Optical fiber sensor based on viscous metal film as well as preparation method and application method of optical fiber sensor

Abstract

The invention discloses an optical fiber sensor based on a viscous metal film as well as a preparation method and an application method. The optical fiber sensor comprises a single-mode optical fiber, a hollow optical fiber and the viscous metal film, the single-mode optical fiber and the hollow optical fiber are welded to form a first reflection interface; the viscous metal film is attached to the tail end of the hollow optical fiber to form a second reflection interface; a hollow cavity filled with air is formed between the first reflection interface and the second reflection interface to form an optical cavity. An optical signal is injected into the optical cavity through the single-mode optical fiber and is reflected for multiple times between the first reflection interface and the second reflection interface to generate an interference signal; the interference signal comprises resonance wavelength or envelope drift information and is used for representing the change of the external environment. According to the technical scheme, core connection can be completed only through one-time welding, the problems of interface deformation and loss caused by multiple-time welding are remarkably reduced, and therefore the structural stability and measurement consistency of a system are improved; and the method has good universality and expandability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronics, in particular to a fiber sensor based on a viscous metal film and a preparation method and an application method. BACKGROUND

[0002] With the development of modern optical communication and photonics, the research on miniature fiber devices and optical microcavity structures continues to deepen. Reflective fiber microcavity (such as Fabry-Pérot type microcavity) devices have a wide range of applications in fiber sensing, miniature lasers, interference measurement, and other fields due to their compact structure, high sensitivity, and ease of integration. FPI sensors use the interference effect of light waves between two mirrors to measure the change in the relative position of the mirrors to obtain information about the physical quantity being measured. This interference effect makes FPI sensors have excellent sensitivity and accuracy.

[0003] However, existing FPI sensors usually rely on high-cost film pieces or film materials such as gold films. These materials require complex technical means and process flow when plated on the end face of the optical fiber, such as evaporation plating or sputtering technology, which makes the preparation process of the optical microcavity cumbersome and costly. In addition, traditional FPI sensors are mostly used for the measurement of a single physical quantity (such as temperature or pressure), although some research has explored the measurement of different parameters, but the existing technology still cannot accurately measure multiple physical quantities. For example, the patent with application number 202210344455.X proposes a vernier-enhanced fiber pressure sensor and its preparation method combined with plating technology, but the patent needs to first dip the optical fiber into the graphene oxide solution to obtain a graphene oxide film, and then use ion sputtering to plate a gold film on the graphene oxide film. Such a manufacturing method not only has a complex process, but also uses high-cost materials. Moreover, the sensor can only sense a single parameter of gas pressure.

[0004] Therefore, there is a need for a technical solution to solve the problems of complex preparation process, high cost, and inability to measure multiple physical quantities of existing FPI sensors. SUMMARY

[0005] To achieve the above-mentioned purpose, the present application provides a fiber sensor based on a viscous metal film, comprising: a single-mode optical fiber, a hollow optical fiber, and a viscous metal film. Wherein the single-mode optical fiber and the hollow optical fiber are fused to form a first reflection interface; the viscous metal film is attached to the tail end of the hollow optical fiber to form a second reflection interface; and the first reflection interface and the second reflection interface form a hollow cavity filled with air to constitute an optical cavity.

[0006] The hollow optical fiber includes, but is not limited to, a hollow optical fiber, a capillary optical fiber or other hollow structure type optical fiber; the inner diameter and length of the hollow optical fiber are determined according to the target application requirement of the sensor. The adhesive metal film has a reflection function, and the material support includes, but is not limited to, an aluminum foil, a copper foil or other adhesive metal film materials with a reflection function.

[0007] The application also provides a preparation method of the optical fiber sensor based on the adhesive metal film, for preparing the optical fiber sensor provided by the application, and includes the following steps: The surfaces of the hollow optical fiber and the single-mode optical fiber are cleaned, and the end faces of the hollow optical fiber and the single-mode optical fiber are cut flat; One end face of the single-mode optical fiber cut flat is fused with one end face of the hollow optical fiber cut flat to form a first reflection interface; The adhesive metal film is attached to the other end face of the hollow optical fiber to form a second reflection interface; The first reflection interface and the second reflection interface are filled with air to form an optical cavity.

