KR101682805B1

KR101682805B1 - The line duplexing Passive Optical Network system, method for detecting received signal of standby line thereof

Info

Publication number: KR101682805B1
Application number: KR1020150060898A
Authority: KR
Inventors: 정수필; 이경훈
Original assignee: 주식회사 엘지유플러스; (주)유비쿼스
Priority date: 2015-04-29
Filing date: 2015-04-29
Publication date: 2016-12-05
Also published as: KR20160128853A

Abstract

A PON trunk duplication system for detecting a received light level of a preliminary trunk line of the present invention is a system in which an optical line terminal apparatus and a plurality of optical telecommunication terminal apparatuses are duplexed into an operation trunk line and a spare trunk line, A PON trunk duplication system in which a traffic is protected and switched from the operation trunk line to the backup trunk line when a fault occurs, the system comprising: a light sensitivity value receiving from the optical communication terminal apparatus based on dynamic bandwidth allocation (DBA) A standby PON port for acquiring a light sensitivity value received from the optical communication terminal device on the basis of an idle time and a reception light sensitivity value provided from the spare PON port to a circle queue Cumulatively stores the maximum received light level, extracts the maximum received light level from the latest information among the accumulated information, Includes a CPU that determines the status of the spare trunk line by using the maximum received optical level. According to the configuration of the present invention as described above, it is possible to reliably determine the intensity of the received optical signal of the preliminary trunk line.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a PON trunk line redundancy system and a method for detecting a received light level of the trunk line,

The present invention relates to a passive optical network trunk duplication system and a method for detecting a received light level of a redundant trunk line in the trunk duplication system. More particularly, the present invention relates to an optical line termination apparatus on the service provider side and an optical communication terminal apparatus In the PON trunk line redundancy system in which traffic is switched from the operation trunk line to the spare trunk line under the control of the CPU when an event occurs in the trunk line in use and the trunk line is duplicated to the trunk line and the spare trunk line in use, Despite the switchover, we want to measure the received optical sensitivity of the preliminary trunk line in order to prevent the service from being maintained still due to an accident such as cutting the optical fiber in the waiting preliminary trunk line.

For this purpose, the stability of the preliminary trunk line is directly detected by directly detecting the level of the received light of the preliminary trunk line, the optical signal is periodically detected at the spare PON port so that the operator can easily recognize the state of the preliminary trunk line, In order to check the state of the preliminary trunk line by storing in the circle queue of the CPU and to increase the reliability of the measurement of the received light sensitivity and the reliability of the judgment, the size of the circle queue is maintained 300 times or more, And extracts a more reliable result compared to the received light sensitivity information of the line. If the maximum value of the received light sensitivity of the preliminary trunk line is less than the reference value, the status of the abnormal trunk line is determined, A PON trunk duplication system that provides data to be used as a basis for judgment, And more particularly to a method of detecting a received light level of a trunk line.

In general, a passive optical network (PON) has a passive device at a remote node (RN), and connects a service provider and a plurality of optical network termination units (Optical Network Terminals) as one section. Since a passive optical network (PON) uses a passive optical device, there is no need to manage the optical device separately, and there is no need to supply power.

This passive optical network (PON) is a method of providing broadband communication service using optical fibers to subscribers, and one optical line terminal OLT functioning as a central office is connected to the remote node RN And is connected to N optical communication terminal devices (ONT or ONU). In such a passive optical network, 32 or 64 optical communication terminal devices (ONT or ONU) are usually installed in a single optical line terminal (OLT) located in the central office in the vicinity of the subscriber.

At this time, if a communication failure occurs due to a failure of the optical line terminating device (OLT) or an optical fiber cut between the optical line terminating device (OLT) and the remote node (RN), all optical communication terminal devices (ONT or ONU) So that all the subscribers can not receive the communication service due to the communication failure.

In order to solve this problem, redundancy (or port redundancy) of the optical network terminator (OLT) is proposed in a passive optical network (PON). In other words, the passive optical network system (PON) supporting redundancy has a standby OLT / spare trunk line in addition to the active OLT / operation trunk line, thereby causing a failure in the active OLT / trunk line in use , The standby OLT / spare trunk line is replaced.

However, in the passive optical network system supporting such redundancy, another problem occurs unexpectedly despite the redundancy.

