WO2015060325A1 - プロテクション方法及び光通信システム - Google Patents
プロテクション方法及び光通信システム Download PDFInfo
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- WO2015060325A1 WO2015060325A1 PCT/JP2014/078025 JP2014078025W WO2015060325A1 WO 2015060325 A1 WO2015060325 A1 WO 2015060325A1 JP 2014078025 W JP2014078025 W JP 2014078025W WO 2015060325 A1 WO2015060325 A1 WO 2015060325A1
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- child node
- termination device
- signal light
- logically connected
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0287—Protection in WDM systems
- H04J14/0297—Optical equipment protection
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
- H04J14/0282—WDM tree architectures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0287—Protection in WDM systems
- H04J14/0293—Optical channel protection
- H04J14/0295—Shared protection at the optical channel (1:1, n:m)
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q11/0066—Provisions for optical burst or packet networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0016—Construction using wavelength multiplexing or demultiplexing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0037—Operation
- H04Q2011/0043—Fault tolerance
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/0079—Operation or maintenance aspects
- H04Q2011/0081—Fault tolerance; Redundancy; Recovery; Reconfigurability
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
- H04Q2213/1301—Optical transmission, optical switches
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
- H04Q2213/13295—Wavelength multiplexing, WDM
Definitions
- the present invention relates to a protection method in an optical communication system and an optical communication system capable of realizing the protection method.
- FTTH Fiber To The Home
- Most of the FTTH services accommodate multiple subscriber-side devices (ONU: Optical Network Unit) by time division multiplexing (TDM: Time Division Multiplexing) of one accommodating station-side device (OSU: Optical Subscriber Unit).
- TDM Time Division Multiplexing
- OFD station-side device
- PON Passive Optical Network
- the system band is shared between ONUs based on the dynamic band allocation calculation in the OSU, and each ONU 200 is transmitted only within the transmission permission time notified from the OSU 51 as shown in FIG. Intermittent transmission of signal light is prevented by transmitting the signal light intermittently.
- the current main systems are GE-PON (Gigabit Ethernet (registered trademark) PON) and G-PON (Gigabit-capable PON), which have a transmission speed of gigabit. Due to the appearance of applications for uploading / downloading, etc., there is a demand for further increasing the capacity of the PON system.
- GE-PON Gigabit Ethernet (registered trademark) PON
- G-PON Gigabit-capable PON
- FIG. 2 is an example of WDM / TDM-PON in which WDM technology is combined with TDM-PON.
- Each ONU 200a is fixedly assigned with a downstream wavelength and an upstream wavelength depending on which terminal of the wavelength routing means 152 is connected through an optical fiber transmission line, and temporal overlap of signals among all ONUs Up to the number of OSUs is allowed. Therefore, the system bandwidth can be expanded without increasing the line rate per wavelength by increasing the OSU.
- Each ONU connected to the same terminal among the terminals of the wavelength routing means 152 via the optical fiber transmission line is logically connected to the same OSU and shares the upstream band and the downstream band.
- the logical connection between each ONU and the OSU is unchanged, and the traffic load cannot be distributed among different OSUs regardless of the traffic load state of each OSU.
- Non-Patent Document 1 proposes a wavelength tunable WDM / TDM-PON in which an optical transmitter and an optical receiver mounted on an ONU have a wavelength variable function (FIG. 3).
- the logical connection destination OSU can be changed in units of ONUs by switching transmission / reception wavelengths in the ONU.
- the logical connection between the ONU and OSU is changed so that the traffic load is distributed to the OSU in the low load state. Degradation of communication quality can be prevented.
- the wavelength tunable WDM / TDM-PON is a protection operation in which when an OSU fails, the ONU that is logically connected to the failed OSU changes communication destination OSU to another OSU and resumes communication. Is possible (FIG. 4, Non-Patent Document 2).
- the reception wavelength of the ONU logically connected to the OSU is set to the output optical wavelength of the failed OSU.
- the OLT Optical Line Terminal
- an ONU that has detected that no downstream signal light has been received for a certain time or more is re-registered in the OLT by deleting the connection information with the OLT on the ONU side and re-executing the discovery procedure.
- the ONU that has been logically connected to the failed OSU has the OSU that outputs the downstream signal light at a wavelength that can be received by itself, and therefore performs the discovery procedure again.
- the discovery procedure in order to start the registration process of an unregistered ONU, it is required that the received wavelength of the ONU matches the wavelength of the search signal that instructs to transmit a registration request to the unregistered ONU.
- an unregistered ONU receives a non-registered ONU by applying a wavelength sweeping method in which the unregistered ONU periodically sweeps the reception wavelength over the entire range of the downstream wavelength band.
- the wavelength can be matched with the wavelength of the search signal transmitted by at least one of the OSUs operating normally, and the registration process to the OLT can be started. Therefore, the ONU that has been logically connected to the failed OSU is logically connected to the new OSU through the discovery procedure to which the wavelength sweep method is applied, so that the protection operation is realized.
- the time required for the ONU logically connected to the failed OSU to resume communication after the OSU failure occurs is required.
- an unregistered ONU is used until the received wavelength of the ONU matches the wavelength of the search signal. Since the registration process is not started, there is a problem that it takes a long time to complete the protection operation.
- an object of the present invention is to provide a protection method and an optical communication system in which it takes a short time until the ONU that is logically connected to the failed OSU resumes communication in order to solve the above problems.
- the present invention assigns a spare OSU to each ONU, and continues to hold connection information held by the ONU and OLT even if an OSU failure is detected.
- OLT may be described as a parent node and ONU as a child node.
- a parent node having a plurality of termination devices and a plurality of child nodes are connected via an optical fiber transmission line, and at least one of the child nodes and the termination devices is provided.
- the failure of the termination device is detected, the child node that has been logically connected to the failed termination device continuously maintains connection information with the parent node and the termination device that has failed in the parent node;
- the optical communication system is: A parent node with multiple termination devices; A plurality of child nodes connected to the parent node via an optical fiber transmission line; A wavelength variable function that at least one of the child node and the termination device includes, and enables logical connection between the child node and any one of the plurality of termination devices;
- An optical communication system comprising: The parent node is Standby designation means for designating the termination device different from the termination device to which the child node is logically connected as a spare termination device of the child node; First information holding means for continuously holding information of the child node that is logically connected to the failed terminal device when a failure of the terminal device is detected; Based on the information of the child node held by the first information holding means, a control frame, which is a downstream signal light, is transmitted to the backup termination device designated by the child node logically connected to the failed termination device.
- Control frame transmitting means for transmitting to the child node;
- the logical termination destination of the child node is changed from the termination device to the spare termination device by the spare termination device receiving the upstream signal light transmitted from the child node in response to the control frame.
- With The child node is Second information holding means for continuously holding connection information with the parent node when a failure of the terminal device is detected;
- the present invention when an ONU logically connected to a failed OSU detects an OSU failure, connection information with the OLT is not deleted, and the spare OSU takes over the information of the ONU on the OLT side. No action is required. Therefore, the ONU that is logically connected to the failed OSU can resume communication in a short time after the OSU failure occurs. Therefore, the present invention can provide a protection method and an optical communication system in which the time required for the ONU that is logically connected to the failed OSU to resume communication is short.
- the protection method according to the present invention is characterized in that the information on the child node held by the parent node in the information holding procedure is delivered from the parent node to the spare terminal device in the control frame transmission procedure.
