Freezing prevention design apparatus, method, and program

Abstract

A freezing countermeasure design device 20 designs piping 11 that accommodates therein an optical fiber cable 12 and a hollow pipe 13, and that makes provisions against the freezing of water 101 filling the piping 11, by using a void ensured by the hollow pipe 13. The freezing countermeasure design device 20 includes: an input unit 21 for inputting parameters defining the optical fiber cable 12, the hollow pipe 13, and the piping 11, and a pressure that the optical fiber cable 12 can withstand; and a void ratio calculation unit that calculates a void ratio on the basis of the diameter of the hollow pipe 13, configured so that the pressure in the piping 11 when the water filling the piping 11 freezes does not exceed the pressure that the optical fiber cable 12 can withstand, the pressure in the piping being based on the parameters, the volume of ice obtained by the water filling the piping 11 freezing, a volume corresponding to the pressure of the water filling the piping 11, and the Young's modulus of ice.

Description

[Technical Field]

[0001] This disclosure relates to a design apparatus, method, and program for preventing freezing of conduits containing optical fiber cables, and more specifically, to a design apparatus, method, and program for preventing freezing of conduits that also contain hollow pipes to create air gaps within the conduits in preparation for the freezing of water accumulated inside the conduits. [Background technology]

[0002] Currently, optical fibers are widely used as the primary communication infrastructure. These optical fibers are used as optical fiber cables (sometimes simply called optical cables or cables), which are made by bundling multiple fibers together and covering the outer perimeter with an outer sheath. Especially outdoors, where they are laid underground or overhead, it is essential that the optical fiber cables can maintain their characteristics in the face of changes in the surrounding environment.

[0003] When fiber optic cables are laid in underground conduits (for example, cylindrical conduits), rainwater and other liquids can flow into and accumulate inside the conduits. In cold weather, if this accumulated water freezes, the volume expansion caused by the solidification of water into ice can put pressure on the fiber optic cable, leading to optical loss.

[0004] To address these problems, technologies have been proposed to increase the strength of optical fiber cables (for example, Patent Document 1). However, this technology requires the preparation of a special optical fiber cable with an outer sheath coated with a resin that hardens near the freezing temperature of water for sections where freezing occurs, which is not economical.

[0005] Furthermore, a technique has been proposed to create a gap within the conduit to absorb freezing pressure (for example, Patent Document 2). In this technique, a dedicated optical fiber cable is not required, and a hollow pipe is disclosed as a means of securing the gap. [Prior art documents] [Patent Documents]

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Here, the required void varies depending on the strength of the optical fiber cable. This is also clear from the fact that in the technology of Patent Document 1, the void is made unnecessary by coating the optical fiber cable with an outer skin that becomes hardened near the temperature at which water freezes. Also, since pressure is generated by the volume expansion of water due to freezing, the required void also varies depending on the amount of water filling the pipeline.

[0008] However, in the prior art, the relationship between the strength of the optical fiber cable and the void was not clear, and it was not possible to pre-design how much void should be provided in order to maintain the characteristics of the optical fiber cable when the water in the pipeline froze. For this reason, it was necessary to take measures such as securing an excessive void for safety or securing an additional void when a failure occurred.

[0009] The present disclosure is proposed in view of the above situation, and an object thereof is to provide a freezing countermeasure design device, method, and program capable of appropriately implementing a freezing countermeasure for accumulated water in a pipeline that houses a hollow pipe for securing a void together with an optical fiber cable.

Means for Solving the Problems

[0010] To solve the above-mentioned problems, the freeze-proof design device according to this application is a conduit freeze-proof design device that accommodates a hollow pipe together with an optical fiber cable in the conduit and prepares for the freezing of water in the conduit by the void secured by the hollow pipe, and includes an input unit for inputting parameters that define the optical fiber cable, hollow pipe and conduit, and the pressure that the optical fiber cable can withstand, and a void ratio calculation unit that calculates the void ratio based on the parameters, the volume of ice formed when the water filling the conduit freezes, the volume corresponding to the pressure of the water filling the conduit, and the Young's modulus of the ice, so that the pressure inside the conduit when the water filling the conduit freezes does not exceed the pressure that the optical fiber cable can withstand.

