A kind of based on core melt exposure type papillary microcavity sensing device

Abstract

The application discloses a kind of based on core deviation fusion exposure type F-P microfluidic cavity sensing device, belong to optical fiber sensing and microfluidic technology field, including standard single-mode optical fiber, quartz capillary, side-hole optical fiber, taper optical fiber, taper optical fiber is obtained by standard single-mode optical fiber taper interception, side-hole optical fiber is symmetrically distributed with first micropore, second micropore, the taper optical fiber taper region diameter is greater than the diameter of second micropore;The first end surface of the taper optical fiber is fused with the second micropore port outside end surface of side-hole optical fiber, the taper optical fiber is pre-installed in quartz capillary inside, and the end surface of the side-hole optical fiber is fused and fixed with one end of quartz capillary.The application uses the above-mentioned one based on core deviation fusion exposure type F-P microfluidic cavity sensing device, solves the problems that traditional device is easy to block, sealing failure, poor signal quality, high preparation difficulty, insufficient micro-detection, realizes the technical effects of glueless sealing, high contrast interference, micro-sample detection, good structural consistency and batch production.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing and microfluidics technology, and in particular to a sensing device based on an eccentric fusion-exposed Fabry-Perot microfluidic cavity. Background Technology

[0002] The fiber optic Fabry-Perot interferometric microfluidic cavity integrates an optical interference cavity with a microfluidic channel, possessing numerous advantages such as miniaturization, resistance to electromagnetic interference, label-free detection, remote real-time monitoring, and high sensitivity. It is one of the core devices in the field of microfluidic optical sensing and has irreplaceable application value in the field of microfluidic parameter detection.

[0003] The core design principle of existing fiber optic Fabry-Perot microfluidic cavities is as follows: two optical reflective surfaces are constructed on the end face or inside of the optical fiber, and a microfluidic channel is integrated between the two sets of reflective surfaces to enable the liquid under test to fully interact with the transmitted optical field. By collecting and analyzing signals such as wavelength drift, phase change, and light intensity fluctuation of the interference spectrum, quantitative detection of parameters such as refractive index and concentration of the liquid can be achieved.

[0004] However, existing technical solutions have many core defects in actual preparation and application, which seriously restrict the detection performance, stability and mass industrial application of the devices: The device is difficult to assemble, has a low yield, and is prone to clogging and damage. Current mainstream solutions often insert tapered optical fibers into the micropores of edge-hole optical fibers to achieve optical path introduction and liquid sealing. However, the tapered region of the fiber is only tens of micrometers in diameter and quite long, making it highly susceptible to bending, breakage, and end-face damage during insertion into the micropore. Manual assembly requires extremely high precision, resulting in low yields in mass production. Furthermore, the insertion structure occupies the effective flow cross-section within the micropore, significantly increasing fluid transmission resistance. When the liquid being tested contains tiny particles or biomolecules, micropore clogging is significant, leading to short device lifespan and poor detection stability.

[0005] Poor sealing reliability and susceptibility to interference in detection accuracy are issues. Existing devices generally use organic adhesives such as UV adhesives and epoxy resins to fix and seal optical fibers to micropores and capillaries. These adhesives are prone to moisture absorption, swelling, aging, and cracking when immersed in liquid environments for extended periods. Furthermore, organic adhesives continuously release small molecule impurities, contaminating trace amounts of the sample and significantly impacting the accuracy of biomedical and precision chemical detection results.

[0006] Poor optical path coupling quality and low detection and demodulation accuracy. Traditional structures often adopt a fiber core straight-through alignment optical path design, in which a large amount of incident light is directly transmitted, making it impossible to form effective double-beam interference. At the same time, the fiber core straight-through optical path is prone to introducing stray reflections from fiber optic connectors and end faces, increasing detection background noise, resulting in insufficient depth of interference spectrum valleys, and limiting parameter demodulation accuracy.

