A T-tube based fiber-optic Fabry-Perot cavity sensing device

Abstract

This invention discloses a fiber optic Fabry-Perot cavity sensing device based on a T-tube, comprising a T-tube with a first channel and two vertically arranged second and third channels. The first channel is internally sealed with a first single-mode fiber, and its other end is fused to a quartz capillary to form a first reflective surface. The other end of the quartz capillary is fused to a second single-mode fiber to form a second reflective surface. Two symmetrically positioned microfluidic channels are located near the second single-mode fiber at one end of the quartz capillary, communicating with the central tube of the quartz capillary to form a Fabry-Perot cavity. Both the quartz capillary and the second single-mode fiber are located within the T-tube. The two microfluidic channels are also connected to the second and third channels, respectively. The second channel is connected to a needle tube, which is connected to a microfluidic pump. The third channel is connected to a waste liquid tank. This invention offers high detection efficiency; the Fabry-Perot cavity is formed through fusion splicing, resulting in high-quality optical mirrors, and is protected by encapsulation, making it suitable for a wide range of applications.

Description

Technical Field

[0001] This utility model relates to the field of fiber optic sensing and microfluidics technology, specifically to a fiber optic Fabry-Perot cavity sensing device based on a T-tube. Background Technology

[0002] Fiber optic Fabry-Perot cavity (FAPC) devices have become important tools in the field of biochemical sensing due to their outstanding advantages such as high sensitivity, resistance to electromagnetic interference, compact structure, and suitability for remote monitoring. Their basic principle is to utilize two parallel reflecting surfaces to form an interference cavity. When the analyte liquid enters the cavity, the effective optical path length changes due to the change in the refractive index of the material within the cavity, subsequently causing a drift in the interference spectrum. Ultimately, by demodulating the spectral information, high-precision measurement of parameters such as the concentration of the analyte liquid can be achieved. Existing fiber optic Fabry-Perot cavities mostly consist of two fiber end faces forming the reflectors of the Fabry-Perot cavity. However, their microfluidic channels are limited to axial small holes at both ends of a capillary tube. Fluid slowly seeps in through capillary action, resulting in extremely low displacement efficiency and consequently low detection efficiency. Utility Model Content

[0003] This invention addresses the problem of low detection efficiency in existing technologies by disclosing a fiber optic Fabry-Perot cavity sensing device based on a T-tube. This invention directly connects two lateral microfluidic channels to channels two and three of the T-tube, allowing the liquid to be measured to be instantly flushed and filled into the microfluidic Fabry-Perot cavity under the pressure of the flow channel. This significantly improves the liquid replacement speed and thus enhances the detection efficiency for trace fluids. The Fabry-Perot cavity is formed by fusion welding, resulting in high-quality optical mirrors. Furthermore, it is protected by encapsulation, making it suitable for a wide range of applications.

[0004] This utility model is achieved through the following technical solution: This invention first provides a fiber optic Fabry-Perot cavity sensing device based on a T-tube, comprising a T-tube, a first channel, and two vertically arranged second and third channels. A first single-mode fiber is sealed inside the first channel. One end of the first single-mode fiber is connected to a fiber optic modulator, and the other end is fused with a quartz capillary to form a first reflective surface. The other end of the quartz capillary is fused with a second single-mode fiber to form a second reflective surface. Two symmetrically positioned microfluidic channels are provided near the end of the quartz capillary close to the second single-mode fiber. These two microfluidic channels communicate with the central tube of the quartz capillary to form a Fabry-Perot cavity. Both the quartz capillary and the second single-mode fiber are located inside the T-tube. The two microfluidic channels are also connected to the second and third channels, respectively. The second channel is connected to a needle for controlling the injection and discharge of the liquid to be measured, and the needle tubing is connected to a microfluidic pump. The third channel is connected to a waste liquid tank.

[0005] As a further step, the first single-mode optical fiber is inserted into the No. 1 channel and then sealed with optical adhesive.

[0006] As a further improvement, the two microfluidic channels of the quartz capillary are the inlet channel and the outlet channel, respectively. The inlet channel is located in channel number two, and the outlet channel is located in channel number three.

[0007] As a further improvement, the length of the quartz capillary is 40-60 micrometers, the length of the inlet channel and the outlet channel are both 60 micrometers, and the angle between them and the axis of the quartz capillary is 50°.

[0008] As a further improvement, the inner diameter of channel one, the outer diameter of the quartz capillary, the outer diameter of the first single-mode fiber, and the outer diameter of the second single-mode fiber are the same.

[0009] As a further improvement, the quartz capillary has an outer diameter of 125 micrometers and an inner diameter of 70 micrometers.