[0011] The freeze protection design method relating to this application is a pipeline freeze protection design method that accommodates a hollow pipe together with an optical fiber cable inside the pipeline, and prepares for the freezing of water filling the pipeline through the air gap secured by the hollow pipe, comprising an input step of inputting parameters defining the optical fiber cable, hollow pipe, and pipeline, and the pressure that the optical fiber cable can withstand, The method includes a calculation step of calculating the void ratio based on the aforementioned parameters, the volume of ice formed when the water filling the conduit freezes, the volume corresponding to the pressure of the water filling the conduit, and the diameter of the hollow pipe such that the pressure inside the conduit when the water freezes, based on the Young's modulus of the ice, does not exceed the pressure that the optical fiber cable can withstand.

[0012] The program relating to this application causes a computer to function as the freeze-prevention design device. [Effects of the Invention]

[0013] According to this disclosure, for conduits that house both optical fiber cables and hollow pipes to ensure air gaps, appropriate measures can be taken to prevent the freezing of water accumulated inside the conduit. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view of a water-filled pipeline. [Figure 2]This is a block diagram of a device designed to prevent freezing. [Figure 3] This is a flowchart of the series of steps involved in designing a freeze prevention measure. [Figure 4] This is a cross-sectional view of the pipeline shown in Figure 1 when the water freezes. [Figure 5] This is a perspective view illustrating the measurement of optical loss due to compression of an optical fiber cable. [Figure 6] This is a cross-sectional view illustrating the measurement of optical loss due to compression of an optical fiber cable. [Figure 7] This is a cross-sectional view illustrating the conversion of the cross-sectional area of ​​an optical fiber cable to pressure. [Figure 8] This graph shows the measured loss of the optical fiber cable in the example. [Figure 9] This graph shows the relationship between the pressure inside the pipeline and the required porosity. [Figure 10] This is a graph showing the results of the freezing test. [Figure 11] This is an example of a hardware configuration. [Modes for carrying out the invention]

[0015] The embodiments of the freeze prevention design apparatus, method, and program will be described in detail below with reference to the drawings. Figure 1 is a cross-sectional view of a conduit 11 containing the optical fiber cable 12 and hollow pipe 13 that are the subject of this embodiment. The conduit 11 is filled with water 101 that has entered.

[0016] The pipe 11 has an inner diameter D0 and a wall thickness t. p It has a cylindrical shape that is symmetrical with respect to the axis extending in the longitudinal direction. The optical fiber cable 12 has an outer diameter d0 and a wall thickness t. cIt has an outer surface that is symmetric about the axial direction. The hollow pipe 13 has a diameter dh0 and is composed of a wall surface that is symmetric about the axial direction. The hollow pipe 13 is made of a flexible plastic such as polyethylene to provide a void in the pipeline 11 in case the water 101 filling the pipeline 11 freezes. Note that the subscript 0 in the inner diameter D0 of the pipeline 11, the outer diameter d0 of the optical fiber cable 12, and the diameter dh0 of the hollow pipe 13 indicates that it corresponds to the state where the water 101 filling the pipeline 11 is not frozen.

[0017] Figure 2 is a block diagram showing a schematic configuration of the freezing countermeasure design device 20 of the present embodiment. The freezing countermeasure design device 20 calculates the porosity that needs to be ensured by the hollow pipe 13 so that no optical loss occurs in the optical fiber cable 12 even if the pressure increases in the pipeline 11 due to the volume expansion caused by the freezing of the water 101 filling the pipeline 11 shown in FIG. 1.

