Optical fiber sensor

Abstract

The utility model relates to the technical field of sensors, in particular to an optical fiber sensor. The utility model aims to solve the problem that an existing sensor is insufficient in partial discharge detection sensitivity, and particularly provides an optical fiber sensor which comprises an optical fiber functional component, a first sensing film and a second sensing film which are sequentially arranged at intervals in the axial direction of the optical fiber sensor, the first sensing film is connected with the optical fiber functional component, and the second sensing film is connected with the optical fiber functional component. The second sensing film is connected with the first sensing film, the optical fiber functional component is provided with a smooth front end face, a first F-P resonant cavity is formed between the front end face of the optical fiber functional component and the first sensing film, and a second F-P resonant cavity is formed between the first sensing film and the second sensing film. According to the utility model, a phase superposition effect is generated on an interference spectrum based on a double F-P resonant cavity structure, the sensitivity of sensing ultrasonic waves is improved, external electromagnetic interference and mechanical vibration can be isolated to a certain extent, and the accuracy and reliability of signals are ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of sensors, and more specifically, to an optical fiber sensor. Background Art

[0002] Partial discharge is a common but potentially harmful phenomenon in the operation of power equipment. Therefore, effective online identification of partial discharge patterns is important for determining the degree of harm of partial discharge to transformers.

[0003] Traditional partial discharge detection technology usually uses piezoelectric sensors or resistive sensors to receive ultrasonic signals. Due to the physical structure and material properties of the sensor, its resolution and sensitivity are limited. In addition, traditional fiber optic sensors also have the following defects: 1. Limited working frequency range: usually designed to work within a specific frequency range, it cannot adapt well to the detection needs within different frequency ranges; 2. Insufficient environmental adaptability: greatly affected by environmental factors, such as changes in temperature, humidity, air pressure, etc., which may affect its detection performance and stability; 3. Size and weight limitations: the size and weight are usually large, which limits its use in some specific application scenarios, such as occasions that require miniaturization or lightweight; 4. Complex installation and maintenance: the structure and working principle are relatively complex, and the installation and maintenance process may be cumbersome, increasing the cost and difficulty of use; 5. Insufficient anti-interference ability: it may be interfered in a strong electromagnetic field or other interference environment, affecting its detection accuracy and reliability; 6. Low real-time performance: some traditional ultrasonic sensors require a certain amount of time to process signals, resulting in a slow response speed and inability to monitor abnormal conditions in real time.

[0004] In summary, the traditional partial discharge detection technology has the disadvantages of limited detection distance, low resolution, great influence of environmental interference and inability to realize online monitoring. In view of this, it is necessary to improve the existing optical fiber sensors to improve the accuracy, reliability and practicality of detection, so as to realize online monitoring and fault warning of power equipment. Utility Model Content

[0005] The utility model aims to overcome at least one defect of the above-mentioned prior art and provide an optical fiber sensor for solving the problem that the existing sensor has insufficient sensitivity to partial discharge detection.

[0006] The technical solution adopted by the utility model is to provide an optical fiber sensor, comprising an optical fiber functional component, a first sensing film, and a second sensing film which are sequentially spaced apart along the axial direction of the optical fiber sensor, wherein the first sensing film is connected to the optical fiber functional component, and the second sensing film is connected to the first sensing film, wherein the optical fiber functional component has a smooth front end surface, a first FP resonant cavity is formed between the front end surface of the optical fiber functional component and the first sensing film, and a second FP resonant cavity is formed between the first sensing film and the second sensing film.

[0007] In this solution, the optical fiber functional component can play the function of an optical fiber, that is, it is used to propagate the incident light signal. The interference spectra formed by the forward light wave of the incident light signal propagating in the two FP resonant cavities respectively produce a superposition effect, which in turn enhances the output end optical signal in the optical fiber functional component, thereby improving the detection sensitivity of the optical fiber sensor to ultrasound. When partial discharge occurs, the ultrasonic wave generated by the discharge senses the first sensing film and the second sensing film, causing the cavity lengths of the first FP resonant cavity and the second FP resonant cavity to change, which in turn causes the interference spectrum characteristics of the two FP resonant cavities to change. The multiple interference spectra generated by the dual FP resonant cavity structure have a phase superposition effect, which improves the significance of the change in spectral characteristics, that is, improves the sensitivity of the sensor device to perceive partial discharge signals, which is convenient for indirectly inferring the properties and parameters of the ultrasonic vibration signal by analyzing the changes in spectral characteristics. Finally, using an appropriate demodulation method, information related to the ultrasonic vibration signal can be obtained from the output optical signal.

