Optical fiber and preparation method thereof

Abstract

The invention relates to the technical field of optical fibers, and discloses an optical fiber and a preparation method thereof.The optical fiber comprises an outer wrapping tube, an optical core and capillary tubes, the axes of the outer wrapping tube, the optical core and the capillary tubes are parallel, the optical core is arranged in the outer wrapping tube, and the capillary tubes are arranged between the inner circumferential face of the outer wrapping tube and the outer circumferential face of the optical core; the capillary tubes are arranged around the optical core at intervals, one end of each capillary tube is connected with the outer circumferential face of the optical core through laser welding in the radial direction of the optical core, the other end of each capillary tube is connected with the inner circumferential face of the outer wrapping tube through laser welding, and therefore the connection stability of the capillary tubes, the optical core and the outer wrapping tube is high, and the capillary tubes are not prone to sliding and high in reliability. According to laser welding, a laser beam with high energy density is used as a heat source to enable materials to be locally melted and fused so as to achieve connection, micro gaps between the capillary tube and the optical core and between the capillary tube and the outer wrapping tube can be eliminated, pollutants cannot be introduced, and scattering loss caused by pollution can be eliminated.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber technology, and more specifically, relates to an optical fiber and its preparation method. Background Technology

[0002] Solar-guided optical fiber technology is a key development direction in the field of green building and renewable energy utilization. It aims to efficiently introduce natural light into the interior space of buildings through optical transmission media, so as to significantly reduce lighting energy consumption and improve the quality of indoor light environment. Among the related technologies, the optical fiber used in solar-guided optical fiber technology includes an outer cladding, a capillary layer and a light-guiding core layer. The capillary layer includes multiple capillaries, which are connected between the outer cladding and the light-guiding core layer through physical contact. In this type of optical fiber structure, the bonding strength between the capillaries and the outer cladding and the light-guiding core layer is low, and interlayer slippage or even detachment is prone to occur, causing optical path interruption and low reliability. Summary of the Invention

[0003] The main objective of this invention is to provide a highly reliable optical fiber.

[0004] According to a first aspect of the present invention, an optical fiber is provided, comprising an outer sheath, an optical core, and a capillary tube, wherein the axes of the outer sheath, the optical core, and the capillary tube are parallel, the optical core is disposed within the outer sheath, and the capillary tube is disposed between the inner circumferential surface of the outer sheath and the outer circumferential surface of the optical core. A plurality of capillary tubes are arranged at intervals around the optical core, wherein, along the radial direction of the optical core, one end of each capillary tube is laser-welded to the outer circumferential surface of the optical core, and the other end is laser-welded to the inner circumferential surface of the outer sheath.

[0005] In a specific embodiment of the present invention, the number of capillaries is 4 to 12.

[0006] In one specific embodiment of the present invention, the number of capillaries is eight.

[0007] In a specific embodiment of the present invention, the capillary is made of pure quartz glass, and the outer diameter of the capillary is 5 ~ 15 μm, and the wall thickness is 1 ~ 3 μm.

[0008] In one specific embodiment of the present invention, a plurality of capillaries are arranged at equal intervals.

[0009] In a specific embodiment of the present invention, the optical fiber has a first imaginary circle arranged around the axis of the optical core, and the axes of a plurality of capillaries are arranged on the first imaginary circle, wherein the diameter of the first imaginary circle is 170 ~ 1000 μm.

[0010] This invention also proposes a method for preparing optical fibers, applicable to the preparation of optical fibers as described above, comprising the following steps:

[0011] A preform is provided, the preform comprising an outer tube preform, an optical core preform, and a capillary preform. The axes of the outer tube preform, the optical core preform, and the capillary preform are parallel. The optical core preform is disposed within the outer tube preform, and the capillary preform is disposed between the inner circumferential surface of the outer tube preform and the outer circumferential surface of the optical core preform. There are multiple capillary preforms, which are arranged at intervals around the optical core preform along the radial direction of the optical core preform. One end of each capillary preform is connected to the outer circumferential surface of the optical core preform by laser welding, and the other end is connected to the inner circumferential surface of the outer tube preform by laser welding.

[0012] The preform is drawn to obtain the optical fiber. During the drawing process, a positive pressure P1 is applied to the cavity inside the capillary preform, while a negative pressure P2 is applied to the area between the inner circumferential surface of the outer sheath preform, the outer circumferential surface of the capillary preform, and the outer circumferential surface of the optical core preform. The absolute value of the negative pressure P2 is controlled to be less than the positive pressure P1 to prevent the capillary preform from collapsing during the drawing process.

[0013] In a specific embodiment of the present invention, the positive pressure P1 and the negative pressure P2 satisfy the following relationship: -0.5 P2≤ P1≤ -0.1 P2.

[0014] In a specific embodiment of the present invention, the control range of the positive pressure P1 is 1.0 kPa to 50.0 kPa, and the control range of the negative pressure P2 is -0.3 kPa to -15 kPa.

[0015] In a specific embodiment of the present invention, the laser used in the laser welding is a CO2 laser with a power control range of 20 ~ 45 W and an equivalent welding temperature of 1750 ~ 1850℃.

