JP7723635B2 - Tube end member for optical fiber-carrying resin tube, optical fiber-carrying resin tube with tube end member, and method for manufacturing optical fiber-carrying resin tube with tube end member - Google Patents

Description

The present invention relates to a tube end member for an optical fiber-supported resin tube, an optical fiber-supported resin tube with a tube end member, and a method for manufacturing an optical fiber-supported resin tube with a tube end member.

An optical fiber-supported resin tube, in which the optical fiber is embedded in the resin tube in a straight or spiral shape so that it extends axially, can constantly monitor the strain changes, pressure changes, and temperature changes caused by bending, stretching, and twisting in the resin tube from the frequency or phase changes of the Rayleigh scattering of the optical fiber.
In order to detect distortions in the optical fiber-supported resin pipe with higher accuracy, the optical fiber-supported resin pipe has two or more optical fibers. However, simply increasing the number of optical fibers requires separate operations for each optical fiber, making the management of measurement data more complicated. Furthermore, since the number of measurement channels in the device is limited, the effort of connecting the optical fibers each time a measurement is made increases.
For example, as shown in Fig. 11(a), an optical fiber-supported resin tube 910 has four optical fibers inside a cylindrical wall 11A of a resin tube 11. In the optical fiber-supported resin tube 910, it is necessary to connect each of the four optical fibers 12 to an analytical instrument or the like. For this reason, as in the optical fiber-supported resin tube 910A of Fig. 11(b), the ends of adjacent optical fibers in the circumferential direction of the resin tube 11 are fused together to form a folded portion, thereby reducing the number of optical fibers to be managed.
For example, Patent Document 1 describes an invention in which one optical fiber is folded back and connected to a resin pipe, so that four or six optical fibers are arranged along the outer circumferential surface of the resin pipe.
Furthermore, Patent Document 2 describes a construction method in which a casing pipe is buried underground, and an optical fiber-carrying resin pipe is inserted into the casing pipe with the folded-back portion of the optical fiber facing downward.

Japanese Patent Application Laid-Open No. 2004-61112 Japanese Patent Application Laid-Open No. 2006-242743

However, in the inventions of Patent Documents 1 and 2, the optical fiber is fused to the resin tube, and the stress relaxation of the resin tube due to the thermal history at that time can cause deformation of the optical fiber, resulting in loss of optical transmission (microbending).In addition, when inserting the optical fiber-carrying resin tube into the casing, if the folded-back portion of the optical fiber is long, the operation becomes complicated.
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a tube end member for an optical fiber-carrying resin tube that can prevent damage to the folded-back portion and reduce transmission loss.

The present invention has the following aspects.
<1>
A tube end member for an optical fiber-carrying resin tube, which is used for an optical fiber-carrying resin tube having a cylindrical resin tube and two or more optical fibers located within a cylindrical wall of the resin tube and extending in an axial direction of the resin tube, and which has a folded portion on the outer side of the axial direction of the resin tube, in which an arbitrary optical fiber and another arbitrary optical fiber adjacent to the arbitrary optical fiber in the circumferential direction of the resin tube are connected to each other,
It has an inner cylinder and an outer cylinder,
The inner cylinder can be inserted into the outer cylinder in part or in whole,
A tube end member for an optical fiber-supported resin tube, which, when part or all of the inner tube is inserted into the outer tube, forms a storage section between the outer surface of the inner tube and the inner surface of the outer tube to receive the optical fiber in the folded-back portion.
<2>
the outer peripheral surface of the inner cylindrical body has one or more first ridges extending in the axial direction of the inner cylindrical body;
The tube end member for an optical fiber-carrying resin tube according to <1>, wherein the first ridge defines the storage section when the outer tube is placed over the inner tube.
<3>
the inner peripheral surface of the outer cylindrical body has one or more second ridges extending in the tube axis direction of the outer cylindrical body,
The tube end member for an optical fiber-supported resin tube described in <1> or <2>, wherein the second ridge defines the storage section when the outer tube is placed over the inner tube.
＜4＞
the outer cylinder body has an outer cylinder wall and an inner cylinder wall spaced apart from the outer cylinder wall and closer to the tube axis than the outer cylinder wall,
The tube end member for an optical fiber-carrying resin tube according to any one of <1> to <3>, wherein the tube wall of the inner tube is received between the outer tube wall and the inner tube wall.