[0007] Therefore, there is an urgent need to develop a Faber microfluidic cavity sensing device. Summary of the Invention

[0008] The purpose of this invention is to provide a Fabry-Perot microfluidic cavity sensing device based on eccentric welding and exposure, which solves the problems of easy clogging, sealing failure, poor signal quality, high manufacturing difficulty, and insufficient micro-sample detection in traditional devices, and achieves the technical effects of glue-free sealing, high-contrast interference, micro-sample detection, good structural consistency, and mass production capability.

[0009] To achieve the above objectives, the present invention provides a Fabry-Perot microfluidic cavity sensing device based on eccentric fusion splicing, comprising a standard single-mode fiber, a quartz capillary, an edge-hole fiber, and a tapered fiber. The tapered fiber is formed by tapering the standard single-mode fiber. The edge-hole fiber is provided with symmetrically distributed first and second micro-holes, and the diameter of the tapered region of the tapered fiber is larger than the diameter of the second micro-hole. The first end face of the tapered optical fiber is fused to the outer end face of the second micro-hole port of the side-hole optical fiber. The fusion point is located on the outer side of the end face of the side-hole optical fiber. The tapered optical fiber does not extend into the interior of the second micro-hole and forms an annular fusion area with its slightly larger diameter. The tapered optical fiber is pre-inserted inside the quartz capillary tube, and the end face of the side-hole optical fiber is fused and fixed to one end of the quartz capillary tube; the second end of the tapered optical fiber is fused to the front end of the standard single-mode optical fiber, and the fusion area only covers the cladding of the standard single-mode optical fiber and avoids the fiber core to prevent damage to the Fabry-Perot interference.

[0010] Preferably, the front end face of the standard single-mode fiber constitutes the first reflecting surface of the Fabry-Perot interferometer cavity, the fusion splice surface of the quartz capillary and the side-hole fiber constitutes the second reflecting surface of the Fabry-Perot interferometer cavity, and the cavity length of the Fabry-Perot interferometer cavity is determined by the length of the tapered fiber.

[0011] Preferably, the first micropore is a liquid inlet channel, through which the liquid to be tested flows sequentially through the first micropore and the interior of the quartz capillary, and is discharged from the end of the quartz capillary near the standard single-mode optical fiber.

[0012] Preferably, the edge-hole optical fiber is a dual-hole symmetrical structure optical fiber with an overall length of 700~900μm and an outer diameter of 125μm. The diameters of the first and second micropores are both 25~30μm. The small aperture can significantly reduce the consumption of the liquid to be tested, realize micro-sample injection, and at the same time enhance the capillary driving force and improve the flow rate stability. The micropores are spatially symmetrically distributed, which further optimizes the micro-detection capability, splice matching and signal stability while ensuring smooth micro-flow.

[0013] Preferably, the tapered fiber is made from standard single-mode fiber through a tapering process, retaining a tapered length of approximately 500-600 μm. This length ensures a smooth transition of the tapered region diameter from 125 μm to the target diameter of 40-45 μm (slightly larger than the 30 μm diameter of the micro-aperture in the edge-hole fiber), avoiding splicing failure due to an excessively short tapered region diameter, while also avoiding the mechanical fragility and increased manufacturing difficulty caused by an excessively long tapered region length. Within this length range, the tapered fiber has sufficient stiffness and length to facilitate insertion and positioning within the quartz capillary, as well as two splicing operations with the micro-aperture port of the edge-hole fiber and the standard single-mode fiber. Simultaneously, the 500-600 μm tapered length forms a reasonable difference with the subsequent retained length of the quartz capillary, ensuring that the tail end of the tapered fiber can be naturally exposed outside the capillary, providing ample operating space for subsequent splicing.

[0014] Preferably, the length of the quartz capillary is 300~350μm, which is shorter than the length of the tapered optical fiber, and the second end of the tapered optical fiber is exposed outside the tail end of the quartz capillary.

