A method for preparing a fully doped hollow-core anti-resonant actively guided optical fiber preform

Abstract

The application provides a preparation method of a full-doped hollow anti-resonant active optical fiber preform, and belongs to the technical field of optical fiber preparation. First, nano-silicon dioxide and photosensitive resin raw materials are mixed to obtain a printing base material, and then DLP photocuring 3D printing is performed. The method can meet the design requirements of the complex structure of the optical fiber preform, is simple in method, and is uniform in thickness. Then, organic monomers are removed through heat treatment, and then a rare earth source and / or bismuth source solution is impregnated for doping. The doping method is simple and uniform. Finally, sintering is performed to densify the silicon dioxide, so that the full-doped hollow anti-resonant active optical fiber preform is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber preparation, and particularly relates to a preparation method of a full-doped hollow-core antiresonant active optical fiber preform. BACKGROUND

[0002] In the 21st century, with the continuous explosive growth of demand for information transmission capacity, the intrinsic defects of quartz optical fiber such as nonlinearity, dispersion, irradiation damage, and non-transmission of ultraviolet and infrared light have become more and more obvious in restricting the development of the field of optical communication. The antiresonant hollow-core fiber based on the antiresonant reflection optical waveguide effect confines light energy in the air core. Compared with solid-core optical fibers, the hollow-core fiber has been widely concerned and researched due to its wideband low transmission loss, small nonlinear coefficient, and low transmission delay. The transmission loss of various structures of antiresonant hollow-core fibers has continuously reached a new low loss record, especially the nested ring nodeless antiresonant hollow-core fiber (NANF). Gregory TJasion of the University of Southampton in the UK and others have achieved a series of low-loss NANFs. In 2018, they obtained a six-ring NANF with a transmission loss of <1.4 dB / km and a 40 nm transmission bandwidth. In 2019, they achieved a low transmission loss of 0.65 dB / km in the entire C+L communication band. In 2020, Gregory T Jasion and others further improved the structure design, and the transmission loss of the 1.51-1.6 μm band was further reduced to 0.28 dB / km. In 2022, Gregory T Jasion and others increased a layer of nested structure and achieved a low transmission loss record of 0.174 dB / km in the C-band in a 5-ring NANF. The transmission loss of the antiresonant hollow-core fiber in the C+L communication band continues to reach a new low, and the theoretical prediction in “Opportunities and Challenges for Long-Distance Transmission in Hollow-Core Fibers” published in the Journal of Lightwave Technology in 2022 predicts that when the loss of the nested ring nodeless antiresonant hollow-core fiber NANF is lower than that of a single-mode optical fiber, a 200-300 km non-repeater amplification transmission can be achieved. If an antiresonant hollow-core active optical fiber is realized, it is possible to achieve ultra-long distance transmission.

[0003] The existing method for preparing the anti-resonance hollow core optical fiber with a complex structure is a rod tube stacking method: a capillary tube with a required diameter is drawn by using a glass tube, and then the capillary tube is inserted into a quartz tube, and the two are fused together by heating and melting, but the thickness of the optical fiber preform prepared by this method is uneven, and can only be used for producing optical fibers with relatively simple structures, and cannot meet the needs of the anti-resonance hollow core optical fiber with a complex structure. Moreover, the existing method for doping the hollow anti-resonance optical fiber is improved chemical vapor deposition (MCVD) or outside vapor deposition (OVD). A rare earth doped hollow anti-resonance optical fiber is disclosed in Chinese Patent CN113497404B, which uses the MCVD or OVD method to dope the rare earth on the entire cladding glass tube ring; and Chinese Patent CN219065790U uses the non-rotating MCVD method to perform partial circumferential rare earth doping on the nested outer tube. Due to the inherent characteristics of the MCVD or OVD deposition method, the complete doping of the entire cladding tube ring will cause there to be an undoped layer outside or inside the doped tube, and if the undoped area is to be removed, additional processing is required to remove the undoped layer, which increases the preparation cost and may affect the performance of the optical fiber after the removal.

