KR102119065B1 - Monitoring system based on optical signal and method of monitoring based on optical signal - Google Patents

Abstract

Disclosed is a monitoring system based on an optical signal. The monitoring system based on an optical signal includes a controller outputting an incident light signal and an optical module monitoring a place using the incident light signal. The optical module splits the incident light signal into two, and proceeds in opposite directions at both ends of the optical path installed at a place, and then combines the split two incident light signals to generate a received light signal. The controller receives the received optical signal, determines whether a phase difference occurs between the received optical signal and the incident optical signal, and determines whether an event has occurred in the place. The optical path is composed of an optical path having an integer multiple of the wavelength of the incident light signal.

Description

Monitoring system and monitoring method based on optical signal{MONITORING SYSTEM BASED ON OPTICAL SIGNAL AND METHOD OF MONITORING BASED ON OPTICAL SIGNAL}

Embodiments of the present disclosure relate to an optical signal based monitoring system and a monitoring method.

The monitoring system using the light reflection measurement method uses a principle that when an external force is applied to a light path made of an optical fiber, a refractive index change occurs in a corresponding optical fiber or reflected light is generated and the intensity of the light is changed. However, such a monitoring system may have low accuracy because it determines whether an event has occurred based only on the light intensity.

For example, in the case of an optical time domain reflectometer (OTDR) system most widely used as an external force sensing system using an optical fiber as shown in FIG. 13, after generating a pulse signal, the reflected light or the pulse wave is detected by the light receiving unit at the other end and the waveform change is detected. It is operated as a method of determining the size or location of an external force by measuring time. In the case of such an OTDR, since sensitivity is remarkably low, an external force response is detected in a situation where the optical fiber is bent at an angle of about 90 degrees or so. There are disadvantages that are needed. In addition, since it is difficult to detect a reaction when a portion other than a twisted ring is touched, there is a problem in that a cable must be installed over the entire interface such as a barbed wire. On the other hand, in order to improve the problem of the sensitivity, a FBG (fiber bragg grating) cable capable of increasing the sensitivity by forming a certain pattern in the optical fiber may be used, but a large place may be used due to expensive installation cost, signal loss during long distance transmission, and the like. There is a problem that is not suitable for the monitoring equipment to be covered.

In particular, in the case of monitoring and monitoring systems in large-scale facilities such as airports, power plants, factories, and warehouses, there is a need for a monitoring sensor facility that reduces installation costs, facilitates efficient construction and mass installation, and shortens construction period.

The problem to be solved by the present disclosure is to apply a different wavelength from a plurality of optical modules installed in a plurality of places, and a plurality of places to diverge light of a selected wavelength, and proceed to the optical path in opposite directions to each other, and then combine the signals. It is to provide an optical signal-based monitoring system and a monitoring method capable of monitoring in which place an external force is applied when measuring the external force.

An optical signal based monitoring system according to embodiments of the present disclosure includes a controller that outputs an incident light signal and an optical module for monitoring a place using the incident light signal, and the optical module divides the incident light signal into two. After advancing in opposite directions at both ends of the optical path installed in the place, the combined optical signals are generated, and the controller receives the received optical signals, and a phase difference occurs between the received optical signals and the incident optical signals. It is determined whether or not an event has occurred in the place, and the optical path comprises an optical path having an integer multiple of the wavelength of the incident light signal.

A monitoring method of an optical signal-based monitoring system including an optical module and a controller for controlling the optical module according to embodiments of the present disclosure includes: outputting an incident light signal by the controller, and the optical module placing the incident light signal Bifurcating into dogs, and proceeding in opposite directions at both ends of the optical path installed at the place, and then combining to generate a received optical signal, the optical module transmitting the received optical signal to the controller, and the controller is the And receiving a received optical signal, determining whether a phase difference occurs between the received optical signal and the incident optical signal, and determining whether an event has occurred in the place, and the optical path is an integer multiple of the wavelength of the incident optical signal. It consists of an optical path having a length of.

A computer-readable medium according to embodiments of the present disclosure may store a program that performs an optical signal-based monitoring method when executed in a computer.

According to the present disclosure, when the external force is generated by separating and transmitting the light of the same wavelength in the opposite direction, when the dual signal is interfered with by the receiving unit, the amount of change in the optical signal is maximized and the sensitivity to external force is maximized. It grows.

That is, by measuring the amount of change in the optical signal at the light receiving unit, it is not necessary to form a cable in the form of a ring like an OTDR, and a simple and highly sensitive optical fiber monitoring sensor that does not need to use an expensive FBG can be implemented.

In addition, according to an embodiment of the present disclosure, by dividing the entire monitoring section into a plurality of sections and applying a plurality of pulse signals having a plurality of wavelengths equal to or greater than the number of the sections, only a pulse signal of a specific wavelength can be measured in a specific section. By specifying the compartment to which the external force is applied, it is possible to determine in which compartment the external force is operating.

According to embodiments of the present disclosure, since a plurality of optical modules may be installed to be extended with respect to an existing module, if only an optical module is additionally installed in order to expand a range to be monitored, installation is simple.

According to embodiments of the present disclosure, since a plurality of received optical signals output from a plurality of optical modules are combined into one combined received optical signal and transmitted to a controller, detection accuracy and stability are high even if the number of optical modules increases. .

In addition, according to the present disclosure, by learning the model of the measured waveform through deep learning, it is possible to specify the type of external force applied through the pattern analysis of the vibration waveform.

1 shows an optical signal-based monitoring system according to embodiments of the present disclosure.
2 shows a controller according to embodiments of the present disclosure.
3 shows an optical module according to embodiments of the present disclosure.
4 and 5 show the flow of the system and the optical signal when there are three monitoring locations in the embodiment of FIG. 3.
6 shows an optical module according to embodiments of the present disclosure.
FIG. 7 shows a case where an event occurs in the optical module of FIG. 5.
8 shows an optical signal according to embodiments of the present disclosure.
9 and 10 show waveforms of events and received light signals according to embodiments of the present disclosure.
11 is a flowchart illustrating an optical signal-based monitoring method according to embodiments of the present disclosure.
12 is a flowchart illustrating an optical signal based monitoring method according to embodiments of the present disclosure.
13 illustrates a block diagram showing an OTDR system according to the prior art and changes and loss of measurement signals.

Embodiments of the present disclosure will be described with reference to the accompanying drawings in this specification.

