Extrusion preparation method of chalcogenide glass node-free hollow-core anti-resonance optical fiber preform

Abstract

The invention discloses an extrusion preparation method of a chalcogenide glass node-free hollow-core anti-resonance optical fiber preform. The preparation method comprises the following steps: firstly, preparing chalcogenide glass by adopting a melting-quenching method, and processing the chalcogenide glass into round-rod-shaped preform glass with a smooth surface; then putting the preform glass into a hollow-core anti-resonance optical fiber preform extrusion forming mold, and putting the preform glass and the hollow-core anti-resonance optical fiber preform extrusion forming mold into a heating furnace; and finally, heating the glass to a softened state, and applying pressure by a piston to extrude the glass out of a mold forming nozzle to obtain the optical fiber preform. The method has the advantages of high preparation efficiency, good structural uniformity, controllable cladding pipe wall thickness tolerance, high preform surface quality and the like, and the mold is convenient to maintain and high in adaptability.

Description

Technical Field

[0001] This invention relates to the field of optical fiber fabrication technology, specifically to an extrusion method for preparing nodeless hollow anti-resonant optical fiber preforms from chalcogenide glass. Background Technology

[0002] Anti-resonant hollow fiber (AR-HCF) is a novel type of hollow fiber developed in the last two decades. It features a high laser damage threshold, low transmission loss, and large transmission bandwidth, making it highly promising for high-power, high-beam-quality laser transmission. The light-guiding characteristics of AR-HCF are primarily determined by its unique fiber structure. A key feature of this structure is that its cladding consists of capillaries arranged around the core, with the core wall exhibiting an inverse curvature relative to the core. Its guiding mechanism can be explained using the anti-resonant optical waveguide (ARROW) theory: in the resonant band, energy in the core couples into the core wall, resulting in extremely high leakage loss; while in the anti-resonant band, multi-beam interference formed in the core wall reflects most of the energy back to the core, significantly reducing leakage loss. The core wall thickness and fiber structure directly determine the position of the anti-resonant band, playing a decisive role in fiber loss. Within the anti-resonant transmission band, the interaction between light and the cladding material is weak, and the transmission characteristics are less affected by the properties of the cladding material itself; therefore, its transmission loss can exceed the intrinsic absorption limit of the material. For example, the low-loss transmission wavelength of quartz glass hollow antiresonant fiber can reach above 5 μm, far exceeding the material transmission limit of quartz glass (2 μm). However, in the mid- and far-infrared bands, the absorption coefficient of quartz increases sharply, resulting in losses in quartz-based hollow antiresonant fibers typically exceeding 10 dB / m at wavelengths above 7 μm, making it difficult to meet practical application requirements. Chalcogenide glasses, with their high transmittance in the mid- and far-infrared bands, are ideal matrix materials for fabricating mid- and far-infrared hollow antiresonant fibers.

[0003] Hollow-core antiresonant optical fibers are typically fabricated using a stacking method, where cladding tubes are arranged in an orderly fashion on the inner wall of an outer tube to form an optical fiber preform. This preform is then drawn into a thin rod, and finally, the thin rod is drawn into an optical fiber. However, during the drawing process, the cladding tubes are prone to displacement, causing fiber structure deformation and increasing fiber loss. Furthermore, this method places extremely high demands on the wall thickness of the cladding tubes and their radial and axial consistency. Unlike commercially available high-quality silica cladding tubes, the fabrication of thin-walled chalcogenide glass cladding tubes with high dimensional uniformity remains challenging, which also poses difficulties for the manufacture of chalcogenide glass hollow-core antiresonant optical fibers. Summary of the Invention

