JP2018040778A - FBG temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FBG temperature sensor that can further accurately measure a temperature of a narrow area where detection has been conventionally difficult.SOLUTION: A main body part 3 has a through-hole 31 into which an optical fiber 2 is inserted. Further, the main body part 3 cantilever-supports the optical fiber 2 inserted into the through-hole 31 on one side of an FBG part 21. A heat reception part 4 contacts with a temperature detection object. A thermal conductivity part 5 is arranged at a space with the optical fiber 2 in a state of surrounding a periphery of the FBG part 21. Further, the thermal conductivity part 5 is thermally connected to the heat reception part 4. A coupling part 35 is provided in the main body part 3. The coupling part 35 supports an outer peripheral surface of the heat reception part 4 or an outer peripheral surface of the thermal conductivity part 5, and thereby fixes the heat reception part 4 to the main body part 3. In the foregoing configuration, the coupling part 35 is composed of a material lower in a thermal conductivity than the heat reception part 4 and the thermal conductivity part 5.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an FBG (Fiber Bragg Grating) temperature sensor, and more particularly to an FBG temperature sensor suitable for high temperature measurement.

  In recent years, an optical fiber sensor using an optical fiber formed with FBG (Fiber Bragg Grating) has been used as a temperature sensor. The Bragg wavelength of FBG is determined by the refractive index of the optical fiber and the grating spacing of the diffraction grating. For this reason, the Bragg wavelength also changes due to changes in the refractive index when the temperature changes and thermal expansion / contraction (expansion / contraction) of the optical fiber. By detecting this change in Bragg wavelength, a change in temperature can be detected.

  In order to improve the function as a temperature sensor, various structures have been proposed. For example, Patent Document 1 described later discloses an optical fiber having an FBG portion, a resin coating layer having a high linear expansion coefficient applied on the optical fiber, and a coating of a metal material formed on the resin coating layer. A temperature sensor comprising a layer is disclosed. According to this structure, the sensitivity of the thermal expansion and contraction of the FBG portion can be increased by the action of the coating layer made of a resin having a high linear expansion coefficient, and the heat transfer to the resin coating layer by the action of the coating layer made of a metal material. Can be secured. As a result, it is said that the function as a temperature sensor in a cryogenic environment can be improved.

  Patent Document 2 discloses a temperature sensor including a metal layer having a thermal expansion coefficient larger than that of the optical fiber on the surface corresponding to the temperature measurement point of the optical fiber. According to this structure, the sensitivity of the thermal expansion and contraction of the FBG portion can be increased by the action of the metal layer. As a result, it is said that the function as a temperature sensor in a cryogenic environment can be improved.

  Furthermore, Patent Document 3 discloses that a resin coating material that covers the outer surface of an optical fiber in which an FBG portion is formed is fired at a temperature higher than the application temperature of the FBG temperature sensor, and is not restrained in the metal tube. The temperature sensor inserted in the state in which the clearance gap was formed between the inner peripheral surface and the outer peripheral surface of the sensor cable is disclosed. According to this structure, it is possible to prevent fluctuations in the characteristics of the optical fiber due to the thermal decomposition of the resin that is the coating material in a high-temperature environment due to the action of the fire treatment, and even when the metal tube expands due to the action of the gap, The sensor cable having a lower coefficient of thermal expansion than the tube can be prevented from being pulled and cut. As a result, it is said that the function as a temperature sensor in a high temperature environment can be improved.

  Patent Document 4 describes an optical fiber having an FBG portion at one end or in the vicinity of the one end, and a range in which the end portion of the optical fiber and the FBG portion are provided at intervals from the optical fiber, the optical fiber end portion, and the FBG portion. A temperature sensor is disclosed that includes an open cap that opens and surrounds. In this temperature sensor, the cap is sealed by the optical fiber at the position of the opening located on the side away from the FBG portion. The cap is formed of a material having a low Young's modulus and functions to separate the FBG portion from strain. According to this structure, the distortion of the FBG portion can be separated with respect to temperature detection. As a result, it can be suitably used as a temperature sensor for temperature compensation of a strain sensor having an FBG unit for strain measurement.

