WO2006080051A1 - Optical network wavelength managing method, terminal station and center station - Google Patents

Abstract

A method for managing the wavelengths of an optical network where terminal stations are connected to a center station through optical fibers to do communication by wavelength division multiplex. A terminal station monitors the wavelength used state in the optical network. When an external client signal is inputted, the terminal station transmits wavelength occupation inquiry information for inquiring the occupation of a wavelength unused in the optical network with an unused wavelength to the center station. The center station monitors the wavelength used state in the optical network. When the wavelength inquired with the wavelength occupation inquiry information can be used, the center station transmits a selected wavelength occupation permission notification for permitting the occupation of an unused wavelength to the terminal station with an unused wavelength. The terminal station occupies the permitted wavelength notified in the selected wavelength occupation permission notification and communicates a client signal in the optical network by superposing the external client signal on the wave of permitted wavelength. When the center station detects the end of communication of the client signal, the center station transmits a selected wavelength cancel notification to the terminal station. The terminal station cancels the wavelength occupation in the optical network on receiving the selected wavelength cancel notification. Thus, the wavelengths can be effectively used, and the cost increase for the communication traffic volume can be reduced.

Description

 Specification

 Optical network wavelength management method, terminal station and center station

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to an optical network wavelength management method, a terminal station, and a center station, and relates to an optical network wavelength management method and a terminal station that perform communication by wavelength division multiplexing by connecting a plurality of terminal stations and a center station with optical fibers. And the center station.

 Background art

 In conventional optical transmission, an optical fiber facility is provided for each communication ground, and point-to-point communication has been performed. In recent years, it has become possible to multiplex multiple wavelengths within a single-core optical fiber using WDM (wavelength division multiplexing) technology, but it is possible to communicate with each wavelength λ. We are communicating.

 [0003] In Patent Document 1, when communication occurs, the control station is informed of the fact to the master station, and the master station selects an unused wavelength and transmits it to the calling side and the called side, thereby enabling communication. Is described.

 [0004] In Patent Document 2, when a communication occurs, a line monitoring node detects an unused wavelength, outputs an unused signal using the wavelength, and a local node that desires transmission detects an unused signal. It is described that communication is possible by outputting a signal requesting establishment of communication at an unused wavelength.

 [0005] Patent Document 3 describes that when communication occurs, one or a plurality of unused wavelengths are reserved, and a minimum number of unused wavelengths is selected from the reserved wavelengths that are duplicated by negotiation. .

 Patent Document 1: Japanese Patent Laid-Open No. 1-160298

 Patent Document 2: JP-A-9-83491

 Patent Document 3: Japanese Patent Application Laid-Open No. 2003-318952

 Disclosure of the invention

 Problems to be solved by the invention

[0006] In recent years, traffic such as the IP communication represented by the Internet has been increasing. Even in communications that generate only one traffic, there is a problem that, in the past, optical fibers and wavelengths are fixedly used for each communication ground, and optical fibers and wavelengths are not effectively used. there were.

 [0007] Further, since the user side always occupies the optical fiber and the wavelength, there is a problem that the cost for the amount of communication traffic increases when communication traffic is generated only in a burst manner.

 [0008] The present invention has been made in view of the above points, and it is possible to effectively use the wavelength, and to reduce the increase in cost with respect to the amount of communication traffic. The overall purpose is to provide a center station.

 Means for solving the problem

In order to achieve this object, the present invention relates to a wavelength management method for an optical network in which a plurality of terminal stations and a center station are connected by optical fibers and communication is performed by wavelength division multiplexing. Wavelength occupancy inquiry information that monitors the usage of wavelengths in the optical network and inquires about the occupancy of unused wavelengths in the optical network when an external client signal is input is transmitted to the center station by the unused wavelengths. The center station monitors the wavelength usage status in the optical network, and if the wavelength inquired by the wavelength occupation inquiry information is operable, the selection to permit the occupation of the unused wavelength is permitted. A wavelength occupation permission notification is transmitted to the terminal station by the unused wavelength, and the terminal station occupies the wavelength permitted by the selected wavelength occupation permission notification and transmits the external client. The client station communicates the client signal in the optical network, and when the center station detects the end of communication of the client signal, it transmits a selective wavelength release notification to the terminal station. The wavelength occupation in the optical network is canceled when the selective wavelength cancellation notification is received.

