Patent Publication Number: US-2021172767-A1

Title: Utility pole location specifying system, utility pole location specifying apparatus, utility pole location specifying method, and non-transitory computer readable medium

Description:
TECHNICAL FIELD 
     The present disclosure relates to a utility pole location specifying system, a utility pole location specifying apparatus, a utility pole location specifying method, and a non-transitory computer readable medium. 
     BACKGROUND ART 
     Conventionally, abnormalities of utility poles are often detected manually. For example, a worker determines an abnormality only by a visual observation, or taps on a utility pole and determines an abnormality based on reverberating sound or the like. However, when an abnormality of a utility pole is manually detected, it takes large amounts of time and cost, and thus in some cases, detecting an abnormality and coping therewith are delayed. 
     Therefore, recently, a system for monitoring a utility pole for detecting an abnormality thereof by using an optical fiber has been proposed (e.g., Patent Literatures 1 and 2). 
     In a technique disclosed in Patent Literature 1, an optical fiber is linearly or spirally disposed in the vertical direction of a utility pole. When a utility pole is broken by a collision of an automobile with the utility pole, the optical fiber is severely bent, so that a loss occurs in an optical signal propagating through the inside of the optical fiber. In this way, it is detected that one of a plurality of utility poles has been broken by detecting the amount of a loss caused by the above-described loss through OTDR (Optical Time-Domain Reflectometry) measurement. 
     Further, in a technique disclosed in Patent Literature 2, a nesting detection core line, which is composed of an optical fiber for detecting nesting in a utility pole, is disposed. When the nesting detection core line is warped due to nesting in the utility pole, the nesting detection core line is distorted, e.g., is bent or stretched, so that the strength of an optical signal propagating through the inside of the nesting detection core line is attenuated. As a result, it is detected that a nest has been made by detecting the amount of a loss caused by this attenuation through OTDR measurement. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2008-067467 
     Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2015-053832 
     SUMMARY OF INVENTION 
     Technical Problem 
     As automated monitoring of utility poles for detecting abnormalities thereof has been becoming more common, it is likely that demands for techniques for specifying locations of utility poles and automatically finding which utility poles are monitored will increase. 
     Note that, in the techniques disclosed in Patent Literatures 1 and 2, the location of a utility pole is specified by monitoring the amount of an optical loss through OTDR measurement and measuring a distance from a monitoring apparatus to a place where the loss has occurred. 
     However, in the techniques disclosed in Patent Literatures 1 and 2, there is a problem that in order to specify the location of a utility pole, it is necessary to have information about a correspondence relation between distances from the monitoring apparatus and all the utility poles in advance. 
     Therefore, an object of the present disclosure is to solve the above-described problem and to provide a utility pole location specifying system, a utility pole location specifying apparatus, a utility pole location specifying method, and a non-transitory computer readable medium capable of accurately and automatically specifying the location of a utility pole. 
     Solution to Problem 
     A utility pole location specifying system according to one aspect includes: 
     a cable disposed in a utility pole, the cable containing a communication optical fiber; 
     a receiving unit configured to receive an optical signal containing a characteristic pattern of the utility pole from at least one communication optical fiber contained in the cable; and 
     a specifying unit configured to specify a location of the utility pole based on the characteristic pattern. 
     A utility pole location specifying apparatus according to another aspect includes: 
     a receiving unit configured to receive an optical signal containing a characteristic pattern of a utility pole from at least one communication optical fiber contained in a cable disposed in the utility pole; and 
     a specifying unit configured to specify a location of the utility pole based on the characteristic pattern. 
     A utility pole location specifying method according to another aspect is a utility pole location specifying method performed by a utility pole location specifying apparatus, including: 
     receiving an optical signal containing a characteristic pattern of a utility pole from at least one communication optical fiber contained in a cable disposed in the utility pole; and 
     specifying a location of the utility pole based on the characteristic pattern. 
     A non-transitory computer readable medium according to another aspect is a non-transitory computer readable medium storing a program for causing a computer to perform: 
     a process of receiving an optical signal containing a characteristic pattern of a utility pole from at least one communication optical fiber contained in a cable disposed in the utility pole; and 
     a process of specifying a location of the utility pole based on the characteristic pattern. 
