Low-loss bending-resistant hollow-core anti-resonance optical fiber applied to fluorescence imaging

Abstract

The invention provides a low-loss bending-resistant hollow-core anti-resonance optical fiber applied to fluorescence imaging. The low-loss bending-resistant hollow-core anti-resonance optical fiber can achieve low loss and low bending loss at the same time within the wave band of 410-575 nm. The inner cladding is provided with a plurality of inner cladding first-layer circular unit tubes and inner cladding second-layer circular nested tubes which are annularly distributed at equal intervals, and the inner cladding first-layer circular unit tubes are tangent to the inner side of the outer cladding; a plurality of inner cladding second-layer circular nesting pipes are arranged in the inner cladding first-layer circular unit pipes, the plurality of inner cladding second-layer circular nesting pipes annularly surround to form an air fiber core area, the plurality of inner cladding second-layer circular nesting pipes are arranged at equal intervals, a gap exists between every two adjacent inner cladding second-layer circular nesting pipes, and the inner cladding second-layer circular nesting pipes are tangent to the inner cladding first-layer circular unit pipes. The optical fiber provided by the invention has good bending resistance, effectively reduces light leakage caused by bending, and is widely applied to scenes requiring high flexibility and compact wiring.

Description

Technical Field

[0001] The present application relates to the field of optical fiber communications, and in particular to a low-loss, bend-resistant hollow-core anti-resonant optical fiber for fluorescence imaging. Background Art

[0002] With the development of modern fluorescence imaging technology, especially in the biomedical field, accurate imaging capabilities play a vital role in the early diagnosis of diseases and the formulation of treatment plans. In these applications, it is usually necessary to excite fluorescent markers with lasers and then collect and transmit fluorescent signals through optical fibers. The performance of optical fibers is crucial to the clarity and resolution of imaging.

[0003] However, conventional optical fibers have the following problems, which limit their application in high-demand imaging systems: ① Fiber loss problem: Conventional optical fibers, especially those with solid cores, often have large transmission losses, especially when transmitted over long distances, where optical signals are significantly attenuated. The presence of loss not only affects the transmission efficiency of the signal, but may also lead to a decrease in image quality. Fluorescence imaging requires high-fidelity transmission of signals, especially in high-precision imaging and low-signal environments, where fiber loss becomes an important factor limiting imaging performance; ② Limited working band: Conventional optical fibers can generally only work effectively within a certain wavelength range, which is particularly problematic in fluorescence imaging systems. Different detection bands in fluorescence imaging require that optical fibers can transmit different optical signals within a wide wavelength range, but existing optical fiber materials often cannot meet this requirement. In order to obtain accurate fluorescence signals, the wavelength ranges of the required excitation light and fluorescence signals are often wide, and the bandwidth limitation of conventional optical fibers becomes a technical bottleneck; ③ Mode mismatch problem: There may be a mismatch between the transmission mode of the optical fiber and the requirements of the imaging system, especially when imaging fine structures, conventional optical fibers may not provide sufficient transmission mode flexibility, resulting in signal distortion and decreased transmission efficiency. In addition, due to the internal refractive index gradient of the optical fiber during transmission, mode conversion or nonlinear effects may also be induced, resulting in a decrease in transmission performance; ④ Phase distortion and resolution limitation: In high-resolution imaging, any slight signal distortion will affect the final imaging result. Traditional optical fibers are prone to phase distortion during the transmission of high-power signals, thus affecting the accuracy of imaging, especially in high-precision instruments such as super-resolution fluorescence microscopes, where the phase transmission performance of optical fibers is crucial.

[0004] In order to overcome these problems, hollow-core fiber (HCF) has been widely studied in recent years. Hollow-core fiber reduces the propagation loss of light by replacing the core part with air or gas. Hollow-core antiresonant fiber (HC-ARF) uses the antiresonance principle to effectively suppress the mode mismatch and loss caused by the structure of the optical fiber during transmission, significantly improving the transmission efficiency and bandwidth of the optical fiber.

