JP7026542B2 - Optical fiber strain sensor and its manufacturing method - Google Patents

Description

The present invention relates to a strain sensor using an optical fiber and a method for manufacturing the same.

The optical fiber distortion sensor can measure the amount of frequency shift having a distortion dependence of the backward scattered light (Brillouin scattered light) of the pulsed light incident on the optical fiber in a time-divided manner. Using this measurement result, the magnitude of strain and the location where it occurs can be known as a distribution. This method is called a BOTDR (Brillouin Optical Time Domain Reflectometry) method. The application of this measurement system has made it possible to measure strain as a distribution at a relatively low cost. Its measuring ability is a distance resolution of 1 m and a strain resolution of 0.1 mm / 1 m, and the allowable dynamic range (total transmission loss due to optical fiber) is about 2 dB at the minimum value depending on the measurement conditions.

When an optical fiber is fixed to the entire line as a strain sensor, JP-A-2001-228380 (Patent Document 1), JP-A-2002-5759 (Patent Document 2), and JP-A-2002-107269 In the optical fiber strain sensor in which the optical fiber is fixed to the outer skin tube in the entire strain sensor line such as (Patent Document 3), the sensor is locally stretched when the object to be measured is distorted in a minute section such as a crack. Therefore, the elongation limit of the optical fiber is easily reached, and the wire may be broken.

In the optical fiber strain sensor shown in JP-A-2001-281777 (Patent Document 4), the outer skin tube is fixed to the optical fiber core wire by flat caulking of the outer skin tube, but the outer skin tube cross section is elliptical due to the flat caulking. Since there is only partial contact with the optical fiber, if the strain becomes large, slippage may occur between the outer skin tube and the optical fiber core wire. If the caulking is strengthened to stop slipping between the outer skin tube and the optical fiber core wire, the optical fiber may break. Further, since the gap is present in the caulking, it is difficult to adjust the position of the optical fiber core wire, which is one of the factors for lowering the manufacturing yield of the optical fiber strain sensor having a stable low transmission loss.

Furthermore, in an optical fiber strain sensor with a flat caulking structure, the caulking may extend beyond the outer diameter of the metal tube, so the caulking may be pushed open when the optical fiber strain sensor is laid, and the applied tension may be released. ..

In addition, since the strain sensor in which the optical fiber is intermittently fixed to the outer skin tube undergoes deformation on average at the length of the fixed section, the strain sensor is disconnected due to a crack compared to the strain sensor fixed to the entire line. It is difficult to get rid of, but it tends to be less sensitive to a small range of deformation.

According to Japanese Patent Application Laid-Open No. 2005-274200 (Japanese Patent Laid-Open No. 5), the applicant applies light in which an optical fiber core wire is fixed to the inner surface of the outer skin tube by all-around diaphragm caulking at a predetermined interval over the entire length of the outer skin tube. A fiber optic strain sensor was presented. According to this strain sensor, the inner surface of the outer skin tube is in close contact with the entire outer surface of the optical fiber by caulking all around, and there is no need to adjust the position of the optical fiber core wire. Can be improved. Further, in the optical fiber strain sensor having a caulking structure all around, the caulking does not protrude outside the outer diameter of the metal tube, and the sensor can be easily installed.

Japanese Unexamined Patent Publication No. 2001-228380 JP-A-2002-5759 Japanese Unexamined Patent Publication No. 2002-107269 Japanese Unexamined Patent Publication No. 2001-281777 Japanese Unexamined Patent Publication No. 2005-274200

However, even with the optical fiber strain sensor described in Japanese Patent Application Laid-Open No. 2005-274200 (Japanese Patent Laid-Open No. 5), the optical fiber is constrained by the metal tube for measuring the strain of the expansion / contraction ratio exceeding 2% in the optical axis direction of the optical fiber. It is difficult to apply due to lack of power. That is, if a distortion of the expansion / contraction ratio exceeding 2% occurs, slippage occurs between the metal tube and the optical fiber core wire at the crimped portion, which makes measurement difficult.