[0008] Further, the medium in the first FP resonant cavity is air; and / or the medium in the second FP resonant cavity is air.

[0009] Furthermore, the first FP resonant cavity and the second FP resonant cavity are coaxially arranged.

[0010] Furthermore, the reflectivity of the first sensing film is 50-75%, and / or the reflectivity of the second sensing film is ≥90%.

[0011] Furthermore, the diameter of the optical fiber functional component is 100-200um.

[0012] Furthermore, the distance between the first sensing film and the front end surface of the optical fiber functional component is 50-110 nm.

[0013] In some embodiments, the first sensing film and the second sensing film are encapsulated in the front part of the optical fiber functional component via a packaging structure, the packaging structure has a hollow cavity penetrating its two end faces, the packaging structure sleeves the optical fiber functional component through the hollow cavity, and the front end face of the optical fiber functional component, the first sensing film, and the second sensing film are encapsulated in the hollow cavity at intervals front and back.

[0014] In this solution, the ultrasonic wave generated by the partial discharge causes elastic deformation of the first sensing film and the second sensing film, which in turn changes the length of the first FP resonant cavity and the second FP resonant cavity, resulting in changes in the interference spectrum characteristics of the first FP resonant cavity and the second FP resonant cavity. The multiple spectra generated by the dual FP resonant cavity structure have a phase superposition effect, which improves the significance of the change in the spectral characteristics, that is, improves the sensitivity of the sensing device to the partial discharge signal. In addition, the optical fiber functional component is encapsulated by the packaging structure to improve the connection strength between the sensing head component and the optical fiber functional component, and the hollow cavity structure can also play a certain role in limiting the first sensing film and the second sensing film in the radial direction, thereby improving the structural stability of the first FP resonant cavity and the second FP resonant cavity, which helps the optical fiber sensor maintain a high detection sensitivity to ultrasonic waves.

[0015] Furthermore, the packaging structure includes a first connecting tube, a second connecting tube and a third connecting tube which are connected in sequence along its own axial direction, the first connecting tube is sleeved on the front part of the optical fiber functional component, the front end part of the first connecting tube is used to support and set the first sensing membrane, the second connecting tube cover is set on the periphery of the first sensing membrane, the front end of the second connecting tube is used to support and set the second sensing membrane, and the third connecting tube cover is set on the periphery of the second sensing membrane.

[0016] This solution uses a packaging structure composed of a first connecting tube, a second connecting tube and a third connecting tube to facilitate arranging the front end face of the optical fiber functional component, the first sensing film and the second sensing film in a center-aligned manner in the hollow cavity of the connecting tube, thereby forming a first FP resonant cavity and a second FP resonant cavity that can work stably. In addition, the multiple connecting tube structure also facilitates encapsulating the front end face of the optical fiber functional component, the first sensing film and the second sensing film inside the packaging structure to provide protection.

[0017] Further, the first connecting tube is made of a capillary tube; and / or the second connecting tube is made of a capillary tube; and / or the third connecting tube is made of a capillary tube.

[0018] In some embodiments, the optical fiber functional component, the first sensing film and the second sensing film are integrally arranged, the optical fiber functional component and the first sensing film are connected via the first remaining portion of the optical fiber, and the first sensing film and the second sensing film are connected via the second remaining portion of the optical fiber.

