monitoring control unit 32 (active system monitoring control unit 32A, standby system monitoring control unit 32B) and transponder unit 33 (OTN transponder 33A, transponders 33B _{1 to} 33B _n ) are connected by a monitoring control bus.

  The WDM coupler 31 wavelength-multiplexes upstream and downstream communication wavelengths, transmits upstream signal light with wavelengths λ421 to λ42s, and receives downstream signal light with wavelengths λ211 to λ21s.

  The active monitoring control unit 32A and the standby monitoring control unit 32B of the monitoring control unit 32 have the same configuration, and perform failure detection / notification of the transponder unit 33, wavelength mapping setting, and the like. The active system supervisory control unit 32A and the standby system supervisory control unit 32B include an optical transceiver (Optical TRx) 321, an OTN mapper / demapper 322, a management frame transceiver unit 323, a TS adding unit 324, a time synchronization unit 325, and a memory 326. And a CPU 327 that operates using the memory 326.

The optical transmitter / receiver 321 transmits / receives signal light to / from the WDM coupler 31. OTN mapper / demapper 322, the uplink (direction toward the ring nodes 2 _1), generates OTU frame encapsulates Ethernet frame input from the management frame transmission and reception unit 323, and outputs the WDM coupler 31. In the downstream direction, the OTU frame input from the WDM coupler 31 is decapsulated to extract an ether frame. Management frame transmitting and receiving unit 323 transmits and receives a management frame via a ring node 2 _1. When receiving the management frame, the OUT frame to which the management frame is mapped is input from the optical transceiver 321 to the OTN mapper / demapper 322, converted into an Ethernet frame format management frame by the OTN mapper / demapper 322, and then received. . On the other hand, at the time of transmission, the management frame transmission / reception unit 323 generates a management frame in the ether frame format and outputs the management frame to the OTN mapper / demapper 322. After the ether frame (management frame) is mapped to the OTU frame, the optical transceiver 321 is sent to the WDM coupler 31 from being transmitted after being wavelength-multiplexed by the WDM coupler 31 to the ring node 2 _1. When the management frame transmission / reception unit 323 generates and transmits a management frame, the TS adding unit 324 receives information on the current time from the time synchronization unit 325 as necessary, and writes it as a time stamp in the management frame. The time synchronizer 325 is a 16 ns precision counter (timer) and manages the time, like the OLT-IF local timer manager 125 described above. Note that the TS adding unit 324 and the time synchronization unit 325 realize a function (details of this function will be described later) for measuring a transmission line delay with the ring node accommodating the own RN. .

The OTN transponder 33A includes an optical transceiver (Optical TRx) 331 and an OTN mapper / demapper 332. The optical transmitter / receiver 331 transmits / receives signal light to / from the WDM coupler 31. In the upstream direction, the OTN mapper / demapper 332 maps signals received from the connected transponders (transponders 33B _{1 to} 33B _n ) to the OTU frame and outputs the OTU frame to the optical transceiver 331. In the downstream direction, an ether frame is extracted from the OTU frame input from the optical transceiver 331 and is output to any _{one of} the transponders 33B _{1 to} 33B _n . In the configuration example shown in FIG. 3, the OTN transponder unit 33A is not duplicated (redundant), but may be duplicated to improve reliability.

The transponders 33B _{1 to} 33B _n have the same configuration, and are an upstream dual rate burst CDR (Clock Data Recovery) 333, a dual rate burst optical receiver (Dual rate Optical Burst Rx) 334, and a 10 Gbps continuous optical transmitter (Continuous 10G-Tx). 335, 1 Gbps continuous optical transmitter (Continuous 1G-Tx) 336, and WDM coupler 337.

  The upstream dual rate burst CDR 333 and the dual rate burst optical receiver 334 send upstream signal light having a communication speed of 1 Gbps and 10 Gbps, specifically, burst signals of wavelengths λup41 and λup42 transmitted from the ONU via the WDM coupler 337. And is reproduced as a continuous signal of 1 Gbps and 10 Gbps. Also, the 10 Gbps continuous optical transmitter 335 and the 1 Gbps continuous optical transmitter 336 convert 1 Gbps and 10 Gbps Ethernet frames, which are downstream signal light transmitted from the OTN transponder 33A, to wavelengths specified by the IEEE standard, and a WDM coupler. Then, the data is transmitted to the optical fiber side to which the star coupler (optical coupler 4) is connected.

<Downlink communication control operation>
Next, the downlink communication control operation in the optical communication system according to the present embodiment will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of a downlink communication control operation.

(Procedure D1)
In the OLT, the user frame input from the higher-level network interface is demultiplexed by the demultiplexing unit (demultiplexing unit 11 shown in FIG. 2), and one of the OLT-IFs (OLT-IFs 12A and 12B shown in FIG. 2) The logical link ID (LLID) uniquely assigned to the ONU by the OLT-IF is assigned. The OLT-IF has a function of identifying which RN is an ONU under which the LLID belongs, and user data is accommodated in an OTU frame for each RN based on the LLID. As shown in FIG. 5, the OTU frame may be generated for each communication speed (corresponding to the upper case in FIG. 5), or frames having different communication speeds may be mixedly accommodated in one OTU frame (see FIG. 5). 5 corresponds to the lower case). The OTU frame is output at a fixed delay from the ROADM unit 14 to which the OLT-IF is connected, in a communication wavelength group set in advance for communication between the OLT 1 and each RN.

In Figure 4, λ111~λ11i (i is OLT1 and RN3 ₁₁ ~RN3 _1p number of wavelengths required band communication) OLT1 and ring nodes 2 ₁ wavelength for communication, λ121~λ12j (j is OLT1 and RN3 ₂₁ ~RN3 _2q is the number of wavelengths required band communication) OLT1 and ring nodes 2 ₂ wavelength for communication, λ1n1~λ1nk (k is OLT1 and RN3 _n1 ~RN3 _nr is the number of wavelengths required band communication) OLT1 and ring node 2 _n communication wavelength. The number of wavelengths actually used is determined according to the transmission capacity to be communicated between the OLT 1 and each RN.

