KR100732587B1 - Apparatus and Method for Duplicating Optical Lines in the WDM-PON System - Google Patents

Abstract

The present invention relates to an apparatus and method for optical line redundancy in a WDM-PON system in which a corresponding optical line is switched when a failure occurs in an optical line in a Wavelength Division Multiplex (WDM) -Passive Optical Network (PON) system. In a WDM-PON system having an optical line termination device located at a network and a remote node for connecting to a plurality of subscriber devices, an optical fiber cable is duplicated between the optical line termination device and the remote node by an operational link and a spare link. Is done; A reception monitoring unit monitors signal loss alarms of a plurality of optical receivers provided in the optical line termination device; An optical line switching unit checks a signal loss alarm monitored by the reception monitoring unit to control switching of the redundant optical fiber cable; The optical switch control unit controls the optical line transfer operation of the optical switch under the control of the optical line transfer unit, whereby the optical switch performs the optical line transfer from the operational link of the redundant optical fiber cable to the spare link or vice versa. By characterized in that, even in the case of disconnection and failure of the optical line can provide a continuous and stable service to the subscriber through the economical optical line transfer immediately without a long service interruption.

Description

Apparatus and Method for Duplicating Optical Lines in the WDM-PON System

1 is a block diagram illustrating a typical Wavelength Division Multiplex (WDM) -Passive Optical Network (PON) system.

2 is a view showing the configuration of an optical line redundancy device in a WDM-PON system according to an embodiment of the present invention.

3 is a flowchart illustrating a method for duplexing optical lines in a WDM-PON system according to an exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

210: reception monitoring unit 220: optical line switching unit

230: optical switch control unit 240: optical switch

251, 252: redundant fiber optic cable

260: optical splitter

The present invention relates to an apparatus and method for optical line redundancy in a WDM-PON system, and more particularly, to an apparatus and method for optical line redundancy in a WDM-PON system, in which a corresponding optical line is switched when an optical line in the WDM-PON system fails. It is about.

A typical WDM-PON system, that is, a wavelength division multiplexing passive optical network system, as shown in FIG. 1, has an optical line terminal (OLT) 100, one optical fiber cable 110, and a remote node. And a plurality of subscriber stations (130-1 to 130-N). 1 is a diagram illustrating a configuration of a WDM-PON using a conventional non-coherent broadband light source (BLS).

The OLT 100 is an optical line termination device located at a central base station, and includes a plurality of optical transmitters 101-1 to 101-N, a plurality of optical receivers 102-1 to 102-N, and a plurality of optical fibers. Filters 103-1 to 103-N, 1 * N wavelength multiplexer / demultiplexer 104, optical filter 105, A-band incoherent light source 106-1, and B-band incoherent The light source 106-2, the optical circulators 107-1 and 107-2, and the optical filter 108 are comprised. Here, the optical transmitters 101-1 to 101 -N perform an operation in a band of incoherent light injected from the corresponding A-band light source 106-1. The optical filters 103-1 to 103-N, 105, and 108 perform combination and separation of wavelengths.

The optical fiber cable 110 connects the OLT 100 and the remote node 120, and transmits a signal in which multiple wavelengths of up and down are multiplexed. In addition, each of the subscriber devices 130-1 to 130 -N from the remote node 120 may have a demultiplexed downward wavelength or an uplink wavelength output from each of the subscriber devices 130-1 to 130 -N. A specific wavelength is made to transmit through each fiber optic cable.

The remote node 120 serves to connect to each of the subscriber devices 130-1 to 130 -N, and includes a 1 * N wavelength multiplexer / demultiplexer 121.

Each of the subscriber devices 130-1 to 130 -N is an optical terminal device positioned at the subscriber side as an optical network terminal (ONT) or an optical network unit (ONU), and includes optical filters 131-1 to 131-N. And optical transmitters 132-1 to 132-N and optical receivers 133-1 to 133-N, respectively. Here, the optical transmitters 132-1 to 132 -N operate in a band of incoherent light injected from the B-band light source 106-2 of the OLT 100. The optical filters 131-1 to 131-N perform wavelength combining and separation.

And, it is composed of an optical distribution network (Optical Distribution Network) including the optical fiber cable 110 and the wavelength multiplexer / demultiplexer 121 of the remote node 120, wherein the OLT 100 of the central base station and The wavelength multiplexed signal is transmitted between the wavelength multiplexer / demultiplexer 121 through a single optical fiber cable 110, and the optical multiplexer 121 from the wavelength multiplexer / demultiplexer 121 to the optical subscriber (that is, ONT or ONU) Specific wavelengths with demultiplexed wavelengths are allocated and transmitted.

