JP4665779B2 - Fence vibration sensor device - Google Patents

Description

  The present invention relates to a fence vibration sensor device using an optical fiber ring interference type vibration sensor.

  An optical fiber ring interference type sensor has been conventionally provided as a sensor for detecting illegal intrusion by attaching to a fence installed so as to surround a vast area to be warned (for example, Patent Document 1).

  The sensor configuration disclosed in Patent Document 1 uses a single optical fiber loop shared by optical fiber ring interference type sensors that use light of different wavelengths, and simultaneously observes the intensity of two interfering light beams to obtain an excitation position. And the optical path length variation amount is calculated.

A loop-shaped optical path of such an optical fiber ring interference type sensor is attached to, for example, a fence arranged so as to surround a vast warning area, and a fence vibration sensor device that detects illegal intrusion from the vibration of the fence is configured. In this case, since an intrusion position can be specified, there is an advantage that an illegal intruder can be quickly captured.
JP 2002-365058 A (paragraphs 0027 to 0032)

  As described above, if the optical fiber ring interference type sensor disclosed in Patent Document 1 is used for the fence vibration sensor device, there is an advantage that the intrusion position can be specified, but there are also the following unsolved problems. That is, when the fence vibrates due to rain, wind, or the like, the vibration position may be erroneously detected as the entry position. Therefore, when trying to reduce the sensitivity by reducing the sensitivity, there is a problem that the actual illegal intrusion is overlooked and leads to a false alarm.

  In addition, when there is a gate (gate) in a part of the stretched fence, it is designed to embed the optical fiber in the ground at this gate position, but the car passes over the buried position. In some cases, vibrations that occur when this occurs are detected. Although it is possible to take measures such as installing separate fence vibration sensor devices on both sides of the gate position so as not to detect such vibrations, there is a new problem that the installation cost becomes high .

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fence vibration sensor device that can reduce false alarms and obtain high reliability.

In order to achieve the above object, in the invention of claim 1, an optical fiber which is attached to the fence so as to follow the circumferential direction of the fence provided so as to surround the warning area and forms a loop-shaped optical path, and this light A light source unit that makes an optical signal enter the optical path so that the propagation direction is different from an appropriate position of the fiber, and interference light obtained by combining the optical signals that propagate in the optical path in different directions and are emitted at the appropriate position are received. A light receiving unit that outputs an interference intensity signal indicating the interference intensity, a distance calculating unit that obtains a distance from the excitation point to the light receiving point based on the interference intensity signal output from the light receiving unit, and When the level of the interference intensity signal exceeds a predetermined threshold and a predetermined condition is satisfied while monitoring the level change, the distance obtained by the distance calculating means is the distance from the excitation point to the light receiving point. And a judging means for outputting a constant to determine a result, the condition, the peak level of the threshold value the interference intensity time signal level exceeds sequentially or the threshold the interference intensity signal is within a predetermined time And the fence is divided into a plurality of warning zones in the circumferential direction, and the threshold value and the sensitivity used by the determination means are set for each of the warning zones .

According to the invention of claim 1, the vibration applied to the fence by the intrusion act can be distinguished from the transient vibration, and the distance of the excitation point by the intrusion act can be accurately measured. Even when a long-distance fence that surrounds is monitored with a single alarm system, it is possible to accurately grasp the location where the intrusion occurred, and as a result, high reliability can be obtained, and optical fiber is used. Since it is possible to monitor over a long distance simply by attaching to the fence along the fence, it is possible to reduce the installation cost of the alarm system using the fence vibration sensor device. Further, the threshold value and conditions for determining the distance can be set in accordance with the state of the fence installation location and the like, and the reliability can be improved. In addition, the sensitivity can be set for each part of the fence with different environmental conditions, and the part that cannot be infiltrated can be removed from the detection target, thus reducing the cause of false alarms and improving the reliability. In addition, even if a single vibration occurs, the occurrence of false alarms can be reduced because the determination is made for each warning zone in the case of occurrence for each warning zone.

