A gradient microstructure regulated high-uniformity side-emitting optical fiber and a preparation method thereof

Abstract

The application discloses a high-uniformity side-emitting optical fiber with gradient microstructure regulation and a preparation method thereof. 3+ / Er 3+ rare earth ions; the scattering light-emitting layer is made of Si / B / F / Al / Ti / Zr composite, a concentration gradient of 5% to 1% is realized in the radial direction by doping particles in the silicon-grade glass material, the refractive index is linearly reduced from 1.48 to 1.42, and the light field is guided to penetrate; and the cladding layer is a periodic gradient-depth micro-groove array, the groove depth is linearly increased from 2 to 5 microns along the axial two ends to the center, the interval is linearly decreased from 50 to 10 microns, and the optical transmission attenuation is compensated. The application realizes the structural cooperative design and process optimization, simplifies the preparation process and reduces the cost.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber technology and relates to a highly uniform side-emitting optical fiber with gradient microstructure control and its preparation method. This optical fiber can be widely used in flexible lighting, display backlighting, biomedical sensing and decorative lighting. Background Technology

[0002] Side-emitting fiber is a special type of fiber that emits light from the side while transmitting light, solving the spatial limitations of traditional point light sources and becoming a key component in special lighting and optical sensing. Currently, mainstream products such as Schott's Sidelight fiber and Corning's Fibrance® Light-Diffusing Fiber, while achieving side-emitting functionality, have the following technical limitations:

[0003] Schott Sidelight fiber: It achieves side emission by using doped scattering particles or macroscopic bending design, resulting in poor emission uniformity (brightness fluctuation along the fiber axis >20%) and significant attenuation of emission intensity with transmission distance; its fixed cladding structure makes the emission angle unadjustable (usually <60°), which cannot meet the lighting needs of complex scenes.

[0004] Corning Fibrance® fiber: Light diffusion is achieved through a nanoscale air hole array, which improves uniformity (fluctuation <15%). However, the fabrication of the nanostructure depends on a high-precision drawing tower, which is highly complex (requiring control of aperture deviation at the ±10nm level). The production cost is 3-5 times that of traditional optical fibers. Moreover, its luminous brightness is limited by the excitation light power, and it is impossible to achieve dynamic local brightness control.

[0005] In summary, existing side-emitting optical fibers generally suffer from four major problems: First, the manufacturing cost is too high, making it difficult to promote and apply on a large scale; second, the luminous effect weakens significantly with the increase of transmission distance, and the transmission attenuation problem is prominent; third, the luminous uniformity is insufficient, and dark spots, bright spots and yellow spots are easily generated when the fiber is bent; fourth, the luminous angle is fixed, which cannot adapt to the diverse lighting needs of different scenarios. Summary of the Invention

[0006] The purpose of this invention is to provide a highly uniform side-emitting optical fiber with gradient microstructure control and its fabrication method. Through structural co-design and process optimization, the invention achieves the technical goals of emission uniformity >90%, adjustable viewing angle of 30°-120°, and dynamic range of brightness >500 cd / m², while simplifying the fabrication process to reduce costs.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A highly uniform side-emitting optical fiber with gradient microstructure modulation comprises a core layer and a cladding layer, wherein a scattering emission layer is disposed between the core layer and the cladding layer; wherein...

[0009] The core layer is made of quartz glass doped with 0.5%-2% Ce by mass. 3+ / Er 3+ / Yb 3+ / Tm 3+ rare earth ions;

[0010] The scattering light-emitting layer is made of Si / B / F / Al / Ti / Zr composite glass material, with the internal doped particles distributed radially in a concentration gradient from 5% to 1%, and the refractive index linearly decreasing from 1.48 to 1.42.

[0011] The cladding is fluorine-doped silica glass with a periodically arranged gradient depth microgroove array on its surface. The groove cross-section is an isosceles triangle. The groove depth increases linearly from 2 μm to 5 μm along the fiber axis from both ends to the center. The groove spacing decreases linearly from 50 μm to 10 μm along the fiber axis from both ends to the center.

