Monitoring system, monitoring method and program

Abstract

Since it is difficult to determine the correspondence between points on the optical fiber and points on the monitored object, the monitoring system includes an acquisition means for acquiring multiple amplitudes of vibration at multiple points on the optical fiber cable based on light propagating through the optical fiber cable attached to the monitored object, a generation means for generating a vibration mode of the monitored object based on the multiple amplitudes, and a detection means for detecting points on the monitored object that correspond to the points on the optical fiber based on the vibration mode.

Description

[Technical Field]

[0001] The present invention relates to a monitoring system and the like, and more particularly to the correspondence between points on an optical fiber cable and points on a monitored object. [Background technology]

[0002] In recent years, optical fiber sensing technology has been developed to acquire environmental information such as vibrations and temperature around optical fiber cables. In typical optical fiber sensing technology, a monitoring device transmits pulsed light through an optical fiber cable attached to a monitored object such as a bridge. The monitoring device acquires environmental information around the monitored object by analyzing the backscattered light of the pulsed light.

[0003] For example, Patent Document 1 discloses an optical fiber sensing technology for monitoring a structure using an optical fiber cable attached to the structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 213060 Summary of the Invention [Problem to be solved by the invention]

[0005] In general optical fiber sensing technology, a monitoring device acquires information about the environment and surroundings between points on an optical fiber cable and points on the monitored object, which is necessary for monitoring multiple points within the monitored object. However, it is difficult to determine the correspondence between points on the optical fiber cable and points on the monitored object.

[0006] An exemplary object of the present invention is to provide a monitoring system and the like, and in particular to determine correspondence between points on a fiber optic cable and points on a monitored object. [Means for solving the problem]

[0007] A monitoring system according to a preferred embodiment of the present invention comprises: an acquisition means for acquiring a plurality of amplitudes of vibration at a plurality of points on the optical fiber cable based on light propagating through the optical fiber cable attached to the monitoring target; a generating means for generating a vibration mode of the monitoring target based on the plurality of amplitudes; a detection means for detecting a point on the monitoring object corresponding to a point on the optical fiber cable based on the vibration mode; Equipped with.

[0008] A monitoring method according to a preferred embodiment of the present invention comprises: acquiring a plurality of amplitudes of vibration at a plurality of points on the optical fiber cable based on light propagating through the optical fiber cable attached to the monitoring target; generating a vibration mode of the monitored object based on the plurality of amplitudes; detecting points on the monitored object corresponding to points on the optical fiber cable based on the vibration modes; Includes:

[0009] A non-transitory computer-readable storage medium according to a preferred embodiment of the present invention comprises: acquiring a plurality of amplitudes of vibration at a plurality of points on the optical fiber cable based on light propagating through the optical fiber cable attached to the monitoring target; generating a vibration mode of the monitored object based on the plurality of amplitudes; detecting points on the monitored object corresponding to points on the optical fiber cable based on the vibration modes; The program for causing a computer to execute the above is stored. [Effects of the Invention]

[0010] An exemplary advantage of the present invention is, among other things, providing a monitoring system, a monitoring method, and a storage medium that establishes correspondence between points on a fiber optic cable and points on a monitored object. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a monitoring system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining a monitoring system according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram for explaining a monitoring system according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram for explaining a monitoring system according to a first embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart illustrating the operation of the monitoring system according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a diagram for explaining a monitoring system according to a first embodiment of the present invention. [Figure 7] FIG. 7 is a diagram for explaining a monitoring system according to a first embodiment of the present invention. [Figure 8] FIG. 8 is a block diagram showing an example of the configuration of a monitoring device according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart illustrating the operation of the monitoring device according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment

[0013] A monitoring system 1 will be described with reference to Fig. 1. Fig. 1 is a block diagram showing an example configuration of the monitoring system 1. As shown in Fig. 1, the monitoring system 1 includes a monitoring device 10 and an optical fiber cable 20. In the monitoring system 1, the monitoring device 10 uses the optical fiber cable 20 as a sensor to monitor the environment around the optical fiber cable 20. In the first embodiment, the optical fiber cable 20 is laid along a road on which vehicles travel. The monitoring target, which will be described later, is a bridge included in the road.