 The invention's effect

 [0010] According to such a wavelength management method for an optical network, it is possible to effectively utilize the wavelength by occupying the wavelength only when communication occurs, and to reduce an increase in cost with respect to the amount of communication traffic. it can.

Brief Description of Drawings FIG. 1 is a block diagram of an embodiment of an optical network system to which an optical network wavelength management method of the present invention is applied.

 FIG. 2 is a flowchart of the wavelength selection operation of the terminal station.

 FIG. 3 is a flowchart of wavelength selection operation of the master station.

 FIG. 4 is a flowchart of wavelength selection cancellation operation of the terminal station.

 FIG. 5 is a flowchart of wavelength selection cancellation operation of the master station.

 [Fig.6] Wavelength selection and cancellation sequence between terminal station and master station.

Explanation of symbols

 Master station

 11, 21 Input controller

 12 WDM multiplexer

 13 Mediation department

 14 Control termination

 15, 24 Output controller

 17 N: 4 light switch section

 20 Department of Art

 22 Control signal termination

 30, 31 Optical fiber

 111, 211 EZ ○ part

 112, 212 2: 1¾ SW¾

 113, 152, 213, 242 Wavelength converter

 114, 142, 214, 232 ○ / E

 1 15, 154, 16, 215, 25, 26, 27

 151, 231, 241 Tunable wavelength filter

 153 PD 咅 | 5

BEST MODE FOR CARRYING OUT THE INVENTION

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

<Configuration of optical network system> FIG. 1 shows a block diagram of an embodiment of an optical network system to which an optical network wavelength management method of the present invention is applied. In the figure, the optical network system is configured by connecting a single master station 10 and a plurality of terminal stations 20 with optical fibers 30 and 31. A configuration may be adopted in which the downstream wavelength band and the upstream wavelength band are separated, and the downstream optical fiber 30 and the upstream optical fiber 31 are combined into one optical fiber.

[0014] The master station 10 includes an E / O unit 111 that performs electrical Z-optical conversion, a 2-input 1-output optical switch 2: 1 optical 3 unit 112, a wavelength conversion unit 1 13 that converts the wavelength of an optical signal, OZE unit 114 that performs optical Z electrical conversion, light power unit 115 that splits the optical signal, input control unit 11 provided in parallel with N circuits, WDM multiplexing unit 12 that performs wavelength multiplexing, and arbitration unit 13 , A variable wavelength filter unit 141 that varies the pass wavelength, a control termination unit 14 that includes the ○ / E unit 142, a variable wavelength filter unit 151 that varies the pass wavelength, a wavelength conversion unit 152, and a PD (photodiode) that outputs an optical signal. From the output control unit 15 provided in parallel with the N circuit, the optical power plastic unit 16, and the N input 4 output optical switch N: 4 light SW unit 17 Made up

[0015] The terminal station 20 is an E / O unit 211 that performs electrical / optical conversion, a 2-input 1-output optical switch 2

 : 1 input 3 unit 212, wavelength conversion unit 213 for converting the wavelength of optical signal, O / E unit 214 for optical / electrical conversion, input control unit 21 consisting of optical power bra unit 215 for branching optical signal, and control A signal termination unit 22, a wavelength monitoring unit 23 comprising a variable wavelength filter unit 231 that changes the passing wavelength, a ○ / E unit 232, an output control unit 24 comprising a variable wavelength filter unit 241, and a wavelength conversion unit 242, and an optical It consists of force plastic parts 25, 26, 27.

