Optical lens optical fiber preparation method, composite sensor and pressure guide wire

Abstract

The application relates to the technical field of optical fibers, and discloses an optical lens optical fiber preparation method, a composite sensor and a pressure guide wire, which comprises the following steps: S1, fusing a first single-mode optical fiber and a second single-mode optical fiber; S3, using an optical fiber fusion machine to perform arc discharge on the tail end of a hollow-core optical fiber to form a lens; S4, inserting the lens end of the hollow-core optical fiber into the inner cavity of a capillary optical fiber and performing discharge fusion; S5, fusing a multimode optical fiber and the capillary optical fiber; and S6, performing cutting and grinding treatment on the end face of the multimode optical fiber to form a sensitive diaphragm. The length of the capillary optical fiber is controlled through the optical fiber lens focusing theory during preparation. The high-performance double-F-P cavity composite sensor can be prepared through the cutting, etching, fusing and grinding processes, so that the composite measurement of the temperature and pressure double parameters can be realized, the problem that the optical fiber itself is damaged due to the use of the femtosecond laser processing process is avoided, and the manufacturing cost of the sensor is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fibers, in particular to a preparation method of an optical lens optical fiber, a composite sensor and a pressure guide wire. BACKGROUND

[0002] With the continuous development of medical technology, minimally invasive surgery is widely used due to its small trauma, fewer complications and rapid recovery. As an important medical instrument for evaluating fractional flow reserve (FFR) of coronary artery, the interventional pressure guide wire measures the blood pressure in the coronary artery to evaluate the degree of stenosis of the patient's blood vessel, thereby assisting clinical decision-making. Therefore, accurate measurement of pressure is the key to the pressure guide wire, but the existing piezoelectric, resistance type and other electric sensors still have the disadvantages of poor biocompatibility and being easily affected by electromagnetic interference. Using an optical fiber sensor is one of the effective means to achieve accurate monitoring in a complex blood vessel environment.

[0003] The Fabry-Perot (F-P) cavity sensor has been widely used in temperature and pressure monitoring due to its high sensitivity and stability. In order to reduce damage to the sensor and reduce the manufacturing cost of the sensor, a fusion and grinding process is often used to prepare the optical fiber Fabry-Perot sensor. For example, the Chinese patent document with publication number CN113188691A provides an optical fiber Fabry-Perot sealed cavity pressure sensor and a preparation method thereof. The sensor is composed of a single-mode optical fiber, a quartz capillary and a sealed cavity fixed by one-time welding. CO2 laser welding technology and fine polishing process are used.

[0004] Although the preparation process uses CO2 laser welding technology to reduce the cross-sensitivity of temperature and achieve accurate measurement of pressure. However, based on such a traditional optical fiber Fabry-Perot interferometer, when the diaphragm deforms due to external pressure, the deformation of the diaphragm will affect the quality of its reflecting surface, resulting in a decrease in reflection efficiency. Moreover, the reflecting surface is far away from the end face of the optical fiber, and due to the divergence of the light beam, the intensity of the reflected light will decrease rapidly, resulting in a decrease in coupling efficiency. SUMMARY

[0005] Therefore, the present application provides a preparation method of an optical lens optical fiber, a composite sensor and a pressure guide wire which can effectively avoid processing damage and ensure the performance of the optical fiber, thereby solving the problem that the existing optical fiber preparation process affects the performance of the optical fiber.

[0006] The technical scheme of the present application is as follows:

[0007] On the one hand, the present application provides a preparation method of an optical lens optical fiber, comprising the following steps:

[0008] S1, preparing a first single-mode optical fiber and a second single-mode optical fiber, fusing the first single-mode optical fiber and the second single-mode optical fiber, and forming an air gap,

[0009] S2, the second single-mode optical fiber is fused away from one end of the first single-mode optical fiber, and a coreless optical fiber,

[0010] S3, using an optical fiber fusion machine to arc discharge the end of the coreless optical fiber to form a lens, thereby forming a fiber lens, and the fiber lens is a semi-spherical structure,

[0011] S4, placing the coreless optical fiber and the capillary optical fiber on the optical fiber fusion machine, and inserting the lens end of the coreless optical fiber into the inner cavity of the capillary optical fiber and discharging and fusing,

[0012] S5, preparing a multi-mode optical fiber, and fusing the multi-mode optical fiber with the capillary optical fiber through the optical fiber fusion machine, and forming an air cavity,

[0013] S6, cutting and grinding the end face of the multi-mode optical fiber to form a sensitive diaphragm;

[0014] In the preparation process, the length of the capillary optical fiber is controlled by the fiber lens focusing theory.