[0014] The monitoring device 10 includes an acquisition unit 11, an identification unit 12, a generation unit 13, and a detection unit 14. The acquisition unit 11, the identification unit 12, the generation unit 13, and the detection unit 14 are also referred to as an acquirer, an identifier, a generator, and a detector, respectively. As shown in FIG. 1 , the monitoring device 10 is connected to an optical fiber cable 20. The monitoring device 10 includes a light source and a light receiving unit (not shown). The light source outputs pulsed light to the optical fiber cable 20. The light source may repeatedly output pulsed light at predetermined intervals. In the optical fiber cable 20, Rayleigh backscattered light is generated at multiple points on the optical fiber cable 20 as the pulsed light propagates through the optical fiber cable 20. The light receiving unit receives the Rayleigh backscattered light from multiple points on the optical fiber cable 20. The light receiving unit detects the amplitude of vibration at multiple points on the optical fiber cable 20 by analyzing the Rayleigh backscattered light. For example, the light receiving unit detects the amplitude of vibration at multiple points on the optical fiber cable 20 based on a phase change of the Rayleigh backscattered light. The light receiving means outputs information indicating the amplitude of vibration at a plurality of points on the optical fiber cable 20 to the acquiring means 11. The points on the optical fiber cable 20 refer to points on the surface of the optical fiber cable 20.

[0015] The acquiring means 11 acquires the amplitude of vibration at a plurality of points on the optical fiber cable 20 from the Rayleigh backscattered light propagating through the optical fiber cable 20 attached to the monitoring target. The acquiring means 11 may include the light source and the light receiving means described above.

[0016] The acquiring means 11 may calculate the sum of multiple amplitudes of vibration in each section on the optical fiber cable 20. Specifically, the acquiring means 11 calculates the sum of amplitudes acquired based on Rayleigh backscattered light from points in a predetermined section on the optical fiber cable 20 as the sum of amplitudes in the predetermined section on the optical fiber cable 20. The acquiring means 11 generates a first graph showing a first correspondence relationship between the sum of the sections and the sections. The acquiring means 11 further acquires multiple amplitudes of vibration at multiple points on the optical fiber cable 20 multiple times over a certain period of time. The acquiring means 11 generates a second graph as shown in FIG. 2 showing a second correspondence relationship between each of the multiple times and the first correspondence relationship.

[0017] The identification means 12 identifies the monitoring portion corresponding to the monitoring target based on a plurality of amplitudes of vibration at a plurality of points on the optical fiber cable 20. The operation of the identification means 12 will be described with reference to FIG.

[0018] FIG. 2 is a diagram showing the change over time in the amplitude of vibration at each point on the optical fiber cable 20, acquired by the acquisition means 11. The vertical axis of FIG. 2 represents time. The horizontal axis of FIG. 2 represents the distance from the monitoring device 10. The color intensity in FIG. 2 represents the amplitude of vibration. For example, the amplitude of the gray parts is greater than the amplitude of the black parts.

[0019] The line extending from the upper right to the lower left in FIG. 2 indicates the temporal approach of the vehicle to the monitoring device 10. The colors in FIG. 2 indicate that the vibrations occurring between points A and B are always greater than the vibrations occurring in other areas. If the monitored object is a bridge, the vibrations of the monitored object are always greater than the vibrations of the road. Therefore, the identification means 12 identifies that the monitored object is located in the area between points A and B.

[0020] As described above, the identification means 12 identifies a monitoring portion of the optical fiber cable 20 corresponding to the monitoring target based on the amplitude of vibration at multiple points on the optical fiber cable 20. For example, the identification means 12 identifies a portion where vibrations having an amplitude equal to or greater than a threshold are detected during a predetermined period as the monitoring portion. The M detection channels in FIG. 2 indicate different positions of the monitoring portion. The identification means 12 may identify multiple monitoring portions of the optical fiber cable 20. Alternatively, the identification means 12 may mask portions other than the monitoring portion and output only information about the monitoring portion to the outside.

