JP2003255151A - Fitting structure for fbg - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the long-term reliability of a physical quantity sensor, etc., which has an FBG (optical fiber Bragg diffraction grating) fitted to a strain generating member by stabilizing the precision and performance. <P>SOLUTION: Optical fibers 12 on both the sides of the FBG 10 are coated with metal 18. The optical fibers 12 on both the sides of the FBG 10 are sheathed with metal pipes 26. The metal coatings 18 are fixed to the metal pipes 26 by soldering 20 respectively. The metal pipes 26 are fixed to metal pedestals 34 by welding 24A respectively. The metal pedestals 34 are fixed to the strain generating member 14 by welding 24B. The FBG 10 is tensed not to slack. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a physical quantity sensor for detecting a physical quantity such as pressure, tension and temperature, a filter, an F used for a Fabry-Perot laser, etc.
The present invention relates to a mounting structure for a BG (optical fiber Bragg diffraction grating).

[0002]

2. Description of the Related Art When light is incident on an optical fiber provided with an FBG in a part of its longitudinal direction from one end side, the FBG reflects only light of a specific wavelength. When elongation strain is applied to the FBG, the wavelength of reflected light shifts to the longer side. Therefore, the pressure can be detected by attaching the FBG to a member that generates strain by pressure and measuring the wavelength shift amount of the reflected light (Japanese Patent Laid-Open No. 2001-83031). Also FBG
Is attached to a member that generates tensile strain due to tension,
The tension can be detected by measuring the wavelength shift amount of the reflected light (JP-A-11-173820). Similarly, FB
The temperature can be detected by attaching G to a member that expands and contracts due to temperature changes and measuring the wavelength shift amount of the reflected light.

When the FBG is used as various sensors as described above, it is necessary to attach the FBG to a member that is distorted by a change in physical quantity so as to expand and contract with the member. Conventionally, the attachment of the FBG to the strain generating member has been performed by fixing the entire length of the FBG to the strain generating member using an adhesive.

Further, in a filter or a laser using an FBG, in order to stabilize the reflection wavelength, it is preferable to fix the FBG to a supporting member having rigidity with a certain tension applied. Also in this case, it is general that the FBG is attached to the rigid support member with an adhesive.

[0005]

Since the strain generating member and the rigid supporting member are generally made of metal, there is no problem in accuracy and long-term reliability. However, the FBG is attached to the strain generating member or the rigid supporting member by an adhesive. When installed, there are the following problems. (1) Since the adhesive strength is likely to vary, it is difficult to stabilize accuracy and performance. (2) Since the adhesive has a larger coefficient of thermal expansion than the optical fiber,
The FBG is susceptible to the expansion and contraction of the adhesive. (3) Since the adhesive tends to creep at high temperatures,
Accuracy and performance may deteriorate over the long term.

An object of the present invention is to provide an FBG mounting structure (mounting structure) that solves the above problems.

[0007]

Means for Solving the Problems An FBG mounting structure according to the present invention is one in which an FBG is mounted on a metal substrate that constitutes a strain generating member or a rigid support member, and the optical fibers are provided on both sides of the FBG or A metal coating is applied to the FBG and the optical fibers on both sides of the FBG, and the metal-coated portions on both sides of the FBG are bonded to the metal substrate directly or through other metal parts by metal joining means so that the FBG does not have slack (preferably Is characterized by being fixed under tension.

The metal joining means is any one of known soldering, brazing, welding and the like. In the present invention, the structure is such that both sides of the FBG are fixed to the metal substrate by metal bonding without using an adhesive, so that the fixing strength is high, the accuracy and performance are stable, and the long-term reliability is improved.

In the FBG mounting structure of the present invention, the FB
It is preferred that G is mounted away from the metal substrate. By doing so, it is possible to improve the sensitivity as a physical quantity sensor.

The FBG mounting structure according to the present invention is such that the FBG is mounted on a metal substrate that constitutes a strain generating member or a rigid supporting member, and the FBG is mounted on the optical fibers on both sides of the FBG or on both sides of the FBG. The optical fiber is metal-coated, and the metal-coated portions on both sides of the FBG are fixed to the metal pedestals by metal joining means, and the metal pedestals are fixed to the metal base by the metal joining means so that the FBG does not have slack ( It is characterized in that it is fixed (preferably under tension).