[0005] Hollow-core antiresonant fibers have been widely used in high-power laser transmission, nonlinear optics, sensor technology and other fields, but their application in fluorescence imaging is still in the exploratory stage. Since fluorescence imaging requires broadband and low-loss transmission characteristics, the potential of hollow-core antiresonant fibers in this field has not been fully explored. Therefore, it is necessary to design a low-loss, bend-resistant hollow-core antiresonant fiber for fluorescence imaging, which can significantly improve image quality, broaden the application scope of imaging technology, and promote the further development of fiber-optic imaging technology. Summary of the invention

[0006] To address the deficiencies of the above-mentioned prior art, the present application provides a low-loss, bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging, which can simultaneously achieve low loss and low bending loss in the 410-575nm band, significantly improving image quality.

[0007] A low-loss bending-resistant hollow-core anti-resonant optical fiber for fluorescence imaging comprises an outer cladding, an inner cladding and an air core region which are sequentially arranged from the outside to the inside along the radial direction of the optical fiber, a plurality of inner cladding first-layer circular unit tubes are arranged between the outer cladding and the inner cladding, and the plurality of inner cladding first-layer circular unit tubes are distributed in an annular manner with equal distances, wherein one end of each inner cladding first-layer circular unit tube is tangent to the inner side of the outer cladding, and the other end of each inner cladding first-layer circular unit tube is tangent to the inner cladding second-layer circular nested tube; the air core region is formed by a plurality of inner cladding second-layer circular nested tubes enclosed in an annular manner; each of the inner cladding second-layer circular nested tubes comprises a circular unit tube and an inner nested circular unit tube, the plurality of inner cladding second-layer circular nested tubes are arranged at equal distances, and there is a gap between every two adjacent inner cladding second-layer circular nested tubes.

[0008] Furthermore, the wall tube substrate materials of the outer cladding, the first layer of circular unit tubes of the inner cladding, and the second layer of circular nested tubes of the inner cladding are all quartz glass, and the refractive index of quartz glass is 1.4623.

[0009] Furthermore, the number of the circular unit tubes in the first layer of the inner cladding is six, and the wall thickness of the circular unit tubes in the first layer of the inner cladding is 0.347 μm.

[0010] Furthermore, the aperture d of the first circular unit tube of the inner cladding is 1 =17μm.

[0011] Furthermore, the number of the second layer of circular nested tubes in the inner cladding is six, and the circular unit tube is located in the inner cavity of the internally nested circular unit tube; one end of the circular unit tube is tangent to the inner side of the internally nested circular unit tube.

[0012] Furthermore, the aperture d of the circular unit tube is 2 =12μm, the aperture d of the internally nested circular unit tube 3 =18μm.

[0013] Furthermore, the wall thickness of the circular unit tube and the internally nested circular unit tube is 0.347 μm.

[0014] Furthermore, the wall thickness of the first layer of circular unit tubes, the circular unit tubes, and the internally nested circular unit tubes of the inner cladding are , satisfying the anti-resonance condition: ; In the formula Indicates the wall thickness, represents the designed operating wavelength, and are the refractive index of the dielectric tube material and the refractive index of air, respectively. is an integer.

[0015] Furthermore, the outer cladding is in the shape of a hollow cylinder, and the wall thickness of the outer cladding is 30 μm.

[0016] Furthermore, the interior of the outer cladding, the interior of the first layer of circular unit tubes of the inner cladding, the interior of the second layer of circular nested tubes of the inner cladding and the interior of the air core region are filled with air, and the refractive index of the air is 1.