In the invention of claim 2, an optical fiber attached to the fence to form a loop-like optical path along the circumferential direction of the fence provided so as to surround the warning area, and the propagation direction from the appropriate position of the optical fiber are different. A light source unit that causes an optical signal to enter the optical path, and an interference intensity signal that indicates interference intensity by receiving interference light obtained by combining the optical signals that propagate in the optical path in different directions and exit at the appropriate position , A distance calculating means for obtaining a distance from the excitation point to the light receiving point based on the interference intensity signal output from the light receiving unit, and the interference intensity while monitoring the level change of the interference intensity signal When the signal level exceeds a predetermined threshold value and a predetermined condition is satisfied, the distance obtained by the distance calculation means is determined as the distance from the excitation point to the light receiving point, and a determination result is output. And means, said condition Ri number der the time or the threshold the threshold level of the interference intensity signal exceeds continuously the peak level of the interference intensity signal exceeds within a predetermined time, the determination The means is characterized in that when the peak level of the interference intensity signal to be monitored is detected a predetermined number of times within a predetermined time at a level lower than the threshold, the threshold is increased by a predetermined level .

According to the invention of claim 2, the vibration applied to the fence due to the intrusion act can be distinguished from the transient vibration, and the distance of the excitation point due to the intrusion act can be accurately measured. Even when a long-distance fence that surrounds is monitored with a single alarm system, it is possible to accurately grasp the location where the intrusion occurred, and as a result, high reliability can be obtained, and optical fiber is used. Since it is possible to monitor over a long distance simply by attaching to the fence along the fence, it is possible to reduce the installation cost of the alarm system using the fence vibration sensor device. Further, the threshold value and conditions for determining the distance can be set in accordance with the state of the fence installation location and the like, and the reliability can be improved. Furthermore, it is possible to prevent the occurrence of false alarms for events such as wind that continuously vibrate the fence, thereby further improving reliability.

  In the invention of claim 3, in the invention of claim 1 or 2, the determination means has a function of determining a vibration event occurring in the fence based on a temporal change waveform of the level of the interference intensity signal, The threshold value is set for each vibration event assumed in advance, and the threshold value corresponding to the determined vibration event is compared with the level of the interference intensity signal.

  According to the invention of claim 3, by setting thresholds corresponding to various events that cause the fence to vibrate, it is possible to give high reliability to the distance determination for different vibration events.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the determination means includes the distance calculation means based on a temporal change waveform of the level of the interference intensity signal and the interference intensity signal. It is determined whether there are one or two excitation points from the waveform of the change in the distance value over time, the level of the interference intensity signal and the threshold value, and the distance data determined by the conditions. In this case, it has a function of outputting an alarm judgment result.

According to the invention of claim 4 , even when the fence is vibrated simultaneously at two locations and the distance of the excitation point cannot be determined, the alarm can be issued. Reliability can be increased.

  The present invention distinguishes the vibration applied to the fence due to the intrusion action from the transient vibration, and can accurately measure the distance of the excitation point due to the intrusion action. Even when the fence is monitored by a single alarm system, it is possible to accurately determine the location where the intrusion occurred, and the reliability of the alarm system can be improved. It is possible to reduce the installation cost of the alarm system to be used because it is possible to monitor over a long distance simply by mounting along the side.

(Embodiment 1)
FIG. 1 shows a schematic configuration of an alarm system using the fence vibration sensor device of the present embodiment. The fence vibration sensor device (I) is an optical fiber ring interference type disclosed in Patent Document 1 described above. The sensor unit (II) is used as a basic configuration for detecting the vibration position, and the vibration applied to the fence 2 by the intrusion act in this basic configuration is distinguished from the transient vibration, and the distance of the excitation point by the intrusion act It is characterized in that it includes a determiner (determination means) for accurately measuring.

