KR100707244B1 - Apparatus and method for protection of wavelength division multiplexed passive optical network - Google Patents

Abstract

The present invention relates to a protection recovery apparatus for a wavelength division multiplexing passive optical subscriber network, and a method and a method for recovering protection of the wavelength division multiplexing passive optical subscriber network according to the present invention. OLT), a first optical subscriber station (ONT) receiving information from the OLT through the first and second transmission paths, and receiving information from only the first transmission path from the OLT. And a second ONT and a switching unit configured to switch the second ONT and the OLT to receive information through a third transmission path when a failure occurs in the first transmission path. In addition, the method of the present invention is a first step OLT delivers the information to the first ONT through the first and second delivery path, and the information to the second ONT through the first delivery path, and the first delivery path A second step of the OLT delivering information to the first ONT via the second transmission path upon detecting a failure of the second path; and when the failure of the first transmission path is detected, the OLT transmits the third transmission path through the third transmission path. And a third step of conveying information to the ONT. Therefore, it is possible to implement an economical and efficient protection recovery function.

Wavelength Division Multiplexing Passive Optical Subscriber Network, Protection Recovery, Redundancy

Description

Apparatus and method for protection recovery of wavelength division multiplexing passive optical subscriber network {APPARATUS AND METHOD FOR PROTECTION OF WAVELENGTH DIVISION MULTIPLEXED PASSIVE OPTICAL NETWORK}             

1 is a diagram illustrating a wavelength division multiplexing passive optical subscriber network (WDM-PON) having a wavelength control and a fiber state detection circuit;

2A and 2B are diagrams showing an example of a protection recovery structure of a passive optical subscriber network (PON) proposed in G.983.5;

3 is a diagram illustrating a wavelength division multiplexing passive optical subscriber network (WDM-PON) according to an embodiment of the present invention;

4 is an operation flowchart of an optical line terminator (OLT) for performing protection recovery of a wavelength division multiplexed passive optical subscriber network (WDM-PON) according to one embodiment of the present invention;

5 is an operation flowchart of an optical subscriber station (ONT) for performing protection recovery of a wavelength division multiplexed passive optical subscriber network (WDM-PON) according to an embodiment of the present invention.

Wavelength division multiplexed passive optical network (Wavelength Division Multiplexed-Passive Optical Network, hereinafter referred to as 'WDM-PON')

Optical subscriber terminal device (Optical Network Unit / Terminal, hereinafter referred to as 'ONU' or 'ONT')

Optical line terminal (hereinafter referred to as 'OLT')

The present invention relates to a wavelength division multiplexing passive optical subscriber network (WDM-PON), and more particularly, to an apparatus and method for protection recovery of a wavelength division multiplexing passive optical subscriber network (WDM-PON) having a wavelength control and optical fiber state detection circuit. will be.

Various applications based on the Internet have resulted in a rapid increase in the Internet population and at the same time, an increase in the required bandwidth and a qualitative improvement. This trend is not limited to business subscribers, but aims to provide affordable bandwidth to end-users as they expand to residential subscribers. Therefore, the optical transmission technology used only in the existing backbone network is being extended to the subscriber network.

For example, technologies for establishing an efficient and economical optical subscriber network (e.g., optical fiber technology, wavelength division multiplexed (WDM)) technology, optical device technology (e.g., optical amplifier, optical exchange) Devices, etc.), optical fiber distribution technologies, etc., are rapidly being developed. As a result, a study on passive optical subscriber network (hereinafter referred to as 'ATM-PON' and 'E-PON') based on asynchronous transfer mode and Ethernet in the existing single star type subscriber network Is actively underway, and is currently at the commercialization stage.

In particular, the 'ATM-PON' and 'E-PON' has a structure of FTTC (Fiber To The Curb) type, but when it is evolved into FTTH (Fiber To The Home) type PON, it is limited to transmission capacity and number of subscribers. There is a problem.

In order to overcome this problem, research on WDM-PON that connects optical fibers to each home using WDM technology is being conducted in the US, Europe, and Japan. WDM-PON, a next-generation optical subscriber network, is proposed as an optical distribution structure that can provide giga-class large-capacity data service by assigning individual wavelengths to each subscriber. However, the development of WDM-PON is in its infancy, so the analysis of applicable network structure and performance indicators / limiting factors is weak. Therefore, research on the new WDM-PON structure and its key element technology is required.