[0018] The freezing countermeasure design device 20 has an input unit 21 that receives inputs of parameters defining the optical fiber cable 12, the hollow pipe 13, and the pipeline 11, as well as the pressure P c that the optical fiber cable 12 can withstand. Note that hereinafter, the pressure that the optical fiber cable 12 can withstand may also be referred to as pressure resistance. Specifically, the input unit 21 receives, from an external user terminal 31, the outer diameter d0, the wall thickness t c and the Young's modulus E of the material c as parameters of the optical fiber cable 12, the Young's modulus E h as a parameter of the hollow pipe 13, the inner diameter D0, the wall thickness t p and the Young's modulus E of the material p as parameters of the pipeline 11, and the pressure P c that the optical fiber cable 12 can withstand. Since the diameter dh0 of the hollow pipe 13 is determined by calculation as described later, no input is required. The input unit 21 may constitute an input interface that receives data input from an external user terminal 31.

[0019] Furthermore, the freeze protection design device 20 defines the parameters that define the optical fiber cable 12, hollow pipe 13, and conduit 11 input to the input unit 21, as well as the pressure P that the optical fiber cable 12 can withstand, which will be described later. c The system includes a void ratio calculation unit 22 that calculates the required void ratio to be secured in the hollow pipe 13 based on the calculation, and an output unit 23 that outputs the void ratio calculated by the void ratio calculation unit 22. Details of the void ratio calculation in the void ratio calculation unit 22 will be described later. The output unit 23 may be configured as an output interface for outputting data to an external display device 32. The display device 32 may also be used as a user terminal 31 for inputting data.

[0020] The freeze protection design device 20 of this embodiment is configured as a module consisting of an input unit 21, a void ratio calculation unit 22, and an output unit 23, and data input and output may be routed via an external user terminal 31 and display device 32. Alternatively, the freeze protection design device 20 may be configured as an integrated device including the user terminal 31 and display device 32. The freeze protection design device 20 may also be provided as a program that realizes freeze protection design processing by being executed, for example, on a personal computer.

[0021] Figure 3 is a flowchart showing a series of operations in the freeze protection design method performed in the freeze protection design device 20. The operation of the freeze protection design device 20 will be explained according to this flowchart. In the first step S1, the input unit 21 receives input from an external user terminal 31 of parameters defining the optical fiber cable 12, hollow pipe 13, and conduit 11, as well as the pressure that the optical fiber cable 12 can withstand. Specifically, the input unit 21 receives the parameters of the optical fiber cable 12 as outer diameter d0 and wall thickness t. c and the Young's modulus E of the material c Young's modulus E is a parameter of the hollow pipe 13. h The parameters of the pipe 11 are inner diameter D0 and wall thickness t. p and the Young's modulus E of the material p Furthermore, the pressure P that the optical fiber cable 12 can withstand cReceive. As mentioned above, the diameter dh0 of the hollow pipe 13 is determined by calculation, so no input is required.

[0022] In step S2, once the void ratio calculation unit 22 is input to the input unit 21, the parameters defining the optical fiber cable 12, hollow pipe 13, and conduit 11, as well as the input P of the pressure that the optical fiber cable 12 can withstand, are entered. c Based on this, the required void ratio to be secured by the hollow pipe 13 is calculated using equation (8), which defines the pressure P inside the pipeline 11 described later.

[0023] [Derivation of equation (8) which defines the pressure P in the pipeline 11] Below, we derive equation (8), which defines the pressure P inside the pipe 11. In Figure 1, the volume V0 of the water 101 filling the pipe 11 is given by the following equation (1). In this specification, volume refers to the volume per unit length in the longitudinal direction of the pipe 11.

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[0024] Figure 4 is a cross-sectional view showing the state in which the water filling the conduit 11 in Figure 1 has frozen. The water 101 filling the conduit 11 has frozen into ice 102 and has expanded in volume. In response to this volume expansion, pressure P is generated inside the conduit 11, and this pressure P is exerted on the inner surface of the conduit 11 and the outer surfaces of the optical fiber cable 12 and the hollow pipe 13. In response to this pressure P, the inner diameter of the conduit 11 expands to D1, and the outer diameter of the optical fiber cable 12 and the diameter of the hollow pipe 13 shrink to d1 and dh1, respectively. The subscript 1 in the inner diameter D1 of the conduit 11, the outer diameter d1 of the optical fiber cable 12, and the diameter dh1 of the hollow pipe 13 indicates that the water 101 filling the conduit 11 is frozen and the conduit 11 is filled with ice 102.