[0021] The generating means 13 generates a vibration mode of the monitoring target based on the amplitudes of multiple vibrations for the monitoring portion identified by the identifying means 12. The operation of the generating means 13 will be described with reference to Figures 3 and 4. When the identifying means 12 identifies multiple monitoring portions, the generating means 13 generates a vibration mode for each monitoring target.

[0022] 3 is a diagram showing changes in vibration detected based on Rayleigh backscattered light from different positions on the monitored portion. The generating means 13 acquires information including changes in vibration at multiple points on the optical fiber cable 20 from the acquiring means 11.

[0023] As shown in Figure 2, the generation means 13 analyzes information including vibration changes to generate vibration modes of the monitored bridge. The analysis by the generation means 13 can be performed using a known method. For example, vibration modes can be extracted using a standard peak-picking method in the frequency domain. Another example is applying the frequency domain decomposition (FDD) method to the vibration signal from the fiber sensor. Because the phase change of Rayleigh backscattered light is a relative response to ambient vibrations, the vibration amplitude has different scales and offsets for each detection channel in the fiber cable. Because vibration modes represent global information about the structure, the generation means 13 standardizes each detection channel to, for example, unit variance so that the extracted vibration modes closely relate to the theoretical vibration mode shapes of the target bridge. In the FDD method, the vibration mode shapes are extracted using the following steps: 1. Estimate the spectral density matrix from the raw time series oscillations. 2. Perform singular value decomposition of the spectral density matrix. 3. Choose the dominant peak in the mean singular value. 4. The vibration modes correspond to the eigenvectors at the selected peak singular frequencies.

[0024] FIG. 4 shows the vibration modes of the monitored object. Specifically, mode 1 in FIG. 4 shows the primary vibration mode, mode 2 shows the secondary vibration mode, and mode 3 shows the tertiary vibration mode. The vertical axis of each vibration mode in FIG. 4 shows the amplitude of that vibration mode. The horizontal axis in FIG. 4 shows the point on the optical fiber cable 20. In this embodiment, the horizontal axis shows the portion between point A and point B as shown in FIG. 2. Therefore, the vibration modes in FIG. 4 show the vibration modes of the monitored portion corresponding to the monitored object. In other words, since the vibration of the monitored portion in the optical fiber cable 20 and the vibration of the monitored object are the same, FIG. 4 shows the vibration modes of the monitored object.

[0025] The detecting means 14 detects at least one point on the monitoring object that corresponds to a point on the optical fiber cable 20 based on the vibration mode. The point on the monitoring object indicates a point where the surface of the optical fiber cable 20 contacts the monitoring object. For example, the detecting means 14 detects that a point where the amplitude is zero in the first vibration mode is the end of the monitoring object. The detecting means 14 also detects that point C where the amplitude is zero in the second vibration mode of FIG. 4 is the center of the monitoring object. The detecting means 14 also detects that point D where the amplitude is zero in the third vibration mode of FIG. 4 is a point 1 / 3 of the way between the ends of the monitoring object. The detecting means 14 also detects that point E where the amplitude is zero in the third vibration mode of FIG. 4 is a point 2 / 3 of the way between the ends of the monitoring object. As described above, the detecting means 14 detects N-1 points on the monitoring object from the Nth vibration mode.

[0026] The detection means 14 may also detect other points on the monitored object based on the following method: The detection means 14 obtains the arcsine function of the input mode shape Ψ_n(x) from equation (1).

number

[0027] Since the arcsine is multi-valued, the detection means 14 calculates the angle between the angle (-π) / 2 and the angle π / 2, and calculates the weighting coefficient by dividing by π / 2. The detection means 14 calculates the rate of change between two consecutive points on the monitored object by applying forward differentiation.