  As an alarm system, the fence vibration sensor device (I) and an alarm / display device that displays the distance to the excitation point based on the distance data determined by the determination device 4 of the fence vibration sensor device (I) and issues an alarm. And 5.

Optical fiber ring interferometer type sensor unit of the basic structure (II), the loop shape is disposed along the circumferential direction of the fence 1 is disposed Minor X to enclose Nyo be so that as shown in FIG. 1 It comprises an optical path and a distance calculator 3.

The loop-shaped optical path includes two optical fibers 2a and 2b for detection, which are attached to the fence 1 and arranged close to each other at both ends, and respective input / output ports at appropriate ends of both optical fibers 2a and 2b. Four wavelength division branching couplers (hereinafter referred to as WDM <Wavelength Division Multiplexing> couplers) 101 to 104 and one of branching ports of the WDM couplers 101 and 102 connected to one end side of the optical fibers 2a and 2b. connecting the optical fiber 2c 1, optical fibers 2a, is composed of one each other branch port at the other end of the WDM coupler 103 and 104 2b in the optical fiber 2c2 to each connection, couplers 101 to for each wavelength branch The other of the 104 branching ports is connected to the corresponding optical branching couplers 71 and 72 (see FIG. 2) in the distance calculator 3 via optical fibers 2d1 to 2d4, respectively. It is.

Distance calculator 3, corresponding to the optical branching coupler 71, the light source unit 61 and the light receiving portion 81 and the driving unit 301 to the light source unit 61 is driven to emit light having a wavelength lambda ₁ to a photodiode consisting of a laser diode And a light source unit 62 made of a laser diode, a light receiving unit 82 made of a photodiode, and a drive unit 302 for driving the light source unit 62 to emit light of wavelength λ2. The light from the light source sections 61 and 62 is incident on the optical branch couplers 71 and 72 via the optical fibers 2e1 and 2e2, and the light emitted from the optical branch couplers 71 and 72 is received via the optical fibers 2f1 and 2f2. Incident on the portions 81 and 82.

  The received light signals converted into electric signals by the light receiving units 81 and 82 are amplified by the amplification units 311 and 312 and further A / D converted by the A / D conversion units 321 and 322 so as to be taken into the arithmetic processing unit 33. It has become.

  FIG. 3 shows the connection configuration of the sensor parts, where the optical path length of the optical fiber 2a is La, the optical path length of the optical fiber 2b is Lb, the optical path length of the optical fiber 2c1 is Ld, and the optical path length of the optical fiber 2c2 is Lg. The optical path length of the optical fiber 2d1 is Lc, the optical path length of the optical fiber 2d2 is Le, the optical path length of the optical fiber 2d3 is Lf, the optical path length of the optical fiber 2d4 is Lh, the optical path length of the optical fiber 2e1 is Li, and the optical fiber 2e2 The optical path length is Lk, the optical path length of the optical fiber 2f1 is Lj, and the optical path length of the optical fiber 2f2 is L1.

And Thus, in FIG. 3, the light of the wavelength λ1 of one of the light source unit 61 is branched through the optical fiber 2 e1 enters the light branching and coupling portion 71, the length Lc + La + Lg + Lb + Le via the WDM coupler 101, 102 The light propagates in the clockwise and counterclockwise directions, and these propagating lights are coupled by the optical branching and coupling unit 71 through the WDM couplers 101 and 102, and further received by the light receiving unit 81 through the optical fiber 2f1. .

Light of the wavelength λ2 of the other light source unit 62 is branched through the optical fiber 2 e2 incident on the light branching and coupling part 72, the clockwise optical path length Lf + Lb + Ld + La + Lh through the WDM coupler 103 and 104, counterclockwise These propagating lights are coupled by the optical branching and coupling unit 72 through the WDM couplers 103 and 104, and further received by the light receiving unit 82 through the optical fiber 2f2. In this way, a fiber ring interference type sensor part is configured by propagating through the looped optical path clockwise and counterclockwise.

