Location evaluation device, location evaluation method, and program

Abstract

A position evaluation device (50) according to the present disclosure comprises: a vibration characteristics calculation unit (51) in which a signal indicating the characteristic vibration generated at each position of an optical fiber is input from a sensor and sensing data indicating the vibration characteristics of each position of the optical fiber is calculated on the basis of the input signal; a dissimilarity calculation unit (52) that calculates dissimilarity in the sensing data between two adjacent points in the optical fiber; and an environmental change position estimation unit (53) that uses the dissimilarity as a basis to estimate an environmental change position at which the environment of the optical fiber changes.

Description

Location evaluation device, location evaluation method, and computer-readable medium

[0001] The present disclosure relates to a location assessment device, a location assessment method, and a computer-readable medium.

[0002] A technology called optical fiber sensing makes it possible to detect vibrations and sounds occurring at any section of an optical fiber. Specifically, in optical fiber sensing, an optical fiber sensor inputs coherent pulsed light into an optical fiber and receives backscattered light from the optical fiber. The optical fiber sensor then detects the phase difference between the backscattered light generated at two points on the optical fiber, thereby detecting vibrations and sounds acting on the optical fiber in the phase difference evaluation section (gauge length section) between the two points. Such optical fiber sensors can be realized by phase-sensitive OTDRs (Phase-Sensitive Optical Time Domain Reflectometers) or DASs (Distributed Acoustic Sensors), but the following description assumes that the optical fiber sensor is a DAS.

[0003] However, existing optical fiber cables for communication, including existing optical fibers, are sometimes laid in areas away from the ground surface. Examples of such optical fiber cables for communication include optical fiber cables suspended on poles such as utility poles and steel towers, and OPGWs (Optical Ground Wires).

[0004] Figure 1 shows an example of the configuration of a sensing system using existing optical fibers suspended on poles aligned in one dimension. In the sensing system shown in Figure 1, existing optical fibers are suspended on poles 1 to 3, which are utility poles or steel towers. A DAS is connected to one end of the optical fibers.

[0005] DAS can detect the environment around the optical fiber based on vibration information that indicates vibrations acting on the optical fiber, such as wind and rain hitting the optical fiber, the presence or absence of lightning, the vibration mode of the pole, and the presence or absence of living things.

[0006] DAS can also detect abnormalities occurring around optical fibers based on sound information indicating sounds applied to the optical fibers, such as gunshots, explosions, and abnormal sounds caused by accidents.

[0007] However, if the installation conditions of the optical fiber are not taken into consideration, there is a possibility that the location of the vibration / sound generation may be erroneously estimated, such as excess optical fiber sections generated by optical fiber fusion splicing work, and overhead sections of optical fiber suspended above a pole.

[0008] Figure 2 shows an example of an erroneous estimation of the vibration occurrence location due to excess length of optical fiber. As shown in Figure 2, the position information of the vibration occurrence location measured by the DAS is the "length of the optical fiber from the DAS to the vibration point" (hereinafter defined as "DAS coordinates"). For example, the DAS can measure the vibration occurrence location on the DAS coordinates based on the time difference between the input of pulsed light and the reception of backscattered light from that pulsed light.

[0009] In the example of Figure 2, the excess length of the optical fiber is included in pillar 2. Therefore, if vibration occurs at a position farther away from the DAS than pillar 2, the vibration occurrence point on the distance from the DAS toward the pillar (hereinafter defined as "real world coordinates") will no longer match the vibration occurrence point on the DAS coordinates.

[0010] Therefore, when building a sensing system using optical fibers suspended on pillars, it is necessary to accurately know the environmental change positions where the optical fiber environment changes as DAS coordinates. The environmental change positions of the optical fiber include, for example, the positions of the pillars on which the optical fiber is suspended, the overhead sections of the optical fiber suspended between the pillars, and the excess length sections of the optical fiber.

[0011] An example of a method for matching real-world coordinates and DAS coordinates is to generate an event at a position whose real-world coordinates are known, and then match that position on the real-world coordinates with the vibration occurrence location or vibration occurrence section measured by the DAS for the vibration caused by that event.

[0012] Figure 3 shows an example of a method for aligning real-world coordinates with DAS coordinates by artificially vibrating a column suspending an optical fiber. As shown in Figure 3, when the column is artificially vibrated, the DAS measures the vibration occurrence section on the DAS coordinates. The position of the column on the real-world coordinates is then matched with the vibration occurrence section on the DAS coordinates. In the example of Figure 3, there is an excess length of optical fiber on the vibrated column. Therefore, the vibration occurrence section on the DAS coordinates corresponds to the excess length of optical fiber.

[0013] However, the method shown in Figure 3 has the following problems: - Since each and every pillar needs to be inspected, it takes a lot of man-hours. - When a pillar is vibrated, the vibration is transmitted to the overhead optical fiber on both sides of the pillar, causing the vibrating section to expand instantly. - This method cannot be applied to pillars where it is difficult to artificially generate vibrations (for example, large pillars such as steel towers).

[0014] For this reason, recently, methods have been proposed for determining the position on the DAS coordinates of a pole suspending an optical fiber, other than the method shown in Figure 3. For example, Patent Document 1 discloses a technology in which a section where the strength of vibration detected by optical fiber sensing is equal to or greater than a threshold is determined to be a section where a unique pattern of the utility pole is occurring, and the point in that section where the strongest vibration occurs is estimated to be the position of the utility pole.

[0015] International Publication No. 2020 / 044648

[0016] As described above, the technology described in Patent Document 1 focuses on the threshold value of vibration intensity (i.e., the magnitude of vibration), and estimates the point where the vibration with the greatest intensity occurs as the position of the utility pole. Therefore, the technology described in Patent Document 1 cannot estimate the position of the utility pole for points other than the point where the vibration with the greatest intensity occurs. Therefore, it is believed that there is still room for improvement in the accuracy of estimating the position of an environmental change in optical fiber, such as the position of a pole.

[0017] In view of the above-mentioned problems, an object of the present disclosure is to provide a position evaluation device, a position evaluation method, and a computer-readable medium that can improve the accuracy of estimating the position of an environmental change in an optical fiber.

[0018] A position evaluation device according to one embodiment includes a vibration characteristic calculation unit that receives a signal indicating a natural vibration generated at each position of an optical fiber from a sensor and calculates sensing data indicating the vibration characteristics of each position of the optical fiber based on the received signal; a dissimilarity calculation unit that calculates the degree of difference in the sensing data between two adjacent points of the optical fiber; and an environment change position estimation unit that estimates an environment change position where the environment of the optical fiber changes based on the degree of difference.

[0019] A position evaluation method according to one embodiment is a position evaluation method executed by a position evaluation device, and includes: a vibration characteristic calculation step of inputting a signal indicating a natural vibration generated at each position of an optical fiber from a sensor and calculating sensing data indicating the vibration characteristics of each position of the optical fiber based on the input signal; a dissimilarity calculation step of calculating the degree of difference in the sensing data between two adjacent points of the optical fiber; and an environment change position estimation step of estimating an environment change position where the environment of the optical fiber changes based on the degree of difference.

[0020] A computer-readable medium according to one embodiment is a non-transitory computer-readable medium having stored thereon a program to be executed by a computer, the program including: a vibration characteristic calculation step of receiving, from a sensor, a signal indicating a natural vibration occurring at each position of an optical fiber, and calculating sensing data indicating the vibration characteristics of each position of the optical fiber based on the received signal; a dissimilarity calculation step of calculating a degree of difference in the sensing data between two adjacent points of the optical fiber; and an environment change position estimation step of estimating, based on the degree of difference, an environment change position where the environment of the optical fiber changes.

[0021] According to the above-described aspects, it is possible to provide a position evaluation device, a position evaluation method, and a computer-readable medium that can improve the accuracy of estimating the position of an environmental change in an optical fiber.