[0015] Preferably, the outer diameter of the quartz capillary is 125 μm, matching the outer diameter of the standard single-mode fiber and the edge-hole fiber. This allows for good coaxial alignment and end-face fusion splicing, significantly reducing the risk of offset deviation and rotational mismatch during splicing. Simultaneously, the identical outer diameter allows for processing using standard 125 μm fiber clamps, cleavers, and fusion splicer programs, eliminating the need for additional custom tooling, greatly simplifying the manufacturing process and improving splicing strength and repeatability. Preferably, the standard single-mode fiber has an outer diameter of 125 μm and a core inner diameter of 9 μm. Single-mode transmission ensures high contrast of the interference signal. Furthermore, the mature fusion splicing process and broad commercial compatibility significantly reduce manufacturing and integration difficulty, and facilitate subsequent surface functionalization, thus achieving the advantages of low cost, high reliability, and mass production while ensuring sensing performance.

[0016] Preferably, the entire device adopts a fully welded, adhesive-free sealing structure with no organic glue filler layer.

[0017] Preferably, the preparation process of this device includes the following steps: S1. Preparation of tapered fiber: Take a standard single-mode fiber, remove the coating layer, and perform tapering treatment using the fused taper process. Stop tapering when the diameter of the tapered end face reaches 40~45μm, and cut a tapered section with a length of 500~600μm to obtain the tapered fiber. S2. End face fusion sealing: Fix the side hole fiber to the fusion station, align the first end face of the tapered fiber with the outer end face of the port of the second micro hole, keep them coaxially aligned and start the fusion to make the end face of the tapered fiber and the side hole fiber fused together to form an annular fusion sealing area around the second micro hole. S3. Quartz Capillary Assembly and Cutting: Insert the side-hole fiber assembly with the tapered fiber fused into the quartz capillary, so that the tapered fiber is accommodated in the cavity of the quartz capillary. Align the end face of the side-hole fiber with one end of the quartz capillary and fix it by fusion. After fusion, cut the quartz capillary, leaving a length of 300~350μm, so that the second end of the tapered fiber is exposed outside the tail end of the quartz capillary. S4. Off-core fusion splicing: Fix the standard single-mode fiber at the fusion splicing station, adjust the position so that the exposed end of the tapered fiber is aligned with the cladding region of the standard single-mode fiber and avoids the fiber core, start the fusion splicing program to complete the off-core fusion splicing, and obtain a complete Fabry-Perot microfluidic cavity sensing device.

[0018] Preferably, the detection method of the device includes the following steps: System connection: Connect the first micro-hole of the edge-hole optical fiber to the micro-injection pump through the microfluidic pipeline, and connect the liquid outlet of the quartz capillary to the waste liquid collection device. Fluid-driven: When the micro-injection pump is started, the liquid to be tested enters the device from the first micro-hole under the combined action of the pump driving force and capillary force. After flowing through the inner cavity of the quartz capillary, it is discharged from the tail end, so that the liquid to be tested fills the Fabry-Perot interference cavity region in the quartz capillary. Interference signal generation: Broadband probe light is incident into a standard single-mode fiber. The probe light is reflected at the front end of the standard single-mode fiber and the fusion splice of the quartz capillary and the side-hole fiber, respectively. The two reflected beams return to the standard single-mode fiber and couple to generate a Fabry-Perot interference spectrum. Parameter detection: The Fabry-Perot interference spectrum is acquired in real time using a spectral demodulation device. The liquid to be tested replaces the air medium in the cavity, causing a change in the effective refractive index of the interference cavity, which leads to a shift in the characteristic wavelength of the interference spectrum. By analyzing the amount of the shift in the characteristic wavelength, the refractive index or concentration parameter of the liquid to be tested can be obtained.