     Advantageous Effects of Invention 
     According to the above-described aspect, it is possible to achieve an advantageous effect that the location of a utility pole can be accurately and automatically specified. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an example of a configuration of a utility pole location specifying system according to an example embodiment; 
         FIG. 2  shows an example of vibration data at each distance used in a first method performed in a utility pole location specifying system according to an example embodiment; 
         FIG. 3  shows an example of a result of the specifying of the location of each of utility poles by the first method performed in a utility pole location specifying system according to an example embodiment; 
         FIG. 4  shows an example of vibration data at each distance used in a second method performed in a utility pole location specifying system according to an example embodiment; 
         FIG. 5  shows an example of a result of the specifying of the location of each of utility poles by the second method performed in a utility pole location specifying system according to an example embodiment; 
         FIG. 6  shows an example of vibration data at each distance used in a third method performed in a utility pole location specifying system according to an example embodiment; 
         FIG. 7  shows an example of machine learning by a fourth method performed in a utility pole location specifying system according to an example embodiment; 
         FIG. 8  is a block diagram showing an example of a hardware configuration of a computer that implements a utility pole location specifying apparatus according to an example embodiment; 
         FIG. 9  is a flowchart showing an example of a flow of operations performed by a utility pole location specifying system according to an example embodiment; 
         FIG. 10  shows an example of a frequency characteristic of vibration data of a type-X utility pole; 
         FIG. 11  shows an example of a frequency characteristic of vibration data of a type-Y utility pole; 
         FIG. 12  shows an example of a utility pole location specifying system according to another example embodiment; 
         FIG. 13  shows an example of a disposition of a fiber sensing unit in a utility pole location specifying system according to another example embodiment; 
         FIG. 14  shows another example of a disposition of a fiber sensing unit in a utility pole location specifying system according to another example embodiment; 
         FIG. 15  shows yet another example of a disposition of a fiber sensing unit in a utility pole location specifying system according to another example embodiment; 
         FIG. 16  shows yet another example of a disposition of a fiber sensing unit in a utility pole location specifying system according to another example embodiment; 
         FIG. 17  shows an example of an operation that is performed by the fiber sensing unit when an optical fiber cable is broken in the utility pole location specifying system shown in  FIG. 13 ; 
         FIG. 18  shows an example of an operation that is performed by the fiber sensing unit when an optical fiber cable is broken in the utility pole location specifying system shown in  FIG. 14 ; and 
         FIG. 19  shows an example of an operation that is performed by the fiber sensing unit when an optical fiber cable is broken in the utility pole location specifying system shown in  FIG. 16 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Example embodiments according to the present disclosure will be described hereinafter with reference to the drawings. 
     EXAMPLE EMBODIMENT 
     Configuration of Example Embodiment 
     Firstly, a configuration of a utility pole location specifying system according to this example embodiment will be described with reference to  FIG. 1 . Note that, in  FIG. 1 , only three utility poles  10  are shown for simplifying the explanation. Further, the three utility poles  10  are indicated by utility pole numbers A, B and C, respectively. 
     As shown in  FIG. 1 , the utility pole location specifying system according to this example embodiment is a system for specifying the locations of the utility poles  10 , and includes an optical fiber cable  20  and a utility pole location specifying apparatus  33 . 
     The optical fiber cable  20  is strung (e.g., stretched) through the utility poles  10 . When the optical fiber cable  20  is strung through the utility poles  10 , it is strung (e.g., stretched) substantially perpendicular to the longitudinal direction of the utility poles  10 . 
     The optical fiber cable  20  is a cable containing at least one communication optical fiber. One end of the optical fiber cable  20  is routed to the inside of a communication carrier station building  30 , and the other end thereof is terminated at the utility pole  10  having the utility pole number C. 
     The utility pole location specifying system according to this example embodiment specifies the locations of the utility poles  10  by using an optical fiber sensing technique in which the optical fiber is used as a sensor. 
     Specifically, pulsed light is made to enter the communication optical fiber contained in the optical fiber cable  20  inside the communication carrier station building  30 . As a result, as the pulsed light is transmitted through the communication optical fiber toward the utility poles  10 , backscattered light is generated each time the pulsed light travels a certain transmission distance. The backscattered light returns to the inside of the communication carrier station building  30  through the same communication optical fiber. 
     Note that the utility poles  10  vibrate due to disturbances from the surrounding environment or naturally vibrate, and the vibrations of the utility poles  10  are transmitted to the communication optical fiber. It should be noted that the parts of the optical fiber cable  20  which are not disposed in the utility poles  10  also naturally vibrate. However, the vibration patterns of the utility poles  10  are patterns characteristic of the utility poles  10  and are different from the vibration patterns of the parts of the optical fiber  20  which are not disposed in the utility poles  10 . 
     Therefore, the backscattered light returning to the inside of the communication carrier station building  30  contains the characteristic patterns of the utility poles  10 . In the example shown in  FIG. 1 , since the three utility poles  10  are provided, the backscattered light returning to the inside of the communication carrier station building  30  contains the characteristic patterns corresponding the three utility poles  10 . 
     The utility pole location specifying system according to this example embodiment specifies the locations of the utility poles  10  by utilizing the fact that the pattern of the backscattered light returning to the inside of the communication carrier station building  30  contains the characteristic patterns of the utility poles  10 . 
     Note that the above-described utility pole location specifying apparatus  33  is provided inside the communication carrier station building  30 . The utility pole location specifying apparatus  33  is equipment that is newly installed in order to implement this example embodiment. 
     The utility pole location specifying apparatus  33  is an apparatus having a function of specifying the locations of the utility poles  10  in addition to the functions as the optical fiber sensing apparatus. Specifically, the utility pole location specifying apparatus  33  includes a fiber sensing unit  331  and a specifying unit  332 . The fiber sensing unit  331  is an example of the receiving unit. 
     The fiber sensing unit  331  makes pulsed light enter at least one communication optical fiber contained in the optical fiber cable  20 . This pulsed light is transmitted toward the utility poles  10 . Further, the fiber sensing unit  331  receives backscattered light of the pulsed light from the same communication optical fiber to which the pulsed light has entered. This backscattered light is received in the direction from the utility poles  10 . 