- the control frame transmitting means of the optical communication system according to the present invention is characterized in that the information of the child node held by the first information holding means is delivered to the backup termination apparatus.
- the slave node in the spare designation procedure, the slave node is notified of the wavelength of the downstream signal light transmitted from the spare termination device to the child node, When the child node detects a failure of the termination device that has been logically connected, a reception wavelength switching procedure is performed to cause the child node to switch the reception wavelength to the wavelength of the downstream signal light that is logically connected to the backup termination device. It is characterized by.
- the backup designation unit of the optical communication system notifies the slave node of the wavelength of the downstream signal light transmitted from the backup termination device to the child node;
- the wavelength variable function of the child node is characterized by switching the reception wavelength of the child node to the wavelength of the downstream signal light that is logically connected to the backup termination device when the termination device that has been logically connected fails. To do.
- the ONU that is logically connected to the failed OSU can switch the reception wavelength of the downstream signal light to the standby wavelength when the OSU failure is detected, the reception wavelength is spread over the entire downstream wavelength band.
- the control frame transmitted by the spare OSU can be received without sweeping.
- One is to notify the child node of the wavelength of the upstream signal light to be transmitted from the child node to the spare termination device in the backup designation procedure,
- a transmission wavelength switching procedure is performed to cause the child node to switch the transmission wavelength to the wavelength of the upstream signal light that is logically connected to the backup termination device.
- the backup designation unit of the optical communication system notifies the child node of the wavelength of the upstream signal light transmitted from the child node to the backup terminal device;
- the wavelength variable function of the child node switches the transmission wavelength of the child node to the wavelength of the upstream signal light that is logically connected to the backup termination device when the termination device that has been logically connected fails.
- the other is a transmission wavelength switching procedure for causing the child node to switch the transmission wavelength to the wavelength of the upstream signal light that is logically connected to the standby termination device in accordance with the wavelength switching instruction included in the control frame notified in the control frame transmission procedure. I do.
- the wavelength tunable function of the child node of the optical communication system is an uplink that logically connects the transmission wavelength of the child node with the standby termination device according to a wavelength switching instruction included in the control frame notified by the control frame transmission means. Switch to the wavelength of the signal light.
- the protection method and optical communication system according to the present invention are as follows.
- the optical communication system connects the parent node and the child node via wavelength routing means, and the reception wavelength of the downlink signal light received by the child node is determined in advance, In the information holding procedure, the received wavelength is held in the information of the child node, In the control frame transmission procedure, the backup termination device is caused to transmit the control frame at the reception wavelength set in the child node logically connected to the failed termination device.
- the optical communication system further comprises wavelength routing means for connecting the parent node and the child node,
- the child node has a predetermined reception wavelength of downlink signal light to be received,
- the parent node is
- the first information holding means holds the received wavelength in the information of the child node;
- the control frame transmission unit causes the backup termination device to transmit the control frame at the reception wavelength set in the child node logically connected to the failed termination device.
- the protection method and the optical communication system according to the present invention are as follows.
- the transmission wavelength of the upstream signal light transmitted by the child node is predetermined, In the information holding procedure, the transmission wavelength is held in the information of the child node, In the confirmation procedure, the wavelength received by the optical receiver of the standby termination apparatus is set to the transmission wavelength of the upstream signal light transmitted from the child node.
- the transmission wavelength of the upstream signal light to be transmitted is predetermined
- the transmission wavelength is held in the information of the child node
- the parent node is The confirmation means sets the wavelength received by the optical receiver of the standby termination device to the transmission wavelength of the upstream signal light transmitted from the child node.
- the present invention can provide a protection method and an optical communication system in which it takes a short time until the ONU that is logically connected to the failed OSU resumes communication.
- TDM-PON It is a figure explaining WDM / TDM-PON. It is a figure explaining wavelength variable type WDM / TDM-PON. It is a figure explaining operation
- This embodiment is a protection method in a wavelength tunable WDM / TDM-PON in which an optical receiver mounted on an ONU has a wavelength tunable function.
- the outline of the operation of the protection method of this embodiment is as follows.
- the ONU detects a failure of the OSU that is logically connected to itself, the ONU switches the reception wavelength to the standby wavelength when logically connecting to the standby OSU designated in advance for each ONU, but does not delete the connection information with the OLT. .
- the spare OSU of the ONU that is logically connected to the failed OSU takes over the information of the ONU.
- the ONU that is logically connected to the failed OSU resumes communication in a short time.
- the protection method of the present embodiment is configured such that a parent node having a plurality of termination devices and a plurality of child nodes are connected via an optical fiber transmission line, and at least one of the child nodes and the termination devices has a variable wavelength function.
- the child node that has been logically connected to the failed termination device continuously maintains connection information with the parent node and the termination device that has failed in the parent node;
- the slave node in the preliminary designation procedure, is notified of the wavelength of the downstream signal light transmitted from the standby termination device to the child node, When the child node detects a failure of the termination device that has been logically connected, a reception wavelength switching procedure is performed to cause the child node to switch the reception wavelength to the wavelength of the downstream signal light that is logically connected to the backup termination device. It is characterized by.
- the optical communication system to which the protection method of this embodiment is applied is as follows.
- An optical communication system comprising: The parent node is Standby designation means for designating the termination device different from the termination device to which the child node is logically connected as a spare termination device of the child node;
- First information holding means for continuously holding information of the child node that is logically connected to the failed terminal device when a failure of the terminal device is detected;
- Based on the information of the child node held by the first information holding means Based on the information of the child node held by the first information holding means, a control frame, which is a downstream signal light, is transmitted to the backup termination device designated by the child node logically connected to the failed termination device.
- Control frame transmitting means for transmitting to the child node;
- the logical termination destination of the child node is changed from the termination device to the spare termination device by the spare termination device receiving the upstream signal light transmitted from the child node in response to the control frame.
- With The child node is Second information holding means for continuously holding connection information with the parent node when a failure of the terminal device is detected;
- the wavelength variable function of the child node is characterized by switching the reception wavelength of the child node to the wavelength of the downstream signal light that is logically connected to the backup termination device when the termination device that has been logically connected fails. To do.
- the optical communication system has the wavelength variable WDM / TDM-PON configuration of FIG.
- the wavelength tunable WDM / TDM-PON configuration to which the protection method according to the present embodiment is applied is not limited to FIG. 3.
- wavelength routing means such as an AWG or thin film filter and an optical fiber between the ONU and the OLT.
- the present invention can also be applied to a configuration (FIG. 5) in which optical multiplexing / demultiplexing means such as an optical coupler created by PLC or the like is arranged.
- OSU side terminals # 1 to #M (M is an integer of 2 or more) and optical fiber transmission line side terminals # 1 to #N (N is an integer of 2 or more), and the input light is determined according to the wavelength 1
- N is an integer of 2 or more
- the wavelength routing means N ⁇ M AWG, etc., which has wavelength circulatory characteristics and whose input / output characteristics are shown in FIG. 7 and FIG.
- the wavelength tunable WDM / TDM-PON 300b of FIG. 3 includes OSUs 51 # 1 to #M , transmits downstream signal light having wavelengths ⁇ D_1 to ⁇ D_M , and upstream burst signal light having wavelengths ⁇ U_1 to ⁇ U_M.
- the input OLT 100a is connected to a plurality of ONUs 200a assigned from the OLT with each wavelength from ⁇ D_1 to ⁇ D_M and ⁇ U_1 to ⁇ U_M as a downstream wavelength and an upstream wavelength via an optical fiber transmission line. ing.
