Analysis system, analysis device, and analysis method

Abstract

This technology provides high-precision analysis of the shape of optical fibers, even when they are twisted. [Solution] A multi-core optical fiber cable 10 comprises multiple optical fibers, each containing a multi-core fiber with four or more cores in addition to the center, and the position of each optical fiber is fixed relative to the other optical fibers; a strain distribution measuring device 30 for measuring the strain at each point in the longitudinal direction of the cores of the multiple optical fibers; and an analysis device 40 for analyzing the shape of the multiple optical fibers from the strain at each point. The analysis device 40 determines the bending strain included in the strain from the strain at each point of the core of the multi-core fiber measured when the multi-core optical fiber cable is installed on a linear structure 100, calculates the curvature and bending angle at each point of the core from the bending strain, calculates the spin rate at each point of the core from the bending strain, and analyzes the shape of the multi-core fiber based on the calculation results.

Description

Technical Field

[0001] The present disclosure relates to an analysis system, an analysis device, and an analysis method.

Background Art

[0002] There is a technique for analyzing the longitudinal shape of an optical fiber by measuring the longitudinal strain distribution of the optical fiber (see Non-Patent Documents 1 to 3). Further, there is a technique for analyzing the shape of a linear structure on which an optical fiber is installed based on the analysis result (see Patent Document 1).

[0003] In Patent Document 1, the strain distribution of an optical fiber is measured using a multi-core fiber (MCF) having a plurality of cores. However, torsion is applied to the cores due to bending of the MCF, and this torsion has a great influence on the measurement accuracy. It is inevitable that torsion is applied when installing the optical fiber, and it is extremely difficult to know in advance the amount of applied torsion.

[0004] Therefore, in Non-Patent Documents 1 and 2, the MCF is arranged in a spiral shape to measure the torsion of the cores in advance, and the strain distribution is measured on the premise that the cores have torsion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

[0007] However, pre-applying torsion to MCF requires specialized equipment in the MCF manufacturing process, which significantly impacts yield and cost. Furthermore, it is difficult to install MCF in linear structures while maintaining that torsion.

[0008] This disclosure is made in view of the above circumstances and aims to provide a technology that can analyze the shape of an optical fiber with high precision even when the optical fiber is twisted. [Means for solving the problem]

[0009] An analysis system according to one aspect of the present disclosure comprises a multi-core optical fiber cable comprising a plurality of optical fibers, each containing a multi-core fiber with four or more cores in addition to the center, wherein the position of each optical fiber is fixed relative to the optical fibers; a strain distribution measuring device for measuring the strain at each point in the longitudinal direction of the cores of the plurality of optical fibers; and an analysis device for analyzing the shape of the plurality of optical fibers from the strain at each point. The analysis device determines the bending strain included in the strain from the strain at each point of the core of the multi-core fiber measured when the multi-core optical fiber cable is installed in a linear structure, calculates the curvature and bending angle at each point of the core from the bending strain, calculates the spin rate at each point of the core from the bending strain, and analyzes the shape of the multi-core fiber based on the calculation results.

[0010] An analysis apparatus according to one aspect of the present disclosure determines the bending strain contained in the strain measured at each point of a multicore fiber having four or more cores in addition to the center when the multicore fiber is installed in a linear structure, calculates the curvature and bending angle at each point of the core from the bending strain, calculates the spin rate at each point of the core from the bending strain, and analyzes the shape of the multicore fiber based on the calculation results.

[0011] An analysis method according to one aspect of the present disclosure is an analysis method performed by an analysis device, in which the bending strain included in the strain is determined from the strain measured at each point of the core when a multicore fiber having four or more cores in addition to the center is installed in a linear structure, the curvature and bending angle at each point of the core are calculated from the bending strain, the spin rate at each point of the core is calculated from the bending strain, and the shape of the multicore fiber is analyzed based on the calculation results. [Effects of the Invention]