     Note that, as described above, the backscattered light received by the fiber sensing unit  331  contains the characteristic patterns of the utility poles  10 . 
     Therefore, the specifying unit  332  specifies the locations of the utility poles  10  based on the characteristic patterns of the utility poles  10  contained in the backscattered light received by the fiber sensing unit  331 . 
     Next, several methods in which the specifying unit  332  specifies the locations of the utility poles  10  based on the characteristic patterns of the utility poles  10  contained in the backscattered light received by the fiber sensing unit  331  will be described. 
     (1) First Method 
     Firstly, a first method for specifying the locations of utility poles  10  will be described with reference to  FIG. 2 .  FIG. 2  shows vibration data at each distance from the fiber sensing unit  331  (in which, a horizontal axis indicates distances and a vertical axis indicates time of occurrences). In  FIG. 2 , the density of shading in a section in which a utility pole vibrates is changed according to the magnitude of the vibration. Note that the vibration data at each distance shown in  FIG. 2  was obtained by the fiber sensing unit  331  by detecting backscattered light received from the communication optical fiber by using a distributed acoustic sensor (Distributed Acoustic Sensor) and a distributed vibration sensor (Distributed Vibration Sensor). 
     In the first method, vibrations that are non-artificially generated in the utility pole  10  due to changes in the surrounding environments are used. 
     When the specifying unit  332  specifies the locations of the utility poles  10 , it first acquires vibration data at each distance like the one shown in  FIG. 2  from the fiber sensing unit  331 . 
     In the vibration data at each distance shown in  FIG. 2 , vibrations occur at several places different distances away from the fiber sensing unit  331 . 
     Therefore, for example, the specifying unit  332  determines a section in which the number of times of vibrations in a certain period is equal to or greater than a threshold as a section in which a characteristic pattern of a utility pole  10  occurs, and specifies the center of that section as the location of the utility pole  10 . 
     Alternatively, the specifying unit  332  determines a section in which the magnitude of vibrations is equal to or greater than a threshold as a section in which a characteristic pattern of a utility pole  10  occurs, and specifies a point in that section at which vibrations having the maximum magnitude occur as the location of the utility pole  10 . 
     In the example shown in  FIG. 2 , the specifying unit  332  specifies places about 125 m, 168 m, and 188 m away from the fiber sensing unit  331  as the locations of utility poles  10 .  FIG. 3  shows an image of a result of the specified location of each utility pole  10 . 
     (2) Second Method 
     Next, a second method for specifying the locations of utility poles  10  will be described with reference to  FIG. 4 .  FIG. 4  shows vibration data at each distance from the fiber sensing unit  331  (in which, a horizontal axis indicates distances and a vertical axis indicates time of occurrences). In  FIG. 4 , the density of shading in a section in which a utility pole vibrates is changed according to the magnitude of the vibration. Note that the vibration data shown in  FIG. 4  was obtained by the fiber sensing unit  331  by detecting backscattered light received from the communication optical fiber by using a distributed acoustic sensor and a distributed vibration sensor. 
     In the second method, a user taps on a utility pole  10  with a hammer or the like and thereby artificially generates vibrations in the utility pole  10 , and the generated artificial vibrations are used. 
     For example, when artificial vibrations are generated in the utility pole  10  having the utility pole number A, vibrations occur at a point corresponding to the distance from the fiber sensing unit  331  to the utility poles  10  having the utility pole number A in the vibration data at each distance shown in  FIG. 4 . 
     Therefore, when the specifying unit  332  specifies the locations of utility poles  10 , it first acquires vibration data at each distance like the one shown in  FIG. 4 . Then, the specifying unit  332  determines a pattern of the vibrations artificially generated in the utility pole  10  having the utility pole number A as a characteristic pattern of the utility pole  10 , and specifies a point in the section where the characteristic pattern of the utility poles  10  occurs as the location of the utility pole  10  having the utility pole number A. The method for specifying the point in the above-described method may be similar to that used in the first method. The positions of the utility poles  10  having the utility pole numbers B and C are also specified in a similar manner.  FIG. 5  shows an image of a result of the specified location of each utility pole  10 . In the second method, since a user taps on the utility poles  10  with a hammer or the like while recognizing which utility pole  10  he/she is tapping on, it is possible to associate the utility pole number of the utility pole  10  with the location of the utility pole  10 . 
     (3) Third Method 
     Next, a third method for specifying the locations of utility poles  10  will be described with reference to  FIG. 6 .  FIG. 6  shows vibration data at each distance from the fiber sensing unit  331  (in which, a horizontal axis indicates distances and a vertical axis indicates magnitudes (amplitudes) at a specific frequency). Note that the vibration data shown in  FIG. 6  was obtained by the fiber sensing unit  331  by detecting backscattered light received from the communication optical fiber by using a distributed acoustic sensor and a distributed vibration sensor. 
     The third method uses a fact that while parts of the optical fiber cable  20  disposed between the utility poles  10  are greatly affected by outside environments such as a wind, the utility poles  10  themselves are less likely to be affected by these outside environments. 