[0022] 1 is a diagram showing an example of the configuration of a sensing system using existing optical fibers that suspend pillars lined up in a one-dimensional direction. FIG. 2 is a diagram showing an example of erroneous estimation of the location of vibration occurrence due to an excess length of optical fiber. FIG. 3 is a diagram showing an example of a method of aligning real-world coordinates and DAS coordinates by artificially vibrating a pillar on which an optical fiber is suspended. FIG. 4 is a diagram showing an example of an application of a position evaluation device according to a first embodiment. FIG. 5 is a diagram showing an example of the configuration of a position evaluation device according to a first embodiment. FIG. 6 is a diagram showing an example of a phase difference signal input as an input signal to a vibration characteristics extraction unit according to a first embodiment. FIG. 7 is a flowchart showing an example of the operation flow of a vibration characteristics extraction unit according to a first embodiment. FIG. 8 is a flowchart showing an example of the operation flow of a dissimilarity calculation unit according to a first embodiment. FIG. 9 is a flowchart showing an example of the operation flow of a pillar position calculation unit according to a first embodiment. FIG. 10 is a diagram showing an example of a method of analyzing dissimilarity by a pillar position calculation unit according to a first embodiment. FIG. 11 is a diagram showing an example of the configuration of a sensing system assumed in a specific example of the operation of the position evaluation device according to the first embodiment. FIG. 12 is a diagram showing an example of dissimilarity obtained in a specific example of the operation of the position evaluation device according to the first embodiment. FIG. 13 is a diagram showing an application example of a position evaluation device according to a second embodiment. FIG. 14 is a diagram showing an example of the configuration of a position evaluation device according to a second embodiment. 19 is a flowchart showing an example of the flow of operation of the excess length section calculation unit according to embodiment 2. FIG. 19 is a diagram showing an example of the configuration of a sensing system assumed in a specific example of the operation of the position evaluation device according to embodiment 2. FIG. 19 is a diagram showing examples of frequency average values, dissimilarity, and weighted dissimilarity of power spectra obtained in a specific example of the operation of the position evaluation device according to embodiment 2. FIG. 19 is an enlarged view of the X region shown in FIG. 18. FIG. 19 is a diagram showing an application example of a position evaluation device according to embodiment 3. FIG. 19 is a diagram showing an example of the configuration of a position evaluation device according to embodiment 3. FIG. 20 is a flowchart showing an example of the flow of operation of the pillar position calculation unit according to embodiment 3. FIG. 20 is a diagram showing an example of an analysis target section determined by the pillar position calculation unit according to embodiment 3. FIG. 21 is a diagram showing an example of a window function configured by the pillar position calculation unit according to embodiment 3. FIG. 21 is a diagram showing an example of the relationship between the window function and the dissimilarity in a case where an appropriate offset point is determined by the pillar position calculation unit according to embodiment 3. FIG. 21 is a diagram showing an application example of the position evaluation device according to embodiment 4.FIG. 10 is a diagram showing an example of the configuration of a position evaluation device according to embodiment 4. FIG. 11 is a flowchart showing an example of the flow of operations of an excess length section calculation unit according to embodiment 4. FIG. 12 is a flowchart showing an example of the flow of operations of a pillar position calculation unit according to embodiment 4. FIG. 13 is a diagram showing an example of an analysis target section determined by a pillar position calculation unit according to embodiment 4. FIG. 14 is a diagram showing an example of the cross-correlation between a weighted dissimilarity and a window function according to embodiment 4. FIG. 15 is a diagram showing an example of a method for calculating the excess length left by a pillar position calculation unit according to embodiment 4. FIG. 16 is a diagram showing an example of the configuration of a position evaluation device according to embodiment 5. FIG. 17 is a block diagram showing an example of the hardware configuration of a computer that realizes the position evaluation device according to each embodiment.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description and drawings have been omitted and simplified as appropriate for clarity of explanation. In addition, in each of the following drawings, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary. Furthermore, specific numerical values ​​etc. shown below are merely examples to facilitate understanding of the present disclosure, and are not limited thereto.

[0024] In each embodiment of the present disclosure described below, the following (1) and / or (2) are performed. (1) Estimation of the position of the pillar suspending the optical fiber / Estimation of the aerial section of the optical fiber Specifically, the position of each pillar suspending the optical fiber is estimated on the DAS coordinate system. Also, the start and end of the aerial section of the optical fiber suspended between two pillars is estimated on the DAS coordinate system.

[0025] (2) Estimation of excess length of optical fiber Specifically, the extent of the excess length of optical fiber (optical fiber localized at a certain location in real space) is estimated on the DAS coordinate system.

[0026] Below, in each embodiment, the basic idea for performing (1) and / or (2) above will be explained. (1) Estimation of the position of the pillar suspending the optical fiber / Estimation of the aerial section of the optical fiber The movement of the optical fiber in the aerial section can be considered as the movement of a string. In each embodiment, this is used to estimate the aerial section of the optical fiber on the DAS coordinates. - For example, if the total weight of the optical fiber is large, the force suspending the optical fiber also becomes large. Therefore, the optical fiber is always subjected to a large tension, making it prone to dynamic distortion. - In addition, the optical fiber is constantly swaying due to the wind. - In addition, the transmission speed of the signal transmitted through the optical fiber is determined by the linear density (ρ), tension (T), and span length (L) of the optical fiber. ・Furthermore, optical fibers have a steady-state nth natural vibration mode (frequency f n ) vibrations are observed.

[0027] On the other hand, the position of the pillar that suspends the optical fiber is the boundary between each aerial section of the optical fiber. In each embodiment, this is utilized to estimate the position of the pillar on the DAS coordinates. For example, vibrations transmitted through the optical fiber are reflected at the pillar. Furthermore, the vibration characteristics change for each aerial section at the pillar.

[0028] (2) Estimation of Extra Optical Fiber Length Extra optical fiber lengths are often glued or fixed to a pole, making them less susceptible to dynamic distortion. Therefore, the extra optical fiber lengths are less sensitive to background noise such as wind and vibrations of the pole itself (i.e., the noise level is low). Each embodiment utilizes this fact to estimate the extra optical fiber length on the DAS coordinates. Each embodiment of the present disclosure will be described in detail below.

[0029] <First Embodiment> In the first embodiment, the position of a pillar is estimated and output as a DAS coordinate value, as shown in Fig. 4. The DAS coordinate is redefined as the length of an optical fiber measured by the DAS with a certain point as the reference.

[0030] An example of the configuration of the position evaluation device 10 according to the first embodiment will be described with reference to Fig. 5. As shown in Fig. 5, the position evaluation device 10 according to the first embodiment includes a vibration characteristics extraction unit 11, a dissimilarity calculation unit 12, and a pillar position calculation unit 13.

[0031] The vibration characteristic extraction unit 11 is connected to a DAS (not shown) and receives a phase difference signal of backscattered light obtained from the DAS as an input signal. The vibration characteristic extraction unit 11 then extracts the input signal in a certain time interval, calculates a power spectrum for the extracted input signal, and extracts and outputs a power spectrum in a frequency band including the fundamental vibration mode in the imaginary interval from the calculated power spectrum.

[0032] The dissimilarity calculation unit 12 determines an evaluation interval for evaluating the dissimilarity. Furthermore, the dissimilarity calculation unit 12 calculates and outputs the dissimilarity between the two power spectra between the evaluation intervals for all DAS coordinate points, based on the power spectra obtained by the vibration characteristic extraction unit 11.

[0033] Based on the dissimilarity at all DAS coordinate points obtained by the dissimilarity calculation unit 12, the pillar position calculation unit 13 estimates the position where the dissimilarity takes a maximum peak value as the position of the pillar, and outputs an output signal representing the DAS coordinate value corresponding to the estimated position.

[0034] The position evaluation device 10 according to the first embodiment will be described in more detail below. First, the input signal will be described. The DAS inputs pulsed light into an optical fiber and receives backscattered light (Rayleigh scattered light) from the optical fiber in response to the input pulsed light. The DAS also detects the phase difference between the backscattered light generated at two points on the optical fiber, and generates a phase difference signal indicating the detected phase difference. This phase difference signal is proportional to the dynamic strain of the optical fiber in the phase difference evaluation section (gauge length section) between the two points. The vibration characteristic extraction unit 11 receives this phase difference signal as an input signal.

[0035] The phase difference signal will be described with reference to Fig. 6. In the phase difference signal, d indicates the distance from the DAS to the measurement point in the longitudinal direction of the optical fiber, and is expressed as follows: where p is the DAS coordinate label (an integer). ADC is the frequency of the ADC (analog-digital converter) installed in the DAS. c is the speed of light in the optical fiber, expressed as c = c0 / n. c0 is the speed of light in a vacuum, and n is the refractive index of the optical fiber core (approximately 1.46 for a silica glass core). d unit is the spacing between discrete points in the spatial direction. For example, f ADC If is 125MHz, d unit is approximately 0.82 m.

[0036] Furthermore, t in the phase difference signal indicates the measurement time, and is expressed as follows: where q is the label of the time interval (an integer). Pulse is the frequency at which the DAS launches pulsed light into the optical fiber.

[0037] The gauge length is given as follows depending on the DAS settings: Here, g is an integer value. Note that the smaller the gauge length, the higher the spatial resolution of measurements possible, so a smaller gauge length is preferable.

[0038] From the above, the phase difference signal is expressed as follows: where: is a vector representing time series data in a certain DAS coordinate.

[0039] Next, an example of the flow of operations of the vibration characteristic extraction unit 11 will be described with reference to Fig. 7. As shown in Fig. 7, first, the vibration characteristic extraction unit 11 extracts an input signal in a certain time interval (step S11). The input signal in a certain time interval is the above-mentioned phase difference signal obtained from the DAS. This refers to data extracted for a desired time interval from the above. If the extracted data has N components in the time direction, the phase difference signal can be expressed as an N-dimensional vector as follows:

[0040] Next, the vibration characteristic extraction unit 11 calculates a power spectrum for the input signal extracted in step S11 (step S12). The Fourier transform is performed and the absolute value of the obtained Fourier component (power spectrum) Calculate.