1 shows an optical signal-based monitoring system according to embodiments of the present disclosure. Referring to FIG. 1, the monitoring system 10 may include a controller 100 and a plurality of optical modules 200-1 to 200-n (where n is a natural number of 2 or more). The monitoring system 10 may detect an event (or external force generation) occurring in a plurality of places (ZONE1 to ZONEn) using an optical fiber and an optical signal through the optical fiber. According to embodiments, the monitoring system 10 may detect the location and characteristics (type, strength, etc.) of events occurring in a plurality of places.

The controller 100 outputs a combined incident light signal IOS_CB in which light of a plurality of wavelengths or frequencies is combined. Here, the number of wavelengths or frequencies included in the combined incident light signal IOS_CB may be the same as the number of locations (ZONE1 to ZONEn) to be monitored, but is not limited thereto.

In each place (ZONE1~ZONEn), only the light having one selected frequency/wavelength is used to monitor the external force and vibration of the corresponding place, and then a received optical signal is formed, and the received optical signal received at the corresponding location is combined. To form a combined received optical signal and send it to the controller 100.

The controller 100 can sense the input of external force or vibration through the waveform change of the optical signal from the combined received optical signal ROS_CB, select (or determine) the light with the waveform change, and the frequency of the light with the waveform change By analyzing, it is possible to specify a place where the light where the waveform change has occurred is a place where an external force has occurred.

According to embodiments, the detector 150 of the controller 100 includes a light sensing unit capable of analyzing a diffraction pattern (or interference pattern) of the combined received optical signal ROS_CB, or according to the combined received optical signal ROS_CB. It may be an optical voltage sensing unit made of a photodiode capable of detecting a change in voltage due to the generated photoelectric effect. Hereinafter, in this specification, it is assumed for convenience that the light receiving unit of the controller 100 includes a voltage sensing unit capable of measuring an optical voltage generated by a photoelectric effect due to a waveform change due to a phase difference of a dual optical signal when an external force occurs. do. According to embodiments of the present disclosure, the voltage sensing unit may include a photodiode. The photodiode included in the voltage sensing unit corresponds to a photodetector that generates a different voltage according to the light intensity by a photoelectric effect. When external force occurs in the optical path (path of the corresponding place among OP1 to OPn) in a specific place (one of ZONE1 to ZONEn), the phase difference of the input dual optical signals proceeding in the opposite direction to the optical path occurs, and the initial input light A voltage waveform different from the signal and a different waveform change occur. By measuring this, you can check the change in the waveform. According to embodiments of the present disclosure, the detector 150 includes a photodiode. When the combined received optical signal ROS_CB is applied to the detector 150, a voltage is generated by the photoelectric effect, and a change in the optical voltage with respect to this time axis can be detected. Since the waveform of the voltage change is sensitively reacted by the phase difference of the dual optical signal, it can be accurately measured even if the size of the event is small.

In addition, when the waveform change of the combined received optical signal ROS_CB occurs, the controller 100 analyzes the wavelength/frequency of the received optical signal having a waveform change among the received optical signals included in the combined received optical signal ROS_CB and performs a plurality It is possible to determine at which of the places (ZONE1 to ZONEn) the event occurred.

Referring to the drawings in detail, as shown in FIGS. 1 to 2, the plurality of optical modules 200-1 to 200-n detect events occurring in a plurality of places (ZONE1 to ZONEn). Can be used. According to embodiments, the plurality of optical modules 200-1 to 200-n may include a plurality of places (ZONE1~) through a plurality of incident light signals IOS1 to IOSn through optical loops OP1 to OPn. ZONEn).

As shown in FIG. 2, the controller 100 generates a combined incident light signal IOS_CB combined with light of a plurality of wavelengths and transmits it to the optical module side. For example, the place consists of three (n=3), and the combined incident light signal (IOS_CB) may be a combined optical signal of three optical signals having different wavelengths of 1310 nm, 1530 nm, and 1550 nm, and optical signals of different wavelengths Since it proceeds independently in the optical fiber, even if the optical signals are separated from each other through a frequency filter and combined through a combiner, the waveform properties of each optical signal can be transmitted independently to the optical module while being maintained independently.

The primary incident light signal IOS1 is an optical signal of a frequency to be processed by the first optical module 200-1. The primary incident light signal IOS1 is selected by the frequency filter of the first optical module 200-1. The unfiltered combined incident light signal may be bypassed and transmitted to the second optical module 200-2.

Similarly, in the second optical module 200-2, the secondary incident light signal IOS2 is selected through a frequency filter, and the combined incident light signal IOS_CB is bypassed and transmitted to the third optical module 200-3. That is, the combined incident light signal IOS_CB is transmitted while maintaining its characteristics until the nth optical module 200-n, and in each optical module 200-1 to 200-n, it is included in the combined incident light signal IOS_CB. Among the optical signals, an optical signal to be used in a corresponding place (ZONE1 to ZONEn) is extracted using a frequency filter 260-1 to 260n, and the extracted optical signal is transmitted to the corresponding place.

The first optical module 200-1 branches the extracted first incident optical signal (IOS) into two optical signals through the distributor 210-1, and splits the two first incident optical signals (IOS1). Is output to the first place (ZONE1) through the first optical path (OP1), the branched primary incident light signal proceeds to the first place (ZONE1) in the opposite direction to each other through the first optical path (OP1), and then combines (240) It is combined in -1) and is received as the primary received optical signal ROS1.

Each of the optical paths OP1 to OPn is an optical path in which loops are formed so that the incident light signals diverge and proceed in opposite directions and pass through a plurality of places (ZONE1 to ZONEn).

As will be described in detail later with reference to FIGS. 5 and 6, when an event occurs in the first place (ZONE1), the first incident optical signal passing through the first optical path (OP1) is divided into two optical signals (ie, dual) Phase difference occurs in the optical signal) and the first received optical signal coupled to the combiner is received as an optical signal having a waveform different from the first incident optical signal by the phase difference of the dual optical signal. For example, at least one of the amplitude and wavelength of the primary received optical signal may be different from at least one of the amplitude and wavelength of the incident first incident optical signal, and such a change may include a diffraction pattern (or interference pattern) or a light receiving unit of the primary received light signal. It can be confirmed by the change of the voltage waveform of ..

3 shows an optical module according to embodiments of the present disclosure. The optical module 200-1 shown in FIG. 3 is a representative representation of the first optical module 200-1 among the optical modules 200-1 to 200-n shown in FIG. That is, the structure and function of the optical modules 200-1 to 200-n of the present disclosure may be described as the structure and function of the first optical module 200-1 shown in FIG. 3.