     That is, since parts of the optical fiber cable  20  disposed between utility poles  10  widely vibrates due to a wind or the like, the magnitude of vibrations at the vibration frequency of the vibrations caused by a wind or the like increases. Meanwhile, the magnitude of vibrations at the vibration frequency of the vibrations of the utility poles  10  decreases. 
       FIG. 6  shows vibration data at each distance in which a vibration frequency of vibrations caused by a wind or the like is used as a specific frequency. In the vibration data at each distance shown in  FIG. 6 , there are parts having large magnitudes, and these parts can be determined as the central parts of the parts of the optical fiber cable  20  disposed between the utility poles  10 . Meanwhile, there are parts having small magnitudes, and these parts can be determined as parts where utility poles  10  are located. 
     Therefore, when the specifying unit  332  specifies the locations of the utility poles  10 , it first acquires vibration data at each distance like the one shown in  FIG. 6 . Then, the specifying unit  332  specifies parts having small magnitudes as the locations of utility poles  10 . An image of a result of the specified location of each utility pole  10  is similar to that shown in  FIG. 3 . 
     (4) Fourth Method 
     Next, a fourth method for specifying the locations of utility poles  10  will be described. 
     In the fourth method, the specifying unit  332  performs machine learning (e.g., deep learning) for vibration patterns at locations where utility poles  10  are present, and specifies the locations of utility poles  10  by using the learning result of the machine learning (an initial training model). 
     Firstly, a method for performing machine learning in the fourth method will be described with reference to  FIG. 7 . 
     As shown in  FIG. 7 , the specifying unit  332  inputs teacher data, which is location information indicating the locations of utility poles  10  having utility pole numbers A, B and C, and vibration data at each distance obtained from the fiber sensing unit  331  (steps S 1  and S 2 ). Note that the location information is one shown in  FIG. 5 . Further, the vibration data at each distance is those shown in  FIGS. 2, 4 and 6 . 
     Next, the specifying unit  332  performs matching between these information and data, and classification thereof (step S 3 ), and performs supervised training (step S 4 ). In this way, an initial training model is obtained (step S 5 ). This initial training model is such a model that when vibration data at each distance is input to the initial training model, locations where utility poles  10  are present are output. 
     Next, a method for specifying locations of utility poles  10  in the fourth method will be described. 
     When the specifying unit  332  specifies the locations of utility poles  10 , it acquires, from the fiber sensing unit  331 , vibration data at each distance measured from the fiber sensing unit  331  (e.g., those shown in  FIG. 2, 4 or 6 ) and inputs the acquired vibration data to the initial training model. As a result, the specifying unit  332  acquires the locations of utility poles  10  as a result output from the initial training model. 
     As described above, in the fourth method, machine learning for vibration data (vibration patterns) at locations where utility poles  10  are present is performed, and then the locations of utility poles  10  are specified by using the learning result of the machine learning. 
     In some cases, it is very difficult to extract features by which the locations of utility poles  10  are specified from vibration data by manually analyzing the vibration data. In the fourth method, it is possible, by constructing a training model from a large amount of vibration data, to accurately specify the locations of utility poles  10  even in the case where it is very difficult to manually analyze the vibration data. 
     Note that, in the machine learning in the fourth method, in the initial state, a training model may be generated based on at least two teacher data. Further, it is possible to make the generated training model newly learn distance-by-distance vibration data distance that is newly collected by the fiber sensing unit  331 . In this case, details of the conditions for specifying the locations of utility poles  10  may be adjusted when the new training model is used for the first time. 
     Next, a hardware configuration of a computer  40  that implements the utility pole location specifying apparatus  33  will be described with reference to  FIG. 8 . 
     As shown in  FIG. 8 , the computer  40  includes a processor  401 , a memory  402 , a storage  403 , an input/output interface (an input/output I/F)  404 , a communication interface (communication I/F)  405 , and the like. The processor  401 , the memory  402 , the storage  403 , the input/output interface  404 , and the communication interface  405  are connected to each other through data transmission lines through which they transmit/receive data to/from each other. 
     The processor  401  is, for example, an arithmetic processing unit such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The memory  402  is, for example, a memory such as a RAM (random access memory) or a ROM (Read Only Memory). The storage  403  is, for example, a storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a memory card. Further, the storage  403  may be a memory such as a RAM or a ROM. 
     The storage  403  stores programs for implementing the functions of the fiber sensing unit  331  and the specifying unit  332  included in the utility pole location specifying apparatus  33 . The processor  401  implements the function of each of the fiber sensing unit  331  and the specifying unit  332  by executing the respective programs. Note that when the processor  401  executes these respective programs, it may execute the programs after loading them onto the memory  402  or may execute the programs without loading them onto the memory  402 . Further, the memory  402  and the storage  403  also have a function of storing information and data held by the fiber sensing unit  331  and the specifying unit  332 . 
     Further, the above-described program can be stored and provided to a computer (including the computer  40 ) using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (Compact Disc-Read Only Memory), CD-R (CD-Recordable), CD-R/W (CD-ReWritable), and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory), etc.). Further, the program may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g. electric wires, and optical fibers) or a wireless communication line. 