 <Wavelength selection operation of terminal station>

 FIG. 2 shows a flowchart of the wavelength selection operation of the terminal station. In the figure, the wavelength monitoring unit 23 monitors all WDM signals on the optical fiber 30 in step S 10 and notifies the control signal termination unit 22 of the presence or absence of each of the wavelengths λ 1-; The input control unit 21 determines whether or not a client signal is input in step S11. If there is a client signal input, the process proceeds to step S12.

[0016] The control signal termination unit 22 determines the unused wavelength (for example, λ 2) from the unused wavelength recognized in step S12; 1 2 and 4 and selects it as the variable wavelength filter unit 231 in step S13. Wavelength Control to fix to λ 2, control to output the wavelength λ 2 to the wavelength conversion unit 213, and control to select the output of the Ε / ◯ unit 211 to the 2: 1 light SW 212. In step S14, the control signal termination unit 22 notifies the master station 10 of the wavelength occupation inquiry information (occupation inquiry and selection of the selected wavelength λ 2) including the terminal identification ID of the own device.

 [0017] After that, in step S15, the control signal termination unit 22 determines whether or not the response from the master station 10 has timed out, and returns to step S12 when the response 'timeout is detected. Proceed to S16.

 [0018] In step S16, the control signal termination unit 22 receives the selected wavelength occupancy permission notification addressed to its own device from the master station 10 through the wavelength λ 2 and passes the variable wavelength filter unit 241 through the wavelength λ 2 in step S17. Fixed, controlled to output wavelength; 1 2 to wavelength converter 242 and controlled to select client signal input λ ζ side to 2: 1 optical SW212, and output wavelength λ 2 to wavelength converter 213 In addition, the operation of the eaves / outlet section 211 is stopped, and communication using the selected wavelength λ 2 is started.

 <Master station wavelength selection operation>

 FIG. 3 shows a flowchart of the wavelength selection operation of the master station. In the figure, the control termination unit 14 monitors the free wavelengths λ 2 and 4 recognized by the arbitration unit 13, and proceeds to step S21 when the free wavelength λ 2 changes from unused to used.

 The arbitration unit 13 controls the variable wavelength filter 141 to fix the selected wavelength to λ 2 in step S 21, and terminates the wavelength occupation inquiry information in the arbitration unit 13 in step S 22. In step S23, the arbitration unit 13 determines whether or not the wavelength 2 selected in the wavelength occupation inquiry information is an operable wavelength. If the wavelength is not inoperable, the arbitration unit 13 selects the wavelength selected by the variable wavelength filter 141 in step S24. ; The control to fix to I 2 is canceled and the process returns to step S20. If the wavelength is not operable, the process proceeds to step S25.

[0020] In step S25, the arbitration unit 13 controls the variable wavelength filter 151 to fix the selected wavelength to λ 2 and controls the wavelength conversion unit 113 to output the wavelength λ 2 to the 2: 1 light SW 112. Ε Controls to select the output of 〇 part 111, and Ν: Cross-connects the connection between the client signal input and λ 2 output to 4 optical SW part 17. The arbitration unit 13 then transmits a selection wavelength occupation permission notification including the terminal identification ID to the terminal station 20 that has made the wavelength occupation inquiry in step S26. Do this according to length 2.

 [0021] In step S27, the arbitration unit 13 cancels the control to fix the variable wavelength filter 141 to the wavelength 2 and changes the recognition of the wavelength 2 of the arbitration unit 13 (wavelength λ 2 is in use). PD153 Monitoring of the client signal input received by the ΟΖΕ unit 114, the wavelength conversion unit 113 is controlled to output the wavelength; 1 2 and the 2: 1 optical SW 112 receives the client signal. Control to select the input λ χ and shift to the data communicable state.