[0019] Therefore, the present invention employs the above-mentioned Fabry-Perot microfluidic cavity sensing device based on eccentric welding exposure, and the technical effects are as follows: 1) Tapered optical fiber and edge-hole optical fiber are directly fused to the outside of the micro-hole port, without the need to insert into the micro-hole, thus avoiding the problems of tapered optical fiber being easily broken and clogging the micro-hole in traditional solutions; 2) All connections require no organic adhesives, are highly corrosion-resistant and pollution-free; the reflectivity difference between the standard single-mode fiber end face (first reflecting surface) and the capillary-side hole fiber fusion splice surface (second reflecting surface) is moderate, which can obtain high-contrast Fabry-Perot interference fringes, facilitating subsequent signal demodulation. 3) The edge-hole fiber adopts a small-diameter symmetrical micropore, which requires less liquid and has stable capillary drive, which is beneficial for the detection of trace samples. 4) All components have the same outer diameter, good coaxiality, are easy to manufacture, and are easy to integrate with standard fiber optic devices; In summary, this device has the combined advantages of simple structure, reliable sealing, adjustable cavity length, high signal quality, suitability for micro-scale detection, and good repeatability.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the device connection of an embodiment of the present invention based on an exposed Fabry-Perot microfluidic cavity sensing device with eccentric welding; Figure 2 This is a schematic diagram of the Fabry-Perot microfluidic cavity structure of an embodiment of the present invention based on an eccentric welded exposed Fabry-Perot microfluidic cavity sensing device; Figure 3 This is a schematic diagram of the optical path and liquid flow path of an embodiment of the present invention based on an exposed Fabry-Perot microfluidic cavity sensing device with eccentric welding.

[0022] Figure Labels 1. Standard single-mode optical fiber; 2. Quartz capillary; 3. Side-hole optical fiber; 4. Tapered optical fiber; 5. First micro-aperture; 6. Second micro-aperture; 7. First reflecting surface; 8. Second reflecting surface; A. Optical path; B. Liquid flow path. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] Example 1 like Figures 1-3 As shown, the present invention provides a Fabry-Perot microfluidic cavity sensing device based on eccentric fusion splicing, which is composed of a standard single-mode fiber 1, a quartz capillary tube 2, a side-hole fiber 3, and a tapered fiber 4 arranged coaxially. All components have a uniform outer diameter of 125μm and can be directly adapted to standard fiber processing fixtures and fusion splicing equipment.

[0026] The edge-hole fiber 3 is a dual-hole symmetrical structure silica fiber with an overall length of 800 μm and an outer diameter of 125 μm. It has two symmetrically distributed micropores, the first 5 and the second 6, each with a diameter of 28 μm. This small-aperture design significantly reduces the amount of analyte consumed, enabling micro-sample injection, while simultaneously enhancing capillary driving force and improving flow rate stability. The symmetrical micropore distribution avoids liquid deviation and bubble residue, reduces thermal drift asymmetry, and improves detection repeatability.

[0027] The tapered fiber 4 is obtained by fusion tapering a standard single-mode fiber 1, with an overall length of 500 μm. The diameter of the tapered region gradually transitions from 125 μm to 42 μm, and its tapered end face diameter is slightly larger than the diameter of the second micro-aperture 6 of the side-hole fiber 3. The first end face of the tapered fiber 4 is fused to the outer end face of the second micro-aperture 6 of the side-hole fiber 3. The fusion point is located outside the end face of the side-hole fiber 3. The tapered fiber 4 does not extend into the interior of the second micro-aperture 6. Relying on the diameter difference, a dense annular fusion zone is formed around the micro-aperture port, achieving glue-free sealing. The tapered fiber 4 of this length has both sufficient structural rigidity and operational margin, facilitating tube insertion and positioning, as well as two fusion operations.

[0028] The quartz capillary 2 is a hollow capillary made of pure quartz material with an outer diameter of 125 μm and a cut length of 300 μm, which is shorter than the length of the tapered optical fiber 4. The tapered optical fiber 4 is pre-inserted inside the quartz capillary 2, and the end face of the side-hole optical fiber 3 is aligned and fused with one end of the quartz capillary 2. After fusion, the second end of the tapered optical fiber 4 is exposed outside the tail end of the quartz capillary 2, with an exposed length of about 200 μm, providing sufficient operating space for subsequent fusion.