     The input/output interface  404  is connected to a display apparatus  4041 , an input apparatus  4042 , and the like. The display apparatus  4041  is an apparatus, such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube) display, which displays an image corresponding to drawing data processed by processor  401 . The input apparatus  4042  is an apparatus that receives an operation input from an operator, and is, for example, a keyboard, a mouse, and a touch sensor. The display apparatus  4041  and the input apparatus  4042  may be integrated with each other and hence implemented as a touch panel. Note that the computer  40  may also include sensors (not shown) including a distributed acoustic sensor and a distributed vibration sensor, and have a configuration in which these sensors are connected to the input/output interface  404 . 
     The communication interface  405  transmits/receives data to/from an external apparatus. For example, the communication interface  405  communicates with an external apparatus through a wired communication line or a radio communication channel. 
     Operation in Example Embodiment 
     Operation performed by the utility pole location specifying system according to this example embodiment will be described hereinafter. Here, a flow of operations performed by the utility pole location specifying system according to this example embodiment will be described with reference to  FIG. 9 . 
     As shown in  FIG. 9 , firstly, the fiber sensing unit  331  makes pulsed light enter at least one communication optical fiber contained in the optical fiber cable  20  (step S 11 ). 
     Next, the fiber sensing unit  331  receives backscattered light containing characteristic patterns of utility poles  10  from the same communication optical fiber to which the pulsed light has entered (step S 12 ). 
     After that, the specifying unit  332  specifies the locations of utility poles  10  based on the characteristic patterns of the utility poles  10  contained in the backscattered light received by the fiber sensing unit  331  (step S 13 ). Note that the specifying unit  332  may specify the locations of the utility poles  10  by using one of the above-described first to fourth methods. 
     Effect of Example Embodiment 
     As described above, according to this example embodiment, backscattered light (optical signals) containing characteristic patterns of utility poles  10  is received from at least one communication optical fiber contained in the optical fiber cable  20 , and the locations of the utility poles  10  are specified based on the characteristic patterns of the utility poles  10 . Therefore, it is possible to accurately and automatically specify the locations of utility poles. 
     Further, according to this example embodiment, it is sufficient to have an existing communication optical fiber in order to specify the locations of utility poles  10 . That is, unlike Patent Literature 1, there is no need to linearly or spirally dispose an optical fiber in the vertical direction of a utility pole, and unlike Patent Literature 2, there is no need to dispose a nesting detection core line in a utility pole. Therefore, since the utility pole location specifying system requires no dedicated structure in order to specify the locations of utility poles  10 , it can be constructed at a low cost. 
     Further, according to this example embodiment, it is possible to simultaneously and remotely specify the locations of a plurality of utility poles  10  by using an existing communication optical fiber. Therefore, it is possible to easily specify the locations of utility poles  10  and reduce the cost required to specify the locations of utility poles  10 . 
     Further, according to this example embodiment, an optical fiber sensing technique in which an optical fiber is used as a sensor is used. Therefore, for example, there are following advantages: the system is not affected by electromagnetic noises; there is no need to supply power to the sensor; the system has an excellent environmental resistance; and the maintenance thereof is easy. 
     Other Example Embodiment 
     It should be noted that each of the utility poles  10  may have a different characteristic pattern. 
     In this case, for example, the specifying unit  332  holds a correspondence table in which the characteristic patterns of utility poles  10  are associated with information about the utility poles  10  (e.g., utility pole numbers, types, and the like of the utility poles  10 ), so that the specifying unit  332  can specify the locations of the utility poles  10  based on the characteristic patterns of the utility poles  10  contained in the optical signal received by the fiber sensing unit  331 . 
     Further, the characteristic pattern of a utility pole  10  changes according to the type of the utility pole  10  (e.g., the material of the utility pole  10 ) or the state of the utility pole  10  (e.g., the deterioration state of the utility pole  10 ). 
     The fact that the characteristic pattern of a utility pole  10  changes according to the type of the utility pole  10  will be explained hereinafter with reference to  FIGS. 10 and 11 . Note that  FIGS. 10 and 11  show frequency characteristics (a horizontal axis indicates frequencies and a vertical axis indicates magnitudes (amplitudes)) of vibration data (a horizontal axis indicates time and a vertical axis indicates magnitudes (amplitudes)) of a utility pole  10  after an FFT (Fast Fourier Transform) is performed for the vibration data. In particular,  FIG. 10  shows a frequency characteristic of vibration data of an X-type utility pole  10 , and  FIG. 11  shows a frequency characteristic of vibration data of a Y-type utility pole  10 . Note that the frequency characteristics shown in  FIGS. 10 and 11  were obtained by the fiber sensing unit  331  by detecting backscattered light received from the communication optical fiber by using a distributed acoustic sensor and a distributed vibration sensor. 
     As shown in  FIG. 10 , in the case of the X-type utility pole  10 , a peak of the strength appears in a low frequency band irrespective of the deterioration state of the utility pole  10 . In contrast, as shown in  FIG. 11 , in the case of the Y-type utility pole  10 , a peak of the strength appears in a high frequency band irrespective of the deterioration state of the utility pole  10 . 
     Therefore, for example, the specifying unit  332  holds a correspondence table in which the characteristic patterns of utility poles  10  are associated with the types of the utility poles  10 , so that the specifying unit  332  can specify the types of these utility poles  10  based on the characteristic patterns of the utility poles  10  contained in the optical signal received by the fiber sensing unit  331 . 