 <Wavelength selection cancellation operation of terminal station>

 FIG. 4 shows a flowchart of the wavelength selection cancellation operation of the terminal station. In the figure, the control signal termination unit 22 of the terminal station 20 monitors the presence / absence of a client signal in the collar unit 214 of the input control unit 21 in step S30, and proceeds to step S31 when communication of the client signal is completed.

 [0022] In step S31, the control signal termination unit 22 controls the 2: 1 optical SW 212 of the terminal station 20 to select the ΕΖ〇 part 211 side, cancels the output of the wavelength λ 2 of the wavelength conversion part 213, and the ◯ / Ε part. 21 4 Stop monitoring.

 [0023] After that, the control signal termination unit 22 detects the selection wavelength cancellation notification from the master station 10 or the input cutoff of the wavelength λ 2 in step S32, and fixes the wavelength λ 2 of the variable wavelength filter units 231, 241 in step S33. Is released, the output of wavelength converter 2 of wavelength converter 242 is released, communication is stopped, and occupation of wavelength λ 2 is released.

 <Master station wavelength selection release operation>

 FIG. 5 shows a flowchart of the wavelength selection cancellation operation of the master station. In the figure, the control termination unit 14 monitors the wavelength 2 from the terminal station 20 by monitoring the output value of the PD 153 in step S40, and detects the light stop state in step S41. If the client signal received via 114 is monitored and the input is stopped, the process proceeds to step S42.

[0024] In step S42, the arbitration unit 13 releases the fixed wavelength λ 2 of the variable wavelength filter unit 151, cancels the output of the wavelength of the wavelength conversion unit 152; 1 2 and stops monitoring the output value of the PD 153. The client signal input monitoring by the / θ unit 114 is stopped, and the 2: 1 optical SW unit 112 is changed to the selection on the side of the ΕΖ ΕΖ unit 111, and the output of the wavelength λ 2 of the wavelength conversion unit 113 is set. [0025] The arbitration unit 13 sends a selective wavelength release notification including the terminal identification ID to the terminal station 20 that has occupied the wavelength in step S43. Then, in step S44, the arbitration unit 13 releases the control force for fixing the variable wavelength filter 141 to the wavelength λ2, performs control to fix the 2: 1 light SW112 to the Ε / ○ portion 111 side, and Ν: 4 light. Performs control to release the cross connection between the client signal input of SW unit 17 and the connection between λ 2 outputs and stop the output of Ε / Ο unit 111.

 <Wavelength selection and wavelength selection release operation>

 Here, the operation to perform the wavelength selection and release of λ 4 when the operating wavelength is 1 1 and λ 3 in a 4-wavelength WDM configuration that multiplexes the wavelength; 1 1 1 14 will be described. .

FIG. 6 shows a wavelength selection / cancellation sequence between the terminal station and the master station.

Time point tl: In the terminal station 20, all the WDM signals on the optical fiber 30 are branched by the optical power plastic units 25 and 27 and supplied to the variable wavelength filter unit 231 of the wavelength monitoring unit 23. The variable wavelength filter unit 231 transmits 4 wavelengths; 1 1 1; 14 at regular intervals regardless of the presence or absence of each wavelength, and supplies the transmitted light to the ○ / E unit 232 under the control of the control signal termination unit 22 Do

[0028] The O / E unit 232 performs optical / electrical conversion to detect the existence of the wavelengths λ, and λ 3 and the absence of the wavelengths λ 2 and λ 4 force S, and the detection result is sent to the control signal termination unit 22 Notify As a result, the terminal station 20 can identify the unused wavelengths λ 2 and λ 4.

 [0029] Time t2: When communication is performed from the terminal station 20, the optical input h input from the client is branched by the optical power bra unit 215 of the input control unit 21 and is transmitted by the ○ / E unit 214. After the electrical conversion, the control signal termination unit 22 determines whether or not a client signal is input.

