A multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring

Abstract

The present invention discloses a multi-resonance layer hollow optical fiber for carbon dioxide gas monitoring, and relates to the field of optical fiber communication technology. The present invention includes an outer cladding, an inner cladding and an air core region in sequence from the outside to the inside along the radial direction of the optical fiber, and a plurality of first nested tube units are arranged between the outer cladding and the inner cladding, and the plurality of first nested tube units are distributed in an annular shape and are equidistant, and the first nested tube units are tangent to the outer cladding and the inner cladding respectively. The present invention realizes efficient transmission of light of a specific wavelength through an optimized resonant structure, and enhances the interaction with gas molecules through its hollow structure. The optical fiber has the characteristics of low loss, near-zero dispersion and anti-bending, and is suitable for monitoring carbon dioxide gas molecules. The multi-resonance structure of the optical fiber enables it to maintain good optical transmission characteristics in a wide spectrum range, and is particularly suitable for gas monitoring methods such as laser absorption spectroscopy and Raman spectroscopy.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber communication, in particular to a multi-resonance layer hollow optical fiber used for carbon dioxide gas monitoring. Background Art

[0002] The application of fiber optic sensors in gas monitoring has made significant progress. Traditional optical fibers use the principle of total internal reflection to transmit optical signals, but because light propagates in the solid core, the interaction path with the gas is limited, and the monitoring sensitivity is limited. To overcome this problem, hollow fiber technology came into being. The core of the hollow fiber is filled with air or gas, and the optical signal can fully contact the target gas when propagating in the core, thereby enhancing the interaction between light and gas molecules and improving monitoring sensitivity.

[0003] Among them, hollow-core anti-resonant fiber (HC-ARF) has become the research focus in the field of carbon dioxide gas monitoring due to its low loss and efficient light transmission characteristics. HC-ARF fiber is based on the anti-resonance effect. By designing an anti-resonance structure of a specific thickness in the fiber cladding, it suppresses the leakage of optical signals and achieves efficient light transmission. Compared with traditional optical fibers, HC-ARF can not only significantly reduce the interaction loss between light and materials, but also enhance the interaction between light and gas in the hollow core.

[0004] However, there are still some challenges in the application of existing hollow antiresonant optical fibers in gas monitoring. For example, in practical applications, how to further reduce the loss of optical fibers, improve the compatibility of optical fibers with light of different wavelengths, and how to balance the transmission performance and structural complexity of optical fibers in multi-resonance layer structures still need in-depth research. To this end, we propose a multi-resonance layer hollow optical fiber for carbon dioxide gas monitoring. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring, which can significantly improve the accuracy and sensitivity of gas detection by enhancing the interaction between light and gas through the multi-resonance layer hollow-core anti-resonance optical fiber.

[0006] To achieve the above object, the present invention provides the following technical solution: a multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring, which includes an outer cladding, an inner cladding and an air core region from the outside to the inside along the radial direction of the optical fiber, and a plurality of first nested tube units are arranged between the outer cladding and the inner cladding, and the plurality of first nested tube units are distributed in an annular shape with equal spacing, and the first nested tube units are tangent to the outer cladding and the inner cladding respectively;

[0007] The inner cladding includes an anti-resonance layer and a plurality of second nested tube units, the plurality of second nested tube units are arranged in a ring shape to form an air core region, the plurality of second nested tube units are arranged at equal distances, and there is a gap between two adjacent second nested tube units, the anti-resonance layer is located between the first nested tube unit and the second nested tube unit, and is tangent to both the first nested tube unit and the second nested tube unit.

[0008] Furthermore, the substrate materials of the outer cladding layer, the plurality of first nested tube units, the anti-resonance layer and the plurality of second nested tube units are all quartz glass, and the refractive index thereof is 1.4192.

[0009] Furthermore, the number of the first nested tube units is six, and the first nested tube unit includes a first microcapillary tube tangent to the inner cladding, a second microcapillary tube is inscribed in the inner wall of the first microcapillary tube, a third microcapillary tube is inscribed in the inner wall of the second microcapillary tube, and the first microcapillary tube, the second microcapillary tube and the third microcapillary tube are all tangent to the outer cladding.

