JP2005128074A - Optical fiber and optical fiber sensor to measure physical quantity of concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber in which productivity is high, bending rigidity is made uniform and handling is made easy and to provide an optical fiber sensor to measure physical quantity of a concrete structure. <P>SOLUTION: An anti-side pressure coating layer 2 is formed on the outer periphery of a primary coated optical fiber 1 and a foamed coating layer 3 is formed on the outer periphery of the anti-side pressure coating layer 2 so that bending rigidity is made uniform and handling during a burying work is improved. Moreover, productivity is not reduced because no emboss process is required and only an extrusion process is needed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber sensor for measuring physical quantities of optical fibers and concrete structures.

  An optical fiber sensor was fixed by embedding an optical fiber in a concrete structure such as a building, a bridge, a tunnel, etc., and entering light at one or both ends of the optical fiber, and measuring scattered light and optical loss. In recent years, a method of measuring continuous strain and temperature distribution in the length direction of a place has been adopted.

  FIG. 4 is an external perspective view of a conventional optical fiber sensor.

  The conventional optical fiber sensor has a structure in which the outer periphery of the optical fiber 1 is covered with glass FRP2, and the outer periphery of the glass FRP2 is covered with a coating layer 8 having an uneven embossing 7 (for example, , See Patent Document 1).

  In this way, by coating the glass FRP 2 on the outer periphery of the optical fiber 1, an optical fiber that is not affected by water or electromagnetic induction and prevents the optical fiber 1 from being disconnected due to pressure or weight when placing concrete. It becomes a sensor.

  Also, by providing the outer layer with an uneven embossing 7, the cement grains and sand in the concrete enter the outer layer, and sufficient adhesion can transmit the strain and temperature distribution of the concrete structure to the optical fiber 1. An optical fiber sensor having

  The prior art document information related to the invention of this application includes the following.

Japanese Patent Laid-Open No. 2002-23030

  However, although the above-described optical fiber sensor has sufficient adhesion that can transmit the strain and temperature distribution of the concrete structure to the optical fiber 1, it is necessary to provide the outer layer with an uneven embossing 7. Therefore, there is a problem that the manufacturing process must be added, resulting in a decrease in productivity.

  In addition, there is a problem in that the bending rigidity of the optical fiber becomes non-uniform due to the unevenness on the outer periphery.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical fiber for solving the above problems, high productivity, uniform bending rigidity and easy handling, and an optical fiber sensor for measuring a physical quantity of a concrete structure.

  The invention of claim 1 is an optical fiber comprising an optical fiber, a side pressure-resistant coating layer formed on the outer periphery of the optical fiber, and a foam coating layer formed on the outer periphery of the side pressure-resistant coating layer. It is.

  A second aspect of the present invention is the optical fiber according to the first aspect, wherein the foaming rate of the foam coating layer increases from the inside toward the outside.

  The invention according to claim 3 is the optical fiber according to claim 1 or 2, wherein the foam coating layer has a plurality of layer structures.

  Invention of Claim 4 is an optical fiber in any one of Claim 1 to 3 whose outside foaming rate is 40%-60% among the said foaming coating layers.

  A fifth aspect of the present invention is the optical fiber according to any one of the first to fourth aspects, wherein the overall foaming rate of the foam coating layer is 30% to 40%.

  The invention of claim 6 is an optical fiber sensor embedded in a concrete structure or the like for measuring various physical quantities, an optical fiber, and a lateral pressure-resistant coating layer formed on the outer periphery of the optical fiber. An optical fiber sensor for measuring a physical quantity of a concrete structure provided with a foam coating layer formed on the outer periphery of the side pressure resistant coating layer.

  The invention according to claim 7 is the optical fiber sensor for measuring a physical quantity of a concrete structure according to claim 6, wherein the foaming rate of the foam coating layer increases from the inside toward the outside.

  The invention according to claim 8 is the optical fiber sensor for measuring a physical quantity of a concrete structure according to claim 6 or 7, wherein the foam coating layer has a plurality of layer structures.