[0004] In summary, the current method for preparing the doped hollow anti-resonance active optical fiber cannot meet the design needs of the hollow anti-resonance optical fiber with a complex structure, and the preparation method is complex, the thickness of the prepared product is uneven, and the preparation cost is high. Therefore, there is an urgent need for a full-doped hollow anti-resonance active optical fiber preparation method that can meet the design needs of the hollow anti-resonance optical fiber with a complex structure, and can achieve a simple and controllable method and uniform thickness. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a full-doped hollow anti-resonance active optical fiber preform. The preparation method provided by the present application is simple, and the thickness of the prepared active optical fiber preform is uniform.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a preparation method of a full-doped hollow anti-resonance active optical fiber preform, comprising the following steps:

[0008] (1) mixing nanosilica and photosensitive resin raw materials to obtain a printing substrate;

[0009] (2) performing DLP photocuring 3D printing on the printing substrate obtained in step (1) to obtain a green body;

[0010] (3) performing heat treatment on the green body obtained in step (2) to obtain a preform precursor;

[0011] (4) immersing the preform precursor obtained in step (3) in a solution of a rare earth source and / or a bismuth source to obtain a doped preform precursor;

[0012] (5) sintering the doped preform precursor obtained in step (4) to obtain a fully-doped hollow-core anti-resonant active optical fiber preform.

[0013] Preferably, the average particle size of the nanosilica in step (1) is 45-55 nm.

[0014] Preferably, the photosensitive resin raw material in step (1) comprises a resin monomer, a solvent, a crosslinking agent, a photosensitizer, and a UV absorber.

[0015] Preferably, the mass ratio of the nanosilica to the photosensitive resin raw material in step (1) is (40-50):100.

[0016] Preferably, the light intensity of the DLP photocuring 3D printing in step (2) is 6-6.5 mW / cm 2 , the light exposure time is 1-1.5 s per layer, and the layer thickness is 0.04-0.06 mm.

[0017] Preferably, the heat treatment process in step (3) is as follows: first, increasing the temperature from room temperature to 60-80℃ at a rate of 0.13-0.16℃ / min and maintaining the temperature for 3-5 h, then increasing the temperature to 140-160℃ at a rate of 0.08-0.12℃ / min and maintaining the temperature for 3-5 h, then increasing the temperature to 320-380℃ at a rate of 0.4-0.6℃ / min and maintaining the temperature for 3-5 h, and finally increasing the temperature to 580-620℃ at a rate of 0.4-0.6℃ / min and maintaining the temperature for 1-3 h.

[0018] Preferably, the concentration of the rare earth ions in the solution of the rare earth source in step (4) is 0.001-0.002 mol / L.

[0019] Preferably, the immersion time in step (4) is 3-5 min.

[0020] Preferably, first, increasing the temperature to 750-850℃ at a rate of 2-4℃ / min and maintaining the temperature for 1-2 h, and then increasing the temperature to 1150-1250℃ at a rate of 0.5-1.5℃ / min and maintaining the temperature for 1.5-2.5 h.

[0021] The application provides a preparation method of a full-doped hollow anti-resonant active optical fiber preform, comprising the following steps: (1) mixing nano-silicon dioxide and photosensitive resin raw materials to obtain a printing base material; (2) performing DLP photocuring 3D printing on the printing base material obtained in the step (1) to obtain a green body; (3) performing heat treatment on the green body obtained in the step (2) to obtain a preform precursor; (4) performing immersion doping on the preform precursor obtained in the step (3) in a rare earth source and / or bismuth source solution to obtain a doped preform precursor; and (5) performing sintering on the doped preform precursor obtained in the step (4) to obtain a full-doped hollow anti-resonant active optical fiber preform. The printing base material is obtained by mixing nano-silicon dioxide and photosensitive resin raw materials, and then DLP photocuring 3D printing is performed, the method has extremely high precision, can meet the design requirements of the complex structure of the optical fiber preform, is uniform in thickness, is simple, the organic monomer is removed through heat treatment, then the rare earth source and / or bismuth source solution is immersed for doping, the doping method is simple and uniform, and finally sintering is performed to densify the silicon dioxide, so that the full-doped hollow anti-resonant active optical fiber preform is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A structure schematic diagram of the full-doped hollow anti-resonant active optical fiber preform prepared for the embodiment 1 of the application is shown in the figure.

[0023] Figure 2 A macrograph of the full-doped hollow anti-resonant active optical fiber preform prepared for the embodiment 1 of the application is shown in the figure. DETAILED DESCRIPTION

[0024] The application provides a preparation method of a full-doped hollow anti-resonant active optical fiber preform, comprising the following steps:

[0025] (1) mixing nano-silicon dioxide and photosensitive resin raw materials to obtain a printing base material;

[0026] (2) performing DLP photocuring 3D printing on the printing base material obtained in the step (1) to obtain a green body;

[0027] (3) performing heat treatment on the green body obtained in the step (2) to obtain a preform precursor;

[0028] (4) performing immersion doping on the preform precursor obtained in the step (3) in a rare earth source and / or bismuth source solution to obtain a doped preform precursor;

[0029] (5) performing sintering on the doped preform precursor obtained in the step (4) to obtain a full-doped hollow anti-resonant active optical fiber preform.