[0015] On the basis of the above technical scheme, preferably, in step S1, the first single-mode optical fiber and the second single-mode optical fiber are formed by cutting and placed in a hydrofluoric acid solution for chemical corrosion treatment, wherein the concentration of the hydrofluoric acid solution is 40%, and the corrosion time is 5 minutes.

[0016] The discharge intensity of the first single-mode optical fiber and the second single-mode optical fiber during fusion is 85bit, and the discharge time is 1500ms.

[0017] On the basis of the above technical scheme, preferably, the grinding of the multi-mode optical fiber includes the following steps:

[0018] S61, using a roughness of 5um grinding paper to coarsely grind the end face of the multi-mode optical fiber, and synchronously monitoring the remaining length of the multi-mode optical fiber until the length of the multi-mode optical fiber is ground to 20um, and using dust-free paper to wipe off the residues generated during the grinding process;

[0019] S62, using a roughness of 1um grinding paper to grind the multi-mode optical fiber to a length of less than 5um to form a sensitive diaphragm.

[0020] On the basis of the above technical scheme, preferably, the step of controlling the length of the capillary optical fiber by the fiber lens focusing theory is as follows:

[0021] P1, by using the light generated by the ABCD matrix light source for trajectory tracking analysis, assuming that the light beam generated by the light source is a Gaussian light beam, using the matrix M LFO to correlate the output light of the single-mode optical fiber and the fiber lens;

[0022] P2, obtain the ABCD matrix of the Gaussian beam propagating in the hollow core fiber, the fiber lens and the air cavity, and obtain the system matrix M LFO ;

[0023] P3, find the best working distance d of the fiber lens to the light ray in combination with steps P1 and P2 work , that is, the distance between the output beam waist of the output beam and the tip of the optical lens fiber;

[0024] P4, solve the best working distance d work in combination with the matrix M LFO to obtain the beam waist size ω of the output beam of the fiber lens f ;

[0025] P5, guide the grinding work of the capillary fiber by judging the focusing effect.

[0026] On the basis of the above technical scheme, preferably, in the matrix M LFO , the output light of the single mode fiber and the fiber lens is associated, and the formula is as follows,

[0027]

[0028] Wherein, r LFO and r SMF are the positions of the light rays measured from the center axis of the fiber, r' LFO and r' SMF are the slopes of the light rays relative to the center axis of the fiber.

[0029] On the basis of the above technical scheme, preferably, the ABCD matrix of the Gaussian beam propagating in the hollow core fiber, the fiber lens and the air cavity is:

[0030]

[0031] From the above formula, the system matrix M LFO , that is, M LFO =M HCF M lens M CSF ;

[0032]

[0033] Wherein, n1 is the refractive index of the single mode fiber and the multi-mode fiber; d CSF is the length of the hollow core fiber, which does not include the length of the fiber lens; R is the radius of the fiber lens; d work is the best working distance of the fiber lens; M HCF is the ABCD matrix propagating in the hollow core fiber; M lens is the ABCD matrix propagating in the fiber lens; MCSF ABCD matrix for the air cavity; A, B, C, D are light transmission matrix, LFO is optical lens fiber.

[0034] On the basis of the above technical solutions, preferably, the optimal focusing range d work The solving steps are as follows:

[0035] When the curvature radius of the output light beam is infinite, as the following formula,

[0036]

[0037] Wherein, a is the beam parameter, representing the beam divergence characteristics; λ is the wavelength of light; n2 is the refractive index of the medium; ω0 is the radius of the Gaussian beam at the beam waist; A, B, C, D are light transmission matrix, LFO is optical lens fiber; π is the circular constant;

[0038] R is the radius of the fiber lens (31).

[0039] Solving it can get d work The solution is as follows:

[0040]

[0041] Wherein, ω0 is the beam waist radius of the input light beam from the single-mode fiber, λ is the center wavelength of the input Gaussian light beam.