3, the first optical module 200-1 includes a distributor 210-1, a primary coupler 220-1, a secondary coupler 230-1 and a coupler 240-1, an optical fiber ( 250-1), an optical filter 260-1 and a received optical signal combiner 270-1.

The optical filter 260-1 extracts the primary incident light signal IOS1 to be used in the first optical module 200-1 from the combined incident light signal IOS_CB having a plurality of wavelengths, and extracts the combined incident light signal from the second optical module Bypass to (200-2). For example, the optical filter 260-1 may extract the primary incident light signal IOS1 corresponding to the wavelength allocated to the first location ZONE1 from the combined incident light signal IOS_CB.

In addition, like the first optical module 200-1, each optical module 200-1 to 200-n includes an optical filter 260, and can extract incident light signals to be used in the optical module.

For example, the first optical module 200-1 extracts an optical signal having a wavelength of 1310 nm from the combined incident light signal IOS_CB as the primary incident light signal IOS1 using the optical filter 260-1, and extracts the extracted primary incident light signal (IOS1) can be sent to the first location (ZONE1) through the first optical path (OP1). The second optical module 200-2 extracts an optical signal having a wavelength of 1530 nm from the combined incident light signal IOS_CB as a secondary incident light signal IOS2 using an optical filter, and extracts the extracted second incident light signal IOPS2 as a second optical path. You can send it to the second location (ZONE2) through (OP2). The third optical module 200-3 extracts an optical signal having a wavelength of 1550 nm from the combined incident light signal IOS_CB as a third incident light signal IOS3 by using a filter, and extracts the extracted third incident light signal IOS3 third It can be sent to a location (ZONE3).

Accordingly, the plurality of optical modules 200-1 to 200-n receive the combined incident light signal IOS_CB, and the incident incident light signals IOS1 to IOSn of the wavelength corresponding to themselves from the received combined incident light signal IOS_CB And the combined incident light signal (IOS_CB) is bypassed and transmitted to the next optical module.

The divider 210-1 branches the incident light signal IOS1 into two light signals. In the drawing, the distributor 210-1 branches the incident light signal IOS1 extracted from the optical filter 260-1 into a primary incident light signal IOS1_P and a second incident light signal IOS1_S. The primary incident light signal IOS1_P and the secondary incident light signal IOS1_S have the same optical characteristics.

The optical fiber 250-1 is formed of a loop exposed to the place ZONE1, and both ends are respectively connected to the primary coupler 220-1 and the secondary coupler 230-1. The above-described primary incident light signal IOS1_P is incident on the primary coupler 220-1, proceeds to the secondary coupler 230-1 within the optical fiber 250 (clockwise in the drawing), and then moves the secondary coupler 230-1. Through the first received optical signal (ROS1_P) proceeds to the combiner 240, the secondary incident light signal (IOS1_S) is incident on the secondary coupler (230-1) and proceeds to the primary coupler (220-1) in the primary coupler optical fiber ( In the drawing, a counterclockwise direction is performed through the primary coupler 220-1 to the combiner 240-1 as the secondary received optical signal ROS1_S.

The combiner 240-1 combines the primary received optical signal ROS1_P and the secondary received optical signal ROS1_S to form a single optical module received optical signal ROS1, and receives the received optical signal ROS1 as a received optical signal combiner (270-1).

4 and 5, when the monitoring place is a continuous fence and the place to be monitored is three sections (ZONE1, ZONE2, ZONE3), the combined incident light signal is a combined light beam including optical signals having wavelengths of 1310nm, 1530nm and 1550nm. It shows an example of the case. As shown in FIG. 4, the signal generator of the controller 100 transmits control signals to three laser diodes, and the three laser diodes have three wavelengths of 1310 nm, 1530 nm, and 1550 nm in response to the input control signal. Generates laser light. The controller 100 may combine three laser lights and transmit the combined light to the optical module. In addition, the controller 100 receives the combined received optical signal past the optical path and separates them into different wavelengths through a divider. The detector includes a photodiode as a light-receiving unit, detects light of a corresponding wavelength, detects a waveform of each wavelength-received light signal, amplifies and stores it in memory as digital information through a converter.

As shown in FIG. 5, the first optical module 200-1 filters the first incident optical signal IOS1 having a wavelength of 1310 nm from the combined incident optical signal IOS_CB transmitted from the controller 100 (corresponding to the front end) and , The first incident optical signal IOS1 is transmitted to the first location ZONE1 and the original combined incident optical signal IOS_CB is bypassed and transmitted to the second optical module 200-2 (corresponding to the rear end).

Likewise, the second optical module 200-2 filters the secondary incident light signal IOS2 having a wavelength of 1530 nm from the combined incident light signal IOS_CB transmitted from the first optical module 200-1, and filters the secondary incident light signal IOS2. It transmits to the second place (ZONE2) and bypasses the original combined incident light signal (IOS_CB) and transmits it to the third optical module. The third optical module at the last stage filters the third incident light signal having a wavelength of 1550 nm from the combined incident light signal IOS_CB, and transmits the third incident light signal to the third place. As illustrated, in the optical module at the last stage, such as the third optical module 200-3, the incident light can be used without needing to be distributed, and since there is no subsequent stage thereafter, the number of the third optical module 200-3 The new optical signal is output from the third optical module 200-3 without the need for combining.

The plurality of optical modules generates a plurality of received optical signals ROS1 to ROSn through the above-described process using incident light signals of different frequencies, and the received optical signal combiners of each optical module may be transmitted from the optical module of the rear stage. Receive a new optical signal (e.g., ROS_2+ROS_3+...ROSn in the case of the first optical module) and additionally combine the received optical signal of the corresponding optical module (e.g., ROS1 in the case of the first optical module) to receive the combined received optical signal Transfer to the front end optical module. Through this sequential process, the first optical module finally generates and transmits a combined received optical signal ROS_CB combined with received optical signals of the entire optical module to the controller.

According to embodiments of the present disclosure, an event occurring in a plurality of places may be detected using a combined incident light having a plurality of wavelengths using a plurality of optical modules instead of a single optical module. Furthermore, despite the use of a plurality of optical modules, installation and implementation is simple because one combined incident light signal and one combined received light signal are used, and no additional power is required to be applied to each module.