[0010] Furthermore, the pore size d of the first microcapillary is 4 = 20 μm, the pore size of the second microcapillary d 5 = 15 μm, the pore size of the third microcapillary d 6 =9μm.

[0011] Furthermore, the number of the second nested tube units is six, and the second nested tube units include a fourth microcapillary that is externally cut with the air core region, a fifth microcapillary is internally cut with the inner wall of the fourth microcapillary, a sixth microcapillary is internally cut with the inner wall of the fifth microcapillary, and the fourth microcapillary, the fifth microcapillary and the sixth microcapillary are all internally cut with the inner cladding.

[0012] Furthermore, the pore size d of the fourth microcapillary is 1 = 15 μm, the pore size of the fifth microcapillary d 2 = 12 μm, the pore size of the sixth microcapillary d 3 =6μm.

[0013] Furthermore, the thickness of the first microcapillary, the second microcapillary, and the third microcapillary are all t=0.744 μm.

[0014] Further, the thickness of the first microcapillary, the second microcapillary, the third microcapillary, the fourth microcapillary, the fifth microcapillary and the sixth microcapillary are all t, and the thickness t satisfies the anti-resonance condition:

[0015]

[0016] In the formula, t represents the thickness of the dielectric tube, λ represents the designed working wavelength, and n 1 and n0 are the refractive index of the dielectric tube material and the refractive index of air respectively, and m is an integer.

[0017] Furthermore, the outer cladding is a hollow cylindrical layer with a wall thickness of t 2 =30μm, the anti-resonance layer is a micro-ring capillary, and its thickness is t 1 =3μm.

[0018] Furthermore, the inner regions of the outer cladding, the inner cladding, the plurality of first nested tube units, the antiresonance layer and the plurality of second nested tube units are all filled with air, serving as air holes in the outer ring of the air core region, and the air core region is also filled with air, and the refractive index of the air is 1.

[0019] The present invention has at least the following beneficial effects:

[0020] The present invention meets the anti-resonance reflection waveguide (ARROW) principle in structural design and uses multiple anti-resonance layers to improve the performance parameters during transmission, so that it has the characteristics of loss, near-zero dispersion and anti-bending, and is suitable for monitoring carbon dioxide gas molecules. Compared with the prior art, the present invention is structurally circular, easy to prepare and the preparation material is common quartz glass, and the cost is extremely low; in terms of performance parameters, the present invention has a limiting loss of less than 10 in the range of 2.0~3.2μm in the mid-infrared band. -5 dB / m, which is much lower than the existing single-mode optical fiber, achieving low-loss transmission; secondly, the present invention also has a transmission loss of up to 10 -13 The dispersion is close to zero and the nonlinear coefficient in the above transmission band is as low as 0.07503 (W·m) -1 , so that the optical fiber can obtain greater transmission power to achieve long-distance transmission; and when the bending radius is 7cm, it can reach 10 -4 The bending loss of dB / m indicates that the present invention has good anti-bending performance.

[0021] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic cross-sectional view of the overall structure of the optical fiber of the present invention;

[0023] Figure 2 It is the fundamental mode diagram and three-dimensional height representation diagram of the optical fiber cross section in the present invention;

[0024] Figure 3 It is a schematic diagram of the relationship between the limiting loss of the fundamental mode of the optical fiber and the change of the wavelength in the present invention;

[0025] Figure 4 It is a schematic diagram of the relationship between the fundamental mode dispersion of optical fiber and the wavelength in the present invention;

[0026] Figure 5 This is a schematic diagram of the relationship between the fundamental mode mode field area of ​​the optical fiber and the wavelength in the present invention;

[0027] Figure 6 It is a schematic diagram of the relationship between the nonlinear effect of the optical fiber fundamental mode and the wavelength in the present invention;

[0028] Figure 7 A graph showing the relationship between the bending loss and the bending radius when the optical fiber is bent in the X direction at a wavelength of 3 μm and an electric field distribution graph when the optical fiber is bent in the X direction;

[0029] Figure 8 A graph showing the relationship between the bending loss and the bending radius when the optical fiber is bent in the Y direction at a wavelength of 3 μm and an electric field distribution graph when the optical fiber is bent in the Y direction;

[0030] Fig. 9 is a cross-sectional schematic diagram of the inner cladding structure of the present invention;

[0031] Fig.10 It is a cross-sectional schematic diagram of the first nested tube unit structure of the present invention.

