High-temperature optical fiber sensor and manufacturing method

Abstract

The invention discloses a high-temperature optical fiber sensor and a manufacturing method in the field of sensors, and the high-temperature optical fiber sensor comprises a single-mode optical fiber, a plurality of SiO2 microspheres are fixed at one end of the single-mode optical fiber, and the SiO2 microspheres are arranged along the optical signal transmission direction in the single-mode optical fiber; fusing one end of the single-mode optical fiber into SiO2 microspheres to form a plurality of first sensor assembly parts; wherein the maximum light intensity of the first sensor assembly is greater than 80% of the maximum light intensity of the broadband light source; and connecting the SiO2 microspheres on the plurality of first sensor assembly parts along the optical signal transmission direction of the single-mode optical fiber to obtain the high-temperature optical fiber sensor. The microsphere structures are the excitation unit, the coupling unit and the sensing unit of the optical fiber sensor, the change of the phase difference of light is caused by the change of the difference of the effective refractive indexes of the fiber core and the cladding relative to the temperature, and the high-precision temperature measurement is realized.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a high-temperature optical fiber sensor and a manufacturing method thereof. Background Art

[0002] Optical fiber sensors have many advantages such as compact structure, strong resistance to external interference, and sensitive sensing signals. They are widely used in the field of sensing, such as temperature sensing, humidity sensing, strain sensing, lateral pressure sensing, refractive index sensing, etc. Among a series of optical fiber sensors, optical fiber Michelson interferometer sensors have their unique advantages. For example, compared with Mach-Zehnder interferometers, their interference structure is shorter and can achieve smaller sensing structures; compared with traditional sensors, they have higher sensitivity and real-time performance. Existing Michelson optical fiber interferometer sensors are used in the fields of refractive index and temperature. According to existing literature reports, some special structures can reach 4000nm / RIU for refractive index measurement. In the field of temperature sensing, the usual Michelson optical fiber interferometer sensors can reach tens of pm / ℃. The most direct way to make an optical fiber Michelson sensor is to use a single-mode optical fiber dislocation structure, and there are also structures such as cones or special optical fiber structures to excite the light mode into the cladding to achieve the purpose of Michelson interference. However, these structures have two defects. The first aspect is that the structural strength is too poor. For example, in structures such as thin cones, the diameter of the thinnest part of the optical fiber is only tens or even several microns, which is not conducive to practical applications. Although the use of special optical fiber structures solves this problem, special optical fibers are very expensive and not conducive to large-scale applications. There are also literature on the use of optical fiber Michelson sensors in the field of high temperature measurement. In 2012, Wu Di and others designed a peanut structure in which the microspheres were regarded as a kind of optical coupler, and obtained a sensitivity of about 90pm / ℃. However, in this structure, the efficiency of optical coupling is not high and the sensitivity is also low. The most important problem is that the sensing length is nearly 3cm, which seriously affects the usability in the field of high temperature measurement.

[0003] The purpose of the present application is to provide a high-temperature optical fiber sensor and a self-fabrication method to solve the defects of the prior art sensors that are expensive and cannot meet the requirements of high-precision measurements.

[0004] In order to achieve the above objectives, this application is implemented by adopting the following technical solutions: In a first aspect, the present application discloses a high-temperature optical fiber sensor, which includes a single-mode optical fiber, and a plurality of SiO2 microspheres are fixed to one end of the single-mode optical fiber, and the plurality of SiO2 microspheres are arranged along the transmission direction of the optical signal in the single-mode optical fiber.

[0005] According to a further solution of the present application, the centers of several SiO2 microspheres are on the same horizontal line, and the line connecting the centers of several of the microspheres is colinear with the axis of the single-mode optical fiber.

[0006] In a further solution of the present application, the diameters of the connecting surfaces of adjacent SiO2 microspheres are equal.

[0007] In a further embodiment of the present application, the diameter of the SiO2 microspheres is 150 um to 250 um.