[0030] The source of each raw material is not particularly limited in the present application unless otherwise specified, and commercially available products well known to those skilled in the art can be used.

[0031] The present application mixes nanosilica and photosensitive resin raw materials to obtain a printing substrate.

[0032] In the present application, the nanosilica is preferably hydrophilic fumed silica.

[0033] In the present application, the average particle size of the nanosilica is preferably 45-55 nm, more preferably 50 nm.

[0034] In the present application, the photosensitive resin raw material preferably includes resin monomer, solvent, crosslinking agent, photosensitizer, and ultraviolet absorber. In the present application, the resin monomer preferably includes 2-hydroxyethyl methacrylate (HEMA); the solvent preferably includes 2-phenoxyethanol (POE); the crosslinking agent preferably includes tetra(ethylene glycol) dipropylene glycol acrylate (TEGDA); the photosensitizer preferably includes (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (DPO); and the ultraviolet absorber preferably includes hydroquinone (Hyd). In the present application, the volume ratio of the resin monomer, solvent, and crosslinking agent is preferably 60:30:10, the mass of the photosensitizer is preferably 0.2% of the total mass of the nanosilica, resin monomer, solvent, and crosslinking agent, and the mass of the ultraviolet absorber is preferably 0.1% of the total mass of the nanosilica, resin monomer, solvent, and crosslinking agent, denoted as (60HEMA-30POE-10TEGDA, vol%) + (0.2DPO-0.1Hyd, wt%).

[0035] In the present application, the mass ratio of the nanosilica and photosensitive resin raw material is preferably (40-50):100, more preferably 45:100.

[0036] In the present application, the nanosilica is used as the substrate of an optical fiber preform rod, is first mixed with photosensitive resin raw material, and then subjected to DLP photocuring 3D printing. The photosensitive resin raw material undergoes a curing reaction during DLP photocuring 3D printing, can form a variety of green bodies with complex structures, and the method is simple and the thickness is uniform.

[0037] By limiting the particle size of the nanosilica, the composition of the photosensitive resin raw material, and the amount of each of the two parameters within the above ranges, the present application can have a suitable silica content for subsequent formation of an optical fiber preform rod and a high density after sintering, and also has a suitable photosensitive resin content to facilitate the performance of DLP photocuring 3D printing.

[0038] After obtaining the printing substrate, the present application performs DLP photocuring 3D printing on the printing substrate to obtain a green body.

[0039] In the present application, the light intensity of the DLP light-curing 3D printing is preferably 6-6.5 mW / cm 2 , more preferably 6.2 mW / cm 2 ; the light exposure time is preferably 1-1.5 s per layer, more preferably 1.2 s per layer; and the layer thickness is preferably 0.04-0.06 mm, more preferably 0.05 mm. By limiting the parameters of the DLP light-curing 3D printing within the above ranges, the printing process can proceed smoothly, and the thickness is more uniform.

[0040] The present application does not have special limitations on the structure of the blank, and the optical fiber preform structure known to those skilled in the art can be used.

[0041] After obtaining the blank, the present application performs heat treatment on the blank to obtain a preform precursor.

[0042] In the present application, the heat treatment process is preferably: first, from room temperature, at a heating rate of 0.13-0.16 ℃ / min, to 60-80 ℃ and holding for 3-5 h, then at a heating rate of 0.08-0.12 ℃ / min, to 140-160 ℃ and holding for 3-5 h, then at a heating rate of 0.4-0.6 ℃ / min, to 320-380 ℃ and holding for 3-5 h, and finally at a heating rate of 0.4-0.6 ℃ / min, to 580-620 ℃ and holding for 1-3 h; more preferably, first, from room temperature, at a heating rate of 0.15 ℃ / min, to 70 ℃ and holding for 3-5 h, then at a heating rate of 0.1 ℃ / min, to 150 ℃ and holding for 4 h, then at a heating rate of 0.5 ℃ / min, to 350 ℃ and holding for 4 h, and finally at a heating rate of 0.5 ℃ / min, to 600 ℃ and holding for 2 h. In the present application, the heat treatment is used to remove the organic monomer. By segmenting the heat treatment and controlling the temperature and time of each stage within the above ranges, the organic monomer can be fully removed without affecting the structure of the blank.