JP 2012-021939 A JP 2014-190874 A JP 2009-258007 A Japanese Patent Application Laid-Open No. 11-072353

  As described above, the Bragg wavelength of the FBG portion is determined by the grating interval of the diffraction grating. Therefore, in one optical fiber, diffraction gratings with different grating intervals are formed at different positions and arranged in series, so that multipoint measurement for simultaneously measuring temperatures at a plurality of measurement positions is relatively easy. Can be realized. Therefore, the conventional FBG temperature sensor is structured on the assumption that the side surface of the optical fiber is placed in contact with the temperature detection target as in the configuration disclosed in Patent Document 1 to Patent Document 4 described above. ing.

  However, since the FBG portion is formed in the optical fiber over a range of a length of about several millimeters to several tens of millimeters, in the arrangement method as described above, the portion corresponding to the length of the FBG portion is detected in the temperature detection target. The average value of temperature is measured. That is, in the conventional FBG temperature sensor, it is difficult to accurately measure the temperature in an extremely narrow region, for example, as in a known thermocouple type temperature sensor.

  On the other hand, according to the structure of the FBG temperature sensor disclosed in Patent Document 4, for example, it may be possible to arrange the FBG temperature sensor in a positional relationship in which the optical fiber is perpendicular to the temperature detection target. However, in this case, the cap surrounding the periphery of the FBG portion comes into contact with the temperature detection target. In Patent Document 4, since the cap is made of quartz glass or epoxy resin, it cannot follow a rapid temperature change of a temperature detection target and cannot detect an accurate temperature.

  The present invention has been made in view of such a problem of the prior art, and provides an FBG temperature sensor that can more accurately measure the temperature of a narrow region that has been difficult to detect conventionally. With the goal.

  In order to achieve the above object, the present invention employs the following technical means. First, the present invention is premised on an FBG temperature sensor that detects temperature using an optical fiber in which an FBG (Fiber Bragg Grating) portion is formed. And the FBG temperature sensor which concerns on this invention is provided with a main-body part, a heat receiving part, a heat conductive part, and a coupling | bond part. The main body has a through hole into which the optical fiber is inserted. The main body cantilever supports the optical fiber inserted into the through hole on one side of the FBG portion. A heat receiving part contacts a temperature detection object. The heat conducting unit is disposed at a distance from the optical fiber so as to surround the periphery of the FBG unit. The heat conducting unit is thermally connected to the heat receiving unit. The coupling portion is provided on the main body portion. The coupling portion supports the outer peripheral surface of the heat receiving portion or the outer peripheral surface of the heat conducting portion, thereby fixing the heat receiving portion to the main body portion. In the above configuration, the coupling portion is made of a material having a lower thermal conductivity than the heat receiving portion and the heat conducting portion.

  According to the FBG temperature sensor of the present invention, since the heat (hot or cold) given to the heat receiving part is transmitted to the FBG part via the heat conducting part, the heat receiving part contacts the temperature detection target. The plane can be arranged in a direction intersecting the axial direction of the optical fiber. Therefore, the area of the heat receiving portion can be made smaller than the area of the region defined by the length of the FBG portion in the optical fiber. Moreover, since the heat receiving part and the heat conducting part are thermally separated at the joint part, heat is prevented from being transmitted from the main body part side. Therefore, it is possible to more accurately measure the temperature in a narrow region that has been difficult to detect conventionally.

In this FBG temperature sensor, for example, the heat receiving part is the other side of the FBG part, that is, F
It is possible to adopt a configuration in which the optical fiber is disposed at a distance on the opposite side of the main body portion with the BG portion interposed therebetween.

  Further, for example, the coupling part can be constituted by a concave part that is recessed along the axial direction of the optical fiber. In this case, the structure by which the outer peripheral surface of a heat receiving part or the outer peripheral surface of a heat conductive part is supported by the inner peripheral surface of the said recessed part is employable.

  Furthermore, the heat conducting part can be constituted by a cylindrical member having an open end at one end. In this case, the structure provided in the other end of a cylindrical member can be employ | adopted for a heat receiving part. The heat conduction part comprised with the cylindrical member can employ | adopt the structure which has the outer peripheral surface of circumference | surroundings different in the position close | similar to a heat receiving part, and the position away from the heat receiving part.

  In the above configuration, the coupling portion may employ a configuration in which the heat receiving portion is fixed to the main body portion by press-contacting the outer peripheral surface of the heat conducting portion by shrink fitting, press fitting, or screwing. In addition, the main body portion may be configured to support the optical fiber in a cantilever manner by pressing the outer peripheral surface of the optical fiber inserted into the through hole by shrink fitting.