The controller 100 may detect events occurring in a plurality of places (ZONE1 to ZONEn) by using the change indicated in the combined received light signal (ROS_CB). When a waveform change occurs in the combined received optical signal ROS_CB, the controller 100 determines an optical signal having a waveform change among the optical signals included in the combined received optical signal ROS_CB based on the frequency band where the waveform change has occurred. Then, using a corresponding optical signal, it is possible to detect a place where an event has occurred among a plurality of places (ZONE1 to ZONEn).

As shown in FIG. 5, when an event occurs in the second location (ZONE2), a change occurs in the waveform of the 1530nm optical signal traveling through the corresponding place. Therefore, since the waveform of the 1530nm wavelength optical signal changes in the combined received optical signal transmitted from the first optical module 200-1 to the controller 100, the waveform of the 1530nm wavelength can be detected through the detector to detect the waveform change. have.

That is, when a waveform change occurs in the nth received optical signal ROSn among the combined received optical signals ROS_CB, it may be detected that an event has occurred in the nth location ZONEn. 4 and 5, the controller 100 measures the frequency at which the waveform change occurred in the combined received optical signal ROS_CB, and when the frequency at which the waveform change occurs is 1310 nm, the controller 100 transmits the optical signal at a frequency of 1310 nm. It can be determined that the event has occurred in the corresponding first place (ZONE1), and when the frequency where the waveform change occurs is 1530nm, it can be determined that the event has occurred in the second place (ZONE2) corresponding to the optical signal of the frequency of 1530nm. , When the frequency at which the waveform change occurred is 1550 nm, it may be determined that the event has occurred at the third location (ZONE3) corresponding to the optical signal having the frequency of 1550 nm.

The controller 100 learns the pattern of each waveform change according to the location and type of the events of the received optical signals ROS1 to ROSn included in the combined received optical signal ROS_CB, and receives the received optical signal based on the learning result. It is also possible to determine what kind of event occurred from the waveform change of the fields ROS1 to ROSn. The learning method described above can be programmed by applying various artificial intelligence algorithms such as deep learning through image analysis or graph analysis, learning through discrimination data and probability through machine learning.

When the event location is determined, if a CCTV is installed at the location where the event occurs, a second confirmation of the event or a patrol by the administrator for the corresponding location may be performed.

The primary coupler 220-1 and the secondary coupler 230-1 selectively pass only optical signals in a specific direction. For example, the couplers 220-1 and 230-1 pass the optical signal incident in the first direction, and reflect the optical signal incident in the second direction opposite to the first direction. Referring to the drawings, the primary coupler 220-1 and the secondary coupler 230-2 pass through an optical signal incident at their front end (on the left side in the drawing), but at their rear end (on the right side in the drawing). The reflected optical signal is reflected.

The wavelength of the optical signal reflected or passed by the primary coupler 220-1 and the secondary coupler 230-1 does not change. The combiner 240-1 receives and combines the signal reflected from the primary coupler 220-1 and the signal reflected from the secondary coupler 230-1. The combiner 240-1 combines the primary received optical signal ROS1_P and the primary received optical signal ROS1_S to generate and output the received optical signal ROS1. The received optical signals ROS1 to ROSn of each optical module are added in reverse order from the received optical signal combiner 270 of each optical module to finally form a combined received optical signal ROS_CB in the first optical module to the controller 100 To join.

The optical path difference between the primary received optical signal ROS1_P and the secondary received optical signal ROS1_S may be an integer multiple of the original wavelength. That is, the optical path of the primary received optical signal ROS1_P is called OP_RP, the optical path of the secondary received optical signal ROS1_S is called OP_RS, and the wavelengths of the primary received optical signal ROS1_P and the secondary received optical signal ROS_S are λ. If you do, the following equation

OP_RP-OP_RS = k*λ (k is an integer)

Is satisfied.

6 and 7, when analyzing the received optical signal ROS1 output from the combiner 240-1, it may be confirmed whether an event has occurred on the optical fiber 250-1. According to embodiments, the pattern appearing on the received optical signal ROS1 is observed, the observed pattern is compared with the reference pattern (stored in advance), and an event occurs on the optical fiber 250-1 based on the comparison result. Whether or not it can be detected, and the characteristics of the event can be checked. In addition, by measuring a change in voltage due to the received optical signal ROS1, it is possible to detect whether an event has occurred on the optical fiber 250-1, and to check the characteristics of the event.

6 shows an optical module when an event does not occur. The optical module 200-1 shown in FIG. 5 exemplarily shows the first optical module 200-1 of FIG. When an event does not occur for the optical fiber 250-1, the primary incident light signal IOS1_P is not refracted/reflected in the optical fiber 250-1, but proceeds to the secondary coupler 230-1, and the secondary incident light signal ( IOS1_S) may also proceed to the primary coupler 220-1 without being refracted/reflected within the optical fiber 250-1.

When the primary received optical signal ROS1_P and the secondary received optical signal ROS1_S are combined by the combiner 240-1, the phase difference hardly occurs and the amplitude is extremely small, and the frequency/wavelength does not change. IOS1), and it is determined that no external force is generated in a place where the input optical signal IOS1 and the received optical signal ROS1 are almost the same.

That is, the primary incident light signal IOS1_P diverges from the distributor 210-1, passes through the primary coupler 220-1, proceeds clockwise along the optical fiber 250-1, and proceeds to the secondary coupler 230-1. do. The primary incident light signal IOS1_P is reflected from the secondary coupler 230-1 and proceeds to the coupler 240. Further, the secondary incident light signal IOS1_S is branched from the distributor 210-1, passes through the secondary coupler 230-1, and proceeds counterclockwise along the optical fiber 250-1 to the primary coupler 220-1. To join. The secondary incident light signal IOS1_S is reflected by the primary coupler 220-1 and proceeds to the coupler 240-1. The primary incident light signal IOS1_P and the secondary incident light signal IOS1_S do not interfere with each other within the optical fiber 250-1, and proceed as independent signals.

When an event does not occur on the optical path OP as shown in FIG. 6, the optical path difference between the primary received optical signal ROS1_P and the secondary received optical signal ROS1_S is the primary received optical signal ROS1_P and the secondary received optical signal ( ROS1_S) Since it is an integer multiple of the wavelength, when the primary received optical signal ROS1_P and the secondary received optical signal ROS1_S are combined in the combiner 240-1, mutual phase difference does not occur and can be combined into one received optical signal. The phase difference does not occur even in preparation for the incident light signal IOS1. Accordingly, the received optical signal ROS1 does not have a phase difference with respect to the incident optical signal IOS1. That is, the received optical signal ROS1 and the incident light signal IOS1 have a phase difference of an integer multiple of 2π (where π is the circumference), so the pattern of the received optical signal ROS1 (for example, a diffraction pattern of Laue) and the incident light signal IOS1 The patterns of the same represent the same pattern with each other. That is, if the diffraction pattern of the incident light signal IOS1 is referred to as a reference pattern, the received light signal ROS1 when an event does not occur on the optical path OP represents a reference pattern.