  Here, when vibration is applied to the optical path, the principle of obtaining the distance Lp to the excitation point P is disclosed in the above-mentioned Patent Document 1, but this point will be briefly described again.

First, the phase difference θ1 between the clockwise light and the counterclockwise light having the wavelength λ ₁ observed by the light receiving unit 71 is θ ₁ (t) = φ ₁ (t− (Lp + Lc + Lj) · n / c).
−φ ₁ (t− (La−Lp + Lg + Lb + Le + Lj) · n / c) + θ ₀
(Expression 1)
However,
n: Core refractive index of the optical fiber used c: Speed of light θ ₀ : Initial value in a static state In addition, the phase difference θ2 between the clockwise light and the counterclockwise light of wavelength λ ₂ observed by the light receiving unit 72 is also , Θ ₂ (t) = φ ₂ (t− (Lp + Ld + Lb + Lf + Ll) · n / c)
−φ ₂ (t− (La−Lp + Lh + Ll) · n / c) + θ ₀
... (Formula 2)
It is represented by

Here Lp is W DM coupler the distance to 101, also phi ₁ and phi ₂ is the excitation point P, respectively showing the phase variation amount of the wavelength lambda ₁ of light and the wavelength lambda ₂ of light in the excitation point P.

Further, since the phase fluctuation amounts φ ₁ and φ ₂ are caused by the same optical path length variation,
λ ₁ φ ₁ = λ ₂ φ ₂ (Formula 3)
It becomes.

In (Equation 1), (Equation 2), and (Equation 3), the only unknowns are Lp, φ ₁ , and φ ₂ , and other numbers are known if the measurement system is determined. Therefore, Lp, φ ₁ and φ ₂ can be obtained by solving the simultaneous equations.

If the time differential value of φ ₁ (φ ₂ ) hardly fluctuates within the time when light passes through the sensor part,
That is, if the excitation frequency is f,
If f << c / {n · (La + Lb + Lc + Le + Lg + Li + Lj)} and f << c / {n · (La + Lb + Ld + Lf + Lh + Lk + Ll)}, then Lp, φ ₁ , and φ ₂ can be expressed as follows.

Note that θ ₁ (t) and θ ₂ (t) can be obtained from the light intensity Ppd detected by the light receiving portions 71 and 72, since Pi and Pc are known if the sensor measurement system is determined. it can.

Ppd = Pi + (Pc (1 + cos θ)) / 2
However, Pc represents an interference component of light detected by the light receiving units 71 and 72, and Pi represents a non-interference component.

  In the above arithmetic processing, after the interference intensity signals obtained as electric signals by the light receiving units 71 and 72 are amplified by the amplification units 311 and 312, A / D conversion is performed by the A / D conversion units 32 and 3, respectively. The calculation unit 33 uses the D-converted interference intensity signal, and the distance Lp data obtained by the calculation unit 33, that is, the distance data α is output to the determiner 4.

  Incidentally, as described above, merely obtaining the distance Lp of the excitation point P leads to erroneous detection. Therefore, the determination unit 4 stores the distance data α output from the distance calculator 3 in the storage unit 40 over time. The time response data from the distance calculator 3, that is, the data β indicating the change in level of the interference intensity signal with time is monitored by the comparison determination unit 41, and the peak level (maximum value) of the level change and the sensitivity setting unit 9 set. When the peak level exceeds the threshold LA as shown in FIG. 4A, the comparison determination unit 41 determines that the predetermined condition for determining the distance is satisfied, and the storage unit shown in FIG. 40, the distance value at the time when the peak level exceeds is extracted from the time-dependent distance data α stored in 40, and the distance value is determined as the distance Lp ′ corresponding to the excitation point P. Output to the display 5. The alarm / display 5 displays the distance Lp ′ of the excitation point P on the display unit 51 based on the determination result under the control of the control unit 50 and performs a process of generating an alarm output γ.