[0016] In a specific embodiment of the present invention, the outer diameter of the outer cladding preform is D1 mm;

[0017] The outer diameter of the optical core preform is D2 mm;

[0018] The preform has a second imaginary circle, which is arranged around the axis of the optical core preform, and the axes of the plurality of capillary preforms are arranged on the second imaginary circle, the diameter of the second imaginary circle being D3 mm;

[0019] Among them, D2=(0.7~0.9)D1, D3=(0.8~0.95)D1, D3>D2.

[0020] One of the above-described technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0021] In the optical fiber of this invention, the two ends of the capillary are connected to the outer peripheral surface of the optical core and the inner peripheral surface of the outer sheath tube respectively by laser welding in the radial direction of the optical core. The connection between the capillary and the optical core and the outer sheath tube has high stability, the capillary is not easy to slip, and the reliability is high. Laser welding uses a high-energy-density laser beam as a heat source to locally melt and fuse the materials to achieve the connection. Compared with high-temperature melting (such as oxyhydrogen flame welding), laser welding connects the capillary to the optical core and the outer sheath tube, which can eliminate the micro gaps between the capillary and the optical core and the outer sheath tube, and it does not introduce contaminants, thus eliminating scattering loss caused by contamination. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0023] Figure 1 This is a cross-sectional view of the optical fiber in Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the steps in the optical fiber fabrication method of Embodiment 1 of the present invention;

[0025] Figure 3 This is a cross-sectional view of the optical fiber in Embodiment 2 of the present invention;

[0026] Figure 4 This is a cross-sectional view of the optical fiber in Embodiment 3 of the present invention;

[0027] Figure 5 This is a cross-sectional view of the optical fiber in Embodiment 4 of the present invention;

[0028] Figure 6 This is a cross-sectional view of the optical fiber in Embodiment 5 of the present invention;

[0029] Figure 7 This is a cross-sectional view of the optical fiber in Embodiment 6 of the present invention;

[0030] Figure 8 This is a cross-sectional view of the optical fiber in Embodiment 7 of the present invention;

[0031] Figure 9 This is a cross-sectional view of the optical fiber in Embodiment 8 of the present invention;

[0032] Figure 10 This is a cross-sectional view of the optical fiber in Embodiment 9 of the present invention.

[0033] In the diagram, 1 is the outer tube; 2 is the optical core; 3 is the capillary; 4 is the cladding layer; and 5 is the solid rod. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0035] Example 1

[0036] Reference Figure 1 As shown, a preferred embodiment of this application discloses an optical fiber comprising an outer sheath 1, an optical core 2, and a capillary tube 3. The axes of the outer sheath 1, the optical core 2, and the capillary tube 3 are parallel. The optical core 2 is disposed inside the outer sheath 1, and the capillary tube 3 is disposed between the inner circumferential surface of the outer sheath 1 and the outer circumferential surface of the optical core 2. Multiple capillary tubes 3 are arranged at intervals around the optical core 2. Along the radial direction of the optical core 2, one end of each capillary tube 3 is laser-welded to the outer circumferential surface of the optical core 2, and the other end is laser-welded to the inner circumferential surface of the outer sheath 1. Optical welding provides a stable connection between the capillary 3, the optical core 2, and the outer tube 1, ensuring high reliability as the capillary 3 is less prone to slippage. In contrast, laser welding utilizes a high-energy-density laser beam as a heat source to locally melt and fuse the materials, achieving a connection. Compared to high-temperature melting (such as oxyhydrogen flame welding), laser welding connects the capillary 3, the optical core 2, and the outer tube 1, eliminating micro-gaps between them. Furthermore, it does not introduce contaminants, thus eliminating scattering losses caused by contamination.

[0037] In this embodiment, there are eight capillaries 3, arranged at equal intervals, i.e., adjacent capillaries 3 are spaced 45° apart. This type of fiber, with its capillary 3 layer, exhibits relatively high density and uniformity, increasing the numerical aperture of the fiber and enhancing its ability to capture large-angle incident light. Furthermore, the spaced arrangement of the capillaries 3 offers significant advantages over a close arrangement in terms of optical performance, manufacturing feasibility, and mechanical flexibility. Specifically, in a close arrangement, the physical contact between the capillaries 3 creates a continuous refractive index region, leading to light leakage and increased transmission loss. Simultaneously, this structure places extremely stringent requirements on the geometric precision of the capillaries 3, making it prone to structural failure during the fiber drawing process due to wall fusion, and significantly increasing fiber stiffness. In contrast, the spaced arrangement allows each capillary 3 to operate as an independent total internal reflection interface, effectively suppressing light leakage; its structural tolerance is stronger, which is beneficial to improving process yield; at the same time, this arrangement reduces the amount of quartz material used, lowers the fiber's mass per unit length and bending stiffness, making it more suitable for complex wiring scenarios. Therefore, the spaced arrangement of the capillary 3 achieves an optimal balance between optical efficiency, manufacturability, and mechanical flexibility, constituting one of the core innovations of this invention.

[0038] In this embodiment, the capillary 3 is made of pure quartz glass, which can reduce the scattering and loss of light signals, and the optical core 2 has good performance.