The present invention improves the accuracy of the strain sensor by preventing slipping between the outer skin tube and the optical fiber core wire in the optical fiber strain sensor, and stabilizes and strengthens the integration between the optical fiber core wire and the coated outer skin tube. The purpose is to improve and stabilize the quality, and to further expand the measurable range of the strain amount by the optical fiber strain sensor.

(1) The optical fiber strain sensor of the present invention is opened in the outer skin tube and the tube wall of the outer skin tube at a predetermined interval over the entire length in a direction orthogonal to the axis of the outer skin tube . An optical fiber inside the outer skin tube, fixed to the inner surface of the outer skin tube by all-around squeezing caulking while holding a predetermined tension, and locally bonded to the outer skin tube, and the above. It is provided with an adhesive that is locally injected into the outer skin tube through the injection port and fixes the optical fiber to the outer skin tube.

(2) Further, the optical fiber strain sensor of the present invention in an aspect of expanding the strain measurement limit is a spiral optical fiber strain sensor in which the optical fiber strain sensor of the above (1) is formed into a spiral shape.

(3) A process of opening an injection port that leads from the outside of the tube to the inside of the tube at a predetermined interval over the entire length of the metal tube that is the outer skin tube of the optical fiber strain sensor.
The step of inserting an optical fiber into a metal tube having an injection port opened,
A step of locally injecting an adhesive for fixing the optical fiber to the metal tube through the injection port inside the metal tube into which the optical fiber is inserted, and
A step of fixing the inner surface of the metal tube to the optical fiber by all-around drawing caulking in the vicinity of the injected adhesive of the metal tube into which the adhesive has been injected.
A method of manufacturing an optical fiber strain sensor, including.

(4) A process of opening an injection port that leads from the outside of the tube to the inside of the tube at a predetermined interval over the entire length of the metal tube that is the outer skin tube of the optical fiber strain sensor.
The step of inserting an optical fiber into a metal tube having an injection port opened,
A step of squeezing and caulking the vicinity of the injection port of the metal tube into which the optical fiber is inserted to hold a predetermined tension and fixing the optical fiber in the tube to the inner surface of the metal tube.
A step of locally injecting an adhesive for fixing an optical fiber to a metal tube through the injection port inside the metal tube.
A method of manufacturing an optical fiber strain sensor, including.

(5) In the step of opening the injection port, the injection port is opened on both sides of the position where the all-around drawing caulking is performed in the direction in which the central axis of the metal tube extends, respectively, in the above (3) or (4). The method for manufacturing an optical fiber strain sensor according to the description.

(6) In the step of opening the injection port, each injection port is opened in the metal tube wall facing the central axis in the vicinity of the all-around throttle caulking in the direction in which the central axis of the metal tube extends. 3) The method for manufacturing an optical fiber strain sensor according to (4).

(7) In the step of opening the injection port, a plurality of injection ports directed to the central axis of the metal tube are opened at each location at predetermined intervals in the direction in which the central axis of the metal tube extends, and the adhesive is locally injected. The method for manufacturing an optical fiber strain sensor according to (3) or (4) above, wherein the adhesive is simultaneously injected into the metal tube through the plurality of injection ports.

(8) In the step of opening the injection port, the injection port is a metal tube wall facing each other with the central axis on both sides of the position where the all-around drawing caulking is performed in the direction in which the central axis of the metal tube extends. In the step of opening each injection port and locally injecting the adhesive, the central axes of the metal pipes on both sides of the all-around squeezing caulking are simultaneously inserted into the metal pipe through the injection ports opened in the opposite metal pipe walls. The method for manufacturing an optical fiber strain sensor according to (3) or (4) above, wherein an adhesive is injected into the fiber.

