Optical fiber sensing system, optical fiber sensing equipment, and fracture detection method

Abstract

An optical fiber sensing system according to the present disclosure comprises: an optical fiber (10); a communication unit (21) that transmits pulse light to the optical fiber (10) and receives an optical signal from the optical fiber (10); a distal end sensing unit (22) that continuously or regularly senses the distal end position of the optical fiber (10) on the basis of the optical signal received from the optical fiber (10); and a breakage sensing unit (23) that determines that the optical fiber (10) has broken if the difference between the distal end position detected by the distal end sensing unit (22) and the initial value of the distal end position exceeds a prescribed value.

Description

Technical Field

[0001] The present disclosure relates to an optical fiber sensing system, an optical fiber sensing device, and a break detection method.

Background Art

[0002] In recent years, a technology called optical fiber sensing that uses an optical fiber as a sensor has attracted attention. Optical fiber sensing is mainly realized by an optical fiber and an optical fiber sensing device connected to the optical fiber.

[0003] The optical fiber sensing device transmits pulsed light to the optical fiber and receives the backscattered light with respect to the pulsed light from the optical fiber as an optical signal. Based on the optical signal, the optical fiber sensing device detects vibrations, sounds, temperature changes, etc. generated in the optical fiber, or identifies the positions where these vibrations, etc. occur.

[0004] For example, when the optical fiber is laid in an area or object where an abnormality is to be detected, the optical fiber sensing device can further detect an abnormality of the monitoring object or identify the position where the abnormality is detected based on the detected vibrations, etc.

[0005] However, when the optical fiber breaks for some reason, the optical fiber sensing device cannot obtain data of positions ahead of the break point. Therefore, if the optical fiber sensing device has detected an abnormality based on data of positions ahead of the break point, it will no longer be able to detect an abnormality thereafter.

[0006] Therefore, recently, technologies for detecting a break in an optical fiber have been proposed. For example, Patent Document 1 describes a technique for detecting a disconnection such as a break in an optical fiber if Fresnel reflected light is detected when test light is incident on the optical fiber.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2001-324358 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, the technology described in Patent Document 1 is a technology for detecting Fresnel reflected light, and therefore it is considered possible to detect the far end position of the optical fiber. However, many optical fibers, especially those used for sensing, are designed with a free end at the far end.

[0009] Therefore, as with the technology described in Patent Document 1, simply detecting the position of the far end of the optical fiber is unlikely to detect breakage in optical fibers where the far end is a free end.

[0010] Therefore, in view of the above-mentioned problems, the purpose of this disclosure is to provide an optical fiber sensing system, an optical fiber sensing device, and a fracture detection method that are capable of detecting the breakage of an optical fiber. [Means for solving the problem]

[0011] One embodiment of the optical fiber sensing system is: Optical fiber and A communication unit that transmits pulsed light to the optical fiber and receives optical signals from the optical fiber, A far-end detection unit that continuously or periodically detects the far-end position of the optical fiber based on the optical signal received from the optical fiber, The system includes a break detection unit that determines that the optical fiber has broken when the difference between the far-end position detected by the far-end detection unit and the initial value of the far-end position exceeds a predetermined value.

[0012] One embodiment of an optical fiber sensing device is: A communication unit that transmits pulsed light to an optical fiber and receives optical signals from the optical fiber, A far-end detection unit that continuously or periodically detects the far-end position of the optical fiber based on the optical signal received from the optical fiber, The system includes a break detection unit that determines that the optical fiber has broken when the difference between the far-end position detected by the far-end detection unit and the initial value of the far-end position exceeds a predetermined value.

[0013] One method for detecting fracture is: A method for detecting breakage using optical fiber sensing equipment, A communication step of transmitting pulsed light to an optical fiber and receiving an optical signal from the optical fiber, A far-end detection step in which the far-end position of the optical fiber is detected continuously or periodically based on the optical signal received from the optical fiber, The method includes a break detection step in which it is determined that the optical fiber has broken if the difference between the far-end position detected by the far-end detection step and the initial value of the far-end position exceeds a predetermined value. [Effects of the Invention]

