Sensor, system, and sensing method

Abstract

An object of the present disclosure is to wire an optical fiber for sensing by a simple method.SOLUTION: The sensor of the present disclosure includes one or more optical fibers 20 and a connection portion 31 that connects the one or more optical fibers 20 to a measurement target.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to fiber optic sensing technology. [Background technology]

[0002] Optical fiber sensing methods have been known for some time, in which an optical fiber is wired in contact with an object to be measured and the state of the object is measured. For example, Non-Patent Document 1 discloses a technique for measuring the dynamic strain of an optical fiber by irradiating a test light onto the optical fiber and measuring the time change in the backscattered light. By measuring the state of the optical fiber, the state of the object to be measured can be measured.

[0003] Furthermore, studies are being conducted on treating communication optical fiber networks as sensors to measure environmental information around the cables. In particular, in order to reduce the effort and cost of laying new optical fiber for optical fiber sensing, studies are being conducted on utilizing communication optical fiber already laid in cities for sensing (see Non-Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7315009 [Non-patent literature]

[0005] [Non-Patent Document 1] “Advances in distributed vibration sensing for optical communication fiber state visualization”, Optical Fiber Technology, Vol.57, 102263. 2020 [Non-patent document 2] "Smart Engineering / Maintenance Initiatives Aiming for Operational Innovation," Business Communication 2022 Vol. 59 No. 4 [online], [Retrieved June 11, 2024], Internet<URL:https: / / www.bcm.co.jp / site / 2022 / 04 / ntt-as / 2204-ntt-as-01-06.pdf> Summary of the Invention [Problem to be solved by the invention]

[0006] However, when wiring optical fibers for sensing, the measurement results and accuracy can vary significantly depending on how they are laid and how they are contacted during wiring. For this reason, advanced technology is required to wire optical fibers for sensing, and there has been a demand for a simpler method for wiring optical fibers for sensing.

[0007] Therefore, an object of the present disclosure is to provide a simple method for wiring optical fibers for sensing. [Means for solving the problem]

[0008] To achieve the above object, the sensor, system, and sensing method of the present disclosure employ a technique in which multiple optical fibers are connected at predetermined intervals.

[0009] Specifically, the sensor of the present disclosure comprises: one or more optical fibers; and a connecting portion that connects the one or more optical fibers to an object to be measured.

[0010] The connecting portion extends in a direction different from the direction in which the one or more optical fibers extend, By connecting the ends of the connecting portions together, the measuring device may be able to be wrapped around the object to be measured.

[0011] Furthermore, the one or more optical fibers may be spirally wound around the object to be measured.

[0012] Moreover, the connecting portion is plural, The positions of the connection points between the respective ends of the plurality of connecting portions may be continuously shifted in one circumferential direction of the object to be measured.

[0013] Moreover, the connecting portion is plural, The positions of the connection points between the respective ends of the plurality of connecting portions may be discontinuously shifted in the circumferential direction of the object to be measured.

[0014] Furthermore, the rate of the spiral, which indicates the number of revolutions of the spiral per unit distance along the measurement object, may be set to a value exceeding one revolution in the distance resolution of strain distribution measurement.

[0015] Specifically, the system of the present disclosure includes: The above sensor; an optical sensing device for acquiring light scattering characteristics in an optical fiber; Equipped with.

[0016] Specifically, the sensing method of the present disclosure includes: The method includes connecting one or more optical fibers to the object to be measured using a connector that connects the one or more optical fibers to the object to be measured.

[0017] and winding the one or more optical fibers around the object to be measured by connecting the ends of the connecting portions together. and obtaining light scattering characteristics in the one or more optical fibers using a light sensing device.