[0039] In practical applications, the outer diameter of the capillary 3 is 5 ~ 15 μm and the wall thickness is 1 ~ 3 μm, which is determined according to the actual application and is not limited in this application; for example, the outer diameter of the capillary 3 is 10 ± 0.1 μm and the wall thickness is 2 μm; specifically, the optical fiber has a first imaginary circle, which is arranged around the axis of the optical core 2, and the axes of multiple capillary 3 are arranged on the first imaginary circle, wherein the diameter of the first imaginary circle is 170 ± 0.5 μm.

[0040] In practical applications, the diameter of the first imaginary circle can also be any value in the range of 170 to 1000 μm, depending on the actual application, and this application does not impose any restrictions on it.

[0041] In this embodiment, the outer cladding tube 1 is made of low-hydroxyl pure SiO2 synthetic quartz material. Its advantages are that the low hydroxyl content effectively reduces the absorption of light by hydroxyl impurities, thereby reducing the loss during light transmission. The pure SiO2 synthetic quartz material has high hardness and good chemical stability, which can provide reliable mechanical support for the optical fiber and protect the internal structure from external physical damage and chemical corrosion. Specifically, the outer diameter of the outer cladding layer is 200 ± 0.2 μm and the wall thickness is 10 μm. This ensures that the outer cladding layer has sufficient strength to withstand external pressure and tension, without increasing the overall weight and cost of the optical fiber due to excessive thickness. The inner circumferential surface of the outer cladding tube 1 forms an interface with a diameter of 180 μm. This interface is specially treated to have a smooth and flat surface, providing ideal conditions for laser welding connection with the capillary tube 3. Through the laser welding process, the outer cladding tube 1 and the capillary tube 3 can be tightly combined to form a whole, effectively preventing light leakage and scattering at the interface, while enhancing the mechanical stability of the optical fiber, enabling it to withstand certain bending and stretching without damage during installation and use.

[0042] In this embodiment, the optical core 2 is the core light-guiding channel of the optical fiber, with a diameter of 60 ± 0.3 μm. The optical core 2 is made of pure solid SiO2 material. The optical core 2 and the capillary 3 are coupled without gaps through laser welding. This gapless connection method fundamentally eliminates the reflection and scattering loss of light at the interface, allowing light to be transmitted smoothly between the optical core 2 and the capillary 3 layer, thereby minimizing optical loss. The pure solid SiO2 material has the characteristics of high transparency and low loss, which can ensure that light can be transmitted over long distances with low loss in the optical core 2. At the same time, its stable chemical properties and good mechanical properties also enable the optical core 2 to withstand certain temperature changes and mechanical stress, ensuring that the optical fiber can work reliably in various complex environments.

[0043] The outer circumferential surface of the outer tube 1 has a covering layer 4.

[0044] Reference Figure 2 As shown, the present invention also proposes an optical fiber fabrication method, applicable to the fabrication of optical fibers as described above, comprising the following steps:

[0045] Step 1: Provide a preform, which includes an outer tube preform, an optical core preform, and a capillary preform. The axes of the outer tube preform, the optical core preform, and the capillary preform are parallel. The optical core preform is located inside the outer tube preform, and the capillary preform is located between the inner circumferential surface of the outer tube preform and the outer circumferential surface of the optical core preform. There are multiple capillary preforms, which are arranged at intervals around the optical core preform. Along the radial direction of the optical core preform, one end of the capillary preform is connected to the outer circumferential surface of the optical core preform by laser welding, and the other end is connected to the inner circumferential surface of the outer tube preform by laser welding.

[0046] Step 2: The preform is drawn to obtain optical fiber. During the drawing process, a positive pressure P1 is applied to the cavity inside the capillary preform, while a negative pressure P2 is applied in the area between the inner circumferential surface of the outer sheath preform, the outer circumferential surface of the capillary preform, and the outer circumferential surface of the optical core preform. The absolute value of the negative pressure P2 is controlled to be less than the positive pressure P1 to prevent the capillary preform from collapsing during the drawing process.

[0047] When a positive pressure P1 is applied to the internal cavity of the capillary preform, all the internal cavities of the capillary preform are connected, and high-purity gas is filled into the internal cavity to maintain a positive pressure environment to resist the structural collapse caused by surface tension during the wire drawing process.

[0048] When a negative pressure P2 is applied to the area between the inner circumferential surface of the outer casing preform, the outer circumferential surface of the capillary preform, and the outer circumferential surface of the optical core preform, the cavities between the three are connected and a vacuum treatment is performed to maintain them in a low-pressure state. This works in conjunction with the positive pressure of the internal cavity of the capillary preform to stabilize the capillary 3 structure.

[0049] In this embodiment, the positive pressure P1 and the negative pressure P2 satisfy the relationship: -0.5 P2 ≤ P1 ≤ -0.1 P2, and the control range of the positive pressure P1 is 1.0 kPa to 50.0 kPa, while the control range of the negative pressure P2 is -0.3 kPa to -15 kPa. Specifically, the positive pressure P1 is controlled according to the pressure control function P1 = K 2 * 3.75*10 5 The formula is as follows: K is the drawing ratio; and P2 = -0.3P1. P1 and P2 satisfy the above conditions, which can effectively stabilize the structure of capillary 3 during the drawing process.