[0032] Reference numerals:

[0033] 1. Outer cladding; 2. Inner cladding; 3. Air core region; 4. First nested tube unit; 41. First microcapillary; 42. Second microcapillary; 43. Third microcapillary; 5. Anti-resonance layer; 6. Second nested tube unit; 61. Fourth microcapillary; 62. Fifth microcapillary; 63. Sixth microcapillary. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0035] See also Figure 1-Figure 10 The present invention provides a technical solution: a multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring, which includes an outer cladding 1, an inner cladding 2 and an air core region 3 from outside to inside in the radial direction of the optical fiber, and a plurality of first nested tube units 4 are arranged between the outer cladding 1 and the inner cladding 2, and the plurality of first nested tube units 4 are distributed in an annular manner with equal spacing, and the first nested tube units 4 are tangent to the outer cladding 1 and the inner cladding 2 respectively;

[0036] The inner cladding 2 includes an anti-resonance layer 5 and a plurality of second nested tube units 6. The plurality of second nested tube units 6 are arranged in a ring shape to form an air core region 3. The plurality of second nested tube units 6 are arranged at equal distances, and there is a gap between two adjacent second nested tube units 6. The anti-resonance layer 5 is located between the first nested tube unit 4 and the second nested tube unit 6, and is tangent to both the first nested tube unit 4 and the second nested tube unit 6.

[0037] According to the technical solution of this embodiment, the number of the first nested tube units 4 is six, and the first nested tube units 4 include a first microcapillary 41 circumscribed with the inner cladding 2, a second microcapillary 42 is inscribed in the inner wall of the first microcapillary 41, a third microcapillary 43 is inscribed in the inner wall of the second microcapillary 42, and the first microcapillary 41, the second microcapillary 42 and the third microcapillary 43 are all tangent to the outer cladding 1, and the first nested tube units 4 are mainly used to support the outer cladding 1 and the inner cladding 2.

[0038] Furthermore, if Fig.10 As shown, the pore size d of the first microcapillary 41 is 4 = 20 μm, the pore size d of the second microcapillary 42 5 =15 μm, the pore size d of the third microcapillary 43 6 =9μm.

[0039] According to the technical solution of this embodiment, the second nested tube unit 6 is arranged as the anti-resonance layer 5 of the optical fiber, so as to improve the transmission performance of the optical signal, such as reducing loss and dispersion, thereby improving the transmission quality and stability of the optical signal. The number of the second nested tube units 6 is six, and the second nested tube units 6 include a fourth microcapillary 61 externally cut with the air core region 3, the inner wall of the fourth microcapillary 61 is inscribed with a fifth microcapillary 62, the inner wall of the fifth microcapillary 62 is inscribed with a sixth microcapillary 63, and the fourth microcapillary 61, the fifth microcapillary 62 and the sixth microcapillary 63 are all inscribed with the inner cladding 2.

[0040] Furthermore, if Fig. 9 As shown, the pore size d of the fourth microcapillary 61 is 1 =15 μm, the pore size d of the fifth microcapillary 62 2 =12 μm, the pore size d of the sixth microcapillary 63 3 =6μm, the microcapillaries inside the nested tube unit can help optimize the transmission efficiency of optical signals. The mutual influence and interference between different microcapillaries are small, thereby reducing transmission losses. In addition, through the design of the nested tube unit structure, the bandwidth of the hollow-core optical fiber can also be increased, thereby supporting a wider range of frequency signal transmission.