[0029] The exposed second end face of the tapered fiber 4 is fixed to the front end of the standard single-mode fiber 1 using an off-core fusion splice. The splice area only covers the cladding region of the standard single-mode fiber 1, completely avoiding the core region, thus preventing stray reflections introduced into the straight optical path and ensuring the quality of the Fabry-Perot interference signal. The standard single-mode fiber 1 has an outer diameter of 125 μm and a core inner diameter of 9 μm, supporting single-mode optical transmission.

[0030] In the above structure, the front end face of the standard single-mode fiber 1 constitutes the first reflecting surface 7 of the Fabry-Perot interferometer cavity, and the fusion splice surface of the quartz capillary 2 and the side-hole fiber 3 constitutes the second reflecting surface 8 of the Fabry-Perot interferometer cavity. The cavity length of the Fabry-Perot interferometer cavity is determined by the length of the tapered fiber 4. The first micro-hole 5 of the side-hole fiber 3 serves as a liquid inlet channel. The liquid to be tested flows sequentially through the first micro-hole 5 and the interior of the quartz capillary 2, and exits from the end of the quartz capillary 2 closest to the standard single-mode fiber 1. The liquid flow area completely overlaps with the light field interaction area, achieving effective sensing. The entire device adopts a fully fused, adhesive-free sealing structure with no organic glue filling layer, possessing excellent corrosion resistance and sample cleanliness.

[0031] The fabrication process of the sensing device in this embodiment is as follows: Fabrication of tapered fiber 4: Take a section of standard single-mode fiber 1, remove the coating layer and place it on the fiber tapering platform. Taper the fiber using the fused taper process, monitor the diameter of the tapered region in real time, and stop tapering when the diameter of the tapered end face reaches 42μm. Use a fiber cleaver to cut a 500μm long tapered section in the tapered region to obtain tapered fiber 4.

[0032] Fusion splicing of tapered fiber 4 and side-hole fiber 3: Fix the side-hole fiber 3 to one side of the fiber optic fusion splicer, and adjust its posture so that the port of the second micro-hole 6 faces the fusion station; align the first end face of the tapered fiber 4 with the outside of the port of the second micro-hole 6, ensuring that the end face is coaxially aligned with the micro-hole port, and start the fusion program to perform end face fusion. Since the end face diameter of the tapered fiber 4 is larger than the micro-hole diameter, an annular fusion sealing area is formed around the micro-hole port after fusion, and the tapered fiber 4 does not enter the interior of the micro-hole.

[0033] Assembly and splicing of quartz capillary 2: Insert the side-hole fiber 3 assembly with tapered fiber 4 spliced ​​into the quartz capillary 2, so that the tapered fiber 4 is completely accommodated in the cavity of the quartz capillary 2; push the quartz capillary 2 so that its end face is tightly attached to the end face of the side-hole fiber 3, keep the three coaxial, and start the splicing procedure to fuse the side-hole fiber 3 and the quartz capillary 2 into one piece.

[0034] After the fusion splicing is completed, the other end of the quartz capillary 2 is cut with an optical fiber cleaver, leaving the length of the quartz capillary 2 at 300μm, so that the tail end of the tapered optical fiber 4 is exposed outside the quartz capillary 2.

[0035] Off-core fusion splicing of single-mode fiber: Fix the standard single-mode fiber 1 on the other side of the fusion splicer, adjust the horizontal and vertical positions so that the exposed end of the tapered fiber 4 is aligned with the cladding region of the standard single-mode fiber 1 and avoids the central core. Start the fusion program to complete the off-core fusion, and a complete Fabry-Perot microfluidic cavity sensing device is obtained.

[0036] The working principle and testing process are as follows: The optical signal emitted by the broadband light source is incident into the device through a standard single-mode fiber 1, such as... Figure 3 As shown in optical path A, since the standard single-mode fiber 1 and the tapered fiber 4 are fused with an off-core cladding, most of the incident light enters the cavity medium and propagates forward. When the beam reaches the front end face (first reflecting surface 7) of the standard single-mode fiber 1, part of the light is reflected and returns along the original path; the other part is transmitted into the cavity and continues to propagate, undergoing a second reflection when it reaches the fusion surface (second reflecting surface 8) of the quartz capillary 2 and the side-hole fiber 3. The two reflected beams couple and superimpose within the standard single-mode fiber 1, producing a Fabry-Perot interference effect and forming a stable interference spectrum.