[0025] In Figure 4, the volume V1 of the ice 102 filling the pipe 11 is given by the following equation (2).

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[0026] The pressure P inside pipe 11 can be considered to have arisen because the original volume V2 of the ice 102, which is formed from the frozen water 101 given by equation (3), is packed into the volume V1 inside pipe 11 given by equation (2). From this, the pressure P inside pipe 11 is given by equation (4). Note that α in equation (3) is the expansion coefficient of ice, and κ in equation (4) is the Young's modulus of ice.

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[0027] In Figure 4, the expansion ΔD0 of the inner diameter of the conduit 11 due to the pressure P inside the conduit 11 and the reduction Δd0 of the outer diameter of the optical fiber cable 12 are given by equations (5) and (6), respectively, based on the mechanics of materials. Note that in equation (5), E p and t p These are the Young's modulus and wall thickness of pipe 11, respectively. Also, E in equation (6) c and t c These are the Young's modulus and wall thickness of the optical fiber cable 12, respectively.

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[0028] As for the hollow pipe 13, since its interior is hollow and made of a flexible plastic material such as polyethylene, the reduction in diameter Δdh0 of the hollow pipe 13 due to pressure P is calculated using equation (7), which assumes that it is flattened in a uniaxial direction in response to pressure P. Note that in equation (7), E h This is the Young's modulus of the hollow pipe 13.

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[0029] By combining equations (1), (2), (5) to (7) with equation (4), we obtain equation (8), which defines the pressure P inside the pipe 11.

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[0030] Here, in addition to the parameters included in equation (8), the parameters related to Figures 1 and 4 are summarized in Table 1.

[0031] [Table 1]

[0032] Equation (8), which defines the pressure P inside the conduit 11, can be considered a function where the diameter dh0 of the hollow pipe 13 is the independent variable and the pressure P is the dependent variable. The pressure P is the pressure that the optical fiber cable 12 can withstand. c By doing so, the optical fiber cable 12 can withstand the pressure P. c The diameter dh of the hollow pipe 13 is necessary to prevent optical loss in the corresponding optical fiber cable 12. c You can obtain this.

[0033] As shown in equation (9), the pressure P that the optical fiber cable 12 can withstand c The diameter dh of the hollow pipe 13 corresponding to c Based on this, the required void ratio v to prevent optical loss in the optical fiber cable 12 is c (%) is obtained. The denominator of equation (9) is the volume of water 101 filling the pipe 11, and the numerator is the volume of the required void secured in the hollow pipe 13.

[0034] In step S3, the output unit 23 outputs the required void ratio v calculated by the void ratio calculation unit 22. c Outputs the required void ratio v. Output unit 23 outputs the required void ratio v. c The output is sent to an external display device 32. In this step S3, the series of operations of the freeze protection design method are completed.

[0035] [The pressure P that the fiber optic cable 12 can withstand] c ] The input section 21 of the freeze protection design device 20 is configured to withstand a pressure P that the optical fiber cable 12 can withstand. c You need to input this pressure P c This can be obtained by measuring the optical fiber cable 12.

[0036] Figures 5 and 6 illustrate the measurement of optical loss due to compression of an optical fiber cable 12. Figure 5 is a perspective view of the optical fiber cable 12, and Figure 6 is a cross-sectional view of the optical fiber cable 12. As shown in Figure 5, the optical fiber cable 12 to be measured has an optical fiber core 106 drawn from one end connected to a light source, and an optical fiber core 106 drawn from the other end connected to a power meter. Such an optical fiber cable 12 is sandwiched between the top surface of the support base 108 and the bottom surface of the movable member 109, and a load W is applied to the optical fiber cable 12 by the movable member 109.