- Each OSU 51 in the OLT 100a transmits downlink signal light having a different wavelength for each OSU.
- Downstream signal light from each OSU 51 is wavelength-multiplexed by the optical multiplexing / demultiplexing means 151 and then output to the optical fiber transmission line.
- the optical multiplexing / demultiplexing means 151 an optical coupler or the like produced by an optical fiber or PLC (Planar Lightwave Circuit) or the like corresponds to this.
- the wavelength tunable optical receiver 23 in the ONU 200a selectively receives the downlink signal light, which is the downlink wavelength assigned from the OLT 100a, from the input wavelength multiplexed signal light.
- the light receiver 21 is, for example, a PIN-PD (Photo-Diode) or an APD (Avalanche Photo-Diode).
- the ONU 200 a arranges the wavelength tunable filter 22 in front of the light receiver 21.
- the ONU 200a can selectively receive the downstream signal light of a desired wavelength by the wavelength variable optical receiver 23 by changing the transmission wavelength of the wavelength tunable filter 22 according to the assigned downstream wavelength.
- Each ONU 200a determines whether the received frame is addressed to itself by using an ONU identifier such as LLID (Logical Link ID), and performs selection of the received frame.
- LLID Logical Link ID
- the ONU 200a includes a wavelength tunable optical transmitter 24 that can intermittently transmit signal light of wavelengths ⁇ U_1 to ⁇ U_M for uplink communication.
- the ONU 200a transmits the upstream burst signal light at the upstream wavelength assigned from the OLT 100a within the transmission permission time notified from the OLT.
- the transmission permission time notified as dynamic band allocation information from the OLT is between each ONU 200a stored in the OLT 100a so that burst signal lights from different ONUs 200a to which the same upstream wavelength is allocated do not collide with each other.
- Frame round-trip propagation time RTT: Round Trip Time).
- the wavelength tunable optical transmitter is, for example, a configuration in which the output light wavelength of a direct modulation laser such as a distributed feedback (DFB) laser is changed by temperature control, or a direct modulation laser having a different output light wavelength is arranged in an array. And it can be set as the structure in which the high-speed wavelength switching which switches the laser emitted by the control signal from the outside is possible.
- a wavelength tunable optical transmitter uses a Mach-Zehnder modulator, an electroabsorption (EA) modulator, or a semiconductor optical amplifier that uses a semiconductor or lithium diobate (LiNbO 3 ) as output light from a wavelength tunable light source.
- the wavelength tunable light source can be configured, for example, by arranging continuous light (CW) lasers having different output light wavelengths in an array and switching the output light wavelength by an external control signal.
- CW continuous light
- DBR distributed Bragg reflector
- an external resonator laser or the like can be used as the wavelength variable light source.
- the upstream burst signal light transmitted through the optical fiber transmission line is branched by the optical multiplexing / demultiplexing means 151, and then input to the OSUs 51 # 1 to #M that selectively receive upstream burst signal lights having different wavelengths.
- a wavelength filter 13 having a different transmission wavelength for each optical receiver is arranged in front of the light receiver 14 such as a PIN-PD or APD corresponding to a burst signal.
- the burst signal light can be selectively received.
- each ONU 51 sends an upstream burst signal light including an ONU identifier such as LLID assigned to itself in the transmission frame, so that the OLT 100a determines the ONU 200a that is the transmission source of the frame based on the ONU identifier in the reception frame. Can be identified.
- an ONU identifier such as LLID assigned to itself in the transmission frame
- coherent receivers (16, 27) can be used as shown in FIG.
- the output light wavelength of the local light source 28 in the ONU 200b is set near the wavelength of the assigned downstream signal light.
- the output light wavelength of the local light source 17 in the OLT 100b is set in the vicinity of one of the wavelengths ⁇ U_1 to ⁇ U_M so as to be different for each OSU 51 .
- the transmission distance can be extended and the number of ONUs to be accommodated can be increased.
- the number of OSUs can be expanded by increasing the branching loss allowed in the optical multiplexing / demultiplexing means 151 connected to each OSU, the total system bandwidth can be expanded.
- the application of coherent reception eliminates the need for a wavelength filter, the adjacent wavelength interval can be narrowed without being limited by the characteristics of the wavelength filter.
- FIGS. 10 and 11 show a case where ONU # n-1 logically connected to the failed OSU # 1 changes the logical connection destination OSU to OSU # 2 designated as the spare OSU.
- one spare OSU is designated for each ONU separately from the logically connected OSU.
- the spare OSU designated for each ONU may be an OSU in which one or more ONUs are logically connected, or an OSU in which no ONUs are logically connected.
- the downstream wavelength when logically connecting to the backup OSU is notified to each ONU as the backup wavelength.
- the upstream wavelength when logically connected to the backup OSU may be notified to each ONU as the backup wavelength (FIG. 11).
- the backup OSU may notify the ONU of the uplink wavelength (FIG. 10). 3, 5, 6, and 9, the OLT has a preliminary designation unit.
- a wavelength switching instruction for switching the transmission wavelength to the upstream wavelength when logically connected to the standby OSU will be described later. Included in the control frame. Then, after receiving the control frame, the ONU switches to the transmission wavelength to the spare OSU. As described above, the ONU has the wavelength variable function in the present embodiment.
- the ONU continues to store the ONU identifier such as the LLID assigned from the OLT without deleting the connection information with the OLT. That is, the ONUs in FIGS. 3, 5, 6, and 9 have the second information holding unit.
- the OLT can detect a failure of the OSU due to, for example, no reception of upstream burst signal light over a certain period of time.
- the OLT detects an OSU failure
- the OLT continues to hold information on the ONU that is logically connected to the failed OSU. That is, the OLT in FIGS. 3, 5, 6, and 9 has the first information holding unit. Then, the OLT delivers the retained ONU information to the spare OSU.
- the ONU spare OSU logically connected to the failed OSU takes over the information of the ONU.
- the ONU information includes ONU identifiers such as LLID assigned from the OLT, frame round-trip propagation time with the OLT, and the like.
- Control frame transmission procedure, control frame transmission means In the OLT, when an OSU failure is detected, a control frame instructing a reply is transmitted from the spare OSU designated for each ONU to the ONU logically connected to the failed OSU. That is, the OLT in FIGS. 3, 5, 6, and 9 has a control frame transmission unit.
- the spare OSU includes an ONU identifier such as an LLID already assigned to the ONU that is the destination of the frame in the control frame addressed to the ONU that is logically connected to the failed OSU.
- the transmission permission time of the upstream burst signal light returned by the ONU for the control frame is also included. The transmission permission time is determined in consideration of the frame round-trip propagation time between the OLT and the ONU so as to avoid the collision between the upstream burst signal light returned by each ONU.
- the ONU backup OSU logically connected to the failed OSU transmits a control frame addressed to the ONU
- the ONU switches the received wavelength to the notified backup wavelength. Therefore, the ONU reception wavelength matches the wavelength of the control frame transmitted by the backup OSU, and the ONU can receive the control frame without sweeping the reception wavelength over the entire range of the downstream wavelength band. .
- the ONU recognizes that the control frame is addressed to itself based on the ONU identifier such as LLID assigned from the OLT that is continuously stored, and transmits the upstream burst signal light within the transmission permission time notified by the control frame. Send back. That is, the ONUs in FIGS. 3, 5, 6, and 9 have response means.
