MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber and its manufacturing method

Abstract

The present invention relates to a MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber and a manufacturing method thereof, comprising a plum blossom-shaped optical fiber, a guide hole, a support frame, a hole shoulder, an interference cavity body, a sensitive diaphragm, a first reflection layer and a second reflection layer; the plum blossom-shaped optical fiber comprises a central optical fiber and a surrounding optical fiber; the plum blossom-shaped optical fiber is fixed in the guide hole and connected to the second reflection layer, the central optical fiber is aligned with the center of the first reflection layer, the surrounding optical fiber is connected to the second reflection layer, the second reflection layer is arranged on the hole shoulder formed by the bottom of the guide hole and the interference cavity body, the interference cavity body is arranged at the bottom of the guide hole and is coaxial with the center of the guide hole, the sensitive diaphragm is manufactured at the bottom of the interference cavity body and connected to the support frame, and the first reflection layer is arranged on the sensitive diaphragm. Compared with the prior art, the present invention has the advantages of less process flow, low processing difficulty, flexible structural design, low manufacturing cost, etc.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing, and in particular to a MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber and a manufacturing method thereof. Background Art

[0002] With the introduction of the concept of Industry 4.0, industrial production is gradually moving towards intelligence and informatization. Sensor technology is also facing challenges in miniaturization, intelligence, stability and sensitivity. Sensors based on fiber interferometers have the advantages of high sensitivity, anti-electromagnetic interference, and long transmission distance. They have attracted great attention in the field of sensing at home and abroad, and there are many related studies. Micro-electro-mechanical systems (MEMS) are electronic mechanical devices developed on the basis of semiconductor technology. They have the characteristics of miniaturization, integration, multi-function and intelligence. Their technology integrates lithography, corrosion, thin film deposition, LIGA, silicon micromachining, non-silicon micromachining and precision machining, and has a wide range of applications in the field of high-tech industries. Fiber interferometers based on MEMS technology have unique advantages such as diverse structural designs, a wide range of sensitive diaphragm materials, and high interference sensitivity. They are widely used in the detection of physical and chemical quantities such as temperature, pressure, sound waves, and concentration, and have become a research hotspot in the field of intelligent sensing.

[0003] In 2009, Guan Xile et al. (Research on Fiber Optic Dynamic Strain Sensing Technology [D]. University of Electronic Science and Technology of China, 2009.) proposed a Fabry-Perot interferometer cavity consisting of two optical plates with highly reflective films on their end faces and strictly parallel to each other. They used vacuum coating technology to coat about 0.3 μm thick metal chromium (Cr) as a reflective film on the punched quartz fiber end face and the cut and polished quartz end face, respectively, in an effort to achieve maximum reflectivity and improve the interference quality of the Fabry-Perot cavity. However, this method of increasing the reflectivity of the interference cavity is cumbersome, difficult to ensure processing consistency, and has poor flexibility. In 2010, Sun Dong et al. proposed a micro-fiber Fabry-Perot cavity made by using 157nm wavelength laser (Acta Photonica Sinica, 2010, 39(07):1239-1242). The microchannel made by 157nm laser was used to introduce the measured medium into the Fabry-Perot cavity located at the top of the single-mode optical fiber. In order to increase the contrast of the Fabry-Perot cavity, it also adopted the method of coating the reflection surface of the Fabry-Perot cavity with a high reflective film. However, this method is more difficult to process and more complicated to operate. In 2012, Akkaya OC et al. proposed a fiber Fabry-Perot interferometer cavity for acoustic wave detection (J. Microelectromech.S., 2012, 21(6):1347-1356). It increased the reflectivity of the silicon surface by etching photonic crystals on the silicon film and improved the interference quality of the Fabry-Perot cavity. Although this design can reduce the process of coating on the silicon surface, the overall process flow of the preparation is relatively complicated, the process is difficult, the cost is high, and the assembly of the sensor is also cumbersome.