(Procedure D2)
In the OLT 1, an MPCP Discovery frame for automatically registering an ONU and an MPCP frame for controlling an upstream burst signal from the ONU are generated by the PON control unit 122 (see FIG. 2) in the OLT-IF, It is MUXed by MUX123. These control frames (MPCP Discovery frame, MPCP frame for controlling the uplink burst signal) are also accommodated in the corresponding OTU frame based on the LLID in the same manner as the user frame, and output to the ROADM unit 14 side.

(Procedure D3)
Each ring node connected to the RN extracts a preset communication wavelength, converts the wavelength by a transponder, and then outputs the wavelength to each RN connected with a fixed delay. Each RN and ring node are connected by a point-to-point duplex fiber, and perform communication at a wavelength of at least one wavelength according to the communication capacity between each RN and the ring node (wavelength multiplexing communication). I do). For example, to extract the signal light of the ring nodes 2 ₁ at a wavelength Ramuda111～ramuda11i, wavelength transponder Ramuda211～ramuda21s, ..., is converted into Ramuda211～ramuda21t. In Figure 4, λ211~λ21s (s is OLT 1 and RN3 number of wavelengths required for ₁₁ communicate over the ring node) communication wavelength, λ211~λ21t (t of ring nodes 2 ₁ and RN3 ₁₁ is via ring node communication wavelength, λ211~λ21u (u the wavelength number) is ring node 2 ₁ and RN3 _1p required to communicate OLT1 and RN31p of the number of wavelengths required to OLT1 and RN3 ₂₁ communicate over the ring node) The communication wavelength of ring node 2 ₂ and RN3 ₂₁ , λ211 to λ21w (w is the number of wavelengths required for communication between OLT1 and RN3 _2q via the ring node) is the communication wavelength of ring node 2 ₂ and RN3 _2q , λ211 to λ21x (x is the number of wavelengths required for communication OLT1 and RN3 _n1 over the ring node) communication wavelength of the ring nodes 2 _n and RN3 _n1, λ211~λ21y (y is the OLT1 and RN3 _nr over the ring node Number of wavelengths required for communication) A communication wavelength of the ring nodes 2 _n and RN3 _nr, the number of wavelengths actually used, OLT 1 and RN are determined according to the transmission capacity to be communicated.

(Procedure D4)
In each RN, a user frame and a control frame are reproduced from an OTU frame stored in a wavelength group received from a higher-order ring node, and a frame addressed to an ONU under which transponder is assigned from the LLID assigned to the reproduced frame. Are allocated to a plurality of transponders in the RN (corresponding to the transponders 33B _{1 to} 33B _n shown in FIG. 3) with a fixed delay.

(Procedure D5)
Each transponder in each RN converts the received user frame or control frame into a wavelength for each communication speed compliant with IEEE802.3, IEEE802.3av, ITU-T standards, etc., and generates ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G-ONU5 ₁₀₁ ). In FIG. 4, the communication wavelengths between each transponder and each ONU are indicated by λ 311 and λ 312, and these indicate the wavelength for 1 Gbps and the wavelength for 10 Gbps, respectively. λ311 and λ312 are transmitted by wavelength multiplexing.

(Procedure D6)
Each ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G-ONU5 ₁₀₁ ) standardizes user frames and control frames received from higher-level RNs according to IEEE802.3, IEEE802.3av, and ITU-T standards. The predetermined operation is executed and processed.

  Note that the ODU (Optical Channel Data Unit) used between ring nodes (within the ring network) may be the same as the ODU used between the ring node and the RN, and the ring node transponder may be used for convenience of operation. You may convert and use a different floor.

<Uplink communication control operation>
Next, an uplink communication control operation in the optical communication system according to the present embodiment will be described with reference to FIG. FIG. 6 is a diagram illustrating an example of the uplink communication control operation.

(Procedure U1)
Each ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G / 1G-ONU5 ₁₀₁ ) performs Auto Discovery operation with OLT1 based on the control frame received from OLT1 via the ring node and RN. , Registered in OLT1. Thereafter, based on the time information included in the MPCP Gate frame, which is one of the control frames received from the OLT 1, uplink transmission data (user frame) and control frames are transmitted to the upper RN by time division multiplexing. These operations are those standardized by IEEE802.3, IEEE802.3av, ITU-T standards, and the like. In FIG. 6, communication wavelengths of each transponder and each ONU are indicated by λ 321 and λ 322, and these indicate a wavelength for 1 Gbps and a wavelength for 10 Gbps, respectively. λ321 and λ322 are transmitted by time division multiplexing.

(Procedure U2)
In each RN, each transponder (corresponding to the transponders 33B _{1 to} 33B _n shown in FIG. 3) converts the received upstream burst signal (the signal that has been time-division multiplexed) into a continuous signal, The OTN transponder 33A accommodates these continuous signals in an OTU frame, which is an OTN format frame, and outputs to the upper ring node with a fixed delay by an optical signal having a wavelength of at least one wavelength designated by the OLT 1 (Send by wavelength multiplexing). Similar to the downlink communication control operation, the OTU frame may be generated for each communication speed, or frames having different communication speeds may be mixedly accommodated in one OTU frame (see FIG. 5).

In Figure 6, λ421~λ42s (s is OLT 1 and RN3 number of wavelengths required for ₁₁ communicate over the ring node) communication wavelength, λ421~λ42t (t of ring nodes 2 ₁ and RN3 ₁₁ is via ring node OLT1 and RN3 _1p number of wavelengths necessary for communication) is ring node 2 ₁ and RN3 _1p communication wavelength at, λ421~λ42u (u is the number of wavelengths required to OLT1 and RN3 ₂₁ communicate over the ring node) Is the communication wavelength of ring node 2 ₂ and RN3 ₂₁ , λ421 to λ42w (w is the number of wavelengths necessary for communication between OLT1 and RN3 _2q via the ring node) is the communication wavelength of ring node 2 ₂ and RN3 _2q , λ421 to λ42x (x is the number of wavelengths necessary for communication between OLT1 and RN3 _n1 via the ring node) is the communication wavelength of ring node 2 _n and RN3 _n1 , λ421 to λ42y (y is OLT1 and RN3 _nr via the ring node) Number of wavelengths required for communication) Is the communication wavelength of the ring node 2 _n and RN3 _nr . The number of wavelengths actually used is determined according to the transmission capacity to be communicated between the OLT 1 and each RN.