[0042] On the basis of the above technical solutions, preferably, through d work And M LFO The beam waist size ω work Of the optical lens fiber output light beam under d f ;

[0043]

[0044] When d work Works in the range of d0, the output light beam has focusing effect, and the beam waist size ω f The minimum, the focusing effect is the best; to guide the grinding work of capillary fiber, control the length of the hollow part in the capillary fiber during grinding;

[0045] Wherein, ω0 is the radius of the Gaussian beam at the beam waist, n1 is the refractive index of the single-mode fiber and the multi-mode fiber, λ is the center wavelength of the input Gaussian light beam; n2 is the refractive index of the medium.

[0046] In another aspect, the present application provides a composite sensor prepared by the optical lens fiber preparation method of any one of claims 1-8, the composite sensor comprising a first single-mode optical fiber, a second single-mode optical fiber, a hollow-core optical fiber, a capillary optical fiber, and a multi-mode optical fiber, wherein,

[0047] One end of the first single-mode optical fiber is fused to one end of the second single-mode optical fiber, and an air gap is formed between the first single-mode optical fiber and the second single-mode optical fiber;

[0048] One end of the second single-mode optical fiber is heat-fused to form a fiber lens in the shape of a semispherical ball, and is inserted into the capillary optical fiber;

[0049] The end of the capillary optical fiber distal to the second single-mode optical fiber is fused to the multi-mode optical fiber, and an air cavity is formed between the fiber lens and the multi-mode optical fiber.

[0050] In yet another aspect, the present application provides a pressure guide wire comprising the composite sensor of claim 9, further comprising a head end, a spring hose, a pressure window, a first connecting tube, and a second connecting tube, wherein,

[0051] The head end, the spring hose, the first connecting tube, and the second connecting tube are connected in sequence;

[0052] The pressure window is provided on the first connecting tube;

[0053] The composite sensor is installed inside the pressure guide wire.

[0054] The optical lens fiber preparation method, the composite sensor, and the pressure guide wire of the present application have the following beneficial effects over the prior art:

[0055] (1) By means of cutting, etching, fusing, and grinding processes, a double-F-P cavity temperature and pressure composite sensor with high performance can be prepared to achieve composite measurement of two parameters of temperature and pressure, which avoids the problem of damage to the optical fiber itself caused by the femtosecond laser processing process, and greatly reduces the manufacturing cost of the sensor;

[0056] (2) By increasing the structure of the fiber lens to shape the light beam, the fiber lens can focus the incident light beam through its curvature, so that the irradiation area of the light beam on the diaphragm is reduced and the light intensity is increased, and the focusing action can improve the efficiency of the interaction between the light and the diaphragm;

[0057] (3) By increasing the structure of the fiber lens to shape the light beam, when the diaphragm is deformed due to external temperature or pressure, its position relative to the optical fiber will also change; since the shape of the fiber lens is similar to that of a convex lens, it can collect the light reflected back, even in the case of displacement of the diaphragm;

[0058] (4) By increasing the structure of the fiber lens to shape the light beam, due to the focusing and light collection ability of the fiber lens, the reflected light can be more effectively coupled back into the single-mode fiber even at a long cavity length; this means that even if the distance between the diaphragm and the fiber end face changes, the sensor can still capture sufficient light power to produce an effective interference signal. In summary, the design of the fiber lens can collect and focus the reflected light, maintaining a high coupling efficiency even in the case of diaphragm deformation. In this way, the sensor can work at a longer cavity length while maintaining an effective interference signal, thereby improving the sensitivity and accuracy of the measurement. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, a brief introduction will be given below to the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0060] Figure 1 Structure diagram of the optical lens fiber of the present application;

[0061] Figure 2 Structure diagram of the fiber focusing structure of the present application;

[0062] Figure 3 Structure diagram of the pressure guide wire of the present application;

[0063] Figure 4 Flowchart of etching, fusion and cutting of the single-mode fiber and the coreless fiber of the optical lens fiber of the present application;

[0064] Figure 5 Flowchart of preparation of the fiber lens and connection with the capillary fiber of the coreless fiber of the optical lens fiber of the present application;

[0065] Figure 6 Flowchart of cutting, grinding and cleaning of the capillary fiber of the optical lens fiber of the present application;

[0066] Figure 7 Flowchart of cutting, grinding and fusion with the capillary fiber of the multi-mode fiber of the optical lens fiber of the present application;

[0067] In the figure: 1, first single-mode fiber; 2, second single-mode fiber; 3, coreless fiber; 31, fiber lens; 4, capillary fiber; 5, multi-mode fiber; 100, air gap; 200, air cavity; 101, head end; 102, spring hose; 103, pressure window; 104, first connecting tube; 105, second connecting tube. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0069] As shown in Figure 2 The optical lens fiber of the present application comprises a first single-mode optical fiber 1, a second single-mode optical fiber 2, a coreless optical fiber 3, an optical fiber lens 31, a capillary optical fiber 4 and a multi-mode optical fiber 5.