[0041] According to the technical solution of this embodiment, the thickness of the first microcapillary 41, the second microcapillary 42, the third microcapillary 43, the fourth microcapillary 61, the fifth microcapillary 62 and the sixth microcapillary 63 are all t to meet the anti-resonance condition:

[0042]

[0043] In the formula, t represents the thickness of the dielectric tube, λ represents the designed working wavelength, and n 1 and n 0 are the refractive index of the dielectric tube material and the refractive index of air respectively, and m is an integer.

[0044] According to the technical solution of this embodiment, the outer cladding 1 is a hollow cylindrical shape with a wall thickness of t 2 =30μm, the anti-resonance layer 5 is a micro-ring capillary, and its thickness is t 1 =3μm, the outer cladding 1 serves as the outer protective layer of the hollow-core optical fiber, which can protect the internal structure from the influence of the external environment, such as mechanical damage, chemical corrosion, etc. The micro-annular capillary structure of the anti-resonance layer 5 helps to optimize the mode coupling process of the optical signal, so that different types of optical signals can be transmitted more efficiently without interference.

[0045] According to the technical solution of this embodiment, the base materials of the outer cladding 1, the plurality of first nested tube units 4, the antiresonance layer 5 and the plurality of second nested tube units 6 are all quartz glass, and its refractive index is 1.4192. Silica glass is a high-quality optical material with good refractive index and transparency, which is very beneficial for the transmission and collection of optical signals. The refractive index range is also suitable for the production of composite optical fibers, which can ensure that the propagation speed of the optical signal inside the fiber is the same as that outside, thereby realizing high-speed and long-distance data transmission.

[0046] According to the technical solution of this embodiment, the inner regions of the outer cladding 1, the inner cladding 2, the plurality of first nested tube units 4, the antiresonance layer 5 and the plurality of second nested tube units 6 are all filled with air, and the air holes in the outer ring of the air core region 3 are also filled with air, and the refractive index of air is 1. The design of filling the interior with air and adopting an air refractive index less than that of silica glass can improve the propagation efficiency of visible light in the optical fiber, reduce the difference between refraction and reflection, and reduce the dispersion of the optical fiber, thereby improving the transmission performance and reliability of the optical fiber.

[0047] For the technical solution of this embodiment, the finite element simulation software COMSOL Multiphysics is used for simulation. By setting the truncation boundary in the simulation area, the wave impedance of the medium is completely matched with the wave impedance of the adjacent medium. This design allows the incident wave to pass through the interface without reflection and enter the PML, thereby achieving lossless transmission of energy. The introduction of PML is mainly to solve the problem of the difference between the optical fiber model in the simulation environment and the actual optical fiber environment. By setting appropriate boundary conditions, the environmental difference between the two is effectively eliminated, making the simulation results closer to the actual situation.

[0048] The realization principle of the perfect matching layer is to set a boundary condition with the same material as the cladding and matching wave impedance on the outside of the outer cladding 1 of the optical fiber. Therefore, it can be regarded as a non-reflective absorption layer. When the light beam enters the perfect matching layer, it will not be reflected back immediately, but will gradually attenuate until it is finally absorbed. This non-reflective feature makes the perfect matching layer an ideal boundary condition in simulation analysis, especially when simulating and analyzing large mode area optical fibers, the use of the perfect matching layer can significantly improve the accuracy of the simulation results.

[0049] Next, the technical solution of the present invention is further described in conjunction with specific embodiments:

[0050] This embodiment uses finite element simulation software COMSOL Multiphysics to simulate this embodiment, adopts finite element method and combines the perfect matching layer boundary absorption condition to carry out theoretical calculation, and obtains the change relationship diagram of mode field distribution diagram, restrictive loss, dispersion, nonlinear coefficient and bending loss of the composite hollow core optical fiber of this embodiment through calculation.