[0010] As a further improvement, both the first and second single-mode fibers are standard single-mode fibers with an inner diameter of 9 micrometers.

[0011] As a further improvement, the length of the second single-mode fiber is 58-65 micrometers.

[0012] As a further improvement, the inner diameter of both the second and third channels is 100 micrometers, and the sum of their lengths is 400-800 micrometers.

[0013] As a further advancement, the length of channel one ranges from 100 to 180 micrometers.

[0014] The features and beneficial effects of this utility model are as follows: (1) This utility model directly connects the two microfluidic channels on the side with the second and third channels of the T-tube, so that the liquid to be tested can be instantly flushed and filled into the microfluidic Fabry cavity under the pressure of the flow channel, which greatly improves the liquid replacement speed and thus improves the detection efficiency of the refractive index of trace fluids.

[0015] (2) This utility model has a simple and compact structure. The Fabry-Perot cavity is formed by welding, resulting in high quality optical mirrors. It is also protected by encapsulation, exhibiting strong mechanical robustness and a wide range of applications.

[0016] (3) This utility model adopts mature optical fiber splicing and polishing technology, and the raw material cost is low, which reduces the production cost. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the fiber optic Fabry-Perot cavity sensing device based on a T-tube according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the Fabry-Perot cavity described in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of the Fabry-Perot cavity as described in an embodiment of this utility model.

[0019] Explanation of reference numerals in the attached figures: 1. First single-mode optical fiber; 2. Quartz capillary tube; 3. Microfluidic channel inlet; 4. Microfluidic channel outlet; 5. T-tube; 51-Channel 1; 52-Channel 2; 53-Channel 3; 6. First reflecting surface; 7. Second reflecting surface; 8. Second single-mode optical fiber; 9. Inlet channel; 10. Outlet channel; 11-Needle tube; 12-Waste liquid tank; A. Optical signal path; B. Path of the liquid to be tested into the microfluidic channel; L1: Fabry-Perot cavity length; L2: Second single-mode optical fiber length. Detailed Implementation

[0020] To facilitate understanding of this utility model, a more comprehensive description of this utility model will be provided below, along with embodiments of this utility model, but this does not limit the scope of this utility model.

[0021] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] A fiber optic Fabry-Perot cavity sensing device based on a T-tube, such as Figures 1 to 3 As shown, it includes a T-shaped tube 5, which includes a first channel 51 and two vertically arranged second and third channels 52 and 53. The first channel 51 is sealed (bonded) with a first single-mode fiber 1. One end of the first single-mode fiber 1 is connected to a fiber optic modulator (plugged into the mounting port of the fiber optic modulator). The fiber optic modulator is a HYPERION. The first reflective surface 6 is formed by fusing the other end of the si155 with the quartz capillary tube 2. The second reflective surface 7 is formed by fusing the other end of the quartz capillary tube 2 with the second single-mode fiber 8. Two microfluidic channels are provided at one end of the quartz capillary tube 2 near the second single-mode fiber 8. The two microfluidic channels are connected to the central tube of the quartz capillary tube 2 to form a Fabry-Perot cavity. The quartz capillary tube 2 and the second single-mode fiber 8 are both located in the T-shaped tube 5. The two microfluidic channels are also connected to the second channel 52 and the third channel 53, respectively. The second channel 52 is connected to the needle tube 11, which is used to control the injection and discharge of the liquid to be tested, via a rubber hose. The needle tube 11 is connected to the microfluidic pump. The third channel 53 is connected to the waste liquid tank 12 via a rubber hose.

[0024] In one embodiment, the two microfluidic channels of the quartz capillary 2 are an inlet channel 9 and an outlet channel 10, respectively. The inlet channel 9 is located in the second channel 52, and the outlet channel 10 is located in the third channel 53.

[0025] In some embodiments, the outer diameter of the quartz capillary 2 is 125 micrometers and the inner diameter is 70 micrometers. The outer diameter is perfectly matched with the first single-mode fiber 1 and the second single-mode fiber 8 to facilitate fusion splicing, while the inner diameter provides a smooth channel for fluid.

[0026] In some embodiments, the length of the quartz capillary 2 is 40-60 micrometers, and the lengths of the inlet channel 9 and the outlet channel 10 are both 60 micrometers, with an angle of 50° to the axis of the quartz capillary 2. The length of the quartz capillary 2 (40-60 micrometers) results in a Fabry-Perot cavity length of 40-60 micrometers, achieving an optimal balance between ensuring the visibility of interference fringes and maintaining refractive index detection sensitivity. Preferably, the length of the Fabry-Perot cavity is 50 micrometers.