[0017] Beneficial effects of this application: 1. The structural design of this application meets the anti-resonant reflection waveguide (ARROW) principle and uses the anti-resonant layer to improve the performance parameters during transmission, so that the optical fiber has the characteristics of broadband low loss and near-zero dispersion, so that it maintains good optical transmission characteristics in a wide spectrum range, and is suitable for light transmission in the field of fluorescence imaging; 2. The structure of the present application is a circular structure, which is easy to prepare and the preparation material is common quartz glass, and the cost is extremely low; 3. In terms of performance parameters, the limiting loss of this application is less than 10 in the visible light band range of 410-575nm. -11 dB / m, much lower than existing single-mode optical fibers, achieving low-loss transmission; 4. This application also has up to 10 -12 The dispersion is close to zero and the effective mode area is 289.82μm 2When the bending radius in the X and Y directions is 15cm and 13cm respectively, it can reach 10 -12 dB / m and 10 -13 The bending loss of dB / m indicates that the present invention has good anti-bending performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a cross-sectional schematic diagram of the overall structure of the present application; Figure 2 is a diagram representing the fundamental mode and three-dimensional height of the optical fiber cross section in this application; Figure 3 is the electric field contour map of the fundamental mode of the optical fiber cross section in this application; Figure 4 It is a schematic diagram of the relationship between the limiting loss of the fundamental mode of the optical fiber and the wavelength in this application; Figure 5 It is a schematic diagram of the relationship between the fundamental mode dispersion of optical fiber and the wavelength in this application; Figure 6 This is a schematic diagram of the relationship between the fundamental mode mode field area of ​​the optical fiber and the wavelength in this application; Figure 7 The relationship between the bending loss and the bending radius when the optical fiber is bent in the X direction at a wavelength of 530nm provided by the present application and the electric field distribution diagram when the optical fiber is bent in the X direction; Figure 8 The present application provides a relationship between the bending loss and the bending radius when the optical fiber is bent in the Y direction at a wavelength of 530nm and an electric field distribution diagram when the optical fiber is bent in the Y direction.

[0019] List of reference numerals: 1. Outer cladding; 2. Inner cladding; 3. Air core region; 4. First layer of circular unit tubes in the inner cladding; 5. Second layer of circular nested tubes in the inner cladding; 51. Circular unit tubes; 52. Internally nested circular unit tubes. DETAILED DESCRIPTION

[0020] The present application is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0021] See also Figure 1The present embodiment provides a low-loss bending-resistant hollow-core antiresonant optical fiber for fluorescence imaging, comprising an outer cladding 1, an inner cladding 2 and an air core region 3 arranged in sequence from the outside to the inside along the radial direction of the optical fiber, a plurality of inner cladding first-layer circular unit tubes 4 are arranged between the outer cladding 1 and the inner cladding 2, and the plurality of inner cladding first-layer circular unit tubes 4 are distributed in an annular manner with equal spacing, wherein one end of each inner cladding first-layer circular unit tube 4 is tangent to the inner side of the outer cladding 1, and the other end of each inner cladding first-layer circular unit tube 4 is tangent to the inner side of the inner cladding second-layer circular inlay The air core region 3 is formed by a plurality of inner cladding second layer circular nested tubes 5 which are surrounded in a ring shape; each of the inner cladding second layer circular nested tubes 5 comprises a circular unit tube 51 and an internally nested circular unit tube 52, and the plurality of inner cladding second layer circular nested tubes 5 are arranged at equal distances, and there is a gap between every two adjacent inner cladding second layer circular nested tubes 5; the circular unit tube 51 is located in the inner cavity of the internally nested circular unit tube 52; one end of the circular unit tube 51 is tangent to the inner side of the internally nested circular unit tube 52.

[0022] The wall tube substrate materials of the outer cladding 1, the first layer of circular unit tubes 4 of the inner cladding, and the second layer of circular nested tubes 5 of the inner cladding are all quartz glass, and the refractive index of quartz glass is 1.4623; quartz 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 optical signals inside the fiber is the same as that outside, thereby realizing high-speed and long-distance data transmission.

[0023] The number of the first-layer circular unit tubes 4 of the inner cladding and the second-layer circular nested tubes 5 of the inner cladding are both six; the wall thickness of the first-layer circular unit tubes 4 of the inner cladding is 0.347 μm; the wall thickness of the circular unit tubes 51 and the internal nested circular unit tubes 52 are both 0.347 μm.

[0024] The aperture d of the first circular unit tube 4 of the inner cladding is 1 =17 μm; the aperture d of the circular unit tube 51 2 = 12 μm, the pore size d of the internally nested circular unit tube 52 3 =18μm.