[0019] The optical fiber sensor of this scheme can be realized based on a single-mode optical fiber. The optical fiber functional component is used to propagate the incident light signal. The first remaining part of the optical fiber is used to support and connect the first sensing film. The second remaining part of the optical fiber is used to support and connect the second sensing film. The front end face of the optical fiber functional component forms a first FP resonant cavity before the first sensing film, and the second FP resonant cavity is formed between the first sensing film and the second sensing film. The overall structure of the optical fiber sensor is simple, the volume is small, and the application range is wide. When partial discharge occurs, the ultrasonic wave generated by the discharge causes the first sensing film, the second sensing film, and the first remaining part of the optical fiber and the second remaining part of the optical fiber to undergo elastic deformation, which then changes the cavity length of the first FP resonant cavity and the second FP resonant cavity, resulting in changes in the interference spectrum characteristics of the first FP resonant cavity and the second FP resonant cavity. The multiple interference spectra generated by the dual FP resonant cavity structure have a phase superposition effect, which improves the significance of the change in spectral characteristics, that is, improves the sensitivity of the optical fiber sensor to perceive partial discharge signals, so as to facilitate the indirect inference of the properties and parameters of the ultrasonic vibration signal by analyzing the changes in spectral characteristics. Finally, by using an appropriate demodulation method, information related to the ultrasonic vibration signal can be obtained from the output optical signal to monitor the partial discharge phenomenon.

[0020] Compared with the prior art, the utility model has the following beneficial effects: (1) based on the dual sensing film structure, the thickness of the dual sensing film and the distance between the sensing film and the optical fiber head can be adjusted during the preparation process, thereby changing the reflection spectrum characteristics of the optical fiber sensor, thereby increasing the detection capability of long-distance signals and overcoming the problem of limited detection distance;

[0021] (2) The dual FP resonant cavity structure produces a phase superposition effect, which can isolate external electromagnetic interference and mechanical vibration to a certain extent, reduce the impact of these interferences on the sensor device, and ensure the accuracy and reliability of the signal;

[0022] (3) By analyzing the changes in spectral characteristics, the properties and parameters of the partial discharge signal can be indirectly inferred, which simplifies the processing of the complexity of the partial discharge signal;

[0023] (4) It has high sensitivity and can respond quickly to ultrasonic signals. By demodulating the output optical signal, it can monitor the ultrasonic vibration signal in the power equipment in real time.

[0024] (5) It has a small size and weight, low manufacturing cost, and is suitable for various power equipment monitoring scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural diagram of Example 1.

[0026] Figure 2 This is a structural breakdown diagram of Example 1.

[0027] Figure 3 These are cross-sectional views of some implementation methods of Example 1.

[0028] Figure 4 These are cross-sectional views of other implementations of Example 1.

[0029] Figure 5 This is a structural diagram of Example 2.

[0030] Figure 6 This is a cross-sectional view of Example 2.

[0031] Figure numerals: optical fiber functional component 100, optical fiber core 110, sensor head component 200, first sensor film 210, second sensor film 220, packaging structure 230, first connecting tube 231, second connecting tube 232, third connecting tube 233, first remaining portion of optical fiber 240, second remaining portion of optical fiber 250, first FP resonant cavity 300, second FP resonant cavity 400. DETAILED DESCRIPTION

[0032] The drawings of the present invention are only used for illustrative purposes and cannot be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0033] Example 1

[0034] like Figure 1-3 As shown, this embodiment provides a first optical fiber sensor, including an optical fiber functional component 100 and a sensing head component 200 connected in sequence along the reverse direction of the incident light source, the sensing head component includes a first sensing film 210, a second sensing film 220 and a packaging structure 230, the packaging structure 230 has a hollow cavity running through its two end faces, the packaging structure 230 is sleeved with the optical fiber functional component 100 through the hollow cavity, the front end face of the optical fiber functional component 100, the first sensing film 210, and the second sensing film 220 are packaged in the hollow cavity at intervals in front and back, a first FP resonant cavity 300 is formed between the front end face of the optical fiber functional component 100 and the first sensing film 210, and a second FP resonant cavity 400 is formed between the first sensing film 210 and the second sensing film 220.

[0035] During implementation, in order to reduce the complexity of the incident light wave signal, the optical fiber functional component 100 adopts a single-mode optical fiber. Specifically, the core 110 of the single-mode optical fiber is coaxial with the center of the first sensing film 210 and the second sensing film 220, thereby forming a first FP resonant cavity 300 and a second FP resonant cavity 400 that can work stably.

