Temperature measuring optical fiber, manufacturing method of temperature measuring optical fiber and interferometer

Abstract

The invention relates to the technical field of optical fiber temperature measurement, in particular to a temperature measurement optical fiber, a manufacturing method of the temperature measurement optical fiber and an interferometer. The temperature measurement optical fiber comprises an optical fiber body; the optical fiber body is arranged in the first capillary tube in a penetrating manner, and the first capillary tube has a first thermal expansion coefficient; the first capillary tube is arranged in the second capillary tube in a penetrating manner, and the second capillary tube has a second thermal expansion coefficient; wherein the first thermal expansion coefficient is not equal to the second thermal expansion coefficient. The optical fiber body is packaged through double capillaries, the temperature sensitivity of the temperature measurement optical fiber is improved, and the influence of external stress on the measurement temperature of the optical fiber body is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of optical fiber temperature measurement, and in particular to a temperature measuring optical fiber, a manufacturing method of the temperature measuring optical fiber, and an interferometer. Background Art

[0002] At present, with the continuous improvement of my country's scientific and technological level, the development of the sensor field is also becoming more and more perfect. The development of optical fiber temperature sensors can be traced back to the early 1970s, when it was discovered that the bending and elongation of optical fibers would affect the optical signal, so research began on how to use this effect for temperature measurement.

[0003] In the initial research, temperature sensors mainly inferred temperature by measuring the change in the length of the optical fiber. However, the accuracy of this method is limited and is greatly affected by external factors. Later, researchers found that the temperature can be measured more accurately by using the thermoreflection effect of optical fiber. In this method, the medium inside the optical fiber will cause the refractive index to change due to temperature changes, which will cause the frequency and phase of the reflected light to change. By analyzing these changes, very accurate temperature measurement results can be obtained. With the continuous development of technology, the principles and applications of fiber optic temperature sensors are becoming more and more abundant and extensive, involving optics, optoelectronics, mechanics, thermal and other fields. Fiber optic temperature sensors based on different principles such as Raman scattering, Brillouin scattering, fiber grating, MZ interference principle, etc. have gradually been developed. They are widely used in industry, medical care, environmental protection, safety and other fields, and have become an important measurement and monitoring technology.

[0004] However, in the related art, the optical fiber has a low sensitivity to temperature, resulting in poor accuracy of the demodulated temperature. Therefore, it is urgent to propose a structure or method for improving the sensitivity of the optical fiber to temperature. Summary of the invention

[0005] The embodiments of the present application provide a temperature measuring optical fiber, a manufacturing method of the temperature measuring optical fiber, and an interferometer. By encapsulating the optical fiber body with double capillaries, the temperature sensitivity of the temperature measuring optical fiber is improved, and the influence of external stress on the measured temperature of the optical fiber body is reduced.

[0006] In some embodiments, a temperature measuring optical fiber is provided, comprising: an optical fiber body; a first capillary, the optical fiber body is passed through the first capillary, and the first capillary has a first thermal expansion coefficient; a second capillary, the first capillary is passed through the second capillary, and the second capillary has a second thermal expansion coefficient; wherein the first thermal expansion coefficient and the second thermal expansion coefficient are not equal.

[0007] The temperature measuring optical fiber provided by the embodiment of the present application is used. When the measured ambient temperature changes, the first capillary and the second capillary having different thermal expansion coefficients are simultaneously affected, and the changes in the expansion lengths of the first capillary and the second capillary are different. In addition to the measured ambient temperature, the difference between the changes in the first capillary and the second capillary will also cause axial strain to the optical fiber, thereby improving the temperature sensitivity of the temperature measuring optical fiber and realizing the sensitivity enhancement of the temperature measuring optical fiber. In addition, by setting the second capillary, the influence of external stress on the first capillary is reduced, thereby reducing the influence on the optical fiber body, reducing the effect of external stress and strain on the first capillary, and avoiding the external force from being transmitted to the optical fiber body through the first capillary. This can greatly reduce the influence of the external environment.

[0008] Optionally, the length of the first capillary is a first length, the length of the second capillary is a second length, and the length of the optical fiber body is a third length; the first length and the second length are both smaller than the third length.

[0009] Optionally, the caliber of the first capillary is a first caliber A, the caliber of the second capillary is a second caliber B, and the outer diameter of the optical fiber body is a third caliber C; C <A<B。

[0010] Optionally, the first capillary and the second capillary are metal capillaries or alloy capillaries.

[0011] Optionally, the first capillary tube and the exposed portion of the optical fiber body are bonded with metal glue; and the second capillary tube and the exposed portion of the optical fiber body are bonded with metal glue.

[0012] Optionally, the temperature measuring optical fiber further includes: a protective tube, which is sleeved outside the optical fiber body, the first capillary tube and the second capillary tube.

