阅读说明：本技术 局部放电efpi光纤传感器法珀腔探头的制造方法 (Manufacturing method of Fabry-Perot cavity probe of partial discharge EFPI optical fiber sensor ) 是由 司文荣 吴旭涛 傅晨钊 李秀广 陆启宇 黄兴德 黄华 虞益挺 贺林 高凯 何宁辉 于 2019-10-31 设计创作，主要内容包括：本发明涉及一种局部放电EFPI光纤传感器法珀腔探头的制造方法,包括以下步骤：步骤1)局部放电EFPI光纤传感器法珀腔探头敏感膜片结构及辅助定位结构加工；步骤2)小孔即法珀腔加工；步骤3)大孔即光纤安装定位阶梯孔加工；步骤4)法珀腔敏感膜片内表面镀膜；步骤5)法珀腔探头光纤装配。与现有技术相比,本发明具有利用SOI片实现了μm级敏感膜片法珀腔探头的大批量加工制备等优点。(The invention relates to a method for manufacturing a Fabry-Perot cavity probe of a partial discharge EFPI optical fiber sensor, which comprises the following steps of: step 1) processing a Fabry-Perot cavity probe sensitive diaphragm structure and an auxiliary positioning structure of a partial discharge EFPI optical fiber sensor; step 2), processing small holes, namely Fabry-Perot cavities; step 3), machining a large hole, namely an optical fiber installation positioning stepped hole; step 4), coating the inner surface of the Fabry-Perot cavity sensitive membrane; and 5) assembling the Fabry-Perot cavity probe optical fiber. Compared with the prior art, the invention has the advantages that the large-scale processing and preparation of the micron-scale sensitive diaphragm Fabry-Perot cavity probe are realized by utilizing the SOI sheet, and the like.)

1. A method for manufacturing a Fabry-Perot cavity probe of a partial discharge EFPI optical fiber sensor is characterized by comprising the following steps:

step 1) processing a Fabry-Perot cavity probe sensitive diaphragm structure and an auxiliary positioning structure of a partial discharge EFPI optical fiber sensor;

step 2), processing small holes, namely Fabry-Perot cavities;

step 3), machining a large hole, namely an optical fiber installation positioning stepped hole;

step 4), coating the inner surface of the Fabry-Perot cavity sensitive membrane;

and 5) assembling the Fabry-Perot cavity probe optical fiber.

2. The manufacturing method of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor according to claim 1, wherein the specific processing procedures of the sensitive diaphragm structure and the auxiliary positioning structure are as follows:

device layer A, SiO of Si material₂An SOI sheet composed of the spacing layer B and the substrate layer C made of Si material is used as a processing object; after removing surface oxide from the SOI wafer by HF solution, the sensitive diaphragm structure and the auxiliary positioning structure are obtained by adopting an inductively coupled ion dry etching process, and the thickness h of the sensitive diaphragm is determined by the device layer A.

3. The method for manufacturing the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor according to claim 2, wherein the auxiliary positioning structure is that a circular boss is surrounded on the periphery of the sensitive diaphragm structure, the thickness of the boss is the Fabry-Perot cavity length l, and the diameter of the circular boss is the diameter of an optical fiber used for assembly.

4. The manufacturing method of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor, as claimed in claim 3, wherein the thickness of the boss can be adjusted by a coating process; the boss periphery constitute by ring recess and four location arrows, the glue dripping groove when the ring recess is as fixed optic fibre during the assembly is in order to prevent that the colloid from flowing into sensitive diaphragm surface to observe the arrow and in order to confirm optic fibre external diameter and the coincidence of ring boss external diameter, thereby realize better axiality.

5. The manufacturing method of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor according to claim 1, wherein the machining of the small hole Fabry-Perot cavity is specifically as follows:

after the sensitive membrane structure and the auxiliary positioning structure are obtained in the step 1), back side alignment is carried out on the SOI sheet according to the effective radius a of the sensitive membrane to form a small hole, namely a Fabry-Perot cavity.

6. The manufacturing method of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor according to claim 1, wherein the machining of the large hole, namely the optical fiber installation positioning stepped hole specifically comprises the following steps:

and (3) etching a large hole according to the length l of the Fabry-Perot cavity and the outer diameter 2b of the optical fiber to form an optical fiber installation positioning stepped hole and accurately control the length l of the Fabry-Perot cavity and the coaxiality of the Fabry-Perot cavity and the optical fiber.