[0004] The purpose of this invention is to propose an extrusion preparation method for nodeless hollow anti-resonant optical fiber preforms of chalcogenide glass, so as to solve the problems of easy displacement of cladding tube and poor wall thickness uniformity in the preparation of hollow anti-resonant optical fiber preforms of chalcogenide glass in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for extruding nodeless hollow anti-resonant optical fiber preforms from chalcogenide glass includes the following steps: Step 1: Prepare chalcogenide glass in a vacuum quartz ampoule using a melt-quench method; Step 2: Process the chalcogenide glass obtained in Step 1 into a smooth, cylindrical preform glass. Step 3: Prepare a set of hollow anti-resonant optical fiber preform extrusion molding die. The hollow anti-resonant optical fiber preform extrusion molding die includes a piston, a sleeve with a discharge through hole at the bottom, and a forming nozzle. The forming nozzle, the preformed glass obtained in Step 2, and the piston are sequentially placed into the sleeve. The forming nozzle is installed at the center of the discharge through hole. The forming nozzle includes an outer ring, an inner ring, and round rods. The outer ring is connected to the inner ring, and an outer layer tube injection hole is provided between them. A blind hole is provided at the center of the inner ring. Several evenly distributed round rods are provided around the lower perimeter of the inner ring. Several cladding tube injection holes corresponding to the round rods are provided on the blind holes. A cladding tube forming hole is provided between the blind hole and the round rod. An outer layer tube forming hole is provided between the inner wall of the discharge through hole and the outer wall of the inner ring. The number of round rods is a positive integer greater than 5. Step 4: Place the hollow anti-resonant optical fiber preform extrusion mold containing the preformed glass into the heating furnace of the extruder, and then heat the furnace to soften the preformed glass. Step 5: The extruder applies pressure to the pre-shaped glass through the piston. The pre-shaped glass is extruded from the outlet of the forming nozzle in a softened state. After passing through the forming nozzle, the pre-shaped glass forms a hollow anti-resonant optical fiber preform. The pre-shaped glass is extruded through the outer tube forming hole to form the outer tube. At the same time, the pre-shaped glass flowing through the cladding tube forming hole is divided into several cladding tubes that adhere to the inner wall of the outer tube by the evenly distributed round rods. The hollow area enclosed by the several cladding tubes constitutes the fiber core area. Step 6: After extrusion, remove the hollow anti-resonant optical fiber preform and place it in a precision annealing furnace for annealing.

[0006] As a further improvement of the present invention, the surface roughness of the pre-shaped glass R a <100 nm.

[0007] As a further improvement of the present invention, the diameter of the forming hole of the cladding tube is 0.6~0.9 mm larger than the diameter of the round bar.

[0008] As a further improvement of the present invention, in step 4, protective gas nitrogen or argon is continuously introduced into the furnace cavity of the heating furnace until the extrusion is completed.

[0009] As a further improvement of the present invention, in step 5, the pressure applied by the piston to the preformed glass is 1.5~3.0 MPa.

[0010] As a further improvement of the present invention, in step 6, the annealing temperature of the hollow anti-resonant optical fiber preform is 5-10 °C lower than its glass transition temperature.

[0011] Compared with the prior art, the present invention has the following technical advantages: (1) The extrusion method of the present invention prepares hollow anti-resonant optical fiber preforms for chalcogenide glass, which can realize one-time precise co-forming of the cladding tube and the outer tube structure, fundamentally solving the technical problem of cladding tube displacement in traditional step-by-step preparation, and simplifying the process steps, making operation convenient, and significantly improving preparation efficiency and product consistency. (2) The prepared hollow anti-resonant fiber preform has excellent geometric uniformity: the cladding tube wall thickness tolerance is controlled within ±1%, and the diameter tolerance is controlled within ±2%; at the same time, the preform surface has high optical quality and low average roughness. R a <100 nm, providing a high-quality preform foundation for subsequent low-loss fiber drawing; (3) The hollow anti-resonant optical fiber preform extrusion molding die of the present invention is reasonably designed, and its molding nozzle adopts a modular and detachable design, which is convenient for cleaning and maintenance. By replacing the molding nozzle of different specifications, it can quickly adapt to the preparation requirements of preforms with different structural parameters, saving manufacturing costs and production preparation time. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the extrusion molding die for the hollow anti-resonant optical fiber preform used in the preparation method of the present invention. Figure 2 This is a schematic diagram of the structure of the forming nozzle and the discharge through hole after the sleeve is installed in the preparation method of the present invention. Figure 3 This is a schematic cross-sectional view of the molding nozzle and sleeve after installation in the preparation method of the present invention. Figure 4 A schematic diagram of the hollow anti-resonant optical fiber preform structure prepared by the method of the present invention; Figure 5 Photograph of the 6-unit hollow anti-resonant optical fiber preform prepared in Embodiment 1 of the present invention; Figure 6 This is a photograph of the 8-unit hollow anti-resonant optical fiber preform prepared in Embodiment 2 of the present invention.