The operation of the conventional WDM-PON system having the configuration as described above is as follows.

First, in the case of an uplink signal from the optical subscriber to the central base station, the B-band optical signal output from the B-band light source 106-2, which is an incoherent broadband light source in the OLT 100 of the central base station, is the second light. Optical transmitter 132 in each subscriber device 130-1 to 130-N via circulator 107-2 and optical filter 108 via a wavelength multiplexer / demultiplexer 121 at the remote node 120. -1 ~ 132-N) to create a wavelength-locked light source.

Accordingly, the wavelength-locked signal in the B band is transmitted to the optical receivers 102-1 to 102-N of the OLT 100 through the wavelength multiplexer / demultiplexer 121 in the remote node 120. .

Second, in the case of a downlink signal from the central base station to the optical subscriber, the A-band optical signal output from the A-band light source 106-1, which is an incoherent broadband light source in the OLT 100 of the central base station, is the first light. Through the circulator 107-1 and the optical filter 105, the light is injected into the optical transmitters 101-1 to 101 -N through the wavelength multiplexer / demultiplexer 104 to form a wavelength-locked light source.

Thus, the wavelength-locked signal in the A band is transmitted to the optical receivers 133-1 to 133 in each subscriber device 130-1 to 130-N through the wavelength multiplexer / demultiplexer 121 in the remote node 120. -N).

However, in the WDM-PON system using the conventional non-coherent broadband light source as described above, OLT by having a bidirectional forming network structure that simultaneously transmits the up and down wavelengths between the OLT and the remote node to one optical fiber cable, From the multiplexer to the wavelength multiplexer / demultiplexer of the remote node, uplink and downlink multiplexed signals are transmitted through one optical fiber cable. At this time, when the cutting and failure of the optical fiber cable occurs, the service of a plurality of subscribers is impossible at the same time, there was a problem that it takes a long time to find a cutting place or to perform the replacement of the optical fiber cable. Therefore, subscribers have a problem that they cannot use the service for a long time until the optical path is restored.

In order to solve the problems described above, the present invention provides an apparatus and method for optical line redundancy in the WDM-PON system to switch the optical line when the optical line in the WDM-PON system failure. There is a purpose.

In addition, the present invention provides a stable service to subscribers through economical optical line switching in the WDM-PON system, an object thereof.

In addition, the present invention is an optical fiber cable which transmits multiplexed wavelengths of multiple subscribers between the OLT of a central base station and the wavelength multiplexer / demultiplexer of a remote node of an optical distribution network in a WDM-PON system using an incoherent broadband light source. Redundant and detects the cutting and failure of the working link among the duplicated fiber optic cables, and transfers the working link to the protection link for a long time even in the case of cutting and failure of the optical line. Its purpose is to provide continuous and stable service without interruption of service.

In the WDM-PON system according to an embodiment of the present invention for achieving the above object, the optical line redundancy apparatus includes an optical line termination device located at a central base station and a remote node for connecting to multiple subscriber devices. A WDM-PON system, comprising: a fiber optic cable duplexed between an operational link and a spare link between the optical line termination device and the remote node; An optical switch for performing optical line switching from an operational link of the redundant optical fiber cable to a spare link or vice versa; A reception monitoring unit for monitoring signal loss alarms of a plurality of optical receivers provided in the optical line termination device; An optical line switching unit for controlling switching of the redundant optical fiber cable by checking a signal loss alarm monitored by the reception monitoring unit; And an optical switch controller configured to control an optical line transfer operation of the optical switch according to the control of the optical line transfer unit.

Preferably, the optical switch is installed and operated in the optical line termination device.

And, in the WDM-PON system according to an embodiment of the present invention, the optical line redundancy device is installed and operated in the remote node, distributes the multiplexed wavelengths of a plurality of subscribers applied from the remote node to transfer to the redundant optical fiber cable It characterized in that it further comprises a light distributor for.

And, if the signal loss alarm is not released even after performing the switching control of the redundant optical fiber cable, the optical line switching unit to perform the switching control of the redundant optical fiber cable again after a delay for a predetermined time. It characterized in that it comprises a timer for.

Preferably, when the signal loss alarm is not released even after the switching control of the duplicated optical fiber cable is repeated a predetermined number of times using the timer, the optical line switching unit may be disconnected or interrupted. It is characterized by notifying the operator by generating an alarm indicating that there is.