[0050] The outer diameter of the outer cladding preform is D1 mm; the outer diameter of the core preform is D2 mm; the preform has a second imaginary circle, which is arranged around the axis of the core preform, and the axes of multiple capillary preforms are arranged on the second imaginary circle, the diameter of the second imaginary circle is D3 mm; wherein, D2 = (0.7 ~ 0.9)D1, D3 = (0.8 ~ 0.95)D1, D3 > D2; preferably, D2 = 0.8D1, D3 = 0.85D1.

[0051] Specifically, the fiber fabrication method described above utilizes a combination of techniques. During the preform drawing process, a positive pressure P1 is applied to the internal cavity of the capillary preform, while a negative pressure P2 is applied to the region between the inner circumferential surface of the outer sheath preform, the outer circumferential surface of the capillary preform, and the outer circumferential surface of the optical core preform. The absolute value of the negative pressure P2 is controlled to be less than the positive pressure P1. This effectively suppresses deformation caused by force and surface tension, significantly improving structural stability and transmission consistency. Furthermore, since the preform is formed by connecting the outer sheath preform, capillary preform, and optical core preform using laser welding, OH hydroxyl contamination and thermal stress issues are fundamentally eliminated compared to flame welding, improving product reliability and optical performance. Additionally, it achieves high-purity, low-loss, and defect-free connections at the interfaces of the outer sheath preform, capillary preform, and optical core preform, making it suitable for fabricating complex high-end optical fibers.

[0052] Furthermore, the preparation method of the preform includes the following steps:

[0053] Step 11: Arrange multiple capillary preforms along the inner circumferential surface of the outer tube preform.

[0054] Specifically, a quartz glass outer tube preform with an outer diameter of D1 is selected, and multiple capillary preforms are arranged circumferentially on its inner circumferential surface, so that they are evenly distributed along the circumference on a second imaginary circle with a diameter of D3.

[0055] Step 12: Weld the capillary preform and the outer tube preform using laser welding technology.

[0056] Specifically, a laser is used to perform circumferential scanning welding on the contact interface between the outer circumferential surface of the capillary preform and the inner circumferential surface of the outer tube preform. Welding is carried out in a dry inert atmosphere or low-pressure environment to avoid the introduction of OH groups. The welding quality is monitored by an online interferometric detection system to ensure that the interface air gap is less than 0.1 μm.

[0057] Step 13: Arrange the optical core preform inside the capillary preform layer formed by multiple capillary preforms, wherein the capillary preform and the optical core preform are tangent.

[0058] Specifically, a solid quartz core preform (diameter D2) is slowly inserted into the inner circumference of the capillary preform layer, so that its outer circumferential surface is in tangential contact with the outer circumferential surface of the capillary preform, maintaining the overall structure axial concentricity.

[0059] Step 14: Weld the capillary preform and the optical core preform using laser welding technology.

[0060] Specifically, a laser is used to perform local scanning welding on the contact ring between the capillary preform and the outer wall of the optical core preform.

[0061] The laser welding used in the preform preparation process is a CO2 laser with a power control range of 20 ~ 45 W and an equivalent welding temperature of 1750 ~ 1850℃.

[0062] When fabricating the optical fiber of this embodiment using the above-described optical fiber fabrication method, the specific steps are as follows:

[0063] The outer tube preform is a quartz glass tube with an outer diameter of 100 mm. Eight high-purity quartz capillary preforms with an outer diameter of 5.0 mm and a wall thickness of 1.0 mm are arranged at equal intervals along an 85 mm circumference, with adjacent members at a 45° angle, forming a ring structure. The optical core preform is a solid quartz rod with a diameter of 80 mm. Precision positioning fixtures ensure that the rod, the imaginary ring formed by the capillary preforms, and the outer tube preforms maintain axial concentricity and radial symmetry.

[0064] After assembly, a stepped welding process was performed using a CO2 laser: In the first stage, circumferential scanning welding was conducted at the contact area between the outer circumferential surface of the capillary preform and the inner circumferential surface of the outer sheath preform, with a laser power of 60 W, a scanning speed of 2 mm / s, and the local temperature controlled at 1650–1700℃; in the second stage, focused scanning welding was performed at the contact area between the outer circumferential surface of the capillary preform and the outer circumferential surface of the optical core 2, with a laser power of 70 W and a scanning speed of 1.5 mm / s. The entire welding process was carried out under nitrogen protection at a dew point below -40℃ to minimize the introduction of hydroxyl groups.

[0065] After welding, the fiber drawing stage begins. The drawing ratio is set to K=0.002, the final outer diameter of the target fiber is 200 μm, the diameter of core 2 is 160 μm, and the distribution diameter of capillary 3 is 170 μm (the diameter of the first imaginary circle). The drawing speed is controlled at 15 m / min, and the pneumatic control system is activated simultaneously. A positive pressure P1=1.5 kPa is applied to the inner cavity of the capillary preform, and a negative pressure P2=–0.45 kPa is applied to the area between the inner circumferential surface of the outer sheath preform, the outer circumferential surface of the capillary preform, and the outer circumferential surface of the core preform. This is to suppress structural deformation caused by surface tension during high-temperature drawing (~2000℃), ensuring that the wall thickness of capillary 3 is maintained at 2 ±0.1 μm and the roundness error is no greater than 3%.