If the standby line is disconnected due to the worker's carelessness during excavation work, it is often the case that the line is not in use at the moment and is roughly connected. A failure occurs in the active line of the on-line operation, and the switchover to the standby line is performed, but the standby line, which is roughly connected, fails to exhibit its function, thereby failing to have a switching effect.

Such truncation of the backup trunk line occurs more than a few times a day, resulting in unexpected service interruption despite redundancy switching.

In this way, according to the passive optical network system supporting redundancy according to the related art, the state of the spare trunk line can not be known in the OLT.

The operation is switched to the stand-by line (standby line) in which the degree of attenuation is unknown. However, when the line is switched, the light attenuation increases beyond the reference value and the switch is switched to the standby line One becomes useless. In this way, although switched to the standby line, the standby line causes a secondary problem, resulting in a more unexpected service interruption than the primary problem.

In this way, since the OLT can not operate the Received Signal Strength Indication (RSSI) function of the preliminary trunk line in the current passive optical network system structure, there is a problem that it can not judge the failure of the trunk trunk line.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating an optical transmission / reception system capable of detecting a failure in a preliminary transmission path according to the related art; FIG.

Referring to FIG. 1, a transmitting apparatus 1a includes a pair of optical transceivers 20 and 21 for transmitting and receiving optical signals, and a control unit 3 for detecting and switching faults. The one-way optical transceiver 20 can be set to the currently active system by the control unit 3 and the other optical transceiver 21 can be set to the standby preliminary system. The receiving side transmission path 7 connecting the transmission device 1a to the external device 9a is branched to the transmission paths 70 and 71 by the branching section 40, It is possible to branch to the transmission lines 80 and 81 by the transmission line 41 to realize line duplication.

At this time, an optical filter 50 is installed on one side of the transmission side transmission line 8. The light provided by the optical transceivers 20 and 21 of the transmission apparatus 1a detects the light reflected back from the optical filter 5 and the control unit 3 monitors the state of the spare transmission line 81 .

Therefore, since the light generated by the external device 9a is not directly detected but detected by the optical filter 5 and reflected by the optical filter 5, the signal of the return light, which is detected when the optical signal is weak, do.

As a result, since the optical filter 5, which reflects only a specific wavelength of light, must be provided on one side of the transmission line 8, the optical filter 5 which causes the increase of the cost and transmits the signal light and reflects only the inspection light, There is a problem that the reliability of detection is low.

Japan Specification 2014-93558

SUMMARY OF THE INVENTION It is an object of the present invention to provide a PON trunk duplication system capable of measuring a received light sensitivity directly transmitted from an optical communication terminal apparatus, A method of detecting a received light level of a line.

Another object of the present invention is to provide a PON trunk duplication system capable of measuring the received light sensitivity through only a software program change without a hardware design change in a PON port or an optical module and a method of detecting a received light level of the trunk line .

According to an aspect of the present invention, there is provided a method of detecting a preliminary trunk line receiving light level in a PON trunk duplication system, the method comprising: obtaining reception light sensitivity information of a trunk line from a spare PON port; Determining a maximum received light level among the received light sensitivity information of the preliminary trunk line by accumulating the received light sensitivity information of the preliminary trunk line by a predetermined amount or more, Level to the received light level of the operational PON port to increase the reliability, and if the maximum received light level of the spare trunk line is less than the received light level of the operational PON port, And informing the operator of the status of the abnormal primary trunk line And providing the message.

According to another aspect of the present invention, a PON trunk line redundancy system for detecting a reception light level of a preliminary trunk line is configured such that an optical line terminal apparatus and a plurality of optical communication terminal apparatuses are duplexed into an operation trunk line and a spare trunk line, A PON trunk duplication system in which traffic is protected and switched from the operation trunk line to the spare trunk line when a fault occurs in the trunk line of operation, the system comprising: A preliminary PON port for obtaining a light sensitivity value received from the optical communication terminal device on the basis of an idle time, and a reception light sensitivity value provided from the preliminary PON port, Cumulatively stored in the circle queue, searches the latest information among the accumulated information, The extraction, and using the maximum received optical level to be extracted comprises a CPU for determining the state of the spare trunk line.