[0012] According to this disclosure, a technology is available that can analyze the shape of an optical fiber with high precision even when the optical fiber is twisted. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows an example of the configuration of the analysis system. [Figure 2] Figure 2 shows a cross-section of a multi-core optical fiber cable. [Figure 3] Figure 3 is a schematic diagram of the measurement system for a multi-core optical fiber cable. [Figure 4A] Figure 4A shows the measurement results of the strain distribution of the MCF under bending conditions. [Figure 4B] Figure 4B shows the measurement results of the strain distribution of the MCF under bending conditions. [Figure 5A] Figure 5A shows the measurement results of the strain distribution of the MCF in the non-bending state. [Figure 5B] Figure 5B shows the measurement results of the strain distribution of the MCF in the non-bending state. [Figure 6] Figure 6 shows the distribution of bending strain in the core. [Figure 7] Figure 7 shows an example of the core's torsional angle θ. [Figure 8] Figure 8 shows the calculated value of the core's torsional angle θ. [Figure 9] Figure 9 shows a method for measuring the shape of optical fibers and linear structures. [Figure 10] Figure 10 is an explanatory diagram of distance r, angle α, bending angle β, and torsional angle θ. [Figure 11] Figure 11 shows the verification results of the MCF shape measurement. [Figure 12] Figure 12 shows an example of the hardware configuration of the analysis device. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described below with reference to the drawings.

[0015] [Summary of this disclosure] This disclosure describes a technique for analyzing the three-dimensional shape and shape changes of a linear structure in which an optical fiber is installed, by measuring the strain distribution in the longitudinal direction of the optical fiber.

[0016] In particular, by determining the amount of torsion applied to the core of the MCF due to bending, calculating the spin rate from that torsion amount, and reflecting that spin rate in the shape measurement of the MCF, the accuracy of shape measurement of the MCF and linear structures is improved.

[0017] [Configuration of the analysis system] Figure 1 shows an example of the configuration of the analysis system 1 according to this embodiment.

[0018] Analysis System 1 is a system that analyzes the three-dimensional shape and shape changes of the linear structure 100 by installing a multi-core optical fiber cable 10 on the linear structure 100 to be analyzed, measuring the strain distribution generated in the optical fibers 11 within the multi-core optical fiber cable 10, and thereby analyzing the three-dimensional shape and shape changes of the optical fibers 11 in the longitudinal direction.

[0019] Linear structures 100 refer to structures on which various cables such as electricity, gas, water, and telecommunications cables are laid. Specifically, these include ducts, conduits, and tunnels installed on land, underground, in bridges, underwater, etc.

[0020] The analysis system 1 comprises a multi-core optical fiber cable 10, an optical switch 20, a strain distribution measuring device 30, and an analysis device 40.

[0021] The multi-core optical fiber cable 10 comprises four optical fibers 11. Each optical fiber 11 is arranged and fixed in parallel and on the same straight line in the short direction of the multi-core optical fiber cable 10.

[0022] The optical switch 20 is connected to the end of each optical fiber 11 in the multi-core optical fiber cable 10 and is a device that selects the desired optical fiber 11 from among the four optical fibers 11.

[0023] The strain distribution measuring device 30 is a device that measures the strain distribution in the longitudinal direction of the optical fiber 11 selected by the optical switch 20 (the strain at each point in the longitudinal direction of the core of the optical fiber 11). The strain distribution measuring device 30 is, for example, an OTDR (Optical Time Domain Reflectometer) or a B-OTDR (Brillouin Optical Time Domain Reflectometer).

[0024] The analysis device 40 analyzes the three-dimensional shape and shape changes of the optical fiber 11 in the longitudinal direction from the strain distribution of the optical fiber 11 measured by the strain distribution measuring device 30, and analyzes the three-dimensional shape and shape changes of the linear structure 100 from the analysis results.

[0025] [Configuration of a multi-core optical fiber cable] Figure 2 shows a cross-section of the multi-core optical fiber cable 10 in the short direction.

[0026] The two cores at both ends consist of a multicore fiber (MCF1) with four cores 1-1 to 1-4 arranged in a square grid pattern on the same circumference except for the center, and a multicore fiber (MCF2) with four cores 2-1 to 2-4 arranged in a square grid pattern on the same circumference except for the center.