(9) A method for manufacturing an optical fiber strain sensor, which comprises a step of fixing the optical fiber strain sensor manufactured in each of the steps (3) or (4) above to a spiral shape.

In addition to being strongly restrained by full-circle squeezing caulking, the optical fiber is further fixed to the outer skin tube with an adhesive, so even when laid linearly as an optical fiber strain sensor, distortion near the measurement limit in the longitudinal direction is accurate. It can be measured well.

Further, by making the optical fiber strain sensor spiral, the strain measurement range can be greatly expanded.

INDUSTRIAL APPLICABILITY The present invention can be used for detecting elongation of tension-imparted objects such as wires, landslides, surface surveys such as rock collapse, prediction of collapse of buildings, etc. by raising the limit value of strain detection and because of its high accuracy. .. For landslides, it is possible to measure just before sliding, and for tension-imparted objects, just before it runs out. Other objects and features of the present invention will be clarified by the description of the following examples with reference to the drawings.

It is a vertical sectional view of the optical fiber strain sensor of one Embodiment of this invention. It is a graph which shows the result of the optical strain with respect to the mechanical displacement by comparing the Example 1 and the Comparative Example of this invention. The optical fiber strain sensor formed into a spiral shape of the present invention is shown, (a) is a front view, and (b) is a right side view. It is a block diagram which shows the whole outline of the manufacturing equipment which manufactures the optical fiber strain sensor of this invention. It is a block diagram which shows the whole outline of another manufacturing equipment which manufactures the optical fiber strain sensor of this invention.

FIG. 1 shows an enlarged vertical sectional view of a linear optical fiber strain sensor according to an embodiment of the present invention. As the outer skin tube, the metal tube 2 is used in consideration of environmental resistance and temperature characteristics. As the material of the metal tube 2 used as the outer skin tube, stainless steel, nickel-based alloy, copper, titanium, aluminum and the like are used. As a proper use, use a stainless steel outer skin tube for normal atmospheric use, for example, in an atmosphere that requires chlorine resistance, hydrogen sulfide resistance, or electrolytic corrosion resistance, such as when embedding in soil near a volcano. A nickel-based alloy tube is used. Titanium pipes for long-term use in environments exposed to seawater, such as submarine cables and revetment blocks, and aluminum or copper pipes if it is necessary to match the material of the object to be measured. It may also be used for.

Inside the metal tube 2, there is an optical fiber core wire F in which a bare optical fiber composed of a core 5 and a clad 4 is covered with a resin coating 3. The optical fiber core wire F is fixed to the metal tube 2 by a full-circle throttle caulking 1 with a predetermined tension. The all-around drawing caulking 1 is manufactured with an arbitrary interval A, and a gap 6 exists in the metal tube 2 other than the all-around drawing caulking 1.

As shown in FIG. 1, by making the caulking 1 into a round all-around throttle caulking, it is possible to fix the optical fiber core wire F so as not to give a slipping phenomenon in which the applied tension escapes, and the caulking 1 is a metal tube 2. Since it no longer protrudes outside the outer diameter of the caulking 1, it is possible to eliminate the possibility that the caulking 1 will open during laying or the like. The depth at which the metal tube 2 of the all-around drawing caulking portion bites into the resin coating 3 of the optical fiber core wire F by all-around drawing caulking stops the occurrence of slippage between the two, and the caulking force does not affect the optical fiber. Considering this, 0.15 mm to 0.25 mm is preferable. The depth of this bite varies depending on the material and physical property value of the resin coating 3, but if it is 0.2 mm (radial direction) in the case of a normal resin coating, the slip between the metal tube 2 and the optical fiber core wire F should be stopped. Can be done.

The principle of the linear optical fiber strain sensor of the present invention detects the amount of strain from the position of the peak of the backscattered light of the incident pulsed light at each distance of the Brillouin scattered light. The strain amount is calculated assuming that the strain is 493 [MHz /%]. Further, since the value of the optical strain output from the measuring instrument is (movement of the object to be measured) = (movement of the sensor), it is output one-to-one with the mechanical strain.