[0066] Performance testing shows that the fiber has a typical transmission loss of 3.8 dB / km at a wavelength of 550 nm and a numerical aperture (NA) ≥ 0.50. Under standard test conditions (outdoor illuminance of 100,000 lux, fiber length of 20 m), the output luminous flux reaches 2850 lm. The minimum bending radius is 35 mm, which can meet the requirements of most building cabling. After reliability testing (85℃ / 85% RH, 1000 hours), the loss increment is less than 0.3 dB / km, demonstrating good environmental stability and practical potential.

[0067] Example 2

[0068] Reference Figure 3 As shown, this embodiment provides an optical fiber whose structure is roughly the same as that of the optical fiber in Embodiment 1, except that the number of capillaries 3 is 12.

[0069] The optical core preform is a high-purity solid quartz rod with a diameter of 80 mm; the capillary preform consists of 12 preforms arranged precisely in a circumferential equiangular manner, each with an outer diameter of 5 mm and a wall thickness of 1 mm; the outer sheath preform is a quartz glass tube with an inner diameter of 90 mm and a wall thickness of 5 mm. These preforms are drawn into an optical fiber with an outer diameter of 200 μm using a high-temperature drawing process, resulting in an optical core diameter of approximately 160 μm.

[0070] In terms of manufacturing process, firstly, twelve capillary preforms are fixed around the optical core preform and encapsulated within the outer tube 1 optical core preform to form a preform rod; then, a CO2 laser is used at a power of 35 W and a scanning speed of 5 mm / s to locally weld the contact points between the capillary preforms, the optical core preforms, and the outer tube preforms, while helium gas is introduced for active heat dissipation to control the local temperature below 1650℃; finally, wire drawing is performed at 2050℃, and a slight positive pressure of 10–50 kPa (P1) is maintained inside the capillary preform, while a negative pressure of -3 to -15 kPa (P2) is maintained between the capillary preform, the optical core preform, and the outer tube preform to maintain the structural morphology of the capillary 3.

[0071] This fiber structure achieves an air-fill ratio of 75% and a numerical aperture stable between 0.55 and 0.56. Experimental results show that the fiber exhibits a transmission loss of 3.5–4.5 dB / km at a wavelength of 550 nm, with an additional loss of less than 0.5 dB at a bending radius of 30 mm. This solution is suitable for applications with extreme requirements for light guiding performance.

[0072] Example 3

[0073] Reference Figure 4 As shown, to address the issues of insufficient mechanical strength and poor environmental tolerance in traditional hollow-core solar fiber, this embodiment proposes an optical fiber. The structure of the optical fiber in this embodiment is roughly the same as that in Embodiment 1, except that there are four capillary tubes 3 and four solid rods 5. The outer diameter of the solid rods 5 is the same as that of the capillary tubes 3. The solid rods 5 and capillary tubes 3 are arranged alternately around the optical core 2. This design significantly enhances the bending and compressive strength of the optical fiber by partially replacing the capillary tubes 3 with solid rods 5, while moderately sacrificing some optical performance. It is particularly suitable for lighting scenarios with high vibration and pressure requirements, such as urban underground pipe corridors, highway tunnels, and industrial plants.

[0074] Structurally, the optical fiber has an overall outer diameter of 320 μm, and the optical core 2 is made of high-purity quartz glass with a diameter of 160 μm. Around it are eight external units arranged in a ring: four hollow capillaries 3 with an inner diameter of 10 μm and a wall thickness of 1.5 μm, used to maintain light guiding capability; and four solid fluorine-doped quartz rods (refractive index 1.440) of the same outer diameter, interspersed with the capillaries 3 to form high-rigidity support units. All capillaries 3 and solid rods 5 are drawn using the same lathe to ensure geometric consistency and reduce thermal stress; the outermost layer is a 60 μm thick polymer coating 4.

[0075] The manufacturing process employs a stacking method: pre-drawn capillary preforms are fixedly welded to solid rod 5 preforms according to the design sequence to form preforms, which are then integrally melt-drawn at 1950℃ under nitrogen protection. The fiber end face is treated with precision cutting and polishing processes to ensure a low-loss end face at the multi-material interface.

[0076] Performance testing demonstrates that this hybrid structure achieves a balance between design and objectives: its transmission loss at 550 nm wavelength is 5.5 ± 0.6 dB / km, its numerical aperture is 0.48, and its air-fill ratio is 58%. Mechanical properties are significantly improved, with a minimum bending radius of 25 mm and lateral pressure resistance exceeding 1.5 GPa, representing an improvement of over 50% compared to a pure hollow structure. After a dual 85 aging test (85℃, 85% RH, 2000 hours), the loss increment at 1380 nm is less than 2.1 dB / km.

[0077] Example 4

[0078] Reference Figure 5 As shown, this embodiment proposes an optical fiber to address the performance degradation problem faced by traditional solar optical fibers when used in hydrogen-rich environments. Its core innovation lies in the use of a high-performance composite polymer material that integrates physical barrier and chemical trapping functions, which significantly reduces manufacturing complexity and cost while ensuring excellent hydrogen barrier performance.