[0027] The two inner cores are single-mode fibers (SMF1, SMF2) with one core positioned at the center.

[0028] These four optical fibers 11 are positioned and fixed relative to each other. In other words, each optical fiber 11 is positioned and fixed at a desired interval in the radial direction of the optical fiber 11.

[0029] The four optical fibers 11 are arranged and fixed in a single line along the radial direction of each fiber. Because each optical fiber 11 is arranged and fixed in a single line, no unintended twisting occurs in each optical fiber 11 when the multi-core optical fiber cable 10 is installed on the linear structure 100. Therefore, it is not necessary to consider this twisting in the analysis device 40.

[0030] A multi-core optical fiber cable 10 only needs to have at least one MCF. In other words, if it has multiple optical fibers 11, at least one of those multiple optical fibers 11 needs to be an MCF.

[0031] If multiple optical fibers 11 are provided, these multiple optical fibers 11 may be arranged in a single row or in multiple rows. In other words, in the cross-section of the multi-core optical fiber cable 10 in the short-side direction, they only need to be fixedly arranged in a single row at a desired interval in the vertical direction, the horizontal direction, or both directions.

[0032] While at least one MCF is sufficient, having multiple is preferable. If the desired measurement accuracy cannot be obtained with a given MCF, the measurement results of another MCF can be utilized, allowing for efficient measurement of the MCF's shape. Furthermore, the analysis results of multiple MCFs can be used interchangeably, enabling more accurate measurement of the MCF's shape.

[0033] The MCF only needs to have four or more cores in addition to the central core. The central core of the MCF may or may not have a core. The cladding diameter of the MCF is preferably 125 ± 1 μm, because it allows the use of existing multi-core optical fiber cables.

[0034] The multi-core optical fiber cable 10 includes, for example, optical fiber ribbon wire.

[0035] [Functions of the analysis device 40] The analysis device 40 analyzes the longitudinal shape of the MCF from the strain distribution in the longitudinal direction of the MCF, and then analyzes the shape of the linear structure 100 from the analysis results.

[0036] In this embodiment, when the analysis device 40 analyzes the longitudinal shape of the MCF, it determines the torsional angle applied to the core of the MCF due to bending of the MCF, calculates the spin rate from that torsional angle, and reflects that spin rate in the shape analysis.

[0037] In other words, the analysis device 40 has a curvature detection function that determines the bending strain included in the measured strain from the measured strain at each point of the MCF core measured when the multi-core optical fiber cable 10 is installed on the linear structure 100, and calculates the curvature and bending angle at each point of the core from that bending strain.

[0038] Furthermore, the analysis device 40 is equipped with a function to calculate the spin rate at each point of the core from its bending strain. Specifically, the analysis device 40 is equipped with a torsion detection function that calculates the torsional angle at each point of the core from its bending strain, and then calculates the spin rate at each point of the core by differentiating the torsional angle with respect to the arc length (circumference) of the MCF.

[0039] Furthermore, the analysis device 40 has a function to analyze the longitudinal shape of the MCF from the calculated curvature and bending angle at each point of the core and the spin rate at each point of the core. Specifically, the analysis device 40 analyzes the three-dimensional shape and shape changes of the MCF and linear structure 100 from the curvature and bending angle at each point of the core, and corrects the analyzed shape with the spin rate at each point of the core.

[0040] In this way, the shape values ​​of the MCF, which are determined from the curvature and bending angle, are made more accurate by reflecting the torsional angle and spin rate applied to the core of the MCF. This improves the accuracy of shape measurement for both the MCF and linear structures.

[0041] [Method for measuring torsional angle and spin rate] Next, we will explain how to measure the torsional angle and spin rate applied to the core of the MCF due to bending of the MCF.

[0042] Figure 3 is a schematic diagram of the measurement system for the multi-core optical fiber cable 10. The multi-core optical fiber cable 10 and the strain distribution measuring device 30 are connected by a fan-in device 50. A BOTDR was used as the strain distribution measuring device 30. The spatial resolution and reading resolution of the BOTDR are 1.0 m and 0.1 m, respectively.