[0051] See also Figure 2 , which is a two-dimensional mode field distribution and three-dimensional height expression diagram of the optical fiber at the 3μm fundamental mode. It can be seen from the figure that the multi-resonance layer hollow-core optical fiber of the present invention can concentrate the energy in the core area when transmitting optical signals, indicating that the light is well bound in the core area and the transmitted light has excellent beam quality;

[0052] See also Figure 3 , which is the relationship between the limiting loss of the optical fiber fundamental mode and the wavelength. It can be seen from the relationship diagram that the limiting loss is at a low level when the incident wavelength is 2.0μm-3.2μm, and the minimum loss is 7.97*10 at 2.7μm. -5 dB / m, which is much lower than the 0.2 dB / km of conventional single-mode fiber, enabling low-loss transmission when monitoring and measuring gases;

[0053] See also Figure 4, which is the relationship between the fundamental mode dispersion of optical fiber and the wavelength. It can be seen from the relationship diagram that: between the wavelength of 2.0μm-3.2μm, the dispersion is at an extremely low level. -13 order of magnitude, that is, its group velocity dispersion is stable at -1.5×10 -12 ~5.5×10 -13 ps / (nm·m); low dispersion can effectively reduce the broadening phenomenon of optical pulses caused by dispersion effects during transmission, which means that the pulses maintain a compact shape when propagating over long distances, reduce the overlap between pulses and signal distortion, improve signal quality, and increase signal transmission rate;

[0054] See also Figure 5 , which is the relationship between the fundamental mode mode area of ​​the optical fiber and the wavelength. From the relationship diagram, it can be seen that the mode field area of ​​the optical fiber is larger in the 2.0-3.2 μm band, and 2 It can be seen that this optical fiber is suitable for high-power laser transmission, improves the optical fiber damage threshold and reduces optical loss, which brings significant advantages, making it widely used in industry, communication and medical fields;

[0055] See also Figure 6 , which is the relationship between the nonlinear effect of the optical fiber fundamental mode and the wavelength. It can be seen from the relationship diagram that the nonlinear coefficient is relatively low in the 2.0-3.2 μm band, and the basic value is 0.07503~0.10816 (W·m) -1 The lower nonlinear coefficient can reduce the signal distortion caused by nonlinear effects, especially in long-distance, high-speed transmission and high-power applications, which improves the stability, signal quality and power transmission capacity of optical fiber communication systems;

[0056] See also Figure 7 and Figure 8 , providing a relationship diagram of the bending loss of the optical fiber when it is bent in the X and Y directions at a wavelength of 3 μm as a function of the bending radius. From the relationship diagram, it can be seen that under the condition of a wavelength of 3 μm, the optical fiber has low bending loss when it is bent in the x and y directions under a bending deformation of 1 cm to 31 cm. When the bending radius is 8 cm, the bending loss of the optical fiber in the x direction is 2.23×10 -4 dB / m; when the bending radius is 7cm, the bending loss in the y direction is 3.97×10 -4 dB / m; When the bending radius is 7 cm or more, the bending loss of the optical fiber when bending in the x and y directions is less than 10 -2 The dB / m level indicates that the optical fiber of this embodiment has excellent anti-bending performance, effectively reduces light leakage due to bending, and is widely used in scenarios requiring extremely flexible and compact wiring.

[0057] In summary, the present invention meets the anti-resonance reflection waveguide (ARROW) principle in terms of structural design, and uses multiple anti-resonance layers to improve the performance parameters during transmission, so that it has the characteristics of loss, near-zero dispersion and anti-bending, and is suitable for monitoring carbon dioxide gas molecules. Compared with the prior art, the present invention is structurally circular, which is easy to prepare and the preparation material is common quartz glass, and the cost is extremely low; in terms of performance parameters, the present invention has a limiting loss of less than 10 in the range of 2.0μm~3.2μm in the mid-infrared band. -5 dB / m, which is much lower than the existing single-mode optical fiber, achieving low-loss transmission; secondly, the present invention also has a transmission loss of up to 10 -13 The dispersion is close to zero and the nonlinear coefficient in the above transmission band is as low as 0.07503 (W·m) -1 , so that the optical fiber can obtain greater transmission power to achieve long-distance transmission; and when the bending radius is 7cm, it can reach 10 -4 The bending loss of dB / m indicates that the present invention has good anti-bending performance.