[0008] In a second aspect, the present application discloses a method for manufacturing the above-mentioned high-temperature optical fiber sensor, which comprises: Obtain a single-mode optical fiber, and melt one end of the single-mode optical fiber into SiO2 microspheres to form a plurality of first sensor assemblies; wherein the maximum light intensity of the first sensor assembly is greater than 80% of the maximum light intensity of the broadband light source; A plurality of SiO2 microspheres on the first sensor assembly are connected along the optical signal transmission direction of the single-mode optical fiber to obtain a high-temperature optical fiber sensor.

[0009] In a further embodiment of the present application, the connection of the SiO2 microspheres is a melting connection, and the melting process includes: Obtain a single-mode optical fiber, and melt it into SiO2 microspheres through discharge through a device to form a first sensor assembly; Arrange two SiO2 microspheres on the first sensor assembly opposite to each other and connect them by discharging and melting them through a device to form a double-sphere structure; Processing the curved surface of the SiO2 microsphere at one end of the double-sphere structure to obtain a second sensor assembly; Arrange the SiO2 microspheres at the ends of the two second sensor assemblies opposite to each other, and connect them by discharging and melting them through a device to obtain a four-sphere structure; The SiO2 microsphere at one end of the four-sphere structure is subjected to curved surface processing to obtain a high-temperature optical fiber sensor.

[0010] According to a further solution of the present application, the SiO2 microspheres are formed by a fiber fusion splicer. During the melting and forming stage of the SiO2 microspheres, the discharge power of the fiber fusion splicer is +80 bits and the discharge time is 2000 ms.

[0011] According to a further solution of the present application, during the SiO2 microsphere connection stage, the discharge intensity of the optical fiber fusion splicer is -20bit and the discharge time is 1000ms.

[0012] The beneficial effects of this application are: In this application, multiple microsphere structures are used as the excitation unit, coupling unit and sensing unit of the optical fiber sensor. The difference in the effective refractive index between the optical fiber core and the cladding changes with respect to the temperature, resulting in a change in the phase difference of the light. In actual experiments, this change can be observed on a spectrometer to achieve high-precision temperature measurement. This can be achieved using only single-mode optical fiber, which is low-cost. At the same time, the microsphere structure itself has a very high strength, which enhances the robustness of the system. The structure manufacturing process is simple, with good repeatability, and can be used for large-scale production.

[0013] Among them, the optical fiber fusion splicer adjusted the appropriate discharge intensity and discharge time during the SiO2 microsphere melting and forming stage and the SiO2 microsphere connection stage to ensure the smooth formation and connection of the SiO2 microspheres. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of single-mode optical fiber processing in Example 2 of the present application; Figure 2 This is a schematic diagram of the structure of the first sensor assembly in the second embodiment of the present application; Figure 3 This is a schematic diagram of the first sensor assembly during processing in the second embodiment of the present application; Figure 4 This is a schematic diagram of the structure of the double-ball structure in Example 2 of the present application; Figure 5 This is a schematic diagram of the second sensor assembly during processing in the second embodiment of the present application; Figure 6 This is a schematic diagram of the structure of the four-ball structure in Example 2 of the present application; Figure 7 Structural diagram of embodiment 1 of the present application Figure 8 This is a schematic diagram of the experimental device of Example 1 of the present application.

[0015] Fig. 9 Line graph of temperature and sensing length for the sensor experiment for this application.

[0016] Among them: 1. Single-mode optical fiber; 2. SiO2 microspheres. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Example

[0018] like Figure 7 As shown, this embodiment discloses a high-temperature optical fiber sensor, which includes a single-mode optical fiber 1, one end of which is fixed with four SiO2 microspheres 2, and the four SiO2 microspheres 2 are arranged along the optical signal transmission direction of the single-mode optical fiber 1.

[0019] Among them, the centers of the four SiO2 microspheres 2 are on the same horizontal line, and the line connecting the four centers is collinear with the axis line of the single-mode optical fiber 1; the diameters of the connecting surfaces of adjacent SiO2 microspheres 2 are equal, which is set to 100 um here; usually the diameter of the SiO2 microsphere 2 is set to 150 um~250 um, and in this embodiment, the diameter of the SiO2 microsphere 2 is made to 200 um.