[0041] Then, the vibration characteristic extraction unit 11 extracts a power spectrum of a certain frequency band from the power spectrum calculated in step S12 and outputs the extracted power spectrum to the dissimilarity calculation unit 12 (step S13). The certain frequency band is a frequency band that includes the fundamental vibration mode in the aerial section of the optical fiber. For example, if a maximum peak value of the power spectrum is observed around 40 Hz, the vibration characteristic extraction unit 11 extracts a power spectrum of a frequency band from 30 to 50 Hz.

[0042] Next, an example of the flow of operations of the dissimilarity calculation unit 12 will be described with reference to Fig. 8. As shown in Fig. 8, first, the dissimilarity calculation unit 12 determines an evaluation interval for evaluating the dissimilarity (step S21). The evaluation interval for evaluating the dissimilarity is an interval for evaluating the dissimilarity between the power spectra of two data.

[0043] Then, based on the power spectrum obtained by the vibration characteristic extraction unit 11, the dissimilarity calculation unit 12 calculates the dissimilarity between the two power spectra between the evaluation intervals determined in step S21 at all DAS coordinate points, and outputs the calculated dissimilarity to the pillar position calculation unit 13 (step S22).

[0044] Next, an example of the flow of operations of the pillar position calculation unit 13 will be described with reference to Fig. 9. As shown in Fig. 9, first, the pillar position calculation unit 13 detects the maximum peak value of the dissimilarity based on the dissimilarity at all DAS coordinate points obtained by the dissimilarity calculation unit 12 (step S31). Note that any method may be used to detect the maximum peak value. Furthermore, the number of maximum peak values ​​to be detected may be determined, for example, depending on the number of pillars whose positions are to be estimated.

[0045] Thereafter, the pillar position calculation unit 13 estimates the position of the maximum peak value detected in step S31 as the position of the pillar, extracts the DAS coordinate value corresponding to the estimated position, and outputs an output signal representing the extracted DAS coordinate value (step S32).

[0046] Next, an example of a method for analyzing the dissimilarity by the pillar position calculation unit 13 will be described with reference to FIG. 10. Here, the dissimilarity calculation unit 12 calculates a power spectrum and the power spectrum The dissimilarity D(p) between and is calculated as follows: Here, a is the evaluation interval of the dissimilarity.

[0047] for example, and, If both and are power spectra of the fictitious part and do not cross a pillar, the power spectra of both are similar, and D(p) takes a value close to 0.

[0048] on the other hand, and, When and span the imaginary part and the pillar, the similarity of the power spectra of the two becomes small, and D(p) takes a value close to 1.

[0049] Therefore, the pillar position calculation unit 13 analyzes the dissimilarity from the above perspective. Fig. 10 shows an example where the evaluation interval a is 1. In the example of Fig. 10, the pillar position calculation unit 13 estimates the position of p = N where D(p) is closest to 1, that is, the position of p = N where the dissimilarity takes the maximum peak value, as the position of the pillar, and outputs the DAS coordinate value corresponding to the estimated position.

[0050] Next, a specific example of the operation of the position evaluation device 10 according to the first embodiment will be described. In this specific example, as shown in Fig. 11, a sensing system is assumed in which an approximately 30 m optical fiber is suspended from a pole and a DAS is connected to the left end of the optical fiber. Under this assumption, in this specific example, the left part of the overhead section of the optical cable is set to 0 m in terms of DAS coordinate value (length of optical fiber), and the DAS coordinate value of the pole position is estimated.

[0051] First, the vibration characteristic extraction unit 11 extracts the power spectrum of the frequency band from 0 to 50 Hz for the input signal for 10 seconds. unit = 0.82m, g = 2. Next, the dissimilarity calculation unit 12 calculates the dissimilarity using these power spectra. Here, a = 1 is set.

[0052] As a result, the dissimilarity shown in Fig. 12 is obtained. In this case, the pillar position calculation unit 13 estimates the position where the dissimilarity takes the maximum peak as the position of the pillar, and outputs a DAS coordinate value of 15.2 m corresponding to the estimated position.

[0053] As described above, according to the first embodiment, the vibration characteristic extraction unit 11 receives a phase difference signal of backscattered light as an input signal, extracts the input signal in a certain time interval, calculates a power spectrum for the extracted input signal, and extracts a power spectrum in a certain frequency band from the calculated power spectrum. The dissimilarity calculation unit 12 calculates the dissimilarity between two power spectra between evaluation intervals for all DAS coordinate points. The pillar position calculation unit 13 estimates the position where the dissimilarity takes a maximum peak value as the position of the pillar, and extracts and outputs the DAS coordinate value corresponding to the estimated position.

[0054] Therefore, even if the point is not the point where the strongest vibration occurs, as long as the difference in the power spectrum between evaluation intervals is maximized, the point can be estimated as the position of the pillar. This makes it possible to improve the accuracy of estimating the position of the pillar, which is the position where the optical fiber environment changes.

[0055] <Embodiment 2> In this embodiment 2, the position of an excess length section of optical fiber is estimated and output as a DAS coordinate value, as shown in Fig. 13. Specifically, the left and right ends of the excess length of optical fiber are expressed as the excess length left and the excess length right, respectively, and the DAS coordinate values ​​of the positions of the excess length left and the excess length right are estimated and output.

[0056] An example of the configuration of the position evaluation device 20 according to the second embodiment will be described with reference to Fig. 14. As shown in Fig. 14, the position evaluation device 20 according to the second embodiment includes a vibration characteristics extraction unit 21, a weighted dissimilarity calculation unit 22, and a marginal length calculation unit 23.

[0057] The input signal input to the vibration characteristic extraction unit 21 is the same as the input signal according to the above-described embodiment 1. The vibration characteristic extraction unit 21 is the same as the vibration characteristic extraction unit 11 according to the above-described embodiment 1.

[0058] The weighted dissimilarity calculation unit 22 calculates the frequency average value of the power spectrum at all DAS coordinate points based on the power spectrum obtained by the vibration characteristic extraction unit 21. The weighted dissimilarity calculation unit 22 also determines an evaluation interval for evaluating the dissimilarity. The weighted dissimilarity calculation unit 22 also calculates the dissimilarity between two power spectra between evaluation intervals at all DAS coordinate points based on the power spectrum obtained by the vibration characteristic extraction unit 21. The weighted dissimilarity calculation unit 22 also calculates and outputs weighted dissimilarity at all DAS coordinate points, in which the dissimilarity is weighted by the frequency average value of the power spectrum, based on the obtained dissimilarity at all DAS coordinate points and the frequency average value of the power spectrum. The weighted dissimilarity calculation unit 22 also outputs the frequency average value of the power spectrum at all DAS coordinate points.

[0059] The excess section calculation unit 23 sets an excess section range on the DAS coordinates based on the average frequency values ​​of the power spectrum at all DAS coordinate points obtained by the weighted difference calculation unit 22. Furthermore, based on the weighted differences at all DAS coordinate points obtained by the weighted difference calculation unit 22, the excess section calculation unit 23 estimates positions within the set excess section range where the weighted difference takes a maximum peak value as the left and right excess section positions, extracts DAS coordinate values ​​corresponding to the estimated positions, and outputs output signals representing the extracted DAS coordinate values.

[0060] The position evaluation device 20 according to the second embodiment will be described in more detail below. First, an example of the flow of operations of the weighted dissimilarity calculation unit 22 will be described with reference to Fig. 15. As shown in Fig. 15, first, the weighted dissimilarity calculation unit 22 calculates the frequency average value of the power spectrum at all DAS coordinate points based on the power spectrum obtained by the vibration characteristics extraction unit 21 (step S41).

[0061] Next, the weighted dissimilarity calculation unit 22 determines an evaluation interval for evaluating the dissimilarity (step S42). Next, the weighted dissimilarity calculation unit 22 calculates the dissimilarity between the two power spectra between the evaluation intervals determined in step S42 for all DAS coordinate points, based on the power spectra obtained by the vibration characteristic extraction unit 21 (step S43).

[0062] Thereafter, the weighted dissimilarity calculation unit 22 calculates weighted dissimilarity for all DAS coordinate points based on the average frequency value of the power spectrum and the dissimilarity at all DAS coordinate points obtained in steps S41 and S43, and outputs the calculated weighted dissimilarity to the extra length interval calculation unit 23. The weighted dissimilarity is obtained by weighting the dissimilarity by the average frequency value of the power spectrum and is obtained by multiplying the average frequency value of the power spectrum by the dissimilarity. The weighted dissimilarity can characterize the state of points where the dissimilarity is high and the vibration intensity is small. Furthermore, the weighted dissimilarity calculation unit 22 outputs the average frequency value of the power spectrum for all DAS coordinate points obtained in step S41 to the extra length interval calculation unit 23 (step S44).

[0063] Next, an example of the flow of operations of the extra length section calculation unit 23 will be described with reference to Fig. 16. As shown in Fig. 16, first, the extra length section calculation unit 23 sets an extra length section range on the DAS coordinates based on the frequency average value of the power spectrum at all DAS coordinate points obtained by the weighted dissimilarity calculation unit 22 (step S51). Specifically, the extra length section calculation unit 23 sets the range on the DAS coordinates where the frequency average value of the power spectrum is below a threshold as the extra length section range. This sets a rough range that can be considered as an extra length section of the optical fiber. Note that the threshold is a percentile value with respect to the frequency average value of the power spectrum.