[0028] The detection means 14 obtains the absolute amount of change in weight from equation (2). In equation (2), l is the length of the monitoring portion, and its value is set to 1.

number

[0029] The detection means 14 finds points on the monitored object x(m) by cumulatively calculating the changes in the absolute values ​​of the weights using equation (3), where |·| is an absolute function.

number

[0030] The detection means 14 normalizes the cumulative aggregated value between the value 0 and the value 1 to obtain the normalized monitoring target position x in equation (4). The final output variable x is a value between 0 and 1, and represents the distance of the monitoring portion from the monitoring start point.

number

[0031] Next, the operation of the monitoring system 1 will be described with reference to Fig. 5. The acquisition means 11 acquires the amplitude of vibration at each point on the optical fiber cable 20 (S101). For example, the amplitude of vibration at each point is derived based on the phase change of the Rayleigh backscattered light described above.

[0032] The identification means 12 identifies the monitoring portion in the optical fiber cable 20 that corresponds to the monitoring target based on the amplitude of the vibration acquired by the acquisition means 11 (S102). For example, if the monitoring target is a bridge, the portion of the optical fiber cable 20 that is attached to the bridge is the monitoring portion. If a portion of the optical fiber cable 20 other than the monitoring portion is attached to the road, the vibration of the monitoring portion will be greater than the vibration of the portion other than the monitoring portion. Therefore, the identification means 12 identifies the portion where vibrations with amplitudes equal to or greater than the threshold value are continuously detected as the monitoring portion.

[0033] The generating means 13 generates a vibration mode of the monitoring target by analyzing vibration information of a plurality of points on the optical fiber cable 20 (S103). A known method is used for the analysis by the generating means 13. The generating means 13 may generate a plurality of vibration modes as shown in FIG.

[0034] Based on the vibration mode, the detection means 14 detects at least one point on the monitoring target that corresponds to a point on the optical fiber cable 20 (S104). For example, the detection means 14 detects points corresponding to the ends of the monitoring target, the center of the monitoring target, a point 1 / 3 of the way between the ends of the monitoring target, and a point 2 / 3 of the way between the ends of the monitoring target.

[0035] As described above, the monitoring system 1 includes an acquiring means 11, a generating means 13, and a detecting means 14. The acquiring means 11 acquires multiple amplitudes of vibration at multiple points on the optical fiber cable 20 based on light propagating through the optical fiber cable 20 attached to the monitored object. The generating means 13 generates vibration modes of the monitored object based on the multiple amplitudes. The detecting means 14 detects points on the monitored object that correspond to points on the optical fiber cable 20. Therefore, the monitoring system 1 can associate points on the optical fiber cable 20 with points on the monitored object.

[0036] For example, it is possible to identify points on the optical fiber cable 20 that correspond to the end or center of the monitored object, so that the monitoring system 1 can accurately measure vibrations at the end or center of the monitored object.

[0037] FIG. 6 shows an error, which is the difference between the distance from a distributed acoustic sensor (DAS) to a certain position and the distance from the DAS to a certain position on the road. The vertical axis of FIG. 6 represents the error. The horizontal axis of FIG. 6 represents the distance from the DAS to a position on the road. The DAS corresponds to the monitoring device 10 in this embodiment. The above error becomes larger when the optical fiber cable is arranged in a loop. As shown in FIG. 6, the optical fiber cable is longer than the road. When the optical fiber cable is installed in an uneven arrangement, the monitoring system 1 can accurately measure vibrations at the edge or center of the monitored object by matching points on the optical fiber cable with points on the monitored object based on the vibration mode of the monitored object.

[0038] The monitoring device 10 may be implemented in a computer device 200 as shown in Fig. 7. Referring to Fig. 7, the computer device 200, such as a server, includes a processor (Central Processing Unit) 202, a memory 204, etc., a display device 206 that displays calibration results at bridge points, and a communication interface 208. The memory 204 includes, for example, semiconductor memory (e.g., random access memory (RAM), read-only memory (ROM), electrically erasable read-only memory (EEPROM)), and / or at least one of storage devices such as a hard disk drive (HDD), a solid-state drive (SSD), a compact disc (CD), and a digital versatile disc (DVD).