[0018] The above disclosures can be combined as much as possible. [Effects of the Invention]

[0019] According to the present disclosure, optical fibers for sensing can be wired in a simple manner. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating an overview of an optical fiber sensing system according to the present disclosure. [Figure 2] 1 is a diagram illustrating an overview of optical fiber sensing using an optical fiber network according to an embodiment of the present disclosure. FIG. [Figure 3] 1 is a diagram illustrating the configuration of an optical fiber net according to an embodiment of the present disclosure. [Figure 4] FIG. [Figure 5] 10A and 10B are diagrams illustrating how the optical fiber net is wrapped around the object to be measured. [Figure 6] FIG. 1 is a view of a measurement object wrapped with an optical fiber net, viewed from the longitudinal direction of the optical fibers. [Figure 7] 10A and 10B are diagrams illustrating modified examples of how the optical fiber net is wrapped around the object to be measured. [Figure 8] 10A and 10B are diagrams illustrating modified examples of how the optical fiber net is wrapped around the object to be measured. [Figure 9] 10A and 10B are diagrams illustrating the process of wrapping an optical fiber net around a measurement object. [Figure 10] FIG. 10 is a diagram illustrating an overview of an optical fiber sensing system according to a second embodiment of the present disclosure. [Figure 11] 1A and 1B are diagrams illustrating an application example of measuring the shape of a measurement object using an optical fiber. [Figure 12] FIG. 1 illustrates a related optical fiber system. [Figure 13] FIG. 10 is a diagram illustrating an optical fiber net according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0022] [Outline of Optical Fiber Sensing] An optical fiber sensing system 500 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. The optical fiber sensing system 500 includes an optical fiber sensing device 10 and an optical fiber 20. As shown in FIG. 2, the optical fiber 20 is wound around a measurement target as an optical fiber net 30 in which multiple single-core optical fibers are connected. Note that for simplicity of illustration, FIGS. 1 and 2 show the optical fiber sensing device 10 connected to one optical fiber 20. However, in reality, multiple optical fibers 20 are connected to the optical fiber sensing device 10. However, the scope of the present disclosure is not limited to this, and multiple optical fiber sensing devices 10 may be provided corresponding to the multiple optical fibers 20, respectively. Furthermore, the scope of the present disclosure is not limited to the provision of multiple optical fibers 20, as long as one or more optical fibers 20 are provided.

[0023] Specifically, the optical fiber sensing system 500 of the present disclosure includes: an optical fiber net 30 in which a plurality of optical fibers are connected at predetermined intervals; an optical fiber sensing device (10) for acquiring light scattering characteristics in an optical fiber (20); Equipped with.

[0024] In the optical fiber sensing system 500, an optical fiber sensing device 10 is used to input test light such as pulse or CW (Continuous Wave) into an optical fiber 20, and observe the backscattered light generated within the optical fiber 20. Based on the observation results of such backscattered light, the optical fiber sensing system 500 can measure the state of an object in contact with the optical fiber 20. The optical fiber sensing device 10 functions as an "optical sensing device."

[0025] Specifically, the state of the optical fiber 20 changes when a disturbance (bending, temperature change, strain, excitation, etc.) is applied, and the state of the backscattered light also changes in accordance with this state change. In other words, by observing the state change of the backscattered light, it is possible to observe the state change of the optical fiber 20, that is, the state of the disturbance applied to the optical fiber. For this reason, the optical fiber sensing system 500 uses a method in which the optical fiber 20 is regarded as a sensor and the backscattered light is observed to measure or estimate the disturbance applied to the optical fiber 20 (bending, temperature change, strain change, vibration, etc.). Here, the disturbance applied to the optical fiber 20 includes a disturbance caused by a change in the state of an object that is in direct or indirect contact with the optical fiber 20.

[0026] In this way, the optical fiber sensing system 500 estimates not only the state of the optical fiber cable itself containing the optical fiber 20, but also the state of the environment surrounding the optical fiber 20. It is expected that this information regarding the state of the environment surrounding the optical fiber 20 will be used for various purposes (see Non-Patent Document 2).

[0027] Note that the disturbances that can be measured depend on the measurement method and the type of scattered light being observed. For example, the optical fiber sensing device 10 may be an OTDR (Optical Time-Domain Reflectometer) that inputs an optical pulse into the optical fiber 20 and extracts the scattered light. Furthermore, the measurement method for optical fiber sensing may be an OFDR (Optical Frequency Domain Reflectometry) that uses the coherence of laser light, or a BOTDR (Brilouin Optical Time Domain Reflectometry) that receives and analyzes Brillouin scattered light to continuously measure the strain of the optical fiber.