[0064] Thereafter, the excess length section calculation unit 23 estimates, within the excess length section range set in step S51, positions where the weighted dissimilarity takes a maximum peak value as the left and right excess length positions of the optical fiber, based on the weighted dissimilarity at all DAS coordinate points obtained by the weighted dissimilarity calculation unit 22. The excess length section calculation unit 23 then extracts DAS coordinate values ​​corresponding to the estimated positions as the left and right excess length positions, and outputs output signals representing the extracted DAS coordinate values ​​(step S52).

[0065] Next, a specific example of the operation of the position evaluation device 20 according to the second embodiment will be described. In this specific example, as shown in Fig. 17, a sensing system is assumed in which three pillars contain an extra length section of optical fiber of approximately 50 m, approximately 30 m of optical fiber is suspended between each of the three pillars, and a DAS is connected to the left end of the optical fiber. Therefore, the total length of the optical fiber is approximately 210 m.

[0066] Based on this assumption, in this specific example, the left portion of the excess optical fiber included in the left-hand pole of the three poles mentioned above is set to 0 m in DAS coordinate value (optical fiber length), and the DAS coordinate values ​​of the left and right positions of the excess optical fiber included in the central pole (approximately 80 m to 130 m in DAS coordinate value) are estimated.

[0067] First, the vibration characteristic extraction unit 21 extracts the power spectrum of the frequency band from 0 to 50 Hz for the input signal for 10 seconds. unit= 0.82m, g = 2. Next, the weighted dissimilarity calculation unit 22 uses these power spectra to calculate the average frequency values, dissimilarity, and weighted dissimilarity of the power spectra at all DAS coordinate points. Here, a = 2 is set.

[0068] As a result, it is assumed that the frequency average values, dissimilarity, and weighted dissimilarity of the power spectrum are obtained as shown in Figures 18 and 19. Note that Figure 19 is an enlarged view of the X region shown in Figure 18.

[0069] Here, the extra length section of optical fiber is hardly affected by wind, so the frequency average value of the power spectrum of the extra length section is small. Therefore, the extra length section calculation unit 23 first sets the range on the DAS coordinates where the frequency average value of the power spectrum is below a threshold as the extra length section range, which is a rough range that can be considered as an extra length section of optical fiber. Here, the threshold is set to the 70th percentile.

[0070] On the other hand, at the position where the optical fiber changes from the slack section to the overhead section, the vibration applied to the optical fiber changes, and the characteristics of the backscattered light change, so the dissimilarity increases. At this time, the weighted dissimilarity, which is obtained by weighting the dissimilarity with the frequency average value of the power spectrum, shows maximum peaks at the left and right parts of the slack section of the optical fiber.

[0071] Therefore, the excess length section calculation unit 23 next estimates the positions within the excess length section range where the weighted difference takes the maximum peak value as the left and right positions of the excess length of the optical fiber, and outputs DAS coordinate values ​​of 80.36 m and 129.2 m corresponding to the estimated positions.

[0072] As described above, according to the second embodiment, the vibration characteristic extraction unit 21 receives a phase difference signal of backscattered light as an input signal, extracts the input signal in a certain time interval, calculates a power spectrum for the extracted input signal, and extracts a power spectrum in a certain frequency band from the calculated power spectrum. The weighted difference calculation unit 22 calculates the frequency average value of the power spectrum at all DAS coordinate points, calculates the dissimilarity between two power spectra between evaluation intervals, and calculates a weighted dissimilarity by weighting the dissimilarity by the frequency average value of the power spectrum. The extra length section calculation unit 23 sets an extra length section range on the DAS coordinates, estimates positions within the set extra length section range where the weighted dissimilarity takes a maximum peak value as the left and right positions of the extra length of the optical fiber, and extracts and outputs DAS coordinate values ​​corresponding to the estimated positions.

[0073] Therefore, even if the points are not the points where the strongest vibration occurs, as long as the weighted difference in the power spectrum between evaluation intervals is maximized, the points can be estimated as the left and right positions of the excess length of the optical fiber. This makes it possible to improve the accuracy of estimating the positions of the excess length sections, which are the positions of the optical fiber where the environment changes.

[0074] <Third embodiment> In this third embodiment, as shown in Fig. 20, the position of a pillar is estimated and output as a DAS coordinate value by referring to the pillar distance given in advance. The pillar distance indicates the distance between adjacent pillars, and is assumed to be given in advance from the following information, for example: Positioning of the pillar distance by referring to GPS (Global Positioning System) information or map information Optical fiber length recorded when the optical fiber is installed between two pillars

[0075] An example of the configuration of a position evaluation device 30 according to the third embodiment will be described with reference to Fig. 21. As shown in Fig. 21, the position evaluation device 30 according to the third embodiment includes a vibration characteristics extraction unit 31, a dissimilarity calculation unit 32, and a pillar position calculation unit 33.

[0076] The input signal input to the vibration characteristic extraction unit 31 is similar to the input signal according to the above-described embodiments 1 and 2. The vibration characteristic extraction unit 31 is similar to the vibration characteristic extraction units 11 and 21 according to the above-described embodiments 1 and 2. The dissimilarity calculation unit 32 is similar to the dissimilarity calculation unit 12 according to the above-described embodiment 1.

[0077] The pillar position calculation unit 33 determines the section including all pillars whose positions are to be estimated as the analysis section. The pillar position calculation unit 33 also constructs a window function for the analysis section based on the pre-given inter-pillar distance. The pillar position calculation unit 33 also searches for a DAS coordinate value (offset point) at which the value of the cross-correlation function between the window function and the dissimilarity is maximized, based on the dissimilarity at all DAS coordinate points obtained by the dissimilarity calculation unit 32 and the window function constructed above. The pillar position calculation unit 33 also outputs the position of each pillar as a DAS coordinate value based on the pre-given inter-pillar distance and the offset point searched above. Specifically, the pillar position calculation unit 33 estimates the position of each pillar as the position of the offset point and the position obtained by adding the offset point to the inter-pillar distance, and outputs a DAS coordinate value corresponding to the estimated position.

[0078] The position evaluation device 30 according to the third embodiment will be described in more detail below. First, an example of the flow of operations of the pillar position calculation unit 33 will be described with reference to Fig. 22. As shown in Fig. 22, the pillar position calculation unit 33 first determines an analysis target section (step S61). The analysis target section is a section of DAS coordinates that includes all pillars whose positions are to be estimated.

[0079] Next, the pillar position calculation unit 33 constructs a window function for the analysis section based on the pre-given inter-pillar distance (step S62). The window function will be described in detail later. Next, the pillar position calculation unit 33 searches for a DAS coordinate value (offset point) in the analysis section at which the value of the cross-correlation function between the window function and the dissimilarity is maximum, based on the dissimilarity at all DAS coordinate points obtained by the dissimilarity calculation unit 32 and the window function constructed in step S62 (step S63).

[0080] Thereafter, the pillar position calculation unit 33 adds the inter-pillar distance to the offset point based on the pre-given inter-pillar distance and the offset point searched for in step S63, thereby outputting the position of each pillar as a DAS coordinate value (step S64). Specifically, the pillar position calculation unit 33 estimates the position of each pillar as the position of the offset point and the position obtained by adding the inter-pillar distance to the offset point, and outputs DAS coordinate values ​​corresponding to the estimated positions.

[0081] Next, an example of an analysis target section determined by the pillar position calculation unit 33 will be described with reference to Fig. 23. As shown in Fig. 23, the pillar position calculation unit 33 sets a label for each pillar and determines the analysis target section. As described above, the analysis target section is a section of DAS coordinates that includes all pillars whose positions are to be estimated (here, pillars 0 to N).

[0082] Here, the distances between pillars according to the labels of each pillar are defined as d1, d2, .... The DAS coordinate value from the DAS to the left end of the analysis section (point p = 0) is set as d0. This DAS coordinate value can be set to any value so as to include pillar 0.

[0083] Next, an example of a window function configured by the pillar position calculation unit 33 will be described with reference to Fig. 24. As shown in Fig. 24, the window function is configured as follows from inter-pillar distances p1, p2, .... Also, the window width p l can be set appropriately as a value of about a. In addition, in order to improve the accuracy of the analysis results, the window width p l The analysis may be performed while changing the value of

[0084] Next, a description will be given of an example of the cross-correlation function calculated by the pillar position calculation unit 33. In the analysis target section, the cross-correlation function between the window function W(p) and the dissimilarity D(p) is given as follows: Here, the dissimilarity D(p) becomes large near the position of the pillar. Therefore, the pillar position calculation unit 33 calculates the DAS coordinate value (offset point) p where the value of the cross-correlation function is maximum in the analysis target section. offset The pillar position calculation unit 33 searches for the offset point p offsetAfter determining the coordinates, the following DAS coordinate values ​​representing the position of each pillar N' are output.