[0013] In the diagram: 1-Piston; 2-Sleeve; 3-Forming nozzle; 4-Preform glass; 3-1-Outer ring; 3-2-Inner ring; 3-3-Round bar; 3-4-Blind hole; 3-5-Clad tube injection hole; 3-6-Outer tube injection hole; 3-7-Outer tube forming hole; 3-8-Clad tube forming hole; 5-Hollow core anti-resonant optical fiber preform; 5-1-Outer tube; 5-2-Clad tube; 5-3-Core region. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015]

Example 1

[0016] The specific process is as follows: Step 1: Prepare Ge in a vacuum quartz ampoule using a melt-quench method. 12 As 24 Se 64 Glass.

[0017] Step 2: Process the obtained chalcogenide glass into smooth, cylindrical pre-shaped glass bodies. The surface roughness of the glass is... R a =98 nm.

[0018] Step 3: Prepare a set of hollow anti-resonant optical fiber preform extrusion molding molds, such as... Figure 1 As shown, the mold includes a piston 1, a sleeve 2, and a forming nozzle 3. The sleeve 2 has a discharge port at its bottom; the forming nozzle 3 is manufactured using metal 3D printing. The forming nozzle 3, the pre-shaped glass 4 obtained in step 2, and the piston 1 are sequentially placed into the sleeve 2; the forming nozzle 3 is located at the center of the discharge port. Specifically, as... Figure 2 and Figure 3 As shown, the forming nozzle 3 includes an outer ring 3-1, an inner ring 3-2, and a round bar 3-3. The outer ring 3-1 is connected to the inner ring 3-2, and an outer tube injection hole 3-6 is provided between them. A blind hole 3-4 is provided at the center of the inner ring 3-2. Six evenly distributed round bars 3-3 are provided around the lower perimeter of the inner ring 3-2. Six cladding tube injection holes 3-5 corresponding to the round bars 3-3 are provided on the blind hole 3-4. A cladding tube forming hole 3-8 is provided between the blind hole 3-4 and the round bars 3-3. An outer tube forming hole 3-7 is provided between the inner wall of the discharge through hole and the outer wall of the inner ring 3-2. The diameter of the cladding tube forming hole 3-8 is 5.0 mm, and the diameter of the round bar 3-3 is 4.4 mm.

[0019] Step 4: Place the hollow anti-resonant optical fiber preform extrusion mold containing the preformed glass into the heating furnace of the extruder, and then heat the furnace to soften the preformed glass.

[0020] Step 5: The extruder is operated to apply a pressure of 3 MPa to the preformed glass through the piston. The preformed glass is extruded from the outlet of the forming nozzle 3 in a softened state. Due to the constraint of the outlet shape of the forming nozzle 3, the preformed glass forms a hollow anti-resonant optical fiber preform 5 after passing through the forming nozzle.