[0070] The composite sensor of the present application comprises the above optical lens fiber, wherein one end of the first single-mode optical fiber 1 is fused with one end of the second single-mode optical fiber 2, and an air gap 100 is formed between the first single-mode optical fiber 1 and the second single-mode optical fiber 2; one end of the second single-mode optical fiber 2 is heat-fused to form a semi-spherical structure of the optical fiber lens 31, and is inserted into the capillary optical fiber 4; the end of the capillary optical fiber 4 away from the second single-mode optical fiber 2 is fused with the multi-mode optical fiber 5, and an air cavity 200 is formed between the optical fiber lens 31 and the multi-mode optical fiber 5.

[0071] Specifically, the inner diameter of the capillary optical fiber 4 is 103 μm, the outer diameter is 200 μm, and the diameter of the multi-mode optical fiber 5 is 200 μm.

[0072] Specifically, the composite sensor is a temperature and pressure sensor, wherein the temperature measurement is realized by an F-P interference cavity based on the single-mode optical fiber, and the cavity is formed by the air gap 100 between the first single-mode optical fiber 1 and the second single-mode optical fiber 2, and the interface between the second single-mode optical fiber 2 and the capillary optical fiber 4.

[0073] Specifically, the pressure measurement is realized by an F-P interference cavity based on the capillary optical fiber 4, and the cavity is the air cavity 200, which is composed of the end face of the optical fiber lens 31, the capillary optical fiber 4 and the multi-mode optical fiber 5.

[0074] As shown in Figure 1 The pressure guide wire of the present application comprises the above composite sensor, and further comprises a head end 101, a spring hose 102, a pressure window 103, a first connecting pipe 104 and a second connecting pipe 105, wherein the head end 101, the spring hose 102, the first connecting pipe 104 and the second connecting pipe 105 are connected in sequence; the pressure window 103 is provided on the first connecting pipe 104; and the composite sensor is installed inside the pressure guide wire.

[0075] As described above, the composite sensor of the application has the advantages of small size, resistance to electromagnetic interference, biocompatibility, etc., and is applied to an interventional pressure guide wire, thereby increasing the accuracy and reliability of pressure monitoring in the process of clinical interventional treatment and being beneficial to improving the operation precision.

[0076] Specifically, the head end 101 is a hemispherical round head, which prevents the guide wire from damaging the inner wall of the blood vessel during the pushing process;

[0077] Specifically, the spring hose 102 can not only be used for buffering, but also can be bent to the required angle to facilitate delivery into the blood vessel;

[0078] Specifically, the pressure window 103 is used for pressure detection, which avoids the problem of damage of the composite sensor caused by the too long connecting pipe.

[0079] Specifically, the structure of the optical fiber lens 31 is increased to shape the light beam. Due to the focusing and light collecting ability of the optical fiber lens 31, even under long cavity length, the reflected light can be more effectively coupled back into the single-mode optical fiber; this means that even if the distance between the sensor diaphragm and the optical fiber end face changes, the sensor can still capture enough optical power to produce an effective interference signal.

[0080] In summary, the design of the optical fiber lens 31 can collect and focus the reflected light, and maintain a high coupling efficiency even in the case of diaphragm deformation. In this way, the sensor can work under a longer cavity length while maintaining an effective interference signal, thereby improving the sensitivity and accuracy of the measurement.

[0081] As shown in Figures 4 to 7 the optical lens optical fiber preparation method of the application comprises the following steps:

[0082] S1, preparing a first single-mode optical fiber 1 and a second single-mode optical fiber 2, and fusing the first single-mode optical fiber 1 and the second single-mode optical fiber 2 to form an air gap 100,

[0083] Specifically, it comprises: etching, placing two cut single-mode optical fibers in a hydrofluoric acid solution for chemical etching treatment, and the two single-mode optical fibers are respectively marked as a first single-mode optical fiber 1 and a second single-mode optical fiber 2.