[0036] refer to Figure 2-4 The packaging structure 230 includes a first connecting tube 231, a second connecting tube 232, and a third connecting tube 233 which are sequentially connected along the axis thereof. The first connecting tube 231 is sleeved on the front part of the optical fiber functional component 100. The front end of the first connecting tube 231 is used to support and set the first sensing film 210. The second connecting tube 232 is covered on the periphery of the first sensing film 210. The front end of the second connecting tube 232 is used to support and set the second sensing film 220. The third connecting tube 233 is covered on the periphery of the second sensing film 220. In specific implementation, the first connecting tube 231, the second connecting tube 232, and the third connecting tube 233 can be obtained by using a capillary tube with a specific diameter length.

[0037] In some embodiments, the optical fiber functional component 100, the first connecting tube 231, the second connecting tube 232 and the third connecting tube 233 are connected in sequence in a nested manner. Specifically, refer to Figure 2-3 The inner diameter of the first connecting tube 231 is slightly larger than the outer diameter of the single-mode optical fiber, the inner diameter of the second connecting tube 232 is slightly larger than the outer diameter of the first connecting tube 231, and the inner diameter of the third connecting tube 233 is slightly larger than the outer diameter of the second connecting tube 232. The first sensing film 210 is attached to the front end surface of the first connecting tube 231, and the second sensing film 220 is attached to the front end surface of the second connecting tube 232. The second connecting tube 232 is sleeved on the first connecting tube 231 through its own hollow cavity. Similarly, the third connecting tube 233 is sleeved on the second connecting tube 232 through its own hollow cavity. Figure 3 As shown, the front end face of the optical fiber functional component 100, the first sensing film 210 and the second sensing film 220 are all encapsulated in the connection assembly composed of the first connecting tube 231, the second connecting tube 232 and the third connecting tube 233, referring to Figure 3, by sleeve-arranging the first connecting tube 231 on the front part of the single-mode optical fiber, an optical fiber sensor can be obtained. In a specific implementation, the first sensing film 210 and the second sensing film 220 can be set at the front end of the corresponding connecting tube by gluing. This embodiment can improve the structural strength of the packaging structure 230, and at the same time improve the connection stability between the sensing head component 200 and the optical fiber functional component 100. In a specific implementation, since the outer diameter of the single-mode optical fiber is usually 100-200um, and 125um is particularly common, in order to adapt to the single-mode optical fiber, the diameter of the first sensing film 210 can be set to 200-240um, and can be set to 220um specifically, and the diameter of the second sensing film 220 can be set to 280-320um, and can be set to 300um specifically. In this way, the overall structure of the optical fiber sensor can also be miniaturized.

[0038] In other embodiments, reference Figure 2 , 4 , only the first connecting tube 231 is nested on the optical fiber functional component 100, the rear end cross section of the second connecting tube 232 is closely attached to the front end cross section of the first connecting tube 231, and the rear end cross section of the third connecting tube 233 is closely attached to the front end cross section of the second connecting tube 232. In specific implementation, the fixing strength between the connecting tubes can be improved by applying adhesive. Similarly, in this embodiment, the first sensing film 210 is arranged on the front end surface of the first connecting tube 231, and the second sensing film 220 is arranged on the front end surface of the second connecting tube 232. It is easy to understand that the packaging of the sensing film can be realized by only making the inner diameter of the second connecting tube 232 slightly larger than the first sensing film 210 and the inner diameter of the third connecting tube 233 slightly larger than the second sensing film 220. Therefore, this embodiment can reduce the diameter size of the second connecting tube 232 and the third connecting tube 233, which is conducive to the miniaturization of the overall structure of the optical fiber sensor.

[0039] In a preferred embodiment, in order to facilitate analysis of the spectral signal of the first FP resonant cavity 300, the distance between the first sensing film 210 and the front end surface of the optical fiber functional component 100 is 50-110 nm, thereby facilitating monitoring of partial discharge signals of power equipment.

