JPH07280902A - Optical-fiber sensor and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an optical-fiber sensor whose refractive index is small and which increases the accuracy of the measurement of a magnetic field without being affected by surroundings by forming a plurality of grooves on the outer circumferential face of a bobbin and inserting elastic holding bodies which bond and hold optical fibers, into the grooves so as to be fixed. CONSTITUTION:A plurality of U-shaped grooves 12 are formed on the outer circumference of a bobbin 11 along the peripheral face. Elastic holding bodies 13 are formed out of a silicone rubber which is inserted into the grooves 12, whose shape is identical to the shape of the grooves and which is provided with a heat-resistant property and a flexible property, and fiber holes 15 into which optical fibers 14 can be inserted, are formed in every central part. Breaks 16 which are passed to every upper edge from the fiber holes 15 are formed. While the optical fibers 14 are being twisted, they are inserted into the fiber holes 15 through the breaks 16 in the holding bodies 13 in the grooves 12, and, in this state, the holding bodies 13 are inserted up to the bottom part of the grooves 12. The holding bodies 13 are arranged at equal intervals on the outer circumference of the bobbin 11. The holes 15 and the breaks 16 are coated with a silicone rubber-based adhesive 17 so as to be thin and uniform, and also every inner-face side corresponding to the grooves 12 is coated with the adhesive. Every interval 18h is set at a size at which a stress due to the difference portion in thermal expansion between the bobbin 11 and the optical fibers 14 is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor for measurement used in a magnetic measuring device using the Faraday effect and a method for fixing the optical fiber.

[0002]

2. Description of the Related Art For example, some magnetic measuring devices using the Faraday effect use optical fibers as sensors. The optical fiber sensor of this magnetic measuring device has a plurality of optical fibers wound in a loop and is arranged so as to surround a current-carrying conductor. Linearly polarized light is made incident from one end of the optical fiber and the emitted light is measured at the other end. The linearly polarized light incident on the optical fiber causes the plane of polarization to rotate in proportion to the magnetic field due to the Faraday effect, and the magnetic field generated from the conductor is measured by calculating the rotation angle.

In this case, since the rotation of the plane of polarization is measured,
The polarization disorder causes a measurement error. The extinction ratio is one measure of the degree of polarization disorder, and is represented by the ratio of circularly polarized light to unpolarized light to linearly polarized light.

In general, an anisotropic medium has two optical axes having different refractive indexes, which is called birefringence. An optically isotropic medium such as glass also becomes anisotropic when stress is applied and birefringence occurs. This birefringence is a main factor that deteriorates the extinction ratio of the catalyst, and thus affects the measurement accuracy of the measuring device.

By the way, as a conventional optical fiber sensor, there is one in which a single mode optical fiber is twisted and processed into a loop shape. With such an optical fiber, it is possible to cancel the birefringence that occurs when the optical fiber is processed into a loop shape.

Therefore, since the factor of measurement error due to birefringence is eliminated, it is widely used in manufacturing an optical fiber sensor to add a twist to form a loop.
FIGS. 8A and 8B show a state where the optical fiber is twisted and processed into a loop shape.

That is, as shown in FIG. 8 (a), the optical fiber 1 is twisted and the connector 2 is attached to both ends of the optical fiber 1 with the adhesive 3
The state of twist is maintained by bonding with. Further, as shown in FIG. 8B, the optical fiber 1 is wound a plurality of times along the outer peripheral surface of the bobbin 4 to form a loop.

[0008]

However, the optical fiber sensor having the above structure has the following problems. That is, although the optical fiber is twisted in order to eliminate the birefringence, it is necessary to fix the optical fiber in order to hold this twist. In this case, if an adhesive is used to fix the optical fiber to the bobbin,
Since shrinkage occurs when the adhesive cures, stress is generated at the joint boundary surface, which tends to increase birefringence. Further, even after fixing the optical fiber, there is a risk of causing stress such as tension in the optical fiber fixing portion due to thermal expansion due to temperature change.

On the other hand, when the optical fiber sensor is installed in a gas insulated switchgear (GIS), there is also a problem that the optical fiber (quartz) is weak due to decomposition products (hydrogen fluoride etc.) of SF6 gas used for insulation.

The present invention has been made in order to solve the above problems, and its purpose is to have a small refractive index and to improve the measurement accuracy of a magnetic field without being affected by the environment. A certain optical fiber sensor and a method for manufacturing the same are provided.

