Ultrasonic sensor based on single-mode fiber

Abstract

The utility model relates to the technical field of optical fiber ultrasonic sensors, in particular to an ultrasonic sensor based on a single-mode optical fiber. The utility model aims to solve the problem that the conventional ultrasonic sensor is insufficient in sensitivity in partial discharge monitoring. The ultrasonic sensor provided by the utility model is provided with a single-mode optical fiber body, the single-mode optical fiber body comprises an optical fiber function part, an optical fiber first residual part, a first sensing film, an optical fiber second residual part and a second sensing film which are sequentially connected along the axial direction of the single-mode optical fiber body, and the optical fiber front end face of the single-mode optical fiber body serves as the front end face of the second sensing film. A first F-P resonant cavity is formed between the front end face of the optical fiber function part 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 continuous double-F-P resonant cavity structure is directly obtained on the single-mode fiber, so that the ultrasonic sensor has a miniaturized structure, and meanwhile, the ultrasonic sensor has higher sensitivity to ultrasonic waves emitted by partial discharge.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber ultrasonic sensors, and more specifically, to an ultrasonic sensor based on a single-mode optical fiber. Background Art

[0002] Partial discharge is a common but potentially harmful phenomenon in the operation of power equipment. Timely and accurate detection and location of partial discharge is essential for the safe and stable operation of power systems. Traditional partial discharge detection technology usually uses piezoelectric ultrasonic sensors or resistive ultrasonic sensors to receive ultrasonic signals, and is limited by the physical structure and material properties of ultrasonic sensors, so its resolution and sensitivity are limited. In addition, traditional ultrasonic ultrasonic sensors have the following defects: 1. Limited working frequency range: usually designed to work within a specific frequency range, and cannot adapt well to detection needs within different frequency ranges; 2. Insufficient environmental adaptability: greatly affected by environmental factors, such as changes in temperature, humidity, air pressure, etc. 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 with in a strong electromagnetic field or other interference environment, affecting its detection accuracy and reliability; 6. Low real-time performance: the signal processing of some traditional ultrasonic sensors takes a certain amount of time, resulting in a slow response speed and inability to monitor abnormal conditions in real time.

[0003] In view of this, it is necessary to improve the existing ultrasonic sensors in order to improve the sensitivity, accuracy and reliability of partial discharge detection, so as to realize online monitoring and fault warning of power equipment. Utility Model Content

[0004] The utility model aims to overcome at least one defect of the above-mentioned prior art and provides an ultrasonic sensor based on a single-mode optical fiber, which is used to solve the problem of insufficient sensitivity of the existing ultrasonic sensor in partial discharge monitoring.

[0005] The technical solution adopted by the utility model is to provide an ultrasonic sensor based on a single-mode optical fiber, which has a single-mode optical fiber body. The single-mode optical fiber body includes an optical fiber functional part, an optical fiber first remaining part, a first sensing film, an optical fiber second remaining part and a second sensing film which are sequentially connected along its own axis.

[0006] Among them, the optical fiber front end face of the single-mode optical fiber body serves as the front end face of the second sensing film, a first FP resonant cavity is formed between the front end face of the optical fiber functional part of the optical fiber functional part and the first sensing film, and a second FP resonant cavity is formed between the first sensing film and the second sensing film.

[0007] The ultrasonic sensor of this scheme can be realized based on a single-mode optical fiber. The optical fiber functional part is used to propagate the incident light signal, the first remaining part of the optical fiber is used to support the first sensing film, and the second remaining part of the optical fiber is used to support the second sensing film. The front end surface of the optical fiber functional part of the optical fiber functional part 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 ultrasonic 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 ultrasonic sensor to perceive partial discharge signals, so as to facilitate the subsequent analysis of the change in spectral characteristics and indirectly infer the nature 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 to monitor the partial discharge phenomenon.

[0008] Furthermore, the first FP resonant cavity and the second FP resonant cavity are coaxially arranged.

[0009] Further, the medium in the first FP resonant cavity is air; and / or the medium in the second FP resonant cavity is air.

[0010] Furthermore, the first sensing film and the second sensing film are both silicon dioxide reflective films.

[0011] Furthermore, the reflectivity of the first sensing film is 50-75%, and / or the reflectivity of the second sensing film is ≥90%.

[0012] This solution can ensure that a reverse wave of sufficient intensity is generated in the first FP resonant cavity through the reflection effect of the first sensing film, thereby generating an interference spectrum that meets the requirements with the forward wave emitted by the optical fiber component, and can also ensure that the forward wave that passes through the first sensing film and enters the second FP resonant cavity retains sufficient intensity, thereby also generating an interference spectrum that meets the requirements in the second FP resonant cavity.

[0013] Furthermore, the diameter of the single-mode optical fiber is 100-200 um.

[0014] Further, the diameter of the first sensing film is the same as the diameter of the single-mode optical fiber; and / or the diameter of the second sensing film is the same as the diameter of the single-mode optical fiber.

[0015] Further, the thickness of the first sensing film is 10-25 um; and / or the thickness of the second sensing film is 10-25 um.