[0043] After the heat treatment is completed, the present application preferably cools the product of the heat treatment to obtain a preform precursor.

[0044] The present application does not have special limitations on the operation of the cooling, and the cooling technical solution known to those skilled in the art can be used.

[0045] After obtaining the preform precursor, the present application impregnates and dopes the preform precursor in a rare earth source and / or bismuth source solution to obtain a doped preform precursor.

[0046] In the present application, the rare earth source preferably comprises a rare earth chloride; and the bismuth source preferably comprises bismuth chloride. In the present application, the rare earth element in the rare earth source solution preferably comprises one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium.

[0047] In the present application, the concentration of the rare earth ions and bismuth ions in the rare earth source solution and / or bismuth source solution is preferably independently 0.001-0.002 mol / L, and more preferably 0.0015 mol / L. The present application limits the concentration of the rare earth source solution and / or bismuth source solution to the above range, which can make the rare earth source and / or bismuth source sufficiently dissolved and the subsequent doping more uniform.

[0048] In the present application, the solvent in the rare earth source solution and / or bismuth source solution is preferably ethanol.

[0049] The present application preferably first drops and coats part of the rare earth source solution and / or bismuth source solution on the surface of the preform precursor to perform preliminary doping, and then immerses the preform precursor in the rare earth source solution and / or bismuth source solution to perform deep doping, thereby obtaining a doped preform precursor.

[0050] The present application does not have special limitations on the amount of the rare earth source solution and / or bismuth source solution used in the preliminary doping, and the preform precursor can be uniformly coated. In the present application, the preliminary doping is to prevent the preform precursor from exploding.

[0051] In the present application, the time for deep doping is preferably 3-5 min. The present application limits the time for deep doping to the above range, which can achieve full doping.

[0052] After the deep doping is completed, the present application preferably dries the product of the deep doping, thereby obtaining a doped preform precursor.

[0053] The present application does not have special limitations on the drying operation, and any drying technical solution known to those skilled in the art can be used.

[0054] After obtaining the doped preform precursor, the present application sinter the doped preform precursor, thereby obtaining a full-doped hollow-core anti-harmonic active optical fiber preform.

[0055] In the present application, the sintering process is preferably: first, heating to 750-850℃ at a heating rate of 2-4℃ / min for 1-2h, and then heating to 1150-1250℃ at a heating rate of 0.5-1.5℃ / min for 1.5-2.5h, more preferably, first, heating to 800℃ at a heating rate of 3℃ / min for 1.5h, and then heating to 1200℃ at a heating rate of 1℃ / min for 2h. In the present application, the sintering process can densify the preform rod precursor. The present application limits the stages of sintering and the parameters such as temperature and time of each stage within the above range, which can further improve the density of the preform rod.

[0056] After sintering, the present application preferably cools the sintered product to obtain a fully doped hollow core anti-resonant active optical fiber preform.

[0057] The present application does not have special limitations on the cooling operation, and the technical solution of cooling known to those skilled in the art can be used.

[0058] In the embodiments of the present application, the structure of the fully doped hollow core anti-resonant active optical fiber preform is preferably as shown in Figure 1 , which comprises a cladding ring tube 2, an air core 3 formed by the cladding ring tube, and a support element 1 outside the cladding ring tube, wherein O p is the center of the air core, C p is the inscribed point of the cladding ring tube and the support element. In the present application, the number of the cladding ring tube is preferably 6-8, more preferably 7; the inner diameter d p of the cladding ring tube is preferably 3.50-3.70mm; the thickness t p of the cladding ring tube is preferably 0.40-0.50mm; the cladding ring tube is inscribed on the inner surface of the support element at equal intervals. In the present application, the diameter D p of the air core formed by the cladding ring tube is preferably 6.40-7.40mm. In the present application, the outer diameter D of the support element is preferably 18-20mm, and the thickness T p of the support element is preferably 1.50-1.60mm, more preferably 1.55mm.

[0059] The present application first mixes nanosilica and photosensitive resin raw materials to obtain a UV-sensitive monomer, and then performs DLP photocuring 3D printing. This method can meet the design requirements of the complex structure of the optical fiber preform rod, has uniform thickness, and is simple. Then, the organic monomer is removed by heat treatment, and then impregnated with a rare earth and / or bismuth solution for doping. The doping method is simple and uniform. Finally, sintering densifies the silica, thereby obtaining a fully doped hollow core anti-resonant active optical fiber preform rod.