[0027] In some embodiments, the microfluidic pump is a Lange LSP01-2A integrated syringe pump, which can precisely control the push and pull of liquid at submicro- or even nano-scale levels, ensuring that the sample can completely and smoothly fill the cavity without causing leakage or damage to the sensitive optical interface due to excessive flushing.

[0028] In some embodiments, the first single-mode fiber 1 and the second single-mode fiber 8 are both standard single-mode fibers with an outer diameter of 125 micrometers and an inner diameter of 9 micrometers. They are plug-and-play compatible with globally used fiber optic communication equipment and components, which greatly reduces the system integration cost and complexity.

[0029] In some embodiments, the second single-mode fiber 8 has a length of 58-65 micrometers, ensuring that the fiber core is fully exposed to achieve efficient optical flow interaction, while retaining sufficient structural strength to protect the internal reflective surface.

[0030] In some embodiments, the T-tube 5 is made of polyethylene. The inner diameter of the second channel 52 and the third channel 53 is 100 micrometers, and the sum of their lengths is 400-800 micrometers, preferably 500 micrometers. The inner diameter of the first channel 51 is 125 micrometers, and its length ranges from 100-180 micrometers, preferably 130 micrometers. The T-tube 5 is made of polyethylene, which significantly reduces the cost of the device while providing excellent chemical stability and making it suitable for various liquid environments. The inner diameter of the first channel 51 is 125 micrometers, which perfectly matches the outer diameters of the quartz capillary 2, the first single-mode fiber 1, and the second single-mode fiber 8.

[0031] A method for fabricating a fiber optic Fabry-Perot cavity sensing device based on a T-tube: 1) Select a quartz capillary tube 2 with an outer diameter of 125 micrometers and an inner diameter of 70 micrometers, and two single-mode optical fibers 1 and 8 with a diameter of 125 micrometers and a core diameter of 9 micrometers, and use an optical fiber cleaver to cut all the end faces flat.

[0032] 2) On a fiber optic fusion splicer, fuse one end of the first single-mode fiber 1 to one end of the quartz capillary 2. After the fusion is completed, use a fiber optic cleaver to cut the quartz capillary 2 at a distance of about 50 micrometers (L1) from the splice point.

[0033] 3) Fusion splice the second single-mode fiber 8 to the other end of the quartz capillary 2. After splicing, use a fiber optic cleaver to cut the second single-mode fiber 8 so that the remaining length of the second fiber 8 is 30 micrometers (L2).

[0034] 4) Using a grinding disc, the 30-micrometer-long quartz capillary 2 is side-polished at an angle of about 50° to a grinding depth of 60 micrometers. The quartz capillary 2 is then rotated 180° and ground again at an angle of about 50° to form two symmetrical microfluidic channels (inlet channel 9 and outlet channel 10), thus creating a microfluidic Fabry-Perot cavity with a length of 50 micrometers.

[0035] 5) Select a T-shaped tube 5 made of polyethylene. The sum of channel 2 52 and channel 3 53 is 500 micrometers and the inner diameter is 100 micrometers. The length of channel 1 51 is 130 micrometers and the inner diameter is 125 micrometers.

[0036] 6) Slowly insert the first single-mode fiber 1 from the end of channel 1 51, and adjust its position under the microscope to ensure that the opening areas of the lateral liquid inlet channel 9 and the liquid outlet channel 10 are accurately aligned with channel 2 52 and channel 3 53, respectively.

[0037] 7) Using a micro-dispensing applicator, apply a small amount of UV-curable optical adhesive to the gap between the top of channel 51 and the first single-mode fiber 1. Irradiate with a UV lamp to cure the adhesive, thereby firmly sealing the first single-mode fiber 1, the quartz capillary 2, and the second single-mode fiber 8 inside the T-tube 5.

[0038] 8) Connect channel 52 to needle tube 11 via a rubber hose, connect needle tube 11 to a microfluidic pump, and connect channel 53 to waste liquid tank 12 via a rubber hose to form a complete flow system; connect the first single-mode optical fiber 1 to the optical fiber demodulator to realize the refractive index detection of the liquid to be tested.