  According to the present invention, it is possible to more accurately measure the temperature of a narrow region that has been difficult to detect.

The figure which shows an example of the structure of the FBG temperature sensor in one Embodiment of this invention Sectional drawing which shows an example of the structure of the FBG temperature sensor in one Embodiment of this invention The schematic block diagram which shows an example of the temperature detection system which uses the FBG temperature sensor in one Embodiment of this invention Sectional drawing which shows the other example of the structure of the FBG temperature sensor in one Embodiment of this invention. Sectional drawing which shows the other example of the structure of the FBG temperature sensor in one Embodiment of this invention. Sectional drawing which shows the other example of the structure of the FBG temperature sensor in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a diagram showing an example of the structure of the FBG temperature sensor in the present embodiment. Fig.1 (a) is a top view which shows the FBG temperature sensor in this embodiment. FIG. 1B is a side view showing the FBG temperature sensor in the present embodiment. FIG.1 (c) is a bottom view which shows the FBG temperature sensor in this embodiment. Moreover, FIG. 2 is sectional drawing which follows the AA line shown to Fig.1 (a).

  As shown in FIGS. 1A to 1C and 2, the FBG temperature sensor 1 includes an optical fiber 2, a main body portion 3, a heat receiving portion 4, a heat conducting portion 5, and a coupling portion 35. The optical fiber 2 includes an FBG (Fiber Bragg Grating) unit 21. As will be described later, the optical fiber 2 is cantilevered by the main body 3. The FBG portion 21 is formed in the vicinity of an unsupported end portion (hereinafter also referred to as a tip) of the optical fiber 2. The optical fiber 2 has a structure in which a core that propagates light and a clad that surrounds the core and reflects light propagating through the core to the core side are arranged in order from the center. The tip of the optical fiber 2 is subjected to a known terminal treatment so that the reflected light reflected at the tip does not travel backward in the optical fiber 2.

As is known, the FBG portion reflects light having a wavelength defined by the Bragg wavelength. The FBG portion is composed of a plurality of diffraction gratings arranged at a predetermined interval in the core of the optical fiber, and the Bragg wavelength is proportional to the product of the refractive index of the optical fiber and the arrangement interval of the diffraction gratings. Therefore, the wavelength of the light reflected by the FBG portion increases due to an increase in the refractive index due to the temperature rise and an increase in the diffraction grating interval due to the extension of the optical fiber. In addition, the wavelength of light reflected by the FBG portion becomes smaller due to a decrease in refractive index due to a temperature decrease and a reduction in the distance between diffraction gratings due to the contraction of the optical fiber.

  As a processing method for forming the FBG portion in the optical fiber, a method of irradiating the optical fiber with ultraviolet light through a mask is widely used. A plurality of grooves are formed at a fixed period on the surface of the mask facing the optical fiber, and the ultraviolet light that has passed through the mask is transmitted to the optical fiber by interference fringes (ultraviolet light having a period determined by the period of the groove). Strength). In this processing method, it is possible to cause a periodic refractive index change in the core of the optical fiber by using the interference fringes.

  However, when the FBG portion formed by such a processing method is installed in a temperature atmosphere of about several hundred degrees, the refractive index change generated in the core becomes small, and the FBG portion disappears. In this embodiment, the refractive index change is caused by irradiating the core of the optical fiber 2 with a femtosecond laser. Since the femtosecond laser has a high peak output, the FBG portion 21 that does not disappear even at a relatively high temperature can be formed in the optical fiber 2.

  In the drawing, for convenience, the boundary between the core and the clad in the optical fiber 2 is omitted, and the FBG portion 21 is expressed by attaching straight lines to the optical fiber 2 at equal intervals.

  As shown in FIG. 1A to FIG. 1C and FIG. 2, in the present embodiment, the main body 3 that cantilever-supports the optical fiber 2 is constituted by a cylindrical member. The main body 3 is made of a low heat conductive material (heat insulating material). Although it does not specifically limit, the main-body part 3 can be comprised by zirconia ceramics, for example. The thermal conductivity (normal temperature) of the main body 3 is preferably 10 W / (m · K) or less, and more preferably 5 W / (m · K) or less.