<5>
<1> to <4>, and a tube end member for an optical fiber-supported resin tube according to any one of <1> to <4>,
a tube end member for the optical fiber-supporting resin tube is provided at an end of the resin tube;
The optical fiber-carrying resin tube with a tube end member is configured such that the folded portion is located within the housing portion.
<6>
The optical fiber-carrying resin tube with tube end member according to <5>, wherein the tube end member for the optical fiber-carrying resin tube is fixed to the resin tube with a screw.

＜７＞
<5> A method for manufacturing an optical fiber-supported resin tube with a tube end member according to the present invention,
The inner cylindrical body is positioned at the end of the resin pipe,
the folded portion is aligned with the outer peripheral surface of the inner cylindrical body,
A method for manufacturing an optical fiber-supported resin tube with a tube end member, in which the outer tube body is placed over the inner tube body to cover part or all of the outer peripheral surface of the inner tube body, and the folded portion is positioned in the accommodating portion between the outer peripheral surface of the inner tube body and the inner peripheral surface of the outer tube body.
＜8＞
The method for manufacturing a resin tube carrying an optical fiber with a tube end member according to <7>, wherein the outer tube body is fixed to the resin tube with a screw.

The tube end member for an optical fiber-supported resin tube of the present invention prevents damage to the folded portion and reduces transmission loss.

1 is an exploded perspective view of an optical fiber-supported resin tube with a tube end member according to a first embodiment of the present invention; 1 is a longitudinal cross-sectional view of an optical fiber-supported resin tube with a tube end member according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2. FIG. 2 is a side view of an inner cylinder body according to the first embodiment of the present invention. FIG. 2 is a longitudinal sectional view of an outer cylinder according to the first embodiment of the present invention. 1 is a process diagram of a resin tube carrying an optical fiber with a tube end member according to a first embodiment of the present invention. 1 is a process diagram of a resin tube carrying an optical fiber with a tube end member according to a first embodiment of the present invention. FIG. 10 is a longitudinal cross-sectional view of an optical fiber-supported resin tube with a tube end member according to another embodiment. 9 is a cross-sectional view taken along line IX-IX of FIG. 8. FIG. 10 is a longitudinal cross-sectional view of an outer cylinder according to another embodiment. FIG. 1 is a perspective view of a conventional optical fiber-supporting resin tube.

The optical fiber-carrying resin tube with a tube end member of the present invention comprises an optical fiber-carrying resin tube and a tube end member for the optical fiber-carrying resin tube (hereinafter, sometimes simply referred to as "tube end member").
The present invention will be described below with reference to embodiments.

[First embodiment]
An optical fiber-carrying resin tube with a tube end member according to a first embodiment of the present invention will be described.
1 and 2 includes an optical fiber carrying resin tube 10 and a tube end member 20. The tube end member 20 is located at the end of the optical fiber carrying resin tube 10.

(Optical fiber-supporting resin tube)
The optical fiber-carrying resin tube 10 in Figures 1 and 2 is a long, cylindrical resin tube. The optical fiber-carrying resin tube 10 includes a cylindrical resin tube 11 and an optical fiber 12 extending in the axial direction (tube axis) O1 of the resin tube 11 within a cylindrical wall 11A of the resin tube 11. In this embodiment, the optical fiber 12 forms two folded portions 12A on the outside of one end of the resin tube 11. The folded portions 12A are ring-shaped. That is, in the optical fiber-carrying resin tube 10, a portion of the optical fiber 12 is embedded in the cylindrical wall 11A, and a portion of the optical fiber 12 protrudes from the cylindrical wall 11A, forming the ring-shaped folded portions 12A.