[0079] The optical fiber in this embodiment has the same structure as the optical core 2 in Embodiment 1. The difference is that the cladding layer 4 includes an inner protective layer and an outer protective layer. The inner protective layer covers the outer cladding tube 1, and the outer protective layer covers the inner protective layer. In terms of structural design, the optical fiber guiding part continues the high-performance configuration, using a 180 μm ultra-high purity synthetic quartz optical core 2 with eight circumferentially symmetrically arranged capillary tubes 3. The inner diameter of the capillary tubes 3 is 6 μm and the wall thickness is 2 μm, thus forming a light guiding structure with a numerical aperture of 0.53 and an air filling rate of 71%. The hydrogen blocking part is a double-layer coating structure of an inner protective layer and an outer protective layer: the inner protective layer is a 45 μm thick palladium-doped polyimide main hydrogen blocking layer. This material combines the inherent extremely low gas permeability of polyimide with the catalytic capture ability of palladium nanoparticles to form an integrated "blocking-capture" barrier; the outer protective layer uses a 60 μm standard hydrolysis-resistant UV-curable acrylic resin to provide mechanical and environmental protection.

[0080] In terms of manufacturing process, after the optical fiber is drawn in a low dew point nitrogen protective atmosphere, the key step is to coat it with a palladium-doped polyimide coating (inner protective layer) online, and then cure it through a high-temperature thermal imidization process. Subsequently, an outer protective resin is coated and cured with ultraviolet light (outer protective layer). This process avoids complex steps such as vacuum coating, is highly compatible with conventional optical fiber production lines, and significantly improves production efficiency and product consistency.

[0081] Test results demonstrate that this structure achieves a good balance between performance and cost. After 1000 hours of accelerated aging in a 5000 ppm hydrogen concentration environment, the increase in hydroxyl absorption loss at 1380 nm wavelength does not exceed 3.5 dB / km, meeting the requirements of most commercial applications. The transmission loss at 550 nm band remains stable at around 4.8 dB / km, indicating that the doped nanoparticles do not negatively affect the light guiding performance. This embodiment, through material innovation and structural optimization, successfully provides a more easily mass-producible and cost-effective hydrogen-resistant solar optical fiber solution.

[0082] Example 5

[0083] Reference Figure 6As shown, in response to the problem that traditional quartz optical fibers are prone to embrittlement and cracking in ultra-low temperature environments such as high-altitude cold regions in the north, cold chain storage, and polar research stations, this embodiment proposes an optical fiber. Its core innovation lies in significantly improving the mechanical reliability and optical stability of the optical fiber in the extreme environment of -60℃ through material modification, structural design, and low-temperature process control.

[0084] The optical fiber in this embodiment is largely the same as that in Embodiment 1, except that: the optical fiber in this embodiment adopts a three-layer composite structure: the optical core 2 is titanium-doped high-purity quartz (Ti content 0.05wt%), which uses titanium to enhance the toughness of the quartz matrix, and the finished diameter is 80 ± 0.2 μm; the capillary 3 is made of 6 low-hydroxyl quartz tubes (OH content <1ppm), with an outer diameter of 8 ± 0.1 μm and a wall thickness of 1.5 μm, which minimizes the generation of low-temperature microcracks; the outer sheath 1 is made of pure quartz with a wall thickness of 10 μm to ensure optical performance, and the outer periphery of the outer sheath 1 is coated with a perfluoroether rubber layer, which effectively buffers low-temperature shrinkage stress, and the total outer diameter is controlled at 140 ± 0.3 μm.

[0085] The key to the manufacturing process lies in low-temperature control throughout: the preform assembly uses epoxy adhesive cured at -10℃ for positioning; laser welding uses a 35W CO2 laser combined with -10℃ cold nitrogen for cooling, controlling the heat-affected zone to ≤ 30 μm; the wire drawing temperature is reduced to 1850℃, the speed is 8m / min, and the positive pressure inside the capillary preform is increased to 1.8kPa, while the negative pressure between the optical core 2 capillary preform, the capillary preform and the outer tube preform is set to -0.6kPa.

[0086] Performance tests show that this optical fiber performs excellently in an environment of -60℃: numerical aperture of 0.52 ± 0.02, transmission loss of 4.8 ± 0.4dB / km at 550nm, and minimum bending radius of 30mm. After aging at 85℃ / 90%RH for 1000 hours, the loss increment is <0.3dB / km, proving its excellent long-term reliability in extremely cold environments.

[0087] Example 6

[0088] Reference Figure 7 As shown, this embodiment provides an optical fiber for cost-sensitive scenarios such as rural schools and temporary venues. Its innovation lies in achieving a 30% cost reduction while maintaining acceptable performance indicators through material substitution, structural simplification, and process innovation.

[0089] The optical fiber in this embodiment has a similar structure to that in Embodiment 1, except that: the optical core 2 is made of industrial-grade high-purity quartz (OH content <5ppm) with a diameter of 120 ± 0.3 μm; the capillary 3 consists of six ordinary quartz tubes with an outer diameter of 12 ± 0.1 μm and a wall thickness of 2 μm; and the outer sheath 1 is made of high-transmittance PMMA material (refractive index 1.49) with an outer diameter of 200 ± 0.5 μm. This material combination significantly reduces material costs while maintaining optical performance.