7. The manufacturing method of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor according to claim 1, wherein the inner surface of the Fabry-Perot cavity sensitive membrane is coated with a film, and the film is specifically as follows:

after the etching in the step 3) is finished, the reflectivity of the diaphragm is improved by adopting an electron beam evaporation instrument to plate a gold-plated reflecting film, and the reflectivity end face reflectivity R is carried out on the inner side of the sensitive diaphragm₁And the end face reflectivity R of the optical fiber₂And carrying out optimized pairing.

8. The manufacturing method of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor according to claim 1, wherein the Fabry-Perot cavity probe optical fiber assembly is specifically as follows:

and 4, assembling the selected optical fiber by using the auxiliary positioning structure formed in the step 1 and the Fabry-Perot cavity probe formed after the step 4, coating sealing glue on the optical fiber sheath, and realizing firm connection based on the installation positioning stepped hole.

Technical Field

The invention relates to a manufacturing technology of partial discharge equipment, in particular to a manufacturing method of a Fabry-Perot cavity probe of a partial discharge EFPI optical fiber sensor.

Background

An Extrinsic Fabry-Perot Interferometer (EFPI) optical fiber sensor is a high-performance ultrasonic detection system which converts ultrasonic waves into mechanical vibration by using a sensitive diaphragm structure, converts the mechanical vibration into optical parameter change by using Fabry-Perot interference technology, and finally converts, acquires and demodulates the optical parameter change by related instruments such as a photoelectric detector and the like, and is used for detecting ultrasonic signals of partial discharge generated by oil-paper insulation defects in a large-scale power transformer at present. As shown in FIG. 1, theThe Fabry-Perot cavity probe of the sensor generally comprises a core body containing optical fibers, a circular sleeve and a sensitive diaphragm (an ultrasonic coupling vibration element); the main working parameters are as follows: the thickness of the vibration diaphragm is h, the effective diameter of the vibration diaphragm is 2a, the length of the Fabry-Perot cavity is l, and the reflectivity R of two reflecting end surfaces of the Fabry-Perot cavity₁And R₂. According to the principle of multi-beam interference, the reflected light intensity I of the Fabry-Perot cavity, the first-order natural frequency f (resonant frequency) of the circular diaphragm completely restrained around the periphery according to the principle of elasticity mechanics, and the displacement y, namely the sensitivity S, generated by the center of the diaphragm vibrating under the pressure P generated by an ultrasonic signal are as follows:

in the formula: i is₀(λ) is the incident light wavelength; n is the refractive index of the medium in the Fabry-Perot cavity; r₁And R₂Is the reflectivity of the two reflective end faces 1 and 2 shown in fig. 1; c is a constant; a is the effective radius of the sensitive membrane; d is the bending stiffness; g is the acceleration of gravity; h is the thickness of the sensitive membrane; rho is the density of the membrane material; e is the elastic modulus of the membrane material; mu is the Poisson's ratio of the membrane material.

According to the formulas (1) to (3), the main parameters I, f and y of the work performance of the EFPI optical fiber sensor selected by the materials are obtained by the thickness h and the radius a of the sensitive diaphragm, the length l of the Fabry-Perot cavity and the reflectivity R of two reflecting end faces of the Fabry-Perot cavity₁、R₂And (6) determining. The natural frequency f of the sensitive membrane is in direct proportion to the thickness h of the sensitive membrane and in inverse proportion to the square of the effective radius a of the membrane; the thinner the thickness h of the vibrating diaphragm, the greater the sensitivity S of the diaphragm, while keeping the natural frequency f of the diaphragm constant.

At present, the processing and preparation method of the Fabry-Perot cavity probe of the EFPI optical fiber sensor commonly used for detecting partial discharge ultrasonic signals of power equipment such as a transformer and the like is shown in figure 2, quartz is used as a sensitive vibration diaphragm, and an adhesive is used for connecting a quartz tube; the optical fiber is fixedly connected with the optical fiber collimator by using an adhesive; and finally, fixedly connecting the quartz tube with the optical fiber collimator by using an adhesive, thereby forming the Fabry-Perot cavity probe with the thickness h of the sensitive diaphragm, the effective radius a and the length l of the Fabry-Perot cavity. The method is easy to cause the problems of end surface damage, pollution and the like in the manufacturing process, is only suitable for being developed and tested in the primary stage of a laboratory, needs to process sensors with various sizes and structures, and has the advantages of easy realization and low cost when the number of the sensors is small, but due to manual splicing, the structural parameter repeatability of the sensors is poor when the resonance inherent frequency of partial discharge ultrasonic signal detection is up to ten-odd kHz, namely when the main structural parameters of a Fabry-Perot cavity probe, such as the thickness h of a sensitive diaphragm, are in micron order, and the mass processing and preparation cannot be realized.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for manufacturing a Fabry-Perot cavity probe of a partial discharge EFPI optical fiber sensor.