[0012] 2. The high-uniformity side-emitting optical fiber with gradient microstructure control according to claim 1, characterized in that the refractive index n1 of the core layer, the refractive index n3 of the scattering light-emitting layer, and the refractive index n2 of the cladding layer satisfy: n1≤n3 and n3>n2.

[0013] As a further improvement of the present invention, the scattering light-emitting layer (2) is a continuous annular layer that completely wraps the outer periphery of the core layer along the optical fiber axis.

[0014] As a further improvement of the present invention, it also includes a resin outer coating layer disposed on the outer surface of the coating layer for light uniformity and protection.

[0015] As a further improvement of the present invention, the core layer has a diameter of 50~250μm, the scattering light-emitting layer has a thickness of 0.5~3μm, the cladding layer has a thickness of 2~60μm, and the resin outer cladding layer has a thickness of 2~60μm.

[0016] As a further improvement of the present invention, wherein, by mass percentage:

[0017] The core layer comprises: SiO2 97.7~99.85%, Er2O3 0.02~0.08%, CeO2 0.02~0.05%, Yb2O3 0.1~0.5%, and Tm2O3 0.01~0.05%.

[0018] The scattering light-emitting layer comprises: 98-99% SiO2, 0-2% Al2O3, 0.05-0.3% nano TiO2, and 0.03-0.2% nano ZrO2;

[0019] The cladding layer contains: 93-97% SiO2, 2-6% B2O3, and 0.5-2% F.

[0020] The resin outer coating comprises: 53-55% polyurethane acrylate, 18-20% epoxy acrylate, 16.5-18.5% reactive diluent monomer, 1-3% photoinitiator, and 0.5-2% stabilizer.

[0021] As a further improvement of the present invention, the light emission angle can be continuously adjusted from 30° to 120° by adjusting the groove spacing to vary from 50μm to 10μm.

[0022] A method for fabricating the aforementioned side-emitting optical fiber includes the following steps:

[0023] S1. Preform preparation: Rare earth ion-doped SiO2 optical fiber preform core rods are prepared using VAD or MCVD methods, and Al / Ti / Zr-doped SiO2 outer cladding sleeves are prepared using OVD methods.

[0024] S2. Preform drawing: The preform is drawn in a high-temperature drawing furnace at 1700-1900℃ with a drawing speed of 100-800m / min and the fiber diameter is controlled to be ±2μm.

[0025] S3. Microstructure fabrication: Using ultraviolet laser direct writing technology with a wavelength of 355nm and a pulse width of 10ns, a gradient depth microgroove array is etched on the cladding surface. The groove depth is controlled to linearly increase from 2μm to 5μm from both ends to the center along the axial direction, while the spacing is linearly decreased from 50μm to 10μm, with a processing accuracy of ±0.5μm.

[0026] S4. Coating: The acrylic resin polymer is uniformly coated on the surface of the bare optical fiber at 180-220℃ and 5-8MPa. The coating speed is the same as the core layer feed speed.

[0027] S5. Annealing treatment: The processed optical fiber is annealed in a nitrogen or air atmosphere at 120℃-300℃ for 2 hours.

[0028] The above technical solution has the following beneficial effects:

[0029] 1. Significantly improved luminescence uniformity: Through the radial concentration / refractive index gradient design of the scattering luminescence layer, combined with axial gradient compensation of the groove depth and spacing on the cladding surface, the attenuation during light transmission is effectively offset, resulting in an axial luminescence uniformity of over 92% (measured fluctuation ≤3%), which is far superior to Schott Sidelight's ≤80% and Corning Fibrance's ≤85%.

[0030] 2. Flexible and controllable viewing angle and brightness: By simply adjusting the spacing of the grooves on the cladding surface (50μm→10μm), the luminous viewing angle can be continuously adjusted from 30° (narrow angle focusing) to 120° (wide angle illumination), breaking through the technical bottleneck of fixed viewing angle in existing products;

[0031] 3. Effective suppression of transmission attenuation: Ce in the core layer 3+ / Er 3+ The gain compensation effect of rare earth ions, combined with the light field guiding function of the scattering light-emitting layer, significantly reduces light transmission loss.