[0004] In summary, when constructing a fiber interferometer cavity, related studies have improved the interference quality of the interferometer cavity by depositing a reflection-enhancing film on the two reflection surfaces of the interferometer cavity. The preparation process is relatively complicated and tedious, and the cost is high, and the process difficulty is relatively large. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber and a manufacturing method thereof.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A MEMS multi-beam interference cavity based on a plum blossom-shaped optical fiber, comprising a plum blossom-shaped optical fiber, a guide hole, a support frame, a hole shoulder, an interference cavity body, a sensitive diaphragm, a first reflection layer and a second reflection layer; the plum blossom-shaped optical fiber comprises a central optical fiber and a surrounding optical fiber;

[0008] The plum blossom-shaped optical fiber is fixed in the guide hole and connected to the second reflective layer, the central optical fiber is aligned with the center of the first reflective layer, the surrounding optical fiber is connected to the second reflective layer, the second reflective layer is arranged on the hole shoulder formed by the bottom of the guide hole and the interference cavity body, the interference cavity body is arranged at the bottom of the guide hole and is coaxial with the center of the guide hole, the sensitive diaphragm is made at the bottom of the interference cavity body and connected to the supporting frame, and the first reflective layer is arranged on the sensitive diaphragm.

[0009] Preferably, the distance between the sensitive membrane and the end face of the plum blossom-shaped optical fiber is controlled by the length of the interference cavity body.

[0010] Preferably, the plum blossom-shaped optical fiber is arranged in a manner that N-1 surrounding optical fibers are evenly distributed around a central optical fiber.

[0011] Preferably, the guide hole, the support frame, the hole shoulder, the interference cavity body, and the sensitive diaphragm are all components integrally made of materials of a silicon wafer, a silicon oxide wafer, a silicon nitride wafer, or an SOI wafer by dry etching or wet etching.

[0012] Preferably, the first reflective layer is a component made of gold, silver or aluminum by evaporation or magnetron sputtering.

[0013] Preferably, the second reflective layer is a component made of gold, silver or aluminum by evaporation or magnetron sputtering.

[0014] Preferably, the light emitted by the light source enters the spectrometer through the optical fiber circulator and is divided into N beams of light by the spectrometer, wherein the N-1 beam enters the surrounding optical fiber, is reflected by the second reflection layer at the bottom of the guide hole and enters the optical fiber, and the remaining beam of light enters the central optical fiber, is reflected by the first reflection layer on the sensitive diaphragm and re-enters the optical fiber. These N partial light beams converge and interfere in the spectrometer, and the converged and interfered light beams enter the back-end detection system through the optical fiber circulator.

[0015] Preferably, the interference signal is related to the cavity length of the interference cavity body. When the detected signal causes the sensitive diaphragm to deform axially, the cavity length of the interference cavity body changes, thereby causing the interference signal to change. The information of the measured physical quantity can be obtained by demodulating the interference signal.

[0016] A method for manufacturing the MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber comprises the following steps:

[0017] Step 1: Making guide holes on silicon wafers, silicon oxide wafers, silicon nitride wafers, and SOI wafers by dry etching or wet etching process;

[0018] Step 2: Making a sensitive membrane at the bottom of the guide hole by dry etching or wet etching process and forming an interference cavity body;

[0019] Step 3: Depositing the first reflection layer and the second reflection layer on the upper part of the sensitive diaphragm and the hole shoulder by evaporating or magnetron sputtering gold, silver, and aluminum materials;

[0020] Step 4: Insert the plum blossom-shaped optical fiber into the guide hole, locate the optical fiber end face through the hole shoulder, align the central optical fiber inside the plum blossom-shaped optical fiber with the center of the first reflection layer on the sensitive diaphragm, and the surrounding optical fiber inside the plum blossom-shaped optical fiber contacts the second reflection layer on the hole shoulder. Use epoxy resin or hot melt adhesive to fix the plum blossom-shaped optical fiber in the guide hole to form a multi-beam optical fiber interference cavity.

[0021] Compared with the prior art, the present invention realizes the construction of the optical fiber interference cavity and the optimization of its interference quality by combining the plum blossom-shaped optical fiber and the high-reflectivity step hole. Compared with the traditional method of optimizing the interference quality of the interference cavity by the precipitation process, this method of optimizing the interference quality of the interference cavity by increasing the number of reflective optical fibers and optimizing the splitting ratio of the optical splitter simplifies the process of coating the optical fiber end face and the surface of the sensitive diaphragm separately. Only one coating is needed to increase the reflectivity of the two reflective surfaces of the interference cavity at the same time, so as to optimize the interference quality of the interference cavity. It has the advantages of less process flow, low processing difficulty, flexible structural design, and low production cost. At the same time, when processing the sensitive diaphragm, a guide positioning hole for optical fiber assembly is integrally made, which can greatly improve the assembly efficiency of the interference cavity. In addition, the optical fiber interference cavity using the MEMS process also has the advantages of small size, light weight, high degree of integration, and mass production. Therefore, the MEMS multi-beam interference cavity proposed by the present invention will contribute to the application and promotion of the optical fiber interference cavity in more fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of a MEMS multi-beam interference cavity based on a plum blossom-shaped optical fiber according to the present invention;