Further preferably, when the signal loss alarm is released after performing the switching control of the redundant optical fiber cable, the optical line switching unit generates an alarm to notify an operator to perform an inspection on the optical line before the switching. It is characterized by.

On the other hand, the optical line redundancy method in the WDM-PON system according to an embodiment of the present invention for achieving the above object, the optical line termination unit located in the central base station, and a remote node for connecting to multiple subscriber devices; A WDM-PON system having a fiber optic cable duplexed between an operational link and a spare link between the optical line termination device and the remote node, the signal loss alarm of all optical receivers in the optical line termination device set by the operator Checking whether it has occurred; Switching optical paths from the operational link to the spare link when signal loss alarms of all the optical receivers occur; Checking whether all of the signal loss alarms are released when the optical path is switched; When all of the signal loss alarm is released, it is characterized in that it comprises a step of generating an alarm to notify the operator to perform a check on the optical path before the transfer.

In the WDM-PON system according to an embodiment of the present invention, in the optical fiber redundancy method, when all the signal loss alarms are not released when the optical line is switched, after the delay for a predetermined time set by the operator Characterized in that it further comprises the step of performing the optical line switching again.

The optical line redundancy method in the WDM-PON system according to the embodiment of the present invention includes the steps of checking whether the process of performing the optical line retransmission is repeated a predetermined number of times set by an operator; If the signal loss alarm is not released even after repeating the optical line switching a predetermined number of times, further comprising a step of alerting the operator that the optical line of all sections are cut or disturbed. .

The present invention provides a WDM-PON system using an OLT located at a central base station, a non-coherent broadband light source including a remote node and a plurality of subscriber devices, and includes a 1 x 2 optical switch on the OLT side of the central base station. A single optical splitter is provided on the wavelength multiplexer / demultiplexer side of a remote node of the optical splitter network, and the optical fiber cable, which is an optical line that transmits multiplexed wavelengths of multiple subscribers, is duplicated between the optical switch and the optical splitter. In case of disconnection or failure of the redundant fiber optic cable, it detects this and transfers the operation link to a spare link, so that continuous service is provided without interruption of service for a long time even in the case of disconnection or failure of the optical line. As far as possible, economical light transfers should provide reliable services to subscribers. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the WDM-PON system according to an embodiment of the present invention, the optical line redundancy apparatus includes a reception monitoring unit 210, an optical line switching unit 220, an optical switch control unit 230, as shown in FIG. 2. And an optical switch 240, redundant optical fiber cables 251 and 252, and an optical splitter 260.

The reception monitoring unit 210 monitors a loss of signal alarm of a plurality of optical receivers in an OLT located at a central base station, and monitors signal loss alarms of all optical receivers in the corresponding OLT. When the signal loss alarms of all the optical receivers are generated, the optical line switching unit 220 informs the optical line switching unit 220 that the optical lines should be switched.

The optical line switching unit 220 serves to control the optical line switching between the OLT and the remote node of the optical distribution network. The optical line switching unit 220 checks a signal loss alarm applied from the reception monitoring unit 210 and checks the optical line. It performs a function of giving a command to the optical switch controller 230 to switch.

In addition, the optical line switching unit 220 is provided with an internal timer 221, and if the signal loss alarm is not released after the optical line transfer command is received from an operator, the corresponding timer ( After driving 221 to delay for a predetermined time, the optical switch controller 230 again gives a command to switch the optical line. In addition, the optical line switching unit 220 prevents the optical line switching over a predetermined number of times for a predetermined time set by an operator in order to prevent the infinite repetitive operation of outputting the optical line switching command to the optical switch control unit 230. Only when one condition is satisfied, the optical switch controller 230 performs the function of giving the optical line transfer command again.

In addition, the optical line switching unit 220 is for the optical line before the transfer (that is, the operating link) when the signal loss alarm of all the optical receiver is released after the optical line switching by the cutting and interruption of the optical line. An alarm is issued to the operator to check. In addition, the optical line switching unit 220 is disconnected or interrupted in all sections when the signal loss alarm from the reception monitoring unit 210 is not released even after performing the optical line switching for a predetermined number of times. An alert is issued to notify the operator.

The optical switch controller 230 controls the optical switch 240. The optical switch control unit 230 checks the optical line transfer command applied from the optical line transfer unit 220 and controls the redundancy through 1 x 2 optical switch control. It is controlled to perform optical line switching from the operational link 251 of the optical fiber cables 251 and 252 to the spare link 252 or vice versa.