[0039] The communication interface 208 (such as a network interface controller (NIC)) may be configured to be communicatively connected to the detection device. A program 210 including program instructions (program modules) for executing the processes of the acquisition means 11, the identification means 12, the generation means 13, and the detection means 14 is stored in the memory 204.

[0040] The processor 202 is configured to read and execute a program 210 (program instructions) from the memory 204 to realize the functions and processes of the monitoring system 1. <Second embodiment>

[0041] An optical monitoring device 2 according to the second embodiment will be described with reference to Fig. 8. Fig. 8 is a block diagram showing an example of the configuration of the monitoring device 2. The monitoring device 2 includes an acquisition means 11, a generation means 13, and a detection means 14. The monitoring device 2 may have the same configuration, the same functions, and the same connection relationships as the monitoring device 10 according to the first embodiment.

[0042] The acquiring means 11 acquires a plurality of amplitudes of vibration at a plurality of points on the optical fiber cable based on light propagating through the optical fiber cable attached to the monitoring target. The acquiring means 11 may have the same configuration, the same functions, and the same connection relationships as the acquiring means 11 in the first embodiment.

[0043] The generating means 13 generates a vibration mode of a monitoring target based on a plurality of amplitudes of vibration at points on the optical fiber cable. The generating means 13 may have the same configuration, the same functions, and the same connection relationships as the generating means 13 in the first embodiment.

[0044] The detecting means 14 detects points on the monitoring target that correspond to points on the optical fiber cable based on the vibration mode. The detecting means 14 may have the same configuration, function, and connection relationship as the detecting means 14 in the first embodiment.

[0045] Next, the operation of the monitoring device 2 will be described with reference to Fig. 9. Fig. 9 is a flowchart for explaining the operation of the monitoring device 2 according to the second embodiment of the present invention. The acquisition means 11 acquires a plurality of amplitudes of vibration at a plurality of points on the optical fiber cable based on light propagating through the optical fiber cable attached to the monitoring object (S201). The generation means 13 generates a vibration mode of the monitoring object based on the plurality of amplitudes of vibration at a plurality of points on the optical fiber cable (S202). The detection means 14 detects points on the monitoring object that correspond to points on the optical fiber cable based on the vibration mode (S203).

[0046] As described above, the monitoring device 2 includes the acquiring means 11, the generating means 13, and the detecting means 14. Therefore, the monitoring device 2 can associate points on the optical fiber cable with points on the monitored object.

[0047] For example, it is possible to identify points on the optical fiber cable that correspond to the end or center of the monitored object, so that the monitoring device 2 can accurately measure vibrations at the end or center of the monitored object.

[0048] While the present invention has been particularly shown and described with reference to preferred embodiments thereof, the invention is not limited to these embodiments, and it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. an acquisition means for acquiring a plurality of amplitudes of vibrations at a plurality of points on an optical fiber cable attached to a monitoring target based on light propagating through the optical fiber cable; a generating means for generating a vibration mode of the monitoring target based on the plurality of amplitudes; a detection means for detecting a point on the monitoring object corresponding to a point on the optical fiber cable based on the vibration mode; Equipped with The acquisition means calculating a sum of the plurality of amplitudes in each section on the optical fiber cable; a monitoring system that generates a graph showing a first correspondence relationship between the sum of the plurality of amplitudes in the section and the section, further comprising an identification means for identifying a monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the optical fiber cable; the generating means generates the vibration mode corresponding to the monitoring target based on vibrations at a plurality of points on the monitoring portion; the identification means identifies the monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the optical fiber cable; the generating means standardizes vibrations at a plurality of points on the monitoring portion, and generates the vibration mode corresponding to the monitoring target based on the standardized vibrations at a plurality of points on the monitoring portion. Surveillance system.

2. The acquisition means acquiring the plurality of amplitudes of vibration a plurality of times; generating a graph showing a second correspondence between each of the plurality of times and the first correspondence; The monitoring system of claim 1 .