[0025] The microcapillary structure inside the second layer of the inner cladding circular nested tube 5 helps to optimize the transmission efficiency of the optical signal, and the mutual influence between the microcapillaries of the circular unit tube 51 and the microcapillaries of the internally nested circular unit tube 52 is small, which effectively reduces the transmission loss. At the same time, thanks to the structural design of the second layer of the inner cladding circular nested tube 5, the bandwidth of the hollow-core optical fiber can also be improved, thereby supporting signal transmission in a wider frequency range.

[0026] The structural design of the second layer of circular nested tubes 5 in the inner cladding can help optimize the transmission efficiency of optical signals and increase the bandwidth of the hollow-core optical fiber, thereby supporting the transmission of frequency signals in a wider range.

[0027] The wall thickness of the first layer circular unit tube 4, the circular unit tube 51, and the internally nested circular unit tube 52 of the inner cladding is , satisfying the anti-resonance condition: ; In the formula Indicates the wall thickness, represents the designed operating wavelength, and are the refractive index of the dielectric tube material and the refractive index of air, respectively. is an integer.

[0028] Furthermore, the outer cladding 1 is a hollow cylindrical shape, and the wall thickness of the outer cladding 1 is 30 μm; the outer cladding 1 serves as the outer protective layer of the hollow 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 inner cladding 2 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.

[0029] The interior of the outer cladding 1, the interior of the first layer circular unit tube 4 of the inner cladding, the interior of the second layer circular nested tube 5 of the inner cladding, and the interior of the air core region 3 are filled with air, and the refractive index of the air is 1; the design of filling the interior with air and adopting an air refractive index lower than that of quartz 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.

[0030] 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. The realization principle of the perfect matching layer is: a boundary condition with the same material as the cladding and matching wave impedance is set outside the outer cladding 1 of the optical fiber, so 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.

[0031] Next, the technical solution of the present application is further described in conjunction with specific embodiments: 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 mode field distribution diagram, electric field contour diagram, restrictive loss, dispersion and bending loss change relationship diagram of the hollow core optical fiber of this embodiment through calculation.

[0032] See also Figure 2 , which is the two-dimensional mode field distribution and three-dimensional height expression diagram of the optical fiber at the 530nm fundamental mode. Figure 2 It can be seen that the hollow antiresonant optical fiber of the present application can concentrate the energy in the core region when transmitting an optical signal, indicating that the light is well confined in the core region and the transmitted light has excellent beam quality.

[0033] See also Figure 3 , is the contour map of the optical fiber at the 530nm fundamental mode, from Figure 3 It can be seen from the figure that the hollow antiresonant optical fiber of the present application can well confine the light in the core region when transmitting the optical signal.

[0034] See also Figure 4 , is the relationship between the limiting loss of the optical fiber fundamental mode and the wavelength. Figure 4 It can be seen that the limiting loss is at a low level when the incident wavelength is 410-575nm, and the minimum loss is 2.62×10 -11 dB / m, which is much lower than the 0.2dB / km of conventional single-mode fiber, enabling low-loss transmission when monitoring and measuring gases; See also Figure 5 , is the relationship between the fundamental mode dispersion of optical fiber and the wavelength. Figure 5 It can be seen that the dispersion is at a very low level between the wavelengths of 410-575nm. -12 order of magnitude, that is, its group velocity dispersion is stable at -5.293×10 -12 ~2.671×10-12 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; See also Figure 6 , is the relationship between the fundamental mode field area of ​​the optical fiber and the wavelength. Figure 6 It can be seen that the mode field area of ​​the optical fiber is larger in the 410-575nm band, and the mode field area of ​​the optical fiber is larger in the 275.64-289.82μm band. 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; See also Figure 7 , provides the relationship between the bending loss and the bending radius when the optical fiber is bent in the X direction at a wavelength of 530nm and the electric field distribution diagram when the optical fiber is bent in the X direction; refer to Figure 8 , providing the relationship between the bending loss and the bending radius when the optical fiber is bent in the Y direction at a wavelength of 530nm, and the electric field distribution diagram when the optical fiber is bent in the Y direction. Figure 7 and Figure 8 It can be seen that under the condition of wavelength of 530nm, under the bending deformation of 3 to 31cm, the optical fiber has low bending loss when bending in the X and Y directions. When the bending radius is 15cm, the optical fiber has low bending loss in the X direction and low bending loss in the Y direction. - 12 dB / m; when the bending radius is 1.3 cm, the bending loss in the Y direction is 6.35×10 -13 After the bending radius is 13cm, the bending loss of the optical fiber when bending in the X and Y directions is 10 -10 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.

