阅读说明：本技术 一种光纤光栅测温光缆 (Fiber grating temperature measurement optical cable ) 是由 姜劭栋 张发祥 王英英 王昌 倪家升 刘小会 于 2021-07-05 设计创作，主要内容包括：本申请提供的光纤光栅测温光缆,包括：保护套管,以及内置于保护套管的多个测温单元；每一个测温单元均包括主干光纤、波分复用器、连接光纤以及光纤光栅；波分复用器包括公共端、反射端以及透射端；光纤光栅包括固定端以及自由端,固定端以及自由端形成光纤光栅的整体；连接光纤的一端与固定端连接,另一端与反射端连接；其中,第n个测温单元的主干光纤的一端连接第n-1个测温单元的透射端,另一端连接第n个测温单元的公共端；以使多个测温单元依次串接形成测温线路。本申请提供的技术方案,光纤光栅处于单端自由状态,且光纤光栅可单独进行标定,受应力作用影响小,温度测量结果更加准确。(The application provides a fiber grating temperature measurement optical cable includes: the temperature measuring device comprises a protective sleeve and a plurality of temperature measuring units arranged in the protective sleeve; each temperature measuring unit comprises a trunk optical fiber, a wavelength division multiplexer, a connecting optical fiber and an optical fiber grating; the wavelength division multiplexer comprises a public end, a reflection end and a transmission end; the fiber grating comprises a fixed end and a free end, and the fixed end and the free end form the whole body of the fiber grating; one end of the connecting optical fiber is connected with the fixed end, and the other end of the connecting optical fiber is connected with the reflecting end; one end of a main optical fiber of the nth temperature measuring unit is connected with the transmission end of the (n-1) th temperature measuring unit, and the other end of the main optical fiber of the nth temperature measuring unit is connected with the common end of the nth temperature measuring unit; so that the plurality of temperature measuring units are sequentially connected in series to form a temperature measuring circuit. According to the technical scheme, the fiber grating is in a single-end free state, the fiber grating can be calibrated independently, the stress effect influence is small, and the temperature measurement result is more accurate.)

1. A fiber grating temperature measurement optical cable is characterized by comprising: the temperature measuring device comprises a protective sleeve (1) and a plurality of temperature measuring units (2) arranged in the protective sleeve (1);

each temperature measuring unit (2) comprises a trunk optical fiber (21), a wavelength division multiplexer (22), a connecting optical fiber (23) and a fiber grating (24);

the wavelength division multiplexer (22) comprises a common end (221), a reflective end (222) and a transmissive end (223);

the fiber grating (24) comprises a fixed end (241) and a free end (242), the fixed end (241) and the free end (242) forming an integral body of the fiber grating (24);

one end of the connecting optical fiber (23) is connected with the fixed end (241), and the other end of the connecting optical fiber is connected with the reflecting end (222);

one end of a main optical fiber (21) of the nth temperature measuring unit (2) is connected with a transmission end (223) of the (n-1) th temperature measuring unit (2), and the other end of the main optical fiber is connected with a common end (221) of the nth temperature measuring unit (2); so that the temperature measuring units (2) are sequentially connected in series to form a temperature measuring circuit.

2. The fiber grating thermometry optical cable according to claim 1, wherein the wavelength of the fiber grating (24) of the nth thermometry unit (2) is within the spectral range of the reflective end (222) of the nth thermometry unit (2).

3. The fiber grating thermometric optical cable according to claim 1 or 2, wherein at least one of the thermometric units (2) further comprises a grating protection tube (25), the fiber grating (24) is embedded in the grating protection tube (25), and the free end (232) is in a free state in the grating protection tube (25).

4. The fiber grating thermometric optical cable according to claim 3, wherein the length of the grating protection tube (25) is greater than the length of the fiber grating (24).

5. The fiber bragg grating thermometry optical cable according to claim 1, further comprising a tensile wire (3), wherein the tensile wire (3) is arranged to extend inside the protective sleeve (1) along the axial direction of the protective sleeve (1); the trunk optical fiber (21) and the wavelength division multiplexer (22) are fixedly connected with the tensile wire (3).

6. The fiber bragg grating temperature measuring optical cable according to claim 5, wherein the tensile wire (3) is a Kevlar wire.

7. The fiber bragg grating thermometric optical cable according to claim 1, wherein the protective sleeve (1) is a stainless steel tube; the grating protection tube (25) is a stainless steel capillary tube.