7 shows the optical module 200 when an event occurs with respect to the optical fiber 250-1. When an event occurs with respect to the optical fiber 250-1, the primary incident light signal IOS1_P proceeds in the optical fiber 250-1 through the primary coupler 220-1, but is refracted/reflected at the location where the event occurs, and thus the primary coupler (220-1) is again incident, or proceeds to the secondary coupler 230-1 with a phase difference occurring. Likewise, the secondary incident optical signal IOS1_S proceeds in the optical fiber 250-1 through the secondary coupler 220-1 and is refracted/reflected at the position where the event occurs, or reflected back to the secondary coupler 230-1, or the phase difference And proceeds to the primary coupler 220-1. Refraction and reflection may occur only one or at the same time.

The primary coupler 220-1 passes the primary incident light signal IOS1_P incident in the first direction (the direction from the left to the right in the drawing), but is reflected at the location where the event occurred and is reflected in the second direction (from the right to the left in the drawing) The primary incident light signal (IOS1_P) incident in the direction of the direction and the secondary incident light signal (IOS1_S) that refracts and proceeds counterclockwise with a phase difference is reflected. Similarly, the secondary coupler 230-1 also passes the secondary incident light signal IOS1_S incident in the first direction, but is reflected at the position where the event occurred and is incident to the second incident light signal IOS1_S reflected in the second direction and refracted to compensate for the phase difference. The primary incident light signal IOS1_P traveling in the clockwise direction of the exciter is reflected.

The primary received optical signal ROS1_P and the secondary received optical signal ROS1_S, which are signals reflected from the couplers 220-1 and 230-1, may be output to and coupled to the combiner 240-1. Since the primary received optical signal and the secondary received optical signal correspond to the same wavelength, they may be combined into one received optical signal ROS1.

When an event occurs at an arbitrary position on the optical path OP-1 as shown in FIG. 7, the optical path between the primary received optical signal ROS1_P and the secondary received optical signal ROS1_S on the optical fiber 250-1 is caused by the event. A difference occurs and has a phase difference. Depending on the phase difference, the received light signal ROS1 and the incident light signal IOS1 may exhibit different characteristics.

According to embodiments, the pattern of the received optical signal ROS1 represents a pattern different from the pattern of the incident optical signal IOS1. That is, when the diffraction pattern of the incident light signal IOS1 represents the reference pattern, the diffraction pattern of the received light signal ROS1 when an event occurs on the optical path OP-1 may be different from the reference pattern.

In addition, when measuring with a photodiode, the voltage change due to the received light signal ROS1 may be different from the voltage change caused by the incident light signal IOS1. For example, when measuring through a photodiode, the waveform of the voltage change amount of the received light signal ROS1 may be measured differently from the waveform of the voltage change amount of the incident light signal IOS1 (see FIGS. 9 and 10 ).

Therefore, by analyzing the diffraction pattern pattern of the incident light signal (IOS1) and the received light signal (ROS1), or by measuring the voltage change waveform at the light-receiving unit, it is possible to monitor the occurrence of the event, size, persistence, etc. By analyzing, it is possible to identify the place where the event occurred (the location where the event occurred) by specifying the optical module where the event occurred.

Referring to FIG. 8, when an event occurs for the optical fiber 250-1, a change occurs in the optical path of the primary received optical signal ROS1_P or the secondary received optical signal ROS1_S. According to embodiments, when an event occurs for the optical fiber 250-1, the optical path of the primary received optical signal ROS1_P or the secondary received optical signal ROS1_S is shortened. Accordingly, the phase of the received optical signal ROS1 may be changed, and the intensity of the received optical signal ROS1 may be changed. For example, as shown in FIG. 8, when an event occurs for the optical fiber 250-1, the period of the received optical signal ROS1 may be shortened (tNE>tE) and the intensity may be reduced (ANE>AE). .

In addition, a change in the optical path of the primary received optical signal ROS1_P or the secondary received optical signal ROS1_S may vary according to the location of the event. Accordingly, a change in the period and intensity of the received optical signal ROS1 may vary according to the location of the event.

9 and 10, when the detector 150 of the controller 100 is implemented as a light-receiving unit including a photodiode, the voltage change measured by the detector 150 is visualized as a waveform. FIG. 9 shows the voltage waveform measured by the detector 150 in a situation where the intruder mounted the ladder to jump over the fence, which is the monitoring target location, and FIG. 10 shows the shear force to cut the fence, which is the monitoring target location. It shows the situation in which the

The pattern of the received optical signal ROS can be based on the nature of the event on the optical fiber 250, and the wavelength is based on the location (location) of the event.

The controller 100 may detect the location and characteristics of the event by comparing the diffraction pattern pattern or voltage waveform change pattern of the received light signal ROS with the pattern indicated by the pattern of the received light signal ROS and the stored reference patterns. Here, the pre-stored reference patterns may be data obtained by patterning the pattern of the received optical signal ROS while varying the characteristics of the event. For example, the controller 100 identifies the pattern most similar to the pattern indicated by the pattern of the received optical signal ROS among the stored reference patterns, and uses the characteristics of the event corresponding to the most similar pattern to actually perform the optical fiber 250. You can detect the nature of the event that has occurred.

As such, depending on the type of event, the shape of the diffraction pattern of the received optical signal ROS may be different or the waveform of the voltage change of the received optical signal may be different. Analysis of the light voltage waveform change pattern of the light-receiving unit by the waveform can determine the type of occurrence of the event.

On the other hand, in the embodiments of the present disclosure, since the received optical signals generated by the plurality of optical modules have independent wavelengths, the wavelength of the received optical signal where the event has occurred can be measured to determine which optical module has the event. , It is possible to determine the location of the event, that is, the location of the event in a range.

Referring back to FIG. 2, the controller 100 includes a processor 110, an optical signal generator 120, a combiner 130, a distributor 140, a detector 150, and a memory 160.