[0037] As shown in Figure 6, the optical fiber cable 12 has a cable sheath 12b as its outermost layer. The cable sheath 12b has a thickness t of the optical fiber cable 12. c This corresponds to the following. For convenience, the inside of the optical fiber cable 12 surrounded by the cable sheath 12b will be referred to as the cable body 12a. There is a certain gap between the optical fiber cores 106 that make up the cable body 12a, and the cross-sectional area S of the cable body 12a is the critical cross-sectional area S c When the pressure decreases to a certain point, the cable sheath 12b makes strong contact with the optical fiber core 106, and force begins to be applied to the fiber. Therefore, the critical cross-sectional area Sc of the cable body 12a where optical loss occurs when pressure is applied to the optical fiber cable 12 is considered to be independent of the cross-sectional shape of the optical fiber cable 12. Since it is not convenient to apply isotropic pressure such as actual freezing pressure when evaluating the pressure that the optical fiber cable 12 can withstand, we will measure the optical loss due to uniaxial compression and determine the critical cross-sectional area Sc where optical loss occurs.

[0038] In response to a load W applied in one axis direction, the optical fiber cable 12 is compressed and deformed into a flattened shape, reducing its height and decreasing the cross-sectional area S of the cable body 12a. This reduction in height is called the amount of flattening x. The cross-sectional area S of the cable body 12a is the critical cross-sectional area S. c The flattening amount x decreases to the point where light loss occurs, and the critical flattening amount x is defined as the flattening amount x. c Let's go with that.

[0039] Critical cross section S c The value of is obtained by actually measuring the optical fiber cable 12 to be measured. To do this, the optical fiber cable 12 to be measured is cut to expose the cross-section of the cable body 12a, and the cross-section of the optical fiber cable 12 is measured again for critical flattening x c Observe the cross-sectional area S of the cable body 12a when only that part is crushed, and determine the critical cross-sectional area S c To decide.

[0040] Figure 7 is a cross-sectional view illustrating the conversion of the cross-sectional area S of the optical fiber cable 12 to a pressure P. The left side of Figure 7 shows the optical fiber cable 12 with no pressure P applied. The outermost cable sheath 12b has a thickness t c The cable body 12a has a radius r. The cross-sectional area S0 of the cable body 12a when no pressure P is applied is given by equation (10).

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[0041] The right-hand diagram of Figure 8 shows an optical fiber cable 12 to which pressure P is applied from all sides. Compared to the optical fiber cable 12 shown on the left without pressure P applied, the radius r of the cable body 12a is reduced to r-Δr due to the applied pressure P, and the cross-sectional area S of the cable body 12a is given by equation (11).

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[0042] If the outer diameter of the cable body 12a is denoted as d2, then the outer diameter d2 has the relationship with the radius r given by equations (12) and (13). Also, the outer diameter d2 of the cable body 12a has the relationship with the outer diameter d0 of the optical fiber cable 12 given by equation (14). Here, t c This is the thickness of the cable sheath 12b, i.e., the thickness t of the optical fiber cable 12. c That is the case.

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[0043] On the other hand, the decrease Δd2 in the outer diameter d2 of the cable body 12a due to the application of pressure P to the optical fiber cable 12 is given by equation (15) based on material mechanics. Here, d0 is the outer diameter of the optical fiber cable 12 as described above, and E c This is the Young's modulus of the optical fiber cable 12.

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[0044] Based on equations (11) to (15), the pressure P can be expressed in terms of the cross-sectional area S of the cable body 12a as shown in equation (16). Furthermore, if the outer diameter D0 of the optical fiber cable 12 is used instead of the radius r of the cable body 12a, the pressure P can be expressed as shown in equation (17). Since the parameters other than pressure P and area S are known in equation (18), the pressure P is given as a function of area S.

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[0045] By substituting the measured critical cross-sectional area Sc into equation (17), the critical pressure P at which optical loss occurs can be obtained. c This is obtained. This critical pressure P c However, this pressure is one that the fiber optic cable 12 can withstand.