[0043] First, as shown in Fig. 3(a), the strain distribution was measured in a state where the multi-core optical fiber cable 10 was wound with a winding diameter of about 0.31 m (with bending). Next, as shown in Fig. 3(b), the strain distribution was measured in a state where about 18 m at the end of the multi-core optical fiber cable 10 was linearly extended (without bending).

[0044] Figs. 4A and 4B are diagrams showing the measurement results of the strain distribution of MCF1 in the state with bending. Figs. 5A and 5B are diagrams showing the measurement results of the strain distribution of MCF1 in the state without bending. The horizontal axis is the distance from the strain distribution measuring device 30, and the vertical axis is the strain value.

[0045] Each figure shows the strain values of the four cores 1-1 to 1-4 provided in MCF1. The section corresponding to the end portion is the section from 86 m to 104 m, and it can be seen that the strain values obtained with bending in Fig. 4 and without bending in Fig. 5 are significantly different.

[0046] From the strain distribution obtained by measurement, the bending strain ε i (z) of the measurement position z of the core i (i = 1-1 to 1-4) of MCF1 can be obtained by Equation (1).

[0047]

Equation

[0048] ε circle i (z) is the strain value of the core i in the state with bending. ε straight i (z) is the strain value of the core i in the state without bending. ε axis i (z) is the axial strain caused by the axial force of the core i. ε error i (z) is the measurement error of the strain value of the core i. a, s end 、s start are constants indicating the sample interval, the end position of the data, and the start position of the data, respectively. They are 10, 200, and 799, respectively.

[0049] Figure 6 shows the bending strain ε of core i obtained by equation (1). bend i This figure shows the distribution of (z). In the section up to 86m, the value is close to 0, indicating no difference. In the section from 86m to 104m, which corresponds to the end point, there is a difference depending on whether or not bending is present, and it can be seen that the positive and negative values ​​of the bending strain between specific cores are always opposite.

[0050] As shown in Figure 6, the bending strain distributions of core 1-1 and core 1-4 are symmetrical with respect to the line where the bending strain value is 0. This is because core 1-1 and core 1-4 are in a symmetrical positional relationship with respect to the center point of MCF1 (see Figure 2). The same symmetrical shape is observed between core 1-2 and core 1-3.

[0051] Since the four cores 1-1 to 1-4 are arranged in a square grid on the same circumference in the radial direction of MCF1, when MCF1 is bent in a certain direction, cores in symmetrical positions with respect to the center point will be subjected to tensile and compressive loads, respectively, and the bending strain ε between those cores bend i (z) is the opposite of that relationship in terms of positive and negative signs.

[0052] Furthermore, from Figure 6, the bending strain ε of core i bend i It can be seen that (z) alternates between positive and negative values ​​along its longitudinal direction.

[0053] Based on these findings, it is possible that twisting is occurring in the cores 1-1 to 1-4 of the MCF1 within the multi-core optical fiber cable 10.

[0054] Next, the bending strain ε of core i bend i This section explains how to determine the core's torsional angle and spin rate from (z).

[0055] Figure 7 shows an example of the torsional angle θ of core i. The positions of cores 1-1 to 1-4 are the positions when bent. The torsional angle θ is the angle of the MCF1 applied to core 1-1 at a predetermined position z from the bending direction. 1-1 That is what they say.

[0056] In Figure 7, the bending direction of MCF1 is used as the reference direction for the torsional angle, but the direction to the core's position when not bent may also be used as the reference direction.

[0057] Bending strain ε of core i at a predetermined position z bend i (z) is the torsional angle θ of the MCF1 at a predetermined position z in arc length s of the MCF1. i Since (z) is proportional to the distance r from the center of MCF1 to core i, it can be expressed as equation (2).

[0058]

number

[0059] κ is the curvature of the bending diameter at each point along the longitudinal direction of core i. The method for calculating the curvature κ will be described later.