  A ninth aspect of the present invention is the optical fiber sensor for measuring a physical quantity of a concrete structure according to any one of the sixth to eighth aspects, wherein the foam ratio of the outer side of the foamed coating layer is 40% to 60%.

  A tenth aspect of the present invention is the optical fiber sensor for measuring a physical quantity of a concrete structure according to any one of the sixth to ninth aspects, wherein the expansion ratio of the foam coating layer is 30% to 40%.

  According to the present invention, the side pressure-resistant coating layer is formed on the outer periphery of the optical fiber, and the foam coating layer is formed on the outer periphery of the side-pressure-resistant coating layer, so that the bending rigidity can be made uniform, and the embedment work The handling at the time is improved. In addition, since extruding can be performed without embossing, productivity is not reduced.

  In short, according to the present invention, it is possible to provide an optical fiber having high productivity, uniform bending rigidity, and easy handling, and an optical fiber sensor for measuring a physical quantity of a concrete structure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of an optical fiber of the present invention.

  The optical fiber may be an optical fiber 1 and a side pressure-resistant coating layer (for example, fiber reinforced plastic such as glass FRP) formed on the outer periphery of the optical fiber 1 or a metal tube for temperature measurement. .) 2 and a foamed coating layer (for example, polyethylene) 3 formed on the outer periphery of the side pressure-resistant coating layer 2.

  The foam coating layer 3 has a higher foaming rate from the inside toward the outside. The foam coating layer 3 preferably has an outer foaming rate of 40% to 60% and an overall foaming rate of 30% to 40%.

  In this way, the side pressure-resistant coating layer 2 is formed on the outer periphery of the optical fiber 1, and the foam coating layer 3 is formed on the outer periphery of the side-pressure-resistant coating layer 2, thereby making the bending rigidity uniform without embossing. Therefore, the productivity is not lowered and the handleability is improved. In addition, the adhesion of the present optical fiber to a concrete structure and soil is improved.

  FIG. 2 is a sectional view showing another embodiment of the optical fiber of the present invention.

  The difference from the optical fiber shown in FIG. 1 is that the foam coating layer has a two-layer structure composed of the foam coating layers 3a and 3b.

  In this optical fiber, the foaming rate of the outer foam coating layer 3a is higher than the foaming rate of the inner foam coating layer 3b.

  Even if it has such a structure, the effect similar to the optical fiber shown in FIG. 1 is acquired.

  FIG. 3 is a sectional view showing another embodiment of the optical fiber of the present invention.

  The difference from the optical fiber shown in FIG. 2 is that it has a three-layer foam coating layer 3a, 3b, 3c.

  Even if it has such a structure, the effect similar to the optical fiber shown in FIG. 1 is acquired.

  In the present embodiment, the case where the number of foam coating layers is two and three has been described, but the present invention is not limited to these and may be four or more layers.

  Here, the foamed coating layer is expected to have low adhesion to a concrete structure when the foaming rate is low, and is easy to break when the foaming rate is high.

  Therefore, the present inventors consider that it is optimal to form a foam coating layer having bending rigidity equivalent to that of the coating layer 8 on which the uneven embossing 7 as shown in FIG. Thus, an expansion ratio of 30% to 40% of the entire foam coating layer was obtained.

  In the present invention, the inner foaming rate is lowered, and the outer foaming rate is set higher, so that the foamed coating layer is prevented from being broken and peeled off by an external force while having adhesion to a concrete structure or soil. It has become.

Usage, application system, etc .;
The optical fiber described in FIG. 1 to FIG. 3 is embedded in a concrete structure or underground to form a physical quantity measurement optical fiber sensor for a concrete structure, and light is incident on one or both ends of the physical quantity measurement optical fiber sensor. By measuring the reflected light, scattered light (for example, backscattered light), and optical loss, the length of the place where the optical fiber sensor is embedded continuously in the concrete structure, underground strain, temperature distribution, etc. Various physical quantities can be measured.