[0013] Optionally, the temperature measuring optical fiber further includes: an optical fiber sheath, which is arranged at both end ports of the protective tube, and the optical fiber body is passed through the optical fiber sheath to fix the optical fiber body and the protective tube.

[0014] Optionally, the optical fiber sheath and the protective tube are bonded with epoxy resin.

[0015] In some embodiments, a method for manufacturing a temperature measuring optical fiber is provided, comprising: S1, inserting an optical fiber body into a first capillary; S2, applying a constant first tensile force at both ends of the optical fiber body, and using metal glue to fix the optical fiber body exposed in the first capillary and the first capillary to obtain a first combined tube; S3, inserting the first combined tube into a second capillary; the first capillary has a first thermal expansion coefficient, the second capillary has a second thermal expansion coefficient, and the first thermal expansion coefficient and the second thermal expansion coefficient are not equal; S4, applying a constant second tensile force at both ends of the optical fiber body, and using metal glue to fix the optical fiber body exposed in the second capillary and the second capillary to obtain a second combined tube; the first tensile force and the second tensile force are equal or unequal; S5, inserting the second combined tube into a protective tube; S6, inserting the optical fiber body into an optical fiber sheath to fix the protective tube and the second combined tube using the optical fiber sheath; S7, using epoxy resin to bond the optical fiber sheath and the protective tube.

[0016] In some embodiments, an interferometer is provided, comprising: a laser, a temperature measuring optical fiber and a demodulation module; the laser is configured to output laser pulses to the temperature measuring optical fiber; the temperature measuring optical fiber comprises a temperature measuring optical fiber as in any one of the above embodiments, or a temperature measuring optical fiber manufactured by the manufacturing method of the temperature measuring optical fiber in the above embodiments; the demodulation module is configured to obtain an optical signal output by the temperature measuring optical fiber, and perform demodulation according to the optical signal.

[0017] It can be understood that the beneficial effects that can be achieved by the manufacturing method of the temperature measuring optical fiber and the technical solution provided by the interferometer provided above can be referred to the beneficial effects of the temperature measuring optical fiber and any of its optional embodiments, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 A schematic diagram of the structure of the first temperature measuring optical fiber provided in an embodiment of the present application; Figure 2 For along Figure 1 A cross-sectional view of the temperature measuring optical fiber along the axial direction in the illustrated embodiment; Figure 3 A schematic diagram of the structure of a second temperature measuring optical fiber provided in an embodiment of the present application; Figure 4 For along Figure 3 A cross-sectional view of the temperature measuring optical fiber along the axial direction in the illustrated embodiment; Figure 5 A flow chart of a method for manufacturing a temperature measuring optical fiber provided in an embodiment of the present application; Figure 6 is a schematic diagram of the structure of an optical fiber; Figure 7 A structural block diagram of an interferometer provided in an embodiment of the present application; Figure 8 A structural block diagram of another interferometer provided in an embodiment of the present application; Fig. 9 A fitting curve output by the interferometer provided in an embodiment of the present application; Fig.10 A graph showing the relationship between the number of right-shifted fringes and the temperature function provided in an embodiment of the present application; Fig.11 A graph showing the relationship between the number of left-shifted fringes and the temperature function provided in an embodiment of the present application.

[0020] Reference numerals: 101, fiber core; 102, cladding; 103, coating layer; 104, sheath; 100, temperature measuring optical fiber; 10, optical fiber body; 20, first capillary tube; 30, second capillary tube; 40, protective tube; 50, optical fiber sheath; 501, first sheath; 502, second sheath; 200, interferometer; 201, laser; 202, demodulation module; 2021, computer; 2022, mobile phone; 203, condenser; 204, first spectrometer; 205, second spectrometer. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, other embodiments obtained by ordinary technicians in this field without making creative work all belong to the protection scope of the present application.

[0022] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0023] In addition, in the present application, directional terms such as "upper", "lower", "inner" and "outer" are defined relative to the orientation of the components schematically placed in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to the changes in the orientation of the components placed in the drawings.

[0024] In order to facilitate the understanding of the technical solution of the application, the relevant technologies involved in this application are first explained below.

[0025] With the continuous improvement of my country's scientific and technological level, the development of the sensor field is also becoming more and more perfect. Optical fiber is the leader in the field of modern communications and is being used more and more widely. As a new type of temperature detection equipment, the optical fiber temperature sensor has the advantages of simple structure and strong anti-interference. With the continuous development of science and technology, the accuracy, portability, and application range of optical fiber temperature sensors will continue to improve. In the future, optical fiber temperature sensors are expected to be more widely used in medical, aerospace and other fields, providing more accurate and efficient temperature monitoring solutions for all walks of life. In the future, with the continuous innovation of technology, the application scope of optical fiber temperature sensors will be further expanded, bringing more convenience and reliability to the development and progress of human society. Optical fiber temperature sensor is a new type of temperature measurement technology developed in the 1970s. It transmits information based on optical signals and has advantages such as insulation, anti-electromagnetic interference, and high voltage resistance.