The processor 110 may control the overall operation of the controller 100. According to embodiments, the processor 110 performs an operation to control the operation of the optical signal generator 120, the combiner 130, the divider 140, the detector 150, and the memory 160, or executes instructions. It can be generated and printed. For example, the processor 110 may be implemented as a central processing unit (CPU) having a processing function, a micro controller unit (MCU), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). It is not limited to this.

The processor 110 may further include a signal generator 111 that generates a control signal for controlling the optical signal generator 120.

The processor 110 may detect the characteristics of the event by comparing the pattern represented by the pattern of the received optical signals ROS1 to ROSn with the stored reference patterns. According to embodiments, the processor 110 determines the pattern of the received optical signals ROS1 to ROSn, and identifies the received optical signal having a different pattern from the reference pattern among the received optical signals ROS1 to ROSn. You can determine the characteristics of.

The processor 110 stores the wavelength bands allocated to each of the optical modules 200-1 to 200-n, and measures the wavelength bands of the received optical signals having different patterns from the reference pattern among the received optical signals ROS1 to ROSn. Thus, it is possible to identify the optical module where the event occurred, and thereby identify the place where the event occurred. In the case of the above-described example, when the pattern of the received optical signal in the wavelength band of 1530 nm does not represent a reference pattern, the processor 110 determines that the received optical signal ROS2 is transmitted from the second optical module 200-2. It may be determined that the event has occurred in the second place (ZONE2) where the second optical module 200-2 is installed.

The optical signal generator 120 may output an optical signal under the control of the processor 110. According to embodiments, the optical signal generator 120 may output a plurality of optical signals OS1 to OSn based on the control signal output from the signal generator 111. These are a plurality of optical signals (OS1 to OSn) having a plurality of wavelengths, and correspond to optical signals having a wavelength that can be filtered by a plurality of optical modules, respectively.

In this embodiment, the optical signal generator 120 may include a plurality of laser diodes LD1 to LDn, and each of the plurality of laser diodes LD1 to LDn may include a plurality of optical signals OS1 to OSn. Output each. The wavelengths of the plurality of optical signals OS1 to OSn are different. That is, the plurality of laser diodes LD1 to LDn output optical signals of different wavelength bands.

The combiner 130 receives a plurality of optical signals OS1 to OSn, combines the plurality of optical signals OS1 to OSn, and outputs a combined incident light signal IOS_CB. In this embodiment, the combiner 130 generates a combined incident light signal IOS_CB using a plurality of optical signals OS1 to OSn, and generates a combined incident light signal IOS_CB of the plurality of optical modules 200-1. ~200-n).

The combined incident light signal IOS_CB is an optical signal including information on the plurality of optical signals OS1 to OSn, and includes all wavelength components of each of the plurality of optical signals OS1 to OSn.

The divider 140 receives the combined received optical signal ROS_CB from which the combined received optical signals from each optical module 200-1 to 200-n are combined, and distributes the combined received optical signal ROS_CB for each wavelength. The plurality of received light signals ROS1 to ROSn are generated, and the generated plurality of received light signals ROS1 to ROSn are output to the detector.

That is, the combined received optical signal ROS_CB is an optical signal including information on a plurality of received optical signals ROS1 to ROSn, and the detector 150 has a plurality of received optical signals ROS1 to ROSn according to a wavelength. And detects the fringes of the plurality of received optical signals ROS1 to ROSn.

The detector 150 individually detects each of the plurality of received light signals ROS1 to ROSn according to a wavelength, and can detect a waveform change and a received signal pattern of each of the number of received light signals ROS1 to ROSn. .

In this embodiment, the detector 150 includes a light-receiving unit made of a photodiode for detecting a plurality of received optical signals ROS1 to ROSn, an amplifier for amplifying the detection result, and amplified detection And a converter that digitally converts the results and stores them in the memory 160. That is, the measurement results of the plurality of received optical signals ROS1 to ROSn by the detector 150 are digitally converted and stored in the memory 160. The memory 160 may store data necessary for the operation of the controller 100. In this embodiment, the memory 160 includes data necessary to generate the plurality of optical signals OS1 to OSn, detection data of the plurality of received optical signals ROS1 to ROSn, and the location of the event and the received optical signals ( ROS1~ROSn) Reference patterns for each waveform can be stored.

As described above, in the first optical module, the incident light signal IOS1 is divided into the first incident light signal IOS1_P and the second incident light signal IOS1_S, and thus optical fibers through the optical couplers 220-1 and 230-1 Proceeding to (250-1), the first and secondary received optical signals (ROS1_P, ROS1_S) output from the optical couplers 220-1 and 230-1 are incident on the combiner 240-1, and the first optical module Is output as the received optical signal ROS1.

The combiner 270-1 of the first optical module receives the received optical signal ROS1 and combines the received optical signals ROS2 to ROSn of the second to nth optical modules with the first received optical signal ROS1. A combined received optical signal (ROS_CB) is generated.

In this embodiment, the received optical signals ROS2 to ROSn of the second to nth optical modules may be transmitted from the second optical module 200-2, and the received optical signals ROS2 of the second to nth optical modules may be transmitted. ~ROSn) is transmitted as a combined optical signal.

That is, the optical signal (∑_) in which the received optical signals of all the optical modules (200-m+1 to 200-n) disposed at the rear end are combined in the combiner of the m-th (m is a natural number between 1 and n) optical modules. (i=m+1)^n▒ROSi) is transmitted from the next stage coupler, and combined with the received optical signal of the optical module containing the coupler, the combined received optical signal is transmitted to the previous coupler.

The combiner 270-1 of the first optical module 200-1 transmits the generated combined receive optical signal ROS_CB to the controller 100.

11 is a flowchart illustrating an optical signal-based monitoring method according to embodiments of the present disclosure. The monitoring method to be described with reference to FIG. 11 may correspond to the function of the monitoring system 10 described with reference to FIGS. 1 to 10. Further, the monitoring method may be performed by the controller 100 or the processor 110, and may also be implemented with instructions executable by the processor 110. The instructions may be stored in the form of a program on a computer-readable storage medium.

1 to 11, the controller 100 may generate a plurality of optical signals OS1 to OSn (S110). According to embodiments, the plurality of optical signals OS1 to OSn and the plurality of incident optical signals IOS1 to IOSn having different wavelengths used in the plurality of optical modules 200-1 to 200-n It can be the same.

The controller 100 outputs the combined incident light signal IOS_CB using a plurality of optical signals OS1 to OSn (S120). The controller 100 combines a plurality of optical signals OS1 to OSn to generate a combined incident light signal IOS_CB, and outputs the generated combined incident light signal IOS_CB.