[0021] like Figure 4 As shown, the preformed glass is extruded through the outer tube forming hole 3-7 to form the outer tube 5-1; at the same time, the preformed glass flowing through the cladding tube forming hole 3-8 is divided into 6 cladding tubes 5-2 that are adhered to the inner wall of the outer tube by the evenly distributed round rods 3-3; the hollow area enclosed by the 6 cladding tubes 5-2 constitutes the core area 5-3. Step 6: After extrusion, remove the hollow anti-resonant fiber preform 5 and place it in a precision annealing furnace for annealing. The annealing temperature is 10 °C lower than its glass transition temperature. After annealing, a 6-unit Ge structure is obtained. 12 As 24 Se 64 Glass hollow antiresonant optical fiber preform, such as Figure 5 As shown.

[0022] The obtained preform was characterized: A 20 cm long preform was measured with vernier calipers, and its diameter was found to be 14.82 ± 0.26 mm. Microscopic observation of the preform cross-section revealed a distance of 2.4 ± 0.1 mm between adjacent cladding tube edges and a cladding tube wall thickness of 301.2 ± 2.9 μm. Further measurements of the glass surface roughness were performed using a white light interferometer, and the results were as follows: R a =96nm.

[0023]

Example 2

[0024] The specific process is as follows: Step 1: Prepare Ge in a vacuum quartz ampoule using a melt-quench method. 10 As 30 Se 40 Te 20 Glass.

[0025] Step 2: Process the obtained chalcogenide glass into smooth, cylindrical pre-shaped glass bodies. The surface roughness of the glass is... R a =82 nm.

[0026] Step 3: Prepare a set of hollow anti-resonant optical fiber preform extrusion molding molds, such as... Figure 1 As shown, the mold includes a piston 1, a sleeve 2, and a forming nozzle 3. The sleeve 2 has a discharge port at its bottom; the forming nozzle 3 is manufactured using metal 3D printing. The forming nozzle 3, the pre-shaped glass 4 obtained in step 2, and the piston 1 are sequentially placed into the sleeve 2; the forming nozzle 3 is located at the center of the discharge port. Figure 2 and Figure 3 As shown, the forming nozzle 3 includes an outer ring 3-1, an inner ring 3-2, and a round bar 3-3; the outer ring 3-1 is connected to the inner ring 3-2, and an outer tube injection hole 3-6 is provided between them; a blind hole 3-4 is provided in the center of the inner ring 3-2; eight evenly distributed round bars 3-3 are provided around the lower periphery of the inner ring 3-2; eight cladding tube injection holes 3-5 corresponding to the round bars 3-3 are provided on the blind hole 3-4; a cladding tube forming hole 3-8 is provided between the blind hole 3-4 and the round bars 3-3; an outer tube forming hole 3-7 is provided between the inner sidewall of the discharge through hole and the outer sidewall of the inner ring 3-2; the diameter of the cladding tube forming hole 3-8 is 5.0 mm, and the diameter of the round bar 3-3 is 4.1 mm.

[0027] Step 4: Place the hollow anti-resonant optical fiber preform extrusion mold containing the preformed glass into the heating furnace of the extruder, and then heat the furnace to soften the preformed glass.

[0028] Step 5: The extruder applies a pressure of 1.5 MPa to the preformed glass through the piston. The preformed glass is extruded from the outlet of the forming nozzle 3 in a softened state. Due to the constraint of the outlet shape of the forming nozzle 3, the preformed glass forms a hollow anti-resonant optical fiber preform 5 after passing through the forming nozzle.

[0029] like Figure 4 As shown, the preformed glass is extruded through the outer tube forming hole 3-7 to form the outer tube 5-1; at the same time, the preformed glass flowing through the cladding tube forming hole 3-8 is divided into 8 cladding tubes 5-2 that are adhered to the inner wall of the outer tube by the evenly distributed round rods 3-3; the hollow area enclosed by the 8 cladding tubes 5-2 constitutes the core area 5-3.

[0030] Step 6: After extrusion, remove the hollow anti-resonant fiber preform 5 and place it in a precision annealing furnace for annealing. The annealing temperature is 5°C lower than its glass transition temperature. After annealing, an 8-unit Ge structure is obtained. 10 As 30 Se 40 Te 20Glass hollow antiresonant optical fiber preform, such as Figure 6 As shown.