[0026] Optical fiber can be used as a medium for data transmission or as a variety of sensors. Optical fiber sensors are particularly effective in situations where electromagnetic noise is high and electrical signals are not suitable. Optical fiber temperature sensors mainly use light as the optical path medium to separate the measuring instrument and the temperature measuring probe. At the same time, in order to better realize the adaptability of optical fiber temperature sensors, they can work in high voltage and high interference environments to achieve accurate temperature measurement results.

[0027] Optical fiber communication is a communication method that uses laser as the carrier of information and optical fiber as the transmission medium. Therefore, the two most important key technologies for the realization of modern information society are laser and optical fiber. Optical fiber is the abbreviation of optical fiber. It is a dielectric waveguide that works in the light wave band. It uses the principle of total optical reflection to confine the energy of light within the waveguide interface where light absorption and light scattering are very small, and guide the light wave to propagate along the axis of the optical fiber.

[0028] In the related technology, the bare optical fiber is sensitive to both temperature and strain. When the bare optical fiber is packaged, a part of the optical fiber and a material with a high thermal expansion coefficient are packaged together through reasonable structural design. When the measured temperature changes, a strain is applied to the optical fiber through the deformation of the high thermal expansion coefficient material, causing the optical fiber to produce axial strain, thereby achieving a sensitivity enhancement effect.

[0029] At present, most sensors are packaged based on this principle as follows: directly stick the bare optical fiber on the material with high thermal expansion coefficient. When the temperature rises, the material with high thermal expansion coefficient directly pulls the optical fiber, increasing the axial strain of the optical fiber, thereby achieving the sensitivity enhancement effect for the optical fiber temperature sensor. However, this sensitivity enhancement method has obvious disadvantages: the sensitivity enhancement effect is restricted by the thermal expansion coefficient of the material, and the resolution of the measured temperature data is limited.

[0030] Moreover, most sensors currently only use plastic sleeves or stainless steel packaging tubes to encapsulate bare optical fibers with high thermal expansion coefficient materials. This will cause a greater impact on the optical fiber if there is a certain pressure interference from the outside world, thus causing a series of errors in the experiment.

[0031] In order to solve the above technical problems, the embodiment of the present application provides a temperature measuring optical fiber 100, a manufacturing method of the temperature measuring optical fiber and an interferometer 200. By using bimetal packaging technology, the temperature sensitivity, resolution and anti-interference ability of the temperature measuring optical fiber 100 are improved, thereby improving the accuracy of temperature measurement by the interferometer.

[0032] Figure 1 This is a schematic structural diagram of the first temperature measuring optical fiber 100 provided in an embodiment of the present application.

[0033] Figure 2 For along Figure 1 A sectional view of the temperature measuring optical fiber 100 in the axial direction in the illustrated embodiment.

[0034] Combination Figure 1 and Figure 2 As shown, the temperature measuring optical fiber 100 provided in the embodiment of the present application includes: an optical fiber body 10, a first capillary 20 and a second capillary 30. The optical fiber body 10 is inserted into the first capillary 20, the first capillary 20 has a first thermal expansion coefficient, the first capillary 20 is inserted into the second capillary 30, and the second capillary 30 has a second thermal expansion coefficient. The first thermal expansion coefficient and the second thermal expansion coefficient are not equal.

[0035] By using the temperature measuring optical fiber 100 provided in the embodiment of the present application, when the measured ambient temperature changes, the first capillary 20 and the second capillary 30 with different thermal expansion coefficients are simultaneously affected, and the changes in the expansion lengths of the first capillary 20 and the second capillary 30 are different. In addition to the measured ambient temperature, the difference between the changes in the first capillary 20 and the second capillary 30 will also cause axial strain to the optical fiber, thereby improving the temperature sensitivity of the temperature measuring optical fiber 100 and realizing the sensitivity enhancement of the temperature measuring optical fiber 100. In addition, by providing the second capillary 30, the influence of external stress on the first capillary 20 is reduced, thereby reducing the influence on the optical fiber body 10, isolating the effect of external stress and strain on the first capillary 20, and reducing the external force transmitted to the optical fiber body 10 through the first capillary 20. In this way, the influence of the external environment can be greatly reduced.

[0036] Specifically, the embodiment of the present application provides a temperature measuring optical fiber 100 that uses the optical fiber light transmission principle and the optical fiber thermo-optical effect to accurately measure the ambient temperature. In the packaging process of the optical fiber sensor, a bimetal packaging technology is used, so that the temperature sensor has higher temperature sensitivity, higher resolution and stronger anti-interference ability than traditional temperature sensors.