[0011]

The present invention achieves the above object by the following means. The invention corresponding to claim 1 applies a twist to a non-magnetic or insulating bobbin arranged so as to be located around the outer periphery of a current-carrying conductor, and winds a plurality of optical fibers in a loop shape from one end side of the optical fiber. An optical fiber sensor in which linear polarized light is incident and the emitted light is measured at the other end, and the magnetic field generated from the conductor is measured by obtaining the rotation angle of the polarization plane with respect to linear polarized light, and the outer peripheral surface of the bobbin. A plurality of grooves are provided in the groove, and an elastic holder for adhesively holding the optical fiber is inserted and fixed in the groove.

According to a second aspect of the present invention, the elastic holder has substantially the same shape as the groove provided on the bobbin, and a fiber hole through which an optical fiber can be inserted and held in the central portion of the elastic holder is provided. A slit is provided in the fiber hole so that the optical fiber can be inserted and inserted from the outer surface side.

According to a third aspect of the present invention, the elastic holder is substantially the same as the groove formed in the bobbin, and a fiber hole through which an optical fiber can be inserted and held is provided in the central portion of the elastic holder. The elastic holder is divided into two parts so that the hole is divided into two parts in the axial direction, and the divided surface is bonded when the optical fiber is bonded.

According to a fourth aspect of the invention, the upper portion of the groove provided on the outer peripheral surface of the bobbin is sealed with a corrosion resistant lid. In the invention corresponding to claim 5, the elastic holder is made of silicone rubber or silicone foam.

According to a sixth aspect of the present invention, a non-magnetic or insulating bobbin arranged so as to be located around the outer periphery of the current-carrying conductor is twisted to wind a plurality of optical fibers in a loop shape. In a method for manufacturing an optical fiber sensor, which is configured to measure a magnetic field generated from the conductor by obtaining linearly polarized light from one end side and measuring the emitted light at the other end side to obtain a rotation angle of a polarization plane with respect to the linearly polarized light. When the optical fiber is twisted and wound around the bobbin a plurality of times to form a loop, the optical fiber is inserted into the groove provided on the outer peripheral surface of the bobbin and temporarily held, and then the groove is formed. An optical fiber sensor is manufactured by inserting an elastic holder into the entire inside. In the invention corresponding to claim 7, a suction device is used to temporarily hold the optical fibers, and the optical fibers that have been wound into the groove on the outer peripheral surface of the bobbin are sequentially held.

[0016]

In the optical fiber sensor according to the inventions corresponding to claims 1 to 5, the elastic holder is partially bonded to the groove provided on the outer peripheral surface of the bobbin so as not to apply stress to the optical fiber. By doing so, the amount of adhesive in the lengthwise direction of the optical fiber is minimized, and the eccentricity of the hole diameter of the optical fiber (or deviation of the amount of adhesive) is suppressed, so that the optical fiber is hardened when the adhesive is cured. It is possible to prevent excessive stress from being generated.

For tension or the like caused by thermal expansion, the distance between the fiber hole of the elastic holder and the groove bottom can be specified to absorb the thermal expansion difference with a soft elasticity to eliminate the stress.

Further, the elastic material of the optical fiber can be prevented from being excessively stressed by selectively adhering or not adhering to the elastic material according to the use condition. The tension or the like generated by thermal expansion or the like is absorbed by the elastic material filled in the gap with the groove with a soft elasticity, so that the stress can be eliminated.

In the optical fiber sensor according to the invention according to claim 4, since the upper surface of the groove is sealed with a durable lid, even when it is mounted in the GIS, the optical fiber and silicon rubber are not corroded. Can be prevented.

Further, in the optical fiber sensor according to the invention according to claim 5, since the soft foam is filled in the groove, the holding force can be gently shared over the entire length of the groove.

In the method of manufacturing an optical fiber sensor according to the invention according to claim 6 or 7, the optical fiber wound around the groove provided on the outer peripheral surface of the bobbin is not firmly adhered to the bobbin, but a predetermined interval is maintained. Since the initial holding force can be suppressed to a minimum by holding the existing temporary holding, it is possible to avoid the occurrence of a large stress in the optical fiber. Therefore, a practical optical fiber sensor having a small birefringence can be obtained.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. 1A to 1C show a first embodiment of an optical fiber sensor according to the present invention. FIG. 1A is a view of an upper half of a bobbin viewed from one side, and FIG. FIG. 4A is a partially enlarged view of a) cut parallel to the central axis of the bobbin radius, and FIG.