  In the above, according to the invention described in claim 1 or 6, since the outer layer of the optical fiber is a foam coating layer, it can have adhesiveness with concrete without performing uneven embossing. In addition, the bending rigidity can be made uniform as compared with the coating layer having the uneven embossing.

  Further, the foam coating layer is made of glass FRP, concrete structure, soil and the like by making the outer portion of the coating layer have a high foaming rate and the inner portion of the foaming coating layer with a low foaming rate as in the invention of claim 2 or 7. It is possible to improve the adhesion.

  Furthermore, the foam coating layer can be constituted by a plurality of foam coating layers as in the invention described in claim 3 or 8. In this case, it is necessary to make the expansion ratio of the foam layer of the outer layer higher than the expansion ratio of the inside. Since each layer has a single foaming rate, the foam coating layer can be formed with a simple configuration. Further, the foam coating layer can be constituted by one layer that changes so that the foam layer becomes higher from the inside toward the outside. In this case, only one coating step is required, and productivity is improved.

  The outermost foam coating layer or the outer portion of the foam coating layer has a foaming rate of 40% to 60% as in the invention according to claim 4 or 9, thereby stabilizing the adhesion to a concrete structure or soil. Can be made.

  Furthermore, as in the invention described in claim 5 or 10, a foamed coating layer capable of preventing breakage and peeling due to external force can be formed by setting the foaming ratio of the entire foamed coating layer to 30% to 40%. it can.

  In the above, according to the present invention, an optical fiber sensor for measuring a physical quantity of a concrete structure capable of accurately transmitting various physical quantities such as a concrete structure, underground strain, temperature distribution, and the like to an optical fiber, is provided. In the length direction of the place where the optical fiber is embedded by measuring the reflected light, scattered light (for example, backscattered light), and light loss by making light incident on one or both ends of the optical fiber sensor for use, Various physical quantities such as concrete structure, underground strain, temperature distribution, etc. can be measured continuously.

It is sectional drawing which shows one Embodiment of the optical fiber of this invention. It is sectional drawing which shows other embodiment of the optical fiber of this invention. It is sectional drawing which shows other embodiment of the optical fiber of this invention. It is an external appearance perspective view of the conventional optical fiber sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber strand 2 Side pressure-resistant coating layer 3 Foam coating layer

Claims (10)

  An optical fiber comprising: an optical fiber; a side pressure-resistant coating layer formed on the outer periphery of the optical fiber; and a foam coating layer formed on the outer periphery of the side-pressure-resistant coating layer.   The optical fiber according to claim 1, wherein a foaming rate of the foam coating layer increases from the inside toward the outside.   The optical fiber according to claim 1, wherein the foam coating layer has a plurality of layer structures.   The optical fiber according to any one of claims 1 to 3, wherein an outer foaming ratio of the foam coating layer is 40% to 60%.   The optical fiber according to any one of claims 1 to 4, wherein the foaming rate of the foam coating layer is 30% to 40%.   In an optical fiber sensor embedded in a concrete structure or the like for measuring various physical quantities, an optical fiber, a side pressure-resistant coating layer formed on an outer periphery of the optical fiber, and the side pressure-resistant coating layer An optical fiber sensor for measuring a physical quantity of a concrete structure, comprising a foam coating layer formed on an outer periphery.   The optical fiber sensor for measuring a physical quantity of a concrete structure according to claim 6, wherein the foaming rate of the foam coating layer increases from the inside toward the outside.   The optical fiber sensor for measuring a physical quantity of a concrete structure according to claim 6 or 7, wherein the foam coating layer has a plurality of layer structures.   The optical fiber sensor for measuring a physical quantity of a concrete structure according to any one of claims 6 to 8, wherein an outer foaming ratio of the foam coating layer is 40% to 60%. The optical fiber sensor for measuring a physical quantity of a concrete structure according to any one of claims 6 to 9, wherein the foaming ratio of the foam coating layer is 30% to 40%.

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