The number of optical fibers 12 within the cylindrical wall 11A is two or more, and four or more is preferable. In addition, it is preferable that the number of optical fibers 12 within the cylindrical wall 11A is an even number. If there are two or more optical fibers 12, bending displacement can be detected more effectively. If there are four or more optical fibers 12, twisting and flattening displacement can be detected more effectively. It is preferable that there are 20 or fewer optical fibers 12 within the cylindrical wall 11A. If the number of optical fibers 12 is equal to or less than the above upper limit, the mechanical strength of the resin tube 11 can be further increased.

The optical fiber 12 is preferably located within 25% of the thickness of the cylindrical wall 11A from the position that divides it in half at the center toward the surface. This ensures that when the surface of the resin tube 11 is scraped during installation of the optical fiber-supported resin tube 10, the optical fiber 12 is not exposed to the outside of the resin tube 11, making it less likely to be damaged.

In this embodiment, four optical fibers 12 are positioned within the cylindrical wall 11A along the tube axis O1. The four optical fibers 12 within the cylindrical wall 11A are arranged in rotationally symmetric positions relative to one another in a cross section perpendicular to the tube axis O1 direction of the resin tube 11. In this embodiment, the optical fibers 12 are arranged at 90° intervals in a cross section perpendicular to the tube axis O1 direction of the resin tube 11. In other words, the four optical fibers 12 are positioned at equal intervals around the tube axis O1 within the cylindrical wall 11A.

The folded portion 12A is the portion of the optical fiber 12 that protrudes from the end of the plastic tube 11. In this embodiment, the folded portion 12A is formed by joining the end of an optical fiber 12 to the end of another optical fiber 12 that is adjacent to the optical fiber 12 around the tube axis O1 (circumferential direction of the plastic tube 11). As a result, the two folded portions 12A do not intersect when viewed from the direction of the tube axis O1.

The length L1 of the folded portion 12A is not particularly limited, but is, for example, 150 to 400 mm. If the length L1 is equal to or greater than the above-mentioned lower limit, it is easy to join the ends of the optical fibers 12 together. If the length L2 is equal to or less than the above-mentioned upper limit, it is possible to prevent the overall length of the optical fiber-supported resin tube 10 from becoming excessively long.

Even if there are six or more optical fibers 12 along the resin tube 11, by joining adjacent optical fibers 12 in the circumferential direction, the folded portions 12A do not intersect with each other when viewed from the tube axis O1 direction.

<Resin pipe>
The resin pipe 11 is formed by molding a resin composition (A) containing a resin (A) into a cylindrical shape and curing the resin composition (A). The resin pipe 11 is composed of a cylindrical wall 11A.

The outer diameter R1 of the resin tube 11 is preferably 20 mm or more and 50 mm or less, and more preferably 30 mm or more and 40 mm or less. If the outer diameter R1 is equal to or greater than the above-mentioned lower limit, signal interference between the optical fibers 12 can be better suppressed. If the outer diameter R1 is equal to or less than the above-mentioned upper limit, the resin tube 11 can more easily follow the displacement of the structure, further improving the accuracy of measurements using the optical fiber-supported resin tube 10.

The thickness of the cylindrical wall 11A is preferably 2.5 mm or more and 10 mm or less, and more preferably 3 mm or more and 5 mm or less. If the thickness of the cylindrical wall 11A is equal to or greater than the lower limit, even if the cylindrical wall 11A is damaged during installation, the optical fiber 12 will not be exposed from the cylindrical wall 11A, further reducing the transmission loss of the optical fiber 12. If the thickness of the cylindrical wall 11A is equal to or less than the upper limit, the resin tube 11 will be able to more easily follow the displacement of the structure, further improving the accuracy of measurements using the optical fiber-supported resin tube 10.

Examples of the resin (A) include polyolefin resins such as polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. Examples of polyethylene include low-density polyethylene (density: 910 kg/m ^{or more} and less than 930 kg/ ^m ), medium-density polyethylene (density: 930 kg/m or ^more and less than 942 kg/ ^m ), and high-density polyethylene (density: 942 kg/m ³ or more). One type of resin (A) may be used alone, or two or more types may be used in combination.