[0008] The cleaning of the surfaces of the hollow optical fiber and the single-mode optical fiber includes: stripping the coating layer of the hollow optical fiber and the single-mode optical fiber, and repeatedly wiping the fiber surface stripped of the coating layer with alcohol with a dust-free paper.

[0009] The attachment of the adhesive metal film to the other end face of the hollow optical fiber includes the following steps: An annular rubber ring is arranged on one side of the adhesive metal film; The adhesive metal film is precisely attached to the end face of the optical fiber by negative pressure adsorption, so that the annular rubber ring is attached to the hollow optical fiber; The sleeve is advanced to cover the outer ring of the adhesive metal film, so that the front end of the sleeve uniformly presses the outer ring of the adhesive metal film; The excess outer ring of the adhesive metal film is cut off along the outer edge of the sleeve under a microscope using a cutting device, so as to ensure that the adhesive metal film is completely attached to the end face of the optical fiber.

[0010] When it is ensured that the adhesive metal film is completely attached to the end face of the optical fiber, the adhesive metal film and the end face of the optical fiber have the same size, and the air cavity has a closed and airtight feature.

[0011] On the other hand, the application also provides an application method of the optical fiber sensor based on the adhesive metal film, which is realized based on the optical fiber sensor provided by the application, and includes the following steps: The optical fiber sensor is connected with a light source, and a response light signal is obtained; The light signal is injected into the optical cavity through the single-mode optical fiber, multiple reflections occur between the first reflection interface and the second reflection interface, and an interference signal is generated; the interference signal includes resonance wavelength or envelope drift information, and is used to represent the change of an external environment; Wherein, the distance between the first reflection interface and the second reflection interface is defined as the cavity length, when the cavity length changes or the medium refractive index changes with the external physical disturbance, the interference fringes produce drift.

[0012] Wherein, the relationship between the cavity length and the interference performance is quantified by FSR: under the condition that other conditions remain unchanged, the shorter the cavity length, the larger the FSR, and the wider the fringe interval; when the cavity length increases, the FSR gradually decreases.

[0013] Further, constructing two interference paths with a small difference in cavity length to amplify the response sensitivity of the cavity length disturbance, including: regarding the first reflection interface as the first cavity and the second reflection interface as the second cavity, when the free spectral ranges of the two cavities are slightly different, periodic envelope fringes appear in the composite interference fringes, realizing sensitive response to small cavity length changes.

[0014] Further, the fiber sensor can realize temperature sensitivity test and pressure sensitivity test, and the adhesive metal film responds to the changes of temperature and pressure; Wherein, the temperature sensitivity test refers to disconnecting the air pressure control device, adjusting the ambient temperature through the temperature control platform, changing the cavity length to realize the temperature sensitivity test; The pressure sensitivity test refers to maintaining the constant ambient temperature, adjusting the air pressure control device to apply different air pressures to the second reflection interface to realize the test of the pressure parameter.

[0015] The adhesive metal film used in the application reduces the cost and simplifies the overall preparation process, and the prepared FPI sensor can also utilize the effects of temperature and pressure on the length of the cavity, so as to realize the separate measurement of temperature and pressure through the changes of the interference signal. The sensing structure of the FPI composed of the adhesive metal film has significant advantages in reducing cost and simplifying preparation process, and can realize the separate measurement of temperature and pressure. The innovation of the technology makes the fiber sensor have broad application prospects in the field of multi-physical quantity measurement, and provides a new direction for the development of fiber sensing, micro sensor and high-precision measurement technology. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of the fiber sensor structure based on the adhesive metal film according to the embodiment of the application; Figure 2 is a schematic diagram of the micro resonant cavity constructed by the fiber sensor according to the embodiment of the application; Figure 3 is a schematic diagram of the temperature sensitivity test system according to the embodiment of the application; Figure 4 is a schematic diagram of the air pressure sensitivity test system according to the embodiment of the application; Reference numerals: 1-Hollow optical fiber; 2-Single-mode optical fiber; 3-Adhesive metal film; 4-Optical cavity; 5-First reflective interface; 6-Second reflective interface. Detailed Implementation