[0028] Furthermore, the optical fiber sensing system 500 may be a DAS (Distributed Antenna System) that expands the communication area by distributing radio waves received from a base station via optical cables.

[0029] Furthermore, the scattered light to be observed may be any of Rayleigh scattered light, Brillouin scattered light, Raman scattered light, etc. In particular, the optical fiber sensing device 10 may be a Raman OTDR.

[0030] In the present disclosure, an optical fiber net in which a plurality of optical fibers 20 are connected is wound around the measurement object 40, thereby making it possible to measure the shape of the measurement object 40. Specifically, by using a plurality of optical fibers 20, it is possible to measure the shape of the measurement object 40 in a manner similar to that of using a multi-core fiber. Details of measuring the shape of the measurement object 40 will be described later.

[0031] [Optical fiber network] Next, the configuration of the optical fiber net 30 according to the embodiment will be described with reference to FIG. 3. The optical fiber net 30 is configured as a net made up of three or more optical fibers 20. By covering a measurement object 40 such as a communication cable, wire rope, or pipe with the optical fiber net 30 configured in this manner, it is possible to perform optical fiber sensing of any object with standardized specifications. In other words, the optical fiber net 30 functions as a "sensor." The number of optical fibers 20 can be any number as long as it is plural, but by providing four or more, the accuracy as a sensor can be improved.

[0032] As shown in FIG. 3, the optical fiber net 30 is configured by connecting the optical fibers 20 at predetermined intervals using a plurality of connecting portions 31. Specifically, the plurality of optical fibers 20 are fixed to the connecting portions 31 so that the plurality of optical fibers 20 are arranged at predetermined intervals in the vertical direction of FIG. 3. The plurality of connecting portions 31 are provided so as to be arranged at predetermined intervals in the horizontal direction of FIG. 3. Each of the plurality of connecting portions 31 extends in a direction different from the direction in which the plurality of optical fibers 20 extend. When the optical fiber net 30 is wound around the measurement object 40, the ends (upper end, lower end) of each connecting portion 31 in the vertical direction of FIG. 3 are connected to each other. In other words, the optical fiber net 30 can be wound around the measurement object 40 by connecting the ends of the plurality of connecting portions 31 to each other.

[0033] Here, the connecting portion 31 may connect the optical fibers 20 in a bare wire state. However, the present disclosure is not limited to this, and the connecting portion 31 can connect the optical fibers 20 in various forms such as cables and tubes.

[0034] Any configuration of the connecting portion 31 and any method for fixing the optical fiber 20 to the connecting portion 31 can be considered. For example, the connecting portion 31 may be configured to mechanically hold the optical fiber 20, or the optical fiber may be bonded to the connecting portion 31.

[0035] [Wrapping of optical fiber net] Next, the manner in which the optical fiber net 30 is wound around the measurement object 40 will be described with reference to Figures 4 to 8. Figure 4 is a diagram showing the appearance of the measurement object 40. The measurement object assumed in this embodiment is a pipe, a cable, or a tower-like structure.

[0036] 5 shows an embodiment in which the optical fiber net 30 is wound in a spiral shape around the measurement object 40. The coupling portions 32 are the points where the ends of the connecting portions 31 are connected to each other. Various methods for this connection are possible, and the ends may be mechanically connected to each other, or the ends may be glued to each other. The number of coupling portions 32 may be plural, but by providing three or more coupling portions 32, the optical fiber net 30 can be suitably wound in a spiral shape around the measurement object 40.

[0037] In this embodiment, the coupling portions 32 are shifted in the circumferential direction of the measurement object 40, so that the optical fiber net 30 is wound around the measurement object 40 in a spiral shape. In other words, the multiple optical fibers form a spiral when wound around the measurement object 40. Specifically, as shown in FIG. 6 , in this embodiment, the coupling portions 32 are continuously (uniformly) shifted in a predetermined direction (one direction in the circumferential direction). In other words, the positions of the connection points between the respective ends of the multiple linking portions 31 are continuously shifted in one direction in the circumferential direction of the measurement object 40. In this way, in this embodiment, the coupling portions 32 can be shifted depending on the shape of the measurement object 40, compared to when the optical fibers 20 are embedded in the coating in advance. This allows the shape of the measurement object 40 to be measured by performing a single spiral calculation on the entire measurement object 40.

