JP2010147545A - Optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical transmission system capable of measuring wavelength dispersion amount per optical path unit at low cost. <P>SOLUTION: An edge node 10 transmits a request for setting an optical path including wavelengths for measurement and communication, transmits a request for start of wavelength dispersion amount measurement upon receiving a response of OK, activates two fixed wavelength light sources to transmit a measurement optical signal upon receiving the response of OK, stops the two fixed wavelength light sources upon receiving a notice of completion of wavelength dispersion amount measurement, transmits a request for releasing an optical path including a measurement wavelength, and activates a variable wavelength light source so as to compensate the measured wavelength dispersion amount and starts transmission of a communication optical signal. A reception side edge node 20 confirms that three designated wavelength resources are usable upon receiving the request of setting optical path, transmits the response of OK, transmits the response of OK upon receiving the request for start of wavelength dispersion amount measurement, measures the wavelength dispersion amount upon receiving the measurement optical signal and transmits a notice of completion of wavelength dispersion amount measurement including the measured wavelength dispersion amount. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical transmission system that compensates for chromatic dispersion in units of optical paths. In this specification, an end-to-end wavelength path (transmitting end and receiving end) of optical communication is called an optical path.

  In current optical networks, in order to compensate for signal distortion caused by optical fiber dispersion, a dispersion compensation fiber according to the amount of chromatic dispersion between adjacent nodes is designed in advance (specifically, the amount of chromatic dispersion between nodes). Mounted on each node based on the measurement results. That is, dispersion compensation is performed so that the chromatic dispersion amount becomes zero between all adjacent nodes.

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

  Therefore, the chromatic dispersion amount between each node (link unit) is measured, and the information is exchanged between the nodes, or the chromatic dispersion amount management server is notified. There has been proposed an optical transmission system that is obtained by accumulating the amount of chromatic dispersion (see, for example, Patent Document 1). As a result, for one optical path that relays multiple nodes, dispersion compensation for compensating the accumulated amount of chromatic dispersion only needs to be performed on the receiving side. Compensation cost can be reduced.

  In addition, an optical transmission system has been proposed in which, after setting an optical path, the amount of chromatic dispersion is measured using a set wavelength, and the chromatic dispersion amount is compensated on the receiving side for each optical path (see, for example, Patent Document 2). As a result, the dispersion compensation cost can be reduced as compared with dispersion compensation for each link.

JP 2003-121303 A JP 2006-74698 A

  In the future, if 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.

  However, even if the chromatic dispersion amount can be measured with high accuracy for each link, the error is accumulated in the process of accumulating the chromatic dispersion amount for each link. In addition, in the link unit measurement, the chromatic dispersion amount of the optical device or the like in the relay node cannot be ignored, so that there is a problem that a highly accurate chromatic dispersion amount result cannot be obtained in the optical path unit.

  In addition, in the chromatic dispersion measurement for each optical path, the chromatic dispersion is measured using the set wavelength of the optical path (that is, the wavelength actually used for communication). A corresponding chromatic dispersion measurement function is required, and there is a problem that the chromatic dispersion measurement cost increases.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to perform chromatic dispersion measurement in units of optical paths at a low cost, and to dynamically distribute dispersion-compensated optical paths. An optical transmission system that can be set is obtained.

  An optical transmission system according to the present invention includes a transmitting side and a receiving side edge node located at an edge part of the system, and a core node located at a core part of the system between the transmitting side and the receiving side edge node, , An optical transmission system respectively connected by an optical fiber and connected by a control network, wherein the transmitting side edge node includes a wavelength light source having a first and second wavelength numbers for measurement and a third light source for communication. When the optical path setting request including the first and second wavelength numbers and the third wavelength number is transmitted and the optical path setting OK response is received, wavelength dispersion is performed. When an amount measurement start request is transmitted and a chromatic dispersion amount measurement start OK response is received, the wavelength light sources of the first and second wavelength numbers are activated and a measurement optical signal is transmitted. When the chromatic dispersion amount measurement completion notification is received, the wavelength light sources having the first and second wavelength numbers are stopped, and an optical path release request for releasing the wavelengths having the first and second wavelength numbers is transmitted. At the same time, the variable wavelength light source having the third wavelength number is activated so as to compensate the measured chromatic dispersion amount, and the transmission of the communication optical signal is started. Upon reception, it is confirmed that the specified three wavelength resources are usable, the optical path setting OK response is transmitted, and when the chromatic dispersion amount measurement start request is received, the chromatic dispersion amount measurement start OK response is transmitted. When the measurement optical signal is received, the chromatic dispersion amount is measured based on the time difference between the optical signals of the two wavelengths, and a chromatic dispersion amount measurement completion notification including the measured chromatic dispersion amount is transmitted.