[0037] Specifically, the temperature sensitivity of the temperature measuring optical fiber 100 can be further changed as required by selecting the first capillary 20 and the second capillary 30 with a large difference in thermal expansion coefficient. For example, an iron-nickel alloy capillary (first capillary 20) and a copper capillary (second capillary 30) with a large difference in thermal expansion coefficient are selected to make the change in the length of the second capillary 30 greater than the change in the length of the first capillary 20, so that the difference between the changes is transmitted to the temperature measuring optical fiber 100, affecting more axial strain of the temperature measuring optical fiber 100, so as to further improve the temperature sensitivity of the temperature measuring optical fiber 100.

[0038] It should be understood that the embodiment of the present application does not limit which capillary has a larger thermal expansion coefficient between the first capillary 20 and the second capillary 30, as long as the two are not equal, that is, the first thermal expansion coefficient can be greater than the second thermal expansion coefficient, or the first thermal expansion coefficient can be less than the second thermal expansion coefficient.

[0039] Optionally, combined Figure 2 As shown, the length of the first capillary 20 is a first length L1, the length of the second capillary 30 is a second length L2, and the length of the optical fiber body 10 is a third length L3; the first length and the second length are both smaller than the third length.

[0040] In this embodiment, by limiting the first capillary 20 and the second capillary 30 to be shorter than the optical fiber body 10, the difference between the change amounts of the first capillary 20 and the second capillary 30 causes axial strain to the optical fiber body 10 through the optical fiber body 10 connected thereto, thereby improving the temperature sensitivity of the temperature measuring optical fiber 100 and realizing sensitivity enhancement of the temperature measuring optical fiber 100.

[0041] Exemplarily, the temperature sensitivity of the temperature measuring optical fiber 100 can be further changed as required by adjusting the length of the first capillary 20 and the length of the second capillary 30. For example, the first capillary 20 is selected to have a smaller difference in thermal expansion coefficient, but the length of the second capillary 30 is smaller than the length of the second capillary 30, so that the change in the length of the second capillary 30 is greater than the change in the length of the first capillary 20, so that the difference between the changes is transmitted to the temperature measuring optical fiber 100, affecting more axial strain of the temperature measuring optical fiber 100, so as to further improve the temperature sensitivity of the temperature measuring optical fiber 100.

[0042] Optionally, combined Figure 2 As shown, the caliber of the first capillary 20 is a first caliber A, the caliber of the second capillary 30 is a second caliber B, and the outer diameter of the optical fiber body 10 is a third caliber C; C <A<B。

[0043] In this embodiment, the caliber of the first capillary 20 is set to be larger than the outer diameter of the optical fiber body 10, so that the optical fiber body 10 can be inserted into the first capillary 20. The caliber of the second capillary 30 is set to be larger than the caliber of the first capillary 20, so that the first combined tube composed of the optical fiber body 10 and the first capillary 20 can be inserted into the second capillary 30 to form a second combined tube. Thus, the temperature sensitivity of the optical fiber body 10 is increased by using the first capillary 20 and the second capillary 30, and the accuracy of the temperature measured by the temperature measuring optical fiber 100 can be improved.

[0044] It is understandable that the embodiment of the present application does not limit the specific dimensions of the apertures of the first capillary 20 and the second capillary 30 , as long as the optical fiber body 10 can be passed through the first capillary 20 and the first capillary 20 can be passed through the second capillary 30 .

[0045] Optionally, the first capillary 20 and the second capillary 30 are metal capillaries or alloy capillaries.

[0046] In this embodiment, by limiting the first capillary 20 and the second capillary 30 to metal capillaries, the change in ambient temperature is transmitted to the second capillary 30 by utilizing the heat conduction property of metal, and then transmitted from the second capillary 30 to the first capillary 20, and then transmitted from the first capillary 20 to the optical fiber body 10, thereby realizing the detection of ambient temperature. In addition, the thermal expansion coefficients of different metal capillaries vary greatly, so that the magnitude of the axial strain of the optical fiber body 10 caused can be increased.

[0047] Specifically, since the first capillary 20 and the second capillary 30 are both metal materials with good thermal conductivity, the temperature can be transferred to the optical fiber body 10 through the second capillary 30 and the first capillary 20, so that the refractive index of the optical fiber changes in response to temperature changes. Even changes in the external ambient temperature can affect the propagation of the optical signal in the optical fiber body 10, thereby realizing the temperature measurement function of the temperature measuring optical fiber 100.

[0048] Optionally, the first capillary tube 20 and the exposed portion of the optical fiber body 10 are bonded with metal glue. The second capillary tube 30 and the exposed portion of the optical fiber body 10 are bonded with metal glue.