[0030] When it is determined that there is a client signal input, the control signal terminator 22 recognizes the unused wavelength λ 2 or λ 4 and selects an arbitrary wavelength (in this case, λ 2) to obtain a variable wavelength. The filter unit 231 is controlled to fix the selected wavelength to λ2, and the wavelength conversion unit 213 is controlled to output the wavelength λ2, and the 2: 1 light SW212 is selected to output the unit 211. In addition to controlling, wavelength occupation inquiry information including the terminal identification ID of its own device (occupation inquiry of selected wavelength λ 2 and matching) is received in accordance with the communication format predetermined for master station 10 Ε / Ο section 211 The wavelength occupation inquiry information is notified to the master station 10 via the 2: 1 optical SW 212 and the wavelength conversion unit 213. [0031] Time t3: In the master station 10, the control termination unit 14 branches all the W DM optical signals received from the optical fiber 31 by the optical power bra unit 16 and supplies the branched signal to the variable wavelength filter unit 141. The unit 141 is controlled at a constant cycle so that only the empty wavelengths 2 and 4 recognized by the arbitration unit 13 pass. As a result, the variable wavelength filter unit 141 transmits only the free wavelength λ 2 or λ 4, detects the presence or absence of each of the optical wavelengths; .

 [0032] Time t4: When the wavelength λ2 changes from unused to use from the wavelength information recognized by the arbitration unit 13, the arbitration unit 13 performs control to fix the selected wavelength to I2; the variable wavelength filter 141; The wavelength occupation inquiry information from the terminal station 20 is supplied to the arbitration unit 13 via the hook unit 142 and terminated.

 [0033] The arbitration unit 13 controls the variable wavelength filter 151 to fix the selected wavelength to λ2 when it is determined that the selected wavelength λ2 of the wavelength occupation inquiry information is not yet used and can be operated. Then, control is performed so that the wavelength λ 2 is output to the wavelength conversion unit 113, and the output of the Ε / ◯ unit 111 is selected for the 2: 1 light SW 11 2.

 [0034] At the same time, Ν: Cross-connecting the connection between the client signal input and the λ2 output using the database held in the arbitration unit 13 in the 4 optical switch unit 17, and in accordance with the communication format determined for the terminal station 20 The selected wavelength occupation permission notification including the terminal identification ID of the terminal station 20 that has made the wavelength occupation inquiry is supplied to the E / O unit 111, and this selected wavelength occupation permission notification is a 2: 1 optical SW112, wavelength conversion unit 113, N: 4 optical signal is supplied to the WDM multiplexing unit 12 by the wavelength 2 via the SW unit 17, multiplexed to the WDM signal, and notified to the terminal station 20.

 [0035] After the notification of permission to occupy the selected wavelength, the arbitration unit 13 cancels the control to fix the variable wavelength filter 141 to the wavelength λ 2 and changes the recognition of the wavelength λ 2 of the arbitration unit 13 (the wavelength λ 2 is in use). And monitoring of the output value of PD153, monitoring of the client signal input received by ΟΖΕ unit 114, and control to output wavelength; 1 2 to wavelength conversion unit 113, and 2: 1 light SW112 Next, control to select the client signal input λχ is performed, and the state shifts to the data communication ready state.

In addition, the arbitration unit 13 makes no response when the selected wavelength λ 2 of the wavelength occupation inquiry information is an inoperable wavelength such as a failure in the master station or a competition in the selected wavelength. [0037] Time point t5: The control signal termination unit 22 of the terminal station 20 receives the selected wavelength occupation permission notification addressed to the own apparatus from the master station 10 with the wavelength 2, and performs control according to the selected wavelength occupation permission notification. In the case of permission to occupy the selected wavelength, the variable wavelength filter unit 241 is fixed to pass the wavelength λ2, and the wavelength conversion unit 242 is controlled to output the wavelength; 1 2 and the 2: 1 light SW212 is input with the client signal λ Control is performed to select the ζ side, and control is performed to output the wavelength λ 2 to the wavelength conversion unit 213. Further, the operation of the 部 unit 211 is stopped, and communication using the selected wavelength λ 2 is started.