  The optical transmission system according to the present invention can measure the amount of chromatic dispersion in units of optical paths at low cost, and has the effect of being able to dynamically set dispersion-compensated optical paths.

Embodiment 1 FIG.
An optical transmission system according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a block diagram showing a configuration of an optical transmission system according to Embodiment 1 of the present invention. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  1, an optical transmission system according to Embodiment 1 of the present invention includes an edge node (transmission side edge node) 10, an edge node (reception side edge node) 20 located at an edge portion of the system, and a core portion of the system. Core nodes 30, 40, and 50, client devices 60 and 70 such as routers and switches connected to the system, and a network management server 80 are provided.

  Each of the nodes 10 to 50 is connected by optical fibers 1, 2, 3, 4, and 5, respectively. The network management server 80 is for controlling the optical transmission system, and is connected to the nodes 10 to 50 and the client devices 60 and 70 by the control network 81.

  FIG. 2 is a diagram showing the configuration of the edge node of the optical transmission system according to Embodiment 1 of the present invention.

  In FIG. 2, the edge node 10 according to the first embodiment is connected to the control network 81, accommodates the node control unit 11 for controlling this node, and the client device 60, and passes through the optical transmission system. Transmitted from a plurality of client accommodation units 12 for communicating with a partner node at a desired wavelength, a chromatic dispersion amount measurement unit 14 for measuring a chromatic dispersion amount, and a client accommodation unit 12 or a chromatic dispersion amount measurement unit 14 , Optical signals of different wavelengths are multiplexed into the optical fiber 1, and conversely, optical signals of a plurality of wavelengths propagated in the optical fiber 1 are demultiplexed to the client accommodating unit 12 and the chromatic dispersion measuring unit 14 for each wavelength. The optical multiplexer / demultiplexer 16 is provided. The same applies to the edge node 20.

  Each client accommodating unit 12 includes a variable wavelength light source 13 (wavelength number # 17) for transmitting a desired wavelength. Further, the chromatic dispersion amount measuring unit 14 has two fixed wavelength light sources 15A (wavelength number # 1) and 15B (wavelength number # 100) in order to measure propagation delay differences of different wavelengths.

  FIG. 3 is a diagram showing the configuration of the core node of the optical transmission system according to Embodiment 1 of the present invention.

  In FIG. 3, the core node 30 according to the first embodiment is connected to a control network 81, and exchanges an optical signal demultiplexed by an optical multiplexer / demultiplexer with a node control unit 31 for controlling this node. The optical switch 32 and optical multiplexers / demultiplexers 33, 34, and 35 existing in units of optical fibers are provided. The core nodes 40 and 50 are the same.

  The core node 30 is not connected to the client devices 60 and 70 but is connected to the optical fibers 1, 2 and 3 for connecting to the edge node 10 and the core nodes 40 and 50.

  Next, the operation of the optical transmission system according to the first embodiment will be described with reference to the drawings. FIG. 4 is a diagram showing an operation (sequence) of the optical transmission system according to Embodiment 1 of the present invention.

  In the optical transmission system shown in FIG. 1, the wavelength dispersion amount is measured by using wavelength numbers # 1 and # 100 as two fixed wavelengths for measurement, and using two fixed wavelengths from the transmission side. Simultaneously, the same signal pattern is transmitted, and the time difference between the signal patterns is measured on the receiving side.

  In addition, it is assumed that information (for example, an IP address) for communicating with an adjacent node is set in advance in each of the nodes 10 to 50 via the control network 81. For example, information (for example, an IP address) of the edge node 10, the core node 40, and the core node 50 is set as the adjacent node in the core node 30.