     Further, although not shown in the drawing, the characteristic pattern of a utility pole  10  also changes according to the state of the utility poles  10 . Therefore, the specifying unit  332  can also specify the state of the utility poles  10  by holding a correspondence table in which the characteristic patterns of utility poles  10  are associated with the states of the utility poles  10 . 
     Further, the specifying unit  332  may generate a map indicating the locations of a plurality of utility poles  10  through which the optical fiber cables  20  are strung (e.g., stretched). Further, the specifying unit  332  may associate the locations of the utility poles  10  with the types or the states of the utility poles  10  specified as described above in the above-described map. 
     Further, similar to the above-described fourth method, the specifying unit  332  may perform machine learning for the characteristic patterns of the utility poles  10  according to the types of the utility poles  10  or perform machine learning for the characteristic patterns of the utility poles  10  according to the states of the utility poles  10 , and specify the types or the states of the utility poles  10  by using the learning result of the machine learning. 
     Further, in the case where the specifying unit  332  performs machine learning for the characteristic patterns of the utility poles  10  by the above-described fourth method or the like, it is considered that the characteristic patterns of the utility poles  10  also change depending on the region. For example, the characteristic patterns in a temperate region are different from those in a cold region. Therefore, the specifying unit  332  may perform machine learning for each region by using teacher data corresponding to that region. 
     Further, as shown in  FIG. 12 , a monitoring terminal  50  that monitors the utility poles  10  based on the result of the specifying process performed by the utility pole location specifying apparatus  33  may be provided. The monitoring terminal  50  may show the locations of utility poles  10  to a system administrator or the like as a result of the specifying process performed by the utility pole location specifying apparatus  33 . Further, although the monitoring terminal  50  is provided outside the communication carrier station building  30  in the drawing, it may be provided inside the communication carrier station building  30 . Further, when the monitoring terminal  50  is provided outside the communication carrier station building  30 , utility poles  10  that are connected to a plurality of respective communication carrier station buildings  30  by optical fiber cables  20  may be monitored by one monitoring terminal  50  in a centralized manner. 
     Further, the fiber sensing unit  331  and the specifying unit  332  of the utility pole location specifying apparatus  33  are disposed remotely from each other. For example, only the fiber sensing unit  331  may be provided inside the communication carrier station building  30 , and the utility pole location specifying apparatus  33  including the specifying unit  332  may be provided outside the communication carrier station building  30 . 
     Further, in the above-described example embodiment, only one fiber sensing unit  331  is provided and it exclusively use the optical fiber cable  20 . However, the present disclosure is not limited to this example. The disposition of a fiber sensing unit  331  in a utility pole location specifying system according to other example embodiments will be described with reference to  FIGS. 13 to 16 . Note that, in  FIGS. 13 to 16 , the illustration of the specifying unit  332  is omitted. 
     In an example shown in  FIG. 13 , the fiber sensing unit  331  shares the optical fiber cable  20  with existing communication equipment  31 . Further, in order to enable the fiber sensing unit  331  and the existing communication equipment  31  to share the optical fiber cable  20 , a filter  32  for separating signals is provided. 
     In an example shown in  FIG. 14 , one fiber sensing unit  331  is provided in each of a plurality of communication carrier station buildings  30  (one fiber sensing unit  331  is provided in each of two communication carrier station buildings  30 A and  30 Z in  FIG. 14 ). Specifically, fiber sensing units  331 A and  331 Z are provided in the communication carrier station buildings  30 A and  30 Z, respectively. Note that, in the example shown in  FIG. 14 , utility poles  10  having utility pole numbers A, B and C are connected to the communication carrier station building  30 A by an optical fiber cable  20 , and utility poles  10  having utility pole numbers X, Y and Z are connected to the communication carrier station building  30 Z by another optical fiber cable  20 . Further, the utility poles  10  having the utility pole numbers C and Y are connected to each other by another optical fiber cable  20 . The communication equipment  31 A and  31 Z correspond to the communication equipment  31 , and the filters  32 A and  32 Z correspond to the filter  32 . 
     In the example shown in  FIG. 14 , both the fiber sensing units  331 A and  331 Z monitor the utility poles  10  having the utility pole numbers A, B, C, X, Y and Z. 
     In an example shown in  FIG. 15 , a data collection unit  34  is provided in a utility pole  10  having a utility pole number C as compared to the example shown in  FIG. 14 . Note that since the number of utility poles  10  is six, only one data collection unit  34  is provided. However, one data collection unit  34  may be provided for a predetermined number of utility poles  10  (e.g., for ten utility poles  10 ). That is, at least one data collection unit  34  may be provided. For example, in the case where the optical fiber cable  20  is strung (e.g., stretched) through  100  utility poles  10 , one data collection unit  34  may be provided for every ten utility poles  10 . That is, ten data collection units  34  may be provided in total. 