  The main body 3 has a through hole 31 along the axial direction. The optical fiber 2 is inserted into the through hole 31. A concave portion that is recessed along the axial direction of the main body 3 (optical fiber 2) is formed at one end of the main body 3. The concave portion functions as a coupling portion 35 as described later. As shown in FIG. 2, the optical fiber 2 is fixed in a state where the FBG portion 21 is disposed in the concave portion. The optical fiber 2 can be fixed to the main body 3 by, for example, shrink fitting. Further, as shown in FIGS. 1B, 1C, and 2, the other end of the main body 3 is fixed with an adhesive 6 that bonds the other end of the main body 3 and the optical fiber 2. You can also. As the adhesive 6, a heat-resistant acrylic adhesive, silicone adhesive, olefin adhesive, polyimide adhesive, or the like can be used. As shown in FIGS. 1B and 2, in this embodiment, the optical fiber 2 on the side connected to the measuring instrument with respect to the adhesive 6 is covered with an outer resin 22 that protects the core and the clad. ing.

  A heat receiving portion 4 that is in contact with the temperature detection target is disposed on the distal end side of the optical fiber 2 at a distance from the optical fiber 2. As shown to Fig.1 (a), the heat receiving part 4 has a circular external shape in planar view. The diameter of the heat receiving part 4 can be set to about 1 mm to 3 mm, for example.

  Further, a heat conducting unit 5 is disposed around the FBG unit 21 with a distance from the optical fiber 2. In the present embodiment, the heat conducting unit 5 is configured by a cylindrical member (here, a columnar member) having an open end at one end, and the heat receiving unit 4 is disposed at the other end of the cylindrical member. . Although not particularly limited, in the present embodiment, the distance between the optical fiber 2 (FBG portion 21) and the inner peripheral surface of the heat conducting portion 5 is about 0.1 mm to 0.3 mm.

The heat receiving unit 4 and the heat conducting unit 5 may be thermally connected, but in the present embodiment, the heat receiving unit 4 is used.
And the heat conducting portion 5 are integrally formed of a high heat conducting material. Although not particularly limited, the heat receiving portion 4 and the heat conducting portion 5 can be made of a metal having high thermal conductivity, such as copper, aluminum nitride ceramics, or the like. The heat conductivity (normal temperature) of the heat receiving unit 4 and the heat conducting unit 5 is preferably 20 W / (m · K) or more, and more preferably 50 W / (m · K) or more. In the present embodiment, as shown in FIG. 2, a configuration is adopted in which the entire FBG portion 21 is accommodated inside the heat conducting portion 5. For example, the FBG portion along the axial direction of the optical fiber 2 is used. When the length of 21 is relatively long, it is possible to adopt a configuration in which a part of the FBG portion 21 is accommodated inside the heat conducting portion 5.

  Further, in the present embodiment, the heat conducting unit 5 has outer peripheral surfaces having different perimeter lengths at positions close to the heat receiving unit 4 and positions away from the heat receiving unit 4. That is, as shown in FIG. 2, the outer diameter of the heat conducting part 5 at a position close to the heat receiving part 4 is larger than the outer diameter of the heat conducting part 5 at a position away from the heat receiving part 4 (hereinafter, A portion having a large outer diameter in the heat conducting portion 5 is also referred to as a large diameter portion 51, and a portion having a small outer diameter is also referred to as a small diameter portion 52).

  The heat conducting part 5 is inserted into the concave part of the main body part 3 constituting the coupling part 35. The heat receiving portion 4 is fixed to the main body 3 by supporting the outer peripheral surface of the heat conducting portion 5 (here, the outer peripheral surface of the large diameter portion 51) by the inner peripheral surface of the concave portion. In this case, the coupling part 35 is particularly preferably configured to fix the outer peripheral surface of the heat conducting part 5 without using an adhesive. For example, the coupling portion 35 can employ a configuration in which the heat receiving portion 4 is fixed to the main body portion 3 by press-fitting the outer peripheral surface of the heat conducting portion 5 by shrink fitting or press fitting. Further, it is possible to adopt a configuration in which a screw thread is formed on the outer peripheral surface of the heat conducting portion 5 and the inner peripheral surface of the coupling portion 35 and the heat receiving portion 4 is fixed to the main body portion 3 by screwing. In the present embodiment, the heat conducting part 5 (heat receiving part 4) and the main body part 3 are in contact with each other only at the connecting part 35. From the viewpoint of further suppressing the movement of heat between the heat conducting unit 5 (heat receiving unit 4) and the main body 3, the contact area between the heat conducting unit 5 (heat receiving unit 4) and the main body 3 is preferably smaller. . In the present embodiment, the contact area between the heat conduction part 5 and the main body part 3 is further reduced by providing the small diameter part 52 on the outer peripheral surface of the heat conduction part 5.