[0040] In some embodiments, in order to take into account the reflection and transmission performance of the FP resonant cavity, the first sensing film 210 is a polyimide reflective film. Specifically, the polyimide reflective film is formed by covering a metal surface film on the surface of a polyimide base film. Preferably, the metal surface film is an aluminum film.

[0041] Preferably, the reflectivity of the first sensing film 210 is 50%-75%; and / or, the reflectivity of the second sensing film 220 is ≥90%. This arrangement can ensure that a reverse wave of sufficient intensity is generated in the first FP resonant cavity 300 through the reflection effect of the first sensing film 210, thereby generating an interference spectrum that meets the requirements with the forward wave emitted by the optical fiber functional component 100, and can also ensure that the forward wave that passes through the first sensing film 210 and is emitted into the second FP resonant cavity 400 retains sufficient intensity, thereby also generating an interference spectrum that meets the requirements in the second FP resonant cavity 400.

[0042] Combination Figure 1-4 For understanding, the working principle of the optical fiber sensor of this embodiment is as follows: the forward light wave emitted by the single-mode optical fiber propagates in the first FP resonant cavity 300, and generates a first reverse light wave under the reflection of the first sensing film 210, and the first reverse light wave interferes with the forward light wave; at the same time, a part of the forward light wave emitted by the single-mode optical fiber propagates to the second FP resonant cavity 400 through the first sensing film 210, and then the forward light wave generates a second reverse light wave under the reflection of the second sensing film 220, and the forward light wave and the second reverse light wave also interfere with each other. When local discharge occurs, the ultrasonic wave generated by the discharge causes the first sensing film 210 and the second sensing film 220 to undergo elastic deformation. At this time, the physical properties of the first sensing film 210 and the second sensing film 220, such as the refractive index and thickness, change, and then change the cavity length of the first FP resonant cavity 300 and the second FP resonant cavity 400, thereby affecting the propagation and reflection of the light wave in the first FP resonant cavity 300 and the second FP resonant cavity 400. The aforementioned changes lead to changes in the interference spectral characteristics of the first FP resonant cavity 300 and the second FP resonant cavity 400. The multiple spectra generated by the dual FP resonant cavity structure have a phase superposition effect, which in turn enhances the significance of the changes in the spectral characteristics, that is, enhances the sensitivity of the optical fiber sensor to the ultrasonic waves emitted by local discharge, and facilitates the subsequent analysis of the changes in the spectral characteristics to indirectly infer the properties and parameters of the ultrasonic vibration signal. Finally, by using an appropriate demodulation method, information related to the ultrasonic vibration signal can be obtained from the output optical signal.

[0043] Example 2

[0044] like Figure 4-5As shown, this embodiment provides another optical fiber sensor. The optical fiber sensor of this embodiment uses a single-mode optical fiber as the main structure, and includes an optical fiber functional component 100, an optical fiber first remaining portion 240, a first sensing film 210, an optical fiber second remaining portion 250, and a first sensing film 220 connected in sequence along the axial direction of the single-mode optical fiber, wherein the front end face of the single-mode optical fiber main structure is the front end face of the first sensing film 220, a first FP resonant cavity 300 is formed between the front end face of the optical fiber functional component 100 and the first sensing film 210, and a second FP resonant cavity 400 is formed between the first sensing film 210 and the first sensing film 220. In specific implementation, the first FP resonant cavity 300 and the second FP resonant cavity 400 can be directly etched on the single-mode optical fiber by femtosecond laser etching, thereby obtaining the ultrasonic sensor of this embodiment.

[0045] It can be understood that the ultrasonic sensor of this embodiment can be realized based on a single-mode optical fiber, the optical fiber functional component 100 transmits the incident light signal, the first remaining part 240 of the optical fiber is used to support the first sensing film 210, and the second remaining part 250 of the optical fiber is used to support the first sensing film 220. The front end face of the optical fiber functional component 100 forms a first FP resonant cavity 300 between the first sensing film 210, and the second FP resonant cavity 400 is formed between the first sensing film 210 and the first sensing film 220. The forward wave of the incident light signal is transmitted and reflected by the first sensing film 210 and the first sensing film 220, and multiple interference spectrum signals are generated in the first FP resonant cavity 300 and the second FP resonant cavity 400. By connecting a demodulator to the output end of the ultrasonic sensor, the interference spectrum signal can be demodulated into information related to the ultrasonic vibration signal to monitor the partial discharge signal. In addition, the ultrasonic sensor of the utility model also has many advantages such as simple structure, small size, and wide application range.