Next, the combined incident light signal (IOS_CB) in each optical module 200 is filtered into incident light signals (IOS1 to IOSn) having one wavelength selected in the corresponding optical module, and then branched into two to make up a scene composed of loops arranged in the monitoring zone. It proceeds in the opposite direction to each other in the furnace (250: OP) to obtain a received optical signal (S130). The change in the optical signal waveform due to the phase difference of the optical signals passing through the two branched loop optical paths in opposite directions is very sensitive, and the event is detected with a sensitivity of less than 1/1000 of the external force that can be measured by the existing optical fiber sensor OTDR. Is possible.

Thereafter, all of the received optical signals of each optical module are combined to generate a combined received optical signal (ROS_CB) (S140).

The controller 100 receives the combined received light signal ROS_CB (S150). At this time, the controller 100 receives the combined received optical signal ROS_CB from the first optical module 200-1. The combined received optical signal ROS_CB is an optical signal in which a plurality of received optical signals ROS1 to ROSn are combined. Since the plurality of received light signals have different wavelengths, characteristics of each wavelength are maintained independently even if the light is single. Thereafter, the controller 100 generates (or separates) a plurality of received optical signals ROS1 to ROSn using the combined received optical signal ROS_CB (S160). The controller 100 distributes the combined received optical signal ROS_CB for each wavelength band to generate a plurality of received optical signals ROS1 to ROSn.

Finally, the controller 100 may monitor a plurality of places (ZONE1 to ZONEn) using a plurality of received light signals (ROS1 to ROSn) (S170). According to embodiments, the controller 100 detects a plurality of received light signals ROS1 to ROSn, and based on the diffraction pattern of the plurality of received light signals ROS1 to ROSn, the plurality of optical modules 200- It is possible to detect whether an event has occurred in places (ZONE1 to ZONEn) where 1 to 200-n) are installed.

In one embodiment of the present disclosure, the controller 100 analyzes a pattern of a diffraction pattern of a plurality of received light signals ROS1 to ROSn in real time, and compares the pattern with a previously stored reference pattern to determine whether an event occurs and You can judge the characteristics of the event.

In another embodiment of the present disclosure, the controller 100 analyzes a waveform pattern of a plurality of received optical signals ROS1 to ROSn in real time and compares the pattern with a pre-stored reference waveform pattern to determine whether an event occurs or not. Characteristics can be judged.

12 is a flowchart illustrating an optical signal based monitoring method according to embodiments of the present disclosure. The monitoring method to be described with reference to FIG. 12 may correspond to the function of the monitoring system 10 described with reference to FIGS. 1 to 10.

Referring to FIG. 12, the controller 100 may identify a received optical signal representing a waveform pattern different from the reference waveform pattern (S210). In this embodiment, the controller 100 compares the waveform patterns of the plurality of received optical signals ROS1 to ROSn and the reference waveform pattern stored in the memory 160, and receives the optical signal representing a waveform pattern different from the reference waveform pattern. (Hereinafter referred to as event light signal) is identified.

Here, the waveform pattern may include a voltage waveform or a diffraction pattern of an optical signal.

According to embodiments, the controller 100 may analyze the waveform pattern by performing image analysis on the waveform pattern, waveform similarity analysis on the time axis, and scale comparison on period and amplitude through a learning algorithm using deep learning. In this embodiment, the reference waveform pattern stored in the memory 160 may be stored for each of the plurality of received optical signals ROS1 to ROSn.

The controller 100 determines an optical module in which an event corresponding to the event optical signal has occurred (S220). In this embodiment, the controller 100 may determine the optical module to which the event light signal is output from among the plurality of optical modules 200-1 to 200-n. For example, the wavelength of the event optical signal is detected and the optical module to which the incident light signal of the corresponding wavelength is incident is determined as the event optical module where the event has occurred.

The controller 100 may identify a place corresponding to the optical module where the event has occurred (S230). In this embodiment, the controller 100 identifies the place where the optical module in which the event occurred is installed among the plurality of places (ZONE1 to ZONEn) as the event occurrence place.

For example, when the wavelength of the event optical signal (the received optical signal where the event occurs) is 1530 nm in step S220, the second optical module 220-2 is determined as the event optical module, and in step S230, the second optical module This installed second location (ZONE2) is identified as the event location.

In one embodiment of the present disclosure, the controller 100 matches the IDs of the plurality of optical modules 200-1 to 200-n and the IDs of the plurality of places (ZONE1 to ZONEn) to correspond one-to-one to form a table. It is possible to store and identify a place where an optical module in which an event has occurred is installed as an event place among a plurality of places (ZONE1 to ZONEn) using the table. The table may be stored in the memory 160.

The controller 100 may provide a notification on the place where the identified event has occurred (S240). In this embodiment, the controller 100 may provide a notification indicating that an event has occurred at the identified event place in a visual, audible or tactile manner. That is, the controller 100 may provide a notification indicating that an event has occurred at the identified event location using a display, speaker, or haptic motor.

In one embodiment of the present disclosure, monitoring (that is, event detection) of the plurality of places is performed by using the received light signals output from the plurality of optical modules installed in the plurality of places, and among the plurality of places You can detect where the event occurred.

In an embodiment of the present disclosure, since a plurality of optical modules may be installed in a plurality of places, when adding a place to be monitored, only the optical modules need to be additionally installed, so that installation is simple. In particular, a boundary line may be formed when the locations are continuously connected, and a fence may be formed when the locations are continuously connected to form a closed loop.

According to the embodiments of the present disclosure, since the same light is diverged and moved in different directions to measure a change in waveform due to its phase difference, compared to an OTDR type optical fiber sensor that measured only a change in amplitude of a light-receiving unit by conventional refraction/reflection Since the event can be detected with a sensitivity of 1000 times or more, monitoring accuracy and stability are high.

According to embodiments of the present disclosure, since a plurality of received signals output from a plurality of optical modules are combined into one combined reception signal and transmitted to a controller, the accuracy and stability of detection are high even if the number of optical modules increases. There is.

A method according to embodiments of the present disclosure may be implemented with instructions that are stored in a computer-readable storage medium and executable by a processor.

Storage media, whether direct and/or indirect, whether in a raw state, a formatted state, an organized state, or any other accessible state, a relational database, a non-relational database, an in-memory database, Or, it can include a database that includes a distributed type, such as other suitable databases that can store data and allow access to such data through a storage controller. In addition, the storage medium includes a primary storage device, a secondary storage device, a tertiary storage device, an offline storage device, a volatile storage device, a nonvolatile storage device, a semiconductor storage device, a magnetic storage device, an optical storage device, and a flash. Storage device, hard disk drive storage device, floppy disk drive, magnetic tape, or any other suitable data storage medium.