 [0038] If the control signal termination unit 22 detects no response (response 'timeout) of the master station 10, the control signal termination unit 22 returns to the time t2 and selects another unused wavelength; 14 to execute the wavelength occupation processing again. To do.

 [0039] Time t6: When the control signal termination unit 22 of the terminal station 20 monitors the client signal received via the optical power plastic unit 215 and the OZE unit 214 and communication ends, Control is performed so as to select the unit 21 1 side, the wavelength λ 2 output of the wavelength conversion unit 213 is canceled, and the monitoring of the O / E unit 214 is stopped.

 [0040] Time t7: The arbitration unit 13 of the master station 10 confirms the optical stop state of the wavelength λ 2 from the terminal station 20 by monitoring the output value of the PD 153, and passes through the light power unit 115 and the Ο / Ε unit 114. If the received client signal input stop is confirmed, and the arbitration unit 13 confirms the optical stop state from the terminal station 20 and the stop of the client signal input, the tunable filter 2 151 of the variable wavelength filter unit 151 is released. Then, cancel the wavelength 2 output of the wavelength conversion unit 152, stop the output value monitoring of the PD153, and stop the client signal input monitoring by the Ε / Ε unit 114.

 [0041] At the same time, the 2: 1 optical SW unit 112 is changed to the selection on the Ε / ○ unit 111 side, the output of the wavelength λ 2 of the wavelength conversion unit 11 3 is set, and the arbitration unit 13 sends the signal to the terminal station 20 In accordance with the determined communication format, the selected wavelength release notification including the terminal identification ID of the terminal that has occupied the wavelength is supplied to EZ0 111. This selective wavelength cancellation notification is supplied to the WDM multiplexing unit 12 via the 2: 1 optical SW112, the wavelength conversion unit 113, ^^: 4 optical 3 unit 17, and the WDM multiplexing unit 12, and is multiplexed with the WDM signal to the terminal station. 20 will be notified.

[0042] After the selection wavelength cancellation notification is transmitted, the arbitration unit 13 stops the E / O unit 1 1 1, cancels the wavelength conversion unit 1 1 3 wavelength; 1 2 output, and N: 4 optical SW unit 17 Cancel the cross-connect. [0043] Time t8: In the terminal station 20, when the control signal termination unit 22 detects the cancellation of the selected wavelength from the master station 10 or the input cutoff of the wavelength λ2, the wavelength of the variable wavelength filter units 231 and 241 is changed to 2 Release the lock, release wavelength 2 output of wavelength converter 242 and stop communication to release the occupation of wavelength λ2.

 In addition, the variable wavelength filter unit 231 transmits the four wavelengths λ 1 to λ 4 at a constant period regardless of the presence or absence of each wavelength under the control of the control signal termination unit 22, and transmits the transmitted light to Supply to part 232

 [0045] The presence of wavelengths λ, and λ 3 and the absence of wavelengths I 2 and λ 4 are detected by the collar unit 232, and the detection result is notified to the control signal termination unit 22. As a result, the terminal station 20 can identify the unused wavelengths λ 2 and λ 4.

 [0046] According to the above-described embodiment, since the wavelength can be occupied in units of communication time, it is possible to accommodate terminal stations having more than the number of wavelengths and to effectively use the wavelength resources. In addition, since the wavelength can be occupied in units of communication time, the cost for the amount of data traffic can be reduced. Furthermore, since a plurality of terminal stations can be accommodated for one wavelength, the scale of the apparatus can be reduced, and the number of accommodations can be easily increased or decreased.

 In addition, since the unused wavelength is detected autonomously by the terminal station 20, the unused wavelength is notified from other stations, whereas the wavelength occupation can be performed at high speed. Further, the difference in configuration between the terminal station 20 and the master station 10 is whether or not the arbitration unit 13 is provided, and most of the configuration of the terminal station and the master station can be shared to reduce the manufacturing cost. In FIG. 1, the terminal station 20 has only one input control unit 21 in the circuit. However, as with the master station 10, the terminal station 20 may have a configuration having a plurality of input control units, an optical SW unit, and a WDM multiplexing unit. .