[0032] 4. Significantly reduced manufacturing costs: The use of ultraviolet laser direct writing technology replaces high-precision nanopore drawing, achieving a processing efficiency of 0.5 m / min. This eliminates the need for the high-precision nanopore drawing process relied upon by Corning Fibrance® (which costs 3-5 times more). The overall manufacturing cost of the optical fiber of this invention can be reduced to 40% of Corning's products, demonstrating significant economic advantages.

[0033] 5. Optimization of mechanical properties and luminous efficiency: After annealing, the fiber's breaking strength exceeds 500MPa, and the minimum bending radius can reach 5mm. The brightness attenuation during bending is less than 5%, exhibiting good flexibility and bending resistance, making it suitable for dynamic bending scenarios such as wearable devices and flexible lighting. Attached Figure Description

[0034] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0035] The structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0036] Figure 1 This is a schematic diagram of the high-uniformity side-emitting optical fiber structure provided by the present invention.

[0037] Figure 2 This is a schematic diagram of the groove distribution on the cladding layer provided by the present invention.

[0038] Figure 3 This is a schematic diagram of the preparation process provided by the present invention.

[0039] Figure 4 This is a schematic diagram of the bundled protection structure provided by the present invention.

[0040] Figure 5 This is a schematic diagram of light refraction within the cladding provided by the present invention.

[0041] Figure 6 for Figure 5 A schematic diagram of the cross-sectional structure.

[0042] In the picture:

[0043] 1. Core layer; 2. Scattering light-emitting layer; 3. Cladding layer; 31. Groove; 4. Resin outer cladding layer; 5. Optical fiber; 6. Protective sleeve. Detailed Implementation

[0044] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0045] like Figure 1 As shown, a highly uniform side-emitting optical fiber with gradient microstructure modulation includes a core layer 1 and a cladding layer 3, with a scattering emission layer 2 disposed between the core layer 1 and the cladding layer 3; wherein,

[0046] Core layer 1 is made of quartz glass doped with Ce by a mass fraction of 0.5%-2%. 3+ / Er 3+ / Yb / Tm rare earth ions are used for luminescence and light guiding to achieve light transmission and gain compensation;

[0047] The scattering light-emitting layer 2 is made of Si / B / F / Al / Ti / Zr composite material. The refractive index is linearly reduced from 1.48 to 1.42 by a radial concentration gradient of silicon-grade glass material doping particles from 5% to 1%, which is used for side emission modulation and guides the light field to penetrate outward. The gradient refractive index cladding layer 2 adopts a multi-layer composite structure design with the innermost layer having the highest refractive index (1.48) and the outermost layer having the lowest refractive index (1.42). By precisely controlling the refractive index distribution of each layer, a smooth gradient refractive index curve is formed.

[0048] Cladding 3, made of fluorine-doped silica glass with a refractive index n2 of 1.428–1.438, serves as both emission and protection. It features a periodically arranged array of gradient-depth microgrooves, such as… Figure 2As shown, the cross-section of the groove 31 is an isosceles triangle. The depth of the groove 31 increases linearly from 2μm to 5μm along the fiber axis from both ends to the center, while the spacing decreases linearly from 50μm to 10μm along the fiber axis from both ends to the center. The gradient changes in the depth and spacing of the groove 31 compensate for the light transmission attenuation, thereby achieving axial uniform light emission.

[0049] Simultaneously combined Figure 5 , Figure 6 As shown, by adjusting the spacing of the grooves 31 (50μm→10μm), the light emission angle can be continuously adjusted from 30° (narrow angle focusing) to 120° (wide angle illumination).

[0050] Furthermore, the refractive index n1 of the core layer 1, the refractive index n3 of the scattering light-emitting layer 2, and the refractive index n2 of the cladding layer 3 satisfy the following relationship: n1≤n3 and n3>n2.

[0051] Among them, the scattering light-emitting layer 2 is a continuous annular layer that completely wraps the outer periphery of the core layer 1 along the optical fiber axis.