[0060] Transform equation (2) into equation (3), and add the bending strain ε of the core i at a predetermined position z to equation (3). bend i By substituting the measured value of (z), the distance r, and the curvature κ, the torsional angle θ of the core i at a given position z can be determined. i (z) can be determined.

[0061]

number

[0062] Then, the torsional angle θ of the core i at the predetermined position z is determined. i By differentiating (z) with respect to the arc length s of MCF1, the spin rate p of the core i at a given position z can be determined.

[0063]

number

[0064] Torsional angle θ i The spin rate p represents the torsional information of the core. Torsional angle θi By converting this to a spin rate p, the torsional information can be represented numerically in an easily understandable way.

[0065] Figure 8 shows the torsional angle θ of each core i in the MCF1. i This figure shows the calculated values ​​of (z). It can be seen that in the section from 86m to 104m, which corresponds to the terminal end, each core i is subjected to a twist of approximately two rotations.

[0066] [Method for measuring the shape of optical fibers and linear structures] Figure 9 shows a method for measuring the shape of the optical fiber 11 and the linear structure 100. Here, we will explain the case in which the multi-core optical fiber cable 10 shown in Figure 2 is installed (laid, inserted) into the linear structure 100 and the shape of the MCF1 is measured.

[0067] Step S1; The strain distribution measuring device 30 measures the strain distribution (strain at each point in the longitudinal direction) of each core i of MCF1 under reference conditions. If necessary, the strain distribution measuring device 30 also measures the strain distribution of each core i of MCF2. The reference conditions refer to the state in which the shape of MCF1 is known, such as when the multi-core optical fiber cable 10 is shipped (in a drum-wound state), before installation, or immediately after installation.

[0068] Step S2; The strain distribution measuring device 30 measures the strain distribution of each core i of MCF1 under arbitrary conditions. If the accuracy required for shape analysis cannot be obtained, the strain distribution measuring device 30 measures the strain distribution of each core i of MCF2. An arbitrary condition is a state in which the shape of MCF1 is unknown, such as after a predetermined time has elapsed since the installation of the multi-core optical fiber cable 10.

[0069] Step S3; The analysis device 40 calculates the difference strain ε between the measured strain of each core i of MCF1 in the reference state and the measured strain of each core i of MCF1 in the arbitrary state. i We seek.

[0070] The differential strain ε of each core i in MCF1 i The bending strain ε is caused by bending MCF1.bend i And the axial strain ε caused by the axial force of MCF1 a It is the sum of and . Therefore, the difference strain ε of each core i of MCF1 i This is expressed by equation (5).

[0071]

number

[0072] Axial strain ε a This value is constant within MCF1 and is a common value for each core i.

[0073] Axial strain ε a We find its axial strain ε a The difference strain ε calculated from the measurement results i Substitute and into equation (5) to get the bending strain ε of each core i. bend i We will find the axial strain ε. a The calculation method will be explained later.

[0074] From here on, the bending strain ε of each core i calculated here... bend i Using this method, we determine the curvature κ and bending angle β of each core i, and the spin rate p of each core i.

[0075] Bending strain ε of each core i bend i The relationship between the curvature κ and the bending angle β is expressed by equation (6).

[0076]

number

[0077] r i As shown in Figure 10, α is the distance from the radial cross-sectional center C of MCF1 to the center of each core i. i α is the angle between the line connecting the center of core i and the cross-sectional center C and the line connecting the center of the adjacent core i and the cross-sectional center C. Since each core i is arranged at approximately equal intervals on a concentric circle, the angle α is... iIt is 90 degrees.

[0078] κ and β are the curvature and bending angle (the angle towards the center when MCF1 is bent) applied to MCF1, respectively, and are common values ​​for each core i.

[0079] Since MCF1 has four cores, a system of four linear equations can be obtained for equation (6). The analysis device 40 calculates the difference strain ε of each core i. bend i and the known distance r i and the known angle α i By substituting and into equation (4), and utilizing the fact that the curvature κ and bending angle β do not depend on any of the cores, the curvature κ and bending angle β at each point of each core i in the longitudinal direction are determined using analytical methods such as regression analysis.