8. The fiber grating thermometric optical cable according to claim 1, wherein the n fiber gratings (24) differ in wavelength.

Technical Field

The application relates to the technical field of fiber bragg grating temperature sensing, in particular to a high-precision fiber bragg grating temperature measurement optical cable.

Background

The fiber grating temperature measuring optical cable achieves the purpose of measuring the ambient temperature by utilizing the modulation effect of the temperature on the wavelength of the fiber grating. Compared with the traditional electrical temperature sensor, the fiber grating temperature measurement optical cable has the advantages of high sensitivity, quick response time, electromagnetic interference resistance, intrinsic safety, easiness in networking, realization of distributed measurement and the like. At present, the main technical schemes of optical fiber distributed temperature measurement include two, one is to use an optical fiber grating array to manufacture a temperature measurement optical cable, and the other is to use the raman scattering effect of the optical fiber and use a common optical fiber to perform distributed temperature measurement (DTS). Compared with DTS, the fiber bragg grating has high temperature measurement sensitivity and quick response, and has good application prospect in the fields of ocean investigation, earthquake prediction, meteorological analysis and the like.

At present, most of fiber grating temperature measuring optical cables adopt a cabling scheme that the interior is provided with a fiber grating array and the exterior is provided with a protective steel pipe. The fiber bragg grating temperature measuring optical cable is high in precision when measuring temperature variation. However, in the situation where the absolute temperature value needs to be measured, the measurement accuracy often cannot meet the requirement. The main reasons for analysis are two:

(1) the fiber grating wavelength is affected by strain in addition to temperature. In the process of laying the fiber grating temperature measurement optical cable in site construction, the internal grating array is easy to deform under the action of external force, so that inaccurate temperature measurement is caused.

(2) When the temperature measuring optical cable measures the absolute temperature value, the temperature measuring optical cable needs to be calibrated in advance. The general temperature calibration equipment is a constant temperature oil groove, but the volume of the groove body is limited, and the optical cable cannot be placed in the groove body. The temperature measuring optical cable is usually coiled up and placed into a high-low temperature circulating box for calibration. High low temperature circulation case temperature stability and degree of consistency are relatively poor, can make the temperature measurement optical cable mark the precision low, and when the optical cable dish was put in addition, inside grating cluster also can receive external force about, causes the temperature measurement inaccurate.

Therefore, the main problems of the prior art are that the stress problem of the grating array and the calibration problem of the fiber grating temperature measurement optical cable cannot be solved. If the fiber grating temperature measurement optical cable with the stress isolation structure can be invented, and the optical cable has the operability of temperature calibration, the optical cable has important application value.

Disclosure of Invention

The application provides a fiber grating temperature measurement optical cable to solve the inaccurate problem of temperature measurement.

The application provides a fiber grating temperature measurement optical cable, include: the temperature measuring device comprises a protective sleeve and a plurality of temperature measuring units arranged in the protective sleeve;

each temperature measuring unit comprises a trunk optical fiber, a wavelength division multiplexer, a connecting optical fiber and an optical fiber grating;

the wavelength division multiplexer comprises a public end, a reflection end and a transmission end;

the fiber grating comprises a fixed end and a free end, and the fixed end and the free end form the whole body of the fiber grating;

one end of the connecting optical fiber is connected with the fixed end, and the other end of the connecting optical fiber is connected with the reflecting end;

one end of a trunk optical fiber of the nth temperature measuring unit is connected with the transmission end of the (n-1) th temperature measuring unit, and the other end of the trunk optical fiber of the nth temperature measuring unit is connected with the common end of the nth temperature measuring unit; so that the temperature measuring units are sequentially connected in series to form a temperature measuring circuit.

Therefore, the fiber bragg grating temperature measuring optical cable can measure the ambient temperature, is less affected by stress and has accurate measuring result.

Optionally, in a possible implementation manner, the wavelength of the fiber grating of the nth temperature measurement unit is within a spectral range of the reflection end of the nth temperature measurement unit.

The working performance of the fiber bragg grating and the wavelength division multiplexer is ensured, and the condition of performance failure is avoided.

Optionally, in a possible implementation manner, at least one of the temperature measuring units further includes a grating protection tube, the fiber grating is disposed in the grating protection tube, and the free end is in a free state in the grating protection tube.