  As described above, the FBG temperature sensor 1 is configured to transmit the heat (hot or cold) given to the heat receiving unit 4 to the FBG unit 21 via the heat conducting unit 5. Thus, the surface with which the heat receiving portion 4 comes into contact can be arranged in a direction crossing the axial direction of the optical fiber 2. Therefore, the area of the heat receiving portion 4 can be made smaller than the area of the region defined by the length of the FBG portion 21 in the optical fiber 2. Further, since the coupling portion 35 is made of a material having a lower thermal conductivity than the heat receiving portion 4 and the heat conducting portion 5, the heat receiving portion 4 and the heat conducting portion 5 are thermally separated from the main body portion 3 in the coupling portion 35. Has been. Therefore, heat is prevented from being transmitted from the main body 3 side. Therefore, it is possible to more accurately measure the temperature in a narrow region that has been difficult to detect conventionally.

  Moreover, since the optical fiber 2 in which the FBG part 21 is formed is configured to be cantilevered on one side of the FBG part 21, for example, distortion caused by thermal expansion and contraction of the main body part 3 acts on the FBG part 21. Nor. That is, the change in the lattice spacing and the change in the refractive index of the FBG unit 21 are caused only by the temperature change around the FBG unit 21, so special correction or the like according to the installation position of the FBG temperature sensor 1 is necessary. And accurate temperature can be detected very easily.

  Furthermore, since the heat given to the heat receiving part 4 is not transmitted to the main body part 3, even when the temperature detection target is a relatively high temperature, the heat given to the heat receiving part 4 is transmitted to the adhesive 6 and the outer resin. It is possible to prevent the 22 from being deteriorated or damaged.

The FBG temperature sensor 1 described above is particularly suitable for high-temperature temperature measurement, such as temperature measurement in an engine cylinder. For example, when measuring the temperature in the cylinder of the engine, the FBG temperature sensor 1 has a through-hole provided at the temperature detection position of the cylinder wall surface of the cylinder block, and the tip of the heat receiving portion 4 is flush with the inner wall surface of the cylinder. It can be installed in the state.

  The change in the reflected wavelength of the FBG temperature sensor 1 is acquired by a measuring instrument connected to the end of the optical fiber 2 as in the conventional case. The measuring device includes a broadband light source including a reflected wavelength in the FBG portion 21 of the FBG temperature sensor 1 and a light receiver that measures the reflected wavelength.

  As shown in FIG. 3, a temperature detection system using a plurality of FBG temperature sensors 1 can also be configured. The temperature detection system 10 includes a measuring instrument 11, an optical splitter 12, and a plurality of FBG temperature sensors 1. The measuring instrument 11 includes the above-described light source and light receiver. The optical splitter 12 is connected to the measuring instrument 11 via the optical fiber 13. The optical splitter 12 is connected to the optical fiber 2 of each FBG temperature sensor 1. The optical splitter 12 has a function of dividing the light incident from the measuring instrument 11 into the optical fiber 2 of each FBG temperature sensor 1 and entering one light incident from the optical fiber 2 of each FBG temperature sensor 1. And having the function of entering the measuring instrument 11 together. In this case, the Bragg wavelength of the FBG section 21 of each FBG sensor 1 is set to a different wavelength. Thereby, the reflection position of reflected light can be easily distinguished based on the wavelength of reflected light.

  Hereinafter, modifications of the FBG temperature sensor will be described. 4 to 6 are diagrams showing other examples of the structure of the FBG temperature sensor in the present embodiment. 4 to 6, the same reference numerals are given to the constituent elements having the same functions and effects as those of the FBG temperature sensor 1.

  In the above-described example, the surface that contacts the temperature detection target of the heat receiving unit 4 and the axial direction of the optical fiber 2 are orthogonal to each other. However, as illustrated in FIG. And the axial direction of the optical fiber 2 may intersect at other angles. In the FBG temperature sensor 7 shown in FIG. 4, the angle formed between the surface of the heat receiving unit 4 that contacts the temperature detection target and the axial direction of the optical fiber 2 is about 45 degrees. According to this structure, since the main-body part 3 can be arrange | positioned diagonally with respect to a temperature detection object, it becomes possible to raise the installation freedom degree of a FBG temperature sensor.