[0052] The resin cladding layer 4 is located on the outermost layer of the optical fiber and serves for light homogenization and protection. Their respective thicknesses are as follows:

[0053] Core layer 1 diameter: 50~250μm

[0054] Thickness of the scattering light-emitting layer 2: 0.5~3μm

[0055] Cladding thickness 3: 2~60μm

[0056] Resin outer coating 4 thickness: 2~60μm.

[0057] The chemical compositions (by mass percentage) of the core layer 1, the light-emitting scattering layer 2, the cladding layer 3, and the resin outer cladding layer 4 in this design are as follows:

[0058] Core layer 1:

[0059] SiO2: 97.7~99.85%

[0060] Er2O3: 0.02~0.08%

[0061] CeO2: 0.02~0.05%

[0062] Yb₂O₃: 0.1~0.5%

[0063] Tm2O3: 0.01~0.05%;

[0064] Scattering light-emitting layer 2:

[0065] SiO2: 98~99%

[0066] Al2O30-2%

[0067] Nano TiO2: 0.05~0.3%

[0068] Nano ZrO2: 0.03~0.2%;

[0069] Encasing 3:

[0070] SiO2: 93~97%

[0071] B2O3: 2~6%

[0072] F element: 0.5~2%;

[0073] Resin outer layer 4:

[0074] Polyurethane acrylate: 53~55%

[0075] Epoxy acrylate: 18~20%

[0076] Reactive dilution monomer: 16.5%~18.5%

[0077] Photoinitiator: 1~3%

[0078] Stabilizer: 0.5~2%.

[0079] like Figure 4 As shown, after the optical fibers 5 are bundled, several optical fibers 5 with the above structure can be placed inside the protective sleeve 6.

[0080] A method for fabricating the side-emitting optical fiber as described above, such as... Figure 3 As shown, it includes the following steps:

[0081] S1. Preform preparation: Ce is prepared using VAD or MCVD methods. 3+ / Er 3+ / Yb / Tm doped SiO2 fiber preform core rod, Al / Ti / Zr doped SiO2 outer cladding sleeve prepared by OVD method, the relative concentration of scattering rod is matched to the fiber scattering brightness requirements by the scattering rod.

[0082] S2. Preform drawing: The preform is drawn in a high-temperature drawing furnace (1700-1900℃) with the drawing speed controlled at 100-800m / min to ensure the fiber diameter accuracy is ±2μm.

[0083] S3. Microstructure Fabrication: A gradient-depth microgroove array is etched on the cladding 3 surface using ultraviolet laser direct writing technology (wavelength 355nm, pulse width 10ns). The groove depth and spacing gradient are controlled by galvanometer scanning. Specifically, this involves precisely controlling the laser power and scanning speed to scan the fiber surface point by point, acquiring a large amount of three-dimensional coordinate information. The coordinates are analyzed and reconstructed through a data processing system to form a three-dimensional contour model. The laser path is planned to ensure processing according to a preset path. The preset pattern feature is an equilateral triangle with a side length of 5μm. This achieves a linear increase in groove depth from 2μm to 5μm along the fiber axis from both ends to the center, and a linear decrease in spacing from 50μm to 10μm along the fiber axis from both ends to the center. The processing accuracy reaches ±0.5μm, and the processing efficiency reaches 0.5m / min (3 times higher than Corning nanostructure technology).

[0084] S4. Coating: Acrylic resin polymer is used as the outer coating material of optical fiber and uniformly coated on the surface of bare optical fiber through a mold. Extrusion temperature: 180-220℃; Extrusion pressure: 5-8 MPa, to ensure that the extruded coating adheres tightly to the preform during the fiber drawing process; The coating speed is consistent with the core layer feed speed to achieve synchronous operation.

[0085] S5. Annealing treatment: The processed optical fiber is placed in a nitrogen / natural air atmosphere at 120℃-300℃ for 2 hours to eliminate laser processing stress and improve the mechanical strength of the optical fiber (fracture strength >500MPa).

[0086] Example 1: Highly Uniform Flexible Illumination Fiber

[0087] 1. Material selection and structural parameters

[0088] Core layer 1: SiO2: 97.7~99.85% + Er2O3: 0.02~0.08% + CeO2: 0.02~0.05% + Yb2O3: 0.1~0.5% + Tm2O3: 0.01~0.05%, diameter 100μm.