By using the metal pedestal as described above, the distance for separating the FBG from the metal base can be accurately set. In addition, the sensitivity of the physical quantity sensor can be adjusted by adjusting the height of the metal pedestal. In this case, the metal coating portion and the metal pedestal are preferably joined by soldering, and the metal pedestal and the metal base are preferably joined by welding.

The FBG mounting structure according to the present invention is such that the FBG is mounted on a metal substrate that constitutes a strain generating member or a rigid supporting member, and the FBG is mounted on the optical fibers on both sides of the FBG or on both sides of the FBG. The optical fiber is metal-coated, and the metal-coated portions on both sides of the FBG are fixed to the metal pipes covered with the optical fibers on both sides of the FBG by metal joining means, and these metal tubes are joined to the metal base by metal joining means. By FB
It is characterized in that G is fixed so as not to have slack (preferably under tension).

By using the metal tube as described above, the optical fibers on both sides of the FBG can be more firmly fixed to the metal substrate. Also, the FBG can be mounted separately from the metal substrate. In this case, it is preferable that the metal coating portion and the metal tube are joined by soldering, and the metal tube and the metal substrate are joined by welding.

When the metal pipe is used as described above, the metal pipe can be accurately fixed by forming a groove for positioning the metal pipe in the metal base.

When a metal tube having a polygonal cross section is used as the metal tube, when the metal tube is joined to the metal base,
This is preferable because the position of the metal tube is stable.

When a metal tube is used, a pedestal portion is integrally formed on the metal tube, and the pedestal portion is fixed to the metal base by a metal joining means, so that the FBG is separated from the metal base and the physical quantity sensor is used. It is effective to improve the sensitivity as.

Further, the FBG mounting structure according to the present invention is one in which the FBG is mounted on a metal substrate that constitutes a strain generating member or a rigid supporting member, in the optical fibers on both sides of the FBG, or on the FBG and on both sides thereof. A metal coating is applied to the optical fiber, and the metal coating portions on both sides of the FBG are fixed to the metal pipes covered with the optical fibers on both sides of the FBG by metal joining means. The metal pedestal is fixed to the metal base by a metal joining means so that the FBG does not have slack (preferably in a tensioned state).

With such a structure, the optical fibers on both sides of the FBG can be more firmly fixed to the metal substrate, and the sensitivity as the physical quantity sensor can be improved. In this case, it is preferable that the metal coated portion and the metal tube are joined by soldering, the metal tube and the metal pedestal are joined, and the metal pedestal and the metal base are joined by welding.

When the metal pipe and the metal pedestal are used as described above, it is preferable to form a groove for positioning the metal pipe on the metal pedestal in order to fix the metal pipe at an accurate position.

The metal tube used in the present invention is preferably made of a material whose coefficient of linear expansion is substantially the same as that of the optical fiber (quartz glass). Further, instead of the metal tube, a ceramic tube having a metal layer provided on the surface can be used. The coefficient of linear expansion of ceramics is close to that of optical fibers.

Further, in the present invention, instead of the metal pedestal,
It is also possible to use a ceramic pedestal provided with a metal layer on the surface.

The FBG mounting structure according to the present invention can also be applied to a structure in which the optical fibers on both sides of the FBG are mounted on a metal fixing member that supports a member that causes elongation strain in the FBG. In that case, A metal coating is applied to the optical fibers on both sides of the FBG or to the FBG and the optical fibers on both sides of the FBG, and the metal coating portions on both sides of the FBG are directly or via other metal parts by metal joining means. The structure should be fixed.

[0023]

Embodiments of the present invention will be described below.
A detailed description will be given with reference to the drawings.