[0016] Further, the length of the first remaining portion of the optical fiber is 50-100um; and / or the length of the second remaining portion of the optical fiber is 50-100um

[0017] Compared with the prior art, the beneficial effects of the utility model are as follows: 1) by directly forming a double-layer sensing film on a single-mode optical fiber, a continuous dual FP resonant cavity structure is obtained, so that the ultrasonic sensor has a miniaturized structure, and at the same time, based on the dual FP resonant cavity, it has a high sensitivity to the ultrasonic wave emitted by local discharge. In addition, the manufacturing process can utilize the characteristics of the optical fiber itself, the manufacturing process is relatively simple, and the manufacturing cost is low; 2) the ultrasonic sensor is not affected by electromagnetic interference and has a strong anti-interference ability; 3) the ultrasonic sensor has the characteristics of high sensitivity and high resolution based on the dual FP resonant cavity, and can realize accurate monitoring of small changes; 4) the ultrasonic sensor is not affected by mechanical vibration and vibration, and has high reliability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of the utility model.

[0019] Figure 2 It is a cross-sectional view of the utility model.

[0020] Figure numerals: optical fiber functional part 1, optical fiber functional part front end face 11, fiber core 12, optical fiber first remaining part 2, first sensing film 3, optical fiber second remaining part 4, second sensing film 5, optical fiber front end face 6, first FP resonant cavity 7, second FP resonant cavity 8. DETAILED DESCRIPTION

[0021] 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.

[0022] Example 1

[0023] like Figure 1-2As shown, this embodiment provides an ultrasonic sensor based on a single-mode optical fiber. The ultrasonic sensor based on a single-mode optical fiber takes a single-mode optical fiber as the main structure, and includes an optical fiber functional part 1, an optical fiber first remaining part 2, a first sensing film 3, an optical fiber second remaining part 4, and a second sensing film 5 connected in sequence along the axial direction of the single-mode optical fiber, wherein the optical fiber front end face 6 of the single-mode optical fiber body serves as the front end face of the second sensing film 5, a first FP resonant cavity 7 is formed between the optical fiber functional part front end face 11 of the optical fiber functional part 1 and the first sensing film 3, and a second FP resonant cavity 8 is formed between the first sensing film 3 and the second sensing film 5. In specific implementation, the first FP resonant cavity 7 and the second FP resonant cavity 8 can be directly etched on the single-mode optical fiber by femtosecond laser etching, thereby obtaining an ultrasonic sensor based on a single-mode optical fiber. FP resonant cavity is the abbreviation of Fabry-Pérot resonant cavity, which is an optical resonant cavity composed of two parallel reflectors. The working principle of the FP resonant cavity is based on the interference phenomenon of light. It consists of two parallel and highly reflective mirrors (or reflective surfaces), through which light is reflected back and forth, forming interference. When the incident light wave is reflected multiple times by the two mirrors in the FP resonant cavity, the multiple interferences formed strengthen the light signals of certain wavelengths, thereby producing a resonance effect. At a specific wavelength, the multiple reflected light waves will form a peak signal, while at other wavelengths they will cancel each other out.

[0024] It is easy to understand that the ultrasonic sensor of this embodiment can be realized based on a single-mode optical fiber. The optical fiber functional part 1 transmits the incident light signal, the first remaining part 2 of the optical fiber is used to support the first sensing film 3, and the second remaining part 4 of the optical fiber is used to support the second sensing film 5. The front end face 11 of the optical fiber functional part 1 forms a first FP resonant cavity 7 between the first sensing film 3, and the second FP resonant cavity 8 is formed between the first sensing film 3 and the second sensing film 5. The forward wave of the incident light signal is transmitted and reflected by the first sensing film 3 and the second sensing film 5, and multiple interference spectrum signals are generated in the first FP resonant cavity 7 and the second FP resonant cavity 8. The ultrasonic sensor is connected to a demodulator to demodulate the interference spectrum signal into information related to the ultrasonic vibration signal to monitor the local discharge ultrasonic signal. In addition, the ultrasonic sensor of the present invention also has many advantages such as simple structure, small size, and wide application range.

[0025] refer to Figure 2In a specific implementation, in order to improve the interference spectrum signal measured by the ultrasonic sensor, the centers of the first FP resonant cavity 7 and the second FP resonant cavity 8 are coaxial, so that the light emitted by the optical fiber functional part 1 can be fully reflected and transmitted when passing through the first sensing film 3 and the second sensing film 5, 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 7 is air, and the medium in the second FP resonant cavity 8 is air, which can ensure the normal operation of the dual FP resonant cavity, avoid additional packaging structure, and promote the miniaturization of the single-mode optical fiber ultrasonic sensor.

[0026] refer to Figure 1-2 Since the single-mode optical fiber is directly etched, the first sensing film 3 and the second sensing film 5 are both silica reflective films. In addition, corresponding to the size of ordinary single-mode optical fiber, the diameter of the single-mode optical fiber specifically adopted 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 3 and the second sensing film 5 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 3 and the second sensing film 5 can be avoided, thereby simplifying the manufacturing process. On the other hand, the front end face 11 of the optical fiber functional part, the first sensing film 3, and the second sensing film 5 with the same diameter are easily aligned through the core 12 located on the central axis of the optical fiber functional part 1, thereby obtaining the coaxial and aligned first FP resonant cavity 7 and second FP resonant cavity 8.