[0017] This invention proposes a fiber optic sensor based on an adhesive metal thin film and its fabrication method. It combines single-mode fiber, hollow fiber (such as hollow-core fiber, capillary, or other types of hollow fiber), and an adhesive metal thin film to form a highly sensitive, low-cost FPI fiber optic sensor. First, by precisely fusion splicing the single-mode fiber and the hollow fiber, efficient optical transmission and mode matching are achieved, ensuring the sensor has excellent signal transmission performance. Compared to traditional multi-segment fusion structures, this invention requires only one fusion to complete the core connection, significantly reducing interface deformation and loss problems caused by multiple fusions, thereby improving the system's structural stability and measurement consistency. Second, an annular adhesive ring is placed on the metal thin film. Negative pressure is used to precisely adhere the adhesive ring to the fiber end face, and a sleeve is used to uniformly press the outer ring of the film. This structure is simple in design, easy to fabricate, and has low overall cost, while also possessing good versatility and scalability.

[0018] The specific implementation of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] This invention provides an optical fiber sensor based on an adhesive metal thin film, the structure of which is as follows: Figure 1 As shown, it includes: single-mode optical fiber 2, hollow optical fiber 1, and adhesive metal thin film 3; Among them, hollow optical fiber 1 includes hollow optical fiber, capillary optical fiber or other hollow structure type optical fiber; the inner diameter and length of hollow optical fiber 1 are determined according to the target application requirements of the sensor in order to improve the sensitivity of the sensor. Adhesive metal films 3 include, but are not limited to, aluminum foil, copper foil, or other reflective adhesive metal film materials, used to respond to changes in external temperature and pressure. Using such adhesive metal film materials can effectively reduce the manufacturing cost of film materials while ensuring stable optical performance; In this configuration, single-mode fiber 2 and hollow fiber 1 are fused together to form a first reflective interface 5. The first reflective interface 5 is a stable optical interface, formed by fusion splicing the single-mode fiber 2 and hollow fiber 1 after cutting their ends flat. This method of formation enables efficient optical transmission and mode matching, ensuring that the sensor has good signal transmission performance and generates interference signals. An adhesive metal film 3 is attached to the tail end of the hollow optical fiber 1 to form a second reflective interface 6; an air-filled hollow cavity is formed between the first reflective interface 5 and the second reflective interface 6 to form an optical cavity 4, which is susceptible to external environmental influences; the adhesive metal film material forming the second reflective interface 6 can achieve a high reflectivity and can also effectively improve the sharpness of interference fringes while simplifying the structure.

[0020] On the other hand, the present invention provides a method for fabricating an optical fiber sensor based on a viscous metal thin film, used to prepare such a sensor. Figure 1 The fiber optic sensor shown includes the following steps: 1) Clean the surfaces of hollow fiber 1 and single-mode fiber 2, and cut the end faces of hollow fiber 1 and single-mode fiber 2 flat. Cleaning the surfaces of hollow fiber 1 and single-mode fiber 2 includes: stripping the coating layer from hollow fiber 1 and single-mode fiber 2, and repeatedly wiping the surface of the fiber with the stripped coating layer using lint-free paper soaked in alcohol.

[0021] 2) Cut one end face of the single-mode fiber 2 flat and fuse it with one end face of the hollow fiber 1 to form the first reflection interface 5; 3) Attach the adhesive metal film 3 to the other end face of the hollow optical fiber 1 to form a second reflective interface 6; the specific requirements include the following steps: An annular adhesive ring is provided on one side of the adhesive metal film 3; The adhesive metal film 3 is precisely bonded to the end face of the optical fiber by negative pressure adsorption, so that the ring adhesive ring is bonded to the hollow optical fiber 1. The sleeve is advanced to the position covering the outer ring of the adhesive metal film 3, so that the front end of the sleeve presses evenly against the outer ring of the adhesive metal film 3; Under a microscope, a cutting device is used to cut off the excess outer ring of the adhesive metal film 3 along the outer edge of the sleeve to ensure that the adhesive metal film 3 is completely bonded to the fiber end face.

[0022] At this point, ensure that the adhesive metal film 3 is fully bonded to the fiber end face, that the adhesive metal film 3 and the fiber end face are the same size, and that the air cavity has a sealed and airtight feature to prevent external gas exchange or cavity air pressure leakage, thus ensuring the stability of the interference cavity length.

[0023] 4) An optical cavity 4 is formed between the first reflective interface 5 and the second reflective interface 6.

