JP4959533B2 - Optical network - Google Patents

Description

  The present invention relates to an optical network in which a plurality of nodes are connected to each other via an optical transmission line to transmit an optical signal.

  In current optical networks, in order to compensate for signal distortion caused by dispersion in an optical fiber, a dispersion compensating fiber corresponding to the amount of chromatic dispersion between adjacent nodes is mounted on each node based on a detailed design in advance. That is, dispersion compensation is performed so that the chromatic dispersion amount becomes zero between all adjacent nodes.

  However, this means that for one optical path that relays a plurality of nodes, dispersion compensation is performed a plurality of times in units of links (here, links between nodes are called links). Dispersion compensation cost becomes enormous.

  Therefore, in the following Patent Document 1 and Patent Document 2, the chromatic dispersion amount between nodes (link unit) is measured, and the information is exchanged between the nodes or notified to the chromatic dispersion amount management server. The chromatic dispersion amount of the entire path is obtained by accumulating the chromatic dispersion amount in link units. As a result, for one optical path that relays a plurality of nodes, only dispersion compensation for compensating the accumulated chromatic dispersion amount needs to be performed. Therefore, dispersion compensation cost is lower than dispersion compensation for each link. Can be reduced.

JP 2003-121303 A JP 2004-274238 A

  In the future, when the bit rate is increased (for example, from 10 Gb / s to 40 Gb / s or 160 Gb / s), more accurate dispersion compensation is required. Even if a highly accurate chromatic dispersion amount is measured for each link, the error is accumulated in the process of accumulating the chromatic dispersion amount for each link. In addition, the chromatic dispersion amount of an optical device or the like in a relay node of an optical path cannot be ignored only by measurement in link units.

  In addition, since the amount of chromatic dispersion dynamically changes due to, for example, a change in the temperature of the optical fiber, it is not sufficient to measure the chromatic dispersion once at the time of installing the optical fiber or the device (node). Must be repeated.

  In order to solve the above-described problems, the present invention dynamically sets dispersion-compensated optical paths by measuring chromatic dispersion amounts of all optical path candidates at high speed and low cost in an optical network. It is an object of the present invention to provide an optical network that dynamically performs dispersion compensation.

  The present invention is an optical network in which a plurality of nodes are connected to each other via an optical transmission line to transmit an optical signal, and each node has its own node identification information as a measurement signal for obtaining a chromatic dispersion amount. Chromatic dispersion measurement signal transmission means to send and distribute the measurement signal from other nodes, receive a part of it, transfer the remaining part to other nodes, and obtain the chromatic dispersion amount from the received measurement signal And a chromatic dispersion measurement signal receiving means for identifying the transmission source node from the attached node identification information, and measuring the chromatic dispersion obtained by the chromatic dispersion measurement signal receiving means and the node identification information indicating the transmission source. As a result, there is provided an optical network characterized by including transmission / reception control means for attaching a node identification information of itself and transmitting to a node identified as a transmission source and receiving a measurement result from another node

  According to the present invention, it is possible to dynamically set a dispersion-compensated optical path and to dynamically implement dispersion compensation.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an optical network according to an embodiment of the present invention. FIG. 1 illustrates a ring-type optical network including nodes 111, 112, 113, and 114 and optical fibers (optical transmission lines) 121, 122, 123, and 124 that connect the respective nodes. For example, client devices 131 and 132 including IP routers and L2 switches are connected to the optical network at nodes and use paths provided by the optical network.

  FIG. 2 is a diagram showing an example of the configuration of each of the nodes 111 to 114 in FIG. 1, and the node 113 will be described as an example here. The optical signal transmission / reception units 211 and 212 are connected to, for example, a client device 132 and serve as an interface, such as input / output conversion between optical signals, and perform optical transmission with other client devices via an optical network. . The chromatic dispersion amount measurement signal receiving unit 221 receives a measurement signal for measuring the chromatic dispersion amount and analyzes it to obtain the chromatic dispersion amount. The chromatic dispersion amount measurement signal transmitter 222 transmits a measurement signal for measuring the chromatic dispersion amount. The transmission / reception control unit 231 performs transmission / reception such as notification of the measurement result of the chromatic dispersion amount with other nodes using the wavelength for monitoring control. The chromatic dispersion compensation units 211a and 212a in the optical signal transmission / reception units 211 and 212 perform chromatic dispersion compensation on the optical signal at the time of transmission or reception according to the measurement result of the chromatic dispersion amount received by the transmission / reception control unit 231.