Thus with the operator of the alarm system can know that the suspicious person by the alarm output γ and the distance Lp 'displayed on the alarm and display unit 5 tries to penetrate ascended or beating fence 1, a vibration point P Thus, it is possible to quickly take measures such as urging the security guard or setting the shooting direction of the surveillance camera in the direction of the excitation point P.

  Here, if the fence 1 is divided into a plurality of warning sections A1 to A8 in the circumferential direction (the number of sections is not limited to eight sections), the corresponding warning section is detected from the determined distance, It can also be displayed with the name of the alert section. FIG. 4 (c) shows a case where it is determined to be, for example, a warning zone A1.

  The determination condition for determining the distance is that the peak level of the interference intensity signal exceeds the threshold LA, but the number of times that the peak level of the interference intensity signal exceeds the threshold LA for a predetermined time is a predetermined number of times. The distance confirmation may be determined, or the distance confirmation may be determined when the level of the interference intensity signal exceeds the threshold LA continuously for a predetermined time. Not only exceeding the threshold LA but also stricter judgment conditions can reduce false alarms and improve reliability.

In order to prevent false alarm, such as a fence 1 I by the wind to vibrate, although the peak level of the interference intensity signal does not exceed the threshold value LA, the number of times exceeding a predetermined level during a predetermined time reaches a predetermined number of times In such a case, it is determined that the fence 1 is vibrating due to the wind, and the sensitivity setting unit 9 is controlled under the comparison determination unit 41 so that the threshold value LA becomes a certain level higher than the normal level. May be. This reduces sensitivity and avoids false alarms for events that cause the fence 1 to continuously vibrate due to wind.

  Further, when a plurality of warning zones A1 to A8 are set as described above, the sensitivity setter 9 can set the sensitivity including the threshold LA for determining the distance and the judgment condition for each warning zone A1 to A8. Also good. In other words, environmental conditions of each of the warning sections A1 to A8, for example, there is a tree in the vicinity of the fence 1, and the place where the branch or the like touches the fence 1 when the wind blows, or the vehicle traveling on the road facing the road By setting the sensitivity according to each environment such as a place that vibrates due to the influence, it is possible to perform the determination process of the distance determination using the sensitivity suitable for each of the warning sections A1 to A8, and further improve the reliability. Can do. Although the sensitivity setting device 9 is provided outside the determination device 5 in the illustrated example, it may be incorporated in the determination device 5.

  In addition, since the distance is determined with the sensitivity of each of the warning zones A1 to A8, when a single vibration such as that generated by a ball hitting occurs in different warning zones A1 to A8, each warning zone A1. Since the determination to determine the distance in .about.A8 is performed based on the set sensitivity, the occurrence of false alarms can be reduced.

Further, by setting the sensitivity for each of the warning sections A1 to A8, it becomes possible to determine the distance with the sensitivity set for each of the warning sections A1 to A8. For example, in the case where vibration is sequentially generated in two places, respectively. If the distances can be confirmed in the two warning areas A1 to A8, and the distances can be determined in two warning areas that are separated from each other by a certain distance, it is determined that there has been an illegal intrusion in two places, and the corresponding display An alarm can be issued by the alarm / display 5.
(Embodiment 2)
In the first embodiment, the change in the level of the interference intensity signal is monitored, and the distance is determined under the condition that the peak level of the level exceeds the threshold LA. There are a method of climbing 1, a method of cutting the fence 1 to make a hole, and a method of entering from the hole, and the phenomenon that appears due to the vibration of the fence 1 varies depending on the method. For example, when climbing the fence 1, a waveform of an interference intensity signal level change that exceeds the threshold value continuously for a certain time appears, whereas when the fence 1 is cut, it peaks every time the fence material is cut. A level change waveform with a level appears.

  Therefore, in this embodiment, the waveform of the level change of the interference intensity signal monitored by the comparison determination unit 41 is monitored, and the waveform of the level change of the interference intensity signal is “climbing” in advance as shown in FIG. In the case of a waveform that continuously exceeds the threshold value LB1 set corresponding to the predetermined time T1 or more, it is determined as “climbing”, and the distance calculated at the time of determination is extracted from the distance data α. The distance is determined, and the determination result is output to the notification display unit 5. The average value of the distance data α during the certain period T1 may be output as the fixed distance.