The grating protection tube can provide protection for the fiber grating in the grating protection tube.

Optionally, in a possible implementation manner, the length of the grating protection tube is greater than the length of the fiber grating.

Optionally, a possible implementation manner is that the protective sleeve further comprises a tensile wire, wherein the tensile wire extends in the protective sleeve along the axial direction of the protective sleeve; the trunk optical fiber and the wavelength division multiplexer are fixedly connected with the tensile wire.

The tensile property of the fiber grating temperature measurement optical cable can be improved by the tensile wire.

Optionally, in a possible implementation manner, the tensile wire is a kevlar wire.

Optionally, in a possible implementation manner, the protective sleeve is a stainless steel tube; the grating protection tube is a stainless steel capillary tube.

Alternatively, a possible implementation manner is that the n fiber gratings have different wavelengths.

In a second aspect, the present application provides a method for assembling a fiber grating temperature measurement optical cable, including:

connecting the fiber bragg grating with a connecting optical fiber, and arranging the fiber bragg grating in a grating protection tube;

placing the fiber bragg grating, the connecting optical fiber and the grating protection tube into a constant-temperature oil groove to calibrate the fiber bragg grating;

after calibration is finished, connecting one end of the connecting optical fiber, which is far away from the optical fiber grating, with a reflection end of a wavelength division multiplexer;

connecting the trunk optical fiber with the common end of the wavelength division multiplexer to form a temperature measuring unit;

one end of a main optical fiber of the nth temperature measuring unit is connected with the transmission end of the (n-1) th temperature measuring unit, and the other end of the main optical fiber of the nth temperature measuring unit is connected with the common end of the nth temperature measuring unit; so that the temperature measuring units are sequentially connected in series to form a temperature measuring circuit.

Connecting the trunk optical fiber and the wavelength division multiplexer with a tensile wire;

the protective sleeve is sleeved to form the fiber bragg grating temperature measuring optical cable.

According to the technical scheme, the fiber grating temperature measurement optical cable provided by the application comprises: the temperature measuring device comprises a protective sleeve and a plurality of temperature measuring units arranged in the protective sleeve; each temperature measuring unit comprises a trunk optical fiber, a wavelength division multiplexer, a connecting optical fiber and an optical fiber grating; the wavelength division multiplexer comprises a public end, a reflection end and a transmission end; the fiber grating comprises a fixed end and a free end, and the fixed end and the free end form the whole body of the fiber grating; one end of the connecting optical fiber is connected with the fixed end, and the other end of the connecting optical fiber is connected with the reflecting end; one end of a main optical fiber of the nth temperature measuring unit is connected with the transmission end of the (n-1) th temperature measuring unit, and the other end of the main optical fiber of the nth temperature measuring unit is connected with the common end of the nth temperature measuring unit; so that the plurality of temperature measuring units are sequentially connected in series to form a temperature measuring circuit. According to the technical scheme, the fiber grating is in a single-end free state, the fiber grating can be calibrated independently, the stress effect influence is small, and the temperature measurement result is more accurate.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an optical fiber grating temperature measurement optical cable according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of a wavelength division multiplexer according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a fiber grating according to an embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of another fiber grating temperature measurement optical cable provided in the embodiment of the present application.

1-protecting the sleeve; 2-a temperature measuring unit; 21-a trunk fiber; 22-wavelength division multiplexer; 221-common end; 222-a reflective end; 223-transmission end; 23-connecting an optical fiber; 24-fiber grating; 241-fixed end; 242-free end; 25-a protective sleeve; 3-tensile line.

Detailed Description

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following examples do not represent all embodiments consistent with the present application. But merely as exemplifications of systems and methods consistent with certain aspects of the application, as recited in the claims.

To facilitate understanding of technical solutions of the embodiments of the present application, before describing specific embodiments of the present application, some technical terms in the technical field to which the embodiments of the present application belong are briefly explained. Wherein:

optical fiber (Optical fiber), which is a fiber made of glass or plastic, is a light-conducting tool.

A fiber grating (FBG) is a diffraction grating formed by periodically modulating the refractive index of the fiber core in the axial direction by a certain method, and is a passive filter device. The grating fiber has the advantages of small volume, low welding loss, compatibility with the fiber, embedding of intelligent materials and the like, and the grating wavelength is sensitive to the change of external environments such as temperature, strain, refractive index, concentration and the like, so the grating fiber is widely applied to the fields of manufacturing fiber lasers, fiber communication and sensing.