[0014] According to the above-described embodiment, the effect is obtained that an optical fiber sensing system, optical fiber sensing equipment, and fracture detection method capable of detecting the breakage of an optical fiber can be provided. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows an example configuration of the optical fiber sensing system according to Embodiment 1. [Figure 2] This figure shows an image illustrating an example of the operation of the far-end detection unit and the fracture detection unit according to Embodiment 1. [Figure 3] This figure shows an example of a method for detecting the far end position of an optical fiber using a far end detection unit according to Embodiment 1. [Figure 4]It is a diagram showing another example of a method for detecting the distal end position of an optical fiber by the distal end detection unit according to Embodiment 1. [Figure 5] It is a flowchart showing an example of a schematic operation flow of the optical fiber sensing system according to Embodiment 1. [Figure 6] It is a diagram showing a configuration example of the optical fiber sensing system according to Embodiment 2. [Figure 7] It is a flowchart showing an example of a schematic operation flow of the optical fiber sensing system according to Embodiment 2. [Figure 8] It is a block diagram showing an example of the hardware configuration of a computer that realizes the optical fiber sensing device according to Embodiments 1 and 2.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description and drawings are appropriately omitted and simplified for clarity of explanation. Also, in the following drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted as necessary. In addition, the specific numerical values shown below are merely examples for facilitating the understanding of the present disclosure and are not limited thereto.

[0017] <Embodiment 1> First, referring to FIG. 1, a configuration example of the optical fiber sensing system according to Embodiment 1 of the present embodiment will be described. As shown in FIG. 1, the optical fiber sensing system according to Embodiment 1 of the present embodiment includes an optical fiber 10 and an optical fiber sensing device 20.

[0018] The optical fiber sensing device 20 is implemented, for example, by a DFOS (Distributed Fiber Optic Sensing) device and includes a communication unit 21, a far-end detection unit 22, and a break detection unit 23. Note that the communication unit 21, the far-end detection unit 22, and the break detection unit 23 are not limited to being provided in the same device as shown in Figure 1, but may be provided in separate devices. Furthermore, the far-end detection unit 22 and the break detection unit 23 may be provided on the cloud.

[0019] One end of the optical fiber 10 is connected to the communication unit 21 of the optical fiber sensing device 20, and the other end is a free end. The optical fiber 10 is laid, for example, in an area or object where anomalies are to be detected. Alternatively, the optical fiber 10 may be laid in the form of an optical fiber cable, which is constructed by covering one or more optical fibers 10.

[0020] The communication unit 21 transmits pulsed light to the optical fiber 10. As the pulsed light is transmitted through the optical fiber 10, backscattered light is generated. The communication unit 21 receives this backscattered light from the optical fiber 10 as an optical signal.

[0021] The far-end detection unit 22 continuously or periodically detects the far-end position of the optical fiber 10 based on the optical signal received from the optical fiber 10 by the communication unit 21. The method for detecting the far-end position of the optical fiber 10 will be described later.

[0022] The break detection unit 23 holds an initial value for the far end position of the optical fiber 10. When the far end position of the optical fiber 10 is detected by the far end detection unit 22, the break detection unit 23 determines whether the difference between the detected far end position and the initial value of the far end position exceeds a predetermined value. If the difference exceeds the predetermined value, the break detection unit 23 determines that the optical fiber 10 has broken.

[0023] Furthermore, the predetermined value held by the fracture detection unit 23 is preferably set considering the detection error of the far end position detected by the far end detection unit 22. While the specific numerical value of the predetermined value is assumed to be, for example, about 1 m, it is not limited to this.

[0024] Now, referring to Figure 2, an image of the operation example of the far-end detection unit 22 and the fracture detection unit 23 according to this embodiment 1 will be described. Referring to Figure 2, in the initial state, the far end position of the optical fiber 10 is assumed to be 40 km from the optical fiber sensing device 20 (communication unit 21). Therefore, the break detection unit 23 is assumed to maintain the initial value of "40 km" for the far end position of the optical fiber 10.

[0025] In this environment, suppose the optical fiber 10 breaks for some reason at a location 20 km from the optical fiber sensing device 20 (communication unit 21). In this case, the far-end detection unit 22 detects the far-end position of the optical fiber 10 at "20 km" through continuous or periodic detection.