- the ONU that is logically connected to the failed OSU switches the reception wavelength to the standby wavelength when an OSU failure is detected. For this reason, the ONU can receive the control frame transmitted by the backup OSU without sweeping the reception wavelength over the entire downstream wavelength band. Further, the ONU does not delete the connection information with the OLT even after the reception wavelength is switched to the standby wavelength, and the standby OSU takes over the information of the ONU on the OLT side, so the discovery operation is unnecessary. Therefore, the ONU that is logically connected to the failed OSU can resume communication in a short time after the OSU failure occurs.
- This embodiment is a protection method in a wavelength tunable WDM / TDM-PON in which an optical receiver mounted on an ONU does not have a wavelength tunable function.
- the outline of the operation of the protection method of this embodiment is as follows.
- the ONU does not delete the connection information with the OLT when detecting a failure of the OSU that is logically connected to the ONU.
- the spare OSU designated for each ONU logically connected to the failed OSU takes over the information of the ONU.
- the ONU that is logically connected to the failed OSU resumes communication in a short time.
- the protection method of the present embodiment performs the preliminary designation procedure, the information holding procedure, the control frame transmission procedure, the response procedure, and the confirmation procedure described in the first embodiment.
- the parent node (OLT) includes a spare designation unit, a first information holding unit, a control frame transmission unit, and a confirmation unit
- the node (ONU) includes a second information holding unit and a response unit.
- the optical communication system has the wavelength variable WDM / TDM-PON configuration of FIG.
- a wavelength routing unit 153 such as an AWG or a thin film filter and an optical multiplexing / demultiplexing unit 151 such as an optical coupler created by an optical fiber or PLC are disposed between the ONU 200b and the OLT 100b.
- the wavelength tunable WDM / TDM-PON configuration to which the protection method in this embodiment is applied is not limited to FIG.
- the protection method in this embodiment can also be applied to the configuration shown in FIG.
- FIG. 13 includes optical transmitter / receiver side terminals # 1 to #M (M is an integer of 2 or more) and optical fiber transmission line side terminals # 1 to #N (N is an integer of 2 or more).
- wavelength routing means having a wavelength distribution function that is output from one terminal determined accordingly is arranged between the ONU and the OLT.
- each OSU 51 includes a wavelength tunable optical transmitter 18 that can output wavelengths ⁇ D — 1 to ⁇ D — N for downlink communication.
- the tunable optical transmitter 18 outputs the output light in units of frames depending on which optical fiber transmission line side terminal of the wavelength routing means 153 is connected to the ONU that is the destination of the input downstream frame via the optical fiber transmission line. Change the wavelength.
- Downstream signal light from each wavelength variable optical transmitter 18 is multiplexed by the optical multiplexing / demultiplexing means 151 and then input to the wavelength routing means 153.
- the wavelength routing unit 153 outputs the input downstream signal light from the different optical fiber transmission line side terminal to the optical fiber transmission line depending on the wavelength.
- the ONU 200b is connected to one of the optical fiber transmission path side terminals of the wavelength routing means 153 via the optical fiber transmission path, and receives the downstream signal light output from the connected terminal using the optical receiver 29.
- Examples of the optical receiver 29 include PIN-PD and APD.
- Each ONU 200b determines whether the received frame is addressed to itself by using an ONU identifier such as LLID, and selects a received frame.
- the ONU 200b includes an optical transmitter 30 that can output at least one of the wavelengths ⁇ U — 1 to ⁇ U_N .
- the ONU 200b transmits the upstream burst signal light at the upstream wavelength assigned by the OLT 100b within the transmission permission time notified from the OLT.
- the transmission permission time notified as dynamic band allocation information from the OLT is determined in consideration of the frame round-trip propagation time between the OLT and each ONU so that upstream burst signal lights destined for the same OSU do not collide with each other. Is done. In the configuration of FIG.
- the upstream wavelength assigned from the OLT is determined by which of the terminals on the optical fiber transmission line side of the wavelength routing means 153 the ONU is connected via the optical fiber transmission line.
- the optical transmitter 30 with a wavelength variable function, it is possible to unify the types of ONUs that are connected to different optical fiber transmission line side terminals, and to improve economy and maintenance operability.
- the wavelength variable optical transmitter 24 mounted in the ONU in the wavelength variable WDM / TDM-PON of FIG. 3 can be used as the optical transmitter 30 having the wavelength variable function.
- the upstream signal light transmitted through the optical fiber transmission line is wavelength-multiplexed through the wavelength routing unit 153, branched by the optical multiplexing / demultiplexing unit 151, and input to the OSUs 51 # 1 to #M.
- the wavelength tunable optical receiver 19 in each OSU selectively receives an upstream burst signal light having a desired upstream wavelength from wavelength multiplexed signal light input as follows. First, the wavelength tunable optical receiver 19 recognizes the ONU that is the transmission source of the input upstream burst signal light by referring to the dynamic band allocation information notified to each ONU.
- the wavelength tunable optical receiver 19 sets the reception wavelength according to which of the terminals on the optical fiber transmission line side of the wavelength routing unit 153 is connected to the ONU via the optical fiber transmission line.
- the wavelength tunable optical receiver 19 may have a configuration in which a wavelength tunable filter capable of changing the transmission wavelength is disposed in front of a light receiver such as PIN-PD or APD.
- each ONU 200b transmits an upstream burst signal light including an ONU identifier such as LLID assigned to itself in the transmission frame, so that the OLT 100b determines the ONU that is the transmission source of the frame based on the ONU identifier in the reception frame. Can be identified.
- the output light wavelength of the local light source in the ONU is a predetermined value depending on which of the optical fiber transmission line side terminals of the wavelength routing means is connected to the terminal via the optical fiber transmission line. It is set near the downstream wavelength.
- the output light wavelength of the local light source in the OSU is changed according to which ONU the upstream burst signal light input to the optical receiver is transmitted.
- the transmission distance can be extended and the number of ONUs to be accommodated can be increased. Further, since the number of OSUs can be expanded by increasing the branching loss allowed by the optical multiplexing / demultiplexing means connected to each OSU, the total system bandwidth can be expanded.
- FIG. 14 shows a case where ONU # n-1 logically connected to the failed OSU # 1 changes the logical connection destination OSU to OSU # 2 designated as the spare OSU.
- the ONU detects that no downstream signal light has been received for a certain period of time, that is, when an OSU failure is detected, the ONU does not delete the connection information with the OLT and uses an ONU identifier such as an LLID assigned by the OLT. Keep memorizing. That is, in FIG. 12, 13, ONU has a 2nd information holding means.
- the OLT can detect a failure of the OSU due to, for example, no reception of upstream burst signal light over a certain period of time.
- the OLT continues to hold information on the ONU that is logically connected to the failed OSU. That is, the OLT in FIGS.
- the ONU 12 and 13 has a first information holding unit. Then, the OLT delivers the retained ONU information to the spare OSU. That is, the ONU spare OSU logically connected to the failed OSU takes over the information of the ONU.
- the ONU information includes ONU identifiers such as LLID assigned from the OLT, frame round-trip propagation time with the OLT, and the like.
- Control frame transmission procedure, control frame transmission means When the OLT detects an OSU failure, the control frame for instructing a reply from the spare OSU designated for each ONU to the ONU logically connected to the failed OSU, similarly to the protection operation in the first embodiment. Send. That is, the OLT in FIGS. 12 and 13 has control frame transmission means.