[0023] Figure 2 A schematic diagram of the structure of a plum blossom-shaped optical fiber made for the N light splitting ports of a 1×N light splitter;

[0024] Figure 3 for Figure 2 A schematic cross-sectional structure diagram in the BB direction;

[0025] Figure 4 Schematic diagram of the structure of the plum blossom-shaped optical fiber processed and manufactured for the five splitting ports of the 1×5 splitter;

[0026] Figure 5 for Figure 4 A schematic cross-sectional structure diagram in the BB direction;

[0027] Figure 6 Schematic diagram of the structure of the plum blossom-shaped optical fiber processed and manufactured for the five splitting ports of the 1×9 splitter;

[0028] Figure 7 for Figure 6 A schematic cross-sectional structure diagram in the BB direction;

[0029] Figure 8 A schematic diagram of making guide holes on a silicon oxide wafer by wet etching;

[0030] Fig. 9 A schematic diagram of manufacturing a sensitive membrane and forming an interference cavity body by wet etching at the bottom of the guide hole;

[0031] Fig.10 Schematic diagram of forming the first reflective layer and the second reflective layer.

[0032] 1 is a plum blossom-shaped optical fiber, 2 is a guide hole, 3 is a support frame, 4 is a hole shoulder, 5 is an interference cavity body, 6 is a sensitive diaphragm, 7 is a first reflection layer, 8 is a second reflection layer, 9 is a central optical fiber, and 10 is a surrounding optical fiber. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] Example 1

[0035] The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber and its manufacturing method proposed in the present invention has an overall structure referring to Figure 1 The device mainly includes a plum blossom-shaped optical fiber 1, a guide hole 2, a support frame 3, a hole shoulder 4, an interference cavity body 5, a sensitive diaphragm 6, a first reflection layer 7, a second reflection layer 8, a central optical fiber 9 and a surrounding optical fiber 10.

[0036] The plum blossom-shaped optical fiber 1 is fixed in the guide hole 2 and connected to the second reflection layer 8. The central optical fiber 9 in the plum blossom-shaped optical fiber 1 is aligned with the center of the first reflection layer 7. The surrounding optical fiber 10 in the plum blossom-shaped optical fiber 1 is connected to the second reflection layer 8. The second reflection layer 8 is made on the hole shoulder 4 formed by the bottom of the guide hole 2 and the interference cavity body 5. The interference cavity body 5 is made at the bottom of the guide hole 2 and is coaxial with the center of the guide hole 2. The sensitive diaphragm 6 is made at the bottom of the interference cavity body 5 and connected to the supporting frame 3. The first reflection layer 7 is made on the sensitive diaphragm 6. The distance between the sensitive diaphragm 6 and the end face of the plum blossom-shaped optical fiber 1 is controlled by the length of the interference cavity body 5.

[0037] See also Figure 2The plum blossom optical fiber 1 is made of N light splitting ports of a 1×N light splitter (N=2, 3, 4...), see Figure 3 The plum blossom-shaped optical fiber 1 is arranged in a uniformly distributed manner with N-1 surrounding optical fibers 10 around a central optical fiber 9. The number of splittings of the splitter and the splitting ratio of the splitter are determined according to the reflectivity and fineness required by the actual interference cavity.

[0038] The guide hole 2, support frame 3, hole shoulder 4, interference cavity body 5 and sensitive diaphragm 6 are integrally made by dry etching or wet etching of silicon wafer, silicon oxide wafer, silicon nitride wafer, SOI (Silicon-On-Insulator) wafer and other materials.

[0039] The first reflective layer 7 and the second reflective layer 8 may be made of materials such as gold, silver, and aluminum by evaporation or magnetron sputtering.

[0040] The sensing principle of the interference cavity is: the light emitted by the light source enters the beam splitter through the fiber circulator, and is divided into N beams of light by the beam splitter, of which the N-1 beam enters the surrounding fiber 10 and is reflected by the second reflection layer 8 at the bottom of the guide hole 2 and enters the fiber, and the remaining beam of light enters the central fiber 9 and is reflected by the first reflection layer 7 on the sensitive diaphragm 6 and re-enters the fiber. These N partial light beams converge and interfere in the beam splitter, and the converged and interfered light beams enter the back-end detection system through the fiber circulator. The interference signal is related to the cavity length of the interference cavity body 5. When the detected signal causes the sensitive diaphragm 6 to deform axially, the cavity length of the interference cavity body 5 changes, thereby causing the change of the interference signal. By demodulating the interference signal, the information of the measured physical quantity can be obtained.