[0026] The break detection unit 23 then calculates "20km" as the difference between the far-end position "20km" detected by the far-end detection unit 22 and the initial value of the far-end position "40km". This difference of "20km" exceeds a predetermined value that is expected to be set to approximately 1m, as described above. Therefore, the break detection unit 23 determines that the optical fiber 10 has broken at a location 20km from the optical fiber sensing device 20 (communication unit 21).

[0027] Here, we will explain in detail how the far-end detection unit 22 detects the far-end position of the optical fiber 10. Two methods will be described below. (1) Method 1 The far-end detection unit 22 can determine the location where the optical signal originated (the distance of the optical fiber 10 from the optical fiber sensing device 20 (communication unit 21)) based on the time difference between the time when the communication unit 21 transmitted pulsed light to the optical fiber 10 and the time when the communication unit 21 received the optical fiber 10.

[0028] Furthermore, when vibration occurs in the optical fiber 10, the characteristics (e.g., wavelength) of the optical signal transmitted through the optical fiber 10 change. Therefore, the far-end detection unit 22 can detect vibrations occurring in the optical fiber 10 and the intensity of those vibrations by analyzing the characteristics of the optical signal received by the communication unit 21.

[0029] Therefore, in the first method, the far-end detection unit 22 acquires data as shown in Figure 3, so-called waterfall data. The waterfall data represents the time course of vibration intensity within a specified time at each distance of the optical fiber 10 from the optical fiber sensing device 20 (communication unit 21). More specifically, the waterfall data represents the vibration intensity acquired at each sampling time (e.g., 0.24 seconds) for each distance of the optical fiber 10 over a specified time (e.g., 30 seconds), represented by color. In Figure 3, the horizontal axis represents the distance of the optical fiber 10 from the optical fiber sensing device 20 (communication unit 21), and the vertical axis represents the time course of vibration intensity at that distance.

[0030] As shown in Figure 3, the waterfall data indicates that the data beyond the far end of the optical fiber 10 shows a significant difference in vibration intensity compared to the data up to the position before the far end, due to the influence of random noise occurring beyond the far end. Therefore, the far-end detection unit 22 determines that the boundary where a significant difference in vibration intensity appears is the far-end position of the optical fiber 10.

[0031] (2) Second method In the second method, the far-end detection unit 22 first acquires waterfall data as shown in Figure 4, similar to the first method.

[0032] Next, the far-end detection unit 22 performs convolution on the waterfall data and then displays only the vibration intensities that are above a vibration intensity threshold, thereby obtaining residual data (Residual_mv).

[0033] Next, the far-end detection unit 22 calculates a vibration score for each distance of the optical fiber 10 from the optical fiber sensing device 20 (communication unit 21) based on the residual data. The vibration score is the sum of the vibration intensity values ​​within a specified time at each distance of the optical fiber 10. More specifically, the vibration score is the sum of the vibration intensity values ​​acquired at each sampling time (e.g., 0.24 seconds) over a specified time (e.g., 30 seconds) at each distance of the optical fiber 10. For example, if the specified time is 30 seconds, the sampling time is 0.24 seconds, and the vibration intensity within the specified time at a certain distance is constant at 100, then the vibration score at that distance will be 12,500 (=100*(30 / 0.24)=100*125).

[0034] Next, the far-end detection unit 22 calculates the difference in vibration scores (Vibration_score_diff) between the vibration score at a given distance and the vibration score at an adjacent distance for each distance of the optical fiber 10 from the optical fiber sensing device 20 (communication unit 21). While it is assumed that the adjacent distance refers to the distance adjacent to the optical fiber sensing device 20 (communication unit 21), it is not limited to this.

[0035] Subsequently, the far-end detection unit 22 sequentially checks the score difference in the positive direction (to the right in the figure) starting from the position where the distance of the optical fiber 10 from the optical fiber sensing device 20 (communication unit 21) is 0. The far-end detection unit 22 then determines the position where the score difference exceeds the score difference threshold as the far-end position of the optical fiber 10.

[0036] Next, with reference to Figure 5, an example of the general operation flow of the optical fiber sensing system according to this embodiment 1 will be described.

[0037] As shown in Figure 5, when the timing for detecting the far end position of the optical fiber 10 is reached, either continuously or periodically, the communication unit 21 first transmits pulsed light to the optical fiber 10 (step S11), and receives the backscattered light from the optical fiber 10 as an optical signal (step S12).