[0046] According to this embodiment, the required void ratio v to be secured by the hollow pipe 13 to prepare for the freezing of the water 101 filling the pipeline 11 is c (%) The pressure that fiber optic cable 12 can withstand P c This allows for appropriate design according to the circumstances. Consequently, there is no need to secure excessive air gaps for safety reasons, nor is there a need to secure additional air gaps in the event of a failure. Furthermore, by laying optical fiber cables 12 through the conduit 11 designed in this way, stable communication can be ensured without optical loss, regardless of the freezing of water 101 that enters the conduit 11. [Examples]

[0047] In the example, a freezing test was conducted by ensuring an air gap in the conduit 11 filled with water 101. Figure 8 is a graph showing the results of measuring the optical loss of the optical fiber cable 12 in the example. In this measurement, a threshold of 0.15 dB / core was used to determine that optical loss had occurred. The optical fiber cable 12 showed almost no optical loss until the flattening amount x exceeded 3 mm, but increased rapidly when the flattening amount x exceeded 3.5 mm, reaching the optical loss threshold of 0.15 dB / core before the flattening amount x reached 4.0 mm. The flattening amount x at which the optical loss reached the threshold of 0.15 dB is the critical flattening amount x c It was determined that...

[0048] The critical cross-sectional area S was determined by actual measurement. c 16.7mm 2 The following was obtained. Furthermore, the critical cross-section S was obtained using equation (17). c The pressure P that the fiber optic cable 12 can withstand c A pressure of 31.4 MPa was obtained. Here, the thickness of the cable sheath 12b, i.e., the thickness t of the optical fiber cable 12, is used. c The diameter was set to 2.4 mm.

[0049] Figure 9 shows the pressure P and required void ratio v inside the pipe 11. c This graph shows the relationship with the void ratio v required for equation (8) which defines the pressure P inside the pipe 11. c This is obtained by combining equation (9) which defines the following. In Figure 9, the pressure P is equal to the required porosity v c The required porosity v decreases monotonically in response to a pressure P of 31.4 MPa. c The percentage was 25%.

[0050] The required porosity v is as described above. c The derivation can be summarized in Table 2. [Table 2]

[0051] Figure 10 is a graph showing the results of the freezing test. A conduit 11 with an inner diameter D0 of 75 mm was filled with water 101, and the ambient temperature was controlled as shown by the broken line c. The temperature was lowered from room temperature to -20°C and maintained thereafter, then raised to 60°C and maintained thereafter, before being lowered back to room temperature. The optical loss (dB / core) of the optical fiber cable 12 housed in the conduit 11 was measured during this process.

[0052] When a porosity of 20.2% was maintained, as shown by line a, a maximum optical loss of approximately 0.4 dB / core occurred after about 20 hours of maintaining the temperature at -20°C, and this continued until the temperature reached approximately 40°C during the temperature rise process. When a porosity of 22.8% was maintained, as shown by line b, no optical loss was observed throughout the entire freezing test.

[0053] The results of this experiment revealed that at a porosity of 20.2%, light loss occurs due to the freezing of water 101, but at a porosity of 22.8%, no light loss occurs even if water 101 freezes. From this, it is assumed that by ensuring a porosity of at least 22.8%, it is possible to prevent light loss due to the freezing of water 101 filling the pipe 11. This result relates to equation (8) which defines the pressure P inside the pipe 11 and the required porosity v c This is consistent with the required void ratio of 25% shown in Table 2, which was obtained using equation (9) that defines the formula.

[0054] According to the embodiment described above, it becomes possible to pre-calculate the void ratio necessary to prepare for the freezing of water filling the conduit, making it possible to appropriately design the void according to the pressure that the optical fiber cable can withstand.

[0055] This disclosure is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and combined effects can be obtained. Moreover, the embodiments include various disclosures, and various disclosures can be extracted by selecting combinations from the multiple disclosed constituent elements. For example, if the problem can be solved and effects obtained even if some constituent elements are removed from all the constituent elements shown in the embodiment, then the configuration with these removed constituent elements can be extracted as a disclosure.

[0056] The freeze protection design device 20 described above can use, for example, a general-purpose computer system as shown in Figure 11. The illustrated computer system comprises a CPU (Central Processing Unit, processor) 901, memory 902, storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), communication device 904, input device 905, and output device 906. The memory 902 and storage 903 are storage devices. In this computer system, the functions of the freeze protection design device 20 are realized when the CPU 901 executes a predetermined program loaded onto the memory 902.