- the information included in the control frame by the OLT in FIG. 12 is the same as that in FIG. 11 of the first embodiment.
- the information included in the control frame by the OLT in FIG. 13 is the same as that in FIG. 10 or 11 in the first embodiment.
- the ONU continuously stores an ONU identifier such as an LLID assigned from the OLT when a spare OSU of the ONU that is logically connected to the failed OSU transmits a control frame addressed to the ONU. For this reason, as shown in FIG. 14, the ONU recognizes that the control frame is addressed to itself, and returns the uplink burst signal light within the transmission permission time notified by the control frame. That is, the ONUs in FIGS. 12 and 13 have response means.
- an ONU identifier such as an LLID assigned from the OLT when a spare OSU of the ONU that is logically connected to the failed OSU transmits a control frame addressed to the ONU. For this reason, as shown in FIG. 14, the ONU recognizes that the control frame is addressed to itself, and returns the uplink burst signal light within the transmission permission time notified by the control frame. That is, the ONUs in FIGS. 12 and 13 have response means.
- the present invention provides (1): A parent node having a plurality of termination devices is connected to a plurality of child nodes via an optical fiber transmission line, and the child node is connected to the plurality of termination devices by a wavelength variable function provided in at least one of the child nodes and the termination devices.
- the child node can be logically connected to any one of the devices, and the child device is designated as a backup terminal device other than the terminal device to which the child node is logically connected.
- a method When the child node detects a failure of the terminal device that has been logically connected, the child node continues to hold connection information with the parent node, When the parent node detects a failure of the termination device, the parent node continues to hold the information of the child node logically connected to the failed termination device, Of the child nodes that are logically connected to the failed termination device, the backup termination device transmits a control frame to the child node as a backup termination device, In the protection method, the parent node confirms that the terminating device of the logical connection destination of the child node is changed by receiving the upstream signal light returned from the child node in response to the control frame. .
- the spare termination device is information on the child node that is the spare termination device itself among the child nodes logically connected to the failed termination device.
- the child node can selectively switch the wavelength to be received, The wavelength of the downstream signal light transmitted to the child node by the backup termination device when logically connected to the backup termination device is notified, When detecting a failure of the terminating device that has been logically connected, the wavelength that is selectively received is switched to the wavelength of the downstream signal light that is logically connected to the backup terminating device (1) ) Or the protection method according to (2).
- the child node can switch the transmission wavelength of the upstream signal light, The wavelength of the upstream signal light that the child node transmits to the standby termination device when logically connected to the backup termination device is notified, (1) The transmission wavelength of the upstream signal light is switched to the wavelength of the upstream signal light when logically connected to the backup termination device when a failure of the termination device that has been logically connected is detected. ) To (3).
- the child node can switch the transmission wavelength of the upstream signal light, In accordance with the wavelength switching instruction notified in the control frame from the backup termination device, the uplink signal transmitted from the child node to the backup termination device when the transmission wavelength of the uplink signal light is logically connected to the backup termination device.
- the protection method according to any one of (1) to (3), wherein the protection method is switched to a wavelength of light.