Two sets of adhesive injection ports 2h are opened on both sides of the all-around drawing caulking 1 in the direction in which the axis of the metal tube 2 extends, at intervals of a short distance φ with the caulking 1 as an intermediate point. Each set 2h has a pair of holes on a through axis that penetrates the metal tube 2 in the transverse direction and is orthogonal to the center of the metal tube 2, that is, between the central axes of the metal tubes on both sides of the all-around drawing caulking 1. It is an injection port opened in the wall of a metal tube facing each other, and is opened at once by laser processing or a drill. In the example shown in FIG. 1, the adhesive 7 is a thermosetting resin and is distributed in two sets at short distance φ intervals with the caulking 1 as an intermediate point, from a total of four injection ports 2h into the metal tube 2 at the same time. After being injected, it is cured and surrounds the optical fiber core wire F in the circumferential direction, and is distributed near both sides of the caulking 1.

Table 1 shows the results of the tensile test of the linear optical fiber strain sensor according to the first embodiment of the present invention and the comparative example. In Table 1, the data described as "adhesive + all-around drawing caulking (%)" shows the optical displacement (%) when the mechanical displacement (%) is given to the tensile tester in Example 1, and " The data described as "all-around diaphragm caulking (%)" indicates the optical displacement (%) of the comparative example when the mechanical displacement (%) is applied as in the first embodiment. FIG. 2 graphically shows the data distribution in Table 1.

The specifications of the optical fiber core wire F and the metal tube 2 of Example 1 and Comparative Example are the same. The optical fiber core wire F has an outer diameter of 0.125 mm for the core 5, and the resin coating 3 has an outer diameter (diameter) of 0.9 mm. The metal tube 2 is a stainless steel SUS304 with an outer diameter (diameter) of 2.0 mm and an inner diameter (diameter) of 1.6 mm. : 0.7mm, applied tension: 210N, initial strain: 0.1%.

The adhesive injection port 2h of Example 1 has a diameter of 0.4 to 0.7 mm and is drilled at positions on both sides of the caulking 1. Of course, it may be opened by laser processing. The adhesive 7 is obtained by injecting a thermosetting adhesive 353ND, which is a mixture of two liquids, with a syringe. Thermosetting Adhesive 353ND is a known two-component thermosetting adhesive sold by Rikei Corporation and used for fixing optical fibers and ferrules. In addition to this, the adhesive 7 includes an epoxy resin adhesive (main agent: epoxy resin, curing agent: modified polyamine, modified polyamide, other: curing accelerator, filler), epoxy modified silicone resin adhesive (main component:). Modified silicone resin / amine-based, curing agent: epoxy resin, others: filler), silylated urethane resin-based adhesive (main component: silylated urethane resin, others: filler, plasticizer, silane coupling agent), also Can be used.

Next, the spiral optical fiber strain sensor according to the second embodiment of the present invention will be described with reference to FIG. In the spiral optical fiber strain sensor shown in FIG. 3, the optical fiber core wire F is fixed to the metal tube 2 as shown in FIG. 1 by the all-around drawing caulking 1 having a predetermined tension and the adhesive 7. The fiber strain sensor is formed into a spiral shape having a diameter D and a pitch d. The spiral diameter D of the spiral optical fiber strain sensor of Example 2 is 50 mm, the spiral pitch of the metal tube 2 is 40 mm, and the number of spiral turns is 30.

If the diameter D of the spiral is increased and the pitch d is decreased, the measurement limit can be increased, but the accuracy is lowered accordingly. On the contrary, if the diameter D of the spiral is made small and the pitch d is made large, the measurement limit becomes smaller, but the accuracy of the measurement result can be improved. Further, if the diameter D of the spiral is made too small, a loss due to bending will occur in the optical fiber itself, so it is desirable to make it large. Considering usability, the diameter D of the spiral is preferably about 30 mm to 80 mm.