First Embodiment FIG. 1A shows an embodiment of the present invention. In the figure, 10 is an FBG formed on a part of the optical fiber 12, and 14 is a metal substrate to which the FBG 10 is attached. The metal substrate 14 is a strain generation member that generates strain due to a change in physical quantity in the case of a physical quantity sensor, and a rigid support member in the case of a filter or a laser. FBG
The optical fiber 12 at 10 and its vicinity is stripped by removing the protective coating 16. A metal coating 18 is applied to the optical fibers 12 on both sides of the FBG 10. This metal coating 18
Is formed, for example, by subjecting the optical fiber 12 to electroless plating of Ni / Au and then gold plating having a thickness of about 1 μm. The portion to which the metal coating 18 is applied is fixed to the metal base 14 by the solder 20 in a state where a slight tension is applied so that the FBG 10 does not sag. As the solder 20, Au / Sn solder or the like can be used. The FBG 10 is preferably mounted separately from the metal substrate 14 as shown.

Although FIG. 1A shows the case where the metal coating 18 is applied to the optical fibers 12 on both sides of the FBG 10, the metal coating 18 is formed as shown in FIG.
And the optical fibers 12 on both sides thereof may be continuously applied. This point is the same in the following embodiments.

Embodiment 2 FIG. 2 shows another embodiment of the present invention. Also in this embodiment, the protective coating 16 is removed from the FBG 10 and the optical fiber 12 in the vicinity thereof, and the metal coating 18 is applied to the optical fibers 12 on both sides of the FBG 10.
The portion coated with the metal coating 18 is placed on the metal pedestal 22 and fixed to the metal pedestal 22 by the solder 20. The metal pedestal 22 is fixed to the metal base 14 by YAG welding or the like. 24 is the weld. Also in this case, the FBG 10 is slightly tensioned so as not to cause slack.

When the metal coating 18 portion is fixed to the metal base 14 via the metal pedestal 22 as described above, the FBG 10
The distance between the metal base 14 and the metal base 14 can be increased. As a result, if the metal substrate 14 is, for example, one that receives pressure from the lower side in the drawing and swells to the upper side, or if it is a bimetal that warps upward due to temperature rise, FB
Since the distortion of G10 is expanded, the sensitivity as a pressure sensor or a temperature sensor can be improved. Also, by adjusting the height of the metal pedestal 22, the sensitivity or dynamic range of the sensor can be adjusted.

[Third Embodiment] In this embodiment, the FB is also used.
The protective coating 16 is removed from the G10 and the optical fibers 12 in the vicinity thereof, and the optical fibers 12 on both sides of the FBG 10 are metal-coated.
18 are given. The difference from the previous embodiment is that the metal tube 26 is packaged so as to extend from the portion where the metal coating 18 is applied to the protective coating 16, the metal coating 18 and the metal tube 26 are fixed by the solder 20, and then the metal tube 26 Is fixed to the metal base 14 by YAG welding or the like. 24 is the weld. Also in this case, the FBG 10 is slightly tensioned so as not to cause slack. As the metal tube 26, it is preferable to use a tube made of Kovar (Fe / Ni / Co alloy) which has substantially the same linear expansion coefficient as that of the optical fiber (quartz glass).

When the metal tube 26 is used, the metal coating 18 portion can be more easily and reliably soldered to the metal tube 26, and the metal tube 26 can be fixed to the metal substrate 14 by welding, so that both sides of the FBG 10 can be fixed. The optical fiber 12 can be more firmly fixed to the metal base 14, and the reliability of the fixed state can be improved. Further, by covering the metal tube 26 so as to extend from the metal coating 18 portion to the protective coating 16, the bare optical fibers 12 on both sides of the FBG 10 can be protected, and handling at the time of welding or the like becomes easy.
The FBG 10 can also be mounted separately from the metal base 14.

When the metal tube 26 is directly welded to the metal substrate 14 as in this embodiment, if a metal tube having a polygonal cross section (quadrangular section, hexagonal section, etc.) is used as the metal tube 26, Since the position of the metal tube 26 on the metal base 14 is stable, the welding operation can be easily performed.

Fourth Embodiment FIG. 4 shows still another embodiment of the present invention. In this embodiment, a pedestal portion 28 is integrally formed with the metal tube 26, and the pedestal portion 28 is fixed to the metal base 14 by welding. By forming the pedestal portion 28, the same effect as that of the second embodiment can be obtained. Since the configuration other than the above is the same as that of the embodiment of FIG. 3, the same parts are designated by the same reference numerals and the description thereof will be omitted.