[0024] This invention also provides methods for applying fiber optic sensors: When the fiber optic sensor responds to an optical signal, the optical signal generated by the light source is injected into the optical cavity 4 through the single-mode fiber 2. Multiple reflections occur between the first reflection interface 5 and the second reflection interface 6, generating interference signals and forming a miniature resonant cavity. The interference signal includes resonant wavelength or envelope drift information, which is used to characterize changes in the external environment. For example, when the distance between the two reflecting surfaces (the cavity length of the optical cavity 4), the refractive index of the medium, etc., change with external physical disturbances (such as temperature and pressure), the optical path difference between different beams will change accordingly, and the interference fringes will drift accordingly.

[0025] Meanwhile, the relationship between the distance between two reflecting surfaces and the interference performance can be quantified by the Free Spectral Range (FSR): under the condition that other factors remain unchanged, the shorter the distance between the two reflecting surfaces, the larger the FSR and the wider the fringe spacing; while as the distance between the two reflecting surfaces increases, the FSR gradually decreases, which can be used to achieve higher wavelength resolution.

[0026] Furthermore, constructing two interference paths with slight differences in cavity length can amplify the response sensitivity to cavity length perturbations: considering the first reflection interface 5 as the first cavity and the second reflection interface 6 as the second cavity, when the free spectral ranges of the two are slightly different, periodic envelope fringes will appear in the composite interference fringes. Even if the interference fringes form a periodic envelope, the response to small cavity length changes can be amplified, significantly improving the response sensitivity of the interference fringes in the reflection spectrum to cavity length perturbations.

[0027] The fiber optic sensor provided by this invention can realize temperature sensitivity testing and pressure sensitivity testing, responding to changes in temperature and pressure through an adhesive metal thin film 3. 1) Temperature change is achieved by placing an optical fiber sensor on a temperature control platform; the corresponding temperature sensitivity testing device structure is as follows: Figure 3 As shown, the temperature sensitivity test refers to: disconnecting the air pressure control device, adjusting the external temperature through the temperature control platform, and changing the length of the cavity to achieve the temperature sensitivity test.

[0028] 2) Pressure changes are controlled by a gas pressure device connected to a viscous metal film 3; the corresponding pressure sensitivity testing device structure is as follows: Figure 4 As shown, the pressure sensitivity test refers to maintaining a constant ambient temperature and applying different air pressures by adjusting the air pressure control device to act on the second reflective interface 6, thereby realizing the test of pressure parameters.

[0029] The present invention provides the following embodiments: Example 1 is an optical fiber sensor prepared by the preparation method provided by the present invention, such as... Figure 2As shown: A first reflective interface M1 (front-end optical reflective interface) is formed by a single-mode fiber 2 and a hollow fiber 1 (capillary fiber in this embodiment). A layer of highly reflective adhesive metal film (adhesive aluminum foil in this embodiment) is attached to the other side of the capillary fiber to form a first reflective interface M2 (rear-end reflective surface). An air-filled hollow cavity is formed between the two, thereby constructing a micro resonant cavity. The optical path is as follows: Figure 2 As shown: The amplitude of the incident beam from the light source is E in The first reflecting interface is M1, and the second reflecting interface is M2. The amplitudes of the reflected light generated by M1 and M2 when incident back into the single-mode fiber 2 are E1 and E2, respectively, which can be expressed as: , , Where R1 is the reflectivity of reflecting surface M1, and R2 is the reflectivity of reflecting surface M2. This represents the transmission loss in the microcavity.

[0030] When the reflected beam enters the single-mode fiber 2 at the left end and interferes with each other, the total interference intensity... for: ,in, This represents a one-way phase shift from M1 to M2; The microcavity refractive index n1, cavity length L1, and incident light wavelength are related to the microcavity refractive index n1, cavity length L1, and incident light wavelength. The following relationship must be satisfied: When the distance between each reflecting surface and the refractive index of the medium change with external physical disturbances (such as temperature and pressure), the optical path difference between different beams will change accordingly, and the interference fringes will drift accordingly.