[0084] S2, fusing the end of the second single-mode optical fiber 2 away from the first single-mode optical fiber 1 with a coreless optical fiber 3, in this step, a fiber fusion machine is used;

[0085] Specifically, it comprises: cutting, under the assistance of a microscope, precisely positioning the fused second single-mode optical fiber 2, and then cutting using a fiber cutting knife to reduce the length of the single-mode optical fiber;

[0086] Fusion, precisely fusion the end of the second single-mode optical fiber 2 after cutting with the coreless optical fiber 3 to realize seamless connection between the two optical fibers;

[0087] Cutting, under the assistance of a microscope, precisely position the coreless optical fiber 3 after fusion, and then cut using an optical fiber cutter to reduce the length of the coreless optical fiber 3.

[0088] S3, arc discharge the end of the coreless optical fiber 3 using an optical fiber fusion machine to form a lens, constituting an optical fiber lens 31, the optical fiber lens 31 being a semi-circular spherical structure;

[0089] S4, place the coreless optical fiber 3 and the capillary optical fiber 4 on the optical fiber fusion machine, and insert the lens end of the coreless optical fiber 3 into the inner cavity of the capillary optical fiber 4, and discharge and fuse;

[0090] Specifically, it includes: fixing the coreless optical fiber 3 and the capillary optical fiber 4 to the corresponding end of the optical fiber fusion machine respectively;

[0091] By manual operation, precisely insert the optical fiber lens 31 of the coreless optical fiber 3 into the inner cavity of the capillary optical fiber 4;

[0092] After the insertion is completed, use the electric shock discharge function of the optical fiber fusion machine to realize precise fusion of the coreless optical fiber 3 and the capillary optical fiber 4;

[0093] Wherein, the diameter of the single-mode optical fiber is 125μm, and the diameter of the capillary optical fiber 4 is 130μm.

[0094] Specifically, it further includes: cutting, cutting the end of the fused capillary optical fiber 4 away from the optical fiber lens 31 using a cutter to reduce the length of the capillary optical fiber 4;

[0095] Grinding, after the cutting of the capillary optical fiber 4 is completed, finely grinding the cutting end using a grinding machine,

[0096] Cleaning, after the capillary optical fiber 4 is ground, clean the optical fiber using an ultrasonic cleaning machine; this step is to remove the optical fiber powder that may be generated during the grinding process, to ensure that the optical fiber surface is free of residues, thereby improving the cleanliness of the hollow part inside the capillary optical fiber 4.

[0097] S5, prepare a multi-mode optical fiber 5, and fuse the multi-mode optical fiber 5 with the capillary optical fiber 4 through an optical fiber fusion machine, and form an air cavity 200;

[0098] Specifically, it includes: cutting, cutting the multi-mode optical fiber 5 using a cutter to increase the flatness of the end face of the multi-mode optical fiber 5;

[0099] Fusion, after cleaning the single mode fiber with capillary fiber 4 and cutting the multi-mode fiber 5, the two ends are fixed in the fiber fusion machine, manual feeding makes the capillary fiber 4 and the multi-mode fiber 5 contact; after contact, the electrode discharge of the fiber fusion machine makes the multi-mode fiber 5 and the capillary fiber 4 fuse with each other to form the fiber F-P cavity, that is, the air cavity 200.

[0100] S6, the end face of the multi-mode fiber 5 is cut and polished to form a sensitive diaphragm;

[0101] Specifically, it includes cutting, cutting the fused multi-mode fiber 5 to reduce the length of the multi-mode fiber 5;

[0102] Polishing: using a grinder to polish the end face of the cut multi-mode fiber 5, so that the multi-mode fiber 5 forms a sensitive diaphragm.

[0103] Wherein, in the preparation process, the length of the capillary fiber 4 is controlled by the fiber lens focusing theory. This step aims to further reduce the length of the capillary fiber 4 and significantly improve the flatness of its end face. By precisely controlling the polishing process, the fiber end face is ensured to reach the required smoothness and parallelism, thereby optimizing the optical performance of the fiber and ensuring the reliability of the connection.