Resin (A) is preferably polyethylene, more preferably medium density polyethylene (MDPE) or high density polyethylene (HDPE), and more preferably a mixture of MDPE and HDPE.
When the resin (A) is a mixture of MDPE and HDPE, the mass ratio (M/H ratio) of MDPE to HDPE (MDPE/HDPE) is preferably 40/60 to 90/10, more preferably 60/40 to 90/10. When the M/H ratio is equal to or greater than the lower limit, molding shrinkage is reduced, and transmission loss can be further reduced. When the M/H ratio is equal to or less than the upper limit, the dimensions of the resin pipe 11 can be more stable.

When resin (A) contains a resin other than polyolefin, the content of the resin other than polyolefin relative to the total mass (100 mass%) of resin (A) is preferably 50 mass% or less, more preferably 30 mass% or less, and may be 0 mass%.

Relative to the total mass (100 mass%) of resin composition (A), the content of resin (A) is preferably 80 mass% or more, more preferably 90 mass% or more, and may be 100 mass%.

The resin composition (A) may contain components other than the resin (A) (optional component (A)). That is, the resin pipe 11 may contain the optional component (A). Examples of the optional component (A) include known additives used in polyolefin resins, such as plasticizers, colorants (pigments, dyes), lubricants, UV absorbers, and antioxidants.

<Optical fiber>
The optical fiber 12 is not particularly limited, and may be an optical fiber strand not coated with a coating resin layer, or a coated fiber in which an optical fiber strand is coated with a coating resin layer. When a coated fiber is used as the optical fiber 12, the coating resin layer may be one layer or two or more layers.

The optical fiber may be an optical fiber having a core and a cladding, but the present invention is not limited to this, and the optical fiber may not have a cladding.
Examples of materials for the optical fiber include resins such as vinyl chloride resin and acrylic resin, and quartz glass.

The coating resin layer is a cured product of a resin composition (B) containing a resin (B). Examples of the resin (B) include ultraviolet-curable resins, polyolefins, polyesters, polyamides, fluororesins, and polyimides. These resins (B) may be elastomers containing hard segments and soft segments. The resin (B) can be appropriately selected from the viewpoints of process suitability, environmental resistance, heat resistance, economic efficiency, etc.
The resin (B) may be used alone or in combination of two or more. The coating resin layer may be a single layer or a multilayer.

The resin composition (B) may contain a component (optional component (B)) other than the resin (B). That is, the coating layer 14 may contain the optional component (B).
Examples of the optional component (B) include plasticizers, colorants (pigments, dyes), lubricants, ultraviolet absorbers, and antioxidants.

The optical fiber 12 may be a single-mode optical fiber, a multi-mode optical fiber, or a polarization-maintaining optical fiber. For measurements in the present invention, a single-mode optical fiber is preferred.

The outer diameter of the optical fiber 12 is preferably, for example, 0.1 to 3 mm, and more preferably 0.15 to 2 mm. If the outer diameter is equal to or greater than the above-mentioned lower limit, the mechanical strength of the optical fiber 12 can be further increased. If the outer diameter is equal to or less than the above-mentioned upper limit, the coating resin layer can be more easily removed.

<Method of manufacturing optical fiber-supported resin tube>
A method for manufacturing the optical fiber-supported resin tube of this embodiment will be described.
The molten resin composition (A) and the optical fiber 12 are fed into a mold, and an extrusion molded body in which the resin tube 11 and the optical fiber 12 are integrally molded is extruded from the mold of the extrusion molding machine. The extrusion molded body is cooled while being taken up by a take-up machine installed downstream of the mold, and the resin composition (A) in the extrusion molded body is hardened. The extrusion molded body is then cut to a desired length. The resin tube 11 at the end of the cut extrusion molded body is cut to expose the optical fiber 12 of the desired length.
The ends of two optical fibers 12 adjacent to each other in the circumferential direction of the resin tube 11 are joined together to form a folded portion 12A, thereby forming the optical fiber-supported resin tube 10. Examples of methods for joining the ends of the optical fibers 12 include thermal fusion with a laser.
The resin tube 11 is cut at the end opposite to the folded portion 12A of the optical fiber-supported resin tube 10 to expose the end of the optical fiber 12. This exposed end (connection end) of the optical fiber 12 is connected to an analytical instrument or the like.
Alternatively, the optical fiber-supported resin tube can be manufactured by the following method. A resin tube 11 is prepared in advance, and grooves are formed in the resin tube 11 from the outer surface to the inner surface. Next, the optical fiber 12 is inserted, and then a resin composition is filled into the recess through the opening of the groove and cured, thereby manufacturing the optical fiber-supported resin tube. The exposure of the optical fiber and the treatment of the end can be performed in the same manner as in the case of an extrusion-molded product.