[0031] To further quantify the relationship between cavity length and interference performance, this invention introduces the Free Spectral Range (FSR) as a measure of spectral fringe periodicity, expressed as follows: As can be seen, with other parameters remaining constant, the shorter the cavity length, the larger the FSR and the wider the stripe spacing; while as the cavity length increases, the FSR gradually decreases, which can be used to achieve higher wavelength resolution.

[0032] The present invention also introduces the "vernier effect" mechanism, which constructs two interference paths with slight differences in cavity length, so that the interference fringes form a periodic envelope, thereby amplifying the response to minute changes in cavity length.

[0033] Specifically, the reflection interface between the single-mode fiber 2 and the capillary is considered as the first cavity (FPI1), and the reflection interface between the capillary end and the aluminum foil is considered as the second cavity (FPI2). When the free spectral ranges FSR1 and FSR2 of the two are slightly different, periodic envelope fringes will appear in the composite interference fringes, and their envelope period can be expressed as: .

[0034] This mechanism significantly improves the sensitivity of the interference fringes in the reflection spectrum to cavity length perturbations. Compared to single-fringe drift measurement, envelope spectral drift responds more dramatically to perturbation changes, resulting in an order-of-magnitude increase in sensitivity. Furthermore, the temperature sensitivity S can be defined based on the envelope drift function in the FPI spectrum. T and air pressure sensitivity S P The relationship between sensor sensitivity and FPI parameters is shown in the following equation: , among which, S X Can represent S T or S P , λ peak λ is the wavelength of the envelope resonance peak.

[0035] According to the formula, the thermal expansion of the FPI caused by heating results in a red shift in the spectrum, while the shortening of the FPI caused by increased air pressure results in a blue shift. Simultaneously, to improve the sharpness and resolution of the interference fringes, the relationship between the cavity's finesse and full width at half maximum (FWHM) must be considered. , , where R is the reflectivity of the reflecting surface.

[0036] This invention uses an aluminum film as the end reflective interface, which achieves high reflectivity, thereby effectively improving the sharpness of interference fringes while simplifying the structure. Furthermore, the relationship between the quality factor (Q) and the full width at half maximum (FWHM) is as follows: ; As shown in the formula, a higher Q value indicates a narrower interference spectrum, resulting in higher wavelength selectivity and sensing accuracy of the system. The adhesive aluminum film used in this invention has high reflectivity, which significantly improves the Q value of the cavity, enabling the device to possess high frequency selectivity and spectral resolution.

[0037] Example 2 describes the construction of an optical fiber sensing system: Based on the theoretical design and parameter optimization of the resonant cavity, this invention further realizes a Fabry–Pérot optical fiber interference structure that is compact, has high optical coupling efficiency, and good stability.

[0038] In this embodiment, a precision fusion splicing process is used to coaxially connect single-mode fiber 2 and capillary fiber 2, forming the first optical reflection interface. The reflection mechanism originates from Fresnel reflection caused by the abrupt change in refractive index between the end face of single-mode fiber 2 and air. According to Fresnel reflection theory, when incident light waves enter a medium with a refractive index of r2 from a medium with a refractive index of r1, their reflectivity can be calculated by the following formula: Simultaneously, by optimizing splicing parameters (such as arc intensity, duration, and axial alignment accuracy), optical loss and joint distortion are minimized, thereby ensuring the stability of the interference signal and the repeatability of the system. The capillary fiber section provides physical support for the cavity structure, and its inner cavity creates conditions for the subsequent construction of the air cavity. At the other end of the capillary fiber, a surface-treated high-reflectivity adhesive metal film (such as an aluminum film) is selected. The adhesive metal film 3 is bonded to the other end face of the capillary fiber using a negative pressure process. The adhesive metal film 3 has a pre-cut annular adhesive film, the size of which is consistent with the end face size of the capillary fiber. After ensuring that the adhesive metal film 3 is properly positioned, the sleeve is pushed in to uniformly press the outer ring of the film. Then, under a microscope, a cutting device is used to cut off the excess outer ring of the film along the outer edge of the sleeve to ensure that the size of the adhesive metal film 3 is completely consistent with the end face of the fiber. This film layer can form the second reflective interface 6 without coating equipment or high-temperature treatment, significantly reducing the device manufacturing threshold, while possessing excellent reflective characteristics. The space between the two reflective interfaces is filled with air to form an interference cavity with stable optical path and easy control. Its length is mainly determined by the physical length of the capillary optical fiber.