[0058] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0059] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on", "installed on", "fixed on" or "set on" another element, it can be directly on the other element or there can also be a centered element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and are not intended to be the only implementation method.

[0060] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0061] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring, comprising an outer cladding (1), an inner cladding (2) and an air core region (3) in sequence from outside to inside along the radial direction of the optical fiber, characterized in that: A plurality of first nested tube units (4) are arranged between the outer cladding (1) and the inner cladding (2), the plurality of first nested tube units (4) are distributed in an annular manner and are equidistant from one another, and the first nested tube units (4) are tangent to the outer cladding (1) and the inner cladding (2) respectively; The inner cladding (2) comprises an anti-resonance layer (5) and a plurality of second nested tube units (6), the plurality of second nested tube units (6) are arranged in a ring shape to form an air core region (3), the plurality of second nested tube units (6) are arranged at equal distances, and a gap exists between two adjacent second nested tube units (6), the anti-resonance layer (5) is located between the first nested tube unit (4) and the second nested tube unit (6), and is tangent to both the first nested tube unit (4) and the second nested tube unit (6); The number of the first nested tubular units (4) is six. The first nested tubular units (4) include a first microcapillary (41) circumscribed with the inner cladding (2); a second microcapillary (42) is inscribed in the inner wall of the first microcapillary (41); a third microcapillary (43) is inscribed in the inner wall of the second microcapillary (42); and the first microcapillary (41), the second microcapillary (42) and the third microcapillary (43) are all tangent to the outer cladding (1); The pore size d4 of the first microcapillary (41) is 20 μm, the pore size d5 of the second microcapillary (42) is 15 μm, and the pore size d6 of the third microcapillary (43) is 9 μm.

2. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 1, characterized in that: The base materials of the outer cladding layer (1), the plurality of first nested tube units (4), the anti-resonance layer (5) and the plurality of second nested tube units (6) are all quartz glass, and the refractive index thereof is 1.4192.

3. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 2, characterized in that: The number of the second nested tube units (6) is six, and the second nested tube units (6) include a fourth microcapillary (61) externally cut with the air core region (3), a fifth microcapillary (62) is inscribed in the inner wall of the fourth microcapillary (61), a sixth microcapillary (63) is inscribed in the inner wall of the fifth microcapillary (62), and the fourth microcapillary (61), the fifth microcapillary (62) and the sixth microcapillary (63) are all inscribed with the inner cladding (2).

4. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 3, characterized in that: The pore size of the fourth microcapillary (61) is d1 = 15 μm, the pore size of the fifth microcapillary (62) is d2 = 12 μm, and the pore size of the sixth microcapillary (63) is d3 = 6 μm.

5. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 4, characterized in that: The thickness of the first microcapillary (41), the second microcapillary (42), and the third microcapillary (43) is all t=0.744 μm.

6. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 5, characterized in that: The thickness of the first microcapillary (41), the second microcapillary (42), the third microcapillary (43), the fourth microcapillary (61), the fifth microcapillary (62) and the sixth microcapillary (63) are all t, and the thickness t satisfies the anti-resonance condition: Wherein, t represents the thickness of the dielectric tube, λ represents the designed working wavelength, n1 and n0 represent the refractive index of the dielectric tube material and the refractive index of air respectively, and m is an integer.

7. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 6, characterized in that: The outer cladding (1) is in the shape of a hollow cylinder, and its wall thickness t2 = 30 μm; the anti-resonance layer (5) is a micro-annular capillary, and its thickness t1 = 3 μm.

8. The multi-resonance layer hollow-core optical fiber for carbon dioxide gas monitoring according to claim 7, characterized in that: The inner regions of the outer cladding (1), the inner cladding (2), the plurality of first nested tube units (4), the anti-resonance layer (5) and the plurality of second nested tube units (6) are all filled with air, serving as air holes in the outer ring of the air core region (3). The interior of the air core region (3) is filled with air, and the refractive index of the air is 1.

Images