[0085] FIG. 25 shows the calculation of the appropriate offset point p offset 25 shows an example of the relationship between the window function and the dissimilarity when the offset point p offset is the DAS coordinate value of column 0, and the distance between columns given in advance is the offset point p offset The values ​​added together become the DAS coordinate values ​​of pillars 1 to N, respectively.

[0086] As described above, according to the third embodiment, the vibration characteristic extraction unit 31 receives a phase difference signal of backscattered light as an input signal, extracts the input signal in a certain time interval, calculates a power spectrum for the extracted input signal, and extracts a power spectrum in a certain frequency band from the calculated power spectrum. The dissimilarity calculation unit 32 calculates the dissimilarity between two power spectra between evaluation intervals at all DAS coordinate points. The pillar position calculation unit 33 determines the analysis interval and configures a window function for the analysis interval based on a predetermined pillar-to-pillar distance. The pillar position calculation unit 33 also searches for a DAS coordinate value (offset point) at which the cross-correlation function between the window function and the dissimilarity takes the maximum value, and adds the predetermined pillar-to-pillar distance to the offset point to output a DAS coordinate value corresponding to the position of each pillar. That is, the pillar position calculation unit 33 estimates the position of each pillar by combining the position of the offset point and the position obtained by adding the offset point to the pillar-to-pillar distance, and outputs a DAS coordinate value corresponding to the estimated position.

[0087] Therefore, it is possible to estimate the position of each pillar even at points other than the point where the strongest vibration occurs. This makes it possible to improve the accuracy of estimating the position of each pillar, which is the position where the optical fiber's environment changes. It also makes it possible to estimate the position of each pillar simultaneously.

[0088] <Embodiment 4> In this embodiment 4, as shown in FIG. 26, when the pillars containing the excess length section of the optical fiber are known, the position of each pillar and the position of the excess length section are estimated and output as DAS coordinate values ​​by referring to the distance between pillars given in advance.

[0089] An example of the configuration of a position evaluation device 40 according to the fourth embodiment will be described with reference to Fig. 27. As shown in Fig. 27, the position evaluation device 40 according to the fourth embodiment includes a vibration characteristics extraction unit 41, a weighted dissimilarity calculation unit 42, a marginal length calculation unit 43, and a pillar position calculation unit 44.

[0090] The input signal input to the vibration characteristic extraction unit 41 is similar to the input signal according to the above-described first, second, and third embodiments. The vibration characteristic extraction unit 41 is similar to the vibration characteristic extraction units 11, 21, and 31 according to the above-described first, second, and third embodiments. The weighted difference calculation unit 42 is similar to the weighted difference calculation unit 22 according to the above-described second embodiment.

[0091] The extra length section calculation unit 43 sets an extra length section range on the DAS coordinates based on the average frequency values ​​of the power spectrum at all DAS coordinate points obtained by the weighted dissimilarity calculation unit 42 .

[0092] The pillar position calculation unit 44 determines the section from a pillar including an extra length section to the next pillar including an extra length section as the analysis section. The pillar position calculation unit 44 also constructs a window function for the analysis section based on a pre-given inter-pillar distance. The pillar position calculation unit 44 also searches for a DAS coordinate value (offset point) at which the value of the cross-correlation function between the window function and the weighted dissimilarity is maximized based on the weighted dissimilarity at all DAS coordinate points obtained by the weighted dissimilarity calculation unit 42 and the window function constructed above. The pillar position calculation unit 44 also outputs DAS coordinate values ​​corresponding to the position of each pillar based on the pre-given inter-pillar distance and the offset point searched above. That is, the pillar position calculation unit 44 estimates the position of each pillar as the position of the offset point and the position obtained by adding the offset point to the inter-pillar distance, and outputs DAS coordinate values ​​corresponding to the estimated position.

[0093] Furthermore, the pole position calculation unit 44 outputs a DAS coordinate value corresponding to the position to the right of the excess length of optical fiber based on the offset point searched for as described above. That is, the pole position calculation unit 44 estimates the position of the offset point as the position to the right of the excess length and outputs a DAS coordinate value corresponding to the estimated position. Also, the pole position calculation unit 44 outputs a DAS coordinate value corresponding to the position to the left of the excess length of optical fiber based on the weighted dissimilarity of each position on the DAS side of the pole position including the excess length section. That is, the pole position calculation unit 44 estimates the position where the weighted dissimilarity takes a maximum peak value on the DAS side of the pole position including the excess length section as the position to the left of the excess length and outputs a DAS coordinate value corresponding to the estimated position.

[0094] The position evaluation device 40 according to the fourth embodiment will be described in more detail below. First, an example of the flow of operations of the extra length section calculation unit 43 will be described with reference to FIG. 28 . As shown in FIG. 28 , the extra length section calculation unit 43 sets an extra length section range on the DAS coordinates based on the frequency average value of the power spectrum at all DAS coordinate points obtained by the weighted dissimilarity calculation unit 42 (step S71). Specifically, the extra length section calculation unit 43 sets the range on the DAS coordinates where the frequency average value of the power spectrum is below a threshold as the extra length section range. This sets an extra length section range, which is a rough range that can be considered as an extra length section of optical fiber. Note that the threshold is a percentile value of the frequency average value of the power spectrum. Furthermore, the number of extra length section ranges is equal to the number of pillars that include extra length sections.

[0095] Next, an example of the flow of operations of the pillar position calculation unit 44 will be described with reference to Fig. 29. As shown in Fig. 29, first, the pillar position calculation unit 44 determines an analysis target section (step S81). The analysis target section is a section of DAS coordinates from a pillar including an extra length section to the next pillar including an extra length section.

[0096] Next, the pillar position calculation unit 44 constructs a window function for the analysis section based on the distance between pillars given in advance (step S82). The window function is the same as the window function according to the third embodiment described above.

[0097] Next, the pillar position calculation unit 44 searches for the DAS coordinate value (offset point) in the analysis section where the value of the cross-correlation function between the window function and the weighted dissimilarity is maximum, based on the weighted dissimilarity at all DAS coordinate points obtained by the weighted dissimilarity calculation unit 42 and the window function constructed in step S82 (step S83).

[0098] Next, the pillar position calculation unit 44 adds the offset points to the inter-pillar distance based on the pre-given inter-pillar distance and the offset points searched for in step S83, and outputs DAS coordinate values ​​corresponding to the position of each pillar (step S84). That is, the pillar position calculation unit 44 estimates the positions of the offset points and the positions obtained by adding the inter-pillar distance to the offset points as the positions of each pillar, and outputs DAS coordinate values ​​corresponding to the estimated positions.

[0099] Next, the pole position calculation unit 44 outputs the DAS coordinate value of the offset point found in step S83 as the DAS coordinate value corresponding to the position to the right of the excess length of the optical fiber (step S85). That is, the pole position calculation unit 44 estimates the position of the offset point as the position to the right of the excess length, and outputs the DAS coordinate value corresponding to the estimated position.

[0100] Thereafter, the pole position calculation unit 44 outputs the DAS coordinate value corresponding to the position where the weighted dissimilarity takes a maximum peak value based on the weighted dissimilarity of each position on the DAS side of the pole position including the excess length section, as the DAS coordinate value corresponding to the position to the left of the excess length of the optical fiber (step S86). That is, the pole position calculation unit 44 estimates the position where the weighted dissimilarity takes a maximum peak value on the DAS side of the pole position including the excess length section as the position to the left of the excess length, and outputs the DAS coordinate value corresponding to the estimated position.

[0101] Next, an example of an analysis target section determined by the pillar position calculation unit 44 will be described with reference to Fig. 30. As shown in Fig. 30, the pillar position calculation unit 44 sets a label for each pillar and determines the analysis target section. As described above, the analysis target section is a section of DAS coordinates from a pillar including an extra length section to the next pillar including an extra length section.

[0102] 30, column 0 includes an excess length section, and the next column that includes an excess length section is column N+1. Therefore, the column position calculation unit 44 determines the section from column 0 to column N immediately before column N+1 as analysis section 1, and determines the section from column N+1 onwards as analysis section 2.

[0103] Here, the distances between pillars according to the labels of each pillar are defined as d1, d2, .... The DAS coordinate value from the DAS to the left end of the analysis section (point p = 0) is set as d0. This DAS coordinate value can be set to any value so as to include pillar 0.

[0104] Next, an example of the cross-correlation between the weighted dissimilarity and the window function will be described with reference to Fig. 31. As described above, the weighted dissimilarity is obtained by weighting the dissimilarity by the average frequency value of the power spectrum, and is obtained by multiplying the average frequency value of the power spectrum by the dissimilarity.

[0105] As shown in Figure 31, when the window function is configured based on the right excess length, the value of the cross-correlation function between the weighted dissimilarity and the window function is larger than when the window function is configured based on the left excess length. Therefore, the column position calculation unit 44 configures the window function based on the right excess length. Then, the column position calculation unit 44 calculates the DAS coordinate value (offset point) p where the value of the cross-correlation function is maximum. offset The DAS coordinate value of the offset point corresponds to the position to the right of the excess length of the optical fiber. Thereafter, the pole position calculation unit 44 estimates the DAS coordinate value of the position of each pole, in the same manner as in the third embodiment described above.