(Procedure U3)
Each ring node converts the signal received from the connected RN into a signal of a predetermined wavelength group for communication with another ring node on the OLT 1 side (for communication in a ring network), Output on a ring network with a fixed delay. In Figure 6, λ511~λ51i (i is, OLT1 and RN3 ₁₁ to 3 _1p number of wavelengths necessary for communication) is OLT1 and ring nodes 2 ₁ wavelength for communication, λ521~λ52j (j is, OLT1 and RN3 ₂₁ to 3 _2q wavelength number) is OLT1 and ring nodes 2 ₂ communication wavelengths necessary for communication, λ5n1~λ5nk (k is, OLT1 and RN3 _n1 to 3 the number of wavelengths required to communicate _nr) of OLT1 and ring nodes 2 _n of It is a communication wavelength. The number of wavelengths actually used is determined according to the transmission capacity to be communicated between the OLT 1 and each RN.

(Procedure U4)
In OLT 1, the ROADM unit extracts the communication wavelength of each RN from the signal light received via each ring node, and inputs all the extracted wavelengths to both OLT-IFs. Alternatively, it is sorted for each wavelength and input to one of the OLT-IFs. The OLT-IF extracts a user frame and a control frame from the OTU frame, performs a PON control operation specified by the standard, and transfers user data to the demultiplexing unit. The demultiplexing unit transfers the signal received from the OLT-IF to the upper network side according to the multiplexing method of the upper network.

  Similar to the downlink communication control operation, the ODUs used between the ring nodes and the ODUs used between the ring nodes and the RN may be the same or different.

<Redundant switching control operation and RTT (Round Trip Time) management method>
Next, the redundant switching control operation in the optical communication system of the present embodiment and the RTT management method closely related thereto will be described with reference to FIGS.

  In general, in a TDMA-PON system, in order to efficiently collect information necessary for upstream bandwidth allocation control by controlling the time when a burst transmitted by an ONU arrives at the OLT, avoiding collision of upstream burst signals. , OLT and ONU ranging (distance measurement). Also in the optical transmission system of the present embodiment, a ranging function is necessary to avoid uplink burst collision between the RN and the ONU and to perform uplink bandwidth allocation control efficiently. In the conventional TDMA-PON system, the number of ONUs supported by the OLT is about 32 at most, so the connection between the OLT and the ONU is not made redundant. However, in the optical communication system of the present embodiment, Since the OLT MAC functions are integrated into the OLT 1, the failure area expands when a failure of the OLT-IF in the OLT 1 or a fiber break occurs. In order to solve this problem, in the optical communication system according to the present embodiment, all communication paths between the OLT and the RN are duplicated to realize high robustness of the communication network. Here, in order to realize high-speed switching of the line by duplicating the communication path, the OLT, which is a PON-specific parameter for controlling the upstream signal so as not to collide on the star coupler (optical coupler 4), It is necessary to individually measure the distance (RTT) between the ONUs not only in the active communication path but also in the standby communication path. However, the conventional method has a problem that the RTTs of the active communication channel and the standby communication channel cannot be managed simultaneously.

  FIG. 7 is a diagram illustrating an operation example when the optical communication system according to the present embodiment is communicating on an active communication path.

For example, the OLT 1 and the 10G-ONU 5 ₁₀ perform uplink and downlink communications on the communication path shown in FIG. In principle, the RTT of this communication channel can perform the same ranging as that of the conventional TDMA-PON system. That is, the OLT 1 can acquire RTT information with the 10G-ONU 5 ₁₀ by Auto Discovery defined by standards such as IEEE 802.3 and IEEE 802.3av, and the MPCP protocol. Assuming that the RTT acquired by these is RTT_Active_Total, the active downlink communication channel trip time between OLT1-ring node 2 ₁ (TT_A) and the active uplink communication channel trip time between OLT1-ring node 2 ₁ (TT_B) shown in FIG. , Ring node 2 ₁ -RN3 ₁₁ working channel round trip time (RTT_C), RN3 ₁₁ -10G-ONU5 ₁₀ working channel round trip time (RTT_D), RTT_Active_Total is expressed as Can be represented.
RTT_Active_Total = TT_A + RTT_C + RTT_D + TT_B (1)

Next, FIG. 8 shows a standby communication path in which the optical fiber used in the communication between the downlink OLT _{1 and the} ring node 21 in the optical communication system of the present embodiment communicating with the communication path in FIG. 7 fails. It is a figure which shows the operation example at the time of switching to.

The RTT_Standby_Total to be applied to the control in this case is the OLT1-ring node 2 ₁ working downlink trip time (TT_A), the OLT1-ring node 2 ₁ backup downlink trip time (TT_A ′), By RTT_Active_Total shown in 1), it can be expressed as the following equation (2).
RTT_Standby_Total = RTT_Active_Total−TT_A + TT_A ′ (2)

Therefore, in the optical communication system of the present embodiment, if the OLT 1 has means for individually measuring and holding the transmission path lengths of the redundant transmission paths, and setting a standby communication path in advance, When a transmission path failure such as a fiber fault occurs, the trip time of the fault location, the trip time of the redundant path, and the RTT after path switching can be instantly replaced from the trip time of the active system, and redundancy is facilitated. In the above example, a case has been described in which a transmission line used in communication between the downstream OLT _{1 and the} ring node 21 has failed. However, all redundant paths (duplex optical fibers) of the optical communication system according to the present embodiment have been described. Redundant switching can be performed by a similar method.