A thermostatic bath: a tank body with constant temperature is provided. Because the temperature ranges of the constant temperature liquid are different, the constant temperature liquid is divided into a low temperature constant temperature tank (generally minus 80 ℃ to 100 ℃) and a super constant temperature tank (generally room temperature to 550 ℃). Since the liquid medium above 100 ℃ cannot be used with water but oil, it is also commonly referred to as a constant temperature oil bath. The constant temperature oil groove can provide a place for calibrating temperature.

The temperature has a modulation effect on the wavelength of the fiber bragg grating, the wavelength of the fiber bragg grating can be moved, and the measured environment temperature can be obtained by obtaining the change of the wavelength of the fiber bragg grating.

The wavelength of the fiber grating is sensitive to stress in addition to temperature. When the environment where the fiber grating is located is subjected to stress change, the fiber grating is subjected to stress, and further deforms, so that the temperature measurement result is inaccurate.

In order to solve the technical problem, the technical scheme of the application provides a fiber grating temperature measurement optical cable. The fiber grating temperature measurement optical cable provided by the technical scheme can be applied to scenes needing temperature measurement. During temperature measurement, the fiber bragg grating temperature measurement optical cable needs to be placed on the surface of an object to be measured.

Fig. 1 is a schematic structural diagram of an optical fiber grating temperature measurement optical cable provided in an embodiment of the present application. Referring to fig. 1, an optical fiber grating temperature measurement optical cable provided in an embodiment of the present application may include: the temperature measurement device comprises a protective sleeve 1 and a plurality of temperature measurement units 2 arranged in the protective sleeve. The plurality of temperature measuring units 2 include the same components, and the parameters of the components are different.

Protective sleeve 1 can constitute the outer wall of this application embodiment fiber grating temperature measurement optical cable, protective sleeve 1 can be stainless steel material, and protective sleeve 1's size can carry out the adaptability design according to the actual size of its content.

In practical application, the stainless steel protective sleeve 1 can protect the optical cable, so that the impact of external force on the optical cable is avoided, and the strength of the optical cable is enhanced. Meanwhile, the stainless steel material has good heat conduction property, so that the temperature of the object to be measured can be conducted to the temperature measuring unit 2, the protection of the temperature measuring unit 2 can be enhanced, the working performance of the temperature measuring unit 2 is not affected, and the accuracy of temperature measurement is ensured.

The material of protective sleeve 1 has the convertibility, also can be the material that other intensity are big and the heat conductivity is good, only need guarantee not influence the temperature measurement performance of optical cable can, this application does not do not specifically limit.

With continued reference to FIG. 1, the composition of a temperature measuring unit 2 is described. One temperature measuring unit 2 includes a trunk optical fiber 21, a wavelength division multiplexer WDM22, a connection optical fiber 23, and a fiber grating 24.

Fig. 2 is a schematic structural diagram of a wavelength division multiplexer according to an embodiment of the present application. As can be seen from fig. 2, the wavelength division multiplexer WDM22 includes a common port 221, a reflective port 222, and a transmissive port 223.

Fig. 3 is a schematic structural diagram of a fiber grating according to an embodiment of the present disclosure, and as can be seen from fig. 3, the fiber grating 24 may include a fixed end 241 and a free end 242, and the fixed end 241 and the free end 242 together form an entirety of the fiber grating 24. One end of the connection fiber 23 is connected to the fixed end 241, and the other end is connected to the reflection end 222. Through the connection, a temperature measuring unit 2 can be formed.

In practical applications, the sensitivity to temperature changes varies with the type of grating. In the technical solution of the present application, a Fiber Bragg Grating (FBG) may be adopted, and the type of the fiber bragg grating 24 may also be selected according to the actual situation, which is not specifically limited in the present application.

In combination with the above, it can be understood that, in the plurality of temperature measuring units 2 included in the fiber grating temperature measuring cable, each temperature measuring unit 2 includes the trunk optical fiber 21, the wavelength division multiplexer WDM22, the connection optical fiber 23, and the fiber grating 24, and is connected according to the above connection manner.