Embodiment 5 FIG. 5 shows still another embodiment of the present invention. In this embodiment, as in the embodiment of FIG. 3, the metal tube 26 is directly fixed to the metal base 14, but the metal base 14 is integrally provided with the thick portion 30. A groove 32 for positioning the metal tube 26 is formed therebetween. In this way, the metal tube 26 can be accurately positioned on the metal base 14. The configuration other than the above is shown in FIG.
Since it is the same as the embodiment of FIG.

[Embodiment 6] FIG. 6A shows still another embodiment of the present invention. In this embodiment, a metal tube 26 is fixed to the optical fibers 12 on both sides of the FBG 10, and the metal tube 26 is
Is fixed to the metal base 14 via the metal pedestal 34.

The metal tube 26 is fixed to the optical fiber 12 as shown in FIG. 6 (B). That is, the protective coating 16 is removed from the FBG 10 and the optical fibers 12 in the vicinity thereof, and the metal coating 18 is applied to the optical fibers 12 on both sides of the FBG 10. The metal tube 26 is externally installed so as to extend from the portion where the metal coating 18 is applied to the protective coating 16,
It is fixed by solder 20 (similar to the embodiment of FIG. 3).

As shown in FIGS. 6C and 6D, the metal pedestal 34 is integrally formed with a pipe receiving portion 38 having a groove 36 for positioning the metal pipe 26 formed on the upper surface thereof and a leg portion 40. It was done.

The metal pedestal 34 has its legs 40 fixed to the metal base 14 by welding as shown in FIG. 6A (24 A is the welded portion), and the metal tube 26 is positioned by the groove 36. It is fixed to 34 by welding (24B is the welded part). Also in this case, the FBG 10 is slightly tensioned so as not to cause slack. On the outer end side of the metal tube 26, the protective coating 16 of the optical fiber 12 is fixed to the metal pedestal 34 with an adhesive 42. In this way, no external force is applied directly to the bare optical fiber 12,
12 can be protected more reliably.

When the protective coating 16 of the optical fiber 12 is fixed with an adhesive, it may be fixed to the outer end of the metal tube 26. Similar configurations are preferably employed in the embodiments of FIGS. 3, 4 and 5 which utilize the metal tube 26.

Embodiment 7 FIG. 7 shows still another embodiment of the present invention. In this embodiment, the optical fiber 12 having the FBG 10 is attached to a metal fixing member 44 supporting the strain generating member 14 so as to straddle the strain generating member 14.
Strain is generated in the FBG 10 by the strain transmitting member 46 fixed to the strain generating member 14. The strain generating member 14 is pressed from the lower surface to generate strain. Also in this case, as in the above-described embodiment, the metal coating 18 is applied to the optical fibers 12 on both sides of the FBG 10, and the metal coating 18 portions are soldered to the metal tubes 26, respectively.
The metal tube 26 may be fixed to the fixing member 44 by welding.

[Other Embodiments] In the above embodiment, in the case where the metal tube 24 is used, a ceramic tube having a metal layer on its surface can be used instead of the metal tube. Further, in the case of the embodiment using the metal pedestals 22 and 34, it is possible to use a ceramic pedestal having a metal layer on the surface instead of the metal pedestal. The metal layer on the ceramic surface can be formed by a known metallization treatment (metallization).

[0040]

As described above, according to the present invention,
Since the optical fibers on both sides of the FBG are fixed to the metal substrate by the metal joining means, there is little variation in fixing strength, and accuracy and performance can be stabilized. In addition, since metal parts such as a metal tube having a thermal expansion coefficient closer to that of the optical fiber than the adhesive can be used, the influence of temperature change can be reduced. Further, since the metal joining means such as soldering has a smaller creep than the adhesive even at high temperature, stable accuracy and performance can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1A is a front view showing an embodiment of an FBG mounting structure according to the present invention, and FIG. 1B is a sectional view showing another example of how to apply a metal coating in the same embodiment.

FIG. 2 is a front view showing another embodiment of the FBG mounting structure according to the present invention.

FIG. 3 is a partially cutaway front view showing still another embodiment.