To achieve redundancy switching by the method described above, the monitoring control unit of OLT1 is self monitoring controller that ROADM unit has in the apparatus (not shown) and a ring node 2 ₁ to 2 _n ROADM unit Monitoring of A function that measures the trip time of the active system and the standby system in cooperation with the control unit (not shown) and the monitoring control unit of each RN (RN3 _{11 to} 3 _1p , RN3 _{21 to} 3 _2q , RN3 _{n1 to} 3 _nr ) have. In the OLT 1, a monitoring control unit (not shown) that performs monitoring control inside the ROADM unit and a monitoring control unit outside the ROADM unit may be combined (the monitoring control unit outside the ROADM unit shown in the figure is the ROADM unit). The monitoring control operation may also be performed.

The functions and methods necessary for measuring the communication paths of the active system and the standby system of the OLT 1 and ONU will be described below. Here, as an example, the communication channel measurements between OLT1 and 10G-ONU 5 _10.

  First, a method of transferring a supervisory control signal used for trip time measurement of the active and standby communication channels will be described. FIG. 9 is a diagram illustrating an example of the transfer operation of the supervisory control signal in the optical communication system according to the present embodiment. As shown in FIG. 9, in the monitoring control operation of the optical communication system according to the present embodiment, the monitoring control wavelength λ611 is used separately from the communication wavelength of the main signal. In the OLT 1 and each ring node constituting the ring network, the monitoring control signal which is a signal of wavelength λ611 flowing on the ring network is always dropped once and terminated by the monitoring controller. Then, the monitoring control information of the own apparatus is added to the extracted OTU frame (monitoring control signal) and updated, and the updated monitoring control signal is transferred to an adjacent node (OLT1 or ring node). If the received monitoring control signal includes information to be transferred to the RN connected to the own apparatus, the information is extracted and mapped to the OTU frame, and the wavelength for downlink monitoring control with the RN Transfer to RN at λ711. Further, as shown in the figure, the wavelength for uplink monitoring control between the OLT 1 and the ring node and the RN is λ712. This wavelength is a response to the OTU frame (monitoring control signal) from the ring node and the monitoring to be transmitted by the RN. Used to transfer control information to the ring node.

  Next, functions and means necessary for measuring the trip times of the working and standby communication channels will be described. The monitoring control unit of each ring node, each RN, and OLT 1 has a time synchronization function. Specific means for time synchronization includes GPS, IEEE802.1AS, and NTP (Network Time Protocol). The time synchronization means needs to be unified in the network, and further, for example, an accuracy equivalent to the RTT accuracy required by the accommodated TDMA-PON is required. For example, in the case of a network that accommodates G-EPON specified by IEEE802.3 and 10G-EPON specified by IEEE802.3av, an accuracy of 16 ns is required.

  Next, a method for measuring the RTT of the working and standby communication channels will be described. The trip time measurement of the active and standby communication paths is a step of measuring transmission path delays in the ring network (transmission path delays in each path (transmission path between adjacent nodes) constituting the ring network) ( Step # 1) and a step (Step # 2) of measuring a transmission line delay between each ring node and each RN connected to the ring node. By performing these steps and measuring the transmission line delay, the OLT 1 can maintain the active RTT and the transmission line delay information acquired by executing steps # 1 and # 2. Based on the above, it is possible to calculate the RTT after the path switching (backup RTT). The method for calculating the standby RTT is as described with reference to FIGS.

  The operation of steps # 1 and # 2 will be described with reference to FIGS. FIG. 10 is a diagram illustrating an operation example of measuring a transmission line delay in the ring network (operation example of Step # 1). FIG. 11 is an operation example of measuring a transmission line delay between the ring node and the RN (of Step # 2). It is a figure which shows an operation example.

(Step # 1)
As shown in FIG. 10, in the monitoring control unit of the OLT 1, the time synchronization unit, the frame generation unit, and the time stamp assigning unit generate an ether frame in which the time stamp is embedded, and store the ether frame in the OTU frame. It transmits to the adjacent ring node 2 _n at a wavelength of λ611 using the working and standby communication channels. When the monitoring control unit of the ring node 2 _n receives the frame in which the time stamp is embedded from the active and standby communication channels, the reception time information is held, and the time stamp given by the OLT 1 is obtained from the reception time information. By subtracting, RTT information between the OLT 1 and the own device (ring node 2 _n ) is acquired. Furthermore, OTU frame monitoring control unit of the ring nodes 2 _n, to the ring node 2 _n-1 adjacent, at a wavelength of λ611 with the working system and the standby system channel, with embedded RTT information previously acquired Send. A time stamp indicating the transmission time is also embedded in this OTU frame. Each ring node sequentially performs such an operation. That is, when each ring node receives a frame transmitted at a wavelength of λ611 from the active and standby communication paths, it is one of the information included in the reception time and the received frame. Based on the time stamp information indicating the frame transmission time by the transmission source node (OLT1 or ring node), the RTT with the transmission source node is calculated, and the calculated RTT information and the time stamp indicating the transmission time are added. Then, the process of transferring the received frame to the adjacent node (OLT1 or ring node) is executed. As a result, finally, the OLT 1 can acquire trip time information (transmission path delay information) of the active and standby communication paths between the ring nodes.

(Step # 2)
Here, the operation of the ring nodes 2 ₁ As an example, also performs the same operation the other ring nodes 2 ₂ to 2 _n. That is, each ring node sequentially executes the operations described below, so that the active and standby RTT information is notified to the monitoring control unit of the OLT 1.

As shown in FIG. 11, first, the monitor control unit of the ring nodes 2 _1, to the monitoring control unit of the RN3 _11, the trip time measurement request frame of the working system and the standby system channel put the OTU frame wavelength Each is transmitted at λ711. The RN3 ₁₁ monitoring control unit, the time synchronization unit, the frame generation unit and the time stamp assigning unit generates a response frame is a OTU frame embedded timestamp (send time information), sent in λ712 to the ring node 2 ₁ To do. The response frame is transmitted from each of the active and standby communication paths. Monitoring control unit of the ring nodes 2 ₁ receives the response frame from the working and standby system channel, and holds the received time information, a value obtained by subtracting the time stamp RN3 ₁₁ is applied from the reception time information Each RTT information is acquired by doubling. Ring node 2 ₁ sequentially in the same sequence, obtains the RTT information under the RN cyclically. The acquired RTT information is added to the monitoring control signal of wavelength λ611 dropped from the ring network and notified to the adjacent node (in this case, OLT1). Accordingly, OLT 1 obtains the RTT information of the working system and the protection system between the ring nodes 2 ₁ and the RN its subordinate.