In particular, as optical transmission technology having a large amount of transmission per unit time is used for subscribers, interest in protection recovery in subscriber networks (eg, WDM-PON) is increasing.

Therefore, the following techniques have been developed to implement the protection recovery function in the PON.

For example, USP 5,896,474 (PON network having a protection configuration) proposes a PON architecture that uses two splitters for protection recovery, and USP 6,327,400 (Protection scheme for single fiber bidirectional passive optical point-to multi-point network architecture). ) Discusses how each ONU in a ring structure for signal recovery selects signals using optical taps. Also, US Publication No. 2002 / 0186439A1 (Wavelength division multiplexed (WDM) ring passive optical network (PON) with route protection for replacement of splitter based passive optical networks) proposes how several ONUs form a ring network for protection recovery. In addition, EP Patent No. 1 041 852 A2-NEC (Protection switching method and apparatus for passive optical network system) proposes a method having a plurality of virtual passes per channel between the OLT and ONU for protection recovery.

However, the conventional WDM-PON protection recovery scheme as described above has a problem in that it cannot provide a differentiated service for the protection recovery and cannot provide a service for failure of a plurality of components.

Accordingly, the present invention is to provide a WDN-PON protection recovery device that duplicates the trunk line commonly used by all ONTs.

In addition, the present invention is to provide a WDN-PON protection recovery device that duplicates both the transmission and reception portion and the wavelength control and optical fiber state detection circuit in the OLT.

In addition, the present invention is to provide an apparatus and method capable of differentiated protection recovery service in WDN-PON.                         

In addition, the present invention is to provide a device that triples the trunk line by adding one more trunk line to the protected transmission and reception line of the WDN-PON.

In addition, the present invention is to provide a protection recovery apparatus and method for recovering by switching from the protection path to the recovery path when a failure occurs in the WDN-PON.

In order to achieve the above object, a protection recovery apparatus of a wavelength division multiplexing passive optical subscriber network provided by the present invention includes an optical fiber termination device connected to a network, and a first communication device configured to receive information through the first and second transmission paths from the optical fiber termination device. A first optical subscriber network device, a second optical subscriber network device which receives information from only the first transmission path from the optical path termination device, and the second optical path termination device under control of the optical path termination device when a failure occurs in the first transmission path. The optical subscriber network device and the optical fiber terminal device comprises a switching unit for switching to receive information through a third transmission path.

In addition, the protection recovery device for the wavelength division multiplexing passive optical subscriber network includes first and second optical distribution devices for forming the first to third transmission paths between the optical fiber termination device and the first and second optical subscriber network devices. The first optical splitter may further include a first transmission path between the optical fiber terminator and the first and second optical subscriber network devices, and the second optical splitter may include the optical fiber terminator and the optical fiber terminator. It is preferable to form a second transmission path between the first optical subscriber network devices. The first optical distribution device preferably forms a third transmission path between the optical fiber termination device and the first and second optical subscriber network devices when a failure occurs in the first transmission path.

Meanwhile, in order to achieve the above object, a protection recovery method of a wavelength division multiplexing passive optical subscriber network provided by the present invention provides information on a fiber optic terminator to a first optical subscriber network device through first and second transmission paths. A first step of transmitting information to the second optical subscriber network device via a first transmission path, and when detecting the failure of the first transmission path, the optical fiber termination device is the first optical subscriber network device through the second transmission path And a third step of transmitting information to the second optical subscriber network device through the third transmission path when the failure of the first transmission path is detected. It features.

At this time, the optical fiber terminal device when the failure of the first transmission path, the optical fiber terminal device shuts down the second transmission path and the first and second optical subscriber network device through the third transmission path Preferably, the method further includes a fourth step of delivering information to the user.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

1 is a diagram illustrating a wavelength division multiplexing passive optical subscriber network (WDM-PON) having a wavelength control and a fiber state detection circuit.