- the present invention enables an ONU that is logically connected to a failed OSU to receive a control frame transmitted by the backup OSU by switching the reception wavelength to the backup wavelength when the OSU failure is detected.
- the feature is that communication can be resumed in a short time by taking over the information of the ONU logically connected to the failed OSU.
- Optical transmitter 12 Wavelength multiplexing / demultiplexing means 13: Wavelength filter 14: Light receiver 15: Optical receiver 16: Coherent receiver 17: Local light source 18: Wavelength variable optical transmitter 19: Wavelength variable optical receiver 21 : Light receiver 22: wavelength tunable filter 23: wavelength tunable optical receiver 24: wavelength tunable optical transmitter 26: wavelength multiplexing / demultiplexing means 27: coherent receiver 28: local light source 29: optical receiver 30: optical transmitter 51 : OSU 100, 100a, 100b, 100c: OLT 151: Optical multiplexing / demultiplexing means 152: Wavelength routing means 153: Wavelength routing means 200, 200a, 200b: ONU 250: Optical fiber transmission line 300: TDM-PON 300a: WDM / TDM-PON 300b, 301b, 302b: Variable wavelength WDM / TDM-PON 300c: Wavelength variable WDM / TDM-PON 300d: Variable wavelength WDM / TDM-PON 300
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Abstract
Description
前記子ノードが論理接続している前記終端装置とは別の前記終端装置を前記子ノードの予備終端装置として指定しておく予備指定手順と、
前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードに前記親ノードとの接続情報を継続して保持させるとともに前記親ノードに故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持させる情報保持手順と、
前記情報保持手順で前記親ノードに保持させた前記子ノードの情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに指定されている前記予備終端装置に下り信号光である制御フレームを前記子ノードへ送信させる制御フレーム送信手順と、
前記情報保持手順で前記子ノードに保持させた前記親ノードとの接続情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに前記制御フレーム送信手順で送信された前記制御フレームに応答する上り信号光を前記親ノードへ送信させる応答手順と、
前記応答手順で前記子ノードから送信された上り信号光を前記予備終端装置が受信することで、前記子ノードの論理接続先が前記終端装置から前記予備終端装置へ変更されたことを確認する確認手順と、
を行うことを特徴とする。
複数の終端装置を備える親ノードと、
前記親ノードと光ファイバ伝送路を介して接続される複数の子ノードと、
前記子ノードと前記終端装置の少なくとも一方が備え、前記子ノードと複数の前記終端装置のうちの任意の1台との論理接続を可能とする波長可変機能と、
を有する光通信システムであって、
前記親ノードは、
前記子ノードが論理接続している前記終端装置とは別の前記終端装置を前記子ノードの予備終端装置として指定しておく予備指定手段と、
前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持する第1情報保持手段と、
前記第1情報保持手段が保持する前記子ノードの情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに指定されている前記予備終端装置に下り信号光である制御フレームを前記子ノードへ送信させる制御フレーム送信手段と、
前記制御フレームに応答して前記子ノードから送信された上り信号光を前記予備終端装置が受信することで、前記子ノードの論理接続先が前記終端装置から前記予備終端装置へ変更されたことを確認する確認手段と、
を備え、
前記子ノードは、
前記終端装置の故障を検知した際に、前記親ノードとの接続情報を継続して保持する第2情報保持手段と、
前記第2情報保持手段が保持する前記親ノードとの接続情報に基づいて、前記親ノードの前記制御フレーム送信手段が送信した前記制御フレームに応答する上り信号光を前記親ノードへ送信する応答手段と、
を備えることを特徴とする。
論理接続していた前記終端装置の故障を前記子ノードが検知した際に、前記子ノードに受信波長を前記予備終端装置と論理接続する下り信号光の波長に切り替えさせる受信波長切替手順を行うことを特徴とする。
前記子ノードの前記波長可変機能は、論理接続していた前記終端装置の故障の際に、前記子ノードの受信波長を前記予備終端装置と論理接続する下り信号光の波長に切り替えることを特徴とする。
論理接続していた前記終端装置の故障を前記子ノードが検知した際に、前記子ノードに送信波長を前記予備終端装置と論理接続する前記上り信号光の波長に切り替えさせる送信波長切替手順を行う。
前記子ノードの前記波長可変機能は、論理接続していた前記終端装置の故障の際に、前記子ノードの送信波長を前記予備終端装置と論理接続する前記上り信号光の波長に切り替える。
前記情報保持手順で、前記受信波長を前記子ノードの情報に保持し、
前記制御フレーム送信手順で、前記予備終端装置に、故障した前記終端装置と論理接続していた前記子ノードに設定されている前記受信波長で前記制御フレームを送信させることを特徴とする。
前記子ノードは、受信する下り信号光の受信波長が予め定まっており、
前記親ノードは、
前記第1情報保持手段が、前記受信波長を前記子ノードの情報に保持し、
前記制御フレーム送信手段が、前記予備終端装置に、故障した前記終端装置と論理接続していた前記子ノードに設定されている前記受信波長で前記制御フレームを送信させることを特徴とする。
前記情報保持手順で、前記送信波長を前記子ノードの情報に保持し、
前記確認手順で、前記予備終端装置の光受信器が受信する波長を、前記子ノードから送信される上り信号光の前記送信波長に設定することを特徴とする。
前記情報保持手順で、前記送信波長を前記子ノードの情報に保持し、
前記親ノードは、
前記確認手段が、前記予備終端装置の光受信器が受信する波長を、前記子ノードから送信される上り信号光の前記送信波長に設定することを特徴とする。
本実施形態は、ONUに搭載する光受信器に波長可変機能を備える波長可変型WDM/TDM-PONにおけるプロテクション方法である。本実施形態のプロテクション方法の動作概要は次の通りである。ONUは、自らと論理接続するOSUの故障を検知した際に、ONUごとに予め指定されている予備OSUと論理接続する際の予備波長へ受信波長を切り替える一方、OLTとの接続情報を削除しない。OLTは、OSU故障を検知した際に、故障したOSUと論理接続していたONUの予備OSUが当該ONUの情報を引き継ぐ。このことにより、本実施形態のプロテクション方法は故障したOSUと論理接続していたONUが短時間で通信を再開する。
前記子ノードが論理接続している前記終端装置とは別の前記終端装置を前記子ノードの予備終端装置として指定しておく予備指定手順と、
前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードに前記親ノードとの接続情報を継続して保持させるとともに前記親ノードに故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持させる情報保持手順と、
前記情報保持手順で前記親ノードに保持させた前記子ノードの情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに指定されている前記予備終端装置に下り信号光である制御フレームを前記子ノードへ送信させる制御フレーム送信手順と、
前記情報保持手順で前記子ノードに保持させた前記親ノードとの接続情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに前記制御フレーム送信手順で送信された前記制御フレームに応答する上り信号光を前記親ノードへ送信させる応答手順と、
前記応答手順で前記子ノードから送信された上り信号光を前記予備終端装置が受信することで、前記子ノードの論理接続先が前記終端装置から前記予備終端装置へ変更されたことを確認する確認手順と、
を行うことを特徴とする。
論理接続していた前記終端装置の故障を前記子ノードが検知した際に、前記子ノードに受信波長を前記予備終端装置と論理接続する下り信号光の波長に切り替えさせる受信波長切替手順を行うことを特徴とする。
複数の終端装置を備える親ノードと、
前記親ノードと光ファイバ伝送路を介して接続される複数の子ノードと、
前記子ノードと前記終端装置の少なくとも一方が備え、前記子ノードと複数の前記終端装置のうちの任意の1台との論理接続を可能とする波長可変機能と、