[0035] In summary, the present application utilizes an anti-resonance layer in structural design to improve the performance parameters during transmission, so that it has the characteristics of loss, near-zero dispersion and anti-bending, which is suitable for monitoring carbon dioxide gas molecules, and the preparation material is common quartz glass, which has extremely low cost; in terms of performance parameters, the present application has a limiting loss of less than 10 in the range of 410-575nm in the mid-infrared band. -11 dB / m, which is much lower than the existing single-mode optical fiber, achieving low-loss transmission; secondly, this application also has a 10 -12 The dispersion is close to zero and the effective mode area is 289.82μm2 , and when the bending radius in the X and Y directions is 15cm and 13cm respectively, it can reach 10 -12 dB / m and 10 -13 The bending loss of dB / m indicates that the present invention has good anti-bending performance.

[0036] The technical means disclosed in the present application are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging, comprising an outer cladding (1), an inner cladding (2) and an air core region (3) arranged in sequence from outside to inside along the radial direction of the optical fiber, characterized in that: A plurality of inner cladding first layer circular unit tubes (4) are arranged between the outer cladding (1) and the inner cladding (2), and the plurality of inner cladding first layer circular unit tubes (4) are distributed in an annular manner at equal distances, wherein one end of each inner cladding first layer circular unit tube (4) is tangent to the inner side of the outer cladding (1), and the other end of each inner cladding first layer circular unit tube (4) is tangent to the inner cladding second layer circular nested tube (5); the air core region (3) is formed by the plurality of inner cladding second layer circular nested tubes (5) enclosed in an annular manner; each of the inner cladding second layer circular nested tubes (5) comprises a circular unit tube (51) and an inner nested circular unit tube (52); the plurality of inner cladding second layer circular nested tubes (5) are arranged at equal distances, and a gap exists between every two adjacent inner cladding second layer circular nested tubes (5).

2. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The wall tube substrate materials of the outer cladding (1), the first layer circular unit tube (4) of the inner cladding, and the second layer circular nested tube (5) of the inner cladding are all quartz glass, and the refractive index of the quartz glass is 1.4623.

3. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The number of the first-layer circular unit tubes (4) of the inner cladding is six, and the wall thickness of the first-layer circular unit tubes (4) of the inner cladding is 0.347 μm.

4. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The aperture d1 of the first layer of circular unit tubes (4) in the inner cladding is 17 μm.

5. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The number of the second layer circular nested tubes (5) of the inner cladding is six, and the circular unit tube (51) is located in the inner cavity of the internally nested circular unit tube (52); one end of the circular unit tube (51) is tangent to the inner side of the internally nested circular unit tube (52).

6. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 5, characterized in that: The aperture d2 of the circular unit tube (51) is 12 μm, and the aperture d3 of the circular unit tube (52) nested inside is 18 μm.

7. A low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 5, characterized in that: The wall thickness of the circular unit tube (51) and the internally nested circular unit tube (52) are both 0.347 μm.

8. The low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The wall thicknesses of the first layer circular unit tube (4) of the inner cladding, the circular unit tube (51), and the internally nested circular unit tube (52) are all , satisfying the anti-resonance condition: ; In the formula Indicates the wall thickness, represents the designed operating wavelength, and are the refractive index of the dielectric tube material and the refractive index of air, respectively. is an integer.

9. The low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The outer cladding (1) is in the shape of a hollow cylinder, and the wall thickness of the outer cladding (1) is 30 μm.

10. The low-loss bend-resistant hollow-core antiresonant optical fiber for fluorescence imaging according to claim 1, characterized in that: The interior of the outer cladding (1), the interior of the first layer of circular unit tubes (4) of the inner cladding, the interior of the second layer of circular nested tubes (5) of the inner cladding, and the interior of the air core region (3) are filled with air, and the refractive index of the air is 1.

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