     In the example shown in  FIG. 15 , each of the data collection units  34  collects data about patterns (sounds, temperatures, vibrations, etc.) of a predetermined number of corresponding utility poles  10 , and the specifying unit  332  summarizes the data collected by all the data collection units  34 . Note that the data may be transmitted from each of the data collection units  34  to the specifying unit  332  through the optical fiber cable  20 , or may be transmitted through a separately provided radio apparatus. The specifying unit  332  specifies the locations of utility poles  10 , of which the data collection unit(s)  34  has collected data, based on their data. 
     Therefore, the section that is monitored by one fiber sensing unit  331  is shortened, and the number of utility poles  10  that are monitored by one fiber sensing unit  331  is reduced. Since the section monitored by the fiber sensing unit  331  is shortened, the distance of the transmission of the pulsed light and the backscattered light is also shortened, so that the loss caused by the fiber is reduced. As a result, the S/N ratio (the signal-to-noise ratio) of the received backscattered light is improved, so that the monitoring accuracy can be improved. Further, since the number of utility poles  10  monitored by the fiber sensing unit  331  is reduced, the monitoring cycle can be improved. 
     In an example shown in  FIG. 16 , a plurality of fiber sensing units  331  (two fiber sensing units  331 A and  331 Z in  FIG. 16 ) are provided in one communication carrier station building  30 AZ. Note that, in the example shown in  FIG. 16 , utility poles  10  having utility pole numbers A, B and C are connected to the fiber sensing unit  331 A by an optical fiber cable  20 , and utility poles  10  having utility pole numbers X, Y and Z are connected to the fiber sensing unit  331 Z by another optical fiber cable  20 . Further, the utility poles  10  having the utility pole numbers C and Y are connected to each other by another optical fiber cable  20 . The communication equipment  31 A and  31 Z correspond to the communication equipment  31 , and the filters  32 A and  32 Z correspond to the filter  32 . 
     In the example shown in  FIG. 16 , both the fiber sensing units  331 A and  331 Z monitor the utility poles  10  having the utility pole numbers A, B, C, X, Y and Z. However, the fiber sensing unit  331 A monitors the utility poles  10  by making pulsed light enter the optical fiber in a clockwise direction, and the fiber sensing unit  331 Z monitors the utility poles  10  by making pulsed light enter the optical fiber in a counterclockwise direction. 
     Note that in the case where a plurality of fiber sensing units  331  are provided as shown in  FIGS. 14 to 16 , one utility pole location specifying apparatus  33  including a specifying unit  332  may be provided for the plurality of fiber sensing units  331 . Further, the locations of utility poles  10  that are connected to a plurality of respective fiber sensing units  331  by optical fiber cables  20  may be specified by one utility pole location specifying apparatus  33  in a centralized manner. In this case, the utility pole location specifying apparatus  33  may be provided in the inside of one of the communication carrier station buildings  30 , or may be provided outside the communication carrier station buildings  30 . 
     Further, there is a possibility that the optical fiber cable  20  strung (e.g., stretched) through the utility poles  10  is broken. Therefore, operations that are performed by the fiber sensing unit  331  when the optical fiber cable  20  is broken in a utility pole location specifying system according to other example embodiments will be described with reference to  FIGS. 17 to 19 . Note that, in  FIGS. 17 to 19 , the illustration of the specifying unit  332  is omitted. 
     An example shown in  FIG. 17  is an example in which a part of the optical fiber cable  20  located between the utility poles  10  having the utility pole numbers B and C is broken in the configuration shown in  FIG. 13 . The fiber sensing unit  331  continues making the pulsed light enter the optical fiber cable  20  even when the optical fiber cable  20  is broken. In this way, the communication carrier station building  30  can continuously monitor the sections up to the place where the optical fiber cable is broken. 
     An example shown in  FIG. 18  is an example in which a part of the optical fiber cable  20  located between the utility poles  10  having the utility pole numbers B and C is broken in the configuration shown in  FIG. 14 . The fiber sensing units  331 A and  331 Z continues making the pulsed light enter the optical fiber cable  20  even when the optical fiber cable  20  is broken. Note that each of the utility poles  10  is connected to at least two communication carrier station buildings  30  (two communication carrier station buildings  30 A and  30 Z in  FIG. 18 ) without exception. Therefore, by having the communication carrier station buildings  30 A and  30 Z monitor the utility poles in both the directions, it is possible to form a redundant configuration by which all the sections can be continuously monitored in the case of a single failure. 
     An example shown in  FIG. 19  is an example in which a part of the optical fiber cable  20  located between the utility poles  10  having the utility pole numbers B and C is broken in the configuration shown in  FIG. 16 . The fiber sensing units  331 A and  331 Z continues making the pulsed light enter the optical fiber cable  20  even when the optical fiber cable  20  is broken. Note that, in the example shown in  FIG. 19 , a ring configuration in which the optical fiber cables  20  are connected in a ring shape is formed. Therefore, by having the one communication carrier station building  30 AZ monitor the utility poles in both the directions of the ring, it is possible to form a redundant configuration by which all the sections can be continuously monitored in the case of a single failure. 
     Although the present disclosure is explained above with reference to 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 invention. 
     The whole or part of the embodiments disclosed above can be described as, but not limited to, the following supplementary notes. 