The optical switch 240 is a 1 x 2 optical switch is connected to the optical filter on the OLT side, under the control of the optical switch controller 230, the operation link of the redundant optical fiber cable (251, 252) At 251, optical path switching to the preliminary link 252 or vice versa.

The redundant fiber optic cables 251, 252 are the operational link 251 and the spare link 252 between the OLT (ie the optical switch 240) and the remote node (ie the optical splitter 260). In the normal operation, the multiplexed wavelengths of the plurality of subscribers are transmitted through the corresponding operation link 251, and the plurality of subscribers are transferred through the corresponding link 252 by the switching operation of the optical switch 240. Delivers multiplexed wavelengths

The optical splitter 260 is a 1: 2 optical splitter, which is connected to the wavelength multiplexer / demultiplexer on the remote node side, and receives the multiplexed wavelengths of multiple subscribers transmitted through the redundant fiber optic cables 251 and 252. It is applied to the wavelength multiplexer / demultiplexer on the remote node side, and conversely, the multiplexed wavelengths of multiple subscribers applied from the wavelength multiplexer / demultiplexer on the remote node side are distributed and applied to the duplicated optical fiber cables 251 and 252. do.

Referring to the operation of the optical line redundancy device in the WDM-PON system according to an embodiment of the present invention.

First, in the optical line redundancy device in the WDM-PON system according to an embodiment of the present invention, in consideration of economics, the optical line for the optical line from the wavelength multiplexer / demultiplexer to the subscriber device provided in the remote node of the optical distribution network Transfer should not be considered.

However, the redundant optical fiber cables 251 and 252, that is, the operational link 251 and the redundant link for the optical path from the OLT located in the central base station multiplexed by the multiple subscribers to the wavelength multiplexer / demultiplexer of the remote node. 252 to be installed.

In addition, a 1 x 2 optical switch 240 is installed on the OLT side, and a 1: 2 optical splitter 260 is installed on the remote node side, and then the 1 x 2 optical switch 240 and a 1: 2 optical splitter ( The operation link 251 and the preliminary link 252 are installed between 260 to operate as shown in FIG. 2.

And, as shown in Figure 2, the reception monitoring unit 210 for monitoring signal loss from the plurality of optical receivers on the OLT side, the optical switch control unit 230 for operating the optical switch 240, and the inside It includes a light line switching unit 220 having a timer 221 and controls the light line switching.

In the WDM-PON system according to the embodiment of the present invention having the configuration as described above, a plurality of optical transmitters on the OLT side is a non-coherent broadband light source (ie, BLS) of the OLT side and the remote node side The wavelength multiplexer / demultiplexer amplifies and outputs the light source at a wavelength that matches the wavelength of the divided light source.

Accordingly, the optical line switching unit 220 of the OLT side determines whether the optical output of which wavelength is locked by the optical transmitter of the subscriber device side is normally input to the optical receiver of the OLT side to cancel the signal loss of all the optical receivers. Reported from the reception monitoring unit 210, thereby operating the optical switch control unit 230 to perform the optical line switch from the operational link 251 to the spare link 252, or the spare link In the case of operation 252, the optical line switch is performed from the spare link 252 to the operation link 251.

This is because a wavelength-locked WDM-PON system using an incoherent broadband light source has a feature in that a signal loss alarm of a corresponding optical receiver is released when an incoherent broadband light source is input to the optical transmitter.

In other words, when a signal loss alarm occurs in all the optical receivers on the OLT side, firstly, an incoherent broadband light source is interrupted due to the disconnection and interruption of the optical path from the OLT to the wavelength multiplexer / demultiplexer of the remote node. This is a case where the wavelength lock is not generated because it is not input to the optical transmitter on the subscriber device side, and secondly, all the optical lines from the wavelength multiplexer / demultiplexer of the remote node to the subscriber device are cut and interrupted. This is a case where wavelength locking does not occur because an incoherent broadband light source is not input to the optical transmitter on the subscriber device side. Third, a large external shock or pressure to prevent the wavelength multiplexer / demultiplexer of the remote node from performing normal operation. If you receive.

However, except for the first case, the probability of occurrence of the second and third cases is very small, and accordingly, the optical line switching unit 220 uses the signal loss alarm of the optical receiver to Determination of switching is desirable in wavelength locked WDM-PON systems using incoherent broadband light sources.