[0080] Furthermore, the bending strain ε of each core i bend i and the torsional angle θ i The relationship can be expressed by equation (7). Equation (7) is the same as equation (2).

[0081]

number

[0082] The analysis device 40 measures the differential strain ε of each core i. bend i and the known distance r i Substitute the known curvature κ into equation (7) and find the torsional angle θ at each point of each core i in the longitudinal direction. i The following is determined. At this time, the analysis device 40 may calculate the average value of all cores after the unwrapping process.

[0083] Subsequently, the analysis device 40 determines the torsional angle θ of each core i. i By differentiating with respect to the arc length s of MCF1, we can find the spin rate p at each point in each core i.

[0084] Step S4; The analysis device 40 uses the Frenet-Serret integral formula to analyze the three-dimensional shape of the MCF1 in the longitudinal direction from the curvature κ and bending angle β at each point of each core i and the spin rate p at each point of each core i.

[0085] Specifically, the analysis device 40 measures the differential strain ε in the direction corresponding to the curvature κ and bending angle β at each point at distance z where the strain was measured. i The position vector of MCF1 is derived by determining the position vector of a corresponding magnitude and correcting its direction with the spin rate p at each point.

[0086] In other words, the analysis device 40 takes into account the spin rate p at each point and continuously derives position vectors from the measurement start point to determine in which direction and to what extent each point along the longitudinal direction of the MCF1 is deformed.

[0087] Furthermore, the analysis device 40 analyzes the shape of the linear structure 100 based on the three-dimensional shape of the MCF1. For example, the analysis device 40 outputs the three-dimensional shape and shape changes of the MCF1 directly as the calculated results of the shape and shape changes of the linear structure 100.

[0088] The analysis device 40 repeatedly performs steps S2 to S4 periodically or irregularly. The analysis device 40 calculates the difference strain ε of at least two measured strains measured at different timings. i The difference is calculated, and the shape changes of MCF1 and linear structure 100 are analyzed from that difference.

[0089] [supplement] This section explains the effect of correcting with spin rate p on measurement accuracy. When spin rate p is considered, equation (6) is expressed as equation (8).

[0090]

number

[0091] k1 and k2 are torsional correction factors. ν is Poisson's ratio. p is the spin rate of the core on the circumference. ai angle α i This is the initial angle of ε. t This is torsional distortion.

[0092] Angle α i From the calculation formula, it can be seen that the spin rate p is incorporated into the torsional angle θ. This results in angle α i As this changes, the curvature κ and bending angle β obtained from the four-variable system of equations (8) also change. In other words, the spin rate p contributes to the curvature κ and bending angle β.

[0093] Therefore, by utilizing the spin rate p in addition to the curvature κ and bending angle β, the measurement accuracy of MCF1 can be improved.

[0094] [Axis strain ε a [How to calculate it] If the core is in the center of the MCF, the strain measured at that core is not affected by bending, so equation (5) is ε i =ε a This is the result. If there is no core at the center of the MCF, equation (5) becomes a system of N equations depending on the number of cores N, and the axial strain ε can be calculated using analytical approaches such as regression analysis. a Calculate.

[0095] Furthermore, the analysis device 4 uses the differential strain obtained from the SMF to determine the axial strain ε a And its axial strain ε a ε of the MCF axial strain a This is also acceptable. This will further improve the shape accuracy of the MCF.

[0096] [Verification results of MCF shape measurement] We wrapped MCF1 around a 1m diameter tube and verified how much shape sensing using torsional information affects measurement accuracy.

[0097] Figure 11 shows the verification results of the MCF shape measurement. Figure 11(a) is shown in three dimensions, and Figures 11(b) to 11(c) are shown in two dimensions. The solid line represents the correct shape of the MCF. The dashed and dotted lines represent the shapes when measured with and without torsional information, respectively.

[0098] We confirmed that the accuracy of shape measurement improved by including torsional information in the measurement, that is, by incorporating the spin rate p into the torsional angle θ.