[0041] The basic processing of the interference cavity is as follows:

[0042] Step 1: Read Figure 8 , forming a guide hole 2 on a silicon wafer, a silicon oxide wafer, a silicon nitride wafer, an SOI (Silicon-On-Insulator) wafer or the like by dry etching or wet etching;

[0043] Step 2: See Fig. 9 , a sensitive membrane 6 is manufactured at the bottom of the guide hole 2 by dry etching or wet etching and the interference cavity body 5 is formed;

[0044] Step 3: Read Fig.10 , depositing a first reflection layer 7 and a second reflection layer 8 on the upper part of the sensitive diaphragm 6 and the hole shoulder 4 by evaporating or magnetron sputtering gold, silver, aluminum and other materials;

[0045] Step 4: Insert the plum blossom-shaped optical fiber 1 into the guide hole 2, locate the optical fiber end face through the hole shoulder 4, align the central optical fiber 9 inside the plum blossom-shaped optical fiber 1 with the center of the first reflection layer 7 on the sensitive membrane 6, and the surrounding optical fiber 10 inside the plum blossom-shaped optical fiber 1 contacts the second reflection layer 8 on the hole shoulder 4. Use adhesives such as epoxy resin and hot melt adhesive to fix the plum blossom-shaped optical fiber 1 in the guide hole 2 to form a multi-beam optical fiber interference cavity.

[0046] Example 2

[0047] The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber proposed in the present invention has an overall structure referring to Figure 1 The device mainly includes a plum blossom-shaped optical fiber 1, a guide hole 2, a support frame 3, a hole shoulder 4, an interference cavity body 5, a sensitive diaphragm 6, a first reflection layer 7, a second reflection layer 8, a central optical fiber 9 and a surrounding optical fiber 10.

[0048] The plum blossom-shaped optical fiber 1 is fixed in the guide hole 2 and connected to the second reflection layer 8. The central optical fiber 9 in the plum blossom-shaped optical fiber 1 is aligned with the center of the first reflection layer 7. The surrounding optical fiber 10 in the plum blossom-shaped optical fiber 1 is connected to the second reflection layer 8. The second reflection layer 8 is made on the hole shoulder 4 formed by the bottom of the guide hole 2 and the interference cavity body 5. The interference cavity body 5 is made at the bottom of the guide hole 2 and is coaxial with the center of the guide hole 2. The sensitive diaphragm 6 is made at the bottom of the interference cavity body 5 and connected to the supporting frame 3. The first reflection layer 7 is made on the sensitive diaphragm 6. The distance between the sensitive diaphragm 6 and the end face of the plum blossom-shaped optical fiber 1 is controlled by the length of the interference cavity body 5.

[0049] See also Figure 4 The plum blossom optical fiber 1 is made of 5 splitting ports of a 1×5 splitter, and the splitting ratio is equal. Figure 5 In the view of FIG. 1 , the plum blossom-shaped optical fiber 1 has four surrounding optical fibers 10 arranged uniformly around the circumference of the central optical fiber 9.

[0050] The guide hole 2, the support frame 3, the hole shoulder 4, the interference cavity body 5 and the sensitive membrane 6 are integrally manufactured by dry etching a silicon wafer.

[0051] The first reflective layer 7 and the second reflective layer 8 are made by evaporating gold.

[0052] The sensing principle of the interference cavity is: the light emitted by the light source enters the optical splitter through the optical fiber circulator, and the optical fiber is split by the optical splitter. The remaining beam of light enters the central optical fiber 9, is reflected by the first reflection layer 7 on the sensitive diaphragm 6, and re-enters the optical fiber. These five parts of the light beam converge and interfere in the optical splitter, and the converged and interfered light beams enter the back-end detection system through the optical fiber circulator. The interference signal is related to the cavity length of the interference cavity body 5. When the detected signal causes the sensitive diaphragm 6 to deform axially, the cavity length of the interference cavity body 5 changes, thereby causing the change of the interference signal. By demodulating the interference signal, the information of the measured physical quantity can be obtained.