  Further, it is assumed that the present optical transmission system operates based on a GMPLS (Generalized Multi Protocol Label Switching) protocol for integrated control and management of an optical transmission network. For this reason, all nodes in this optical transmission system have information about the wavelength configuration that can be used in the configuration of the entire network and each link. It is possible to derive possible wavelengths.

  The setting of the optical path connecting the client device 60 and the client device 70, that is, the setting of the optical path from the edge node 10 to the edge node 20, will be described with reference to the sequence of FIG.

  The optical path setting request is transmitted when the client apparatus 60 transmits an optical path setting request to the edge node 10 via the control network 81 and from the network management server 80 to the edge node 10. In some cases, the optical path setting sequence described below is the same.

  First, the node control unit 11 of the edge node 10 to which the optical path setting request is transmitted determines the shortest path to the edge node 20 and the wavelength used for communication, along with two fixed wavelengths used for measurement. The optical path setting request 101 from the edge node 10 to the edge node 20 is transmitted.

  The optical path setting request 101 includes # 17 as an example of a wavelength number used for communication, and # 1 and # 100 as two fixed wavelength numbers for measurement. The optical path setting request 101 transmitted by the edge node 10 is relayed to the core node 30 and the core node 40 via the control network 81, and reaches the edge node 20 while reserving three designated wavelength resources.

  Next, when the node control unit 21 (not shown) of the edge node 20 receives the optical path setting request 101, it confirms that the specified three wavelength resources are available, and returns an optical path setting OK response 102. Transmit to the edge node 10. The optical path setting OK response 102 transmitted by the edge node 20 is relayed to the core node 40 and the core node 30 via the control network 81, and reaches the edge node 10 while setting the optical switch 32 of each core node.

  Next, when the node control unit 11 of the edge node 10 receives the optical path setting OK response 102, the node control unit 11 determines that the optical path between the edge node 10 and the edge node 20 is normally set, and starts chromatic dispersion measurement. The request 103 is transmitted to the edge node 20 via the control network 81.

  Next, when receiving the chromatic dispersion amount measurement start request 103, the node control unit 21 of the edge node 20 prepares for measurement of the chromatic dispersion amount, and sends a chromatic dispersion amount measurement start OK response 104 via the control network 81. Send back.

  Next, the node control unit 11 of the edge node 10 that has received the chromatic dispersion amount measurement start OK response 104 activates the measurement-use fixed wavelength light sources 15A and 15B and transmits the measurement optical signal 105.

  Next, the chromatic dispersion measuring unit 24 (not shown) of the edge node 20 that has received the measurement optical signal 105 measures the chromatic dispersion, and the node controller 21 converts the measured chromatic dispersion into the chromatic dispersion. The edge node 10 is notified by the measurement completion notification 106.

  Next, when receiving the chromatic dispersion amount measurement completion notification 106, the node control unit 11 of the edge node 10 determines that the measurement of the chromatic dispersion amount is completed, stops the measurement fixed wavelength light sources 15A and 15B, A variable wavelength light source for communication so that an optical path release request 107 for releasing two fixed wavelengths (# 1 and # 100) for measurement is transmitted and the notified chromatic dispersion amount is pre-compensated on the transmission side 13 (# 17) is started and transmission of the optical signal for communication 108 is started.

  Note that the chromatic dispersion amount measurement start request 103, the chromatic dispersion amount measurement start OK response 104, and the chromatic dispersion amount measurement completion notification 106 are transmitted via the control network 81 to the edge nodes 10 and 20 that are both end points of the optical path. Sent and received directly between.

  The optical path release request 107 transmitted by the edge node 10 is relayed to the core node 30 and the core node 40 via the control network 81 to release the two specified fixed wavelength resources, that is, the setting of the optical switch 32 of each core node. The edge node 20 is reached while canceling.

  As described above, a dispersion-compensated optical path using the communication wavelength # 17 can be realized between the edge node 10 and the edge node 20.

  It should be noted that setting of an optical path with a plurality of wavelengths and release of an optical path with a specific wavelength are realized by extending a signaling message of the GMPLS protocol.

  In the above-described embodiment, the case where the fixed wavelength for measurement can be used has been described. However, when the fixed wavelength for measurement is in use, this is realized by waiting for a certain time until the fixed wavelength for measurement is not used.