     (Supplementary Note 1) 
     A utility pole location specifying system comprising: 
     a cable disposed in a utility pole, the cable containing a communication optical fiber; 
     a receiving unit configured to receive an optical signal containing a characteristic pattern of the utility pole from at least one communication optical fiber contained in the cable; and 
     a specifying unit configured to specify a location of the utility pole based on the characteristic pattern. 
     (Supplementary Note 2) 
     The utility pole location specifying system described in Supplementary note 1, wherein 
     each of the utility poles has s different characteristic pattern, and 
     the specifying unit specifies a location of a predetermined utility pole based on the characteristic pattern. 
     (Supplementary Note 3) 
     The utility pole location specifying system described in Supplementary note 1, wherein 
     the characteristic pattern of a utility pole changes according to a type or a state thereof, and 
     the specifying unit specifies the type or the state of the utility pole based on the characteristic pattern. 
     (Supplementary Note 4) 
     The utility pole location specifying system described in any one of Supplementary notes 1 to 3, wherein the characteristic pattern is a pattern artificially generated in the utility pole. 
     (Supplementary Note 5) 
     The utility pole location specifying system described in any one of Supplementary notes 1 to 3, wherein the characteristic pattern is a pattern non-artificially generated in the utility pole. 
     (Supplementary Note 6) 
     The utility pole location specifying system described in any one of Supplementary notes 1 to 5, wherein the specifying unit learns the characteristic pattern at a place where the utility pole is present, and specifies the location of the utility pole based on a result of the learning and the characteristic pattern contained in the optical signal received by the receiving unit. 
     (Supplementary Note 7) 
     The utility pole location specifying system described in any one of Supplementary notes 1 to 6, wherein the cable is disposed substantially perpendicular to a longitudinal direction of the utility pole. 
     (Supplementary Note 8) 
     A utility pole location specifying apparatus comprising: 
     a receiving unit configured to receive an optical signal containing a characteristic pattern of a utility pole from at least one communication optical fiber contained in a cable disposed in the utility pole; and 
     a specifying unit configured to specify a location of the utility pole based on the characteristic pattern. 
     (Supplementary Note 9) 
     The utility pole location specifying apparatus described in Supplementary note 8, wherein 
     each of the utility poles has s different characteristic pattern, and 
     the specifying unit specifies a location of a predetermined utility pole based on the characteristic pattern. 
     (Supplementary Note 10) 
     The utility pole location specifying apparatus described in Supplementary note 8, wherein 
     the characteristic pattern of a utility pole changes according to a type or a state thereof, and 
     the specifying unit specifies the type or the state of the utility pole based on the characteristic pattern. 
     (Supplementary Note 11) 
     The utility pole location specifying apparatus described in any one of Supplementary notes 8 to 10, wherein the characteristic pattern is a pattern artificially generated in the utility pole. 
     (Supplementary Note 12) 
     The utility pole location specifying apparatus described in any one of Supplementary notes 8 to 10, wherein the characteristic pattern is a pattern non-artificially generated in the utility pole. 
     (Supplementary Note 13) 
     The utility pole location specifying apparatus described in any one of Supplementary notes 8 to 12, wherein the specifying unit learns the characteristic pattern at a place where the utility pole is present, and specifies the location of the utility pole based on a result of the learning and the characteristic pattern contained in the optical signal received by the receiving unit. 
     (Supplementary Note 14) 
     The utility pole location specifying apparatus described in any one of Supplementary notes 8 to 13, wherein the cable is disposed substantially perpendicular to a longitudinal direction of the utility pole. 
     (Supplementary Note 15) 
     A utility pole location specifying method performed by a utility pole location specifying apparatus, comprising: 
     receiving an optical signal containing a characteristic pattern of a utility pole from at least one communication optical fiber contained in a cable disposed in the utility pole; and 
     specifying a location of the utility pole based on the characteristic pattern. 
     (Supplementary Note 16) 
     A non-transitory computer readable medium storing a program for causing a computer to perform: 
     a process of receiving an optical signal containing a characteristic pattern of a utility pole from at least one communication optical fiber contained in a cable disposed in the utility pole; and 
     a process of specifying a location of the utility pole based on the characteristic pattern. 
     This application is based upon and claims the benefit of priority from Japanese patent applications No. 2018-162040, filed on Aug. 30, 2018, the disclosure of which is incorporated herein in its entirety by reference. 
     REFERENCE SIGNS LIST 
     
         
           10  UTILITY POLE 
           20  OPTICAL FIBER CABLE 
           30 ,  30 A,  30 Z,  30 AZ COMMUNICATION CARRIER STATION BUILDING 
           31 ,  31 A,  31 Z COMMUNICATION EQUIPMENT 
           32 ,  32 A,  32 Z FILTER 
           33  UTILITY POLE LOCATION SPECIFYING APPARATUS 
           331 ,  331 A,  331 Z FIBER SENSING UNIT 
           332  SPECIFYING UNIT 
           34  DATA COLLECTION UNIT 
           40  COMPUTER 
           401  PROCESSOR 
           402  MEMORY 
           403  STORAGE 
           404  INPUT/OUTPUT INTERFACE 
           4041  DISPLAY APPARATUS 
           4042  INPUT APPARATUS 
           405  COMMUNICATION INTERFACE 
           50  MONITORING TERMINAL