Referring to FIG. 1, the WDM-PON includes an OLT 10 including the wavelength control optical fiber state detection circuits 11 and 12 for transmission and reception, an ONT 40 including the wavelength control circuit 43, and the OLT ( 10) and a Remote Node (hereinafter referred to as 'RN') 30 for connecting the ONT 40. In particular, the OLT 10 outputs a plurality of output signals of the first detection circuit 11 for detecting the state of the optical fiber for transmission, the second detection circuit 12 for detecting the state of the optical fiber for reception, and the first detection circuit 11. The output signal of the ECL array 13 is multiplexed to the RN 30 based on the control signal of the first detection circuit 110 and the external cavity laser (ECL) array 13 to be divided and output as a signal of the signal. 1x (n + 1) WMUX (15) to output, 1x (n + 1) WDMX (16) to demultiplex and output the signal transmitted from RN (30), and 1x (n + 1) WDMX (16) It includes a PD (photo diode) array (14) for receiving a signal output from the.

Meanwhile, the RN 30 demultiplexes the downlink signal transmitted from the OLT 10 for each subscriber (eg, ONT) and delivers the corresponding signal to the corresponding subscriber, and each subscriber (eg, the UE). And 2x (n + 1) WMUX 32 for multiplexing uplink signals transmitted from each of the ONTs to the OLT 10. At this time, data transmitted from the 1x (n + 1) WMUX (15) of the OLT 10 to the 1x (n + 1) WDMX (31) of the RN 30 is transferred through the first optical fiber 20, and the RN Data transferred from the 2x (n + 1) WMUX 32 of 30 to the 1x (n + 1) WDMX 16 of the OLT 10 is transferred through the second optical fiber 50.

In addition, the ONT 40 receives a PD (Photo Diode) 42 which receives a downlink signal for each subscriber transmitted from 1x (N + 1) WDMX 31 of the RN 30, and an uplink signal to be transmitted to the OLT 10. And a wavelength control circuit 43 for selecting a wavelength for transmitting the upstream signal generated by the mPD 41 and the generated mPD 41.

The WDM-PON having the above configuration operates as follows.

First, the downlink transmission path from the OLT 10 to the subscriber (ONT 40), the transmission of the OLT 10 including the Optical Performance Monitor (OPM) -ECL for the wavelength alignment of the downlink path to the temperature change 1x (n + 1) WMUX (15) of the OLT (10) multiplexing the output of the ECL array (13), the ECL array (13) of the reliable wavelength controlled fiber optic state detection circuit (11), the ONT (10) for data transmission 1x (n + 1) WDMX () of the RN 30 which demultiplexes the multiplexed signal transmitted from the 1x (n + 1) WMUX 15 of the OLT 10 through the first optical fiber 20 by ONT. 31) and a receiving module (PD) 42 of the ONT 40, which is a subscriber optical receiving module.

On the other hand, the uplink transmission path from the subscriber (ONT 40) to the OLT (10), the module (mPD) 41 for generating an uplink signal in the subscriber optical transmission module ONT 40, the generated uplink signal 2x (n + 1) WMUX of the wavelength control circuit 43 of the RN 30 determining the transmission wavelength, and the RN 30 multiplexing the uplink signal for each subscriber transmitted by the wavelength determined by the wavelength control circuit 43. (32), the 1x (n + 1) NDMX (16) of the OLT 10 demultiplexing the multiplexed signal transmitted from the 2x (n + 1) WMUX 32 of the RN 30 via the second optical fiber 50. And a PD array 14 for receiving the demultiplexed signal and a receiving wavelength controlled fiber optic state detection circuit 12 for wavelength alignment of the uplink path to temperature changes.

If a change in temperature occurs in the downlink transmission path, the central optical wavelength or the optical wavelength passband (hereinafter referred to as OW) is changed. The wavelength controlled optical fiber state detection circuit 11 for transmission of the OLT 10, 1x (n + 1) WMUX 15 of OLT 10 and 1x (n + 1) WDMX 31 of RN 30. Among them, the 1x (n + 1) WDMX 31 of the RN 30 is exposed to a change in the ambient temperature because an electrical device for temperature control is not provided due to the characteristics of the PON. Therefore, OW of 1x (n + 1) WDMX 31 of RN 30 serves as a reference point. That is, the OW of the wavelength control optical fiber state detection circuit 11 for transmission of the OLT 10 and the 1x (n + 1) WMUX 15 of the OLT 10 is set to 1x (n + 1) WDMX (of the RN 30). 31) to OW. That is, the wavelength control optical fiber state detection circuit 11 and the OLT 10 for transmission of the OLT 10 are changed by changing the temperatures of PD1 and PD2 included in the transmission wavelength control optical fiber state detection circuit 11 of the OLT 10. OW of 1x (n + 1) WMUX 15 of the RN) to the OW of 1x (n + 1) WDMX 31 of the RN 30.