[0046] Referring to the figure, in a specific implementation, in order to improve the interference spectrum signal measured by the ultrasonic sensor, the centers of the first FP resonant cavity 300 and the second FP resonant cavity 400 are coaxial, so that the light emitted by the optical fiber functional component 100 can be fully reflected and transmitted when passing through the first sensing film 210 and the first sensing film 220, which is helpful to measure a stable interference spectrum and improve the detection sensitivity of the ultrasonic sensor. Specifically, the medium in the first FP resonant cavity 300 is air, and the medium in the second FP resonant cavity 400 is air, which can ensure the normal operation of the dual FP resonant cavity, avoid additional packaging structures, and promote the miniaturization of single-mode optical fiber ultrasonic sensors.

[0047] refer to Figure 3Since the single-mode optical fiber is directly etched, the first sensing film 210 and the first sensing film 220 are both silicon dioxide reflective films. In addition, corresponding to the size of ordinary single-mode optical fiber, the diameter of the single-mode optical fiber specifically used is 100-200um, for example, 125um, so that the single-mode optical fiber ultrasonic sensor can achieve a miniaturized structure. In specific implementation, the diameters of the first sensing film 210 and the first sensing film 220 can be etched to be the same as the diameter of the single-mode optical fiber. On the one hand, additional radial etching processing of the first sensing film 210 and the first sensing film 220 can be avoided, thereby simplifying the manufacturing process. On the other hand, the front end face of the optical fiber functional component 100 with the same diameter, the first sensing film 210, and the first sensing film 220 can be easily aligned through the core 110 located on the central axis of the optical fiber functional component 100, thereby obtaining the coaxial and center-aligned first FP resonant cavity 300 and second FP resonant cavity 400.

[0048] In a preferred embodiment, the reflectivity of the first sensing film 210 is 50-75%, and the reflectivity of the first sensing film 220 is ≥90%. In this way, it can be ensured that a reverse wave of sufficient intensity is generated in the first FP resonant cavity 300 through the reflection effect of the first sensing film 210, thereby generating an interference spectrum that meets the requirements with the forward wave emitted by the optical fiber functional component 100, and the forward wave that passes through the first sensing film 210 and is emitted into the second FP resonant cavity 400 can retain sufficient intensity, thereby also generating an interference spectrum that meets the requirements in the second FP resonant cavity 400.

[0049] In order to fully sense the ultrasonic waves emitted by partial discharge while meeting the transmission and reflection requirements, the thickness of the first sensing film 210 and / or the first sensing film 220 of this embodiment is 10-25um. At this time, the first sensing film 210 and the first sensing film 220 can link the first remaining part 240 of the optical fiber and the second remaining part 250 of the optical fiber to undergo elastic deformation that meets the requirements during partial discharge, thereby causing the cavity lengths of the first FP resonant cavity 300 and the second FP to change, thereby causing the interference spectrum characteristics measured by the single-mode optical fiber ultrasonic sensor to change, and the ultrasonic signal can be obtained after demodulation. In addition, the thickness of the first sensing film 210 and the first sensing film 220 can change the resonant frequency and frequency response range of the ultrasonic sensor. Research has found that within this size range, it is more compatible with the detection of partial discharge ultrasonic waves.

[0050] In a preferred embodiment, the length of the first remaining portion 240 of the optical fiber is 50-110um; and / or, the length of the second remaining portion 250 of the optical fiber is 50-110um, the length of the first remaining portion 240 of the optical fiber is the cavity length of the first FP resonant cavity 300, and the length of the second remaining portion 250 of the optical fiber is the cavity length of the second FP resonant cavity 400, and the length directly affects the free spectral range (FSR) of the reflection spectrum of the ultrasonic sensor, the coherence depth and the insertion loss. Studies have found that within this size range, the interference spectrum is easier to analyze, which can improve the efficiency of measuring local discharge ultrasonic signals.