[0053] The basic processing of the interference cavity is as follows:

[0054] Step 1: Read Figure 8 , forming a guide hole 2 on the silicon wafer by dry etching;

[0055] Step 2: See Fig. 9 , a sensitive membrane 6 is made at the bottom of the guide hole 2 by dry etching and an interference cavity body 5 is formed;

[0056] Step 3: Read Fig.10 , depositing a first reflection layer 7 and a second reflection layer 8 on the upper part of the sensitive membrane 6 and the hole shoulder 4 by evaporating gold;

[0057] Step 4: Insert the plum blossom-shaped optical fiber 1 into the guide hole 2, locate the optical fiber end face through the hole shoulder 4, align the central optical fiber 9 of the plum blossom-shaped optical fiber 1 with the center of the first reflection layer 7 on the sensitive membrane 6, and the surrounding optical fiber 10 of the plum blossom-shaped optical fiber 1 contacts the second reflection layer 8 on the hole shoulder 4. Use epoxy resin to fix the plum blossom-shaped optical fiber 1 in the guide hole 2 to form a multi-beam optical fiber interference cavity.

[0058] Embodiment 3:

[0059] The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber and its manufacturing method proposed in the present invention has an overall structure referring to Figure 1 The device mainly includes a plum blossom-shaped optical fiber 1, a guide hole 2, a support frame 3, a hole shoulder 4, an interference cavity body 5, a sensitive diaphragm 6, a first reflection layer 7, a second reflection layer 8, a central optical fiber 9 and a surrounding optical fiber 10.

[0060] The plum blossom-shaped optical fiber 1 is fixed in the guide hole 2 and connected to the second reflection layer 8. The central optical fiber 9 in the plum blossom-shaped optical fiber 1 is aligned with the center of the first reflection layer 7. The surrounding optical fiber 10 in the plum blossom-shaped optical fiber 1 is connected to the second reflection layer 8. The second reflection layer 8 is made on the hole shoulder 4 formed by the bottom of the guide hole 2 and the interference cavity body 5. The interference cavity body 5 is made at the bottom of the guide hole 2 and is coaxial with the center of the guide hole 2. The sensitive diaphragm 6 is made at the bottom of the interference cavity body 5 and connected to the supporting frame 3. The first reflection layer 7 is made on the sensitive diaphragm 6. The distance between the sensitive diaphragm 6 and the end face of the plum blossom-shaped optical fiber 1 is controlled by the length of the interference cavity body 5.

[0061] See also Figure 6 The plum blossom optical fiber 1 is made of 9 splitting ports of a 1×9 splitter, and the splitting ratio is equal. Figure 7 In the view of the plum blossom-shaped optical fiber 1, 9 surrounding optical fibers 10 are arranged uniformly around the circumference of the central optical fiber 9.

[0062] The guide hole 2, the support frame 3, the hole shoulder 4, the interference cavity body 5 and the sensitive diaphragm 6 are integrally manufactured by wet etching a silicon oxide wafer.

[0063] The first reflective layer 7 and the second reflective layer 8 may be made by magnetron sputtering gold.

[0064] The sensing principle of the interference cavity is: the light emitted by the light source enters the beam splitter through the fiber circulator, and is divided into 9 beams of light by the beam splitter, of which 8 beams enter the surrounding fiber 10 and are reflected by the second reflection layer 8 at the bottom of the guide hole 2 and enter the fiber, and the remaining beam enters the central fiber 9 and is reflected by the first reflection layer 7 on the sensitive diaphragm 6 and re-enters the fiber. These 9 partial beams converge and interfere in the beam splitter, and the converged and interfered beams enter the back-end detection system through the fiber circulator. The interference signal is related to the cavity length of the interference cavity body 5. When the detected signal causes the sensitive diaphragm 6 to deform axially, the cavity length of the interference cavity body 5 changes, thereby causing the change of the interference signal. By demodulating the interference signal, the information of the measured physical quantity can be obtained.

[0065] The basic processing of the interference cavity is as follows:

[0066] Step 1: Referring to 8, a guide hole 2 is formed on the silicon oxide wafer by wet etching;

[0067] Step 2: Referring to 9, a sensitive membrane 6 is made at the bottom of the guide hole 2 by wet etching to form an interference cavity body 5;

[0068] Step 3: Referring to 10, a first reflective layer 7 and a second reflective layer 8 are deposited on the upper part of the sensitive diaphragm 6 and the hole shoulder 4 by magnetron sputtering gold;

[0069] Step 4: Insert the plum blossom-shaped optical fiber 1 into the guide hole 2, locate the optical fiber end face through the hole shoulder 4, align the central optical fiber 9 of the plum blossom-shaped optical fiber 1 with the center of the first reflection layer 7 on the sensitive membrane 6, and the surrounding optical fiber 10 of the plum blossom-shaped optical fiber 1 contacts the second reflection layer 8 on the hole shoulder 4. Use hot melt adhesive to fix the plum blossom-shaped optical fiber 1 in the guide hole 2 to form a multi-beam optical fiber interference cavity.