In FIGS. 1A and 1B, 11 is a cylindrical bobbin, and a plurality of U-shaped grooves 12 are formed on the outer periphery of the bobbin 11 along the peripheral surface. Further, 13 is an elastic holder having the same shape as the groove shape to be inserted into the groove 12, and this elastic holder 13 is made of, for example, silicon rubber having heat resistance and flexibility, and as shown in FIG. A fiber hole 15 into which the optical fiber 14 can be inserted in the central portion
Is provided, and a cut 16 is provided through the fiber hole 15 to the upper end surface.

Next, a case where the optical fiber 14 is processed into a loop shape and fixed to the bobbin 11 will be described. Figure 1
In FIG. 1B, when the optical fiber 14 is held in the groove 12 while twisting, as shown in FIG.
First, the optical fiber 14 is passed through the cut 16 and the fiber hole 1
5 and insert the elastic holder 13 to the bottom of the groove 12 in this state. As shown in FIG. 1A, the elastic holders 13 are arranged on the circumference of the bobbin 11 at equal intervals.

In this case, the silicon rubber adhesive 17 is thinly and uniformly applied to the fiber hole 15 and the cut 16, and the adhesive 17 is also applied to the corresponding inner surface side of the groove 12. Further, a space 18 is provided between the fiber hole 15 provided at the center of the U-shaped elastic holder 13 and the bottom of the groove 12.
I have h. The space 18h is set to a dimension obtained by adding a thermal expansion difference between the bobbin 11 and the optical fiber 14 with a margin length that does not generate stress due to compression.

In this way, the use of the silicone rubber adhesive 17 alone suppresses the generation of stress on the adhesive surface due to the elasticity. Further, when the elastic holder 13 into which the optical fiber 14 is inserted is inserted into the groove 12, the fiber hole 15
Since the diameter of is close to the diameter of the optical fiber 14,
The surplus of the adhesive agent 17 used for is extruded to the side surface of the elastic holding body 13.

Therefore, the fiber hole 15 and the optical fiber 14 are prevented from being eccentric in the radial direction (or the deviation of the amount of adhesive). Further, since the thickness 18d of the elastic holding body 13 is suppressed to the holding force and the minimum necessary for handling (within 5 mm), it is possible to realize a fixing structure in which stress is not easily generated in the optical fiber 14 when the adhesive is cured together with eccentricity. .

Further, since the elastic holder 13 is made of silicon rubber having heat resistance and flexibility, and a space 18h is provided between the bottom of the groove 12 and the fiber hole 15, the optical fiber is expanded due to thermal expansion or the like. The stress generated in 14 can be absorbed elastically.

According to the above embodiment, since the groove 12 having a U-shaped cross section is formed on the outer circumference of the bobbin 11, the optical fiber 1
In the bobbin winding operation of No. 4, the elastic holding body 13 is easy to insert and difficult to remove. Further, since the bottom of the groove 12 is a semicircle, even if a filling material or an adhesive is put on the entire surface of the groove later, the diameter of the groove bottom and the diameter of the optical fiber 14 are symmetric, so that the stress distribution is close to a uniform direction. Becomes

In the above embodiment, the case where the U-shaped elastic holder 13 is used has been described. However, as shown in FIG. 2, this U-shaped elastic holder 13 is provided at the center of the fiber hole 15. The upper elastic holding portion 13a and the lower elastic holding portion 13b may be cut in the groove width direction and vertically divided into two. In this case, when the bobbin 11 is inserted into the U-shaped groove 12, the adhesive 17 is applied and bonded to the dividing surfaces of the upper and lower elastic holding portions 13a and 13b, the fiber hole and the groove wall surface.

With this structure, the elastic holder 13
The optical fiber 14 can be easily inserted into the fiber hole 15. 3 (a) and 3 (b) are perspective views showing a main part of the second embodiment of the present invention.

In the second embodiment, as shown in FIG. 3 (a), a plurality of V-shaped grooves 19 are provided on the outer circumference of the bobbin 11, and these grooves 19 have a fiber hole 20 at the center. In addition, the elastic holder 21 having the same shape as the groove is inserted.

Next, the case where the optical fiber 14 is processed into a loop shape to fix the optical fiber will be described. Figure 3
As shown in (b), the optical fiber 14 is previously provided in the fiber hole.
The elastic holding body inserted through is fixed at a constant interval to the optical fiber by a method that does not apply stress to the optical fiber, and the optical fiber is twisted by the elastic holding body 21 and inserted into the V-shaped groove formed in the bobbin 11 to be bonded and held. To go.

Also in the second embodiment having such a structure, the same operation and effect as those of the first embodiment can be obtained, and a V-shaped groove 19 is formed on the side surface of the disk other than the bobbin 11, for example. It is suitable for the type provided.