[0051] The working principle of the utility model is as follows: when local discharge occurs, the ultrasonic signal generated by the discharge causes the first sensing film 210, the first sensing film 220, the first remaining part 240 of the optical fiber, and the second remaining part 250 of the optical fiber to undergo elastic deformation, thereby changing the cavity length of the first FP resonant cavity 300 and the second FP resonant cavity 400, resulting in changes in the interference spectrum characteristics of the first FP resonant cavity 300 and the second FP resonant cavity 400. The multiple interference spectra generated by the dual FP resonant cavity structure have a phase superposition effect, which improves the significance of the change in spectral characteristics, that is, improves the sensitivity of the ultrasonic sensor to perceive local discharge signals, so as to facilitate the subsequent analysis of the changes in spectral characteristics to indirectly infer the properties and parameters of the ultrasonic vibration signal. Finally, by using an appropriate demodulation method, information related to the ultrasonic vibration signal can be obtained from the output optical signal.

[0052] Obviously, the above embodiments of the utility model are only examples for clearly explaining the technical solution of the utility model, and are not intended to limit the specific implementation methods of the utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the utility model shall be included in the protection scope of the claims of the utility model.

Claims

1. An optical fiber sensor, characterized in that: The optical fiber sensor comprises an optical fiber functional component, a first sensing film, and a second sensing film which are sequentially spaced apart along the axial direction of the optical fiber sensor, wherein the first sensing film is connected to the optical fiber functional component, and the second sensing film is connected to the first sensing film, wherein the optical fiber functional component has a smooth front end surface, a first FP resonant cavity is formed between the front end surface of the optical fiber functional component and the first sensing film, and a second FP resonant cavity is formed between the first sensing film and the second sensing film.

2. The optical fiber sensor according to claim 1, characterized in that: The medium in the first FP resonant cavity is air; and / or the medium in the second FP resonant cavity is air.

3. The optical fiber sensor according to claim 1, characterized in that: The first FP resonant cavity and the second FP resonant cavity are coaxially arranged.

4. The optical fiber sensor according to claim 1, characterized in that: The reflectivity of the first sensing film is 50-75%, and / or the reflectivity of the second sensing film is ≥90%.

5. The optical fiber sensor according to claim 1, characterized in that: The diameter of the optical fiber functional component is 100-200um.

6. The optical fiber sensor according to claim 1, characterized in that: The distance between the first sensing film and the front end surface of the optical fiber functional component is 50-110 nm.

7. The optical fiber sensor according to any one of claims 1 to 6, characterized in that: The first sensing film and the second sensing film are encapsulated in the front part of the optical fiber functional component through a packaging structure, and the packaging structure has a hollow cavity running through its two end faces. The packaging structure sleeves the optical fiber functional component through the hollow cavity, and the front end face of the optical fiber functional component, the first sensing film, and the second sensing film are encapsulated in the hollow cavity with front and rear intervals.

8. The optical fiber sensor according to claim 7, characterized in that: The packaging structure includes a first connecting tube, a second connecting tube and a third connecting tube which are connected in sequence along its own axial direction. The first connecting tube is sleeved on the front part of the optical fiber functional component. The front end of the first connecting tube is used to support and set the first sensing membrane. The second connecting tube cover is set on the periphery of the first sensing membrane. The front end of the second connecting tube is used to support and set the second sensing membrane. The third connecting tube cover is set on the periphery of the second sensing membrane.

9. The optical fiber sensor according to claim 8, characterized in that: The first connecting tube is made of a capillary tube; and / or the second connecting tube is made of a capillary tube; and / or the third connecting tube is made of a capillary tube.

10. The optical fiber sensor according to any one of claims 1 to 6, characterized in that: The optical fiber functional component, the first sensing film and the second sensing film are integrally arranged, the optical fiber functional component and the first sensing film are connected via the first remaining portion of the optical fiber, and the first sensing film and the second sensing film are connected via the second remaining portion of the optical fiber.

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