[0037] When performing liquid testing, such as Figure 3As shown in the liquid flow path B, the first micro-hole 5 of the edge-hole optical fiber 3 is connected to a micro-injection pump via a microfluidic tube, and the outlet end of the quartz capillary 2 is connected to a waste liquid collection device. Driven by the micro-injection pump and capillary action, the liquid to be tested enters the device through the first micro-hole 5, flows through the inner cavity of the quartz capillary 2, and exits from the tail end. When the liquid fills the interference cavity region within the quartz capillary 2, the medium inside the cavity is replaced by the liquid to be tested, changing the effective refractive index of the interference cavity. This causes a change in the optical path difference between the two reflected beams, resulting in a shift in the characteristic wavelength of the interference spectrum. By using an external spectral demodulation device to acquire and analyze the shift in the interference spectrum in real time, parameters such as the refractive index and concentration of the liquid to be tested can be calculated, achieving highly sensitive micro-liquid detection.

[0038] Therefore, the present invention employs the above-mentioned eccentric fusion spliced ​​exposed Fabry-Perot microfluidic cavity sensing device, which eliminates the need for organic adhesive sealing, thus avoiding problems such as colloid aging, swelling, and sample contamination; the tapered optical fiber does not penetrate the micropore, eliminating the risk of blockage and breakage; the eccentric fusion spliced ​​optical path design effectively improves the contrast of interference fringes, and combined with the microfluidic structure of symmetrical micropores, it has the advantages of high detection accuracy, high stability, and low sample consumption. Moreover, all components are compatible with standard optical fiber processing technology, have good manufacturing consistency, and are suitable for mass production.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A sensing device based on an off-center fusion spliced ​​exposed Fabry-Perot microfluidic cavity, comprising a standard single-mode optical fiber, a quartz capillary, an edge-hole optical fiber, and a tapered optical fiber, characterized in that: The tapered optical fiber is cut from a standard single-mode optical fiber by tapering. The side-hole optical fiber is provided with a symmetrically distributed first micro-hole and a second micro-hole. The diameter of the tapered region of the tapered optical fiber is larger than the diameter of the second micro-hole. The first end face of the tapered optical fiber is fused to the outer end face of the second micro-hole port of the side-hole optical fiber, and the fusion point is located on the outer side of the end face of the side-hole optical fiber. The tapered optical fiber is pre-inserted inside the quartz capillary tube, and the end face of the side-hole optical fiber is fused and fixed to one end of the quartz capillary tube; the second end of the tapered optical fiber is fused to the front end of the standard single-mode optical fiber, and the fusion area only covers the cladding of the standard single-mode optical fiber and avoids the fiber core.

2. The eccentric welded exposed Fabry-Perot microfluidic cavity sensing device according to claim 1, characterized in that: The front end face of the standard single-mode fiber constitutes the first reflecting surface of the Fabry-Perot interferometer cavity, and the fusion splice surface of the quartz capillary and the side-hole fiber constitutes the second reflecting surface of the Fabry-Perot interferometer cavity. The cavity length of the Fabry-Perot interferometer cavity is determined by the length of the tapered fiber.

3. The eccentric welded exposed Fabry-Perot microfluidic cavity sensing device according to claim 2, characterized in that: The first micropore is a liquid inlet channel. The liquid to be tested flows through the first micropore and the inside of the quartz capillary in sequence, and is discharged from the end of the quartz capillary near the standard single-mode optical fiber.

4. The eccentric welded exposed Fabry-Perot microfluidic cavity sensing device according to claim 3, characterized in that: The tapered optical fiber has a length of 500~600μm and a taper diameter of 40~45μm.