[0106] Next, an example of a method for calculating the left excess length by the pole position calculation unit 44 will be described with reference to Fig. 32. As shown in Fig. 32, the pole position calculation unit 44 estimates the DAS coordinate value at which the weighted dissimilarity takes the maximum peak value, among the DAS coordinate values ​​of each position on the DAS side of the pole position including the excess length section, as the DAS coordinate value corresponding to the position of the left excess length of the optical fiber.

[0107] As mentioned above, the offset value p offset The DAS coordinate value of p corresponds to the position to the right of the excess length of the optical fiber. Therefore, in the example of FIG. 32, the pole position calculation unit 44 calculates the DAS coordinate value of p as follows: 0<p<p offsetAmong the DAS coordinate values, the DAS coordinate value with the maximum weighted dissimilarity is estimated as the DAS coordinate value corresponding to the left position of the excess length of the optical fiber.

[0108] As described above, according to the fourth embodiment, the vibration characteristic extraction unit 41 receives a phase difference signal of backscattered light as an input signal, extracts the input signal in a certain time interval, calculates a power spectrum for the extracted input signal, and extracts a power spectrum in a certain frequency band from the calculated power spectrum. The weighted dissimilarity calculation unit 42 calculates the frequency average value of the power spectrum at all DAS coordinate points, calculates the dissimilarity between two power spectra between evaluation intervals, and calculates a weighted dissimilarity by weighting the dissimilarity by the frequency average value of the power spectrum. The marginal interval calculation unit 43 sets the marginal interval range on the DAS coordinate. The pillar position calculation unit 44 determines the analysis target interval and configures a window function for the analysis target interval based on a predetermined pillar-to-pillar distance. The pillar position calculation unit 44 also searches for a DAS coordinate value (offset point) at which the value of the cross-correlation function between the window function and the weighted dissimilarity takes the maximum value, and outputs a DAS coordinate value corresponding to the position of each pillar by adding the predetermined pillar-to-pillar distance to the offset point. The pole position calculation unit 44 also outputs the offset point as the DAS coordinate value of the right side of the excess length of optical fiber. The pole position calculation unit 44 also outputs, among the DAS coordinate values ​​of each position on the DAS side of the right side of the excess length, the DAS coordinate value at which the weighted dissimilarity takes a maximum peak value as the DAS coordinate value of the left side of the excess length of optical fiber. That is, the pole position calculation unit 44 estimates the position of the offset point and the position obtained by adding the offset point to the distance between poles as the position of each pole, estimates the position of the offset point as the position of the right side of the excess length, and estimates the position at which the weighted dissimilarity takes a maximum peak value on the DAS side of the position of the pole including the excess length section as the position of the left side of the excess length. The pole position calculation unit 44 then outputs DAS coordinate values ​​corresponding to the estimated positions of each pole, the right side of the excess length, and the left side of the excess length.

[0109] Therefore, points other than the point where the strongest vibration occurs can be estimated as the position of each pillar or the position of the extra length of optical fiber. This makes it possible to improve the accuracy of estimating the position of each pillar or the position of the extra length of optical fiber, which are the positions where the optical fiber's environment changes. It also makes it possible to estimate the position of each pillar simultaneously.

[0110] <Fifth Embodiment> This fifth embodiment corresponds to an embodiment that is a broader concept than the above-described first to fourth embodiments. An example of the configuration of a position evaluation device 50 according to this fifth embodiment will be described with reference to Fig. 33. As shown in Fig. 33, the position evaluation device 50 according to this fifth embodiment includes a vibration characteristics calculation unit 51, a dissimilarity calculation unit 52, and an environment change position estimation unit 53.

[0111] The vibration characteristic calculation unit 51 receives a signal indicating the natural vibration occurring at each position of the optical fiber from the sensor, and calculates sensing data indicating the vibration characteristic at each position of the optical fiber based on the received signal. The vibration characteristic calculation unit 51 corresponds to the vibration characteristic extraction units 11, 21, 31, and 41 according to the above-described first, second, third, and fourth embodiments. The sensor corresponds to a phase-sensing OTDR or a DAS.

[0112] The dissimilarity calculation unit 52 calculates the dissimilarity of sensing data between two adjacent points on the optical fiber. The dissimilarity calculation unit 52 corresponds to the dissimilarity calculation units 12 and 32 according to the first and third embodiments and the weighted dissimilarity calculation units 22 and 42 according to the second and fourth embodiments.

[0113] The environmental change position estimating unit 53 estimates the environmental change position where the optical fiber environment changes based on the degree of difference. The environmental change position estimating unit 53 corresponds to the pole position calculating units 13, 33, 44 according to the first, third, and fourth embodiments described above and the excess length section calculating units 23, 43 according to the second and fourth embodiments described above.

[0114] Since the fifth embodiment is configured as described above, it is possible to estimate a point other than the point where the maximum vibration occurs as the environmental change position where the environment of the optical fiber changes, thereby improving the accuracy of estimating the environmental change position of the optical fiber.

[0115] The optical fiber may be an optical fiber suspended from a pillar. In this case, the vibration characteristic calculation unit 51 may calculate a power spectrum in a predetermined frequency band as sensing data. Furthermore, the dissimilarity calculation unit 52 may calculate the dissimilarity of the power spectrum between two adjacent points on the optical fiber. Furthermore, the environment change position estimation unit 53 may estimate the position where the dissimilarity takes a maximum peak value as the position of the pillar suspending the optical fiber.

[0116] Alternatively, the vibration characteristic calculation unit 51 may calculate a power spectrum in a predetermined frequency band as the sensing data. Furthermore, the dissimilarity calculation unit 52 may calculate the dissimilarity of the power spectrum between two adjacent points on the optical fiber, and may also calculate a weighted dissimilarity by weighting the calculated dissimilarity by the frequency average value of the power spectrum. Furthermore, the environmental change position estimation unit 53 may set the range in which the frequency average value of the power spectrum is below a threshold as the range of the excess length section of the optical fiber, and estimate positions within the range of the excess length section where the weighted dissimilarity takes a maximum peak value as the left and right ends of the excess length section.

[0117] Alternatively, the vibration characteristic calculation unit 51 may calculate a power spectrum in a predetermined frequency band as sensing data. Furthermore, the dissimilarity calculation unit 52 may calculate the dissimilarity of power spectra between two adjacent points on the optical fiber. Furthermore, the environmental change position estimation unit 53 may determine an analysis target section that includes all pillars whose positions are to be estimated, configure a window function based on a pre-given inter-pillar distance indicating the distance between adjacent pillars in the analysis target section, search for an offset point where the correlation function between the window function and the dissimilarity takes a maximum value, and estimate the position of the offset point and the position obtained by adding the offset point to the inter-pillar distance as the position of the pillar suspending the optical fiber.

[0118] Alternatively, the vibration characteristic calculation unit 51 may calculate a power spectrum in a predetermined frequency band as the sensing data. The dissimilarity calculation unit 52 may calculate the dissimilarity of the power spectrum between two adjacent points on the optical fiber and calculate a weighted dissimilarity by weighting the calculated dissimilarity by the frequency average value of the power spectrum. The environmental change position estimation unit 53 may determine an analysis target section from a pillar including an extra length section of the optical fiber to the next pillar including the extra length section, configure a window function based on a predetermined pillar-to-pillar distance indicating the distance between adjacent pillars in the analysis target section, search for an offset point where the correlation function between the window function and the weighted dissimilarity takes a maximum value, estimate the position of the offset point and a position obtained by adding the offset point to the pillar-to-pillar distance as the positions of the pillars suspending the optical fiber, and estimate the position of the offset point and positions on the sensor side of the offset point where the weighted dissimilarity takes a maximum peak value as the left and right ends of the extra length section.

[0119] In this way, in the case of an optical fiber suspended from a pole, the environmental change position of the optical fiber estimated in this fifth embodiment is, for example, the position of the pole suspending the optical fiber and the excess length section of the optical fiber.

[0120] However, the environmental change position of the optical fiber estimated in this fifth embodiment is not limited to this. This fifth embodiment may also be used to estimate the position of a boundary point where physical properties change significantly (for example, a fixed point of the optical fiber) as the environmental change position. For example, an optical fiber included in an optical submarine cable has a boundary point between a section buried in the seabed and a section exposed in the sea and swaying due to waves. This fifth embodiment may also be used to estimate the position of such a boundary point as the environmental change position.

[0121] <Hardware Configuration of Position Evaluation Apparatus According to the Embodiments> An example of the hardware configuration of a computer 90 that realizes the position evaluation apparatuses 10, 20, 30, 40, and 50 according to the first, second, third, fourth, and fifth embodiments will be described with reference to FIG.

[0122] 34, a computer 90 includes a processor 91, a memory 92, a storage 93, an input / output interface (input / output I / F) 94, and a communication interface (communication I / F) 95. The processor 91, the memory 92, the storage 93, the input / output interface 94, and the communication interface 95 are connected by a data transmission path for transmitting and receiving data to and from each other.