[0038] Next, the far-end detection unit 22 detects the far-end position of the optical fiber 10 based on the optical signal received from the optical fiber 10 by the communication unit 21 (step S13). This detection can be performed using either the first or second method described above.

[0039] Next, the fracture detection unit 23 determines whether the difference between the far end position detected by the far end detection unit 22 and the initial value of the far end position exceeds a predetermined value (step S14).

[0040] In step S14, if the above-mentioned difference is less than or equal to a predetermined value (No in step S14), the break detection unit 23 determines that the optical fiber 10 is not broken and returns to the process in step S11. The process in step S11 starts when the next detection timing for the far end position of the optical fiber 10 occurs. However, it is not limited to this, and the transmission of pulsed light and the reception of optical signals will continue thereafter, and if step S14 is No, the process may return to the process in step S13.

[0041] On the other hand, in step S14, if the above-mentioned difference exceeds a predetermined value (Yes in step S14), the break detection unit 23 determines that the optical fiber 10 has broken (step S15) and terminates the process.

[0042] As described above, according to this embodiment 1, the communication unit 21 transmits pulsed light to the optical fiber 10 and receives the backscattered light from the optical fiber 10 as an optical signal. The far-end detection unit 22 detects the far-end position of the optical fiber 10 based on the optical signal. The break detection unit 23 determines that the optical fiber 10 has broken if the difference between the detected far-end position and the initial value of the far-end position exceeds a predetermined value. This makes it possible to detect the break of the optical fiber 10. In particular, it is possible to detect the break even in optical fibers 10 where the far end is a free end.

[0043] <Embodiment 2> Next, with reference to Figure 6, an example configuration of the optical fiber sensing system according to this second embodiment will be described.

[0044] As shown in Figure 6, the optical fiber sensing system according to this second embodiment differs from the configuration shown in Figure 1 of the first embodiment described above in that the optical fiber sensing device 20 is equipped with an alarm output unit 24.

[0045] The alarm output unit 24 outputs an alarm when the break detection unit 23 determines that the optical fiber 10 has broken. For example, the alarm output method by the alarm output unit 24 may be to display a screen such as a GUI (Graphical User Interface) screen indicating that the optical fiber 10 has broken on a display or monitor (not shown). Alternatively, the alarm output method may be to output an audio message indicating that the optical fiber 10 has broken from a speaker (not shown).

[0046] Furthermore, in Embodiment 1 described above, the process was terminated if it was determined that the optical fiber 10 had broken. In contrast, in Embodiment 2, the detection of breakage of the optical fiber 10 is continued while updating the initial value of the far end position of the optical fiber 10.

[0047] To this end, the break detection unit 23 determines whether or not the optical fiber 10 has broken, and regardless of whether or not it has been determined to be broken, updates the initial value of the far end position of the optical fiber 10 with the value of the far end position detected by the far end detection unit 22.

[0048] After the initial value of the far end position of the optical fiber 10 is updated, when the far end position of the optical fiber 10 is detected by the far end detection unit 22, the break detection unit 23 determines whether the optical fiber 10 has broken based on whether the difference between the detected far end position and the updated initial value of the far end position exceeds a predetermined value.

[0049] Next, with reference to Figure 7, an example of the general operation flow of the optical fiber sensing system according to this second embodiment will be described.

[0050] As shown in Figure 7, first, the same process as steps S11 to S14 in Figure 5 of Embodiment 1 described above is performed, specifically steps S21 to S24.

[0051] In step S24, if the difference between the far-end position detected by the far-end detection unit 22 and the initial value of the far-end position is less than or equal to a predetermined value (No. in step S24), the break detection unit 23 determines that the optical fiber 10 is not broken, and then updates the initial value of the far-end position of the optical fiber 10 with the value of the far-end position detected by the far-end detection unit 22 (step S27). After that, the process returns to step S21.

[0052] On the other hand, in step S24, if the above-mentioned difference exceeds a predetermined value (Yes in step S24), the break detection unit 23 determines that the optical fiber 10 has broken (step S25), and the alarm output unit 24 outputs an alarm (step S26). Subsequently, in step S27, the break detection unit 23 updates the initial value of the far end position of the optical fiber 10 and returns to the process in step S21.