[0049] In this embodiment, the optical fiber body 10, the first capillary 20 and the second capillary 30 are fixed by using metal glue to fix the relative positions of the optical fiber body 10, the first capillary 20 and the second capillary 30. When the temperature measuring optical fiber 100 is used to measure the ambient temperature, the movement of the first capillary 20 and the second capillary 30 relative to the optical fiber body 10 is reduced, thereby improving the structural stability of the temperature measuring optical fiber 100.

[0050] Figure 3 This is a schematic structural diagram of a second temperature measuring optical fiber 100 provided in an embodiment of the present application.

[0051] Figure 4 For along Figure 3 A sectional view of the temperature measuring optical fiber 100 in the axial direction in the illustrated embodiment.

[0052] Optionally, combined Figure 3 and Figure 4 As shown, the temperature measuring optical fiber 100 further includes a protective tube 40 . The protective tube 40 is sleeved outside the optical fiber body 10 , the first capillary tube 20 and the second capillary tube 30 .

[0053] In this embodiment, a protective tube 40 is sleeved on the outside of the optical fiber body 10, the first capillary tube 20 and the second capillary tube 30 to improve the mechanical strength of the temperature measuring optical fiber 100, protect the optical fiber body 10, the first capillary tube 20 and the second capillary tube 30, and reduce damage to the optical fiber body 10, the first capillary tube 20 and the second capillary tube 30.

[0054] Optionally, combined Figure 4As shown, the length of the protective tube 40 is a fourth length L4, the fourth length is greater than the longest length between the first length and the second length, and the fourth length is less than the third length.

[0055] Optionally, combined Figure 4 As shown, the diameter of the protective tube 40 is a fourth diameter D, and the fourth diameter is larger than the second diameter.

[0056] Optionally, the temperature measuring optical fiber 100 further includes: an optical fiber sheath 50 . The optical fiber sheath 50 is disposed at both end ports of the protective tube 40 , and the optical fiber body 10 is passed through the optical fiber sheath 50 to fix the optical fiber body 10 and the protective tube 40 .

[0057] In this embodiment, optical fiber sheaths 50 are provided at both end ports of the protective tube 40 to form a temperature measuring cavity between the protective tube 40 and the optical fiber sheath 50 to accommodate the optical fiber body 10, the first capillary 20 and the second capillary 30, thereby reducing the entry of foreign matter into the temperature measuring cavity and causing damage to the optical fiber body 10, the first capillary 20 and the second capillary 30.

[0058] Optionally, the optical fiber sheath 50 includes a first sheath 501 and a second sheath 502. The protective tube 40 includes a first port and a second port. The first sheath 501 is disposed at the first port to close the first port. The second sheath 502 is disposed at the second port to close the second port.

[0059] In this embodiment, a first sheath 501 and a second sheath 502 are respectively provided at both ends of the protective tube 40 , thereby enclosing the internal space of the protective tube 40 to form a temperature measurement cavity.

[0060] Optionally, the optical fiber sheath 50 and the protective tube 40 are bonded with epoxy resin.

[0061] In this embodiment, the optical fiber sheath 50 and the protective tube 40 are bonded by using epoxy resin to fix the optical fiber sheath 50 and the protective tube 40 to form a temperature measuring cavity to protect the optical fiber body 10, the first capillary 20 and the second capillary 30, reduce damage to the optical fiber body 10, the first capillary 20 and the second capillary 30, complete the packaging of the temperature measuring optical fiber 100, improve the temperature sensitivity of the temperature measuring optical fiber 100, and reduce the influence of external stress on the temperature measuring optical fiber 100.

[0062] Optionally, the first sheath 501 and the second sheath 502 are bonded to the protective tube 40 by using epoxy resin.

[0063] Figure 5 Flow chart of a method for manufacturing the temperature measuring optical fiber 100 provided in an embodiment of the present application.

[0064] Combination Figure 5As shown, the embodiment of the present application also provides a method for manufacturing a temperature measuring optical fiber 100, including steps S1 to S7, which are specifically as follows: S1 , inserting the optical fiber body 10 into the first capillary tube 20 .

[0065] Specifically, before step S1, step S11 is also included, which is as follows: Step S11 , removing the coating layer 103 and the sheath 104 of the optical fiber to obtain the optical fiber body 10 , which includes a core 101 and a cladding 102 .

[0066] Figure 6 Schematic diagram of the optical fiber structure.

[0067] like Figure 6 As shown, the optical fiber mainly includes four layers: a core 101, a cladding 102, a coating 103 and a sheath 104. The coating 103 and the sheath 104 are used to provide protection for the core 101 and the cladding 102 and improve the mechanical strength of the core 101 and the cladding 102.