[0038] The optical fiber net 30 can also be wound around the measurement object 40 so that the spiral rate (revolutions / m) is also an arbitrary value. Here, the spiral rate may be set to a small value of approximately one revolution or less in terms of the distance resolution (m) of the strain distribution measurement in order to measure the spiral state. On the other hand, since the distortion caused by the spiral decreases as the rate increases, the rate may be set to a value that strikes a balance.

[0039] With this spiral structure, even if stress is applied to the optical fiber 20 due to shear deformation of the measurement object 40, causing twisting of the optical fiber 20, the twist can be detected and shape estimation can be performed in the same way as shape sensing using a spiral multi-core. Furthermore, if the state (shape) of the optical fiber net 30 is known, the shape of the measurement object 40 can also be known, and strain and stress can be detected by using techniques such as Brillouin measurement. When measuring temperature, it is possible to increase the spin rate to artificially increase the spatial resolution.

[0040] The scope of the present disclosure is not limited to continuously (uniformly) displacing the coupling portions 32 in a predetermined direction (one direction in the circumferential direction) as shown in Fig. 6. For example, as shown in Fig. 7, every other coupling portion 32 may be displaced in the same direction by an equal amount to form a spiral. In other words, the positions of the connection points between the ends of the multiple linking portions 31 may be displaced discontinuously in the circumferential direction of the measurement object 40. In this way, once the optical fiber net 30 is wrapped around the measurement object 40, a spiral can be easily formed around the entire object.

[0041] However, the scope of the present disclosure is not limited to winding the optical fiber net 30 in a spiral shape around the measurement object 40. For example, as shown in Fig. 8, the optical fiber net 30 may be wound around the measurement object 40 so that the coupling portion 32 is linear depending on the shape of the measurement object 40. Even with this embodiment, the state (shape) of the measurement object 40 can be suitably measured, for example, when no twisting stress is applied.

[0042] [Workflow] Next, the process of winding the optical fiber net 30 around the measurement target 40 will be described with reference to the flowchart of FIG.

[0043] Specifically, the sensing method of the present disclosure includes: a step of connecting a plurality of optical fibers 20 at predetermined intervals; a step of winding the plurality of optical fibers 20 around the measurement object 40 by connecting respective ends of a plurality of connecting portions 31 that connect the plurality of optical fibers 20; a step of acquiring light scattering characteristics in an optical fiber 20 using an optical fiber sensing device 10; Includes.

[0044] First, the user attaches the optical fiber 20 to the connecting portion 31 (step S1). As described above, the optical fiber 20 may be attached to the connecting portion 31 mechanically, or the optical fiber may be attached to the connecting portion 31 by adhesive.

[0045] The user wraps and fixes the optical fiber net 30 around the measurement target 40 (step S2).

[0046] The user uses the optical fiber 20 and the optical fiber sensing device 10 to perform desired optical fiber sensing (step S3).

[0047] [Second embodiment] Next, an optical fiber sensing system 501 according to the second embodiment will be described with reference to Fig. 10 and Fig. 11. As shown in Fig. 10, the optical fiber sensing system 501 includes a calculation processing device 50 in addition to the components included in the optical fiber sensing system 500 according to the first embodiment. The optical fiber sensing system 501 measures the shape of the measurement target 40 using an optical fiber 20. The calculation processing device 50 is configured to be able to calculate various physical quantities using the results of the shape measurement.

[0048] In the optical fiber sensing system 501, the shape of the measurement object 40 is measured using a method similar to that of shape measurement using a multi-core fiber. Specifically, the degree of distortion of each core in the cross sections of a plurality of optical fibers 20 is compared, and it can be determined that the greater the distortion, the more bent the object is. In this case, the shape of the measurement object 40 may be measured using the method disclosed in Patent Document 1.

[0049] 11 shows an application example of the measurement results of measuring the shape of the measurement object 40 using multiple optical fibers 20. First, the optical fiber sensing system 501 measures the shape of the optical fibers 20 (optical fiber net 30) attached along the shape of the measurement object 40 (step S11). The arithmetic processing device 50 may calculate the deformation of the measurement object 40 using the shape of the optical fibers 20 (step S12). The arithmetic processing device 50 may also calculate the stress distribution on the measurement object 40 based on the deformation of the measurement object 40 (step S13). Furthermore, the arithmetic processing device 50 may detect stress concentration on the measurement object 40 and identify the stress concentration location (step S14).