(Pipe end member)
The tube end member 20 has an inner tube body 20A and an outer tube body 20B. As shown in Figures 2 and 3, when the tube end member 20 is attached to the optical fiber-supported resin tube 10 (attached state), the inner tube body 20A is located inside the outer tube body 20B.
In the mounted state, the outer surface of the inner cylinder 20A is spaced apart from the inner surface of the outer cylinder 20B, and the space between the outer surface of the inner cylinder 20A and the inner surface of the outer cylinder 20B forms a housing section 21. In the mounted state, the folded-back section 12A of the optical fiber 12 is located in the housing section 21. This makes it difficult for external force to be applied to the optical fiber 12, and damage to the optical fiber 12 can be prevented.

<Inner cylinder>
1 to 4, the inner cylindrical body 20A has a cylindrical main body 24, a flange 23, and two ridges (first ridges) 22. The flange 23 is located at one end of the main body 24 and protrudes radially from the main body 24. The ridges 22 are located on the outer peripheral surface of the main body 24 and extend in the direction of the tube axis O1. In this embodiment, the main body 24, the flange 23, and the ridges 22 form the cylindrical wall of the inner cylindrical body 20A.

The flange portion 23 surrounds the periphery of the opening at one end of the main body portion 24. The flange portion 23 may be discontinuous.

The ridges 22 extend from the flange portion 23 to the other end of the main body portion 24. In this embodiment, the ridges 22 are continuous from the flange portion 23 to the other end, but the ridges 22 may be discontinuous.
In this embodiment, the inner cylindrical body 20A has two ridges 22. The two ridges 22 are positioned point-symmetrically with respect to the tube axis O1. In the installed state, the two ridges 22 divide the interior of the housing portion 21 into two spaces. The number of ridges 22 is not limited to two, and may be one, or three or more. The number of ridges 22 can be determined appropriately depending on the number of folded-back portions 12A.

The inner cylindrical body 20A is a cured product of a resin composition containing the resin (C).
Resin (C) is the same as resin (A). Resin (C) may be the same as or different from resin (A).
The resin composition (C) may contain the same optional components as the resin composition (A).

The outer diameter r1 of the inner cylindrical body 20A (the outer diameter of the flange portion 23) is preferably equal to the outer diameter R1 of the optical fiber-carrying resin tube 10.
The inner diameter r2 of the inner cylindrical body 20A is preferably equal to the inner diameter R2 of the optical fiber carrying resin tube 10.
In this specification, "equivalent" length means that the difference therebetween is less than ±5%.

The length L2 of the inner cylindrical body 20A is determined taking into account the length L1 of the folded portion 12A, and is, for example, set to be equal to or greater than length L1. If length L2 is equal to or greater than length L1, the folded portion 12A can be easily accommodated within the accommodation portion 21 formed by the inner cylindrical body 20A and the outer cylindrical body 20B. It is more preferable that the length obtained by subtracting the flange portion 23 from length L2 be equal to or greater than length L1.

The height of the flange portion 23 (the length from the surface of the main body portion 24 to the tip) is set to be equal to or less than the difference between the inner diameter r3 and the outer diameter r2 of the outer cylinder body 20B described later.
In this embodiment, the height h of the ridge 22 may be any height that can define the storage section 21, and is preferably equal to or less than the height of the flange section 23.
The width W of the ridge 22 is not particularly limited and is determined appropriately taking into consideration the outer diameter r1 and the like.