[0068] For example, the fiber core 101 is generally composed of high-purity SiO2 with a diameter of 5 to 50 μm and doped with a small amount of P2O5 and GeO2. The function of the dopant is to increase the refractive index of the fiber core 101. In order to reduce light scattering and light absorption, the impurity content of the fiber core 101 is generally not more than 10 -6 Micrometers. The cladding 102 is also mainly composed of high-purity SiO2, doped with a small amount of fluorine and boron to reduce its refractive index. The diameter of the cladding 102 is generally 125μm. The coating layer 103 outside the cladding 102 is generally epoxy resin or silicone rubber, and its function is to enhance the mechanical strength of the optical fiber. The outermost layer of the optical fiber is the sheath 104, which is mostly made of nylon or polyethylene, and its function is also to enhance the mechanical strength of the optical fiber.

[0069] S2, applying a constant first tensile force to both ends of the optical fiber body 10, and fixing the optical fiber body 10 exposed in the first capillary tube 20 and the first capillary tube 20 with metal glue to obtain a first combined tube.

[0070] In this step, a first pulling force is applied to both ends of the optical fiber body 10 so that the optical fiber body 10 is straightened, so as to facilitate the installation and fixation of the optical fiber body 10 and the first capillary tube 20 .

[0071] S3, insert the first combined tube into the second capillary tube 30. The first capillary tube 20 has a first thermal expansion coefficient, the second capillary tube 30 has a second thermal expansion coefficient, and the first thermal expansion coefficient and the second thermal expansion coefficient are not equal.

[0072] S4, applying a constant second tension to both ends of the optical fiber body 10, fixing the optical fiber body 10 exposed in the second capillary tube 30 and the second capillary tube 30 with metal glue to obtain a second combined tube. The first tension and the second tension are equal or different.

[0073] In this step, a second pulling force is applied to both ends of the optical fiber body 10 so that the optical fiber body 10 is straightened, so as to facilitate the installation and fixation of the optical fiber body 10 and the second capillary 30 .

[0074] S5, inserting the second combined pipe into the protective pipe 40.

[0075] S6, inserting the optical fiber body 10 into the optical fiber sheath 50, so as to use the optical fiber sheath 50 to fix the protective tube 40 and the second combined tube.

[0076] In steps S5 and S6, the second combined tube is inserted into the protective tube 40 and encapsulated with the optical fiber sheath 50, so as to improve the mechanical strength of the second combined tube by using the protective tube 40 and the optical fiber sheath 50.

[0077] S7, using epoxy resin to bond the optical fiber sheath 50 and the protective tube 40.

[0078] By adopting the manufacturing method of the temperature measuring optical fiber 100 provided in the embodiment of the present application, the temperature sensitivity of the optical fiber body 10 is improved and the influence of external stress on the optical fiber body 10 is reduced by using the first capillary 20 and the second capillary 30 with different thermal expansion coefficients. The mechanical strength of the temperature measuring optical fiber 100 is further improved by providing the protective tube 40 and the optical fiber jacket 50.

[0079] Specifically, when the measured ambient temperature changes, the first capillary 20 and the second capillary 30 having different thermal expansion coefficients are simultaneously affected, and the changes in the expansion lengths of the first capillary 20 and the second capillary 30 are different. In addition to the measured ambient temperature, the difference between the changes in the first capillary 20 and the second capillary 30 will also cause axial strain to the optical fiber, thereby improving the temperature sensitivity of the temperature measuring optical fiber 100 and realizing the sensitivity enhancement of the temperature measuring optical fiber 100. In addition, by providing the second capillary 30, the influence of external stress on the first capillary 20 is reduced, thereby reducing the influence on the optical fiber body 10, isolating the effect of external stress and strain on the inner tube, and avoiding the external force from being transmitted to the optical fiber through the inner tube. In this way, the influence of the external environment can be greatly reduced.

[0080] Figure 7 A structural block diagram of an interferometer 200 provided in an embodiment of the present application.

[0081] Combination Figure 7As shown, the embodiment of the present application further provides an interferometer 200, comprising: a laser 201, a temperature measuring optical fiber 100 and a demodulation module 202. The laser 201 is configured to output laser pulses to the temperature measuring optical fiber 100. The temperature measuring optical fiber 100 comprises the temperature measuring optical fiber 100 as in any one of the above embodiments, or the temperature measuring optical fiber 100 manufactured by the manufacturing method of the temperature measuring optical fiber 100 in the above embodiments. The demodulation module 202 is configured to obtain an optical signal output by the temperature measuring optical fiber 100, and perform demodulation according to the optical signal.