 [0048] In the above embodiment, the client signal is described as being connected between the terminal station 20 and the master station 10, but the client signal may be connected between a plurality of terminal stations 20. good.

[0049] Steps S10 and S20 correspond to the monitoring means described in the claims, step S14 corresponds to the wavelength occupation inquiry means, step S17 corresponds to the wavelength occupation communication means, and steps S3 3 and S44 include the wavelength occupation. Step S26 corresponds to the selected wavelength occupation permission notification means, step S43 corresponds to the selected wavelength release notification means, and step S31 corresponds to the end of communication. Step S25 corresponds to the communication means.

Claims

The scope of the claims  [1] In connection with the wavelength management method of an optical network in which a plurality of terminal stations and a center station are connected by an optical fiber and communicated by wavelength division multiplexing,  In the terminal station, monitor the usage status of the wavelength in the optical network,  When an external client signal is input, wavelength occupation inquiry information for inquiring about the occupation of an unused wavelength in the optical network is transmitted to the center station by the unused wavelength, and the center station transmits a wavelength of the wavelength in the optical network. The usage status is monitored, and if the wavelength inquired by the wavelength occupation inquiry information is operable, a selection wavelength occupation permission notification for permitting the occupation of the unused wavelength is sent to the terminal station according to the unused wavelength. Communicate  The terminal station occupies the wavelength permitted by the selective wavelength occupation permission notification and carries the external client signal to communicate the client signal in the optical network.  When the center station detects the end of communication of the client signal, it transmits a selection wavelength cancellation notification to the terminal station by the wavelength occupied by the communication of the client signal, and the terminal station receives the selection wavelength cancellation notification. A wavelength management method for an optical network that releases wavelength occupation in the optical network. [2] In an optical network terminal station that connects multiple terminal stations and a center station with optical fibers and performs communication by wavelength division multiplexing,  Monitoring means for monitoring wavelength usage in the pre-optical network;  Wavelength occupancy inquiry means for transmitting wavelength occupancy inquiry information that inquires about the occupation of unused wavelengths in the optical network to the center station by the unused wavelengths when an external client signal is input;  Wavelength occupying communication means for communicating the client signal in the optical network by occupying the wavelength permitted by the selected wavelength occupancy permission notification received from the center station and carrying the external client signal Wavelength occupancy cancellation means for canceling the wavelength occupancy in the optical network upon receipt of the selective wavelength cancellation notification from the center station. Terminal station having.  [3] In an optical network center station that connects multiple terminal stations and a center station with optical fibers and performs communication by wavelength division multiplexing,  Monitoring means for monitoring wavelength usage in the optical network;  If the wavelength inquired by the wavelength occupation inquiry information from the terminal station by an unused wavelength is operable, the selected wavelength occupation permission notification that permits the occupation of the unused wavelength is sent by the unused wavelength. A selection wavelength cancellation notification means for transmitting to the terminal station a selection wavelength cancellation notification means for transmitting the selection wavelength cancellation notification to the terminal station according to the wavelength occupied by the communication of the client signal when detecting the end of communication of the client signal;  Center station having. [4] In the terminal station according to claim 2,  Communication termination means for terminating the communication of the client signal in the optical network when the input of the client signal from the outside stops.  Terminal station having. [5] In the center station according to claim 3,  A communication means for transmitting the selection wavelength occupation permission notification to the terminal station and performing communication of the client signal in the optical network on a wavelength that occupies an external client signal;  Center station having. [6] In the center station according to claim 5,  After the selective wavelength cancellation notification means transmits the selective wavelength cancellation notification, wavelength occupation cancellation means for canceling the wavelength occupation in the optical network is provided.  Center station having.