Using Example 2, a strain measurement test of elongation in the vertical direction (spiral traveling direction) with a mechanical displacement of 0.1 to 40% was carried out. As a result, the mechanical displacement was shown to be a value almost consistent with the theoretical value up to about 25%. In the spiral optical fiber strain sensor of the second embodiment, the measurement limit in the longitudinal direction is the actual strain because the displacement in the longitudinal direction applied to the optical fiber core wire F can be reduced by making the strain sensor spiral. The measurement limit can be expanded by up to 4 orders of magnitude with respect to the linear optical fiber strain sensor (FIG. 1). That is, the linear shape to which the applied tension higher than that of the linear strain sensor is applied in consideration of the decrease in the applied tension due to the optical fiber core wire F in the metal tube 2 which is the outer skin tube escaping to the inside of the spiral diameter D. The optical fiber strain sensor is formed into a spiral shape. By changing the diameter D and pitch d of the spiral, it is possible to receive a deformation of 5 to 1000% in actual strain until the optical strain is extended by about 2.7%.

The conversion between the actual strain% and the optical strain% is performed by the calculation using the correction formulas (1) and (2) shown below. Assuming that the total length of the strain sensor: L, the number of turns of the spiral: n, the pitch of the spiral: d, and the radius of the spiral: D / 2, the relationship between each variable is
L = n · {(Dπ) 2 + d2} 1/2 ... (1)
It is represented by. The total length of the spiral strain sensor is represented by d × n, and assuming that D is a constant, n is a constant, so dn = {L2- (Dπn) 2} 1/2 ... (2)
It becomes a function of the total length L of the spiral sensor.

The total length d'n of the spiral strain sensor when the actual strain is applied is obtained by adding the difference value ε of the optical strain% to the value where the total length L of the reference strain sensor is 1, and setting L'= (1 + ε) L ( 2) Substitute in equation to obtain.

Next, the manufacturing process of the optical fiber strain sensor of the present invention will be described with reference to FIG. The metal pipe 2 molded into the pipe body by the pipe making equipment 60 is linearly sent to the drilling device 8. A plurality of drills are arranged along the metal pipe transport line in the drilling device 8, and one or several drills are used for actual drilling. Each drill is supported by a three-dimensional moving table, and the drill specified for drilling is aligned with the metal pipe 2 on the transport line and penetrates in the transverse direction (vertical direction) orthogonal to the axis of the metal pipe 2. Two adhesive injection ports 2h, each of which is opened in a hole to be formed, that is, a metal tube wall facing each other, are opened, and then a pair of adhesive injection ports are similarly advanced at a position where the metal tube 2 advances by φ on the transport line. 2h is opened, and then a pair of adhesive injection ports 2h are similarly opened at positions where the metal tube 2 advances by A−φ on the transport line, and such drilling is repeated.

The metal tube 2 having the adhesive injection port 2h drawn out by the drilling device 8 is slack-removed and tension-adjusted by a dancer roll (capstan 9 and a pretensioning roll 10), and is wound around a winding drum 12 by a winding device 11. The drum 12 around which the metal tube 2 having the adhesive injection port 2h opened is conveyed to the vibration filling device 15 and mounted on the vibration filling table.

The vibration filling device 15 is an optical fiber wound around a feeding drum 14 around a perforated metal tube 2 of a take-up drum mounted on a vibration filling table by a vibration insertion method disclosed in Japanese Patent Application Laid-Open No. 62-44010. The core line F is extended and inserted. That is, the optical fiber core wire F is vibrated and inserted into the metal tube 2 while applying vibration to the metal tube 2. The drum in which the vibration filling device 15 winds up the metal tube 2 into which the optical fiber core wire F is inserted, that is, the optical fiber G containing the metal tube is conveyed to an adhesive injection facility, where the optical fiber G containing the metal tube is unwound from the drum. It is straightened by the straightening roll 22 and sent to the adhesive injection device 16, from which it is taken up by the dancer roll (capstan) 17 and the pretension addition roll 18 and passed through the constant temperature device 19 to the all-around caulking device 29. Be sent in.