[0057] The freeze protection design device 20 may be implemented on one computer or on multiple computers. Alternatively, the freeze protection design device 20 may be a virtual machine implemented on a computer. The program of the freeze protection design device 20 can be stored on a computer-readable recording medium such as an HDD, SSD, USB (Universal Serial Bus) memory, CD (Compact Disc), or DVD (Digital Versatile Disc), or distributed over a network. A computer-readable recording medium is, for example, a non-transitory recording medium. [Explanation of Symbols]

[0058] 11 Conduit 12 Fiber optic cables 12a cable body 12b Cable sheath 13 Hollow pipe 20. Anti-freezing design device 21 Input section 22 Porosity calculation section 23 Output section

Claims

1. A conduit freezing prevention design device that houses a hollow pipe together with an optical fiber cable inside the conduit, and uses the air gap created by the hollow pipe to prevent the water inside the conduit from freezing, An input section for inputting parameters that define the optical fiber cable, hollow pipe and conduit, and the pressure that the optical fiber cable can withstand, Includes a void ratio calculation unit that calculates the void ratio based on the aforementioned parameters, the volume of ice formed when the water filling the conduit freezes, the volume corresponding to the pressure of the water filling the conduit, and the diameter of the hollow pipe such that the pressure inside the conduit when the water filling the conduit freezes does not exceed the pressure that the optical fiber cable can withstand, based on the Young's modulus of the ice. The pressure that the optical fiber cable can withstand is calculated based on the cross-sectional area where optical loss occurs when the optical fiber cable is compressed in a uniaxial direction. Freezing prevention design device.

2. The freeze protection design apparatus according to claim 1, wherein the parameters defining the optical fiber cable include outer diameter, wall thickness, and Young's modulus of the material, the parameters defining the hollow pipe include Young's modulus, and the parameters defining the conduit include inner diameter, wall thickness, and Young's modulus of the material.

3. The freeze-prevention design device according to claim 1 or 2, wherein the first volume V1 of ice formed when the water filling the pipeline is frozen, and the second volume V2 when the water filling the pipeline has a pressure P, are given by Young's modulus of ice, and the pressure P in the pipeline when the water filling the pipeline is frozen is given by the relation P = κ(V2 - V1) / V2.

4. The freeze-prevention design apparatus according to claim 3, wherein the volume V0 of water filling the conduit is given by (1 + α)V0, where α is the expansion coefficient of ice, based on the outer diameter of the optical fiber cable, the diameter of the hollow pipe, and the inner diameter of the conduit, and the first volume V1 is given by (1 + α)V0, and the second volume V2 is given by adding to the volume V0 an increase in the volume of water based on the decrease in the outer diameter of the optical fiber cable and the diameter of the hollow pipe and the increase in the inner diameter of the conduit when pressure P is applied to the water in the conduit.

5. The optical fiber cable and the conduit have an axially symmetric cylindrical shape, and when pressure P is applied to the water filling the conduit, their outer and inner diameters shrink and expand, respectively, and the hollow pipe also has an axially symmetric cylindrical shape, but deforms to become flattened in one axis direction when pressure P is applied to the water filling the conduit, as described in claim 4, for the freeze prevention design apparatus.

6. A method for designing a pipeline to prevent freezing of water, which involves housing a hollow pipe together with an optical fiber cable inside the pipeline and using the air gap created by the hollow pipe to protect against the freezing of water filling the pipeline, An input step in which parameters defining the optical fiber cable, hollow pipe and conduit, and the pressure that the optical fiber cable can withstand are input, The calculation step includes calculating the void ratio based on the aforementioned parameters, the volume of ice formed when the water filling the conduit freezes, the volume corresponding to the pressure of the water filling the conduit, and the diameter of the hollow pipe such that the pressure inside the conduit when the water filling the conduit freezes does not exceed the pressure that the optical fiber cable can withstand, based on the Young's modulus of the ice. The calculation step involves determining the pressure that the optical fiber cable can withstand based on the cross-sectional area where optical loss occurs when the optical fiber cable is compressed in a uniaxial direction. Methods for designing measures against freezing.

7. A program that causes a computer to function as a freeze-prevention design device according to claim 1.

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