  By performing the same operation for each ring node and each RN connected thereto, finally, the OLT 1 can acquire the RTT information of the active system and the standby system of all the ring nodes and the RNs under the control.

  As described above, in the optical communication system according to the present embodiment, a protocol for measuring the RTT of the standby communication path is defined in the supervisory control information (supervisory control signal) transferred in the ring network. Then, the RTT of the standby communication path is measured in advance by the method and procedure as described above. This realizes high-speed switching when a failure occurs in the active communication path.

Next, an example of redundant switching control operation will be described with reference to FIG. Here, an operation example of a case where an optical fiber failure which connects the OLT1 and ring nodes 2 ₁ (corresponding to the case shown in FIG. 8).

When the optical fiber between the OLT 1 and the ring node 2 ₁ fails and the ring node 2 ₁ detects an alarm indicating this failure, the ring node 2 ₁ sends a switch request message to the adjacent ring node 2 ₂ . It issues (transmits) and requests switching of the route (steps S11 and S12). In addition, the signal transmission path is switched to a backup path (a path that was previously used as a backup system) (step S13). When the ring node 2 ₂ receives the switching request message transmitted from the ring node 2 ₁ , the ring node 2 2 transfers the received message to the adjacent ring node 2 ₃ and switches the signal transmission path to a backup path. When each ring node sequentially executes such an operation and the switching request message transferred by the ring node 2 _n reaches the OLT 1, the ROADM unit of the OLT 1 switches the signal transmission path to the spare path and then adjoins it. A switch completion message is issued to the ring node 2 _n (step S14). Further, the ROADM unit issues an RTT change request message to the OLT-IF corresponding to the switched route (step S15). The OLT-IF that has received the RTT change request message changes to the RTT corresponding to the switched path (step S16), and returns an RTT change completion message to the ROADM unit (step S17). When the ring node 2 _n receives a response message to the switching request message transferred to the OLT 1 (the switching completion message transmitted in step S14), the ring node 2 _n transfers the received switching completion message to the adjacent ring node 2 _n-1 . Similarly, when a ring node other than the ring node 2 _n receives a switching completion message that is a response message to the switching request message, this message is transferred. When the switching completion message arrives at the ring node 21 where the failure of the transmission path (optical fiber) is detected, the switching operation of the signal transmission path is completed.

  When a failure occurs in the transmission path (active optical fiber) between the ring node and the RN under the ring node, the ring node that has detected this failure uses a standby communication path to send a message that requires switching to RN. To the standby optical fiber, and further notifies the OLT 1 that the optical fiber with the RN has failed. When receiving notification that the optical fiber between the ring node and the RN under its control has failed, the OLT 1 changes the RTT according to the notification content (switches to the RTT corresponding to the switched path). As described above, even when a failure occurs in the optical fiber between the ring node and the RN under the ring node, similarly to the case where the failure of the optical fiber occurs on the ring network, the duplex switching (standby optical fiber) is performed. Can be performed in a short time.

  As described above, in the optical communication system according to the present embodiment, the ring network configured by nodes having the ROADM function, the RN accommodated in the nodes configuring the ring network, and one or more ONUs are optical. One-to-many connection via a coupler and including a star network that performs time division multiplex transmission in the upstream direction (direction from ONU to RN), one of the nodes constituting the ring network is a station It operates as a side device (OLT) and performs distance measurement with each ONU in the system, uplink bandwidth allocation to the ONU, and the like. Also, the transmission path included in the ring network and the transmission path between the nodes constituting the ring network and the RN are duplicated, and one transmission path is set as the active system and the other as the standby system. It was decided. As a result, the following effects are obtained.

First, a reduction in power consumption of the system can be realized. The reason for this will be described. A conventional OLT-IF has a configuration as shown in FIG. 18, for example, and generally an OLT housing accommodates a plurality of OLT-IFs. On the other hand, in the optical communication system according to the present embodiment, the PON control part of the conventional OLT-IF is aggregated to some nodes (corresponding to the above-described OLT 1) in the ring network that is a metro network, and the PON in the RN The signal is directly collected in the OTN network. Therefore, the RN does not require PON control for each PON-IF, and configures the CPU, memory, and NNI side PHY (physical layer) in addition to the PON control function required in the conventional OLT. The number of parts can be greatly reduced, and the power consumption can be reduced compared to the case where the conventional configuration is adopted. The conventional configuration here is a configuration in which the ONU is directly connected to the OLT via an optical coupler, that is, each RN of the optical communication system (see FIG. 1 and the like) of the present embodiment operates as an OLT. This corresponds to a configuration in which the OLT 1 is replaced with a node similar to the ring nodes 2 ₁ to 2 _n (a node that does not have an OLT-IF).

  In addition, the reliability of the network can be improved. As described above, simply consolidating the OLT functions expands the service failure area when a transmission line failure occurs. However, in the optical communication system according to the present embodiment, a large number of ONUs are used in one OLT. The service can be accommodated, and the communication path from the station side device (OLT) to the RN is completely duplicated. Therefore, even when the OLT functions are integrated, it is possible to improve the reliability as compared with the conventional example (the system having the configuration disclosed in Patent Document 1 above). Furthermore, since the optical communication system of the present embodiment also has means for measuring the RTT of the standby communication path in advance, the communication path can be switched at a high speed when a failure is detected.

  Further, in the conventional PON system, since there was a technical problem of optical burst signal amplification, it was difficult to extend the length. However, in the optical communication system according to the present embodiment, the conventional IEEE standard PMD (Physical Medium) is used. The RN is arranged at a distance that can be supported by the Dependent (physical medium dependent unit), and the RN also has a function as a relay that converts the burst signal, which is an upstream signal from the ONU, into a continuous signal and transfers it. The transmission line up to can be easily extended.