5. A sensing device based on an eccentric welded exposed Fabry-Perot microfluidic cavity according to claim 4, characterized in that: The edge-hole fiber is a dual-hole symmetrical structure fiber with an overall length of 700~900μm, and the diameters of the first micro-hole and the second micro-hole are both 25~30μm.

6. The eccentric welded exposed Fabry-Perot microfluidic cavity sensing device according to claim 5, characterized in that: The quartz capillary has a length of 300~350μm, which is shorter than the length of the tapered optical fiber. The second end of the tapered optical fiber is exposed outside the tail end of the quartz capillary.

7. A sensing device based on an eccentric welded exposed Fabry-Perot microfluidic cavity according to claim 6, characterized in that: The outer diameter of the quartz capillary is matched with the outer diameter of the standard single-mode fiber and the side-hole fiber.

8. A sensing device based on an eccentric welded exposed Fabry-Perot microfluidic cavity according to claim 7, characterized in that: The entire device adopts a fully welded, adhesive-free sealing structure with no organic glue filler layer.

9. A sensing device based on an eccentric welded exposed Fabry-Perot microfluidic cavity according to claim 8, characterized in that: The preparation process of this device includes the following steps: S1. Preparation of tapered fiber: Take a standard single-mode fiber, remove the coating layer, and perform tapering treatment using the fused taper process. Stop tapering when the diameter of the tapered end face reaches 40~45μm, and cut a tapered section with a length of 500~600μm to obtain the tapered fiber. S2. End face fusion sealing: Fix the side hole fiber to the fusion station, align the first end face of the tapered fiber with the outer end face of the port of the second micro hole, keep them coaxially aligned and start the fusion, so that the end face of the tapered fiber and the side hole fiber are fused to form an annular fusion sealing area around the second micro hole, and the tapered fiber does not extend into the interior of the second micro hole. S3. Quartz Capillary Assembly and Cutting: Insert the side-hole fiber assembly with the tapered fiber fused into the quartz capillary, so that the tapered fiber is accommodated in the cavity of the quartz capillary. Align the end face of the side-hole fiber with one end of the quartz capillary and fuse it in place. After the fusion is completed, cut the quartz capillary, leaving a length of 300~350μm, so that the second end of the tapered fiber is exposed outside the tail end of the quartz capillary. S4. Off-core fusion splicing: Fix the standard single-mode fiber at the fusion splicing station, adjust the position so that the exposed end of the tapered fiber is aligned with the cladding region of the standard single-mode fiber and avoids the fiber core, start the fusion splicing program to complete the off-core fusion splicing, and obtain a complete Fabry-Perot microfluidic cavity sensing device.

10. A sensing device based on an eccentric welded exposed Fabry-Perot microfluidic cavity according to claim 8, characterized in that: The detection method of this device includes the following steps: System connection: Connect the first micro-hole of the edge-hole optical fiber to the micro-injection pump through the microfluidic pipeline, and connect the liquid outlet of the quartz capillary to the waste liquid collection device. Fluid-driven: When the micro-injection pump is started, the liquid to be tested enters the device from the first micro-hole under the combined action of the pump driving force and capillary force. After flowing through the inner cavity of the quartz capillary, it is discharged from the tail end, so that the liquid to be tested fills the Fabry-Perot interference cavity region in the quartz capillary. Interference signal generation: Broadband probe light is incident into a standard single-mode fiber. The probe light is reflected at the front end of the standard single-mode fiber and the fusion splice of the quartz capillary and the side-hole fiber, respectively. The two reflected beams return to the standard single-mode fiber and couple to generate a Fabry-Perot interference spectrum. Parameter detection: The Fabry-Perot interference spectrum is acquired in real time using a spectral demodulation device. The liquid to be tested replaces the air medium in the cavity, causing a change in the effective refractive index of the interference cavity, which leads to a shift in the characteristic wavelength of the interference spectrum. By analyzing the amount of the shift in the characteristic wavelength, the refractive index or concentration parameter of the liquid to be tested can be obtained.

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