3. an acquisition means for acquiring a plurality of amplitudes of vibrations at a plurality of points on an optical fiber cable attached to a monitoring target based on light propagating through the optical fiber cable; a generating means for generating a vibration mode of the monitoring target based on the plurality of amplitudes; a detection means for detecting a point on the monitoring object corresponding to a point on the optical fiber cable based on the vibration mode; and an identification means for identifying a monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the optical fiber cable, the generating means generates the vibration mode corresponding to the monitoring target based on vibrations at a plurality of points on the monitoring portion; the identification means identifies the monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the optical fiber cable; the generating means standardizes vibrations at a plurality of points on the monitoring portion, and generates the vibration mode corresponding to the monitoring target based on the standardized vibrations at a plurality of points on the monitoring portion. Surveillance system.

4. The detection means detects which of the points of the monitoring target corresponds to the vibration mode point. The monitoring system according to any one of claims 1 to 3.

5. A computer comprising: acquiring a plurality of amplitudes of vibration at a plurality of points on an optical fiber cable attached to a monitoring target based on light propagating through the optical fiber cable; generating a vibration mode of the monitored object based on the plurality of amplitudes; detecting points on the monitored object corresponding to points on the optical fiber cable based on the vibration modes; calculating a sum of the plurality of amplitudes in each section on the optical fiber cable; generating a graph showing a first correspondence relationship between the sum of the plurality of amplitudes in the section and the section, The computer further comprising identifying a monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; The computer generating the vibration mode corresponding to the monitored object based on vibrations at a plurality of points on the monitored portion; identifying the monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; normalizing vibrations at a plurality of points on the monitoring portion, and generating the vibration mode corresponding to the monitoring target based on the normalized vibrations at a plurality of points on the monitoring portion; Monitoring method.

6. A computer comprising: acquiring a plurality of amplitudes of vibration at a plurality of points on an optical fiber cable attached to a monitoring target based on light propagating through the optical fiber cable; generating a vibration mode of the monitored object based on the plurality of amplitudes; detecting points on the monitored object corresponding to points on the optical fiber cable based on the vibration modes; identifying a monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; generating the vibration mode corresponding to the monitored object based on vibrations at a plurality of points on the monitored portion, The computer identifying the monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; normalizing vibrations at a plurality of points on the monitoring portion, and generating the vibration mode corresponding to the monitoring target based on the normalized vibrations at a plurality of points on the monitoring portion; Monitoring method.

7. acquiring a plurality of amplitudes of vibration at a plurality of points on an optical fiber cable attached to a monitoring target based on light propagating through the optical fiber cable; generating a vibration mode of the monitored object based on the plurality of amplitudes; detecting points on the monitored object corresponding to points on the optical fiber cable based on the vibration modes; calculating a sum of the plurality of amplitudes in each section on the optical fiber cable; generating a graph showing a first correspondence relationship between the sum of the plurality of amplitudes in the section and the section, further causing the computer to identify a monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; generating the vibration mode corresponding to the monitored object based on vibrations at a plurality of points on the monitored portion; identifying the monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; normalizing vibrations at a plurality of points on the monitored portion and generating the vibration mode corresponding to the monitored object based on the normalized vibrations at a plurality of points on the monitored portion; A program for causing the computer to execute the above.

8. acquiring a plurality of amplitudes of vibration at a plurality of points on an optical fiber cable attached to a monitoring target based on light propagating through the optical fiber cable; generating a vibration mode of the monitored object based on the plurality of amplitudes; detecting points on the monitored object corresponding to points on the optical fiber cable based on the vibration modes; identifying a monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; generating the vibration mode corresponding to the monitoring target based on vibrations at a plurality of points on the monitoring portion, identifying the monitoring portion corresponding to the monitoring target based on the plurality of amplitudes of vibration at the plurality of points on the fiber optic cable; normalizing vibrations at a plurality of points on the monitored portion and generating the vibration mode corresponding to the monitored object based on the normalized vibrations at a plurality of points on the monitored portion; A program for causing the computer to execute the above.

Images