JP3857064B2 - Optical cable for strain detection - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a strain detection optical cable that is used by being fixed on a measurement object in order to detect distortion in the measurement object.
[0002]
[Prior art]
For example, as shown in FIG. 3A, a long optical fiber cable 30 is placed on a strain measurement target 40 such as a ground such as a roadside slope or a building such as a roadway or an inner wall surface of a tunnel. Measure the strain distribution of the optical fiber with a measuring device such as BOTDR, which is arranged in a slack-free or tensioned state and fixed intermittently and combines Brillouin optical amplification and OTDR (optical time domain reflectometer). A system has been proposed. In the figure, reference numeral 31 indicates a fixed portion of the optical cable.
According to such a system, for example, as shown in FIG. 3B, when the measurement object 40 is distorted due to a crack or the like, the optical cable 30 in the vicinity thereof is also distorted to propagate light. Since the state changes, the occurrence of a crack or the like can be detected by monitoring this.
[0003]
By the way, when constructing such a system, as a method of fixing the optical cable 30 on the measurement object 40, for example, a fixture 32 such as two plastic plates or metal plates as shown in FIG. Then, as shown in FIG. 4 (b), the optical cable 30 is sandwiched, and the fixing tool 32 is fixed to the measurement object 40 by fixing means such as a set screw 34. For example, as shown in FIG. Then, as shown in FIG. 5B, the optical cable 30 is pushed into the groove 36 using a plate-like fixing tool 35 having a groove 36 formed on the upper surface, and the fixing tool 35 is fixed by fixing means such as a set screw 34. A method of fixing to the measurement object 40 is generally considered.
[0004]
[Problems to be solved by the invention]
However, such a fixing method has not been sufficiently fixed. That is, since the sheath which is the outermost layer of the optical cable 30 is made of a plastic material and has a smooth surface, there is a problem that the optical cable 30 is easily slipped at the fixing portion 31.
For example, when the measurement object 40 is distorted between the adjacent fixed portions 31 and 31, the optical cable 30 may slip in the length direction within the fixtures 32 and 35, and then There was a problem that accurate measurement could not be performed.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent slippage of an optical cable in the fixing portion 31 and improve accuracy and stability of distortion detection.
[0006]
[Means for Solving the Problems]
The problem is an optical cable that is used by being fixed on the measurement object in order to detect distortion in the measurement object, and the optical fiber core wire and the tensile body are collectively covered with a sheath, This can be solved by an optical cable for strain detection, characterized in that solid particles made of an inorganic material are mixed in the sheath.
The average particle diameter of the solid particles is preferably 5 μm or more and 500 μm or less, and the mixing amount of the solid particles in the sheath is preferably 1% or more and 50% or less by volume ratio.
[0007]
Alternatively, the strain detection optical cable is characterized in that the optical fiber core and the tensile body are collectively covered with a sheath, and solid particles made of an inorganic material are attached on the surface of the sheath. Can be solved.
The average particle diameter of the solid particles is preferably 5 μm or more and 500 μm or less, and the amount of the solid particles adhering to the sheath surface is preferably 0.5% or more and 80% or less by surface area ratio.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
FIG. 1 is a cross-sectional view showing a first example of a strain detection optical cable (hereinafter sometimes simply referred to as an optical cable) according to the present invention.
In the optical cable of this embodiment, the four optical fiber cores 1 are arranged in parallel and in a row, and the sheath 2 is collectively covered on the circumference thereof, and two strength members 3 are provided in the sheath 2. Is embedded so as to be parallel to the optical fiber core wire 1. In addition, solid particles 5 made of an inorganic material are mixed in the sheath 2.
[0009]
The optical fiber core wire 1 is not particularly limited, and a general single mode optical fiber can be used. The number and arrangement of the optical fiber cores 1 constituting the optical cable can be changed as appropriate.
As the tensile body 3, for example, a steel wire, a stainless steel wire (SUS wire), a fiber reinforced plastic (FRP), or the like is used. The number and arrangement of the strength members 3 can be changed as appropriate.
[0010]
The sheath 2 is formed of a resin material obtained by mixing solid particles 5 made of an inorganic material into a general sheath material such as polyethylene, and the solid particles 5 in the optical cable are embedded in the sheath 2. Some are exposed on the surface of the sheath 2. As the solid particles 5, silica powder, talc, alumina powder, metal filler and the like are preferably used.
Further, as a result of the examination, it is preferable that the average particle diameter of the solid particles 5 is 5 μm or more and 500 μm or less, and the mixing amount of the solid particles 5 in the sheath 2 is 1% or more and 50% or less by volume ratio. Even if the average particle size of the solid particles 5 is too small or the amount of mixing is too small, the fixing in the fixing portion 31 is insufficient. On the other hand, if the average particle size of the solid particles is too large, or if the mixing amount is too large, the manufacturability of the optical cable is degraded.
The thickness of the sheath 2 is preferably set to about 0.5 mm to 2 mm, for example.
[0011]
The optical cable of the present embodiment is used by being fixed on a measurement object for which distortion is to be detected. Specifically, for example, as shown in FIG. 4, a fixture 32 sandwiched between two plastic plates or metal plates, or in a groove 36 provided on the upper surface of the plate-like base as shown in FIG. A fixing device of a type that is fixed by the frictional force between the surface of the optical cable and the fixing device, such as a fixing device 35 for pushing the optical cable into the fixing device, is preferably used. A method of fixing the fixtures 32 and 35 to the measurement object is preferable.
According to the present embodiment, since the sheath 2 is formed of a resin material obtained by mixing solid particles 5 made of an inorganic material into the sheath material, a part of the solid particles 5 protrudes from the surface. That is, the surface of the sheath 2 is uneven by the solid particles 5, thereby increasing the frictional force on the surface of the sheath 2. Therefore, the frictional force between the optical cable and the fixtures 32 and 35 that sandwich or hold the optical cable increases, and the optical cable is less likely to slip at the fixing portion 31.