  The optical demultiplexing unit 241 demultiplexes the optical signal received from the optical fiber 122 into optical signals having different wavelengths, and transmits them to the optical signal transmission / reception units 211 and 212, the chromatic dispersion amount measurement signal reception unit 221, and the transmission / reception control unit 231. . The optical multiplexing unit 242 multiplexes optical signals of different wavelengths transmitted by the optical signal transmission / reception units 211 and 212, the chromatic dispersion amount measurement signal transmission unit 222, and the transmission / reception control unit 231, and transmits them to the optical fiber 123.

  The coupler 251 transmits the optical signal (measurement signal) of the chromatic dispersion amount measurement signal divided into light of different wavelengths by the optical demultiplexing unit 241, the measurement signal to the chromatic dispersion amount measurement signal receiving unit 221, and the optical multiplexing unit 242. Distribute the measurement signal to the light as it is. The optical switch 252 selects either the measurement signal received from the coupler 251 or the measurement signal received from the chromatic dispersion measurement signal transmission unit 222 and transfers the selected signal to the optical multiplexing unit 242.

  The chromatic dispersion measurement signal receiver 221 and the coupler 251 are chromatic dispersion measurement signal receivers, the chromatic dispersion measurement signal transmitter 222 and the optical switch 252 are chromatic dispersion measurement signals transmitter, and the transmission / reception controller 231 controls transmission / reception. The chromatic dispersion compensation units 211a and 212a in the optical signal transmission / reception units 211 and 212 constitute a chromatic dispersion compensation unit.

  Next, the operation will be described. It is assumed that address information (node identification information), for example, an IP address, for communicating with each node on the ring is set in advance in each node 111 to 114 via the monitoring control wavelength. For example, an IP address 10.0.0.1 is set for the node 111, an IP address 10.0.0.2 is set for the node 112, an IP address 10.0.0.3 is set for the node 113, and an IP address 10.0.0.4 is set for the node 114.

  Each node communicates with adjacent nodes via the monitoring control wavelength by the transmission / reception control unit 231 to determine a node that holds the right (measurement token) to measure the amount of chromatic dispersion on the ring. For example, when the node having the smallest IP address set holds the measurement token first, the node 111 holds the measurement token. Next, each node uses the transmission / reception control unit 231 to transmit a chromatic dispersion measurement token to the node 112, the node 112 transmits the measurement token to the node 113, the node 113 transmits the measurement token to the node 114, The node 114 transmits the measurement token to the node 111, and sequentially transfers the measurement token to different nodes, so that the node holding the measurement token has the right to transmit a chromatic dispersion measurement signal only on the network. (Actually, the right to transmit a chromatic dispersion measurement signal for measuring the chromatic dispersion to another node and obtain the measurement result of the chromatic dispersion obtained from the other node) . That is, the transmission / reception control unit 231 of each node holds the measurement token when it is received, causes the chromatic dispersion measurement signal transmission unit 222 of the same node to transmit the measurement signal, and transmits the measurement token to other nodes after transmitting the measurement signal. To do.

  A case where the node 112 receives the measurement token from the node 111 and measures the clockwise chromatic dispersion amount of the ring in FIG. 1 will be described with reference to FIGS. FIG. 3 shows an example of a signal pattern of a measurement signal for measuring the chromatic dispersion amount (optical signal of the chromatic dispersion amount measurement signal), and FIG. 4 shows an operation timing chart when measuring the chromatic dispersion amount in the optical network.