Then, the optical line redundancy method in the WDM-PON system according to an embodiment of the present invention will be described in detail with reference to the flowchart of FIG. 3.

First, the reception monitoring unit 210 monitors signal loss alarms of a plurality of optical receivers in an OLT located at a central base station, and monitors signal loss alarms of all optical receivers in the corresponding OLT to monitor signal loss alarms of all the optical receivers. When is generated, the optical path switching unit 220 is notified that the optical path should be switched.

Accordingly, the optical line switching unit 220 confirms the signal loss alarm applied from the reception monitoring unit 210 and commands the optical switch control unit 230 to switch the optical line.

In other words, the optical line switching unit 220 receives the signal loss alarm of all the optical receivers set by the operator from the reception monitoring unit 210, and checks whether the signal loss alarm of all the optical receivers has occurred ( Step S301).

If the signal loss alarm of all the optical receivers does not occur in the step 301 (S301), the optical line switching unit 220 is a light between the OLT of the central base station and the wavelength multiplexer / demultiplexer of the remote node. It is recognized that the track is operating normally, and thus the process returns to the operation of the step S301 (step S302).

However, if the signal loss alarm of all the optical receivers is generated in the step 301 (S301), the optical line switching unit 220 is cut or cut to the current operation link 251 of the redundant optical fiber cable (251, 252) Recognizing that a failure has occurred, the optical switch control unit 230 is operated to switch the optical path from the operation link 251 to the spare link 252 (S303).

In other words, the optical switch controller 230 confirms the optical line transfer command applied from the optical line transfer unit 220 and controls the spare link 252 at the operation link 251 through 1 x 2 optical switch control. To control the optical path switching of the furnace, and the 1 x 2 optical switch 240 controls the optical path switching from the operation link 251 to the spare link 252 under the control of the optical switch controller 230. Will be performed.

Accordingly, in the state where the optical line is switched by the above-described operation, the optical line switching unit 220 reports whether the signal loss alarm of the optical receiver is released from the reception monitoring unit 210 continuously. In this case, it is checked whether all signal loss alarms of the optical receiver are released (step S304).

If all the optical signal loss alarms are released in step 304, the optical line switching unit 220 generates a check alarm for the optical line, that is, the optical line before the transfer (ie, the operation). Link 251) generates an alarm to notify the operator to perform the check (step S305), and then returns to the step 302 (S302) to recognize the optical line condition again and perform the operation again. .

However, even though the optical line switching is performed in the above-described operation, if all the optical signal loss alarms are not released in step 304, the optical line switching unit 220 may use the internal timer 221. ) To prepare for the following occurrence by delaying for a certain time.

Firstly, the disconnection and failure of the switched optical line (ie, the preliminary link 252) occurs, and secondly, a fatal failure or destruction of the wavelength multiplexer / demultiplexer including the optical splitter 260 occurs. The third case is a case where all the lines from the wavelength multiplexer / demultiplexer of the remote node to the subscriber device are cut off and a failure occurs. The fourth case is an abnormal operation of the optical switch 240.

Then, after a predetermined time set by the operator (step S306), the optical line switching unit 220 issues an optical line transfer command to the optical switch control unit 230 again, which is the operation of the step 303 (S303). Try to carry out the fiber switch again.

At this time, in order to prevent the infinite repetitive operation of outputting the optical line transfer command to the optical switch control unit 230, the optical line transfer unit 220 to prevent the switching of the optical line more than a predetermined number of times for a predetermined time set by the operator. Only when one condition is satisfied, the optical switch control unit 230 issues the optical line transfer command again to perform the optical line transfer operation.

That is, the optical line switching unit 220 issues the optical line transfer command to the optical switch control unit 230 by the predetermined number of times to determine whether the optical line transfer operation is repeatedly performed (step S307), and the optical line transfer operation If the operation is not performed the predetermined number of times, the operation of the step 303 (S303) is repeated.

On the other hand, when the signal loss alarm from the reception monitoring unit 210 is not released even after continuously performing the optical line switching for the predetermined number of times, the optical line switching unit 220 is connected to the optical line in all sections. An alarm indicating that there is a cutoff or a failure is generated and the operator is notified (step S308).

Although the preferred embodiment of the present invention has been described above, it should be well understood that the present invention may use various changes, modifications, and equivalents, and that the above embodiments may be appropriately modified in the same manner.