In some embodiments, for the fiber grating temperature measuring cable, n temperature measuring units 2 may be included therein, that is, n trunk optical fibers 21, n wavelength division multiplexers WDM22, n connecting optical fibers 23, and n fiber gratings 24 are included, where n is a natural number other than 0, and a specific value of n (the number of temperature measuring units 2 specifically included in the fiber grating temperature measuring cable) may be designed according to practical situations, and the present application is not limited specifically.

In the drawing that this application provided, use the one end of fiber grating temperature measurement optical cable as the head end, the other end is the tail end, extends from the head end is originated to the tail end, and temperature measuring unit 2 of including is 1 st temperature measuring unit 2 respectively, 2 nd temperature measuring unit 2, so on to this analogizes, to nth temperature measuring unit 2.

In the figures provided in this application, WDM₁I.e. the 1 st temperature measuring unit 2 of the fiber grating temperature measuring optical cable comprises a wavelength division multiplexer WDM22, WDM₂I.e. the wavelength division multiplexer WDM22, WDM included in the 2 nd temperature measuring unit 2 of the fiber grating temperature measuring cable_nNamely, the nth temperature measuring unit 2 of the fiber grating temperature measuring cable comprises a wavelength division multiplexer WDM22, and different figures can be referred to each other.

The specific connection mode of the n temperature measuring units 2 is as follows: one end of the main optical fiber 21 of the nth temperature measuring unit 2 is connected with the transmission end 223 of the (n-1) th temperature measuring unit 2, and the other end is connected with the common end 221 of the nth temperature measuring unit 2; so that the temperature measuring units 2 are connected in series in sequence to form a temperature measuring circuit.

In practical application, the temperature measuring circuit formed by connecting the n temperature measuring units 2 in series can measure the temperature of the surrounding environment.

In order to ensure the temperature measurement, the parameters of the devices included in the temperature measurement circuit need to be designed. Specifically, the wavelength of the fiber grating 24 included in the nth temperature measurement unit 2 is within the spectral range of the reflection end 222 of the nth temperature measurement unit 2. The fiber grating 24 and the wavelength division multiplexer WDM22 can work normally only when the nth temperature measurement unit 2 includes the fiber grating 24 with the wavelength in the spectral range of the reflection end 222 of the nth temperature measurement unit 2.

In some implementations, the thermometric unit 2 further includes a grating protection tube 25, the fiber grating 24 is disposed in the grating protection tube 25, and the free end 232 is in a free state in the grating protection tube 25.

That is, the fiber grating 24 in the grating protection tube 25 is in a single-end free state. When the fiber grating temperature measuring optical cable is acted by external force, the grating protection tube 25 firstly provides protection for the fiber grating 24 in the fiber grating protection tube, and the fiber grating 24 cannot deform along with the stress action when the fiber grating 24 is acted by external force because the single end of the fiber grating 24 is free, so that the temperature measuring performance is not influenced.

In practical applications, the grating protection tube 25 may be a Stainless steel capillary (Stainless steel capillary), which has good flexibility, corrosion resistance, high temperature resistance, wear resistance, tensile resistance, and water resistance and provides excellent electromagnetic shielding performance, and can provide better protection for the fiber grating 24 therein.

In order to provide sufficient protection for the fiber grating 24, the length of the grating protection tube 25 is greater than the length of the fiber grating 24. That is, in practical applications, the specific length of the grating protection tube 25 may be designed according to the length of the fiber grating 24, and the application is not limited in particular. The diameter of the grating protection tube 25 may be slightly larger than the size of the fiber grating 24 to ensure that the fiber grating 24 can be in a single-end free state in the grating protection tube 25.

Fig. 4 is a schematic structural diagram of another fiber grating temperature measurement optical cable according to an embodiment of the present disclosure, and as can be seen from fig. 4, the fiber grating temperature measurement optical cable further includes a tensile wire 3, where the tensile wire 3 extends in the protective sleeve 1 along an axial direction of the protective sleeve 1; the trunk optical fiber 21 and the wavelength division multiplexer WDM22 are fixedly connected to the tensile cord 3.

The fixing method of the trunk optical fiber 21 and the wavelength division multiplexer WDM22 to the tensile cord 3 may be bonding or tying. In practical application. The tensile wire 3 can improve the tensile property of the fiber grating temperature measurement optical cable and ensure that the fiber grating temperature measurement optical cable has good use performance.

In some implementation manners, the tensile wire 3 may be a kevlar wire, which has good tensile property and can provide better protection for the fiber grating temperature measurement optical cable.