FIGS. 4A and 4B show a third embodiment of the present invention. FIG. 4A is a view of the upper half of the bobbin as seen from one side, and FIG. FIG. 4B is a partially enlarged view of FIG. 4B cut parallel to the central axis of the bobbin radius.

In the third embodiment, as shown in FIGS. 4A and 4B, a plurality of V-shaped grooves 19 are formed on the outer circumference of the bobbin 11.
And a plurality of elastic body pieces 22 having the same shape as this portion are arranged on the circumference of the bobbin 11 at equal intervals and bonded to the bottom of the groove 19. In this example, RTV silicon having heat resistance and flexibility is used as the elastic piece 22.

Next, the twisted optical fiber 14 is placed on the elastic piece 22 in the groove 19 while a constant tension is applied by a pulling mechanism (not shown). In this case, since the optical fiber 14 pushes down the elastic piece 22 a little, the twist of the optical fiber 14 is held by mutual contact surface friction accompanied by a repulsive force.

In this method, since the optical fiber 14 is held without being adhered, there is no fear of generating stress at the joint interface between the optical fiber 14 and the adhesive unlike the conventional example. Figure 5
FIG. 3 is a schematic view of this configuration as seen from the side surface of the bobbin 11. In FIG. 5, the bobbin 11 is shown as the bottom of the groove 19, and while rotating the bobbin 11 in the direction of the arrow,
By winding the twisted optical fiber 14,
The temporary holding can be completed immediately.

Next, as the second-step regular holding, FIG.
As shown in (b), the optical fiber 14 that has been temporarily held
On the other hand, the entire surface of the groove 19 is filled with the elastic material 23, and the upper portion of the groove 19 is covered with a durable lid 24 such as hydrogen fluoride to be hermetically sealed. In this case, the elastic material 23 is made of silicon rubber and is not adhered to the optical fiber 14.

Since this silicone rubber has elasticity, even if it is changed to an adhesive, the elasticity has the effect of alleviating the stress at the time of expansion and contraction, and excessive stress is suppressed by devising the shape of the groove 19 and the like. It is expected. For the structure in which this is confirmed, it is possible to use a silicone adhesive for the elastic material 23.

As described above, in the third embodiment, the first holding force can be minimized by holding the twisted optical fiber 14 on the bobbin 11 not by firmly adhering it but by holding it temporarily at several places. Therefore, it is possible to prevent a large stress from being generated in the optical fiber.

Further, since the elastic material 23 made of silicon rubber is filled in the entire surface of the groove 19 in the optical fiber 14 which has been temporarily held, the elasticity can soften the stress at the time of expansion and contraction. it can.

Furthermore, since the groove 19 is sealed with a durable lid 24 such as hydrogen fluoride, the optical fiber 14 and the silicone rubber are not corroded even when used in the GIS.

In the above embodiment, the elastic material 23 may be made of silicone foam in order to support the optical fiber 14 more softly. In this case, the groove 19 is sealed with a lid 24 made of a material having durability against hydrogen fluoride such as aluminum. In this case, the silicone foam is a liquid one, and at a room temperature, it foams 3-4 times within a few minutes to cure. Since this foam is highly elastic, it easily follows the movements of other materials, and has the heat resistance, cold resistance, and heat resistance common to silicone rubber.
It has excellent weather resistance.

If such a silicone foam is used as the filler 23, potting of the silicone foam becomes easy. Further, the optical fiber and silicon rubber, which are weak against hydrogen fluoride, can be protected even when the optical fiber sensor is stored in the GIS.

FIG. 6 shows another example of holding the optical fiber 14 as the fourth embodiment of the present invention.
The optical fiber 14 is point-bonded to the groove portion 19 with the silicone adhesive used as. In this case, it is necessary to carefully select the bonding method by taking care so that the stress at the joint is not applied to the optical fiber 14.

In such temporary holding, since the holding force cannot be obtained unless the adhesive is hardened, it is difficult to wind continuously while twisting, but the twisted optical fiber 14 is not firmly adhered to the bobbin 11. The same effect as described above can be obtained by holding it at several positions.

FIG. 7 shows a structural example of a jig-like and mechanical temporary holding method as a fifth embodiment of the present invention. This temporary holding method is a method in which the suction nozzle 25 is applied to the optical fiber 14 to evacuate as shown in FIG. 7, and an introduction hole is provided in the groove portion of the bobbin so that the pipe 26 can be passed from the inside of the bobbin. Adsorption nozzle 25 made of silicone rubber
When the optical fiber 14 is attached to the suction nozzle 25 and the optical fiber 14 is evacuated so that the switching valve 27 operates each time the optical fiber comes, the optical fiber 14 can be continuously wound. It can be held and can be immediately transferred to the regular holding means.