Although the present disclosure has been described with reference to the embodiments shown in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom. Therefore, the true technical protection scope of the present disclosure should be determined by the technical spirit of the appended claims.

10: Optical signal based monitoring system
100: controller
200-1~200-n: Optical modules
IOS_CB: Combined incident light signal
ROS_CB: Combined received optical signal
IOS1~IOSn: incident light signals
ROS1~ROSn: received optical signals
OP1~OPn: Optical paths
ZONE1~ZONEn: Places

Claims (16)

A controller for outputting a combined incident light signal combined with incident light signals having a plurality of wavelengths; And
It includes a plurality of optical modules for monitoring a plurality of places using the combined incident light signal,
Each of the plurality of optical modules branches into two incident light signals having a wavelength selected from the combined incident light signals, and then proceeds in opposite directions at both ends of the optical path installed at the place, and then combines to generate a received light signal. And filtering the incident light signal and generating the received light signal by advancing the incident light signal through an optical path installed in a corresponding place,
The controller receives the received optical signal, determines whether a phase difference occurs between the received optical signal and the incident optical signal, and receives the combined received optical signal generated by combining received optical signals generated in the respective optical modules. Analysis to detect whether an event has occurred in any of the plurality of places,
The optical path is an optical signal-based monitoring system consisting of an optical path having a length of an integer multiple of the wavelength of the incident light signal. delete According to claim 1, wherein the controller,
A plurality of optical generators that generate optical signals having a different number of wavelengths than the number of places; And
An optical signal based monitoring system comprising a combiner that combines the optical signals generated by the plurality of optical generators and outputs the combined incident light signal. According to claim 3, The controller,
And a processor capable of determining whether an event occurs, the type of the generated event, and the place where the event occurs by analyzing the combined received optical signal detected by controlling the light generator.
The processor is an optical signal-based monitoring system comprising a signal generator for determining the wavelength and intensity of the optical signal generated by the optical generator. According to claim 1, wherein the controller,
Further comprising a received optical signal divider for separating the combined received optical signal into a plurality of received optical signal according to the wavelength,
The controller is an optical signal based monitoring system for detecting the waveform and wavelength of the plurality of received optical signals. The method according to any one of claims 1 and 3 to 5,
Each of the plurality of optical modules,
An incident light splitter separating the incident light signal into two optical signals;
A pair of optical couplers disposed at both ends of the optical path, the optical signal passing through the optical path passing through and the optical signal returning after proceeding along the optical path reflecting; And
An optical signal based monitoring system including a combiner that combines the optical signals reflected from the pair of optical couplers to generate a received optical signal. The method of claim 6,
A first optical module among the plurality of optical modules combines the received optical signal with an optical signal obtained by combining received optical signals generated from optical modules disposed at a rear end of the first optical module to receive the combined received optical signal. It includes a receiving optical signal combiner to generate,
The received optical signal combiner of the first optical module, an optical signal-based monitoring system for outputting the combined received optical signal generated by combining all received optical signals received from all of the plurality of optical modules to the controller. The method of claim 6,
The incident light splitter of each of the plurality of optical modules separates the incident light signal of a selected wavelength to be used by the optical module from the combined incident light signal, and then combines the incident light signal including optical signals of different wavelengths from each of the optical modules. Optical signal-based monitoring system that bypasses the incident optical divider of the optical module in the stage. The method of claim 5, wherein the controller,
A detector for detecting a waveform of each received optical signal separated by the received optical signal distributor; And
Further comprising a reference waveform pattern corresponding to the waveform of the incident light signal of each wavelength and a memory for storing the waveform pattern of the detected received light signal,
The controller determines whether an event has occurred by comparing the waveform of the reference pattern stored in the memory with the waveform of the detected received light signal; An optical signal-based monitoring system that identifies that an event has occurred in a place where the optical module in which an incident light signal having a wavelength corresponding to the wavelength of the received optical signal determined to have occurred is selected. The method of claim 9,
The detector includes a photodiode, and the photodiode is an optical signal based monitoring system that detects a change in the optical voltage caused by the combined received optical signal when the combined received optical signal is applied. In the monitoring method using an optical signal-based monitoring system comprising a plurality of optical modules and a controller for controlling the optical modules,
The controller outputting a combined incident light signal in which incident light signals having a plurality of wavelengths are combined;
Each of the plurality of optical modules filters an incident light signal having a wavelength selected from among the combined incident light signals, and splits the incident light signal into two, so that the optical path is installed at any one of a plurality of places corresponding to the incident light signal. Generating a received optical signal by combining at both ends in a direction opposite to each other;
Receiving, by the controller, a combined received optical signal generated by combining received optical signals generated in the respective optical modules; And
The controller receives the received light signal, determines whether a phase difference occurs between the received light signal and the incident light signal, and analyzes the combined received light signal to determine whether an event has occurred in any of the plurality of places. Including detecting,
The optical path is a monitoring method comprising an optical path having a length that is an integer multiple of the wavelength of the incident light signal. delete The method of claim 11, wherein the step of outputting the combined incident light signal,
Generating, by the controller, optical signals having a different number of wavelengths than the number of places; And
And combining the generated optical signals having different wavelengths and outputting the combined incident light signal. The method of claim 11, wherein the step of analyzing the combined received light signal,
Separating the combined received optical signal into a plurality of received optical signals according to a wavelength by the controller; And
And detecting waveforms and wavelengths of the plurality of received optical signals. The method of claim 11, wherein the monitoring method,
A first optical module among the plurality of optical modules combines the received optical signal and the optical signals generated by the optical modules disposed at the rear end of the first optical module to combine the combined optical signals to generate a combined received optical signal. To do; And
And monitoring, by the first optical module, outputting the combined received optical signal to the controller. 15. The method of claim 14, The step of determining whether an event has occurred in the place,
Detecting a waveform of each received optical signal from which the controller is separated;
Comparing, by the controller, a reference waveform pattern corresponding to the waveform of the incident light signal and a waveform pattern of the detected received light signal;
Comparing and determining whether an event has occurred, and a monitoring method comprising determining that an event has occurred in a place where the optical module in which an incident light signal having a wavelength corresponding to the wavelength of the received optical signal determined to have occurred is selected is installed. .

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