  As described above, according to the optical communication system of the present embodiment, the integration of next-generation metro / access network technology enables power saving, high reliability by high-speed switching at the time of redundancy, and accommodation in a rural area. Prolongation is possible.

Embodiment 2. FIG.
In the first embodiment, the optical communication system having a configuration in which the communication wavelength used for communication in the ring network and the communication wavelength used for communication between the ring node and the RN are wavelength-converted by the ring node has been described. In contrast, in this embodiment, an optical communication system in which a ring node relays signals without performing wavelength conversion will be described. Note that the RTT measurement method for the active communication channel and the standby communication channel by the supervisory control and the path switching operation (redundancy switching control operation) at the time of failure detection are the same as those in the first embodiment, and thus description thereof is omitted. Further, the description of the parts common to the optical communication system of Embodiment 1 is omitted.

FIG. 13 is a diagram illustrating an example of a configuration of the optical communication system according to the second embodiment and a downlink communication control operation. As shown, the optical communication system of this embodiment, the ring nodes 2 ₁ to 2 _n of the optical communication system of the first embodiment is replaced by a ring node 2a ₁ to 2A region _n. Further, the ring node 2a ₁ to 2A region _n, is obtained by removing the transponder from the ring node 2 ₁ to 2 _n. Ring node 2a ₁ to 2A region _n of the present embodiment, the transmission in the downstream communication control operation, the signal light of specific wavelength extracted from the signal light flowing on the ring network, the RN under without wavelength conversion To do.

  The downlink communication control operation in the optical communication system of the present embodiment is as follows.

(Procedure D1a)
First, the OLT 1 performs (Procedure D1) and (Procedure D2) shown in the first embodiment, and sends a downlink signal to the ring network.

(Procedure D2a)
Ring node 2a ₁ to 2A region _n is the like of the ROADM portion WSS (the Wavelength the Select Switch), extracts the communication wavelength set in advance, each wavelength extracted, the port corresponding RN is connected (optical fiber) Distribute.

(Procedure D3a)
Each RN and ring node are connected by a point-to-point duplex fiber, and the RN extracts the signal that the connected ring node extracts from the ring network and distributes to itself. It receives with the wavelength when it is done. In FIG. 13, λ111~λ11i is a ring node 2a ₁ RN3 ₁₁ ~RN3 _1p communication wavelength, Ramuda121～ramuda12j is a ring node 2a ₂ RN3 ₂₁ ~RN3 _2q communication wavelength, Ramuda1n1～ramuda1nk and the ring node 2a _n RN3 _{n1 to} RN3 _nr are the communication wavelengths, and the number of wavelengths actually used is determined according to the transmission capacity to be communicated between the OLT 1 and the RN.

(Procedure D4a)
Each RN performs (Procedure D4) and (Procedure D5) shown in the first embodiment, and sends a downstream signal to the subordinate ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G-ONU5 ₁₀₁ ). To do. Each ONU under the RN executes (procedure D6) shown in the first embodiment.

FIG. 14 is a diagram illustrating an example of an uplink communication control operation in the optical communication system according to the second embodiment. Ring node 2a ₁ to 2A region _n of the present embodiment, in the uplink of the communication control operation, the signal light received from RN subordinate, and transmits to the ring network without wavelength conversion.

  The uplink communication control operation in the optical communication system of the present embodiment is as follows.

(Procedure U1a)
Each ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G-ONU5 ₁₀₁ ) performs the (procedure U1) described in the first embodiment, and transmits an uplink signal to a higher-order RN.

(Procedure U2a)
In each RN, the transponder converts an upstream burst signal (a signal transmitted by time division multiplexing) received from each subordinate ONU into a continuous signal, and further, converts these continuous signals into OTN format frames. It is accommodated in a certain OTU frame, and is output to an upper ring node with a fixed delay by an optical signal (wavelength multiplexed optical signal) having a wavelength of at least one wavelength designated from the OLT 1. An OTU frame may be generated for each communication speed, or frames having different communication speeds may be mixedly accommodated in one OTU frame. In the first embodiment, the optical transmitter constituting the optical transmission / reception device 331 (see FIG. 3) built in the OTN transponder 33A of each RN may be a fixed wavelength laser. In the RN, these lasers (optical transmitters) are tunable lasers. The transmission wavelength is specified by the monitoring controller and uses the wavelength.

In Figure 14, λ511~λ51i ring node 2a ₁ and RN3 ₁₁ to 3 _1p communication wavelength, Ramuda521～ramuda52j is a ring node 2a ₂ RN3 ₂₁ ~3 _2q communication wavelength, Ramuda5n1～ramuda5nk and the ring node 2a _n RN3 The communication wavelengths are _n1 to _3nr , and the number of wavelengths actually used is determined according to the transmission capacity to be communicated between the OLT 1 and each RN.

(Procedure U3a)
Each ring node outputs the signal received from the connected RN as it is to the ring network.

(Procedure U4a)
The OLT 1 performs (procedure U4) shown in the first embodiment, and transfers the uplink user data to the upper network side.

  As described above, in the optical communication system according to the present embodiment, each ring node constituting the ring network directly converts the wavelength-downstream signal extracted from the signal light flowing on the ring network (wavelength conversion). Without being transmitted), and the uplink signal received from the subordinate RN is output to the ring network as it is. Thereby, the effect similar to Embodiment 1 can be acquired. Furthermore, the transponder of each ring node can be omitted, and the network configuration can be simplified.

Embodiment 3 FIG.
In the first and second embodiments, the optical communication system in which the ring node and the RN are connected by an optical fiber has been described. However, the RN described in the first and second embodiments is directly used as a transponder of the ring node. It may be accommodated. Therefore, in this embodiment, an optical communication system having a configuration in which an RN is directly accommodated in a ring node will be described. Note that the RTT measurement method for the active communication channel and the standby communication channel by the supervisory control and the path switching operation (redundancy switching control operation) at the time of failure detection are the same as those in the first embodiment, and thus description thereof is omitted. Further, the description of the parts common to the optical communication system of Embodiment 1 is omitted.