を有する光通信システムであって、
前記親ノードは、
前記子ノードが論理接続している前記終端装置とは別の前記終端装置を前記子ノードの予備終端装置として指定しておく予備指定手段と、
前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持する第1情報保持手段と、
前記第1情報保持手段が保持する前記子ノードの情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに指定されている前記予備終端装置に下り信号光である制御フレームを前記子ノードへ送信させる制御フレーム送信手段と、
前記制御フレームに応答して前記子ノードから送信された上り信号光を前記予備終端装置が受信することで、前記子ノードの論理接続先が前記終端装置から前記予備終端装置へ変更されたことを確認する確認手段と、
を備え、
前記子ノードは、
前記終端装置の故障を検知した際に、前記親ノードとの接続情報を継続して保持する第2情報保持手段と、
前記第2情報保持手段が保持する前記親ノードとの接続情報に基づいて、前記親ノードの前記制御フレーム送信手段が送信した前記制御フレームに応答する上り信号光を前記親ノードへ送信する応答手段と、
を備えることを特徴とする。
前記子ノードの前記波長可変機能は、論理接続していた前記終端装置の故障の際に、前記子ノードの受信波長を前記予備終端装置と論理接続する下り信号光の波長に切り替えることを特徴とする。
本実施形態を適用する波長可変型WDM/TDM-PON構成では、ONUごとに、論理接続しているOSUとは別に1台の予備OSUが指定される。ONUごとに指定する予備OSUは、1台以上のONUが論理接続しているOSUでも、ONUが1台も論理接続していないOSUでもよい。この時、予備OSUと論理接続する際の下り波長が予備波長として各ONUへ通知されている。同時に、予備OSUと論理接続する際の上り波長も予備波長として各ONUへ通知されていてもよい(図11)。また、ONUが下り受信波長を切り替えた後、予備OSUから当該上り波長をONUへ通知してもよい(図10)。なお、図3、5、6、9において、OLTが予備指定手段を有している。
ONUは、一定時間以上に渡る下り信号光の未受信を検知した場合、OSUの故障と判断し、自律的に受信波長または送受信波長を通知された予備波長に切り替える。予備波長として下り波長のみが通知されている場合には、ONUは図10に示すように受信波長のみを切り替える。予備波長として上り下り波長が通知されている場合には、ONUは図11に示すように受信波長及び送信波長を切り替える。
この時、ONUは、OLTとの接続情報を削除せずに、OLTから割り当てられているLLID等のONU識別子を継続して記憶する。すなわち、図3、5、6、9のONUは、第2情報保持手段を有する。
OLTは、例えば、一定時間以上に渡る上りバースト信号光の未受信によりOSUの故障を検知することができる。OLTは、OSU故障を検知した場合、故障したOSUと論理接続していたONUの情報を保持し続けている。すなわち、図3、5、6、9のOLTは、第1情報保持手段を有する。そして、OLTは、保持している前記ONU情報を予備OSUへ引き渡す。つまり、故障したOSUと論理接続していたONUの予備OSUは、当該ONUの情報を引き継ぐことになる。ONU情報としては、OLTから割り当てられているLLID等のONU識別子や、OLTとの間でのフレーム往復伝搬時間などがこれにあたる。
OLTでは、OSU故障を検知した場合、故障したOSUと論理接続していたONU宛に、ONUごとに指定されている予備OSUから、返信を指示する制御フレームを送信する。すなわち、図3、5、6、9のOLTは、制御フレーム送信手段を有する。予備OSUは、引き継いだONU情報を参照することにより、故障したOSUと論理接続していたONU宛の制御フレーム内に、フレームの宛先であるONUへ既に割り当てられているLLID等のONU識別子を含める。また、制御フレームに対してONUが返信する上りバースト信号光の送信許可時間も含められる。送信許可時間は、各ONUが返信する上りバースト信号光同士が衝突することを回避するよう、OLTとONUとの間でのフレーム往復伝搬時間を考慮して決定される。
ONUは、継続して記憶するOLTから割り当てられているLLID等のONU識別子に基づいて制御フレームが自分宛であると認識し、制御フレームにて通知された送信許可時間内に上りバースト信号光を返信する。すなわち、図3、5、6、9のONUは、応答手段を有する。
OLTは、返信された上りバースト信号光の受信をもって、当該ONUの論理接続先OSUが変更されプロテクション動作が完了したことを確認する。すなわち、図3、5、6、9のONUは、確認手段を有する。
本実施形態におけるプロテクション方法では、故障したOSUと論理接続していたONUは、OSU故障を検知した時点で受信波長を予備波長に切り替える。このため、当該ONUは、受信波長を下り波長帯域の全域に渡って掃引することなく、予備OSUが送信する制御フレームを受信できる。また、ONUは受信波長を予備波長に切り替えた後もOLTとの接続情報を削除せず、OLT側では予備OSUが当該ONUの情報を引き継ぐために、ディスカバリ動作が不要である。よって、故障したOSUと論理接続していたONUは、OSU故障が発生してから短時間で通信を再開できる。
本実施形態は、ONUに搭載する光受信器に波長可変機能を備えない波長可変型WDM/TDM-PONにおけるプロテクション方法である。本実施形態のプロテクション方法の動作概要は次の通りである。ONUは、自らと論理接続するOSUの故障を検知した際に、OLTとの接続情報を削除しない。OLTは、OSU故障を検知した際に、故障したOSUと論理接続していたONUごとに指定されている予備OSUが当該ONUの情報を引き継ぐ。このことにより、本実施形態のプロテクション方法は、故障したOSUと論理接続していたONUが短時間で通信を再開する。
本実施形態を適用する波長可変型WDM/TDM-PON構成では、ONUごとに、論理接続しているOSUとは別に1台の予備OSUが指定されている。ONUごとに指定する予備OSUは、1台以上のONUが論理接続しているOSUでも、ONUが1台も論理接続していないOSUでもよい。なお、図12、13において、OLTが予備指定手段を有している。
ONUは、一定時間以上に渡る下り信号光の未受信を検知した場合、すなわちOSU故障を検知した場合、OLTとの接続情報を削除せずに、OLTから割り当てられているLLID等のONU識別子を継続して記憶する。すなわち、図12、13において、ONUは、第2情報保持手段を有する。
OLTは、例えば、一定時間以上に渡る上りバースト信号光の未受信によりOSUの故障を検知することができる。OLTは、OSU故障を検知した場合、故障したOSUと論理接続していたONUの情報を保持し続けている。すなわち、図12、13のOLTは、第1情報保持手段を有する。そして、OLTは、保持している前記ONU情報を予備OSUへ引き渡す。つまり、故障したOSUと論理接続していたONUの予備OSUは、当該ONUの情報を引き継ぐことになる。ONU情報としては、OLTから割り当てられているLLID等のONU識別子や、OLTとの間でのフレーム往復伝搬時間などがこれにあたる。
OLTは、OSU故障を検知した場合、実施形態1におけるプロテクション動作と同様に、故障したOSUと論理接続していたONU宛に、ONUごとに指定されている予備OSUから、返信を指示する制御フレームを送信する。すなわち、図12、13のOLTは、制御フレーム送信手段を有する。図12のOLTが制御フレーム内に含める情報は、実施形態1の図11と同様である。図13のOLTが制御フレーム内に含める情報は、実施形態1の図10または図11と同様である。
ONUは、故障したOSUと論理接続していたONUの予備OSUが当該ONU宛の制御フレームを送信する時点で、OLTから割り当てられているLLID等のONU識別子を継続して記憶している。このために、図14のように、ONUは、制御フレームを自分宛であると認識し、制御フレームにて通知された送信許可時間内に上りバースト信号光を返信する。すなわち、図12、13のONUは応答手段を有する。
OLTは、返信された上りバースト信号光の受信をもって、当該ONUの論理接続先OSUが変更されプロテクション動作が完了したことを確認する。すなわち、図12、13のOLTは確認手段を有する。
本実施形態におけるプロテクション方法では、故障したOSUと論理接続していたONUは、OSU故障を検知した際に、OLTとの接続情報を削除せず、OLT側では予備OSUが当該ONUの情報を引き継ぐために、ディスカバリ動作が不要である。よって、故障したOSUと論理接続していたONUは、OSU故障が発生してから短時間で通信を再開できる。
以下は、本実施形態のプロテクション方法を説明したものである。
従来の波長掃引方式を適用したプロテクション技術では、ONUの受信波長が探索信号の波長と一致するまで未登録ONUの登録処理が開始されないため、プロテクション動作が完了するまでに要する時間が長くなるという課題があった。
(1):
複数の終端装置を備える親ノードが複数の子ノードと光ファイバ伝送路を介して接続され、前記子ノードと前記終端装置の少なくとも一方が備える波長可変機能により、前記子ノードが前記複数の終端装置のうちの任意の1台と論理接続することが可能であり、前記子ノードは論理接続している前記終端装置とは別の前記終端装置を予備終端装置として指定されている光通信システムにおけるプロテクション方法であって、
前記子ノードは、論理接続していた前記終端装置の故障を検知した際に、前記親ノードとの接続情報を継続して保持し、
前記親ノードは、前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持し、
前記予備終端装置が、故障した前記終端装置と論理接続していた前記子ノードのうち、自らを予備終端装置とする前記子ノード宛に制御フレームを送信し、
前記子ノードが前記制御フレームに対して返信する上り信号光の受信により、前記親ノードが前記子ノードの論理接続先の終端装置が変更されたことを確認することを特徴とするプロテクション方法である。