In the adhesive injection device 16, a plurality of sets of adhesive injection syringes are arranged along the metal tube transport line, and one or several pairs of syringes are used for actual adhesive injection. The pair of syringes is supported by a three-dimensional moving table in a downward and upward adhesive injection posture from above and below the optical fiber G with a metal tube on the transfer line, and the pair designated for adhesive injection is Aligned with the adhesive injection port 2h of the metal tube 2 on the transfer line, the adhesive 7 is injected into the metal tube 2 through the injection port 2h, and then the note at the position where the metal tube 2 advances by φ on the transfer line. The adhesive 7 is injected into the metal tube 2 through the inlet 2h, and then the adhesive 7 is injected into the metal tube 2 through the injection port 2h at a position where the metal tube 2 advances by A−φ on the transport line. Repeated injection of adhesive. The optical fiber G into which the adhesive is injected is taken up by the dancer roll (capstan) 17 and the pretension addition roll 18 and enters the thermostatic device 19, and is caulked all around from the thermostat 19 about 1 hour after the adhesive is injected. It leads to the device 29. During this period, the optical fiber G is moving at a constant speed, but it takes a long time to move in the constant temperature device 19. The time delay of about 1 hour is the time to wait for the adhesive 7 injected into the metal tube 2 to cure, but it is shorter than the time until it is completely cured. It is a time having flexibility (fluidity) that does not hinder the axial alignment of the optical fiber F and the metal tube 2 by applying a predetermined tension in the caulking step and caulking all around the circumference.

In the all-around caulking device 29, the extra length of the optical fiber F is adjusted to minus 0.1% by the method disclosed in Japanese Patent Application Laid-Open No. 63-187209, and then the metal tube 2 is provided at a predetermined interval A. The optical fiber F is fixed to the inner wall of the metal tube 2 by the all-around throttle caulking 1, and a tension that causes a predetermined strain is applied to the optical fiber F. After that, the tension is released via the dancer roll 27 and the pretension addition roll 26 to obtain the linear optical fiber strain sensor shown in FIG. The steps up to this point are the manufacturing steps of the linear optical fiber sensor of the first embodiment shown in FIG. In the embodiment in which the linear optical fiber sensor (FIG. 1) is shipped as a product, the optical fiber G via the pretension adding roll 26 and the dancer roll 27 is wound around the winding drum after the all-around caulking is completed.

As shown in FIG. 4, the spiral optical fiber strain sensor of the second embodiment passes through the dancer roll 27 and the pretension adding roll 26, passes through the resin coating device 23, and sequentially passes through the spiral forming device 49, the heating device 38, and the heating device 38. It is wound by the take-up drum 45 via the cooling device 43. In this process, when manufacturing a linear optical fiber strain sensor, the spiral forming device 49 is removed, and if the coating is unnecessary, the resin coating device 23, the heating device 38, and the cooling device 43 are also removed. This manufacturing process is connected to the main control device 47 by a control cable 48 connected to the drive device of each process. Reference numeral 21 in FIG. 4 is a metal tube optical fiber feeding device, and 46 is an optical fiber strain sensor winding device.