FIG. 15 is a diagram illustrating a configuration example of the optical communication system according to the third embodiment. As shown, the optical communication system of this embodiment, the ring node 2 ₁ and RN3 ₁₁ to 3 _1p of the optical communication system of the first embodiment (see FIG. 1), the ring node 2 ₂ and RN3 ₂₁ to 3 _2q , ..., the ring nodes 2 _n and RN3 _n1 to 3 _nr, ring node 2b _1, ring node 2b _2, ..., is replaced with a ring node 2b _n.

The ring node 2b ₁ , ring node 2b ₂ ,..., Ring node 2b _n includes the ROADM unit, RN3 _{11 to} 3 _1p , RN3 _{21 to} 3 _2q ,..., RN3 _{n1 to} 3 _nr described in the first embodiment (FIG. RN # 11 to # 1p, RN # 21 to # 2q,..., RN # n1 to #nr. The transmitter of the optical transceiver mounted on the RN OTN transponder included in each ring node is assumed to be a wavelength tunable laser. In each ring node, the RN constitutes an ONU accommodation unit.

  FIG. 16 is a diagram illustrating an example of a downlink communication control operation in the optical communication system according to the third embodiment. The downlink communication control operation of the present embodiment will be described with reference to FIG.

(Procedure D1b)
First, the OLT 1 performs (Procedure D1) and (Procedure D2) shown in the first embodiment, and sends a downlink signal to the ring network.

(Procedure D2b)
The ring nodes 2b _{1 to} 2b _n extract communication wavelengths set in advance by a WSS (Wavelength Select Switch) or the like in the ROADM unit, and distribute each extracted wavelength to the corresponding RN.

(Procedure D3b)
Each RN in each ring node receives the signal extracted by the ROADM unit from the ring network and distributed to itself as the wavelength at the time of extraction. In Figure 16, distributed to λ111~λ11i ring node 2b extracted ring node 2b ₁ inside the communication wavelength to be distributed to each RN by _1, Ramuda121～ramuda12j ring node 2b each RN interior ring node 2b ₂ extracted by ₂ communication wavelength to be, Ramuda1n1～ramuda1nk is communication wavelength to be distributed to each RN interior ring node 2b _n extracted by the ring node 2b _n, the number of wavelengths actually used to communicate RN in each ring node and OLT1 It is determined according to the transmission capacity.

(Procedure D4b)
Each RN in each ring node performs (Procedure D4) and (Procedure D5) shown in the first embodiment, and transmits downstream signals to ONUs (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G- and sends it to the ONU5 _101). Each ONU under the RN executes (procedure D6) shown in the first embodiment.

  FIG. 17 is a diagram illustrating an example of an uplink communication control operation in the optical communication system according to the third embodiment. The uplink communication control operation of the present embodiment will be described with reference to FIG.

(Procedure U1b)
Each ONU (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G · 1G-ONU5 ₁₀₁ ) implements (procedure U1) shown in the first embodiment, and sends an upstream signal to an upper RN (RN in the ring node). Send to.

  In each RN in each ring node, the transponder converts the upstream burst signal received from each subordinate ONU into a continuous signal, and further, these continuous signals are accommodated in an OTU frame that is an OTN format frame. Then, an optical signal having a wavelength of at least one wavelength designated by the OLT 1 is output to the ROADM unit in the same ring node with a fixed delay. An OTU frame may be generated for each communication speed, or frames having different communication speeds may be mixedly accommodated in one OTU frame.

In Figure 17, the communication wavelength λ511~λ51i is assigned to each RN in the ring node 2b _1, communication wavelength λ521~λ52j is assigned to each RN in the ring node 2b _2, λ5n1~λ5nk ring node 2b _n The number of wavelengths actually used is determined according to the transmission capacity to be communicated between the OLT 1 and each RN (RN in the ring node).

  As described above, in the optical communication system according to the present embodiment, the ring node configuring the ring network directly accommodates the RN described in the first embodiment. Thereby, the effect similar to Embodiment 1 can be acquired. Further, when an RN is arranged in the vicinity of a ring node, an optimal network that does not require an extra fiber can be configured.

Note that this embodiment can be mixed with Embodiment 1 and Embodiment 2, and the network can be configured flexibly. For example, a configuration in which only the ring node 2 ₁ and RN 3 _{11 to} 3 _{1p in} the optical communication system (see FIG. 1) of the _first embodiment are replaced with the ring node 2b ₁ described in the present embodiment, Only the ring node 2a ₂ and RN 3 _{21 to} 3 _2q in the optical communication system (see FIG. 13) can be replaced with the ring node 2b ₂ described in the present embodiment.

  As described above, the optical communication system according to the present invention is useful for a communication system that performs PON control, and is particularly suitable for an optical communication system that includes a plurality of one-to-many connected networks.

1 OLT
2 ₁ , 2 ₂ , 2 _n , 2a ₁ , 2a ₂ , 2a _n , 2b ₁ , 2b ₂ , 2b _n ring node 3 ₁₁ , 3 _1p , 3 ₂₁ , 3 _2q , 3 _n1 , 3 _nr remote node (RN)
4 Optical coupler 5 ₁ 1G-ONU
5 ₁₀ 10G-ONU
5 ₁₀₁ 10G ・ 1G-ONU
11 Demultiplexer 12A, 12B OLT-IF
12-1, 131, 327 CPU
12-2, 132, 326 Memory 12-3 Highly integrated PON control unit 12-4, 138, 321, 331 Optical transceiver (Optical TRx)
12-5 Packet buffer memory 121 L2 bridge 122 PON control unit 123 Multiplexer (MUX)
124 Demultiplexer (DEMUX)
125 Local timer management unit 126 PON-TS giving unit 127, 137, 322, 332 OTN mapper / demapper 128 SER / DES
13, 32 Monitoring control unit 13A, 32A Active system monitoring control unit 13B, 32B Standby system monitoring control unit 133, 323 Management frame transmission / reception unit 134, 324 TS adding unit 135, 325 Time synchronization unit 136 RTT calculation unit 14 ROADM unit 31, 337 WDM coupler 33 transponder unit 33A OTN transponder 33B ₁ , 33B _n transponder 333 Upstream dual rate burst CDR (Clock Data Recovery)
334 Dual rate optical burst receiver (Dual rate Optical Burst Rx)
335 10Gbps Continuous Optical Transmitter (Continuous 10G-Tx)
336 1Gbps Continuous Optical Transmitter (Continuous 1G-Tx)