On the other hand, the point of change of the OW according to the temperature change in the uplink path is the mPD (41) of the ONT (40), 2x (n + 1) WMUX (32) of the RN (30), OLT (10) Wavelength control optical fiber state detection circuit 12 for reception of 1x (n + 1) WDMX 16 and OLT 10. FIG. At this time, as in the case of the downlink transmission path, it is the 2x (n + 1) WMUX 32 of the RN 30 that is exposed to the temperature change. Thus, the remaining elements align each OW with reference to the OW of 2x (n + 1) WMUX 32 of RN 30. The mPD 41 of the ONT 40 senses the OW change of the 2x (n + 1) WMUX 32 of the RN 30 and shifts the optical wavelength center of the 2x (n + 1) WMUX 32 of the RN 30. Aligned with OW, the 1x (n + 1) WDMX 16 of the OLT 10 and the wavelength controlled fiber optic state detection circuit 12 for receiving the OLT 10 are independently 2x (n + 1) of the RN 30. It detects the OW change of WMUX 32 and aligns its OW.

OW alignment of the downlink transmission is performed in the following order.

That is, the transmission wavelength control optical fiber state detection circuit 11 of the OLT 10 transmits the OW measurement light of the 1x (n + 1) WDMX 31 of the RN 30, and transmits 1x (of the RN 30). n + 1) The OW change of the 1x (n + 1) WDMX 31 of the RN 30 is detected by the intensity of light reflected by the WDMX 31 and then the corresponding action is taken.

On the other hand, OW alignment of uplink is performed independently by two loops. That is, the OW alignment of the mPD 41 of the ONT 40 is such that the optical wavelength for data transmission output from the mPD 41 of the ONT 40 is reflected by the 2x (n + 1) WMUX 32 of the RN 30. The OW misalignment of the 2x (n + 1) WMUX 32 of the RN 30 is detected from the returned optical signal strength, and the optical wavelength center of the mPD 41 of the ONT 40 is 2x of the RN 30. (n + 1) Align with the OW of the WMUX 32.

Meanwhile, the OW alignment of the OPM-ECL included in the 1x (n + 1) WDMX 16 of the OLT 10 and the second detection circuit 12 of the OLT 10 is performed by the second detection circuit of the OLT 10 ( The OW measurement light transmitted from the OPM-ECL included in 12) is reflected by the 2x (n + 1) WMUX 32 of the RN 30 and returned by the 2x (n + 1) WMUX of the RN 30. Detect changes in OW of (32) and take appropriate action.

2A and 2B are diagrams showing an example of a protection recovery structure of a passive optical subscriber network (PON) proposed in G.983.5.

FIG. 2A shows only a line card (eg, an Optical Distribution Network (ODN) interface card 61a, 62a) included in the OLT 60a and a trunk line T1, T2 extending from the line cards 61a and 62a. It is a redundant structure. This structure is a structure that duplicates only the parts that each ONT uses in common, and it is economical by not redundancy in the ONT part which has a large number compared to one OLT. And since the control path control is required only in OLT, the control method is simple. However, it is difficult to recover the branch portions (l1, l2) when a failure occurs and cannot accommodate various ONTs.

On the other hand, Figure 2b is a double structure of all parts of the network has a disadvantage of good protection recovery efficiency but high installation cost.

3 is a diagram illustrating a wavelength division multiplexing passive optical subscriber network (WDM-PON) according to an embodiment of the present invention. 3 illustrates a PON form in which a plurality of ONTs 310 and 320 are connected to one OLT 100 through RNs 210 and 220. Referring to FIG. 3, all parts commonly used to add a protective recovery function to all ONTs 310 and 320 (eg, RN 210 and 220 and state detection circuits 113 and 115 of OLT 100). An example of the hardware duplication of 123, 125) and l3) is shown. Referring to FIG. 3, it can be seen that the optical switches 111 and 121 and the recovery paths 1 and 2 are added to the protection paths 1 and 4. Therefore, the WDM-PON according to an embodiment of the present invention requests the ONT 310 and the ONT 320 by selecting the protection paths 1 and 4 or the recovery paths 1 and 5 using the optical switches 111 and 121. According to the protection recovery function can be performed.