[0123] The processor 91 is, for example, a central processing unit (CPU) or a graphics processing unit (GPU). The memory 92 is, for example, a random access memory (RAM) or a read-only memory (ROM). The storage 93 is, for example, a storage device such as a hard disk drive (HDD), a solid state drive (SSD), or a memory card. The storage 93 may also be a memory such as a RAM or a ROM.

[0124] A program is stored in the storage 93. When the program is loaded into the computer, it includes a set of instructions (or software code) that causes the computer 90 to perform one or more functions of the above-described position evaluation devices 10, 20, 30, 40, and 50. The components of the above-described position evaluation devices 10, 20, 30, 40, and 50 may be realized by the processor 91 reading and executing the program stored in the storage 93. Furthermore, the storage function of the above-described position evaluation devices 10, 20, 30, 40, and 50 may be realized by the memory 92 or the storage 93.

[0125] The above-described programs may also be stored on non-transitory computer-readable media or tangible storage media. By way of example and not limitation, computer-readable media or tangible storage media include RAM, ROM, flash memory, SSD or other memory technologies, CD (Compact Disc)-ROM, DVD (Digital Versatile Disc), Blu-ray® disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0126] The input / output interface 94 is connected to a display device 941, an input device 942, a sound output device 943, etc. The display device 941 is a device that displays a screen corresponding to drawing data processed by the processor 91, such as an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube) display, or a monitor. The input device 942 is a device that accepts operation inputs from an operator, such as a keyboard, a mouse, or a touch sensor. The display device 941 and the input device 942 may be integrated and realized as a touch panel. The sound output device 943 is a device that outputs sound corresponding to the sound data processed by the processor 91, such as a speaker.

[0127] The communication interface 95 transmits and receives data to and from an external device. For example, the communication interface 95 communicates with the external device via a wired communication path or a wireless communication path.

[0128] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. For example, some or all of the above-described embodiments may be used in combination with each other.

[0129] Furthermore, some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes. (Supplementary Note 1) A position evaluation device comprising: a vibration characteristic calculation unit that receives, from a sensor, a signal indicating a natural vibration occurring at each position of an optical fiber, and calculates sensing data indicating vibration characteristics at each position of the optical fiber based on the received signal; a dissimilarity calculation unit that calculates a degree of difference in the sensing data between two adjacent points of the optical fiber; and an environment change position estimation unit that estimates an environment change position at which the environment of the optical fiber changes based on the degree of difference. (Supplementary Note 2) The position evaluation device according to Supplementary Note 1, wherein the optical fiber is an optical fiber attached to a pole, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates a degree of difference in the power spectrum between two adjacent points of the optical fiber, and the environment change position estimation unit estimates a position at which the degree of difference takes a maximum peak value as the position of a pole suspending the optical fiber. (Supplementary Note 3) The position evaluation device according to Supplementary Note 1, wherein the optical fiber is an optical fiber suspended above a pole, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates the dissimilarity of the power spectrum between two adjacent points of the optical fiber, and calculates a weighted dissimilarity by weighting the calculated dissimilarity by a frequency average value of the power spectrum, and the environmental change position estimation unit sets a range in which the frequency average value of the power spectrum is below a threshold as a range of a spare length section of the optical fiber, and estimates positions within the range of the spare length section where the weighted dissimilarity takes a maximum peak value to be the left and right ends of the spare length section.(Supplementary Note 4) The position evaluation device according to Supplementary Note 1, wherein the optical fiber is an optical fiber suspended above a pillar, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates the dissimilarity of the power spectrum between two adjacent points of the optical fiber, and the environmental change position estimation unit determines an analysis target section that includes all pillars whose positions are to be estimated, configures a window function in the analysis target section based on a pillar-to-pillar distance that indicates the distance between adjacent pillars that is given in advance, searches for an offset point in the analysis target section where a correlation function between the window function and the dissimilarity takes a maximum value, and estimates, in the analysis target section, the position of the offset point and the position obtained by adding the offset point to the pillar-to-pillar distance as the position of the pillar suspending the optical fiber. (Supplementary Note 5) The optical fiber is an optical fiber suspended on a pillar, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates a dissimilarity of the power spectrum between two adjacent points of the optical fiber, and calculates a weighted dissimilarity by weighting the calculated dissimilarity by a frequency average value of the power spectrum, the environment change position estimation unit determines an analysis target section from a pillar including an extra length section of the optical fiber to a next pillar including the extra length section, configures a window function in the analysis target section based on a pillar-to-pillar distance indicating a distance between adjacent pillars that is given in advance, searches for an offset point in the analysis target section where a correlation function between the window function and the weighted dissimilarity takes a maximum value, and estimates, in the analysis target section, the position of the offset point and a position obtained by adding the offset point to the pillar-to-pillar distance as the position of the pillar suspending the optical fiber, the position evaluation device according to claim 1, wherein the left and right ends of the extra length section are estimated to be the position of the offset point and a position on the sensor side of the offset point where the weighted difference takes a maximum peak value in the analysis section.(Supplementary Note 6) The position evaluation device according to any one of Supplementary Notes 2 to 5, wherein the predetermined frequency band is a frequency band including a fundamental vibration mode in an aerial section of the optical fiber. (Supplementary Note 7) A position evaluation method executed by the position evaluation device, comprising: a vibration characteristics calculation step of receiving, from a sensor, a signal indicating a natural vibration occurring at each position of the optical fiber, and calculating sensing data indicating vibration characteristics at each position of the optical fiber based on the received signal, a difference calculation step of calculating a difference in the sensing data between two adjacent points of the optical fiber, and an environment change position estimation step of estimating an environment change position where an environment of the optical fiber changes based on the difference. (Supplementary Note 8) A position evaluation method according to Supplementary Note 7, wherein the optical fiber is an optical fiber suspended on a pillar, the vibration characteristic calculation step calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation step calculates a dissimilarity of the power spectrum between two adjacent points on the optical fiber, and the environment change position estimation step estimates a position where the dissimilarity takes a maximum peak value as the position of the pillar suspending the optical fiber. (Supplementary Note 9) A position evaluation method according to Supplementary Note 7, wherein the optical fiber is an optical fiber suspended above a pole, the vibration characteristic calculation step calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation step calculates a dissimilarity of the power spectrum between two adjacent points on the optical fiber, and calculates a weighted dissimilarity by weighting the calculated dissimilarity by a frequency average value of the power spectrum, and the environmental change position estimation step sets a range in which the frequency average value of the power spectrum is below a threshold as a range of a spare length section of the optical fiber, and estimates positions within the range of the spare length section where the weighted dissimilarity takes a maximum peak value as the left and right ends of the spare length section.(Supplementary Note 10) A position evaluation method according to Supplementary Note 7, wherein the optical fiber is an optical fiber suspended on a pillar, wherein the vibration characteristic calculation step calculates a power spectrum in a predetermined frequency band as the sensing data, wherein the dissimilarity calculation step calculates a dissimilarity of the power spectrum between two adjacent points on the optical fiber, and wherein the environmental change position estimation step determines an analysis target section to be a section including all pillars whose positions are to be estimated, wherein a window function is constructed in the analysis target section based on a pillar-to-pillar distance indicating the distance between adjacent pillars that is given in advance, wherein an offset point where a correlation function between the window function and the dissimilarity takes a maximum value is searched for in the analysis target section, and wherein the position of the offset point and the position obtained by adding the offset point to the pillar-to-pillar distance are estimated to be the position of the pillar suspending the optical fiber in the analysis target section. (Supplementary Note 11) The optical fiber is an optical fiber suspended on a pillar, and in the vibration characteristic calculation step, a power spectrum in a predetermined frequency band is calculated as the sensing data, and in the dissimilarity calculation step, a dissimilarity of the power spectrum between two adjacent points of the optical fiber is calculated, and a weighted dissimilarity is calculated by weighting the calculated dissimilarity by a frequency average value of the power spectrum, and in the environmental change position estimation step, a section from a pillar including an extra length section of the optical fiber to a next pillar including the extra length section is determined as an analysis section, and a window function is constructed in the analysis section based on a pillar-to-pillar distance indicating the distance between adjacent pillars that is given in advance, and an offset point where a correlation function between the window function and the weighted dissimilarity takes a maximum value is searched for in the analysis section, and in the analysis section, a position of the offset point and a position obtained by adding the offset point to the pillar-to-pillar distance are estimated as positions of the pillars suspending the optical fiber, 8. The position evaluation method according to claim 7, wherein, in the analysis target section, the position of the offset point and a position on the sensor side of the offset point where the weighted dissimilarity takes a maximum peak value are estimated to be the left and right ends of the extra length section.(Supplementary Note 12) The position evaluation method according to any one of Supplementary Notes 8 to 11, wherein the predetermined frequency band is a frequency band including a fundamental vibration mode in an aerial section of the optical fiber. (Supplementary Note 13) A non-transitory computer-readable medium having stored thereon a program to be executed by a computer, the program including: a vibration characteristics calculation step of receiving, from a sensor, a signal indicating a natural vibration occurring at each position of the optical fiber, and calculating, based on the received signal, sensing data indicating vibration characteristics of each position of the optical fiber, a difference calculation step of calculating a difference in the sensing data between two adjacent points of the optical fiber, and an environment change position estimation step of estimating, based on the difference, an environment change position where an environment of the optical fiber changes. (Supplementary Note 14) The computer-readable medium described in Supplementary Note 13, wherein the optical fiber is an optical fiber suspended on a pillar, the vibration characteristic calculation step calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation step calculates the dissimilarity of the power spectrum between two adjacent points on the optical fiber, and the environmental change position estimation step estimates the position where the dissimilarity takes a maximum peak value as the position of the pillar suspending the optical fiber. (Supplementary Note 15) The computer-readable medium according to Supplementary Note 13, wherein the optical fiber is an optical fiber suspended above a pole, the vibration characteristic calculation step calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation step calculates a dissimilarity of the power spectrum between two adjacent points on the optical fiber, and calculates a weighted dissimilarity by weighting the calculated dissimilarity by a frequency average value of the power spectrum, and the environmental change position estimation step sets a range in which the frequency average value of the power spectrum is below a threshold as a range of a spare length section of the optical fiber, and estimates positions within the range of the spare length section where the weighted dissimilarity takes a maximum peak value as the left and right ends of the spare length section.(Supplementary Note 16) The optical fiber is an optical fiber suspended on a pillar, and in the vibration characteristic calculation step, a power spectrum in a predetermined frequency band is calculated as the sensing data, and in the dissimilarity calculation step, a dissimilarity of the power spectrum between two adjacent points on the optical fiber is calculated, and in the environmental change position estimation step, a section including all pillars whose positions are to be estimated is determined as an analysis section, and in the analysis section, a window function is constructed based on a pillar-to-pillar distance indicating the distance between adjacent pillars that is given in advance, and in the analysis section, an offset point where a correlation function between the window function and the dissimilarity takes a maximum value is searched for, and in the analysis section, the position of the offset point and the position obtained by adding the offset point to the pillar-to-pillar distance are estimated as the position of the pillar suspending the optical fiber. (Supplementary Note 17) The optical fiber is an optical fiber suspended on a pillar, and in the vibration characteristic calculation step, a power spectrum in a predetermined frequency band is calculated as the sensing data, and in the dissimilarity calculation step, a dissimilarity of the power spectrum between two adjacent points of the optical fiber is calculated, and a weighted dissimilarity is calculated by weighting the calculated dissimilarity by a frequency average value of the power spectrum, and in the environmental change position estimation step, a section from a pillar including an excess length section of the optical fiber to a next pillar including the excess length section is determined as an analysis section, a window function is configured in the analysis section based on a pillar-to-pillar distance indicating the distance between adjacent pillars that is given in advance, and an offset point where a correlation function between the window function and the weighted dissimilarity takes a maximum value is searched for in the analysis section, and in the analysis section, a position of the offset point and a position obtained by adding the offset point to the pillar-to-pillar distance are estimated as positions of the pillars suspending the optical fiber, the left and right ends of the extra length section are estimated to be the position of the offset point and a position on the sensor side of the offset point where the weighted difference takes a maximum peak value in the analysis section.(Supplementary Note 18) The computer-readable medium according to any one of Supplementary Notes 14 to 17, wherein the predetermined frequency band is a frequency band that includes a fundamental vibration mode in the aerial section of the optical fiber.