  When the node 112 receives the measurement token from the node 111 (a in FIG. 4), the chromatic dispersion measurement signal transmission unit 222 and the optical multiplexing unit 242 are connected by the optical switch 252. Further, the optical signal of the chromatic dispersion amount measurement signal is transmitted from the chromatic dispersion amount measurement signal transmission unit 222. The chromatic dispersion amount is measured by using, for example, a measurement fixed wavelength f1 and a measurement fixed wavelength f2 having a different wavelength, and simultaneously transmitting a specific signal pattern as shown in FIG. The measurement is performed by measuring the reception time difference between the signal patterns of the wavelength f1 and the wavelength f2. The signal pattern shown in FIG. 3 is measured in order to specify on the receiving side that the preamble indicates the start and end of the measurement signal, and that the signal pattern having two different wavelengths transmitted simultaneously when the measurement signal is repeatedly transmitted. It contains measurement bits sufficient to guarantee the uniqueness of the signal and node identification information for identifying the source node.

  The measurement signal transmitted from the node 112 in this way (b in FIG. 4) reaches the node 113 via the optical fiber 122 and reaches the coupler 251 via the optical demultiplexing unit 241 in the node 113. . The coupler 251 distributes (divides) the measurement signal into the measurement signal of the optical signal to the chromatic dispersion measurement signal reception unit 221 and the measurement signal of the optical signal to the optical switch 252 as the optical signal. A part of the measurement signal divided into two reaches the chromatic dispersion measurement signal receiving unit 221, and the remaining part is obtained by setting the optical switch 252 to a state where the coupler 251 and the optical multiplexing unit 242 are connected. Then, it is transferred to the optical fiber 123 via the optical multiplexing unit 242. As a result, the node 114 also receives the measurement signal (c in FIG. 4). In addition, by mounting an optical signal amplification unit (not shown) that amplifies the optical signal as it is at the node, the power of the optical signal that is attenuated by distributing (dividing) by a coupler or passing through an optical fiber over a long distance is provided. It is possible to restore.

  The chromatic dispersion measurement signal receiving unit 221 receives one measurement signal divided by the coupler 251 and measures the reception time difference between the signal patterns received from the wavelengths f1 and f2, respectively, thereby obtaining the chromatic dispersion amount (FIG. 4 d). Further, the chromatic dispersion measurement signal receiving unit 221 in the node 113 includes node identification information included in the received measurement signal pattern (added at the time of transmission by the chromatic dispersion measurement signal transmission unit 222 of the node 112 as shown in FIG. 3). 1) knows that the node that transmitted the measurement signal is the node 112. The transmission / reception control unit 231 in the node 113 transmits the measurement result including the node identification information and the chromatic dispersion amount of the node 112 obtained above to the node 112 with its own node identification information (see FIG. 4). e).

  The node 114 and the node 111 also obtain the chromatic dispersion amount and the node identification information from the measurement signal received by the chromatic dispersion measurement signal receiving unit 221 by the same operation as the node 112, and the measurement result is transmitted to the node by the transmission / reception control unit 231. It transmits to 112 (fj of FIG. 4).

  As a result, the transmission / reception control unit 231 in the node 112 receives the measurement result using the transmitted measurement signal from all the other nodes on the ring, that is, the node 112 receives all the other from its own node. It is possible to obtain the chromatic dispersion amount of each path for the clockwise path to the node.

  When completing the transmission of the measurement signal, the node 112 transmits a measurement token to the next node 113 (k in FIG. 4). The node 113 that has received the measurement token transmits a measurement signal in the same manner as the node 112, and the nodes 114, 111, and 112 receive the measurement signal and transmit the measurement result to the node 113. As a result, the node 113 receives the measurement results from all the other nodes on the ring, and the node 113 has the respective routes on the clockwise path from the own node to all the other nodes. It becomes possible to know the chromatic dispersion amount of the path.

  The chromatic dispersion compensation units 211a and 212a in the optical signal transmission / reception units 211 and 212 of each node perform chromatic dispersion compensation on the optical signal at the time of transmission or reception according to the measurement result of the chromatic dispersion amount received by the transmission / reception control unit 231. . Note that there are various methods for chromatic dispersion compensation, and since these are known techniques, a detailed description thereof will be omitted.

  In this way, all nodes on the ring repeatedly execute the operation at the time of transfer of the measurement token, so that the chromatic dispersion of each path in the clockwise path from the own node to all other nodes is performed. It becomes possible to know the amount.