According to another aspect of the present invention, there is provided a method for detecting a preliminary trunk line receiving light level in a PON trunk duplication system of the present invention, comprising the steps of: initializing a circle queue of a spare PON port, Receiving a received light sensitivity value of a preliminary trunk line from a module, storing the received light sensitivity value of the preliminary trunk line in the circle queue, extracting a maximum light level among the stored received light sensitivity values, Comparing the maximum light level with a reception sensitivity value of an operation trunk line obtained by a reception optical module of an operation PON port, and when the maximum light level is less than the reception sensitivity value of the operation trunk line, .

According to another aspect of the present invention, there is provided a method for detecting a preliminary trunk line receiving light level in a PON trunk duplication system of the present invention includes the steps of initializing a corresponding port and confirming whether or not the link is declared as a spare PON port, Acquiring the received light sensitivity information of the spare PON port using the received light sensitivity information, sequentially storing the measured light sensitivity information in the circle queue, detecting the maximum received light level in the order of the currently stored received light sensitivity information, Reporting to the operator if the maximum received light level is greater than an alarm threshold, and if the stored maximum received light level is not greater than the alarm threshold, the stored received light sensitivity information is equal to the size of the circle queue To the operator.

As described above, according to the configuration of the present invention, the following effects can be expected.

First, in the conventional PON system, it is not possible to perform the reception light sensitivity measurement function in the spare PON port. However, in the present invention, it is possible to measure the reception light sensitivity in the spare PON port and in particular, directly from the optical communication terminal Since the light level is measured using the transmitted light, the reliability of light detection is very high.

Second, the conventional optical module that does not support the RSSI function can be used as it is. In particular, it is possible to measure the receiving optical sensitivity only by the software without changing the hardware in the spare optical module or the spare PON port, Therefore, it is economical because there is no cost burden due to the design change.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of an artboard duplication system according to the prior art; FIG.
2 is a block diagram showing the configuration of a PON trunk duplication system according to the present invention;
3 is a flowchart showing a method of detecting an incoming light level of a redundant line and providing an alarm in the PON trunk duplication system according to the present invention.
4 is a flowchart illustrating a method of detecting light level of a preliminary trunk line and reporting light level information to an operator in a PON trunk duplication system according to the present invention.

Brief Description of the Drawings The advantages and features of the present invention, and how to achieve them, will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. The dimensions and relative sizes of layers and regions in the figures may be exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a PON trunk line redundancy system capable of detecting a reception light level of a preliminary trunk line according to the present invention will be described in detail with reference to the accompanying drawings.

The PON trunk duplication system capable of detecting the reception light level (signal intensity) of the preliminary trunk line according to the present invention is a system for detecting the intensity of an optical signal of each generation optical communication terminal device (ONT or ONT) .

That is, the reception light level of the preliminary trunk line is directly detected and the stability of the preliminary trunk line is determined in advance, and the preliminary trunk line is recovered before an event occurs in the trunk line, thereby preventing a fault condition in advance.

The method of detecting and determining the reception light sensitivity of the preliminary trunk line of the present invention for enabling the operator to easily know the state of the spare trunk line is performed by periodically recognizing the optical signal at the spare PON port and storing it in the circle queue of the CPU The state of the spare trunk line can be confirmed. At this time, in order to increase the reliability of the reception light sensitivity measurement and judgment, a significant accumulation value can be utilized. In particular, it is possible to extract a more reliable result by comparing the reception light sensitivity information of the spare operation PON port with the reception light sensitivity information of the operation PON port.

To this end, it is necessary to repeatedly receive the received optical sensitivity information from the spare PON port for a predetermined time, to accumulate the above information to increase reliability, to obtain a maximum value of the accumulated information, If the maximum value is less than the reference value, it is determined that the system is in an abnormal preliminary trunk line state, and an alarm is provided to the operator or data providing the basis on which the alarm is provided can be provided.

2, the passive optical network (PON) trunk redundancy system 100 includes an optical line termination 110 of an upper system installed on the operator side, a subsystem 110 installed in each household, A plurality of optical communication terminal units (Optical Network Terminals or Optical Network Units) 120 of the optical line terminating apparatuses 110 and an optical node 120 ).

The PON trunk duplication system 100 uses a passive distributor or a wavelength division multiplexing device between a subscriber access node such as an FTTH network (Fiber To The Home) or an FTTC network (Fiber To The Curb) A node can form a network in the form of a bus or tree structure. The PON circuit duplication system 100 of the present invention may have the form of an APON (Asynchronous Transfer Mode PON) or an EPON (Ethernet PON) or a GPON (Gigabit PON).