As described above, since the chromatic dispersion amount can be measured using the fixed wavelength for measurement at the time of setting the optical path, the following effects can be obtained.
(1) Since the amount of chromatic dispersion is measured in units of optical paths, it is possible to accurately measure the amount of chromatic dispersion including the optical devices in the core node to be relayed.
(2) Since the amount of chromatic dispersion is measured with a fixed wavelength for measurement, a chromatic dispersion amount measurement function can be realized at low cost.
(3) Since the speed of the fixed wavelength for measurement may be a speed that satisfies the measurement accuracy of the chromatic dispersion amount, the measurement speed can be slower than the communication speed, and the chromatic dispersion measurement function is realized at low cost. Is possible.
(4) Since only one chromatic dispersion amount measuring unit 14 for measuring the chromatic dispersion amount is required for each edge node, the cost for measurement can be suppressed.

  In the above embodiment, a fixed wavelength is used as a wavelength for measurement, but a variable wavelength can also be used. Specifically, a variable wavelength light source is used instead of the fixed wavelength light sources 15A and 15B of the chromatic dispersion amount measuring unit 14. As a result, the amount of chromatic dispersion can be measured using a free wavelength, so there is no need to wait until the fixed wavelength for measurement becomes unused.

  In the above embodiment, the receiving side node notifies the transmitting side node of the chromatic dispersion amount and performs dispersion compensation on the transmitting side. However, the receiving side does not notify the chromatic dispersion amount. It is also possible to perform dispersion compensation.

  Further, in the above embodiment, the core nodes 30, 40 and 50 do not have the client accommodating unit 12, but the same effect can be obtained also in a node in which the core node and the edge node are merged.

It is a block diagram which shows the structure of the optical transmission system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the edge node of the optical transmission system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the core node of the optical transmission system which concerns on Embodiment 1 of this invention. It is a figure which shows operation | movement (sequence) of the optical transmission system which concerns on Embodiment 1 of this invention.

Explanation of symbols

  1-5 optical fiber, 10, 20 edge node, 11 node control unit, 12 client accommodation unit, 13 variable wavelength light source, 14 chromatic dispersion measurement unit, 15A, 15B fixed wavelength light source, 16 optical multiplexer / demultiplexer, 20 edge node , 30, 40, 50 Core node, 31 Node controller, 32 Optical switch, 33, 34, 35 Optical multiplexer / demultiplexer, 60, 70 Client device, 80 Network management server, 81 Control network.

Claims (3)

Transmitting and receiving edge nodes located at the edge of the system;
A core node located in the core part of the system between the transmitting and receiving edge nodes;
Each node is an optical transmission system connected by an optical fiber and connected by a control network,
The transmission-side edge node includes a wavelength light source having a first and second wavelength numbers for measurement and a variable wavelength light source having a third wavelength number for communication,
Transmitting an optical path setting request including the first and second wavelength numbers and the third wavelength number;
When the optical path setting OK response is received, a chromatic dispersion amount measurement start request is transmitted,
Upon receiving a wavelength dispersion amount measurement start OK response, the wavelength light sources of the first and second wavelength numbers are activated, and a measurement optical signal is transmitted.
Upon receiving the chromatic dispersion amount measurement completion notification, the wavelength light sources having the first and second wavelength numbers are stopped, and an optical path release request for releasing the wavelengths having the first and second wavelength numbers is transmitted. , Activate the variable wavelength light source of the third wavelength number so as to compensate the measured chromatic dispersion amount, and start transmitting a communication optical signal,
The receiving edge node is
Upon receiving the optical path setup request, it confirms that the specified three wavelength resources are available, and transmits the optical path setup OK response,
Upon receiving the chromatic dispersion amount measurement start request, a chromatic dispersion amount measurement start OK response is transmitted,
When the optical signal for measurement is received, the chromatic dispersion is measured based on the time difference between the optical signals of two wavelengths, and a chromatic dispersion measurement completion notification including the measured chromatic dispersion is transmitted. system. The optical transmission system according to claim 1, wherein the wavelength light sources having the first and second wavelength numbers for measurement are fixed wavelength light sources. The optical transmission system according to claim 1, wherein the wavelength light sources having the first and second wavelength numbers for measurement are variable wavelength light sources.

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