[0099] [effect] According to this embodiment, since the shape of the MCF is analyzed considering the spin rate of the core, the shape of the MCF can be analyzed with high accuracy even when torsion is applied to the MF. This improvement in shape measurement accuracy contributes to improved work efficiency during construction and fault location identification.

[0100] [others] This disclosure is not limited to the embodiments described above. This disclosure can be modified in numerous ways within the scope of its essence.

[0101] The analysis device 40 of this embodiment described above can be realized using a general-purpose computer system that includes, for example, a CPU 901, a memory 902, a storage 903, a communication device 904, an input device 905, and an output device 906, as shown in Figure 12.

[0102] Memory 902 and storage 903 are storage devices. In this computer system, the CPU 901 executes a predetermined program loaded onto memory 902, thereby realizing each function of the analysis device 40.

[0103] The analysis device 40 may be implemented on a single computer. The analysis device 40 may be implemented on multiple computers. The analysis device 40 may also be a virtual machine implemented on a computer.

[0104] The program for the analysis device 40 can be stored on a computer-readable recording medium such as an HDD, SSD, USB memory, CD, or DVD. A computer-readable recording medium is, for example, a non-transitory recording medium. The program for the analysis device 40 can also be distributed via a communication network. [Explanation of symbols]

[0105] 1. Analysis System 10 Multi-core fiber optic cable 20 Optical switches 30 Strain distribution measuring device 40 Analyzer 50 Fan-in-Devices 100 linear structures 901 CPU 902 memory 903 Storage 904 Communication equipment 905 Input device 906 Output device

Claims

1. A multi-core optical fiber cable comprising multiple optical fibers, each containing a multi-core fiber with four or more cores in addition to the central core, wherein the position of each optical fiber is fixed relative to the other optical fibers, A strain distribution measuring device for measuring the strain at each point in the longitudinal direction of the core of the plurality of optical fibers, The system includes an analysis device that analyzes the shape of the plurality of optical fibers from the distortion at each of the aforementioned points, The aforementioned analysis device is An analysis system that determines the bending strain contained in the strain measured at each point of the core of the multicore fiber when the multicore optical fiber cable is installed in a linear structure, calculates the curvature and bending angle at each point of the core from the bending strain, calculates the spin rate at each point of the core from the bending strain, and analyzes the shape of the multicore fiber based on the calculation results.

2. The aforementioned analysis device is The analysis system according to claim 1, wherein the torsional angle at each point of the core is calculated from the bending strain, the spin rate at each point is calculated by differentiating the torsional angle with respect to the circumference of the core, and the shape of the multicore fiber is analyzed by correcting the shape analyzed from the curvature and bending angle at each point with the spin rate at each point.

3. The aforementioned analysis device is The analysis system according to claim 1, which determines the difference in strain at two points measured at different timings and analyzes the shape change of the multicore fiber from the difference.

4. The aforementioned analysis device is The analysis system according to claim 1, which analyzes the shape of the linear structure based on the analysis results of the shape of the multicore fiber.

5. The aforementioned plurality of optical fibers are The analysis system according to claim 1, wherein the optical fibers are positioned in one or more rows at desired intervals in the radial direction.

6. The aforementioned plurality of optical fibers are The analysis system according to claim 1, comprising the multicore fiber and the single-mode fiber.

7. An analytical device that analyzes the shape of a multicore fiber, which has four or more cores in addition to the center, when it is installed in a linear structure. This device calculates the bending strain contained in the strain from the strain measured at each point of the core, calculates the curvature and bending angle at each point of the core from the bending strain, calculates the spin rate at each point of the core from the bending strain, and analyzes the shape of the multicore fiber based on the calculation results.

8. In analytical methods performed using analytical equipment, An analysis method for analyzing the shape of a multicore fiber, which has four or more cores in addition to the center, when it is installed in a linear structure. This method involves determining the bending strain contained in the strain measured at each point of the core, calculating the curvature and bending angle at each point of the core from the bending strain, calculating the spin rate at each point of the core from the bending strain, and analyzing the shape of the multicore fiber based on the calculation results.

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