[0104] In step S1, the first single mode fiber 1 and the second single mode fiber 2 are cut and placed in a hydrofluoric acid solution for chemical etching treatment, wherein the concentration of the hydrofluoric acid solution is 40%, and the etching time is 5 minutes;

[0105] As mentioned above, in the structure of the single mode fiber, the chemical composition of the core and the cladding is usually slightly different, the core is usually made of doped quartz glass such as germanium-doped to increase the refractive index, while the cladding is high-purity quartz glass. The difference in composition makes the etching rate of the core and the cladding different when they are in contact with the hydrofluoric acid solution, and the etching rate of the core is slightly faster than that of the cladding; therefore, it is necessary to accurately control the concentration of the hydrofluoric acid solution and the etching time.

[0106] The discharge intensity of the first single mode fiber 1 and the second single mode fiber 2 during fusion is 85bit, and the discharge time is 1500ms;

[0107] As mentioned above, after fusion, the micro air gap 100 between the first single mode fiber 1 and the second single mode fiber 2 acts as the first mirror, when the light source enters this interference cavity, it will be reflected at both ends of the micro air gap 100, that is, the end of the first single mode fiber 1 and the inner surface of the second single mode fiber 2, and then interference occurs.

[0108] Specifically, when preparing the fiber lens 31 of the coreless fiber 3, the heat generated by the electric arc will melt the glass material at the end 204 of the coreless fiber;

[0109] The melting part of the end of the coreless optical fiber 3 forms the required curvature during the cooling process, thereby forming a lens; this lens can focus the incident light and improve the coupling efficiency of the reflected light.

[0110] The grinding of the multimode optical fiber 5 includes the following steps:

[0111] S61, coarsely grinding the end face of the multimode optical fiber 5 using a grinding paper with a roughness of 5 um, and synchronously monitoring the remaining length of the multimode optical fiber 5 until the length of the multimode optical fiber 5 is ground to 20 um, and using a dust-free paper to wipe off the residues generated during the grinding process;

[0112] S62, grinding the multimode optical fiber 5 using a grinding paper with a roughness of 1 um to grind the length of the multimode optical fiber 5 to below 5 um to form a sensitive diaphragm.

[0113] As shown in the fiber lens focusing theory, the steps for controlling the length of the capillary optical fiber 4 are as follows: Figure 3

[0114] P1, by using the light generated by the ABCD matrix light source for trajectory tracking analysis, assuming that the light generated by the light source is a Gaussian beam, using the matrix M LFO to associate the output light of the single-mode optical fiber and the fiber lens;

[0115] P2, obtaining the ABCD matrix of the Gaussian beam propagating in the coreless optical fiber 3, the fiber lens 31 and the air cavity 200, and obtaining the system matrix M LFO ;

[0116] P3, combining steps P1 and P2, finding the best working distance d work of the fiber lens, i.e. the distance between the output beam waist of the output beam and the tip of the optical lens fiber;

[0117] P4, solving the best working distance d work , combining the matrix M LFO to obtain the beam waist size ω f of the output beam of the fiber lens, and the focusing effect is best when the beam waist size ω f of the beam is smallest;

[0118] PS, by judging the focusing effect, guiding the grinding work of the capillary optical fiber 4.

[0119] In the formula for associating the output light of the single-mode optical fiber and the fiber lens in the matrix M LFO , the formula is as follows,

[0120]

[0121] where r​LFO and r SMF r' is the position of the light ray measured from the center axis of the optical fiber, r LFO and r' SMF is the slope of the light ray relative to the center axis of the optical fiber.

[0122] The ABCD matrix of the Gaussian beam propagating in the hollow-core optical fiber 3, the fiber lens 31 and the air cavity 200 is:

[0123]

[0124] The system matrix M LFO can be obtained from the above formula, i.e. LFO M HCF M lens M CSF ;

[0125]

[0126] wherein n1 is the refractive index of the single-mode optical fiber and the multi-mode optical fiber 5; d CSF is the length of the hollow-core optical fiber 3, which does not include the length of the fiber lens 31; R is the radius of the fiber lens 31; d work is the best working distance of the fiber lens 31; M HCF is the ABCD matrix propagating in the hollow-core optical fiber 3; M lens is the ABCD matrix propagating in the fiber lens 31; M CSF is the ABCD matrix propagating in the air cavity 200; A, B, C, D are the light transmission matrix, and LFO is the optical lens fiber.