[0089] Scattering light-emitting layer 2: 98~99% + Al2O3 0-2% + nano TiO2: 0.05~0.3% + nano ZrO2: 0.03~0.2%, diameter 2μm.

[0090] Cladding 3: SiO2: 93~97% + B2O3: 2~6% + F element: 0.5~2%. The refractive index is linearly reduced from 1.48 to 1.42 by a radial concentration gradient of silicon-grade glass material doping particles from 5% to 1%, with a diameter of 30μm.

[0091] The grooves in cladding 3 have a linearly decreasing spacing of 50 μm to 10 μm, a depth gradient of 2 → 5 μm (along a 1 m fiber), and an apex angle of 60°.

[0092] Resin outer coating 4: Polyurethane acrylate: 53~55% + Epoxy acrylate: 18~20% + Reactive diluent monomer: 16.5~18.5% + Photoinitiator: 1~3% + Stabilizer: 0.5~2%.

[0093] 2. Performance Test Results

[0094] At an input power of 1W, the axial luminous uniformity is 92% (520 cd / m² at 50cm, 505 cd / m² at 100cm, with a fluctuation of 3%).

[0095] It has a 60° viewing angle, a minimum bending radius of 5mm, and a brightness attenuation of less than 5% when bent.

[0096] The manufacturing cost is reduced to 40% of that of Corning Fibrance® fiber, giving it a significant cost advantage.

[0097] Example 2: Narrow-angle focusing fiber

[0098] 1. Material selection and structural parameters

[0099] The core layer 1 has the following chemical composition (mass percentage): SiO2: 95~98% + Er2O3: 0.03~0.1% + CeO2: 0.01~0.04% + Yb2O3: 0.2~0.6% + Tm2O3: 0.03~0.05%, with a diameter of 100μm.

[0100] The scattering light-emitting layer 2 has the following chemical composition (mass percentage): SiO2: 97~98.5% + Al2O3 0-1% + nano TiO2: 0.05~0.2% + nano ZrO2: 0.05~0.3%, with a diameter of 1μm.

[0101] Cladding 3: SiO2: 94~98% + B2O3: 2.5~7% + F element: 0.3~2.2%. The refractive index is linearly reduced from 1.48 to 1.42 by a radial concentration gradient of silicon-grade glass material doping particles from 5% to 1%, with a diameter of 35μm.

[0102] Cladding grooves: the spacing is adjusted to 10μm, the apex angle is 90°, and the depth increases linearly from 2μm to 5μm along the fiber axis.

[0103] The resin outer coating 4 is composed of the following chemical components (by mass percentage): polyurethane acrylate: 52.3~54% + epoxy acrylate: 19.2~21% + reactive diluent monomer: 13.5~16.5% + photoinitiator: 0.52~2.5% + stabilizer: 1~3.5%.

[0104] 2. Performance Test Results

[0105] The light-emitting angle is 35°, achieving a narrow-angle focusing effect;

[0106] The center brightness reaches 2100 cd / m², which is 3 times higher than that of Example 1, and is suitable for scenarios with high requirements for directional focusing, such as indicator lights of precision instruments.

[0107] This invention addresses the problems of insufficient uniformity of light emission, fixed viewing angle, difficulty in brightness control, and high fabrication cost in existing side-emitting optical fibers. Through the synergistic design of the scattering light-emitting layer and microstructure control, it overcomes the uniformity bottleneck of Schott Sidelight optical fibers and the cost limitations of Corning Fibrance®, achieving an integrated solution of "high uniformity, wide viewing angle control, and low-cost fabrication." It boasts luminous uniformity (>90%), an adjustable viewing angle of 30°-120°, a brightness dynamic range >500 cd / m², and simplifies the fabrication process to reduce costs.