  On the other hand, when the peak level of the interference intensity signal exceeds the threshold value LB2 set in advance corresponding to the cutting of the fence 1 for a predetermined number of times (predetermined conditions), for example, four times within a predetermined time T2, The distance value calculated at the time of exceeding the fourth peak level, which is the determination time point, is extracted from the distance data α and output to the notification display unit 5. Of course, the average value of the distance values at each time point when the peak level of the interference intensity signal exceeds the threshold LB2 may be output as the determined distance. Further, the predetermined number of times is not limited to four. FIG. 5B shows a change with time of the value of the distance LP to the excitation point P calculated by the distance calculator 3.

Thus, in this embodiment, when the vibration event is judged and the threshold value corresponding to the vibration event is set, the peak level of the interference intensity signal is low as in the case where the fence 1 is cut as described above. Even in this case, it is possible to determine the distance of the excitation point P by this cutting, and display and issue a notification without overlooking the cutting of the fence 1 having a low interference intensity signal level. Of course, as a vibration event, if the threshold value is set by judging the event when the fence is applied to the ladder,
It is possible to deal with different illegal intrusion methods and to eliminate false alarms as well as false alarms.

Since the system configuration and the circuit hardware configuration other than the above-described operation are the same as those in the first embodiment, illustration and description are omitted.
(Embodiment 3)
By the way, in the first and second embodiments, the distance to the excitation point calculated by the distance calculator 3 is determined using a predetermined threshold and determination conditions while monitoring the level change of the interference intensity signal by the determiner 4. However, if there is excitation at two locations at the same time, each excitation point cannot be determined. Therefore, in the present embodiment, focusing on the fact that the time-series change of the distance data to the excitation point calculated by the distance calculator 3 is different between the case where the excitation point is one place and the case where there are two places. It is characterized in that the comparison / determination unit 41 of the determination device has a determination function for determining whether the excitation point is one or two.

  That is, when the vibration is applied at only one location, the time-dependent change waveform of the interference intensity signal level as shown in FIG. 5A and the distance value calculated by the distance calculator 3 as shown in FIG. Similar to the change waveform over time, but when there are two vibrations at the same time (for example, when “climbing” of the fence 1 is two at the same time as shown in FIG. 5A), When the fence 1 is cut at two locations at the same time, the waveform indicating the change over time in the level of the interference intensity signal in FIG. 6A and the distance calculator 3 shown in FIG. 6B are calculated. There is a difference between the change over time of the distance value. That is, for example, the level of the interference intensity signal due to “climbing” of the fence 1 exceeds the threshold LB1 for a certain time or more, while the change in distance value over time varies greatly up and down, and there is a difference between the two. Further, when the fence 1 is cut, the peak level of the interference intensity signal exceeds the threshold value LB2 within a certain period of time, whereas the change in the distance value over time changes from the peak PK of the upward <positive direction> to the downward direction. There are two types of peaks of <negative direction> peak PK 'as shown in FIG. 6B, and there is a difference between them.

  Therefore, in the present embodiment, the comparison determination unit 41 determines the time-dependent change waveform of the interference intensity signal level, the time-dependent change waveform of the distance value calculated by the distance calculator 3, the threshold value, and the determination condition. Compared with the distance value, it is determined whether there is two occurrences or one occurrence from the distance determined by the above-mentioned difference and the threshold and the determination condition. Is output to the alarm / display 5. Upon receiving this determination result, the alarm / display unit 5 generates an intrusion display and an alarm output. That is, although the distance to the excitation point cannot be determined, it is possible to cope with illegal intrusion by generating a two-part intrusion display and an alarm.