The purpose of the invention can be realized by the following technical scheme:

a manufacturing method of a Fabry-Perot cavity probe of a partial discharge EFPI optical fiber sensor comprises the following steps:

step 1) processing a Fabry-Perot cavity probe sensitive diaphragm structure and an auxiliary positioning structure of a partial discharge EFPI optical fiber sensor;

step 2), processing small holes, namely Fabry-Perot cavities;

step 3), machining a large hole, namely an optical fiber installation positioning stepped hole;

step 4), coating the inner surface of the Fabry-Perot cavity sensitive membrane;

and 5) assembling the Fabry-Perot cavity probe optical fiber.

Preferably, the specific processing process of the sensitive membrane structure and the auxiliary positioning structure is as follows:

device layer A, SiO of Si material₂An SOI sheet composed of the spacing layer B and the substrate layer C made of Si material is used as a processing object; removing the SOI wafer by HF solutionAfter surface oxidation, a sensitive membrane structure and an auxiliary positioning structure are obtained by adopting an inductively coupled ion dry etching process, and the thickness h of the sensitive membrane is determined by the device layer A.

Preferably, the auxiliary positioning structure is a circular boss surrounding the periphery of the sensitive diaphragm structure, the boss is Fabry-Perot cavity long l in thickness, and the diameter of the circular boss is the diameter of the optical fiber for assembly.

Preferably, the thickness of the boss can be adjusted through a coating process; the boss periphery constitute by ring recess and four location arrows, the glue dripping groove when the ring recess is as fixed optic fibre during the assembly is in order to prevent that the colloid from flowing into sensitive diaphragm surface to observe the arrow and in order to confirm optic fibre external diameter and the coincidence of ring boss external diameter, thereby realize better axiality.

Preferably, the small hole, namely the Fabry-Perot cavity, is specifically processed as follows:

after the sensitive membrane structure and the auxiliary positioning structure are obtained in the step 1), back side alignment is carried out on the SOI sheet according to the effective radius a of the sensitive membrane to form a small hole, namely a Fabry-Perot cavity.

Preferably, the machining of the large hole, namely the optical fiber installation positioning stepped hole, is specifically as follows:

and (3) etching a large hole according to the length l of the Fabry-Perot cavity and the outer diameter 2b of the optical fiber to form an optical fiber installation positioning stepped hole and accurately control the length l of the Fabry-Perot cavity and the coaxiality of the Fabry-Perot cavity and the optical fiber.

Preferably, the inner surface coating of the Fabry-Perot cavity sensitive membrane is specifically as follows:

after the etching in the step 3) is finished, the reflectivity of the diaphragm is improved by adopting an electron beam evaporation instrument to plate a gold-plated reflecting film, and the reflectivity end face reflectivity R is carried out on the inner side of the sensitive diaphragm₁And the end face reflectivity R of the optical fiber₂And carrying out optimized pairing.

Preferably, the assembly of the fabry-perot cavity probe optical fiber is specifically as follows:

and 4, assembling the selected optical fiber by using the auxiliary positioning structure formed in the step 1 and the Fabry-Perot cavity probe formed after the step 4, coating sealing glue on the optical fiber sheath, and realizing firm connection based on the installation positioning stepped hole.

Compared with the prior art, the invention has the following beneficial effects:

1. the main parameters of the working performance of the EFPI sensor comprise the thickness h of a sensitive diaphragm, the working radius a of the diaphragm, the length l of a Fabry-Perot cavity and the reflectivity R of two reflecting end surfaces of the Fabry-Perot cavity₁、R₂The Fabry-Perot cavity probe processing and preparing process can realize the thickness h of the sensitive diaphragm, the working radius a of the diaphragm and the reflectivity R of the reflecting end face₂The accurate control of the probe is realized, and the large-scale processing and preparation of the micron-scale sensitive diaphragm Fabry-Perot cavity probe are realized by utilizing the SOI sheet.

2. By adopting the auxiliary positioning structure and the stepped hole, the coaxiality of the optical fiber core diameter and the central reflection area of the diaphragm and the accurate control of the cavity length l of the Fabry-Perot cavity are ensured, and the Fabry-Perot cavity is ensured to be at a stable working point according to the designed cavity length l.

Drawings

FIG. 1 is a schematic diagram of the structure and parameters of a Fabry-Perot cavity probe of an optical fiber EFPI ultrasonic sensor;

FIG. 2 is a fabrication method of a Fabry-Perot cavity probe of a conventional partial discharge EFPI optical fiber sensor;

FIG. 3 shows a fabrication process for fabricating a Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor.