The PON trunk duplication system 100 of the present invention may include both a port duplication system in the optical line terminating apparatus 110 and an accompanying trunk line redundancy. For example, the optical splitter 130 and the optical line terminating device 110 are each provided with a redundant PON port, and an operation trunk line La and a spare trunk line Ls are respectively formed in each of the redundant PON ports Pa and Ps When a failure occurs in the PON port Pa or the operation trunk line La in use, the service can be prevented from being interrupted by switching to the spare PON port Ps and the spare trunk line Ls.

The optical line terminating device 110 includes a pair of operation PON ports Pa and a spare PON port Ps and a CPU for instructing a transfer to the standby PON port Ps of the operation PON port Pa (112).

The operation PON port Pa includes an optical module 114a that provides an optical signal to the downlink operation trunk line La or detects an optical signal from the uplink trunk line La and a PON By including the MAC chip 116a, the PON MAC chip 116a can control the optical module 114a through the I / O channel.

The spare PON port Pa also has an optical module 114s that provides an optical signal to the preliminary trunk line Ls to be downlinked or detects an optical signal from the uplink trunk line La, And a PON MAC chip 116s.

In the operation PON port Pa, the intensity of the optical wavelength transmitted from the specific optical communication terminal device ONTx is measured based on the time slot provided by the dynamic bandwidth allocation DBA of the PON MAC chip 116a can do. It is possible to detect the intensity of the light wavelength by using the idle time even if the time is not allocated by the time division method (TDM), and to easily display the state of the operation trunk line La with information on the detected reception light sensitivity Can be confirmed.

On the other hand, since the PON MAC chip 116s is not in operation and is in a standby state in the spare PON port Ps, a specific optical communication terminal apparatus ONTx) can not be detected. Therefore, only the presence or absence of the optical signal can be confirmed in the spare PON port (Ps), and the intensity of the optical wavelength can not be determined.

The present invention is not limited to the optical fiber cutting accident in the preliminary trunk line Ls, but also to the spare PON port Ps (Ps) in the case where the distance between the optical splitter 130 and each optical communication terminal apparatus 120 is remarkably different. The intensity of the received light wavelength can be determined.

The CPU 112 sets a Circle Queue to measure information about the received light sensitivity from the spare trunk line Ls for the port declared as the spare PON port Ps among the pair of ports, Initialize.

For example, since the PON MAC chip 116s of the spare PON port Ps is in the standby state, the CPU 112 measures the optical signal at a constant interval from the optical module 114s during the idle time, The light sensitivity values can be stored in order in the circle queue Cq. In order to increase the reliability of the received light sensitivity value, the size of the queue per port can be set at least 300 times or more.

The CPU 112 manages the reception optical signal information of the spare trunk line Ls based on the reception optical sensitivity value of the spare trunk line Ls stored in the circle queue Cq as described above, Ls).

The CPU 112 is mounted on a main board, and the operation and spare PON ports Pa and Ps can be mounted on a line card, respectively. The optical modules 114a and 114s may include a 1 Gigabit SFP or a 10 Gigabit XFP.

Since the operation PON port Pa and the spare PON port Ps are connected to the optical distributor 130 through the separate lines La and Ls, the optical distributor 130 is connected to the dual PON ports Pa and Ps, And a 2: N optical splitter that is responsible for optical distribution between the plurality of optical communication terminal apparatuses 130. That is, in the PON trunk duplication system 100 of the present invention, by configuring the splitter of the optical splitter 130 used in the PON section as 2: N, the optical link port of the optical line terminal 110 is operated PON port (Pa) and spare PON port (Ps).

Therefore, the optical link ports are duplicated in the optical line terminating device 110 and the optical splitter 130, and the operation trunk line La and the spare trunk line Ls correspond to the respective redundant PON ports Pa and Ps, respectively When the active PON port Pa and the operation trunk line La fail due to redundancy of the trunks, the data can be transferred to the spare PON port Ps and the spare trunk line Ls and data loss can be minimized.