  Since the system configuration and the circuit hardware configuration other than the above-described operation are the same as those in the first embodiment, illustration and description are omitted. In addition, since the determination of the distance when there is only one excitation point is performed in the same manner as in the third embodiment, the description is omitted here.

1 is a configuration diagram of an alarm system using Embodiment 1. FIG. 1 is a circuit block diagram of an alarm system used in Embodiment 1. FIG. FIG. 2 is a schematic configuration diagram of a sensor unit according to the first embodiment. FIG. 4 is a waveform diagram for explaining operation of the first embodiment. FIG. 6 is a waveform diagram for explaining operation of the second embodiment. FIG. 10 is a waveform diagram for explaining operation of the third embodiment.

Explanation of symbols

(I) Fence vibration sensor device
(II) Sensor part
X Warning area 1 Fence 2 Optical fiber 3 Distance calculator 4 Judger 5 Alarm / display 9 Sensitivity setter

Claims (4)

An optical fiber attached to the fence to form a loop-shaped optical path along the circumferential direction of the fence provided so as to surround the warning area;
A light source unit that makes an optical signal enter the optical path so that the propagation direction is different from a proper position of the optical fiber;
A light receiving unit that receives interference light obtained by combining the optical signals propagating in different directions in the optical path and exiting at the appropriate position, and outputs an interference intensity signal indicating interference intensity;
Distance calculating means for obtaining a distance from the excitation point to the light receiving point based on the interference intensity signal output from the light receiving unit;
When the level of the interference intensity signal exceeds a predetermined threshold and a predetermined condition is satisfied while monitoring the level change of the interference intensity signal, the distance obtained by the distance calculation means is calculated from the excitation point to the light receiving point. Determination means for confirming the distance and outputting the confirmation result ;
The condition is a time when the level of the interference intensity signal continuously exceeds the threshold or the number of times that the peak level of the interference intensity signal exceeds the threshold within a certain time.
The fence vibration sensor device, wherein the fence is divided into a plurality of warning sections in the circumferential direction, and the sensitivity including the threshold value and the condition used in the determination unit is set for each of the warning sections . An optical fiber attached to the fence to form a loop-shaped optical path along the circumferential direction of the fence provided so as to surround the warning area;
A light source unit that makes an optical signal enter the optical path so that the propagation direction is different from a proper position of the optical fiber;
A light receiving unit that receives interference light obtained by combining the optical signals propagating in different directions in the optical path and exiting at the appropriate position, and outputs an interference intensity signal indicating interference intensity;
Distance calculating means for obtaining a distance from the excitation point to the light receiving point based on the interference intensity signal output from the light receiving unit;
When the level of the interference intensity signal exceeds a predetermined threshold and a predetermined condition is satisfied while monitoring the level change of the interference intensity signal, the distance obtained by the distance calculation means is calculated from the excitation point to the light receiving point. Determination means for confirming the distance and outputting the confirmation result;
The conditions, Ri number der the time or the threshold the threshold level of the interference intensity signal exceeds continuously the peak level of the interference intensity signal exceeds within a predetermined time,
It said determination means, a certain level that you wherein a higher fence vibration sensor device the threshold when the peak level of the monitor interference intensity signal is a predetermined number of times detected within a predetermined time, lower than the threshold level.   The determination means has a function of determining a vibration event occurring in the fence based on a temporal change waveform of the level of the interference intensity signal, and sets and determines the threshold value for each vibration event assumed in advance. The fence vibration sensor device according to claim 1, wherein the threshold value corresponding to the vibration event is compared with a level of the interference intensity signal. The determination means includes a temporal change waveform of the level of the interference intensity signal, a temporal change waveform of a distance value obtained by the distance calculation means based on the interference intensity signal, a level of the interference intensity signal, and the level of the interference intensity signal. It has a function of judging whether there are one or two excitation points from comparison with a threshold value and distance data determined under the above conditions, and outputting an alarm judgment result in the case of two places. The fence vibration sensor device according to any one of claims 1 to 3 .

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