[0039] The working principle of a fiber optic Fabry-Perot cavity sensing device based on a T-tube is as follows: The first single-mode fiber 1 is connected to the light source. Light A emitted by the light source is transmitted through the first single-mode fiber 1. After reaching the first reflecting surface 6, it is split into two parts for transmission: for ease of description, the light here is divided into two parts: part A1 and part A2. Part A1 is immediately reflected back and returns to the first single-mode fiber 1 along the original path. Part A2 is transmitted into the cavity of the quartz capillary 2 and continues to propagate to the right to the second reflecting surface 7. After being transmitted to the second reflecting surface 7, part A2 is split into two parts: part A21 and part A22. Part A21 is reflected by the second reflecting surface 7 and passes through to the left again. Part A22 is transmitted into the second single-mode fiber 8 on the right, but it is quickly scattered by the deliberately polished and roughened end, without generating an interfering reflection signal. Part A21, reflected back by the second reflecting surface 7, is transmitted through the first reflecting surface 6 and re-enters the first single-mode fiber 1 on the left. Part of the light A1 reflected by the first reflecting surface 6 and part of the light A21 reflected by the second reflecting surface 7 propagates in the same optical fiber, but there is a critical optical path difference between them. When these two beams are finally received by the demodulator, they meet and superimpose (interference), forming an interference spectrum. When the liquid to be measured B flows into the second channel 52 of the T-tube under the drive of the needle tube 11, the liquid rapidly fills the entire Fabry-Perot cavity through the inlet channel 9 under the power drive. The change in the refractive index of the medium inside the cavity causes a phase change in the interference spectrum, which is manifested as a wavelength shift in the interference valley. By monitoring this wavelength shift in real time with an external controller, high-sensitivity, real-time measurement of the liquid refractive index can be achieved.

[0040] In summary, this application utilizes two microfluidic channel openings formed by lateral polishing, which are directly connected to channels two and three of the T-tube. This allows the test liquid to be instantly flushed and filled into the microfluidic Fabry-Perot cavity under the pressure of the flow channel, resulting in rapid liquid replacement. The overall structure of this application is compact, the Fabry-Perot cavity is formed through fusion splicing, the optical mirror surface has high quality, and it is protected by encapsulation, exhibiting strong mechanical robustness and suitability for practical applications. Furthermore, it employs mature fiber optic splicing and polishing processes, resulting in low raw material costs and suitability for mass production.

[0041] It should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A T-coupler based fiber-optic Fabry-Perot cavity sensing device, characterized by: The device includes a T-shaped tube, comprising a first channel and two vertically arranged second and third channels. The first channel is internally sealed with a first single-mode optical fiber. One end of the first single-mode optical fiber is connected to an optical fiber conditioner, and the other end is fused with a quartz capillary to form a first reflective surface. The other end of the quartz capillary is fused with a second single-mode optical fiber to form a second reflective surface. Two symmetrically positioned microfluidic channels are located near the second single-mode optical fiber at one end of the quartz capillary. These two microfluidic channels are connected to the central tube of the quartz capillary to form a Fabry-Perot cavity. Both the quartz capillary and the second single-mode optical fiber are located within the T-shaped tube. The two microfluidic channels are also connected to the second and third channels, respectively. The second channel is connected to a needle tube used to control the injection and discharge of the liquid to be tested. The needle tube is connected to a microfluidic pump. The third channel is connected to a waste liquid tank.

2. A T-tube based fiber-optic Fabry-Perot cavity sensing device according to claim 1, characterized in that: After the first single-mode optical fiber is inserted into the No. 1 channel, it is sealed with optical adhesive.

3. The T-tube based fiber Fabry-Perot cavity sensing device according to claim 1, wherein: The quartz capillary has two microfluidic channels: an inlet channel and an outlet channel. The inlet channel is located in channel number two, and the outlet channel is located in channel number three.

4. A T-tube based fiber-optic Fabry-Perot cavity sensing device according to claim 3, characterized in that: The length of the quartz capillary is 40-60 micrometers, and the length of both the inlet and outlet channels is 60 micrometers, with an angle of 50° between them and the axis of the quartz capillary.

5. The T-tube based fiber Fabry-Perot cavity sensing device of claim 1, wherein: The inner diameter of channel one, the outer diameter of the quartz capillary, the outer diameter of the first single-mode fiber, and the outer diameter of the second single-mode fiber are the same.

6. A T-tube based fiber-optic Fabry-Perot cavity sensing device according to claim 5, characterized in that: The outer diameter of the quartz capillary is 125 micrometers, and the inner diameter is 70 micrometers.

7. A T-tube based fiber-optic Fabry-Perot cavity sensing device according to claim 5, wherein: Both the first and second single-mode fibers are standard single-mode fibers with an inner diameter of 9 micrometers.

8. The T-tube based fiber-optic Fabry-Perot cavity sensing device of claim 1, wherein: The second single-mode fiber has a length of 58-65 micrometers.

9. The T-tube based fiber-optic Fabry-Perot cavity sensing device of claim 1, wherein: The inner diameter of both channels 2 and 3 is 100 micrometers, and the sum of their lengths is 400-800 micrometers.

10. The T-tube based fiber Fabry-Perot cavity sensing device of claim 1, wherein: The length of channel one ranges from 100 to 180 micrometers.

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