  In the above-described example, the heat receiving portion 4 is fixed to the main body portion 3 by supporting the outer peripheral surface of the heat conducting portion 5 with the inner peripheral surface of the concave portion of the main body portion 3 constituting the coupling portion 35. 5, the heat receiving portion 4 is fixed to the main body portion 3 by supporting the outer peripheral surface of the heat receiving portion 4 by the inner peripheral surface of the concave portion of the main body portion 3 constituting the coupling portion 35 as in the FBG temperature sensor 8 shown in FIG. 5. It is also possible to adopt a configuration to be used.

  Further, as in the FBG temperature sensor 9 shown in FIG. 6, the heat receiving portion 4 may be provided with a through hole 41 communicating with the inside of the heat conducting portion 5. This configuration is suitable, for example, when the temperature detection target is a gas.

  As described above, according to the present invention, it is possible to more accurately measure the temperature in a narrow region that has been difficult to detect.

  The above-described embodiments do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, in the above-described embodiment, the outer shape of the main body 3 is a cylindrical shape as a particularly preferable form, but any shape such as a quadrangular prism shape, a polygonal prism shape, a truncated cone shape, a truncated pyramid shape, etc. can be adopted. Moreover, in the said embodiment, although the circumference of the outer peripheral surface of the heat conductive part 5 became the structure which becomes large at the heat receiving part 4 side, it was set as the structure where the peripheral length of the outer peripheral surface of the heat conductive part 5 becomes small at the heat receiving part 4 side. Also good. It is not essential that the peripheral length of the outer peripheral surface of the heat conducting unit 5 be changed in two steps, and it may be changed in steps in three or more steps, or may be changed continuously. Furthermore, it is also possible to employ a configuration in which the peripheral length of the outer peripheral surface of the heat conducting unit 5 does not change, such as the FBG temperature sensor 8 shown in FIG.

  According to the present invention, a temperature in a narrow region that has been difficult to detect conventionally can be measured more accurately, which is useful as an FBG temperature sensor.

DESCRIPTION OF SYMBOLS 1, 7, 8, 9 FBG temperature sensor 2 Optical fiber 3 Main body part 4 Heat receiving part 5 Thermal conduction part 6 Adhesive 21 FBG part 22 Outer resin 31 Through-hole 35 Coupling part 51 Large diameter part 52 Small diameter part

Claims (7)

An FBG temperature sensor that detects temperature using an optical fiber in which an FBG (Fiber Bragg Grating) portion is formed,
A main body having a through hole into which the optical fiber is inserted, and cantilevering the optical fiber inserted into the through hole on one side of the FBG portion;
A heat receiving portion that contacts the temperature detection target;
A heat conducting portion disposed around the FBG portion and spaced apart from the optical fiber, and thermally connected to the heat receiving portion;
A coupling portion that is provided in the main body portion and supports the outer peripheral surface of the heat receiving portion or the outer peripheral surface of the heat conducting portion, thereby fixing the heat receiving portion to the main body portion;
With
An FBG temperature sensor in which the coupling portion is made of a material having a lower thermal conductivity than the heat receiving portion and the heat conducting portion.   2. The FBG temperature sensor according to claim 1, wherein the heat receiving portion is disposed on the other side of the FBG portion and spaced apart from the optical fiber.   The said coupling | bond part is comprised by the recessed part recessed along the axial direction of the said optical fiber, The outer peripheral surface of the said heat receiving part or the outer peripheral surface of the said heat conduction part is supported by the inner peripheral surface of the said recessed part. Or the FBG temperature sensor of Claim 2.   The FBG according to any one of claims 1 to 3, wherein the heat conducting portion is a cylindrical member having an open end at one end, and the heat receiving portion is provided at the other end of the cylindrical member. Temperature sensor.   5. The FBG temperature sensor according to claim 4, wherein the heat conducting portion has an outer peripheral surface having a different perimeter length at a position close to the heat receiving portion and a position away from the heat receiving portion.   The said coupling | bond part fixes the said heat receiving part to the said main-body part by press-contacting the outer peripheral surface of the said heat-conduction part by shrink fitting, press-fit, or screwing to any one of Claims 1-5. The FBG temperature sensor described.   The said main-body part cantilever-supports the said optical fiber by press-contacting the outer peripheral surface of the optical fiber inserted in the said through-hole by shrink fitting, It is any one of Claims 1-6. FBG temperature sensor.

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