[0053] If the process returns to step S21, the process of step S21 will start when the next detection timing for the far end position of the optical fiber 10 occurs. However, this is not limited to this, and the transmission of pulsed light and the reception of optical signals will continue thereafter, and if the process of step S27 is completed, the process may return to step S23.

[0054] As described above, according to this second embodiment, the alarm output unit 24 outputs an alarm when the break detection unit 23 determines that the optical fiber 10 has broken. This makes it possible to notify external users (for example, administrators who manage the optical fiber 10) that the optical fiber 10 has broken.

[0055] Furthermore, according to this second embodiment, after determining whether the optical fiber 10 has broken, the break detection unit 23 updates the initial value of the far-end position of the optical fiber 10 with the value of the far-end position detected by the far-end detection unit 22. After this update, when the far-end position of the optical fiber 10 is detected by the far-end detection unit 22, the break detection unit 23 determines whether the optical fiber 10 has broken based on whether the difference between the detected far-end position and the updated initial value of the far-end position exceeds a predetermined value. This allows for continuous detection of breaks in the optical fiber 10.

[0056] <Hardware configuration of optical fiber sensing equipment according to the embodiment> Next, with reference to Figure 8, an example of the hardware configuration of a computer 90 that implements the optical fiber sensing device 20 according to the above-described embodiments 1 and 2 will be explained.

[0057] As shown in Figure 9, the computer 90 includes a processor 91, memory 92, storage 93, input / output interface (I / F) 94, and communication interface (Communication I / F) 95. The processor 91, memory 92, storage 93, input / output interface 94, and communication interface 95 are connected to each other by data transmission paths for sending and receiving data.

[0058] The processor 91 is a processing unit such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The memory 92 is a type of memory such as RAM (Random Access Memory) or ROM (Read Only Memory). The storage 93 is a storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or memory card. The storage 93 may also be a type of memory such as RAM or ROM.

[0059] The storage 93 stores a program. This program, when loaded into a computer, includes a set of instructions (or software code) that causes the computer 90 to perform one or more functions of the optical fiber sensing device 20 described above. The components of the optical fiber sensing device 20 described above may also be realized by the processor 91 loading and executing the program stored in the storage 93. Furthermore, the storage and retention functions of the optical fiber sensing device 20 described above may be realized by memory 92 or storage 93.

[0060] Furthermore, the programs described above may be stored on non-temporary computer-readable media or tangible storage media. Examples, but not limited to, include RAM, ROM, flash memory, SSD or other memory technologies, CD (Compact Disc)-ROM, DVD (Digital Versatile Disc), Blu-ray® disc or other optical disc storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices. The programs may also be transmitted over temporary computer-readable media or communication media. Examples, but not limited to, include electrical, optical, acoustic or other forms of propagating signals.

[0061] The input / output interface 94 is connected to a display device 941, an input device 942, a sound output device 943, and the like. The display device 941 is a device that displays a screen corresponding to the 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 receives operator input, such as a keyboard, mouse, and touch sensor. The display device 941 and the input device 942 may be integrated and implemented as a touch panel. The sound output device 943 is a device that outputs sound corresponding to the acoustic data processed by the processor 91, such as a speaker.

[0062] The communication interface 95 transmits and receives data to and from external devices. For example, the communication interface 95 communicates with external devices via a wired communication path or a wireless communication path.

[0063] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be understood by those skilled in the art within the scope of the present disclosure.