FIG. 4 shows still another embodiment, (A) is a partially cutaway front view, and (B) and (C) are an end view and a front view of the metal tube used in (A).

5A and 5B are still another embodiment, FIG. 5A is a front view and FIG. 5B is a plan view.

FIG. 6 shows still another embodiment, (A) is a front view, (B) is a partially cut-away front view of a main part of (A),
(C), (D) is an end view and a front view of the metal pedestal used in (A).

FIG. 7 is a front view showing still another embodiment.

[Explanation of symbols]

10: FBG 12: Optical fiber 14: Metal substrate 16: Protective coating 18: Metal coating 20: Solder 22: Metal pedestal 24: Weld 26: Metal tube 32: groove 34: Metal pedestal 36: Groove

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F076 BA01 BD06 BD07 BD10 BD11                       BE01                 2H038 BA25 CA52                 2H050 AB05X AC82 AC84 AD00

Claims (12)

[Claims] 1. An FBG (optical fiber Bragg diffraction grating)
Is attached to a metal substrate that constitutes a strain generating member or a rigid support member, and the optical fibers on both sides of the FBG or the FBG and the optical fibers on both sides thereof are subjected to metal coating, and metal coating on both sides of the FBG is performed. A part to the metal substrate directly or via another metal part,
An FBG mounting structure characterized in that the FBG is fixed so as not to have slack by means of metal joining means. 2. The FBG mounting structure according to claim 1, wherein the FBG is mounted separately from the metal base. 3. A structure in which an FBG is attached to a metal substrate that constitutes a strain generating member or a rigid supporting member, wherein the optical fibers on both sides of the FBG or the FBG and the optical fibers on both sides thereof are metal-coated, Metal coating portions on both sides of the FBG are fixed to a metal pedestal by metal joining means, and these metal pedestals are fixed to the metal base by the metal joining means so that the FBG does not have slack. Mounting structure. 4. A structure in which an FBG is attached to a metal substrate that constitutes a strain generating member or a rigid supporting member, wherein the optical fibers on both sides of the FBG or the FBG and the optical fibers on both sides thereof are metal-coated, The metal coating portions on both sides of the FBG are fixed to the metal pipes respectively coated on the optical fibers on both sides of the FBG by means of metal joining means, and these metal pipes are prevented from sagging on the metal base by means of the metal joining means. FBG mounting structure characterized by being fixed to. 5. The FBG mounting structure according to claim 4, wherein a groove for positioning the metal tube is formed in the metal base. 6. The FBG mounting structure according to claim 4, wherein a metal tube having a polygonal cross section is used as the metal tube. 7. The FBG mounting structure according to claim 4, wherein a pedestal portion is integrally formed with the metal tube, and the pedestal portion is fixed to the metal base by metal joining means. FBG mounting structure. 8. A structure in which an FBG is attached to a metal substrate that constitutes a strain generating member or a rigid supporting member, wherein the optical fibers on both sides of the FBG or the FBG and the optical fibers on both sides thereof are metal-coated, The metal coating portions on both sides of the FBG are fixed to the metal pipes respectively coated on the optical fibers on both sides of the FBG by metal joining means, these metal pipes are fixed to the metal pedestals, and these metal pedestals are attached to the metal base. , By metal joining means,
An FBG mounting structure characterized in that the FBG is fixed so that there is no slack. 9. The FBG mounting structure according to claim 8, wherein a groove for positioning the metal tube is formed in the metal pedestal. 10. The FBG mounting structure according to claim 4, wherein a ceramic tube having a metal layer on a surface thereof is used instead of the metal tube. Construction. 11. The FBG mounting structure according to claim 3, 8 or 9, wherein a ceramic pedestal having a metal layer on a surface thereof is used instead of the metal pedestal.
BG mounting structure. 12. The optical fiber on both sides of the FBG is connected to the F
A structure for attaching to a metal fixing member that supports a member that causes extensional strain in the BG, in which a metal coating is applied to the optical fibers on both sides of the FBG, or the FBG and the optical fibers on both sides thereof are coated with metal. The coating portion is fixed to the fixing member directly or through another metal part by a metal joining means F
BG mounting structure.