JP2002062120A - Optical fiber grating mounting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and easily handled optical fiber grating mounting structure. SOLUTION: By fixing the Bragg grating 102 of the optical fiber grating 106 onto a substrate 101 for mounting an object to be measured and embedding and molding the substrate 101 by an inexpensive hot-melt adhesive 201 superior in close contact, watertightness and handleability are improved. Tension exerted on an optical fiber 207 becomes a fastening force on the cylinders 202a and 202b by winding and fixing an optical fiber grating 208 between two cylinders 202a and 202b, the optical fiber 207 does not slip at all. As the distortion of a structure i.e., a displacement between the fixed points is directly transmitted to an optical fiber grating 206 by fixing fixing holes 203a and 203b formed at the centers of the cylinders 202a and 202b to the object to be measured, it is possible to accurately detect the distortion of the structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mounting structure for an optical fiber grating.

[0002]

2. Description of the Related Art An optical fiber grating is formed by irradiating a core through which light of an optical fiber propagates with ultraviolet rays to form a grating. With this grating,
This is a wavelength multiplexing optical device that reflects and branches only light in a specific wavelength band. This optical fiber grating
There is a characteristic that the wavelength of the demultiplexed light changes according to the strain applied to the optical fiber. If this characteristic is applied, for example, if an optical fiber grating is fixed to a structure such as a tunnel, only the distortion of the fixed part can be monitored in real time as a change in the center wavelength, and the danger of a tunnel collapse accident or the like can be monitored in advance. It can be foreseen and avoided. In addition, if gratings having different center wavelengths are formed in series, there is an advantage that low-cost monitoring is possible, such as that multiple points of distortion can be observed with one monitor facility.

[0003] This optical fiber grating is formed into an optical fiber having a glass fiber outer diameter of 125 µm, like an optical fiber for communication, and is very easily broken. For this reason, there is a demand for a mounting structure that can reliably transmit the distortion of the structure to the optical fiber grating and has good handleability.

FIG. 3 is an external perspective view showing a conventional example of a mounting structure of an optical fiber grating.

An optical fiber grating 106 in which a Bragg grating 102 is formed on an optical fiber 103
Is a substrate 10 for mounting an object to be measured, which is made of aluminum.
First, a Bragg grating 102 of an optical fiber grating 106 is fixed with an adhesive 104, and is fixed to a structure with a fixing hole 105 of a fixing terminal of a substrate 101, and is used for strain detection of the structure.

[0006]

The conventional optical fiber grating shown in FIG. 3 needs a waterproof structure because it is used outdoors such as in a tunnel.

[0007] However, the conventional optical fiber grating has the following problems.

(1) Rain water, groundwater, or the like is directly applied to the bonded portion, or the deterioration of the adhesive is caused by aging, and the optical fiber slides on the substrate due to a decrease in the adhesive force and the distortion is not accurately transmitted to the optical fiber.

(2) The portion where the optical fiber grating is formed is susceptible to external damage and poor in handling.

(3) The distortion may not be transmitted to the optical fiber accurately due to the elastic deformation of the adhesive.

An object of the present invention is to solve the above-mentioned problems and to provide a mounting structure of an optical fiber grating which is inexpensive and easy to handle.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, an optical fiber grating mounting structure according to the present invention comprises a Bragg grating for an optical fiber grating for a strain sensor having a Bragg grating formed by irradiating an optical fiber with ultraviolet light. Is fixed on a substrate for mounting an object to be measured, and then embedded together with a hot melt adhesive together with the substrate.

According to the mounting structure of the optical fiber grating of the present invention, an optical fiber grating for a strain sensor in which a Bragg grating is formed by irradiating an optical fiber with ultraviolet light is provided with at least two optical fibers formed on a substrate for mounting an object to be measured. The optical fibers on both sides of the Bragg grating are fixed on the cylinders by wrapping them around the cylinders and arranging them so as not to cover the circumference.

In the optical fiber grating mounting structure of the present invention, in addition to the above structure, it is preferable that the center of each of the cylinders is fixed to the object to be measured.

According to the present invention, after the formation portion of the Bragg grating is fixed on the substrate for mounting the object to be measured, the substrate is buried with an inexpensive hot-melt adhesive having excellent adhesion and waterproofness. And handling properties are also improved. Further, by winding and fixing the optical fiber grating between the cylinders, the tension applied to the optical fiber grating becomes a tightening force on the cylinder, so that the optical fiber grating does not slip. Further, by fixing the center of each of the cylinders to the object to be measured, the distortion of the structure, that is, the fluctuation between the fixed points is directly transmitted to the optical fiber grating, so that the distortion of the structure can be accurately detected.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an external perspective view showing an embodiment of a mounting structure of an optical fiber grating according to the present invention. The same members as those in the conventional example shown in FIG.