[0020] The sensor in this embodiment uses single-mode optical fiber 1 to achieve sensing, and has low manufacturing cost. The strength of the SiO2 microspheres on the low-cost fiber is very high, which is much greater than the strength of the fine cone structure of the single-mode optical fiber 1 offset Michelson sensor. Example

[0021] Reference Figures 1 to 7 , this embodiment discloses a method for manufacturing a high temperature optical fiber sensor in an embodiment, which comprises the following steps: obtaining a single-mode optical fiber 1, molding one end of the single-mode optical fiber 1 into a SiO2 microsphere 2, and forming a plurality of first sensor assemblies; wherein the maximum light intensity of the first sensor assembly is greater than 80% of the maximum light intensity of the broadband light source; A plurality of SiO2 microspheres 2 on the first sensor assembly are connected along the optical signal transmission direction of the single-mode optical fiber 1 to obtain a high-temperature optical fiber sensor.

[0022] In order to better illustrate the manufacturing process, the solution of the second embodiment is described in detail below in combination with detailed operation steps.

[0023] The high temperature optical fiber sensor in the first embodiment is manufactured and connected.

[0024] The preparation materials require single-mode optical fiber 1 (SMF-28, Corning), and the equipment required includes a fiber fusion splicer (80S, Fujikura), a spectrum analyzer (AQ6370D, Yokogawa, Optical Spectrum Analyzer, OSA), a broadband light source (Benchtop Broadband Source, BBS), a fiber cleaver (CKFC-1, CommKing), a fiber circulator (responsible for connecting the fiber optic sensor and the spectrum analyzer as well as the light source), a micro-displacement platform, a fiber optic clamp, and a microscope (used to observe the size).

[0025] 1) Reference Figure 1First, start the fiber fusion splicer, set the manual mode, put the single-mode fiber 1 to be processed into it, debug the discharge power of the equipment to +80bit, and the discharge time to 2000ms. Discharge at the cut end of this section of single-mode fiber 1. The single-mode fiber 1 will melt and melt into a sphere under the action of surface tension, that is, SiO2 microsphere 2; Figure 2 After multiple discharges, until the diameter of the microspheres reaches 200um (observed under a microscope), a first sensor assembly is formed, and two first sensor assemblies are prepared by the same operation; 2) If Figure 3 As shown. Connect two microsphere structures of the first sensor assembly, one to the broadband light source and the other to the spectrometer. Under the debugging of the optical fiber fusion splicer, adjust the upper and lower positions of the two SiO2 microspheres 2 until the maximum light intensity that can be seen on the spectrometer is greater than 80% of the maximum light intensity of the broadband light source. Otherwise, use step 1) to remake the first sensor assembly; after adjusting the position, set the discharge intensity to -20bit and the discharge time to 1000ms in the manual mode of the fusion splicer, as shown. Figure 4 As shown, manually push and then discharge until the diameter of the middle of the two balls is 100um, forming a double ball structure; use the same step 2) to prepare two double ball structures; use a fiber optic cutter to cut the ends of the double ball structure flat, and obtain a second sensor assembly.

[0026] 3) Reference Figure 5 As shown, the outer SiO2 microspheres 2 on the two second sensor assemblies are connected in a fiber fusion splicer to ensure the smoothness of the spherical surface. The manufacturing process of the double-sphere structure is specifically referred to to obtain a four-sphere structure.

[0027] 4) Reference Figure 6 , use a fiber optic cutting knife to cut the single-mode optical fiber 1 at one end of the four-ball structure, and ensure that the end of the four-ball structure is smooth to obtain a high-temperature optical fiber sensor. When cutting and melting and docking are required in the above steps, the processing object needs to be clamped and fixed by a micro-displacement platform and a fiber optic clamp.