[0027] In a preferred embodiment, the reflectivity of the first sensing film 3 is 50-75%, and the reflectivity of the second sensing film 5 is ≥90%. In this way, it can be ensured that a reverse wave of sufficient intensity is generated in the first FP resonant cavity 7 through the reflection effect of the first sensing film 3, thereby generating an interference spectrum that meets the requirements with the forward wave emitted by the optical fiber component, and the forward wave that passes through the first sensing film 3 and enters the second FP resonant cavity 8 can retain sufficient intensity, thereby also generating an interference spectrum that meets the requirements in the second FP resonant cavity 8.

[0028] In order to fully sense the ultrasonic wave emitted by partial discharge while meeting the transmission and reflection requirements, the thickness of the first sensing film 3 and / or the second sensing film 5 is 10-25um. At this time, the first sensing film 3 and the second sensing film 5 can link the first remaining part 2 of the optical fiber and the second remaining part 4 of the optical fiber to undergo the required elastic deformation during partial discharge, thereby causing the cavity lengths of the first FP resonant cavity 7 and the second FP to change, thereby changing the interference spectrum characteristics measured by the single-mode optical fiber ultrasonic sensor, and the ultrasonic signal can be obtained after demodulation. In addition, the thickness of the first sensing film 3 and the second sensing film 5 can change the resonant frequency and frequency response range of the ultrasonic sensor. Studies have found that within this size range, it is more compatible with the detection of partial discharge ultrasonic waves.

[0029] In a preferred embodiment, the length of the first remaining portion 2 of the optical fiber is 50-100um; and / or, the length of the second remaining portion 4 of the optical fiber is 50-100um, the length of the first remaining portion 2 of the optical fiber is the cavity length of the first FP resonant cavity 7, and the length of the second remaining portion 4 of the optical fiber is the cavity length of the second FP resonant cavity 8, and the length directly affects the free spectral range (FSR) of the reflection spectrum, the coherence depth and the insertion loss of the ultrasonic sensor. 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.

[0030] The working principle of the present invention is as follows: when local discharge occurs, the ultrasonic signal generated by the discharge causes the first sensing film 3, the second sensing film 5, the first remaining part 2 of the optical fiber, and the second remaining part 4 of the optical fiber to undergo elastic deformation, thereby changing the cavity lengths of the first FP resonant cavity 7 and the second FP resonant cavity 8, resulting in changes in the interference spectrum characteristics of the first FP resonant cavity 7 and the second FP resonant cavity 8. The multiple interference spectra generated by the dual FP resonant cavity structure have a phase superposition effect, which improves the significance of the changes in the spectral characteristics, that is, improves the sensitivity of the ultrasonic sensor to perceive the local discharge signal, 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.

[0031] 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 ultrasonic sensor based on single-mode optical fiber, characterized in that: The single-mode optical fiber body comprises an optical fiber functional part, an optical fiber first remaining part, a first sensing film, an optical fiber second remaining part and a second sensing film which are sequentially connected along the axial direction of the single-mode optical fiber body. Among them, the optical fiber front end face of the single-mode optical fiber body serves as the front end face of the second sensing film, a first FP resonant cavity is formed between the front end face of the optical fiber functional part of the optical fiber functional part 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 single-mode optical fiber-based ultrasonic sensor according to claim 1, characterized in that: The first FP resonant cavity and the second FP resonant cavity are coaxially arranged.

3. The single-mode optical fiber-based ultrasonic 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.

4. The single-mode optical fiber-based ultrasonic sensor according to claim 1, characterized in that: The first sensing film and the second sensing film are both silicon dioxide reflective films.

5. The single-mode optical fiber-based ultrasonic sensor according to any one of claims 1 to 4, characterized in that: The reflectivity of the first sensing film is 50-75%, and / or the reflectivity of the second sensing film is ≥90%.

6. The single-mode optical fiber-based ultrasonic sensor according to any one of claims 1 to 4, characterized in that: The diameter of the single-mode optical fiber is 100-200um.

7. The single-mode optical fiber-based ultrasonic sensor according to any one of claims 1 to 4, characterized in that: The diameter of the first sensing film is the same as the diameter of the single-mode optical fiber; and / or the diameter of the second sensing film is the same as the diameter of the single-mode optical fiber.

8. The single-mode optical fiber-based ultrasonic sensor according to any one of claims 1 to 4, characterized in that: The thickness of the first sensing film is 10-25 um; and / or the thickness of the second sensing film is 10-25 um.

9. The single-mode optical fiber-based ultrasonic sensor according to any one of claims 1 to 4, characterized in that: The length of the first remaining portion of the optical fiber is 50-100 um; and / or the length of the second remaining portion of the optical fiber is 50-100 um.

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