[0031] The obtained preform was characterized: A 20 cm long preform was measured with vernier calipers, and its diameter was found to be 18.12 ± 0.34 mm. Microscopic observation of the preform cross-section revealed a distance of 1.8 ± 0.1 mm between adjacent cladding tube edges and a cladding tube wall thickness of 451.3 ± 3.2 μm. Further measurement of the glass surface roughness using a white light interferometer yielded the following results: R a =72nm.

[0032] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A method for extruding nodeless hollow anti-resonant optical fiber preforms from chalcogenide glass, characterized in that, Includes the following steps: Step 1: Prepare chalcogenide glass in a vacuum quartz ampoule using a melt-quench method; Step 2: Process the chalcogenide glass obtained in Step 1 into a smooth, cylindrical preform glass. Step 3: Prepare a set of hollow anti-resonant optical fiber preform extrusion molding die. The hollow anti-resonant optical fiber preform extrusion molding die includes a piston, a sleeve with a discharge through hole at the bottom, and a forming nozzle. The forming nozzle, the preformed glass obtained in Step 2, and the piston are sequentially placed into the sleeve. The forming nozzle is installed at the center of the discharge through hole. The forming nozzle includes an outer ring, an inner ring, and round rods. The outer ring is connected to the inner ring, and an outer layer tube injection hole is provided between them. A blind hole is provided at the center of the inner ring. Several evenly distributed round rods are provided around the lower perimeter of the inner ring. Several cladding tube injection holes corresponding to the round rods are provided on the blind hole. A cladding tube forming hole is provided between the blind hole and the round rod. An outer layer tube forming hole is provided between the inner wall of the discharge through hole and the outer wall of the inner ring. The number of round rods is a positive integer greater than 5. Step 4: Place the hollow anti-resonant optical fiber preform extrusion mold containing the preformed glass into the heating furnace of the extruder, and then heat the furnace to soften the preformed glass. Step 5: The extruder applies pressure to the pre-shaped glass through the piston. The pre-shaped glass is extruded from the outlet of the forming nozzle in a softened state. After passing through the forming nozzle, the pre-shaped glass forms a hollow anti-resonant optical fiber preform. The pre-shaped glass is extruded through the outer tube forming hole to form the outer tube. At the same time, the pre-shaped glass flowing through the cladding tube forming hole is divided into several cladding tubes that adhere to the inner wall of the outer tube by the evenly distributed round rods. The hollow area enclosed by the several cladding tubes constitutes the fiber core area. Step 6: After extrusion, remove the hollow anti-resonant optical fiber preform and place it in a precision annealing furnace for annealing.

2. The extrusion preparation method of nodeless hollow anti-resonant optical fiber preform of chalcogenide glass according to claim 1, characterized in that, Surface roughness of the preformed glass R a <100 nm.

3. The extrusion preparation method of the node-free hollow anti-resonant optical fiber preform of chalcogenide glass according to claim 1, characterized in that, The diameter of the forming hole in the cladding tube is 0.6 to 0.9 mm larger than the diameter of the round bar.

4. The extrusion preparation method of nodeless hollow anti-resonant optical fiber preform of chalcogenide glass according to claim 1, characterized in that, In step 4, protective gases, such as nitrogen or argon, are continuously introduced into the furnace chamber of the heating furnace until the extrusion is completed.

5. The extrusion preparation method of nodeless hollow anti-resonant optical fiber preform of chalcogenide glass according to claim 1, characterized in that, In step 5, the piston applies a pressure of 1.5 to 3.0 MPa to the preformed glass.

6. The extrusion preparation method of nodeless hollow anti-resonant optical fiber preform of chalcogenide glass according to claim 1, characterized in that, In step 6, the annealing temperature of the hollow anti-resonant optical fiber preform is 5-10°C lower than its glass transition temperature.

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