前記親ノードが前記終端装置の故障を検知した際に、前記予備終端装置が、故障した前記終端装置と論理接続していた前記子ノードのうち、自らを予備終端装置とする前記子ノードの情報を引き継ぐことを特徴とする上記(1)に記載のプロテクション方法である。
前記子ノードは、選択的に受信する波長を切替可能であり、
前記予備終端装置と論理接続する際に前記予備終端装置が前記子ノード宛に送信する下り信号光の波長を通知されており、
論理接続していた前記終端装置の故障を検知した際に、選択的に受信する波長を、前記予備終端装置と論理接続する際の前記下り信号光の波長に切り替えることを特徴とする上記(1)または(2)に記載のプロテクション方法である。
前記子ノードは、上り信号光の送信波長を切替可能であり、
前記予備終端装置と論理接続する際に前記子ノードが前記予備終端装置宛に送信する上り信号光の波長を通知されており、
論理接続していた前記終端装置の故障を検知した際に、上り信号光の送信波長を、前記予備終端装置と論理接続する際の前記上り信号光の波長に切り替えることを特徴とする上記(1)から(3)のいずれかに記載のプロテクション方法である。
前記子ノードは、上り信号光の送信波長を切替可能であり、
前記予備終端装置からの制御フレームにて通知される波長切替指示に従って、上り信号光の送信波長を、前記予備終端装置と論理接続する際の前記子ノードが前記予備終端装置宛に送信する上り信号光の波長に切り替えることを特徴とする上記(1)から(3)のいずれかに記載のプロテクション方法である。
12:波長合分波手段
13:波長フィルタ
14:受光器
15:光受信器
16:コヒーレント受信器
17:局発光源
18:波長可変光送信器
19:波長可変光受信器
21:受光器
22:波長可変フィルタ
23:波長可変光受信器
24:波長可変光送信器
26:波長合分波手段
27:コヒーレント受信器
28:局発光源
29:光受信器
30:光送信器
51:OSU
100、100a、100b、100c:OLT
151:光合分波手段
152:波長ルーティング手段
153:波長ルーティング手段
200、200a、200b:ONU
250:光ファイバ伝送路
300:TDM-PON
300a:WDM/TDM-PON
300b、301b、302b:波長可変型WDM/TDM-PON
300c:波長可変型WDM/TDM-PON
300d:波長可変型WDM/TDM-PON
300e:波長可変型WDM/TDM-PON
Claims (14)
- 複数の終端装置を備える親ノードと複数の子ノードとが光ファイバ伝送路を介して接続され、前記子ノードと前記終端装置の少なくとも一方が備える波長可変機能で、前記子ノードと複数の前記終端装置のうちの任意の1台とを論理接続する光通信システムのプロテクション方法であって、
前記子ノードが論理接続している前記終端装置とは別の前記終端装置を前記子ノードの予備終端装置として指定しておく予備指定手順と、
前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードに前記親ノードとの接続情報を継続して保持させるとともに前記親ノードに故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持させる情報保持手順と、
前記情報保持手順で前記親ノードに保持させた前記子ノードの情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに指定されている前記予備終端装置に下り信号光である制御フレームを前記子ノードへ送信させる制御フレーム送信手順と、
前記情報保持手順で前記子ノードに保持させた前記親ノードとの接続情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに前記制御フレーム送信手順で送信された前記制御フレームに応答する上り信号光を前記親ノードへ送信させる応答手順と、
前記応答手順で前記子ノードから送信された上り信号光を前記予備終端装置が受信することで、前記子ノードの論理接続先が前記終端装置から前記予備終端装置へ変更されたことを確認する確認手順と、
を行うことを特徴とするプロテクション方法。 - 前記情報保持手順で前記親ノードが保持した前記子ノードの情報を、前記制御フレーム送信手順で前記親ノードから前記予備終端装置へ引き渡すことを特徴とする請求項1に記載のプロテクション方法。
- 前記予備指定手順で、前記予備終端装置から前記子ノードへ送信する下り信号光の波長を前記子ノードに通知しておき、
論理接続していた前記終端装置の故障を前記子ノードが検知した際に、前記子ノードに受信波長を前記予備終端装置と論理接続する下り信号光の波長に切り替えさせる受信波長切替手順を行うことを特徴とする請求項1または2に記載のプロテクション方法。 - 前記予備指定手順で、前記子ノードから前記予備終端装置へ送信する上り信号光の波長を前記子ノードに通知しておき、
論理接続していた前記終端装置の故障を前記子ノードが検知した際に、前記子ノードに送信波長を前記予備終端装置と論理接続する前記上り信号光の波長に切り替えさせる送信波長切替手順を行うことを特徴とする請求項1から3のいずれかに記載のプロテクション方法。 - 前記制御フレーム送信手順で通知される前記制御フレームに含まれる波長切替指示に従って、前記子ノードに送信波長を前記予備終端装置と論理接続する上り信号光の波長に切り替えさせる送信波長切替手順を行うことを特徴とする請求項1から3のいずれかに記載のプロテクション方法。
- 前記光通信システムが前記親ノードと前記子ノードとを波長ルーティング手段を介して接続し、前記子ノードが受信する下り信号光の受信波長が予め定まっており、
前記情報保持手順で、前記受信波長を前記子ノードの情報に保持し、
前記制御フレーム送信手順で、前記予備終端装置に、故障した前記終端装置と論理接続していた前記子ノードに設定されている前記受信波長で前記制御フレームを送信させることを特徴とする請求項1又は2に記載のプロテクション方法。 - 前記子ノードが送信する上り信号光の送信波長が予め定まっており、
前記情報保持手順で、前記送信波長を前記子ノードの情報に保持し、
前記確認手順で、前記予備終端装置の光受信器が受信する波長を、前記子ノードから送信される上り信号光の前記送信波長に設定することを特徴とする請求項6に記載のプロテクション方法。 - 複数の終端装置を備える親ノードと、
前記親ノードと光ファイバ伝送路を介して接続される複数の子ノードと、
前記子ノードと前記終端装置の少なくとも一方が備え、前記子ノードと複数の前記終端装置のうちの任意の1台との論理接続を可能とする波長可変機能と、
を有する光通信システムであって、
前記親ノードは、
前記子ノードが論理接続している前記終端装置とは別の前記終端装置を前記子ノードの予備終端装置として指定しておく予備指定手段と、
前記終端装置の故障を検知した際に、故障した前記終端装置と論理接続していた前記子ノードの情報を継続して保持する第1情報保持手段と、
前記第1情報保持手段が保持する前記子ノードの情報に基づいて、故障した前記終端装置と論理接続していた前記子ノードに指定されている前記予備終端装置に下り信号光である制御フレームを前記子ノードへ送信させる制御フレーム送信手段と、
前記制御フレームに応答して前記子ノードから送信された上り信号光を前記予備終端装置が受信することで、前記子ノードの論理接続先が前記終端装置から前記予備終端装置へ変更されたことを確認する確認手段と、
を備え、
前記子ノードは、
前記終端装置の故障を検知した際に、前記親ノードとの接続情報を継続して保持する第2情報保持手段と、
前記第2情報保持手段が保持する前記親ノードとの接続情報に基づいて、前記親ノードの前記制御フレーム送信手段が送信した前記制御フレームに応答する上り信号光を前記親ノードへ送信する応答手段と、
を備えることを特徴とする光通信システム。 - 前記制御フレーム送信手段は、前記第1情報保持手段が保持する前記子ノードの情報を前記予備終端装置へ引き渡すことを特徴とする請求項8に記載の光通信システム。
- 前記予備指定手段は、前記予備終端装置から前記子ノードへ送信する下り信号光の波長を前記子ノードに通知し、
前記子ノードの前記波長可変機能は、論理接続していた前記終端装置の故障の際に、前記子ノードの受信波長を前記予備終端装置と論理接続する下り信号光の波長に切り替えることを特徴とする請求項8又は9に記載の光通信システム。 - 前記予備指定手段は、前記子ノードから前記予備終端装置へ送信する上り信号光の波長を前記子ノードに通知し、
前記子ノードの前記波長可変機能は、論理接続していた前記終端装置の故障の際に、前記子ノードの送信波長を前記予備終端装置と論理接続する前記上り信号光の波長に切り替えることを特徴とする請求項8から10のいずれかに記載の光通信システム。 - 前記子ノードの前記波長可変機能は、前記制御フレーム送信手段が通知する前記制御フレームに含まれる波長切替指示に従って、前記子ノードの送信波長を前記予備終端装置と論理接続する上り信号光の波長に切り替えることを特徴とする請求項8から10のいずれかに記載の光通信システム。
- 前記親ノードと前記子ノードとを接続する波長ルーティング手段をさらに有し、
前記子ノードは、受信する下り信号光の受信波長が予め定まっており、
前記親ノードは、
前記第1情報保持手段が、前記受信波長を前記子ノードの情報に保持し、
前記制御フレーム送信手段が、前記予備終端装置に、故障した前記終端装置と論理接続していた前記子ノードに設定されている前記受信波長で前記制御フレームを送信させることを特徴とする請求項8又は9に記載の光通信システム。 - 前記子ノードは、送信する上り信号光の送信波長が予め定まっており、
前記情報保持手順で、前記送信波長を前記子ノードの情報に保持し、
前記親ノードは、
前記確認手段が、前記予備終端装置の光受信器が受信する波長を、前記子ノードから送信される上り信号光の前記送信波長に設定することを特徴とする請求項13に記載の光通信システム。
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JP6078163B2 (ja) | 2017-02-08 |
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