[0070] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber, characterized in that: The invention comprises a plum blossom-shaped optical fiber (1), a guide hole (2), a support frame (3), a hole shoulder (4), an interference cavity body (5), a sensitive membrane (6), a first reflection layer (7) and a second reflection layer (8); the plum blossom-shaped optical fiber (1) comprises a central optical fiber (9) and a surrounding optical fiber (10); The plum blossom-shaped optical fiber (1) is fixed in the guide hole (2) and connected to the second reflective layer (8), the central optical fiber (9) is aligned with the center of the first reflective layer (7), the surrounding optical fiber (10) is connected to the second reflective layer (8), the second reflective layer (8) is arranged on a hole shoulder (4) formed by the bottom of the guide hole (2) and the interference cavity body (5), the interference cavity body (5) is arranged at the bottom of the guide hole (2) and is coaxial with the center of the guide hole (2), the sensitive diaphragm (6) is made at the bottom of the interference cavity body (5) and connected to the support frame (3), and the first reflective layer (7) is arranged on the sensitive diaphragm (6); Light emitted by a light source enters a beam splitter through an optical fiber circulator and is divided into N beams of light by the beam splitter, wherein N-1 beams enter a surrounding optical fiber (10) and are reflected by a second reflection layer (8) at the bottom of a guide hole (2) and enter the optical fiber, and the remaining beam of light enters a central optical fiber (9) and is reflected by a first reflection layer (7) on a sensitive film (6) and re-enters the optical fiber. These N beams of light converge and interfere in the beam splitter, and the converged and interfered beams of light enter a back-end detection system through the optical fiber circulator.

2. The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber according to claim 1, characterized in that: The distance between the sensitive membrane (6) and the end face of the plum blossom-shaped optical fiber (1) is controlled by the length of the interference cavity body (5).

3. The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber according to claim 1, characterized in that: The plum blossom-shaped optical fiber (1) is arranged in a manner that N-1 surrounding optical fibers (10) are evenly distributed around a central optical fiber (9).

4. The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber according to claim 1, characterized in that: The guide hole (2), the support frame (3), the hole shoulder (4), the interference cavity body (5), and the sensitive diaphragm (6) are all components integrally made of materials of a silicon wafer, a silicon oxide wafer, a silicon nitride wafer, or an SOI wafer by dry etching or wet etching.

5. The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber according to claim 1, characterized in that: The first reflective layer (7) is a component made of gold, silver or aluminum by evaporation or magnetron sputtering.

6. The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber according to claim 1, characterized in that: The second reflective layer (8) is a component made of gold, silver or aluminum by evaporation or magnetron sputtering.

7. The MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber according to claim 1, characterized in that: The interference signal is related to the cavity length of the interference cavity body (5). When the detected signal causes the sensitive diaphragm (6) to deform axially, the cavity length of the interference cavity body (5) changes, thereby causing the interference signal to change. By demodulating the interference signal, information about the measured physical quantity can be obtained.

8. A method for manufacturing the MEMS multi-beam interference cavity based on plum blossom-shaped optical fiber as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Making guide holes (2) on a silicon wafer, a silicon oxide wafer, a silicon nitride wafer, or an SOI wafer by dry etching or wet etching process; Step 2: manufacturing a sensitive membrane (6) at the bottom of the guide hole (2) by dry etching or wet etching process and forming an interference cavity body (5); Step 3: Depositing a first reflection layer (7) and a second reflection layer (8) on the upper part of the sensitive diaphragm (6) and the hole shoulder (4) by evaporating or magnetron sputtering gold, silver, and aluminum materials; Step 4: Insert the plum blossom-shaped optical fiber (1) into the guide hole (2), position the optical fiber end face through the hole shoulder (4), align the central optical fiber (9) inside the plum blossom-shaped optical fiber (1) with the center of the first reflection layer (7) on the sensitive membrane (6), and make the surrounding optical fiber (10) inside the plum blossom-shaped optical fiber (1) contact the second reflection layer (8) on the hole shoulder (4). Use epoxy resin or hot melt adhesive to fix the plum blossom-shaped optical fiber (1) in the guide hole (2) to form a multi-beam optical fiber interference cavity.

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