[0064] For example, some or all of the embodiments described above may also be described as follows, but are not limited to the following. (Note 1) Optical fiber and A communication unit that transmits pulsed light to the optical fiber and receives optical signals from the optical fiber, A far-end detection unit that continuously or periodically detects the far-end position of the optical fiber based on the optical signal received from the optical fiber, The system includes a break detection unit that determines that the optical fiber has broken if the difference between the far-end position detected by the far-end detection unit and the initial value of the far-end position exceeds a predetermined value. Optical fiber sensing system. (Note 2) After determining whether the optical fiber has broken, the break detection unit updates the initial value of the far end position with the value of the far end position detected by the far end detection unit. The optical fiber sensing system described in Appendix 1. (Note 3) The break detection unit, after updating the initial value of the far end position, determines whether the optical fiber has broken if the far end position is detected by the far end detection unit, depending on whether the difference between the detected far end position and the updated initial value of the far end position exceeds a predetermined value. The optical fiber sensing system described in Appendix 2. (Note 4) The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, data representing the time course of vibration intensity within a specified time at each distance from the communication unit to the optical fiber is acquired. Based on the above data, the far end position of the optical fiber is detected. The optical fiber sensing system described in Appendix 1. (Note 5) The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, a score is calculated by accumulating the vibration intensity values ​​within a specified time at each distance from the communication unit to the optical fiber. For each distance from the communication unit to the optical fiber, the difference between the score at that distance and the score at a distance adjacent to that distance is calculated. Based on the score difference, the far end position of the optical fiber is detected. The optical fiber sensing system described in Appendix 1. (Note 6) The system further includes an alarm output unit that outputs an alarm when the break detection unit determines that the optical fiber has broken. The optical fiber sensing system described in Appendix 1. (Note 7) A communication unit that transmits pulsed light to an optical fiber and receives optical signals from the optical fiber, A far-end detection unit that continuously or periodically detects the far-end position of the optical fiber based on the optical signal received from the optical fiber, The system includes a break detection unit that determines that the optical fiber has broken if the difference between the far-end position detected by the far-end detection unit and the initial value of the far-end position exceeds a predetermined value. Optical fiber sensing equipment. (Note 8) After determining whether the optical fiber has broken, the break detection unit updates the initial value of the far end position with the value of the far end position detected by the far end detection unit. Optical fiber sensing equipment as described in Appendix 7. (Note 9) The break detection unit, after updating the initial value of the far end position, determines whether the optical fiber has broken if the far end position is detected by the far end detection unit, depending on whether the difference between the detected far end position and the updated initial value of the far end position exceeds a predetermined value. Optical fiber sensing equipment as described in Appendix 8. (Note 10) The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, data representing the time course of vibration intensity within a specified time at each distance from the communication unit to the optical fiber is acquired. Based on the above data, the far end position of the optical fiber is detected. Optical fiber sensing equipment as described in Appendix 7. (Note 11) The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, a score is calculated by accumulating the vibration intensity values ​​within a specified time at each distance from the communication unit to the optical fiber. For each distance from the communication unit to the optical fiber, the difference between the score at that distance and the score at a distance adjacent to that distance is calculated. Based on the score difference, the far end position of the optical fiber is detected. Optical fiber sensing equipment as described in Appendix 7. (Note 12) The system further includes an alarm output unit that outputs an alarm when the break detection unit determines that the optical fiber has broken. Optical fiber sensing equipment as described in Appendix 7. (Note 13) A method for detecting breakage using optical fiber sensing equipment, A communication step of transmitting pulsed light to an optical fiber and receiving an optical signal from the optical fiber, A far-end detection step in which the far-end position of the optical fiber is detected continuously or periodically based on the optical signal received from the optical fiber, The method includes a break detection step in which it is determined that the optical fiber has broken if the difference between the far-end position detected by the far-end detection step and the initial value of the far-end position exceeds a predetermined value, Fracture detection method. (Note 14) In the break detection step, after determining whether the optical fiber has broken, the initial value of the far end position is updated with the value of the far end position detected in the far end detection step. The fracture detection method described in Appendix 13. (Note 15) In the break detection step, if the far end position is detected by the far end detection step after the initial value of the far end position has been updated, it is determined whether the optical fiber has broken or not, depending on whether the difference between the detected far end position and the updated initial value of the far end position exceeds a predetermined value. The fracture detection method described in Appendix 14. (Note 16) In the aforementioned far-end detection step, Based on the optical signal received from the optical fiber, data representing the time course of vibration intensity within a specified time at each distance from the communication unit to the optical fiber is acquired. Based on the above data, the far end position of the optical fiber is detected. The fracture detection method described in Appendix 13. (Note 17) In the aforementioned far-end detection step, Based on the optical signal received from the optical fiber, a score is calculated by accumulating the vibration intensity values ​​within a specified time at each distance from the communication unit to the optical fiber. For each distance from the communication unit to the optical fiber, the difference between the score at that distance and the score at a distance adjacent to that distance is calculated. Based on the score difference, the far end position of the optical fiber is detected. The fracture detection method described in Appendix 13. (Note 18) The method further includes an alarm output step which outputs an alarm if the break detection step determines that the optical fiber has broken. The fracture detection method described in Appendix 13. [Explanation of Symbols]