FIG. 4 shows a stepped-hole support beam arm type sensitive membrane under a microscope processed by the process of the present invention.

FIG. 5 shows an example of detecting ultrasonic signals by a partial discharge EFPI optical fiber sensor manufactured by the process of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.

A manufacturing method of a Fabry-Perot cavity probe of a partial discharge EFPI optical fiber sensor comprises 5 steps of processing a sensitive diaphragm structure and an auxiliary positioning structure of the Fabry-Perot cavity probe of the partial discharge EFPI optical fiber sensor, processing a small hole, namely a Fabry-Perot cavity, processing a large hole, namely an optical fiber installation positioning stepped hole, coating a film on the inner surface of the Fabry-Perot cavity sensitive diaphragm and assembling an optical fiber, wherein the steps are as shown in figure 2.

The step 1: and processing the sensitive membrane structure and the auxiliary positioning structure. Device layer A, SiO of Si material that can be tailored with each layer thickness₂An SOI sheet composed of the spacing layer B and the substrate layer C made of Si material is used as a processing object; after removing surface oxides from the SOI wafer by HF solution, an inductive coupling plasma dry etching process is adopted to obtain a sensitive diaphragm structure and an auxiliary positioning structure, and the thickness h of the sensitive diaphragm is determined by the device layer A. The auxiliary positioning structure is characterized in that a circular boss is arranged around the periphery of the sensitive diaphragm structure, the thickness of the boss is the Fabry-Perot cavity length l, the boss can be adjusted through a coating process, and the diameter of the circular boss is the diameter of an optical fiber for assembly; the boss periphery comprises ring groove and four location arrows, and the glue dripping groove when the ring groove is as fixed optic fibre is in order to prevent that the colloid from flowing into sensitive diaphragm surface during the assembly to observe the arrow and coincide with ring boss external diameter in order to confirm optic fibre external diameter, thereby realize better axiality.

The step 2: and processing a small hole, namely a Fabry-Perot cavity. And (2) after obtaining the sensitive membrane structure and the auxiliary positioning structure on the basis of the step (1), carrying out reverse side alignment on the SOI wafer, and forming a small hole, namely a Fabry-Perot cavity, according to the effective radius a of the sensitive membrane.

The step 3: and machining a large hole, namely an optical fiber installation positioning stepped hole. On the basis of the step 2, large holes are etched according to the length l of the Fabry-Perot cavity and the outer diameter 2b of the optical fiber, so that an optical fiber installation positioning stepped hole is formed, and the length l of the Fabry-Perot cavity and the coaxiality of the Fabry-Perot cavity and the optical fiber can be accurately controlled.

The step 4: and coating the inner surface of the sensitive membrane. After the etching is finished, the reflectivity of the diaphragm is improved by adopting an electron beam evaporation plating instrument gold-plated reflecting film, the optical performance of the Fabry-Perot cavity is improved, the change of the reflected light intensity is enhanced, and the signal-to-noise ratio of the sensor is improved. Namely, the end face reflectivity R of the inner side of the sensitive membrane is subjected to reflectivity according to (1)₁And the end face reflectivity R of the optical fiber₂Optimized pairing is carried out to realize stable operation of the Fabry-Perot cavity under the selected light sourceDo this.

And step 5: and assembling the Fabry-Perot cavity probe optical fiber. And 4, assembling the selected optical fiber by using the auxiliary positioning structure formed in the step 1 and the Fabry-Perot cavity probe formed after the step 4, coating special sealing glue on the optical fiber sheath, and realizing firm connection based on the installation positioning stepped hole.

The embodiment of the processing and preparation process of the invention comprises the following steps: the end of the formed Fabry-Perot cavity probe is 3 multiplied by 3mm, the size is slightly larger than the diameter of the optical fiber by 2.5mm, the natural frequency of the sensitive diaphragm covers the partial discharge ultrasonic frequency band of 20kHz-200kHz, and more than 500 Fabry-Perot cavity probes can be processed on one 4-inch SOI sheet at one time. Fig. 4 shows a microscope stepped-hole supporting beam arm type sensing diaphragm, the length L of the supporting beam arm is 142 μm, the cross-sectional width w is 15 μm, the effective radius a of the central sensing unit is 79 μm, and the diaphragm thickness h is 5 μm. FIG. 5 shows an example of the ultrasonic signal detected by the partial discharge EFPI optical fiber sensor manufactured by the process of the present invention.

While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.