For example, in the case of the wavelength-locked WDM-PON system using the incoherent broadband light source, the optical transmitter of the subscriber device may be applied to operate by receiving an external light source of the OLT located in the central base station.

In addition, in the case of the WDM-PON system, a distributed feedback laser (ie, DFB LD) or an external resonator laser (ie, an external cavity laser (ECL)) having a single wavelength instead of an incoherent broadband light source. By using a wavelength multiplexer / demultiplexer into a single multiplexed light source.

Accordingly, it should be understood that the optical feedback of the subscriber device can be applied to a WDM-PON system using an R-SOA using a distributed feedback laser or an external resonator laser having a single wavelength in the OLT located at the central base station.

It should also be appreciated that the WDM-PON system employs a non-interfering broadband light source and the optical transmitter may be used for R-SOA or FP-LD.

Accordingly, it is to be understood that the above description does not limit the scope of the invention as defined by the following claims.

As described above, in the WDM-PON system using a non-coherent broadband light source according to the present invention, an optical line for delivering multiplexed wavelengths of multiple subscribers between an OLT of a central base station and a wavelength multiplexer / demultiplexer of a remote node of an optical distribution network. Redundant fiber optic cables are duplexed, and the operation link of the redundant fiber optic cable is detected and the operation link is switched to a spare link, so that even when the fiber line is cut and failed, service can be stopped for a long time. Economical fiber-optic switching can provide subscribers with consistent and reliable service.

Claims (9)

A WDM (Wavelength Division Multiplex) -PON (Passive Optical Network) system having an optical line termination device located at a central base station and a remote node for connecting to a plurality of subscriber devices, An optical fiber cable duplexed with an operational link and a spare link between the optical line termination device and the remote node; An optical switch for performing optical line switching from an operational link of the redundant optical fiber cable to a spare link or vice versa; A reception monitoring unit for monitoring signal loss alarms of a plurality of optical receivers provided in the optical line termination device; An optical line switching unit for controlling switching of the redundant optical fiber cable by checking a signal loss alarm monitored by the reception monitoring unit; Including an optical switch control unit for controlling the optical line transfer operation of the optical switch in accordance with the control of the optical line transfer unit, If the signal loss alarm is not released even after performing the switching control of the redundant optical fiber cable, the optical line switching unit includes a WDM timer for performing the switching control of the redundant optical fiber cable again after a predetermined time. -Optical redundancy device in PON system. The method of claim 1, The optical switch is an optical line redundancy device in the WDM-PON system, characterized in that installed in the optical line termination device. The method of claim 1, An optical line in the WDM-PON system, which is installed and operated at the remote node, and further comprises an optical splitter for distributing the multiplexed wavelengths of the plurality of subscribers applied from the remote node and transferring the multiplexed wavelengths to the redundant optical fiber cable. Redundancy device. delete The method of claim 1, The optical line switching unit is an alarm for notifying that the optical line of all the sections are disconnected or interrupted when the signal loss alarm is not released even after the switching control of the redundant optical fiber cable is repeated a predetermined number of times using the timer. Optical fiber redundancy device in the WDM-PON system, characterized in that for generating a notification to the operator. The method of claim 1, When the signal loss alarm is released after performing the switching control of the redundant fiber optic cable, the optical line switching unit generates an alarm to notify an operator to perform an inspection on the optical line before the switching. -Optical redundancy device in PON system. WDM (Wavelength Division) having an optical line termination device located at a central base station, a remote node for connecting to multiple subscriber devices, and a fiber optic cable duplexed between the optical line termination device and the remote node by an operational link and a spare link. As a method of duplexing optical paths of a Multiplex) -Passive Optical Network (PON) system, Checking whether a signal loss alarm has occurred for all the optical receivers in the optical line termination device set by the operator; Switching optical paths from the operational link to the spare link when signal loss alarms of all the optical receivers occur; Checking whether all of the signal loss alarms are released when the optical path is switched; When all of the signal loss alarms are released, generating an alarm to notify an operator to perform a check on the optical path before the switching; If the signal loss alarm is not released in the state that the optical line is switched, the optical line redundancy method in the WDM-PON system comprising the step of performing the optical line switching again after a certain time. delete The method of claim 7, wherein Checking whether the process of performing the optical path switching again is repeated a predetermined number of times set by an operator; If the signal loss alarm is not released even after repeating the optical line switching for a predetermined number of times, further comprising the step of alerting the operator that the optical line of all sections are disconnected or faulty Fiber Channel Redundancy in WDM-PON Systems.

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