<Outer cylinder>
As shown in FIG. 5, the outer cylinder body 20B is a cylindrical member having a space 26 therein.
In the attached state, the outer cylinder 20B covers the entire inner cylinder 20A and a part of the optical fiber carrying resin tube 10. In the attached state, the outer cylinder 20B is joined to the resin tube 11 at the part covering the optical fiber carrying resin tube 10.

The thickness t of the cylindrical wall forming the outer cylindrical body 20B is, for example, 2 to 5 mm.

The inner diameter r3 of the outer cylinder 20B needs only to be large enough to accommodate the inner cylinder 20A and the optical fiber-carrying resin tube 10. In other words, the inner diameter r3 is equal to or greater than the outer diameter R1 of the optical fiber-carrying resin tube 10. The inner diameter r3 is also equal to or greater than the outer diameter r2 of the inner cylinder 20A.

In this embodiment, the length L3 of the outer tube 20B is set to a length that covers the inner tube 20A and also covers a portion of the resin tube 11. While the length L3 may be a length that covers only the inner tube 20A, from the perspective of more reliably joining the tube end member 20 to the optical fiber-carrying resin tube 10, it is preferable that the length L3 be a length that covers a portion of the resin tube 11.

The outer cylinder body 20B is a cured product of a resin composition (D) containing a resin (D).
Resin (D) is the same as resin (C). Resin (D) may be the same as or different from resin (C).
The resin composition (D) may contain the same optional components as the resin composition (C).

<Method of manufacturing tube end member>
The method for manufacturing the tube end member 20 includes a method in which the inner cylindrical body 20A and the outer cylindrical body 20B are each manufactured by injection molding.

(Method for manufacturing an optical fiber-supporting resin tube with tube end members)
An example of a method for manufacturing (constructing) an optical fiber-carrying resin tube with tube end members will be described below.
The manufacturing method of the present invention involves positioning the inner cylinder 20A at the end of the resin tube 11 (step 1), aligning the folded portion 12A along the outer peripheral surface of the inner cylinder 20A (step 2), placing the outer cylinder 20B over the inner cylinder 20A to cover part or all of the outer peripheral surface of the inner cylinder 20A, and positioning the folded portion 12A in the storage section 21 between the outer peripheral surface of the inner cylinder 20A and the inner peripheral surface of the outer cylinder 20B (step 3).

In step 1, the inner tube 20A is positioned at the end (the end having the folded portion 12A) of the resin tube 11. If the optical fiber-carrying resin tube 10 does not have the folded portion 12A, the end of the resin tube 11 in the optical fiber-carrying resin tube 10 is cut to expose the optical fiber 12, and the ends of the exposed optical fiber 12 are joined together to form the folded portion 12A. The inner tube 20A is cut according to the length L1 of the folded portion 12A, and the length L2 of the inner tube 20A is adjusted. Adjusting the length L2 prevents the tube end member 20 from becoming excessively long.
The end of the inner cylindrical body 20A (the end without the flange 23) is brought into contact with the end of the resin tube 11 (the end toward the folded-back portion 12A) (Step 1). At this time, the folded-back portion 12A is aligned with the outer peripheral surface of the inner cylindrical body 20A. In addition, any one folded-back portion 12A is positioned in one region between the ridges 22 on the outer peripheral surface of the inner cylindrical body 20A, and the other folded-back portion 12A is positioned in the other region between the ridges 22 (Step 2). By accommodating the folded-back portions 12A in each region of the accommodation section 21 partitioned by the ridges 22, contact between the folded-back portions 12A can be prevented.
The resin pipe 11 and the inner cylindrical body 20A may be joined by heat fusion or the like, or may not be joined at all.
In this way, an optical fiber-carrying resin tube 110 with an inner tube is obtained, in which the inner tube 20A is joined to the end of the optical fiber-carrying resin tube 10 (FIG. 6).

Next, the outer tube 20B is placed over the inner tube-attached optical fiber-carrying resin tube 110 from the inner tube 20A side (FIG. 7). At this time, the inner tube-attached optical fiber-carrying resin tube 110 is inserted into the outer tube 20B so that the end of the inner tube 20A where the flange portion 23 is formed is flush with the end of the outer tube 20B. In addition, a part of the outer tube 20B is made to cover the resin tube 11 (step 3).
If necessary, the outer cylinder body 20B may be cut to adjust the length.