[0082] In the interferometer 200 provided in the embodiment of the present application, the temperature measuring optical fiber 100 adopts the temperature measuring optical fiber 100 described in the above embodiment or the temperature measuring optical fiber 100 manufactured by the manufacturing method of the temperature measuring optical fiber 100 in the above embodiment, so as to improve the temperature sensitivity of the temperature measuring optical fiber 100 and reduce the influence of external stress on the temperature measurement of the temperature measuring optical fiber 100. Thus, the accuracy of the temperature information demodulated by the interferometer 200 is improved.

[0083] It should be understood that the demodulation module 202 can be any electronic device that can obtain the optical signal output by the temperature measurement optical fiber 100 and perform demodulation according to the optical signal, for example Figure 7 A computer 2021, a mobile phone 2022 or a tablet computer (not shown in the figure) is used.

[0084] Figure 8 A structural block diagram of another interferometer provided in an embodiment of the present application.

[0085] Exemplarily, the interferometer is an M-Z (Mach-Zehnder) fiber interferometer, which includes a reference arm and a sensor arm, wherein the reference arm is used to provide a phase reference; the sensor arm is used for optical phase modulation and is sensitive to changes in the physical quantity to be measured. The laser 201 is a helium-neon laser. The laser emitted by the helium-neon laser is divided into two paths by a beam splitter and respectively sent to two temperature measurement optical fibers 100 of substantially the same length. The output ends of the two temperature measurement optical fibers are combined together, and an interference light field will appear in the overlapping area of ​​the output light spots.

[0086] Specifically, combined Figure 8As shown, the interferometer also includes a condenser 203, a first beam splitter 204 and a second beam splitter 205. The laser 201 emits laser light to the condenser 203, and the condenser 203 is configured to condense the laser light output by the laser 201. The first beam splitter 204 divides the beam condensed by the condenser 203 into a first sub-beam and a second sub-beam. The first sub-beam is output to the second beam splitter 205 through the reference arm RA (including the temperature measurement optical fiber 100), and the second sub-beam is output to the second beam splitter 205 through the sensor arm SA (including the temperature measurement optical fiber 100). The light P output by the second beam splitter includes a reference light P1 and a sensing light P2 with a phase difference, so that the measured temperature information corresponding to the sensing light P2 can be determined by demodulating the phase difference between the reference light P1 and the sensing light P2. The static characteristics of the interferometer represent the input or output relationship of the sensor when the various values ​​of the measured input quantity are in a stable state. The main technical indicators for measuring the static characteristics of the interferometer are: linearity, sensitivity, hysteresis and repeatability. The embodiment of this application mainly studies the linearity and sensitivity of the interferometer. Linearity is an indicator that characterizes the degree of fit between the sensor output or input calibration curve and the selected fitting straight line. It is usually expressed in terms of relative error. To express linearity, that is: Formula (1); In formula (1), is the maximum deviation between the output mean and the fitted straight line, For the theoretical full-scale output, the least squares straight line method is used.

[0087] Fig. 9 It is the fitting curve output by the interferometer 200 provided in the embodiment of the present application. Fig. 9 (a) is the fitting curve of the output of the interferometer 200 when the temperature rises. Fig. 9 (b) is a fitting curve of the output of the interferometer 200 when the temperature is reduced.

[0088] Combination Fig. 9 As shown in (a), the linearity of the interferometer 200 when the temperature is increased for : .

[0089] Combination Fig. 9 As shown in (b), the linearity of the interferometer 200 when the temperature is reduced for : .

[0090] Specifically, the light intensity sensor directly measures the laser light intensity emitted by the laser ( ) is 2.092, the coupling efficiency The calculation formula is shown in formula (2): Formula (2).

[0091] The light intensity measured when the laser is directly coupled to the optical fiber ( ) is 628, and the measured data is substituted into the coupling efficiency The calculation formula for the direct coupling efficiency between light and optical fiber is obtained (%) is 0.03: .

[0092] The light intensity measured by the power meter when the laser is indirectly coupled to the optical fiber ( ) is 1778, and the measured data is substituted into the coupling efficiency The calculation formula for the indirect coupling efficiency between light and optical fiber is obtained. (%) is 0.085: .

[0093] Fig.10 A graph showing the relationship between the number of right-shifted fringes and the temperature function provided in an embodiment of the present application.

[0094] During the heating process, the interference light fringes generated by the sensing light shift to the right compared to the interference light fringes of the reference light.

[0095] Table 1

[0096] According to the data shown in Table 1 above, we can get Fig.10 A graph showing the relationship between the number of right-shifted fringes and temperature as a function of temperature.

[0097] Depend on Fig.10 It can be seen that: ,and , further calculate the temperature rise sensitivity (i.e., the temperature sensitivity of the temperature measuring optical fiber when the temperature rises) is obtained: .