[0090] The manufacturing process is as follows: the outer tube preform is mass-produced at low cost by extruding PMMA tubes; the capillary preform and the optical core preform are combined with mechanical positioning and local laser spot welding, each capillary preform only requires 3 welding points, and the positioning deviation is ±15 μm; a 25W semiconductor laser is used for laser welding, which shortens the welding time by 50%; the wire drawing temperature is adjusted to 200℃ to match the temperature resistance of PMMA, and the speed is increased to 25m / min, which significantly improves production efficiency.

[0091] The optical fiber has a measured numerical aperture of 0.48 ± 0.02 nm, a transmission loss of 6.2 ± 0.5 dB / km at 550 nm, a service life of 10 years at room temperature, and a manufacturing cost per meter reduced to 1.5 yuan. It delivers ≥700 lumens of luminous flux per 100 meters, capable of replacing a 60W incandescent bulb, providing an ideal basic lighting solution for cost-sensitive applications.

[0092] Example 7

[0093] Reference Figure 8 As shown, this embodiment proposes an optical fiber for special scenarios requiring ultraviolet filtration, such as museums, food processing plants, and medicinal plant cultivation. Its innovation lies in achieving efficient filtration of the 200-380nm ultraviolet band while maintaining excellent visible light guiding performance through material modification and nano-coating technology.

[0094] The optical fiber in this embodiment has a structure that is roughly the same as that in Embodiment 1, except that: the optical core 2 is made of UV-resistant quartz with 0.1wt% CeO2 added, with a diameter of 140 ± 0.3 μm, which effectively absorbs 200-300nm deep ultraviolet light; the inner walls of the eight pure quartz capillaries 3 are prepared with SiO2-TiO2 multilayer filter film by PCVD deposition technology, and the finished capillaries 3 have an outer diameter of 10 ± 0.1 μm and a wall thickness of 2μm, which can reflect 300-380nm near ultraviolet light; the outer sheath 1 is made of low-hydroxyl quartz with an outer diameter of 220 ± 0.2 μm to ensure mechanical strength.

[0095] The manufacturing process strictly controls process parameters: the PCVD deposition temperature is controlled at 1000℃ to ensure film uniformity of ±5%; during the preform assembly, the filter capillary preforms are precisely arranged along a 180mm diameter circumference; laser welding uses a 28W CO2 laser with a scanning speed of 6mm / s to avoid high temperature damage to the filter film structure.

[0096] Test data shows that the optical fiber has a transmittance of only 0.5% in the 200-380nm wavelength range, a transmittance of >90% in the 400-760nm visible light range, a numerical aperture of 0.54 ± 0.02, and a transmission loss of 4.8 ± 0.5dB / km at 550nm. After 1000 hours of irradiation testing, the color difference ΔE of the silk artifacts was <0.8, fully meeting the requirements of cultural relic protection standards.

[0097] Example 8

[0098] Reference Figure 9 As shown, in order to meet the special needs of highly corrosive environments such as marine platforms and chemical workshops, this embodiment has developed an optical fiber. Its innovation lies in achieving high tolerance to high salt spray and strong acid and alkali environments through material selection, surface treatment and protective coating technology.

[0099] The optical fiber in this embodiment has a structure that is largely the same as that in Embodiment 1, except that: the optical core 2 is made of 99.999% high-purity fused silica with a diameter of 100 ± 0.2 μm, which greatly reduces corrosion sites; eight fluorine-containing quartz capillaries 3 (F content 1.2wt%) surround the optical core 2 with an outer diameter of 9 ± 0.1 μm and a wall thickness of 2 μm, and the fluorine element effectively improves the acid and alkali resistance; the outer sheath 1 is made of fluorine-containing quartz with a wall thickness of 15 μm to enhance optical stability, and the outer periphery of the outer sheath 1 is coated with polytetrafluoroethylene to provide excellent corrosion protection, with a total outer diameter of 180 ± 0.3 μm.

[0100] The manufacturing process includes special treatment steps: the fluorine-containing quartz capillary preform and the optical core preform are soaked and cleaned in 10% HNO3 solution to remove surface impurities; high-purity argon gas is introduced during the laser welding process to prevent fluorine from reacting with oxygen; after drawing, a polytetrafluoroethylene coating is applied using a hot melt extrusion process to ensure a gapless interface.

[0101] According to national standard tests, after 1000 hours of salt spray testing in 5% NaCl solution, the polytetrafluoroethylene coating showed no peeling, the numerical aperture remained at 0.50 ± 0.02, and the transmission loss increment at 550nm was <0.5dB / km; after immersion in 10% H2SO4 solution for 500 hours, the mechanical strength retention rate was >85%, significantly better than the 65% of traditional optical fibers, proving its excellent corrosion resistance.

[0102] Example 9

[0103] Reference Figure 10 As shown, this embodiment proposes an optical fiber for applications such as ancient building restoration, internal medical equipment lighting, and micro-sensor lighting. The optical fiber in this embodiment has a similar structure to that in Embodiment 1, except that: the optical core 2 is an ultra-fine diameter high-purity quartz with a diameter of 40 ± 0.1 μm; the capillary 3 is an ultra-thin-walled quartz tube (wall thickness 1.5 μm) with an outer diameter of 6 ± 0.05 μm, and there are 4 of them. The "cross-symmetrical arrangement" is used instead of the equally spaced circular rings to simplify the structure; the outer sheath 1 is a 10 μm ultra-thin low-hydroxyl quartz with a total outer diameter of 80 ± 0.1 μm.