4 is a flowchart illustrating an operation of an optical line terminator (OLT) for performing protection recovery of a wavelength division multiplexed passive optical subscriber network (WDM-PON) according to an embodiment of the present invention.

3 and 4, the OLT 100 first checks whether a monitoring signal from the ONT 310 or 320 is received (401).

As a result of the check 401, the OLT 100 detects a signal failure (SF), a failure phenomenon in which no signal is detected for a predetermined time, hereinafter referred to as SF, or a signal degradation, or attenuation or dispersion of a signal. When the monitoring signal is received, the control unit 406 checks whether the signal is misalignment (406), and if it is misalignment, adjusts the WMUX or ECL of the OLT 100 (407). In addition, after performing the process 407, it is again checked whether or not misalignment is performed (408). If the misalignment is still misaligned, the RN 210 is notified of the failure (operator) (404). That is, if the OLT 100 requests retransmission of a signal upon detecting a failure caused by SF or SD, and determines that the retransmitted signal is also caused by SF or SD, it is determined that a failure occurs in the RN 210 (ie, a transmission path). This is to inform the operator.

 On the other hand, if the OLT 100 does not receive the monitoring signal as a result of the check 401, the OLT 100 determines that the protection path l1 being used is disabled and operates the optical switch (402). That is, the switch 111 is driven to select the recovery path l2.

If the signal through the recovery path L2 is misalignment (403), it is checked whether the signal through the recovery path L2 is misalignment. operator), otherwise the OLT 100 exchanges information with the ONT 310 or 320 via a recovery pass l2. For example, the OLT 100 receives uplink data transmitted from the ONT 310 or 320.

5 is a flowchart illustrating an operation of an optical subscriber station (ONT) for performing protection recovery of a wavelength division multiplexed passive optical subscriber network (WDM-PON) according to an embodiment of the present invention.

As illustrated in FIG. 3, the device of the present invention is redundant with all devices for connection between ONT 310, 320 and OLT 100. Thus, the apparatus illustrated in FIG. 3 always has two passes independent of ONT 310. Accordingly, the ONT 310 may always select a signal having a good signal level from two signals.

3 and 5, an operation of an optical subscriber station (ONT) 320 for performing protection recovery of a wavelength division multiplexed passive optical subscriber network (WDM-PON) according to an embodiment of the present invention is as follows. same. First, the ONT 310 or 320 checks whether a monitoring signal from the OLT 100 is received (501).

As a result of the check 501, if the ONT 310 or 320 receives the monitoring signal by SF or SD, it is again checked whether the signal is misalignment (506). If the ONT 310 is misalignment, the ONT 310 is checked. Or ECL of 320). In addition, after performing the process 507, the misalignment is again checked (508). If the misalignment is still present, the ONT 310 or 320 notifies the operator of the fact (504).

If the signal through the recovery path L2 is misalignment (403), it is checked whether the signal through the recovery path L2 is misalignment. the operator, otherwise the ONTs 310, 320 receive the uplink data via the recovery pass l2. That is, the service is provided.

On the other hand, if the check 501, the ONT (310 or 320) did not receive the monitoring signal, the ONT (310 or 320) receives the downlink data through the recovery path (L2) (502). That is, the service is provided.

The ONT 310 or 320 receiving the downlink data through the recovery path L2 checks whether the signal is misalignment (503), so that the signal through the recovery path L2 is misaligned (503). misalignment), a failure of the RN 210 is notified to the operator (504), otherwise the ONT 320 receives the uplink data through the recovery pass (l2). That is, the service is provided (505). At this time, the ONT 310 is not available for service.

 In the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the equivalent of claims and claims.

As described above, the present invention has the effect of providing a basic protection recovery function by redundancy of all parts shared by all ONTs. In particular, for an ONT that requires a special priority, there is an effect of providing a protective recovery function suitable for the request. In addition, the present invention avoids redundancy of the branch line connecting all ONTs compared to the conventional method of duplexing the entire network, and duplicates the branch line only for ONTs requiring priority. Instead, a trunk line is installed to protect the ONTs that do not have redundant branch lines. Therefore, protection recovery performance is not very different from the case of redundancy. However, by reducing the redundancy of the relatively large number of ONT line cards and branch lines, the price of the entire network can be reduced.