[0049]

As described above, according to the present invention, there is provided a practical optical fiber sensor having a small refractive index and capable of enhancing the measurement accuracy of a magnetic field without being affected by the environment, and a manufacturing method thereof. Can be provided.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a first embodiment of an optical fiber sensor according to the present invention.

FIG. 2 is a perspective view showing a modified example of the elastic holding body in the first embodiment.

FIG. 3 is a structural explanatory view showing a main part of a second embodiment of the present invention.

FIG. 4 is a structural explanatory view showing a third embodiment of the present invention.

FIG. 5 is a schematic view of the configuration of the embodiment as seen from the side of the bobbin.

FIG. 6 is a schematic configuration diagram for explaining temporary holding of an optical fiber according to a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram for explaining temporary holding of an optical fiber according to a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram for explaining an optical fiber fixing method of a conventional optical fiber sensor.

[Explanation of symbols]

11 ... Bobbin, 12 ... U-shaped groove, 13 ... Elastic holder, 14 ... Optical fiber, 15 ... Fiber hole, 16
...... Discontinuity, 17 ...... Adhesive, 18h ...... Gap between fiber hole and groove bottom, 18d ...... Thickness of elastic holder, 1
9 ... V-shaped groove, 20 ... Fiber hole, 21 ... Elastic holder, 22 ... Elastic piece, 23 ... Elastic material, 24 ...
Lid, 25 ... adsorption nozzle, 26 ... piping, 27 ... switching valve.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location G02F 1/09 505 (72) Inventor Kiyoto Terai No. 2 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Inside the formula company Toshiba Hamakawasaki Plant (72) Inventor Masao Takahashi 2-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Stock Company Inside the Toshiba Hamakawasaki Plant (72) Inventor Keiko Niwa 2--1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa No. Stock Company Toshiba Hamakawasaki Factory

Claims (7)

[Claims] 1. A non-magnetic or insulating bobbin arranged so as to be positioned around the outer periphery of a current-carrying conductor is twisted to wind a plurality of optical fibers in a loop, and linearly polarized light is incident from one end of the optical fiber. Then, the emitted light is measured at the other end side, and in the optical fiber sensor configured to determine the rotation angle of the polarization plane with respect to the linearly polarized light and measure the magnetic field generated from the conductor, a plurality of grooves are formed on the outer peripheral surface of the bobbin. The optical fiber sensor is characterized in that an elastic holding body for adhesively holding the optical fiber is inserted and fixed in the groove. 2. The elastic holder has substantially the same shape as the groove formed on the bobbin, and a fiber hole through which an optical fiber can be inserted and held in the central portion of the elastic holder, and the optical fiber is inserted in the fiber hole. The optical fiber sensor according to claim 1, wherein a notch is provided to allow insertion and insertion from the outer surface side. 3. The elastic holder is substantially the same as the groove formed in the bobbin, and a fiber hole through which an optical fiber can be inserted and held is provided in the center of the elastic holder, and the fiber hole is arranged in the axial direction. 2. The optical fiber sensor according to claim 1, wherein the elastic holder is divided into two parts, and the divided surface is adhered when the optical fiber is adhered. 4. The optical fiber sensor according to claim 1, wherein an upper portion of the groove provided on the outer peripheral surface of the bobbin is sealed with a corrosion-resistant lid. 5. The optical fiber sensor according to claim 1, wherein the elastic holder is made of silicone rubber or silicone foam. 6. A non-magnetic or insulative bobbin arranged around the outer periphery of a current-carrying conductor is twisted to wind a plurality of optical fibers in a loop, and linearly polarized light is incident from one end side of the optical fibers. Then, the emitted light is measured at the other end side, and in the method for manufacturing the optical fiber sensor, in which the rotation angle of the polarization plane with respect to the linearly polarized light is obtained and the magnetic field generated from the conductor is measured, the optical fiber is twisted. In a state where the bobbin is wound a plurality of times to form a loop, the optical fiber is inserted into the groove provided on the outer peripheral surface of the bobbin and temporarily held, and then an elastic holder is entirely provided in the groove. A method for manufacturing an optical fiber sensor characterized by being inserted. 7. A suction device is used for temporarily holding the optical fiber,
7. The method for manufacturing an optical fiber sensor according to claim 6, wherein the optical fibers which have been wound into the groove on the outer peripheral surface of the bobbin are sequentially held.