In this mounting structure, a Bragg grating 102 of an optical fiber grating 106 for a strain sensor having a Bragg grating 102 formed on an optical fiber 103 is fixed on a substrate 101 for mounting an object to be measured. Each of them is embedded and molded with the hot melt adhesive 201.

That is, in this mounting structure, a structure having the mounting structure of the optical fiber grating 106 shown in FIG. 3 is put in an aluminum mold (not shown), and a hot melt adhesive (commercially available from Aron Evergrip Co., Ltd.) (Namely, cermelt) 201 was cast, molded, and sealed with an adhesive. The resin temperature was 180 ° C. and the cooling time was 2 minutes.

The fixing hole 105 of the fixing terminal of the substrate 101 of the mounting structure shown in FIG. 1 was attached to the object to be measured with a bolt (not shown), and the relationship between the distortion and the center wavelength was evaluated.
, The center wavelength was changed by 10 nm, and the result was in agreement with the theoretical value.

Incidentally, a general thermoplastic resin has poor fluidity in a mold and damages the adhesively fixed Bragg grating, so that it cannot be embedded.

As described above, a mounting structure of an optical fiber grating for a strain sensor, which is excellent in waterproofness and handleability, was obtained.

FIG. 2 is an external perspective view showing another embodiment of the mounting structure of the optical fiber grating of the present invention.

In this mounting structure, an optical fiber grating 208 for a strain sensor, in which a Bragg grating 206 is formed by irradiating an optical fiber 207 with ultraviolet light, is provided on a base 210 formed on a substrate 210 for mounting an object to be measured. One (two, but not limited, three or more in the drawing) may be located on the tangent of the cylinders 202a and 202b and arranged so as not to cover the circumference. The optical fiber 207 is wound around the cylinders 202a and 202b with an appropriate tension so as not to overlap with each other, and fixed with adhesives 209a and 209b, respectively.

Two cylinders 202a and 202b and a base 2
Numeral 10 is integrally formed of resin, and is covered with the cover 204 together with the optical fiber grating 208.
The cover 204 has fixing holes 205a and 205b formed at positions of the cylindrical fixing holes 203a and 203b, respectively.

After attaching the cover 204 to the base 210, the fixing holes 203a, 203b, 205a, 205b
Was attached to the object to be measured with bolts, and the relationship between the strain and the center wavelength was evaluated. When the strain was 1%, the center wavelength was changed by 10 nm, and a result consistent with the theoretical value was obtained.

As described above, the strain of the object to be measured can be accurately measured by the optical fiber grating, and the simple mounting structure allows the cost to be reduced and the optical fiber grating mounting structure for the strain sensor to be easy to handle. Is obtained.

[0028]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to provide an inexpensive and easy-to-handle optical fiber grating mounting structure.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing one embodiment of a mounting structure of an optical fiber grating of the present invention.

FIG. 2 is an external perspective view showing another embodiment of the mounting structure of the optical fiber grating of the present invention.

FIG. 3 is an external perspective view showing a conventional example of a mounting structure of an optical fiber grating.

[Explanation of symbols]

 101, 210 Substrate (base) for mounting DUT 102, 206 Bragg grating 103, 207 Optical fiber 106, 208 Optical fiber grating 201 Hot melt adhesive 202a, 202b Cylindrical 204 Cover 209a, 209b Adhesive

Claims (3)

[Claims] 1. After fixing the Bragg grating of an optical fiber grating for a strain sensor, in which a Bragg grating is formed by irradiating an ultraviolet ray to an optical fiber, on a substrate for mounting an object to be measured, the substrate is hot melt bonded. An optical fiber grating mounting structure characterized by being embedded and molded with an agent. 2. An optical fiber grating for a strain sensor, wherein a Bragg grating is formed by irradiating an ultraviolet ray to an optical fiber, is located on a tangent line of at least two cylinders formed on a substrate for mounting an object to be measured. An optical fiber grating mounting structure, wherein the optical fibers are arranged so as not to extend around the circumference, and the optical fibers on both sides of the Bragg grating are respectively wound around and fixed to the cylinder. 3. A mounting structure for an optical fiber grating according to claim 2, wherein the center of each of said cylinders is fixed to an object to be measured.