[0028] Continue to observe the attached Figure 7 ; The left end is single-mode fiber 1, and the right end is a four-ball array structure. The optical signal is injected from the single-mode fiber 1. First, at the first micro-ball structure, the light beam is widened, and part of the light enters the medium composed entirely of cladding materials, while the other part of the light still propagates along the axial direction of the core. At the position of the last spherical surface, the light is reflected, and the axial light is reflected back along the axis. After the paraxial light beam is reflected, part of the light returns to the axial direction for transmission. Assuming that the intensity of the reflected light is I, I can be expressed as:

[0029] in I is the intensity of the interference light,I 1 is the intensity of the axial reflected light, I 2 is the intensity of the reflected light of the paraxial beam, It is the difference in effective refractive index between the different paths taken by the axial beam and the paraxial beam. L is the total distance travelled by the two reflected lights.

[0030] Then the wavelength shift can be described as:

[0031] In the formula, is the Nth coherent wavelength, N is a constant, and the derivative of the above formula with respect to temperature can be obtained: The larger the value, the more sensitive the sensor is to temperature detection.

[0032] Reference Figure 8 , the high temperature sensor made in Example 2 was tested; light was emitted from the light source, passed through the coupler, and entered a high temperature furnace with a temperature adjustment step of 1°C. The microstructure was placed in the high temperature furnace. The temperature in the high temperature furnace ranged from 50°C to 900°C, and the reflection intensity spectrum of the spectrometer was measured every 50°C. Fig. 9 It can be seen that the sensing length of the sensor in this application is very small.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "multiple" means two or more.

[0034] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

Claims

1. A high temperature optical fiber sensor, characterized in that: It comprises a single-mode optical fiber, one end of which is fixed with a plurality of SiO2 microspheres, and the plurality of SiO2 microspheres are arranged along the transmission direction of the optical signal in the single-mode optical fiber.

2. The high temperature optical fiber sensor according to claim 1, characterized in that: The centers of the SiO2 microspheres are on the same horizontal line, and the line connecting the centers of the microspheres is collinear with the axis of the single-mode optical fiber.

3. The high temperature optical fiber sensor according to claim 1, characterized in that: The diameters of the connecting surfaces of adjacent SiO2 microspheres are equal.

4. The high temperature optical fiber sensor according to claim 1, characterized in that: The diameter of the SiO2 microspheres is 150um~250um.

5. A method for manufacturing a high temperature optical fiber sensor according to any one of claims 1 to 4, characterized in that: include: Obtain a single-mode optical fiber, and mold SiO2 microspheres at one end of the single-mode optical fiber to form a plurality of first sensor assemblies; wherein the maximum light intensity of the first sensor assembly is greater than 80% of the maximum light intensity of the broadband light source; A plurality of SiO2 microspheres on the first sensor assembly are connected along the optical signal transmission direction of the single-mode optical fiber to obtain a high-temperature optical fiber sensor.

6. The method for manufacturing a high temperature optical fiber sensor according to claim 5, characterized in that: The connection of the SiO2 microspheres is a melting connection, and the melting process includes: Obtain a single-mode optical fiber, and melt it into SiO2 microspheres through discharge through a device to form a first sensor assembly; Arrange two SiO2 microspheres on the first sensor assembly opposite to each other and connect them by discharging and melting them through a device to form a double-sphere structure; Processing the curved surface of the SiO2 microsphere at one end of the double-sphere structure to obtain a second sensor assembly; Arrange the SiO2 microspheres at the ends of the two second sensor assemblies opposite to each other, and connect them by discharging and melting them through a device to obtain a four-sphere structure; The SiO2 microsphere at one end of the four-sphere structure is subjected to curved surface processing to obtain a high-temperature optical fiber sensor.

7. The method for manufacturing a high temperature optical fiber sensor according to claim 5, characterized in that: The SiO2 microspheres are formed by a fiber fusion splicer. During the melting and forming stage of the SiO2 microspheres, the discharge power of the fiber fusion splicer is +80 bits and the discharge time is 2000 ms.

8. The method for manufacturing a high temperature optical fiber sensor according to claim 5, characterized in that: During the SiO2 microsphere connection stage, the optical fiber fusion splicer has a discharge intensity of -20 bits and a discharge time of 1000 ms.

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