[0127] The best focusing range d work is solved by the following steps:

[0128] When the curvature radius of the output beam is infinite, as the following formula,

[0129]

[0130] wherein, a is the beam parameter, representing the beam divergence characteristic; λ is the wavelength of light; n2 is the refractive index of the medium; ω0 is the radius of the Gaussian beam at the beam waist; A, B, C, D are the light transmission matrix, and LFO is the optical lens fiber; R is the radius of the fiber lens (31).

[0131] The solution of d work is obtained as the following formula:

[0132]

[0133] Wherein, ω0 is the beam waist radius of the input beam from the single-mode fiber, and λ is the central wavelength of the input Gaussian beam.

[0134] By d work and M LFO The d work The beam waist size ω f of the output beam of the optical lens fiber can be obtained.

[0135]

[0136] When d work works in the range of d0, the output beam has a focusing effect, and the beam waist size ω f is the smallest, and the focusing effect is the best at this time; the incident light is focused on the diaphragm by the lens fiber, which can increase the optical power density of the light beam on the diaphragm, thereby improving the sensitivity of the sensor to pressure changes. This has a guiding effect on the subsequent grinding of the capillary fiber 4, that is, the length of the hollow part inside the capillary fiber 4 is controlled to be around d1 during grinding;

[0137] Wherein, ω0 is the beam waist radius of the input beam from the single-mode fiber, and λ is the central wavelength of the input Gaussian beam.

[0138] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for fabricating an optical lens fiber, characterized in that: Includes the following steps: S1. Prepare a first single-mode fiber (1) and a second single-mode fiber (2), and fusion splice the first single-mode fiber (1) and the second single-mode fiber (2) to form an air gap (100). S2. Splice the end of the second single-mode fiber (2) away from the first single-mode fiber (1) with the coreless fiber (3). S3. Use a fiber optic fusion splicer to perform arc discharge on the end of the coreless optical fiber (3) to form a lens, constituting an optical fiber lens (31). The optical fiber lens (31) has a hemispherical structure. S4. Place the coreless optical fiber (3) and the capillary optical fiber (4) on the optical fiber fusion splicer, insert the lens end of the coreless optical fiber (3) into the inner cavity of the capillary optical fiber (4), and perform discharge fusion splicing. S5. Prepare a multimode optical fiber (5), and fuse the multimode optical fiber (5) with the capillary optical fiber (4) using an optical fiber fusion splicer to form an air cavity (200). S6. The end face of the multimode optical fiber (5) is cut and ground to form a sensitive diaphragm; In the fabrication process, the length of the capillary fiber (4) is controlled by the focusing theory of fiber optic lenses.

2. The method for fabricating optical lens fibers as described in claim 1, characterized in that: In step S1, the first single-mode fiber (1) and the second single-mode fiber (2) are cut and placed in a hydrofluoric acid solution for chemical etching treatment, wherein the concentration of the hydrofluoric acid solution is 40% and the etching time is 5 minutes. The discharge intensity of the first single-mode fiber (1) and the second single-mode fiber (2) during fusion splicing is 85 bits and the discharge time is 1500ms.

3. The method for fabricating optical lens fibers as described in claim 1, characterized in that: The polishing of the multimode optical fiber (5) includes the following steps: S61. Use polishing paper with a roughness of 5 μm to coarsely polish the end face of the multimode fiber (5), and monitor the remaining length of the multimode fiber (5) simultaneously until the length of the multimode fiber (5) is polished to 20 μm, and use lint-free paper to wipe away the residue generated during the polishing process. S62. The multimode optical fiber (5) is polished with polishing paper with a roughness of 1 μm to reduce its length to less than 5 μm so as to form a sensitive film.

4. The method for fabricating optical lens fibers according to any one of claims 1 to 3, characterized in that, The steps for controlling the length of the capillary fiber (4) using the focusing theory of fiber optic lenses are as follows: P1. Trajectory tracking analysis is performed using light generated by an ABCD matrix light source. Assuming the light beam is a Gaussian beam, matrix M is used. LFO To correlate the single-mode fiber with the output light of the fiber lens (31); P2. Obtain the ABCD matrix of the Gaussian beam propagating in the coreless optical fiber (3), the optical fiber lens (31), and the air cavity (200), and calculate the system matrix M. LFO ; P3. Combining steps P1 and P2, find the optimal working distance d of the fiber optic lens (31) for the beam. work That is, the distance between the output beam waist of the output beam and the tip of the optical fiber of the optical lens; P4. Regarding the optimal working distance d work Solve by combining matrix M LFO Obtain the beam waist size ω of the beam output by the fiber optic lens (31). f ; P5. By judging the focusing effect, guide the polishing work of the capillary optical fiber (4).