[0130] 10, 20, 30, 40, 50 Position evaluation device 11, 21, 31, 41 Vibration characteristic extraction unit 12, 32, 52 Difference calculation unit 13, 33, 44 Pillar position calculation unit 22, 42 Weighted difference calculation unit 23, 43 Extra length section calculation unit 51 Vibration characteristic calculation unit 53 Environmental change position estimation unit 90 Computer 91 Processor 92 Memory 93 Storage 94 Input / output interface 941 Display device 942 Input device 943 Sound output device 95 Communication interface

Claims

1. a vibration characteristic calculation unit that receives a signal indicating a natural vibration generated at each position of the optical fiber from the sensor and calculates sensing data indicating a vibration characteristic at each position of the optical fiber based on the received signal; a difference calculation unit that calculates a difference in the sensing data between two adjacent points of the optical fiber; and an environment change position estimating unit that estimates an environment change position where an environment of the optical fiber changes based on the degree of difference.

2. The optical fiber is a pole-mounted optical fiber, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates a dissimilarity of the power spectrum between two adjacent points of the optical fiber; the environment change position estimation unit estimates a position where the degree of difference has a maximum peak value as a position of a pillar suspending the optical fiber; The position evaluation device according to claim 1 .

3. The optical fiber is a pole-mounted optical fiber, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates a dissimilarity of the power spectrum between two adjacent points of the optical fiber, and calculates a weighted dissimilarity by weighting the calculated dissimilarity by an average frequency of the power spectrum; the environmental change position estimating unit sets a range in which the frequency average value of the power spectrum falls below a threshold value as a range of the extra length section of the optical fiber, and estimates positions within the range of the extra length section where the weighted dissimilarity has a maximum peak value as the left end and right end of the extra length section. The position evaluation device according to claim 1 .

4. The optical fiber is a pole-mounted optical fiber, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates a dissimilarity of the power spectrum between two adjacent points of the optical fiber; The environment change position estimation unit is The section including all the pillars whose positions are to be estimated is determined as the analysis section. A window function is configured based on a column distance indicating a distance between adjacent columns given in advance in the analysis section; searching for an offset point at which a correlation function between the window function and the dissimilarity takes a maximum value in the analysis interval; In the analysis section, a position of the offset point and a position obtained by adding the offset point to the distance between pillars are estimated as positions of pillars suspending the optical fiber. The position evaluation device according to claim 1 .

5. The optical fiber is a pole-mounted optical fiber, the vibration characteristic calculation unit calculates a power spectrum in a predetermined frequency band as the sensing data, the dissimilarity calculation unit calculates a dissimilarity of the power spectrum between two adjacent points of the optical fiber, and calculates a weighted dissimilarity by weighting the calculated dissimilarity by an average frequency of the power spectrum; The environment change position estimation unit is determining a section from a pole including the extra length section of the optical fiber to a next pole including the extra length section as an analysis target section; A window function is configured based on a column distance indicating a distance between adjacent columns given in advance in the analysis section; searching for an offset point at which a correlation function between the window function and the weighted dissimilarity takes a maximum value in the analysis interval; In the analysis section, a position of the offset point and a position obtained by adding the offset point to the distance between columns are estimated as positions of columns suspending the optical fiber; In the analysis target section, the position of the offset point and a position on the sensor side of the offset point where the weighted difference takes a maximum peak value are estimated to be the left end and the right end of the extra length section. The position evaluation device according to claim 1 .

6. the predetermined frequency band is a frequency band including a fundamental vibration mode in the overhead section of the optical fiber; The position evaluation device according to claim 2 .

7. A location estimation method executed by a location estimation device, comprising: a vibration characteristic calculation step of inputting a signal indicating a natural vibration generated at each position of the optical fiber from a sensor, and calculating sensing data indicating a vibration characteristic at each position of the optical fiber based on the input signal; a difference calculation step of calculating a difference in the sensing data between two adjacent points of the optical fiber; and estimating an environment change position where an environment of the optical fiber changes based on the degree of difference.

8. The optical fiber is a pole-mounted optical fiber, In the vibration characteristic calculation step, a power spectrum in a predetermined frequency band is calculated as the sensing data, In the dissimilarity calculation step, a dissimilarity of the power spectrum between two adjacent points of the optical fiber is calculated, In the environmental change position estimating step, a position where the degree of difference has a maximum peak value is estimated to be a position of a pillar suspending the optical fiber. The position evaluation method according to claim 7.

9. The optical fiber is a pole-mounted optical fiber, In the vibration characteristic calculation step, a power spectrum in a predetermined frequency band is calculated as the sensing data, In the dissimilarity calculation step, a dissimilarity of the power spectrum between two adjacent points of the optical fiber is calculated, and a weighted dissimilarity is calculated by weighting the calculated dissimilarity by a frequency average value of the power spectrum, In the environmental change position estimating step, a range in which the frequency average value of the power spectrum falls below a threshold is set as a range of the extra length section of the optical fiber, and positions within the range of the extra length section where the weighted dissimilarity has a maximum peak value are estimated to be the left end and the right end of the extra length section. The position evaluation method according to claim 7.

10. On the computer, a vibration characteristic calculation step of inputting a signal indicating a natural vibration generated at each position of the optical fiber from a sensor, and calculating sensing data indicating a vibration characteristic at each position of the optical fiber based on the input signal; a difference calculation step of calculating a difference in the sensing data between two adjacent points of the optical fiber; and an environment change position estimating step of estimating an environment change position where the environment of the optical fiber changes based on the degree of difference.