In step 3, the outer cylinder 20B and the resin pipe 11 are joined in the area where the outer cylinder 20B covers the resin pipe 11 (joining operation). Examples of methods for joining the outer cylinder 20B and the resin pipe 11 include electrical fusion, thermal fusion, and screw fastening. When screw fastening (fixing with a screw) is used, it is preferable to use a screw in which the diameter of the threaded portion (the portion having the helical thread) and the diameter of the screw head are equal and the top surface of the screw head is flush with the outer cylinder 20B. An example of such a screw is a so-called set screw.
When the outer tube 20B and the resin tube 11 are joined by electrical fusion or thermal fusion, it is preferable to perform the joining in a manner that avoids the position of the optical fiber 12.
If the fitting force between the outer cylindrical body 20B and the resin pipe 11 is sufficient, the joining operation may be omitted.
In this way, an optical fiber-carrying resin tube 1 (FIG. 2) with tube end members can be manufactured, in which one folded portion 12A is located in each of the two regions of the storage section 21 divided by the ridge 22.
The connecting end of the optical fiber-carrying resin tube 1 with the tube end member is connected to an analytical instrument or the like, and is used for distortion measurement, temperature measurement, and the like.

The tube end member of this embodiment can prevent damage to the folded-back portion of the optical fiber by being attached to the optical fiber-supporting resin tube.
In addition, the tube end member of this embodiment does not require heating of the optical fiber or its vicinity when it is attached to the optical fiber-supported resin tube, so transmission loss of the optical fiber can be reduced.
Furthermore, the length of the pipe end member of this embodiment can be adjusted by cutting the inner tube, preventing the pipe end member from becoming excessively long. Therefore, the length of the pipe end member can be easily adjusted at the construction site according to the length of the folded-back portion.

[Second embodiment]
A second embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the first embodiment are designated by the same reference numerals and their description will be omitted, and the following mainly describes the differences from the first embodiment.
The optical fiber-carrying resin tube 100 with a tube end member shown in FIG. 8 includes an optical fiber-carrying resin tube 10 and a tube end member 120 .

As shown in FIGS. 8 and 9, the pipe end member 120 has an inner cylindrical body 20A and an outer cylindrical body 120B.
8 to 10 , the outer tube body 120B has an outer tube wall 122 that forms the outer peripheral surface, and an inner tube wall 124 that is spaced apart from the outer tube wall 122 and is positioned closer to the tube axis O2 than the outer tube wall 122. The outer tube wall 122 and the inner tube wall 124 are positioned concentrically when viewed from the direction of the tube axis O2. A space 123 is formed between the outer tube wall 122 and the inner tube wall 124. This space 123 is large enough to accommodate the tube wall (including the main body, flange portion, and ridges) of the inner tube body 20A and the tube wall 11A of the resin tube 11.

In the attached state, the peripheral wall of the inner cylinder 20A is located within the space 123. In the attached state, the tube end member 120 has a storage section 121 between the outer surface of the peripheral wall of the inner cylinder 20A (the outer surface of the inner cylinder 20A) and the inner surface of the outer cylinder wall 122 of the outer cylinder 120B (the inner surface of the outer cylinder 120B). The folded-back section 12A is located in the storage section 121. This makes it less likely that external forces will be applied to the optical fiber 12, preventing damage to the optical fiber 12.

The manufacturing method for the optical fiber-supported resin tube 100 with tube end members of this embodiment differs from the manufacturing method of the first embodiment in that the cylindrical wall of the inner cylindrical body 20A is inserted into the space 123.

In this embodiment, the pipe end member has an outer tube wall and an inner tube wall, with a space between the outer and inner tube walls, and the tube wall of the inner tube is received in this space, resulting in superior workability.