The tension resisting wire 3 can also be selected from a high-horsepower wire and the like, and can be selected according to actual needs.

In some implementation manners, the temperature measurement range of the fiber grating temperature measurement optical cable provided by the embodiment of the application may be-50 ℃ to 150 ℃, and the temperature measurement range may also be changed by changing parameters of devices included in the fiber grating temperature measurement optical cable.

In some implementations, each fiber grating 24 is calibrated using a thermostatic bath prior to cabling of the thermometric cables. And after the calibration is finished, sequentially cabling. The problem that the cable is large in size after cabling and cannot be calibrated by using a constant temperature tank can be solved. When the fiber bragg grating is calibrated, cabled and installed on a test site, the fiber bragg grating 24 is in a free state in the capillary, so that the optical cable is high in temperature measurement accuracy.

Specifically, the fiber grating temperature measurement optical cable is assembled according to the following steps:

connecting the fiber grating 24 with the connecting optical fiber 23, and arranging the fiber grating 24 in the grating protection tube 25;

placing the fiber bragg grating 24, the connecting optical fiber 23 and the grating protection tube 25 into a constant-temperature oil groove to calibrate the fiber bragg grating 24;

after calibration is completed, connecting one end of the connecting optical fiber 23 far away from the fiber grating 24 with a reflection end 222 of a wavelength division multiplexer WDM 22;

connecting the main optical fiber 21 with the common end 221 of the wavelength division multiplexer WDM22 to form a temperature measuring unit 2;

one end of the main optical fiber 21 of the nth temperature measuring unit 2 is connected with the transmission end 223 of the (n-1) th temperature measuring unit 2, and the other end is connected with the common end 221 of the nth temperature measuring unit 2; so that the temperature measuring units 2 are connected in series in sequence to form a temperature measuring circuit.

Connecting the trunk optical fiber 32 and the wavelength division multiplexer WDM22 with a tensile wire 3;

the protective sleeve 1 is sleeved to form the fiber bragg grating temperature measuring optical cable.

That is to say, in the technical scheme provided by the present application, each fiber grating 24 can be calibrated individually, so that the fiber grating 24 is not stressed during the calibration process, and the form and the working performance of the fiber grating 24 can be ensured. In practical applications, the calibration temperature range of each fiber grating 24 can be selected according to practical situations.

The fiber grating temperature measurement optical cable provided by the embodiment of the application has the advantages that the different temperature measurement units 2 in the extending direction can measure the ambient temperature, and the accurate numerical value of the ambient temperature can be obtained by obtaining the information fed back by the fiber grating 24. Specifically, a demodulator may be connected to the fiber grating temperature measurement optical cable to form a temperature measurement system, and the wavelength value reflected by the fiber grating temperature measurement optical cable is obtained and the temperature of the object to be measured is calculated. The fiber grating temperature measurement optical cable provided by the embodiment of the application can also be flexibly applied to various temperature measurement environments, and is high in convenience.

According to the technical scheme, the fiber grating temperature measurement optical cable provided by the application comprises: the temperature measurement device comprises a protective sleeve 1 and a plurality of temperature measurement units 2 arranged in the protective sleeve 1; each temperature measuring unit 2 comprises a trunk optical fiber 21, a wavelength division multiplexer 22, a connecting optical fiber 23 and a fiber grating 24; the wavelength division multiplexer 22 includes a common terminal 221, a reflective terminal 222, and a transmissive terminal 223; the fiber grating 24 includes a fixed end 241 and a free end 242, and the fixed end 241 and the free end 242 form an integral body of the fiber grating 24; one end of the connecting optical fiber 23 is connected to the fixed end 241, and the other end is connected to the reflecting end 222; one end of the trunk optical fiber 21 of the nth temperature measuring unit 2 is connected with the transmission end 223 of the (n-1) th temperature measuring unit 2, and the other end is connected with the common end 221 of the nth temperature measuring unit 2; so that the temperature measuring units 2 are connected in series in sequence to form a temperature measuring circuit. According to the technical scheme, the fiber grating 24 is in a single-end free state, the fiber grating 24 can be calibrated independently, the stress effect influence is small, and the temperature measurement result is more accurate.

The embodiments provided in the present application are only a few examples of the general concept of the present application, and do not limit the scope of the present application. Any other embodiments extended according to the scheme of the present application without inventive efforts will be within the scope of protection of the present application for a person skilled in the art.