[0108] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0109] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly uniform side-emitting optical fiber with gradient microstructure modulation, characterized in that, A core layer (1) and a cladding layer (3) are provided, wherein a light-emitting scattering layer (2) is disposed between the core layer (1) and the cladding layer (3); wherein, The core layer (1) is made of quartz glass doped with Ce by a mass fraction of 0.5%-2%. 3+ / Er 3+ / Yb 3+ / Tm 3+ rare earth ions; The scattering light-emitting layer (2) is made of Si / B / F / Al / Ti / Zr composite glass material, with the internal doped particles distributed in a radial gradient from 5% to 1%, and the refractive index linearly decreasing from 1.48 to 1.

42. The cladding (3) is fluorine-doped silica glass with a periodically arranged gradient depth microgroove array on its surface. The groove (31) has an isosceles triangle cross section. The groove depth increases linearly from 2 μm to 5 μm along the fiber axis from both ends to the center. The groove spacing decreases linearly from 50 μm to 10 μm along the fiber axis from both ends to the center.

2. The high-uniformity side-emitting optical fiber with gradient microstructure modulation according to claim 1, characterized in that, The refractive index n1 of the core layer (1), the refractive index n3 of the scattering light-emitting layer (2), and the refractive index n2 of the cladding layer (3) satisfy: n1≤n3 and n3>n2.

3. The highly uniform side-emitting optical fiber with gradient microstructure modulation according to claim 1, characterized in that, The scattering light-emitting layer (2) is a continuous annular layer that completely wraps around the outer periphery of the core layer (1) along the optical fiber axis.

4. The high-uniformity side-emitting optical fiber with gradient microstructure modulation according to claim 1, characterized in that, It also includes a resin outer coating (4), which is disposed on the outer surface of the coating (3) for light uniformity and protection.

5. The high-uniformity side-emitting optical fiber with gradient microstructure modulation according to claim 4, characterized in that, The core layer (1) has a diameter of 50~250μm, the scattering light-emitting layer (2) has a thickness of 0.5~3μm, the cladding layer (3) has a thickness of 2~60μm, and the resin outer cladding layer (4) has a thickness of 2~60μm.

6. The highly uniform side-emitting optical fiber with gradient microstructure modulation according to claim 1, characterized in that, By weight percentage: The core layer (1) comprises: SiO2 97.7~99.85%, Er2O3 0.02~0.08%, CeO2 0.02~0.05%, Yb2O3 0.1~0.5%, and Tm2O3 0.01~0.05%; The scattering light-emitting layer (2) comprises: 98-99% SiO2, 0-2% Al2O3, 0.05-0.3% nano TiO2, and 0.03-0.2% nano ZrO2; The cladding (3) contains: 93-97% SiO2, 2-6% B2O3, and 0.5-2% F. The resin outer coating (4) comprises: 53-55% polyurethane acrylate, 18-20% epoxy acrylate, 16.5-18.5% reactive diluent monomer, 1-3% photoinitiator, and 0.5-2% stabilizer.

7. The high-uniformity side-emitting optical fiber with gradient microstructure modulation according to claim 1, characterized in that, By adjusting the groove spacing from 50μm to 10μm, the light emission angle can be continuously adjusted from 30° to 120°.

8. A method for preparing a side-emitting optical fiber as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Preform preparation: Rare earth ion-doped SiO2 optical fiber preform core rods are prepared using VAD or MCVD methods, and Al / Ti / Zr-doped SiO2 outer cladding sleeves are prepared using OVD methods. S2. Preform drawing: The preform is drawn in a high-temperature drawing furnace at 1700-1900℃ with a drawing speed of 100-800m / min and the fiber diameter is controlled to be ±2μm. S3. Microstructure fabrication: Using ultraviolet laser direct writing technology with a wavelength of 355nm and a pulse width of 10ns, a gradient depth microgroove array is etched on the cladding surface. The groove depth is controlled to linearly increase from 2μm to 5μm from both ends to the center along the axial direction, while the spacing is linearly decreased from 50μm to 10μm, with a processing accuracy of ±0.5μm. S4. Coating: The acrylic resin polymer is uniformly coated on the surface of the bare optical fiber at 180-220℃ and 5-8MPa. The coating speed is the same as the core layer feed speed. S5. Annealing treatment: The processed optical fiber is annealed in a nitrogen or air atmosphere at 120℃-300℃ for 2 hours.

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