[0012]
FIG. 2 is a sectional view showing a second example of the strain detection optical cable of the present invention.
The optical cable of the present embodiment is different from the first example in that solid particles are not mixed in the sheath 12 and solid particles 15 made of an inorganic material are attached only to the surface of the sheath 12. Is a point.
2, the same components as those in FIG. 1 may be denoted by the same reference numerals and the description thereof may be omitted.
[0013]
In this embodiment, the sheath 12 is made of a general sheath material such as polyethylene, and solid particles 15 made of an inorganic material are attached to the surface thereof. As the solid particles 15, silica powder, talc, alumina powder, metal filler, and the like are preferably used. The method for attaching the solid particles 15 to the surface of the sheath 12 is not particularly limited. For example, the solid particles 15 are attached by contacting the solid particles 15 in a melted state by a method using an adhesive or by heating the surface of the sheath 12. Or the like can be used.
As a result of the examination, it is preferable that the average particle diameter of the solid particles 15 is 5 μm or more and 500 μm or less, and the amount of the solid particles 15 on the surface of the sheath 12 is 0.5% or more and 80% or less in terms of surface area. . Even if the average particle size of the solid particles is too small or the amount of adhesion is too small, the fixing in the fixing portion 31 is insufficient. On the other hand, if the average particle size of the solid particles 15 is too large, the manufacturability of the optical cable is deteriorated. It is difficult to make the amount of solid particles 15 attached more than 80%. The thickness of the sheath 2 is preferably set to about 0.5 mm to 2 mm.
[0014]
Similarly to the first example, the optical cable of the present embodiment is also used by being fixed on the measurement object when detecting distortion in the measurement object.
According to this embodiment, since the solid particles 15 are attached to the surface of the sheath 12, the surface has irregularities. As a result, the frictional force on the surface of the sheath 12 is increased, the frictional force between the optical cable and the fixtures 32 and 35 holding or gripping the optical cable is increased, and the optical cable is difficult to slip at the fixing portion 31.
[0015]
【Example】
Hereinafter, specific examples will be shown to clarify the effects of the present invention.
Example 1
An optical cable having the configuration shown in FIG. 1 was manufactured using a resin material in which silica powder having an average particle diameter of 50 μm was mixed in polyethylene so that the volume ratio was 20% as a constituent material of the sheath.
(Comparative Example 1)
An optical cable was produced in the same manner as in Example 1 except that polyethylene containing no silica powder was used as the constituent material of the sheath.
[0016]
(Experimental example 1)
The optical cables obtained in Example 1 and Comparative Example 1 are each sandwiched between two polyethylene plates, a load of 100 kg is applied in the direction from one plate to the other plate, the optical cable is fixed, and the optical cable is pulled out. The pulling force was evaluated by the method of measuring the load at the time.
As a result, the optical cable obtained in Example 1 was 10 times or more larger in pulling force than the optical cable obtained in Comparative Example 1.
[0017]
(Example 2)
The sheath was formed of polyethylene, and a silica powder having an average particle size of 50 μm was adhered to the surface thereof using a styrene-based adhesive so that the specific surface area ratio was 20%.
(Experimental example 2)
With respect to each of the optical cables obtained in Example 2 and Comparative Example 1, the pulling force was evaluated in the same manner as in Experimental Example 1.
As a result, the pulling force of the optical cable obtained in Example 2 was 10 times or more larger than that of the optical cable obtained in Comparative Example 1.
[0018]
【The invention's effect】
As described above, since the optical fiber for strain detection according to the present invention is roughened by forming irregularities due to solid particles on the surface thereof, a large frictional force is generated between the optical cable for strain detection and a fixture for gripping the optical cable. Is obtained. Therefore, the optical cable is less likely to slip at the fixing portion that fixes the strain detection optical cable to the measurement object, and the accuracy and stability of strain detection are improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a first embodiment according to the present invention.
FIG. 2 is a sectional view showing a second embodiment according to the present invention.
FIG. 3 is an explanatory diagram of a method for detecting distortion using an optical cable.
FIG. 4 is a perspective view showing an example of a fixture for an optical cable.
FIG. 5 is a perspective view showing another example of an optical cable fixture.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical fiber core wire, 2, 12 ... Sheath, 3 ... Strength body,
5, 15 ... Solid particles, 30 ... Optical cable for strain detection, 40 ... Measurement object.

Claims (4)

In order to detect distortion in the measurement object, an optical cable used by being fixed on the measurement object,
An optical cable for strain detection, wherein an optical fiber core and a tensile body are collectively covered with a sheath, and solid particles made of an inorganic material are mixed in the sheath. 2. The strain detection according to claim 1, wherein an average particle diameter of the solid particles is 5 μm or more and 500 μm or less, and a mixing amount of the solid particles in the sheath is 1% or more and 50% or less by volume ratio. Optical cable. In order to detect distortion in the measurement object, an optical cable used by being fixed on the measurement object,
An optical cable for strain detection, wherein an optical fiber core and a tensile body are collectively covered with a sheath, and solid particles made of an inorganic material are attached to the surface of the sheath. 2. The strain according to claim 1, wherein an average particle diameter of the solid particles is 5 μm or more and 500 μm or less, and an adhesion amount of the solid particles on the surface of the sheath is 0.5% or more and 80% or less in a surface area ratio. Optical cable for detection.

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