5. The method for fabricating optical lens fibers as described in claim 4, characterized in that: In matrix M LFO The formula for relating the output light of the single-mode fiber and the fiber lens (31) is as follows. Where, r LFO and r SMF To measure the position of the light ray from the central axis of the optical fiber, r′ LFO and r′ SMF The slope of the light ray relative to the central axis of the optical fiber.

6. The method for fabricating optical lens fibers as described in claim 5, characterized in that, The ABCD matrix of the Gaussian beam propagating in the coreless optical fiber (3), the optical fiber lens (31), and the air cavity (200) is as follows: The system matrix M can be obtained from the above formula. LFO M LFO =M HCF M lens M CSF ; Where n1 is the refractive index of single-mode fiber and multimode fiber; d CSF d is the length of the coreless optical fiber (3), excluding the length of the optical fiber lens (31); R is the radius of the optical fiber lens (31); d work The optimal working distance for the fiber optic lens (31); M HCF M is the ABCD matrix propagating in the coreless optical fiber (3); lens M is the ABCD matrix propagating in the fiber optic lens (31); CSF ABCD matrix propagating in the air cavity (200); A, B, C, and D are light transmission matrices, and LFO is an optical lens fiber.

7. The method for fabricating optical lens fibers as described in claim 6, characterized in that, For the optimal focusing range d work The steps to solve the problem are as follows: When the radius of curvature of the output beam is infinitely large, as shown in the following formula, in, a is the beam parameter, characterizing the beam divergence characteristics; λ is the wavelength of light; n2 is the refractive index of the medium; ω0 is the radius of the Gaussian beam at the beam waist; A, B, C, and D are the light transmission matrices; LFO is the optical lens fiber; π is pi; and R is the radius of the fiber lens (31). Solving for it yields d. work The solution is shown in the following formula; Where ω0 is the beam waist radius from the single-mode fiber input beam, and λ is the center wavelength of the input Gaussian beam.

8. The method for fabricating optical lens fibers as described in claim 7, characterized in that: via d work and M LFO The d can be obtained work The beam waist ω of the optical beam output from the optical lens fiber f ; When d work When operating within the d0 range, it has a focusing effect on the output beam, and the beam waist size ω f When the minimum value is reached, the focusing effect is the best; this guides the polishing of the capillary fiber (4), and during polishing, the length of the hollow part inside the capillary fiber (4) is controlled to be around d1. Where ω0 is the radius of the Gaussian beam at the beam waist, n1 is the refractive index of the single-mode fiber and the multimode fiber (5), λ is the center wavelength of the input Gaussian beam, and n2 is the refractive index of the medium.

9. A composite sensor, characterized in that, The composite sensor is fabricated using the optical lens fiber fabrication method described in any one of claims 1 to 8. The composite sensor comprises a first single-mode fiber (1), a second single-mode fiber (2), a coreless fiber (3), a capillary fiber (4), and a multimode fiber (5), wherein... One end of the first single-mode fiber (1) is fused to one end of the second single-mode fiber (2), and the air gap (100) is formed between the first single-mode fiber (1) and the second single-mode fiber (2); One end of the second single-mode fiber (2) is thermally fused to form a hemispherical structure of the fiber lens (31) and inserted into the capillary fiber (4); The end of the capillary fiber (4) away from the second single-mode fiber (2) is fused to the multimode fiber (5), and the air cavity (200) is formed between the fiber lens (31) and the multimode fiber (5).

10. A pressure guidewire, characterized in that: The composite sensor as described in claim 9 further includes a head end (101), a spring hose (102), a pressure window (103), a first connecting tube (104), and a second connecting tube (105), wherein, The head end (101), spring hose (102), first connecting pipe (104), and second connecting pipe (105) are connected in sequence; The pressure window (103) is opened on the first connecting pipe (104); The composite sensor is installed inside the pressure guide wire.

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