Claims (15)

A ring network composed of nodes having ROADM functions;
A remote node accommodated in a node constituting the ring network;
A star network in which the remote node and one or more ONUs are connected one-to-many via an optical coupler;
Including
An optical communication system characterized in that a part of the nodes constituting the ring network operates as an OLT and performs a PON control operation including uplink bandwidth allocation control for each ONU in the system. . 2. The optical communication system according to claim 1, wherein the station side device and the remote node, which are nodes operating as the OLT, communicate with each other by setting data and control information in an OTU frame. The remote node converts the optical burst signal received from each connected ONU into an optical continuous signal, and wavelength-multiplexes and transmits each optical continuous signal after conversion. An optical communication system according to claim 1. The station side device which is a node operating as the OLT
ROADM means for implementing the ROADM function by executing processing for extracting signal light of a specific wavelength from the ring network and processing for outputting signal light of a specific wavelength to the ring network;
OLT processing means for executing a PON control operation including uplink bandwidth allocation control for each ONU in the system and a monitoring control operation including a transmission line delay measurement with each ONU;
The optical communication system according to claim 1, 2, or 3. Each transmission path connecting the nodes and each transmission path connecting the node and the remote node under the node are configured by duplexed optical fibers, and the station side device and the remote node are duplexed. One of the optical fibers is set to the active system and the other is set to the standby system to perform communication.
The OLT processing means measures and holds each transmission line delay with each ONU when using one of the duplexed optical fibers in the monitoring control operation and uses the other. In this case, the transmission line delay between each ONU is measured and held, and the transmission line delay corresponding to the optical fiber used as the active system is used in the PON control operation. Item 5. The optical communication system according to Item 4. The nodes constituting the ring network are:
When a communication failure in a transmission path with an adjacent node on the ring network or a communication failure in a transmission path with a subordinate remote node is detected, a message indicating that is transmitted to the station side device. At the same time, change the settings to communicate using the optical fiber that was previously used as a standby system,
Also, when a message indicating communication failure detection is received, this message is transferred to the station side device, and the setting is changed so that communication is performed using the optical fiber that has been used as a backup system until then. The optical communication system according to claim 5. The nodes constituting the ring network are:
A transponder that converts the wavelength of the signal light of a specific wavelength included in the signal light received in the ring network and converts the wavelength of the signal light received from the remote node under control thereof,
The optical communication system according to any one of claims 1 to 6, further comprising: A ring network including a node having a ROADM function and having a plurality of ONU accommodating means for accommodating a plurality of ONUs via an optical coupler;
An optical communication system characterized in that a part of the nodes constituting the ring network operates as an OLT and performs a PON control operation including uplink bandwidth allocation control for each ONU in the system. . 9. The ONU accommodating means provided in the station side device and other nodes that are nodes operating as the OLT sets data and control information in the OTU frame and communicates with each other. Optical communication system. The ONU accommodating means converts the optical burst signal received from each connected ONU into an optical continuous signal, and wavelength-multiplexes and transmits each optical continuous signal after conversion. 9. The optical communication system according to 9. The station side device which is a node operating as the OLT
ROADM means for implementing the ROADM function by executing processing for extracting signal light of a specific wavelength from the ring network and processing for outputting signal light of a specific wavelength to the ring network;
OLT processing means for executing a PON control operation including uplink bandwidth allocation control for each ONU in the system and a monitoring control operation including a transmission line delay measurement with each ONU;
The optical communication system according to claim 8, 9 or 10. Each transmission path connecting the nodes and each transmission path connecting the node and the remote node under the node are configured by duplexed optical fibers, and the station side device and the remote node are duplexed. One of the optical fibers is set to the active system and the other is set to the standby system to perform communication.
The OLT processing means measures and holds each transmission line delay with each ONU when using one of the duplexed optical fibers in the monitoring control operation and uses the other. In this case, the transmission line delay between each ONU is measured and held, and the transmission line delay corresponding to the optical fiber used as the active system is used in the PON control operation. Item 12. The optical communication system according to Item 11. The nodes constituting the ring network are:
When a communication failure is detected in a transmission path with an adjacent node on the ring network, a message indicating that is transmitted to the station side device and an optical fiber that has been used as a standby system is used. Change the settings to communicate,
Also, when a message indicating communication failure detection is received, this message is transferred to the station side device, and the setting is changed so that communication is performed using the optical fiber that has been used as a backup system until then. The optical communication system according to claim 12. A ring network, a remote node accommodated in a node constituting the ring network, and a star network in which the remote node and one or more ONUs are connected one-to-many via an optical coupler. In the optical communication system including the communication system, the ring type network is configured together with another node having a ROADM function,
ROADM means for implementing the ROADM function by executing processing for extracting signal light of a specific wavelength from the ring network and processing for outputting signal light of a specific wavelength to the ring network;
OLT processing means for executing a PON control operation including uplink bandwidth allocation control for each ONU in the system and a monitoring control operation including a transmission line delay measurement with each ONU;
A communication apparatus comprising: In an optical communication system including a ring network, a communication apparatus that constitutes the ring network together with another node having a ROADM function and having a plurality of ONU accommodating means for accommodating a plurality of ONUs via an optical coupler. There,
ROADM means for implementing the ROADM function by executing processing for extracting signal light of a specific wavelength from the ring network and processing for outputting signal light of a specific wavelength to the ring network;
OLT processing means for executing a PON control operation including uplink bandwidth allocation control for each ONU in the system and a monitoring control operation including a transmission line delay measurement with each ONU;
A communication apparatus comprising:

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