[0039] The structure of the embodiment is as follows Figure 3 and Figure 4 As shown: The light source uses an ASE light source. The signal is injected into the FPI cavity via a single-mode fiber and a circulator. The reflected light returns via the original fiber and enters the spectrometer through the circulator, achieving precise tracking of the interference fringes. The sensor can be placed on a temperature control platform or connected to a gas pressure device to achieve independent control of both temperature and pressure parameters. Temperature disturbances mainly affect the air cavity length through material thermal expansion, while gas pressure changes cause diaphragm deformation, thus altering the optical path length. Both will cause drift in the position of the interference spectral fringes or the envelope structure. This system achieves optical path continuity and structural stability while effectively reducing manufacturing complexity and system cost, demonstrating promising practical applications.

[0040] Example 3, based on Examples 1 and 2, demonstrates the fabrication of a sensor and tests its temperature and pressure sensing performance using a standard temperature control platform and a gas pressure device. Since the air within the cavity is sensitive to both temperature and pressure disturbances, changes in cavity length cause spectral shifts. By acquiring the reflectance spectrum curve using a spectrometer, linear response monitoring of external physical parameters can be achieved.

[0041] First, the temperature disturbance was tested. The structure of the temperature sensitivity testing system is as follows: Figure 3 As shown, the sensor was fixed on a temperature-controlled platform without connecting a gas pressure device. The platform temperature was gradually increased, and the spectral drift trend with temperature changes was recorded. Due to the thermal expansion effect of air and the thermal response of the encapsulation structure caused by the temperature increase, the cavity length increased accordingly, resulting in a redshift in the spectrum. The temperature sensitivity coefficient can be obtained by linear fitting of the resonance peak of the interference spectrum. At the same time, the linear correlation between the peak shift and temperature can be analyzed to verify the linear response characteristics of the sensor in the target temperature range.

[0042] Subsequently, the air pressure response was tested, and the structure of the air pressure sensitivity testing system is as follows: Figure 4 As shown, under isothermal conditions, the sensor is connected to a gas pressure device, and the gas pressure is gradually increased. The gas pressure acts on the terminal metal membrane, causing it to deform and thus altering the cavity length. This change is reflected in a blue shift in the spectrum, and the shift trend exhibits good linearity.

[0043] It is worth noting that, due to the typical vernier effect in the cavity structure design, the envelope spectrum shifts significantly towards longer wavelengths as temperature increases. Conversely, with increasing air pressure, the envelope spectrum drifts linearly towards shorter wavelengths. This vernier effect significantly amplifies the sensor's response to minute disturbances, thus achieving high-sensitivity sensing performance without the need for complex cascaded structures.

[0044] This invention achieves a simple, highly sensitive, and low-cost fiber optic FPI sensing system by combining a single-mode fiber 2, a hollow fiber 1 (such as a hollow-core fiber, capillary, or other hollow-structure type), and an adhesive metal thin film 3. Through ingenious fiber structure design, this system effectively reduces problems caused by multiple fusion splices, ensuring the stability and consistency of the fiber connection. Furthermore, the fiber optic sensor of this invention can measure both temperature and pressure separately, and possesses high sensitivity, enabling rapid response to minute changes, making it suitable for precision measurement applications. Compared to traditional fiber optic sensing technologies, the innovative design of this invention not only reduces the overall system cost but also improves the system's stability and durability. This technology can be widely applied in various fields such as high-precision sensors, communication systems, and industrial automation.

[0045] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the present invention is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An optical fiber sensor based on a thin film of a viscous metal, characterized in that, It comprises: a single-mode optical fiber (2), a hollow optical fiber (1) and a viscous metal film (3); wherein the single-mode optical fiber (2) and the hollow optical fiber (1) are fused to form a first reflective interface (5); the viscous metal film (3) is attached to the tail end of the hollow optical fiber (1) to form a second reflective interface (6); and the first reflective interface (5) and the second reflective interface (6) form a hollow cavity filled with air to constitute an optical cavity (4).

2. The fiber optic sensor of claim 1, wherein, The hollow optical fiber (1) is a hollow structure type optical fiber, including a hollow core optical fiber or a capillary optical fiber; the inner diameter and length of the hollow optical fiber (1) are determined according to the target application requirements of the sensor; The viscous metal film (3) is a viscous metal film material with reflection function, including aluminum foil or copper foil.