[0098] Fig.11 A graph showing the relationship between the number of left-shifted fringes and the temperature function provided in an embodiment of the present application.

[0099] During the cooling process, the interference light fringes generated by the sensing light shift to the left compared to the interference light fringes of the reference light.

[0100] Table 2

[0101] According to the data shown in Table 2 above, we can get Fig.11 A graph showing the relationship between the number of left-shifted fringes and the temperature function.

[0102] Depend on Fig.11 It can be seen that: ,and , further calculate the cooling sensitivity (i.e., the temperature sensitivity of the temperature measuring optical fiber when the temperature drops) is obtained: .

[0103] From the above calculation results, it can be seen that the temperature sensitivity of the temperature measuring optical fiber in the embodiment of the present application is greatly improved compared with the related art.

[0104] It should be noted that those skilled in the art will easily think of other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application. The specification and examples are only regarded as exemplary, and the true scope of the present application is indicated by the claims.

[0105] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A temperature measuring optical fiber, characterized in that: include: Optical fiber body (10); A first capillary tube (20), wherein the optical fiber body (10) is inserted into the first capillary tube (20), and the first capillary tube (20) has a first thermal expansion coefficient; a second capillary tube (30), wherein the first capillary tube (20) is inserted into the second capillary tube (30), and the second capillary tube (30) has a second thermal expansion coefficient; Wherein, the first thermal expansion coefficient and the second thermal expansion coefficient are not equal.

2. The temperature measuring optical fiber according to claim 1, characterized in that: The length of the first capillary tube (20) is a first length, the length of the second capillary tube (30) is a second length, and the length of the optical fiber body (10) is a third length; The first length and the second length are both smaller than the third length.

3. The temperature measuring optical fiber according to claim 1, characterized in that: The caliber of the first capillary tube (20) is a first caliber A, the caliber of the second capillary tube (30) is a second caliber B, and the outer diameter of the optical fiber body (10) is a third caliber C; <A<B。 4. The temperature measuring optical fiber according to claim 1, characterized in that: The first capillary (20) and the second capillary (30) are metal capillaries or alloy capillaries.

5. The temperature measuring optical fiber according to any one of claims 1 to 4, characterized in that: The first capillary (20) and the exposed portion of the optical fiber body (10) are bonded together using metal glue; The second capillary (30) and the exposed portion of the optical fiber body (10) are bonded together using metal glue.

6. The temperature measuring optical fiber according to any one of claims 1 to 4, characterized in that: Also includes: A protective tube (40), the protective tube (40) being sleeved outside the optical fiber body (10), the first capillary tube (20) and the second capillary tube (30).

7. The temperature measuring optical fiber according to claim 6, characterized in that: Also includes: Optical fiber sheaths (50) are arranged at two end ports of the protective tube (40), and the optical fiber body (10) is inserted into the optical fiber sheaths (50) to fix the optical fiber body (10) and the protective tube (40).

8. The temperature measuring optical fiber according to claim 7, characterized in that: The optical fiber sheath (50) and the protective tube (40) are bonded with epoxy resin.

9. A method for manufacturing a temperature measuring optical fiber, characterized in that: include: S1, inserting an optical fiber body (10) into a first capillary tube (20); S2, applying a constant first tensile force to both ends of the optical fiber body (10), and fixing the optical fiber body (10) exposed in the first capillary tube (20) and the first capillary tube (20) using metal glue to obtain a first combined tube; S3, inserting the first combined tube into the second capillary tube (30); the first capillary tube (20) has a first thermal expansion coefficient, the second capillary tube (30) has a second thermal expansion coefficient, and the first thermal expansion coefficient and the second thermal expansion coefficient are not equal; S4, applying a constant second tensile force to both ends of the optical fiber body (10), fixing the optical fiber body (10) exposed in the second capillary tube (30) and the second capillary tube (30) using metal glue, to obtain a second combined tube; the first tensile force and the second tensile force are equal or unequal; S5, inserting the second combined pipe into the protective pipe (40); S6, inserting the optical fiber body (10) into the optical fiber sheath (50), so as to use the optical fiber sheath (50) to fix the protective tube (40) and the second combined tube; S7, using epoxy resin to bond the optical fiber sheath (50) and the protective tube (40).

10. An interferometer, characterized in that: include: A laser (201), a temperature measuring optical fiber (100) and a demodulation module (202); The laser (201) is configured to output laser pulses to the temperature measuring optical fiber (100); The temperature measuring optical fiber (100) comprises the temperature measuring optical fiber (100) as described in any one of claims 1 to 8, or the temperature measuring optical fiber (100) manufactured by the method for manufacturing a temperature measuring optical fiber as described in claim 9; The demodulation module (202) is configured to acquire an optical signal output by the temperature measurement optical fiber (100) and perform demodulation according to the optical signal.

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