[0065] 10 Optical Fibers 20 Fiber Optic Sensing Equipment 21 Communications Department 22 Far-end detection unit 23 Fracture detection unit 24 Alarm output section 90 Computer 91 processors 92 memory 93 Storage 94 Input / Output Interfaces 941 Display device 942 Input device 943 Sound output device 95 Communication Interface

Claims

1. Optical fiber and A communication unit that transmits pulsed light to the optical fiber and receives optical signals from the optical fiber, A far-end detection unit that continuously or periodically detects the far-end position of the optical fiber based on the optical signal received from the optical fiber, The system includes a break detection unit that determines that the optical fiber has broken when the difference between the far-end position detected by the far-end detection unit and the initial value of the far-end position exceeds a predetermined value, The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, a score is calculated by accumulating the vibration intensity values ​​within a specified time at each distance from the communication unit to the optical fiber. For each distance from the communication unit to the optical fiber, the difference between the score at that distance and the score at a distance adjacent to that distance is calculated. Based on the score difference, the far end position of the optical fiber is detected. Optical fiber sensing system.

2. After determining whether the optical fiber has broken, the break detection unit updates the initial value of the far end position with the value of the far end position detected by the far end detection unit. The optical fiber sensing system according to claim 1.

3. The break detection unit, after updating the initial value of the far end position, determines whether the optical fiber has broken if the far end position is detected by the far end detection unit, depending on whether the difference between the detected far end position and the updated initial value of the far end position exceeds a predetermined value. The optical fiber sensing system according to claim 2.

4. A communication unit that transmits pulsed light to an optical fiber and receives optical signals from the optical fiber, A far-end detection unit that continuously or periodically detects the far-end position of the optical fiber based on the optical signal received from the optical fiber, The system includes a break detection unit that determines that the optical fiber has broken when the difference between the far-end position detected by the far-end detection unit and the initial value of the far-end position exceeds a predetermined value, The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, a score is calculated by accumulating the vibration intensity values ​​within a specified time at each distance from the communication unit to the optical fiber. For each distance from the communication unit to the optical fiber, the difference between the score at that distance and the score at a distance adjacent to that distance is calculated. Based on the score difference, the far end position of the optical fiber is detected. Optical fiber sensing equipment.

5. After determining whether the optical fiber has broken, the break detection unit updates the initial value of the far end position with the value of the far end position detected by the far end detection unit. The optical fiber sensing device according to claim 4.

6. The break detection unit, after updating the initial value of the far end position, determines whether the optical fiber has broken if the far end position is detected by the far end detection unit, depending on whether the difference between the detected far end position and the updated initial value of the far end position exceeds a predetermined value. The optical fiber sensing device according to claim 5.

7. The aforementioned far-end detection unit is Based on the optical signal received from the optical fiber, data representing the time course of vibration intensity within a specified time at each distance from the communication unit to the optical fiber is acquired. Based on the above data, the far end position of the optical fiber is detected. The optical fiber sensing device according to claim 4.

8. The system further includes an alarm output unit that outputs an alarm when the break detection unit determines that the optical fiber has broken. The optical fiber sensing device according to claim 4.

9. A method for detecting breakage using optical fiber sensing equipment, A communication step of transmitting pulsed light to an optical fiber and receiving an optical signal from the optical fiber, A far-end detection step in which the far-end position of the optical fiber is detected continuously or periodically based on the optical signal received from the optical fiber, The method includes a break detection step in which it is determined that the optical fiber has broken if the difference between the far-end position detected by the far-end detection step and the initial value of the far-end position exceeds a predetermined value, In the aforementioned far-end detection step, Based on the optical signal received from the optical fiber, a score is calculated by accumulating the vibration intensity values ​​within a specified time at each distance from the optical fiber sensing device to the optical fiber. For each distance of the optical fiber from the optical fiber sensing device, the difference between the score at that distance and the score at a distance adjacent to that distance is calculated. Based on the score difference, the far end position of the optical fiber is detected. Fracture detection method.

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