[0050] [effect] Next, the effects of the present disclosure will be described in comparison with a related optical fiber sensing system 500A shown in FIG.

[0051] First, when wiring optical fiber for optical fiber sensing, the measurement results and accuracy can vary significantly depending on factors such as how the fiber is laid, the contact method, and the condition of the optical fiber coating. This requires highly advanced know-how and technology for fiber wiring. In particular, optical fiber for communication is not wired for optical fiber sensing, so the measurement results and accuracy can vary significantly depending on the condition of the target communication fiber. For this reason, it is necessary to check the condition of the optical fiber for communication in advance, as this will affect the function, performance, and usability of optical fiber sensing.

[0052] In contrast, in the present disclosure, by wrapping the optical fiber net 30 around the measurement object 40, such as a communication cable, wire rope, or pipe, in a post-process, optical fiber sensing can be performed with standardized specifications for any measurement object 40. This makes it possible to suppress changes in sensing performance and accuracy due to the wiring of the optical fibers 20 and achieve consistent performance. Furthermore, by fixing the structure of the optical fiber net 30 and the type of optical fiber 20 used, it is possible to turn objects of any shape into sensors under the same conditions. Furthermore, any object already existing in the city, such as communication fibers, can be turned into a sensor medium with consistent performance.

[0053] Next, measurements using existing strain measurement optical fiber sensing cables use single-mode fibers that only measure strain, making it difficult to directly measure the shape or bending of a structure.

[0054] In contrast to this, according to the present disclosure, the optical fiber net 30 made up of a plurality of (three or more) optical fibers 20 can be used to measure the shape of the measurement target 40 in the same way as with a multi-core fiber.

[0055] 12, when a single optical fiber 20 is embedded in an optical fiber coating 30A for measurement, it is necessary to insert the optical fiber into a rigid pipe to prevent the optical fiber 20 from bending significantly, or to fill the pipe with liquid to suppress twisting of the optical fiber 20. However, depending on the shape of the measurement target 40, it may be necessary to bend the optical fiber 20 (and the pipe). Also, there are measurement targets 40 with shapes that make twisting of the optical fiber 20 unavoidable.

[0056] In such a case, it is necessary to measure the shape of the measurement object 40 and the optical fiber to compensate for the large bending or twisting of the optical fiber to be used as a sensor. However, it is difficult to perform shape measurement using a multi-core fiber to compensate for the twisting. This is because, in order to perform shape measurement, it is necessary to wire the multi-core fiber without twisting.

[0057] In contrast, according to the present disclosure, by using an optical fiber net 30 made up of multiple (three or more) optical fibers 20, particularly in a spiral structure, optical fiber sensing can be performed in a pseudo manner, similar to using a multi-core fiber, regardless of the fiber type or fiber condition, even when twists or bends occur.

[0058] [Third embodiment] The configuration of an optical fiber net 30 according to the third embodiment of the present disclosure will be described with reference to FIG.

[0059] In the above configuration, when measuring the shape of an object in detail, such as the shape of a spiral, the span length S must be equal to or greater than the fiber measurement resolution. The span length S refers to the distance along the object to be measured between the connecting parts 31.

[0060] The newly added sensor unit may not be as long as the communication fiber. For example, the sensor unit may be several meters long. In contrast, OTDR, a common sensing method for vibration and strain, cannot measure with a measurement resolution of several meters or less. For this reason, even if the optical fiber net 30 described above is wrapped around the object to be measured without considering the design of each part, it is difficult to measure with high resolution.

[0061] On the other hand, there are many cases where the shape of the object to be measured is already known, in which case there is no need to estimate the shape from sensing. Therefore, there is no need to measure the shape of the optical fiber net in detail. Also, there is no need to set the span length S to a large value, and it can be set to any value. Furthermore, the number of fibers can be multiple or one.