Other Embodiments
In the first and second embodiments, the inner cylinder has a ridge, but the present invention is not limited to this, and the inner cylinder may not have a ridge. Alternatively, the inner cylinder may not have a ridge, and the outer cylinder may have a ridge (second ridge).
In order to prevent the folded-back portions from contacting each other within the storage portion, it is preferable that at least one of the inner and outer cylindrical bodies has a ridge that defines the storage portion. When the outer cylindrical body has a ridge, the outer cylindrical body has a ridge on its inner peripheral surface (the surface facing the outer peripheral surface of the inner cylindrical body).

In the first and second embodiments, the folded portion is formed by joining the ends of two optical fibers, but the present invention is not limited to this. The folded portion may also be formed by bending a single optical fiber.

In the first and second embodiments, the entire inner cylinder is inserted into the outer cylinder when the device is attached. However, the present invention is not limited to this, and only a portion of the inner cylinder may be inserted into the outer cylinder as long as a storage section can be formed.

1, 100 Optical fiber-carrying resin tube with tube end member 10, 910, 910A Optical fiber-carrying resin tube 11 Resin tube 11A Tube wall 12 Optical fiber 12A Folded portion 20, 120 Tube end member 20A Inner tube body 20B, 120B Outer tube body 21, 121 Storage portion 22 Convex rib 122 Outer tube wall 124 Inner tube wall O1, O2 Tube axis

Claims (8)

A tube end member for an optical fiber-carrying resin tube, which is used for an optical fiber-carrying resin tube having a cylindrical resin tube and two or more optical fibers located within a cylindrical wall of the resin tube and extending in an axial direction of the resin tube, and which has a folded portion on the outer side of the axial direction of the resin tube, in which an arbitrary optical fiber and another arbitrary optical fiber adjacent to the arbitrary optical fiber in the circumferential direction of the resin tube are connected to each other,
It has an inner cylinder and an outer cylinder,
The inner cylinder can be inserted into the outer cylinder in part or in whole,
A tube end member for an optical fiber-supported resin tube, which, when part or all of the inner tube is inserted into the outer tube, forms a storage section between the outer surface of the inner tube and the inner surface of the outer tube to receive the optical fiber in the folded-back portion. the outer peripheral surface of the inner cylindrical body has one or more first ridges extending in the axial direction of the inner cylindrical body;
2. The tube end member for an optical fiber-carrying resin tube according to claim 1, wherein the first ridge defines the housing portion when the outer tube is placed over the inner tube. the inner peripheral surface of the outer cylindrical body has one or more second ridges extending in the tube axis direction of the outer cylindrical body;
3. The tube end member for an optical fiber-carrying resin tube according to claim 1, wherein the second ridge defines the housing portion when the outer tube is placed over the inner tube. the outer cylinder body has an outer cylinder wall and an inner cylinder wall spaced apart from the outer cylinder wall and closer to the tube axis than the outer cylinder wall,
4. The tube end member for an optical fiber-carrying resin tube according to claim 1, wherein the tube wall of the inner tube is received between the outer tube wall and the inner tube wall. A tube end member for an optical fiber-supported resin tube according to any one of claims 1 to 4, and the optical fiber-supported resin tube,
a tube end member for the optical fiber-supporting resin tube is provided at an end of the resin tube;
The optical fiber-carrying resin tube with a tube end member is configured such that the folded portion is located within the housing portion. The optical fiber-carrying resin tube with tube end member described in claim 5, wherein the tube end member for the optical fiber-carrying resin tube is fixed to the resin tube with screws. 6. A method for manufacturing an optical fiber-supported resin tube with a tube end member according to claim 5,
The inner cylindrical body is positioned at the end of the resin pipe,
the folded portion is aligned with the outer peripheral surface of the inner cylindrical body,
A method for manufacturing an optical fiber-supported resin tube with a tube end member, in which the outer tube body is placed over the inner tube body to cover part or all of the outer peripheral surface of the inner tube body, and the folded portion is positioned in the accommodating portion between the outer peripheral surface of the inner tube body and the inner peripheral surface of the outer tube body. The method for manufacturing a resin tube carrying an optical fiber with a tube end member according to claim 7, wherein the outer tube is fixed to the resin tube with screws.