  Note that the same configuration is applied to the counterclockwise path, the measurement token is transferred counterclockwise (such as nodes 111 to 114, 114 to 113), and transmission / reception of measurement signals and transmission / reception of measurement results are repeated. It becomes possible for all nodes on the ring to know the chromatic dispersion amount of each path regarding the clockwise path from the node to all other nodes. Alternatively, the measurement token is only clockwise, and is shared between the measurement of the clockwise path and the measurement of the counterclockwise path in the chromatic dispersion measurement signal transmitting unit 222 and the chromatic dispersion measurement signal receiving unit 221. It is good.

  In the above embodiment, the ring type optical network has been described. However, the present invention is not limited to this, and the node identification information can be used if the delivery order of measurement tokens at a plurality of nodes in the optical network is determined in advance. Management can be implemented for any type of optical network.

  With the configuration and operation described above, in the present optical network, there is no need to accumulate chromatic dispersion amounts for each link, so there is little error with respect to the chromatic dispersion amount of the path. The measurement of the chromatic dispersion amount is the node that holds the measurement token. Start up, and the coupler distributes the optical signal as it is to multiple nodes, and includes the node identification information of the transmission source in the measurement signal, making it possible to measure in a short time and repeat the measurement at high speed It becomes possible.

It is a figure which shows the structure of the optical network by one embodiment of this invention. It is a figure which shows an example of a structure of each node of FIG. It is a figure which shows an example of the signal pattern of the measurement signal (optical signal of a chromatic dispersion amount measurement signal) for measuring the chromatic dispersion amount in the optical network by this invention. 6 is an operation timing chart when measuring the amount of chromatic dispersion in the optical network according to the present invention.

Explanation of symbols

  111-114 nodes, 121-124 optical fibers (optical transmission lines), 131, 132 client devices, 211, 212 optical signal transmission / reception units, 211a, 212a chromatic dispersion compensation units, 221 chromatic dispersion measurement signal reception units, 222 chromatic dispersion Quantity measurement signal transmission unit, 231 transmission / reception control unit, 241 optical demultiplexing unit, 242 optical multiplexing unit, 251 coupler, 252 optical switch.

Claims (5)

An optical network in which a plurality of nodes (111 to 114) are connected to each other via optical transmission paths (121 to 124) to transmit an optical signal,
Chromatic dispersion amount measurement signal transmission means (222, 252) for transmitting the measurement signal for obtaining the chromatic dispersion amount with its node identification information attached thereto;
Distributes measurement signals from other nodes, receives a part of them, transfers the remaining part to other nodes, calculates the amount of chromatic dispersion from the received measurement signals, and identifies the source node from the attached node identification information Chromatic dispersion measurement signal receiving means (221, 251) to perform,
Transmits node identification information indicating the chromatic dispersion amount and the transmission source obtained by the chromatic dispersion measurement signal receiving means to the node identified as the transmission source with the node identification information as a measurement result, and to other nodes A transmission / reception control means (231) for receiving measurement results from
An optical network characterized by comprising:   When the transmission / reception control means (231) receives the measurement token indicating the right to obtain the chromatic dispersion amount from another node, the transmission / reception control means (231) holds the measurement token, and the chromatic dispersion amount measurement signal transmission means (222) of the same node transmits the measurement signal and performs measurement. 2. The optical network according to claim 1, wherein after the signal transmission, the transmission / reception control means (231) transmits a measurement token to another node.   The optical network according to claim 1, wherein the plurality of nodes are connected in a ring shape.   The measurement signal includes a plurality of measurement signals having different wavelengths, and the chromatic dispersion amount measurement signal receiving means (221) obtains a chromatic dispersion amount based on a difference in arrival times of the plurality of measurement signals having different wavelengths. The optical network according to any one of claims 1 to 3.   Each node includes chromatic dispersion compensation means (211a, 212a) for performing chromatic dispersion compensation on an optical signal at the time of transmission or reception according to a measurement result of the chromatic dispersion amount received by the transmission / reception control means. 5. The optical network according to any one of 1 to 4.

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