[0104] During fabrication, the outer diameter of the preform is 20 mm, the diameter of the optical core 2 preform is 8 mm, and four capillary preforms are arranged in a cross-shaped symmetrical pattern along the outer circumference of the optical core preform. A micron-level positioning platform (accuracy ± 1 μm) is used to ensure coaxiality. The drawing temperature is reduced to 1750℃ to prevent material melting, and the speed is 5 m / min to improve dimensional accuracy. Dynamic air pressure control accuracy is ± 0.05 kPa (P1=1.0 kPa, P2=-0.3 kPa) to prevent the collapse of the ultrathin-walled capillary 3. The finished product is inspected at the end face using a scanning electron microscope, and the coaxiality error is <0.5 μm. Tests show a total outer diameter of 78 ± 0.1 μm, NA=0.49 ± 0.02, a 550nm transmission loss of 5.2 ± 0.4 dB / km, a minimum bending radius of 20 mm (allowing it to pass through 1 mm gaps in ancient wooden structures), and an impact of <0.1% on the structural strength of ancient buildings after installation.

[0105] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An optical fiber, characterized in that, The device includes an outer tube (1), an optical core (2), and a capillary tube (3). The axes of the outer tube (1), the optical core (2), and the capillary tube (3) are parallel. The optical core (2) is located inside the outer tube (1). The capillary tube (3) is located between the inner circumferential surface of the outer tube (1) and the outer circumferential surface of the optical core (2). There are multiple capillary tubes (3). The multiple capillary tubes (3) are arranged at intervals around the optical core (2). Along the radial direction of the optical core (2), one end of the capillary tube (3) is connected to the outer circumferential surface of the optical core (2) by laser welding, and the other end is connected to the inner circumferential surface of the outer tube (1) by laser welding.

2. The optical fiber according to claim 1, characterized in that, The number of capillaries (3) is 4 to 12.

3. The optical fiber according to claim 2, characterized in that, The number of capillaries (3) is 8.

4. The optical fiber according to claim 1, characterized in that, The capillary (3) is made of pure quartz glass, and the outer diameter of the capillary (3) is 5 ~ 15 μm, and the wall thickness is 1 ~ 3 μm.

5. The optical fiber according to any one of claims 1-4, characterized in that, Multiple capillaries (3) are arranged at equal intervals.

6. The optical fiber according to any one of claims 1-4, characterized in that, The optical fiber has a first imaginary circle, which is arranged around the axis of the optical core (2), and the axes of a plurality of capillaries (3) are arranged on the first imaginary circle, wherein the diameter of the first imaginary circle is 170 ~ 1000 μm.

7. A method for fabricating optical fibers, suitable for fabricating optical fibers as described in any one of claims 1-6, characterized in that, Includes the following steps: A preform is provided, the preform comprising an outer tube preform, an optical core preform, and a capillary preform. The axes of the outer tube preform, the optical core preform, and the capillary preform are parallel. The optical core preform is disposed within the outer tube preform, and the capillary preform is disposed between the inner circumferential surface of the outer tube preform and the outer circumferential surface of the optical core preform. There are multiple capillary preforms, which are arranged at intervals around the optical core preform along the radial direction of the optical core preform. One end of each capillary preform is connected to the outer circumferential surface of the optical core preform by laser welding, and the other end is connected to the inner circumferential surface of the outer tube preform by laser welding. The preform is drawn to obtain the optical fiber. During the drawing process, a positive pressure P1 is applied to the cavity inside the capillary preform, while a negative pressure P2 is applied to the area between the inner circumferential surface of the outer sheath preform, the outer circumferential surface of the capillary preform, and the outer circumferential surface of the optical core preform. The absolute value of the negative pressure P2 is controlled to be less than the positive pressure P1 to prevent the capillary preform from collapsing during the drawing process.

8. The optical fiber fabrication method according to claim 7, characterized in that, The positive pressure P1 and the negative pressure P2 satisfy the following relationship: -0.5 P2 ≤ P1 ≤ -0.1 P2.

9. The optical fiber fabrication method according to claim 8, characterized in that, The control range of the positive pressure P1 is 1.0 kPa to 50.0 kPa, and the control range of the negative pressure P2 is -0.3 kPa to -15 kPa.

10. The optical fiber fabrication method according to claim 7, characterized in that, In the laser welding process, the laser is a CO2 laser with a power control range of 20 ~ 45 W and an equivalent welding temperature of 1750 ~ 1850℃.

11. The optical fiber fabrication method according to claim 7, characterized in that, The outer diameter of the outer cladding preform is D1mm; The outer diameter of the optical core preform is D2 mm; The preform has a second imaginary circle, which is arranged around the axis of the optical core preform, and the axes of the plurality of capillary preforms are arranged on the second imaginary circle, the diameter of the second imaginary circle being D3 mm; Among them, D2=(0.7~0.9)D1, D3=(0.8~0.95)D1, D3>D2.

Images