[0062] Even in this case, if the coupling mode of the spiral fiber is designed as follows, the effective sensing resolution of the object to be measured can be improved to be equal to or greater than the resolution of the sensing measurement method (OTDR, etc.).

[0063] Specifically, if the radius of the sensor portion to be applied is r, then the circumference is 2πr, and hereinafter the length of the circumference will be represented as R (R = 2πr). If the length of one span of the spiral is S, then the actual length L of the optical fiber 20 in one span can be expressed as L = √(R^2 + S^2). In this case, for example, for a portion where the distance along the object to be measured between the coupling portions 31 is S, the sensor portion will be made up of optical fiber 20 of length L. In other words, between the coupling portions 31 (using the distance along the object to be measured between the coupling portions 31 as a unit), L / S = √((R / S)^2 + 1) fibers will be included.

[0064] In other words, in this embodiment, the spiral rate, which indicates the number of spiral rotations per unit distance along the measurement object, is set to a value exceeding one rotation in the distance resolution of the strain distribution measurement.

[0065] Furthermore, if the length of the entire sensor unit is M, then M L / S is the fiber length. Here, if the measurement resolution is dz, then with the fiber in a normal cable, measurements can be made separately at the point M / dz. On the other hand, with the optical fiber net 30 according to this embodiment, measurements can be made at the point M L / Sdz, and the number of points that can be measured separately is L / S times larger. Because the measurement portion of M is viewed at the point M L / Sdz, the resolution is effectively reduced to S / L.

[0066] For example, if the radius of the sensor is 10 cm, the circumference will be R ≒ 0.628 m. If the span S = 1 cm, then L = √((0.628)^2 + 0.01^2) = 0.628 m. In this case, S / L = 0.0159, L / S = 62.8, and the number of points that can be separated is approximately 63 times.

[0067] For example, when measuring a 10m distance with an OTDR of 20ns (resolution 2m), only 5 points can be measured. In contrast, this embodiment makes it possible to measure approximately 314 points. In other words, since it is possible to measure a 10m object at 314 points, this is equivalent to a measurement with an effective resolution of 3.18cm (≒20×S / L=20×0.0159).

[0068] Thus, according to this embodiment, by making the span small, it is equivalent to measuring the object with higher resolution, and the object can be measured in detail using the attached sensor unit.

[0069] The device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. The program of the present disclosure is a program for causing a computer to realize each function of the device according to the present disclosure, and a program for causing a computer to execute each procedure of the method executed by the device according to the present disclosure. [Explanation of symbols]

[0070] 10: Optical fiber sensing device 20: Optical fiber 30: Optical fiber network 31:Connection part 32:Joining part 30A: Optical fiber coating 40: Measurement target 50: Processing unit 500, 501, 500A: Optical fiber sensing system

Claims

1. one or more optical fibers; a connecting portion for connecting the one or more optical fibers to a measurement object; Sensor.

2. the coupling portion extends in a direction different from the direction in which the one or more optical fibers extend, By connecting the ends of the connecting parts together, the measuring device can be wrapped around the object to be measured. The sensor of claim 1 .

3. The one or more optical fibers form a spiral shape when wrapped around the measurement object. The sensor of claim 2 .

4. The connecting portion is plural, The positions of connection points between the respective ends of the plurality of connecting portions are continuously shifted in one direction of the circumferential direction of the object to be measured. The sensor of claim 3 .

5. The connecting portion is plural, The positions of connection points between the respective ends of the plurality of connecting portions are discontinuously shifted in the circumferential direction of the object to be measured. The sensor of claim 3 .

6. a rate of the spiral, which indicates a rotation of the spiral per unit distance along the measurement object, is set to a value exceeding one rotation in the distance resolution of strain distribution measurement; The sensor of claim 3 .

7. A sensor according to any one of claims 1 to 6; an optical sensing device for acquiring light scattering characteristics in an optical fiber; Equipped with system.

8. connecting one or more optical fibers to the object to be measured using a connector that connects the one or more optical fibers to the object to be measured. Sensing method.

9. winding the one or more optical fibers around the object to be measured by connecting the ends of the connecting portions together; and acquiring light scattering characteristics in the one or more optical fibers using an optical sensing device. The sensing method according to claim 8 .

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