3. A method of manufacturing an optical fiber sensor based on a thin film of viscous metal, characterized in that, A method for preparing the optical fiber sensor as claimed in claims 1-2, comprising the following steps: cleaning the surface of the hollow optical fiber (1) and the single-mode optical fiber (2), and cutting the end face of the hollow optical fiber (1) and the single-mode optical fiber (2) to be flat; fusing the cut flat end face of the single-mode optical fiber (2) to the cut flat end face of the hollow optical fiber (1) to form a first reflective interface (5); attaching the viscous metal film (3) to the other end face of the hollow optical fiber (1) to form a second reflective interface (6); filling the first reflective interface (5) and the second reflective interface (6) with air to form an optical cavity (4).

4. The method of claim 3, wherein the optical fiber sensor is prepared by the steps of: The cleaning of the surface of the hollow optical fiber (1) and the single-mode optical fiber (2) comprises: stripping the coating layer of the hollow optical fiber (1) and the single-mode optical fiber (2), and repeatedly wiping the fiber surface with alcohol with a dust-free paper.

5. The method of claim 3, wherein the step of applying the coating is performed by a process selected from the group consisting of: dip coating, spin coating, spray coating, and combinations thereof. The attachment of the viscous metal film (3) to the other end face of the hollow optical fiber (1) comprises the following steps: setting a ring-shaped rubber ring on one side of the viscous metal film (3); precisely attaching the viscous metal film (3) to the end face of the fiber by negative pressure adsorption, so that the ring-shaped rubber ring is attached to the hollow optical fiber (1); using a sleeve to advance to a position covering the outer ring of the viscous metal film (3), so that the front end of the sleeve uniformly presses the outer ring of the viscous metal film (3); under a microscope, using a cutting device to cut off the excess outer ring of the viscous metal film (3) along the outer edge of the sleeve, to ensure that the viscous metal film (3) is completely attached to the end face of the fiber.

6. The method of claim 5, wherein the optical fiber sensor is prepared by the steps of: When the viscous metal film (3) is completely attached to the end face of the fiber, the viscous metal film (3) and the fiber end face are the same size, and the air cavity (4) has a closed airtight feature.

7. A method of using a fiber optic sensor based on a thin film of viscous metal, characterized by, Based on the optical fiber sensor as claimed in claims 1-2, an implementation comprises: the optical fiber sensor is connected with a light source, and responds to a light signal; the light signal is injected into the optical cavity (4) through the single-mode optical fiber (2), multiple reflections occur between the first reflective interface (5) and the second reflective interface (6), and an interference signal is generated; the interference signal includes resonance wavelength or envelope drift information, which is used to represent the change of the external environment; Wherein, the distance between the first reflective interface (5) and the second reflective interface (6) is defined as the cavity length; when the cavity length changes or the medium refractive index changes with the external physical disturbance, the interference fringes produce drift.

8. The method of using a fiber optic sensor according to claim 7, wherein, The relationship between the cavity length and the interference performance is quantified by FSR: under the condition that other conditions remain unchanged, the shorter the cavity length, the larger the FSR, and the wider the fringe spacing; when the cavity length increases, the FSR gradually decreases.

9. The method of using a fiber optic sensor according to claim 7, wherein, Constructing two interference paths with a small difference in cavity length to amplify the response sensitivity of the cavity length disturbance, including: regarding the first reflective interface (5) as the first cavity and the second reflective interface (6) as the second cavity, when the free spectral range of the two is slightly different, periodic envelope fringes appear in the composite interference fringes, realizing the sensitive response to the small cavity length change.

10. The method of using a fiber optic sensor according to claim 7, wherein, The optical fiber sensor can realize temperature sensitivity test and pressure sensitivity test, and respond to the change of temperature and pressure through the adhesive metal film; Wherein, the temperature sensitivity test refers to disconnecting the air pressure control device, adjusting the external temperature through the temperature control platform, changing the cavity length to realize the temperature sensitivity test; The pressure sensitivity test refers to maintaining the constant environmental temperature, adjusting the air pressure control device to apply different air pressures to the second reflective interface to realize the test of the pressure parameter.

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