The CPU 112 sets the operation PON port Pa normally operating among the pair of PON ports Pa and Ps and the spare PON port Ps prepared in advance for the event occurrence, It is determined whether the operation PON port Pa is switched to the spare PON port Ps. Therefore, the operation PON port Pa and the spare PON port Ps can be selectively activated under the control of the CPU 112. [

When the operation PON port Pa fails to recover from the standby PON port Ps and the standby PON port Ps is switched to the standby PON port Ps, And the operation PON port Pa and the spare PON port Ps are relative to each other since the operation PON port Pa is set to the spare PON port Ps.

The problem is that even if the spare trunk line Ls is not normal, the failure occurs in the trunk line La and is transferred to the spare trunk line Ls, the subscriber can not normally receive service despite the repair. The PON trunk duplication system 100 of the present invention periodically determines the strength of the optical signal at the spare PON port Ps by using a method of detecting the level of the received light of the spare trunk line Ls, 112 so that the line operator can determine whether the optical signal is normal or not in the preliminary trunk line Ls.

Hereinafter, a method of notifying the line operator of the fact that the received light intensity of the preliminary trunk line is less than the reference value will be described.

Referring to FIG. 3, the operation PON port Pa and the spare PON port Ps are relative. The operation PON port Pa can be changed to the standby PON port Ps (S110) when an event occurs in the operation trunk line La and the operation PON port Pa is switched to the standby PON port Ps. At this time, the CPU 112 initializes the circle queue Cq of the changed spare PON port Ps (S120).

It is confirmed whether the spare PON port Ps is linked (S130). If the link is uplinked, the optical module 114s receives the received optical sensitivity value (S140). The received optical sensitivity value is a value directly received from the optical communication terminal device 130.

In order to increase the reliability of the measured reception light sensitivity value, it is possible to determine the effectiveness of the reception light sensitivity value (S150). For example, it may be limited to a case where the light sensitivity value received from the spare trunk line Ls is at least -30 dB, preferably -28 dB. Therefore, it is preferable that the measured reception light sensitivity value is -28 dB to -5 dB.

And stores the received light sensitivity value measured at the spare PON port Ps in the circle queue Sq. For example, the received light sensitivity data is stored in the circle queue Cq when the received light sensitivity value is larger than the predetermined value (e.g., -28 dB) (S27), for example, -27 dB to -5 dB.

The maximum received light sensitivity value Max among the stored received light sensitivity data is compared with the received light sensitivity value provided from the operation trunk line La at the currently activated operation PON port Pa at step S170. For example, when the reception light sensitivity value of the spare PON port Pa is -32 dB and the reception light sensitivity value of the operation PON port Pa is -29 dB, an alarm is provided to the operator if the former value is not larger than the latter value do. The reason why the largest light level among the reception light sensitivity information of the spare trunk line Ls is smaller than the reception light level of the operation trunk line La is that the event is generated in the spare trunk line Ls.

Hereinafter, a method of detecting and storing the received light sensitivity information of the preliminary trunk line and reporting it to the line operator will be described.

Referring to FIG. 4, the state of the spare trunk line Ls is periodically measured at the spare PON port Ps, and the received light sensitivity information is determined by a predetermined criterion to provide the operator with the received light sensitivity information. It is possible to grasp the overall situation including the abnormality of the spare main line (Ls) and the like.

Therefore, when the operator desires to inquire the reception light sensitivity information of the preliminary trunk line Ls, the report may proceed in the following order.

If it is declared as a spare PON port (Ps), the corresponding port is initialized and it is checked whether it is activated (S210).

Since the spare PON port Ps does not operate the dynamic bandwidth allocation (DBA), the reception light sensitivity information can be obtained only by using the idle time (S220).

The measured reception light sensitivity information is sequentially stored in the circle queue Cq (S230).

The maximum received light level among the accumulated received light sensitivity information starting from the currently stored received light sensitivity information is detected (S240).

If the maximum received light level is greater than the alarm threshold (e.g., -28 dB to -30 dB) (e.g., -5 dB to -27 dB), report to the operator (S250).

Even when the maximum received light level is not greater than the alarm threshold (for example, the level is -31 dB or less, usually expressed as -40 dB), the received light sensitivity information stored is equal to the size of the circle queue Cq (for example, 300 times) And reports the data to the operator (S260).

Therefore, when the maximum received light level is not larger than the alarm threshold value and the row data does not reach the size of the circle queue Cq, the reliability of the data can not be ensured and the operator is not informed.