Claims (15)

delete In the protection recovery device of the wavelength division multiplexing passive optical subscriber network, An optical fiber termination device connected to the network; A first optical subscriber network device for receiving information from the optical ray termination device through first and second transmission paths; A second optical subscriber network device for receiving information from the optical ray termination device only through a first transmission path; And a switching unit configured to switch the second optical subscriber network device and the optical fiber terminal device to receive information through a third transmission path when a failure occurs in the first transmission path. And first and second optical splitters for forming the first to third transmission paths between the optical path terminator and the first and second optical subscriber network devices. Network protection recovery device. The method of claim 2, The first optical distribution device forms a first transmission path between the optical ray termination device and the first and second optical subscriber network devices, And the second optical distribution device forms a second transmission path between the optical fiber terminator and the first optical subscriber network device. The method of claim 3, wherein the first optical distribution device And a third transmission path between the optical fiber terminator and the first and second optical subscriber network devices when a failure occurs in the first transmission path. The apparatus of claim 2, wherein the first optical subscriber network device And a signal having a large signal level is selected from information simultaneously transmitted through the first and second transmission paths. According to claim 2, wherein the optical fiber terminal device When the failure occurs in the first transmission path, the second transmission path is shut down and controlled to connect the optical fiber terminating device and the first and second optical subscriber network device only through the third transmission path. Protection Recovery Device for Multiplexed Passive Optical Subscriber Networks. 7. The optical fiber terminal of claim 6, wherein And if the optical signal is not transmitted for a predetermined time in the first transmission path, determining that a failure occurs in the first transmission path. 7. The optical fiber terminal of claim 6, wherein When a signal transmission error occurs in the first transmission path, a request for retransmission of the signal is required, and when an error occurs in the signal transmitted in response, the wavelength division multiplexing passive optical is characterized in that the failure in the first transmission path. Protection recovery device of subscriber network. delete A method for restoring protection of a wavelength division multiplexed passive optical subscriber network, A first step of the optical fiber terminal device transmitting information to the first optical subscriber network device through the first and second transmission paths, and transmitting the information to the second optical subscriber network device through the first transmission path; A second step of, when the failure of the first transmission path is detected, the optical fiber terminal device transmitting information to the first optical subscriber network device through the second transmission path; In response to detecting the failure of the first transmission path, the optical fiber terminal includes a third step of transmitting information to the second optical subscriber network device via a third transmission path, And the first step is that the optical fiber termination device simultaneously transmits information through the first and second transmission paths. The method of claim 10, A fourth step of, upon detecting a failure of the first transmission path, the optical fiber terminating device shuts down the second transmission path and transmits information to the first and second optical subscriber network devices through the third transmission path; The protection recovery method of the wavelength division multiplexed passive optical subscriber network further comprises. The method of claim 11, And the optical fiber terminator determines that a failure occurs in the first transmission path when the optical signal is not transmitted for a predetermined time in the first transmission path. The method of claim 11, The optical fiber terminating device requests retransmission of a signal when a signal transmission error occurs in the first transmission path, and determines that a failure occurs in the first transmission path when an error occurs in the signal transmitted in response. Protection Recovery Method for Wavelength Division Multiplexing Passive Optical Subscriber Network. A method for restoring protection of a wavelength division multiplexed passive optical subscriber network, A first optical subscriber network device simultaneously receiving information from the optical fiber terminator via first and second transmission paths, and a second optical subscriber network device receiving information from the optical fiber terminator through the first transmission path; With step 1, A second step of receiving, by the first optical subscriber network device, information having a greater signal level among information transmitted through the first and second transmission paths; And upon detecting a failure of the first transmission path, the first optical subscriber network device receives the information through the third transmission path and the second optical subscriber network device includes the third step of receiving information through the second transmission path. A method for recovering and protecting a wavelength division multiplexing passive optical subscriber network, comprising: The method of claim 14, And detecting, by the second optical subscriber network device, information through the third transmission path when detecting a failure of the first transmission path.

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