Next, a manufacturing example will be described together with the operating status of the manufacturing process. The optical fiber G containing a metal tube in which a quartz-based single-mode optical fiber having a normal resin coating is inserted in the metal tube is rewound from the drum 20, and the straightening roll 22 corrects the bending habit of the optical fiber G containing the metal tube. The resin is sent into the adhesive injection device 16 in a shape, and the transfer of the optical fiber G is intermittently stopped there, and the adhesive is injected into the optical fiber G through the injection port 2h, and the temporary stop of the movement is the stop of the subsequent process. The dancer roll 17 controls the control so as not to be affected by such factors. Then, it is caulked by the caulking device 29 via the constant temperature device 19 via the dancer roll 17 and the pretension addition roll 18. The movement of the metal tube optical fiber G is intermittently stopped even when the all-around diaphragm caulking is applied. The dancer roll 27 controls the control so that the temporary stop of movement is not affected by the stop of the subsequent process or the like.

At the time of applying full-circle drawing caulking, the pretensioning roll 26 is adjusted in order to apply tension between each drawing caulking to the optical fiber in advance, and tension is applied to the metal tube to an appropriate set value to enter the metal tube. The metal tube of the optical fiber G is extended. Next, a resin coating is applied to the resin coating device 23, and the shape is adjusted by the molding roll 24. After that, it is formed into a spiral structure by a spiral forming device 49, annealed by a heating device 38 to remove the internal stress of the coating resin, and cooled by a cooling device 43 to manufacture a spiral optical fiber strain sensor and take up. It is wound up on the drum 45. It is also possible to cut it to a predetermined length without winding it on the drum 45, or drop it on a rotating drum and stack it. Each device of the manufacturing equipment shown in FIG. 4 is divided into blocks according to its function, and adopts a modular system in which each block can be freely and easily rearranged.

FIG. 5 shows an overall outline of another manufacturing facility for manufacturing the optical fiber strain sensor of the present invention. In this manufacturing facility, the optical fiber core wire F is fixed to the metal tube 2 by all-around drawing caulking, and then the adhesive is injected into the injection port 2h of the metal tube 2. The optical fiber G is unwound from the drum 20 from which the optical fiber G is wound up with the injection port 2h opened and the optical fiber F is inserted in the vibration filling device 15, and the optical fiber G is straightened by the straightening roll 22 and crimped all around. It is sent to 29. In the all-around caulking device 29, the extra length of the optical fiber F is adjusted to minus 0.1% by the method disclosed in Japanese Patent Application Laid-Open No. 63-187209, and then the metal tube 2 is provided at a predetermined interval A. The optical fiber F is fixed to the inner wall of the metal tube 2 by the all-around throttle caulking 1, and a tension that causes a predetermined strain is applied to the optical fiber F. After the all-around throttle caulking 1, the tension is released via the dancer roll 27 and the pretension adding roll 26. After that, the adhesive is injected into the metal tube 2 by the adhesive injection device 16, passes through the constant temperature device 19 via the dancer roll 17 and the pretension addition roll 18, and the linear optical fiber strain sensor shown in FIG. 1 is used. To get. The steps up to this point are the manufacturing steps of the linear optical fiber sensor of the first embodiment shown in FIG. In the embodiment in which the linear optical fiber sensor (FIG. 1) is shipped as a product, the optical fiber G that has passed through the thermostat 19 is wound around a winding drum.

As shown in FIG. 5, the spiral optical fiber strain sensor of the second embodiment passes through the dancer roll 17 and the pretension adding roll 18, the resin coating device 23, and then the spiral forming device 49, the heating device 38, and so on. It is wound by the take-up drum 45 via the cooling device 43. In this process, when manufacturing a linear optical fiber strain sensor, the spiral forming device 49 is removed, and if the coating is unnecessary, the resin coating device 23, the heating device 38, and the cooling device 43 are also removed. This manufacturing process is connected to the main control device 47 by a control cable 48 connected to the drive device of each process.