As described above, according to the present invention, the optical signal of the optical communication terminal device is directly obtained from the preliminary trunk line to increase the reliability of the reception light level measurement, and the strength of the reception optical signal of the preliminary trunk line is detected, And a reception optical signal is provided to the CPU in the spare PON port so that the operator can easily recognize the state of the spare trunk line and stored in the circle queue and compared with the reception light sensitivity information of the operation trunk line. As shown in FIG. Many other modifications will be possible to those skilled in the art, within the scope of the basic technical idea of the present invention.

100: PON trunk redundancy system
110: optical line terminating device 112: CPU
114a, 114s: optical module 116a, 116s: PON MAC chip
120: optical communication terminal device 130: optical distributor

Claims

Obtaining reception light sensitivity information of the spare trunk line from the spare PON port;
Increasing reliability by accumulating the reception light sensitivity information of the spare trunk line by a predetermined amount or more;
Determining a maximum received light level among the received light sensitivity information of the spare trunk line;
Further enhancing the reliability by comparing the maximum received light level of the spare trunk line with a received light level of an operational PON port;
Determining a state of an abnormal preliminary trunk line when the maximum received light level of the spare trunk line is smaller than the received light level of the operational PON port; And
And providing an alarm message to the operator about the status of the abnormal preliminary trunk line. A method for detecting a preliminary trunk line receiving light level in a PON trunk duplication system,

The method according to claim 1,
Wherein the predetermined amount corresponds to a storage capacity for storing the reception light sensitivity information of the spare trunk line,
And if the predetermined amount exceeds the storage capacity,
Wherein the maximum received light level is retrieved in the order of the received light sensitivity information.

The optical line terminating apparatus and the plurality of optical telecommunication terminal apparatuses are duplexed into the operation trunk line and the spare trunk line, and when a fault occurs in the operation trunk line in use, the traffic is protected and switched from the trunk line to the spare trunk line In the PON trunk duplication system,
An operation PON port for obtaining a light sensitivity value received from the optical communication terminal device based on dynamic bandwidth allocation (DBA) of the PON MAC chip;
A spare PON port for acquiring a light sensitivity value received from the optical communication terminal device based on an idle time; And
The method includes the steps of: cumulatively storing a received light sensitivity value provided from the spare PON port in a circle queue; extracting a maximum received light level from the latest information of the cumulative information; And a CPU for judging the state of the line. A PON trunk duplication system for detecting a received light level of a preliminary trunk line.

The method of claim 3,
And determines that a failure has occurred in the standby trunk line when the maximum received light level is lower than the received light level of the operational PON port.

5. The method of claim 4,
Wherein the cumulative information size is 300 or more times. The PON trunk duplication system for detecting a received light level of a preliminary trunk line.

The CPU initializing the circle queue of the spare PON port;
Wherein the CPU receives a reception optical sensitivity value of a spare trunk line from a reception optical module of the spare PON port;
Storing the received light sensitivity value of the spare trunk line in the circle queue;
Extracting a maximum light level among the stored received light sensitivity values;
Comparing the maximum optical level with a received sensitivity value of an operating trunk line obtained by a receiving optical module of an operational PON port;
And providing an alarm to the operator when the maximum light level is less than the reception sensitivity value of the operation trunk line.

The method according to claim 6,
Wherein when the reception light sensitivity value of the preliminary trunk line is less than -28 dB in order to increase the reliability of the reception light sensitivity information stored in the circle queue, the preliminary trunk line reception light level detection method of the PON trunk line redundancy system.

Initializing the corresponding port and confirming whether or not the port is declared as a spare PON port;
Acquiring reception light sensitivity information of a spare PON port using an idle time;
Sequentially storing the measured received light sensitivity information in a circle queue;
Detecting a maximum received light level in the order of the currently stored received light sensitivity information;
Reporting to the operator if the maximum received light level is greater than an alarm threshold; And
When the maximum received light level is not greater than the alarm threshold, reporting to the operator if the stored received light sensitivity information is equal to the size of the circle queue. Line receiving light level detection method.

9. The method of claim 8,
Wherein when the maximum received light level is not greater than the alarm threshold and the stored received light sensitivity information does not meet the size of the circle queue, the notification is not reported to the operator. Detection method.

10. The method of claim 9,
Wherein the size of the circle queue is 300 times or more. A method of detecting a preliminary trunk line receiving light level in a PON trunk duplication system.