L: Caulking interval δ: Caulking length.
F: Optical fiber core wire G: Optical fiber containing a metal tube H: Optical fiber strain sensor d: Spiral pitch D: Spiral diameter 1: All-around drawing caulking 2: Metal tube 2h which is an outer skin tube: Adhesive injection port 3: Resin Coating 4: Clad 5: Core 6: Void 7: Adhesive 9: Dancer roll (Capstan)
10: Pretension addition roll 11: Metal tube winding device 12: Winding drum 13: Optical fiber feeding device 14: Optical fiber feeding drum 17: Dancer roll (capstan)
18: Pretension adding roll 20: Metal tube optical fiber feeding drum 21: Metal tube optical fiber feeding device 22: Straightening roll 23: Resin coating device 24: Molding roll 26: Pretension adding roll 27: Dancer roll (capstan) )
28: Guide roll 45: Optical fiber strain sensor winding drum 46: Optical fiber strain sensor winding device 47: Main control device 48: Control cable

Claims (9)

The outer skin tube, an injection port opened in the tube wall of the outer skin tube at a predetermined interval over the entire length in a direction orthogonal to the axis of the outer skin tube , and the inside of the outer skin tube. An optical fiber that is fixed to the inner surface of the outer skin tube by squeezing all around the injection port while holding a predetermined tension and locally bonded to the outer skin tube, and the optical fiber that is locally injected into the outer skin tube through the injection port. An optical fiber strain sensor comprising an adhesive for fixing an optical fiber to the outer skin tube. A spiral optical fiber strain sensor in which the optical fiber strain sensor according to claim 1 is formed into a spiral shape. A process of opening an injection port that leads from the outside of the tube to the inside of the tube at a predetermined interval over the entire length of the metal tube that is the outer skin tube of the optical fiber strain sensor.
The step of inserting an optical fiber into a metal tube having an injection port opened,
A step of locally injecting an adhesive for fixing the optical fiber to the metal tube through the injection port inside the metal tube into which the optical fiber is inserted, and
A step of fixing the inner surface of the metal tube to the optical fiber by all-around drawing caulking in the vicinity of the injected adhesive of the metal tube into which the adhesive has been injected.
A method of manufacturing an optical fiber strain sensor, including. A process of opening an injection port that leads from the outside of the tube to the inside of the tube at a predetermined interval over the entire length of the metal tube that is the outer skin tube of the optical fiber strain sensor.
The step of inserting an optical fiber into a metal tube having an injection port opened,
A step of squeezing and caulking the vicinity of the injection port of the metal tube into which the optical fiber is inserted to hold a predetermined tension and fixing the optical fiber in the tube to the inner surface of the metal tube.
A step of locally injecting an adhesive for fixing an optical fiber to a metal tube through the injection port inside the metal tube.
A method of manufacturing an optical fiber strain sensor, including. The optical fiber strain sensor according to claim 3 or 4, wherein in the step of opening the injection port, the injection port is opened on both sides of the position where the all-around throttle caulking is performed in the direction in which the central axis of the metal tube extends. Manufacturing method. 3. The method for manufacturing an optical fiber strain sensor according to the above. In the step of opening the injection port, in the step of drilling holes at predetermined intervals in the direction in which the central axis of the metal tube extends, a plurality of injection ports pointing to the central axis of the metal tube are opened at each location, and the adhesive is locally injected. The method for manufacturing an optical fiber strain sensor according to claim 3 or 4, wherein the adhesive is simultaneously injected into the metal tube through the plurality of injection ports. In the step of opening the injection port, the injection port is injected into the metal tube wall facing each other with the central axis in between on both sides of the position where the all-around drawing caulking is performed in the direction in which the central axis of the metal tube extends. In the step of opening the inlet and locally injecting the adhesive, the adhesive is simultaneously introduced into the metal pipe through the injection ports opened in the metal pipe walls facing each other between the central axes of the metal pipes on both sides of the all-around squeezing caulking. The method for manufacturing an optical fiber strain sensor according to claim 3 or 4. The method for manufacturing an optical fiber strain sensor according to claim 3 or 4, which comprises a step of fixing the optical fiber strain sensor manufactured in each step according to claim 3 or 4 to a spiral shape.

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