[0060] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the protection scope of the present application.

[0061] Embodiment 1

[0062] (1) Hydrophilic fumed silica with an average particle size of 50 nm is mixed with a photosensitive resin, wherein the photosensitive resin is composed of 2-hydroxyethyl methacrylate (HEMA), 2-phenoxyethanol (POE), tetra(ethylene glycol) dimethacrylate (TEGDA), (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (DPO) and hydroquinone (Hyd) according to the component ratio of (60 HEMA-30 POE-10 TEGDA, vol%) + (0.2 DPO-0.1 Hyd, wt%), and the mass ratio of silica and photosensitive resin is 45:100, to obtain a printing substrate;

[0063] (2) The printing substrate is used for DLP 3D printing of a blank, wherein the light intensity of 3D printing is 6.2 mW / cm 2 , the light exposure time is 1.2 s per layer, and the layer thickness is 0.05 mm;

[0064] (3) The printed blank is placed in a high-temperature furnace for heat treatment, and the heat treatment process is as follows: first, the furnace is raised from room temperature to 70℃ at a heating rate of 0.15℃ / min and kept for 4 h, then raised to 150℃ at a heating rate of 0.1℃ / min and kept for 4 h, then raised to 350℃ at a heating rate of 0.5℃ / min and kept for 4 h, and finally raised to 600℃ at a heating rate of 0.5℃ / min and kept for 2 h, to obtain a preform rod precursor;

[0065] (4) An ethanol solution containing erbium chloride (concentration of 0.0015 mol / L) is dropped on the preform rod precursor with a rubber head dropper for preliminary doping, and then the whole is immersed in the ethanol solution containing erbium chloride for 4 min to realize full doping;

[0066] (5) The doped structure is sintered in a high-temperature furnace, and the sintering process is as follows: the furnace is raised to 800℃ at a heating rate of 3℃ / min and kept for 1.5 h, then raised to 1200℃ at a heating rate of 1℃ / min and kept for 2 h, and then lowered to room temperature, to obtain a full-doped hollow-core anti-resonant active optical fiber preform; wherein the full-doped hollow-core anti-resonant active optical fiber preform is composed of a cladding tube 2 and an air core 3 surrounded by the cladding tube, and a support element 1 outside the cladding tube, wherein O p is the center of the air core, Cp The point of tangency between the cladding annulus and the supporting element is defined as 7 cladding annulus tubes; the inner diameter d of the cladding annulus tube is defined as... p The thickness is 3.60 mm; the thickness t of the cladding annulus is... p The diameter is 0.46 mm; the cladding annulus is tangent to the inner surface of the support element at equal intervals, and the diameter D of the air core formed by the cladding annulus is... p The outer diameter D of the support element is 19.14 mm, and the thickness T of the support element is 7.29 mm. p It is 1.55mm.

[0067] Macroscopic image of the fully doped hollow antiresonant optical fiber preform prepared in Example 1 is shown below. Figure 2 As shown. From Figure 2 As can be seen from the above, the thickness of the support layer and the cladding ring in the fully doped hollow anti-resonant optical fiber preform prepared by this invention is relatively uniform.

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1.A method for preparing a fully-doped hollow anti-resonant active optical fiber preform, comprising the following steps: (1) mixing nanosilica and a photosensitive resin raw material to obtain a printing base material; (2) performing DLP photocuring 3D printing on the printing base material obtained in step (1) to obtain a green body; (3) performing heat treatment on the green body obtained in step (2) to obtain a preform precursor; (4) performing immersion doping of the preform precursor obtained in step (3) in a rare earth source and / or bismuth source solution to obtain a doped preform precursor; (5) performing sintering on the doped preform precursor obtained in step (4) to obtain a fully-doped hollow anti-resonant active optical fiber preform; The average particle size of the nanometer silicon dioxide in the step (1) is 45-55 nm; the photosensitive resin raw material in the step (1) comprises a resin monomer, a solvent, a crosslinking agent, a photosensitizer and an ultraviolet absorber; the resin monomer is 2-hydroxyethyl methacrylate; the solvent is 2-phenoxyethanol; the crosslinking agent is tetra(ethylene glycol) dipropylene glycol acrylate; the photosensitizer is (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide; the ultraviolet absorber is hydroquinone; the mass ratio of the nanometer silicon dioxide and the photosensitive resin raw material in the step (1) is (40-50): 100; the light intensity of the DLP light-cured 3D printing in the step (2) is 6-6.5 mW / cm 2 , the light exposure time is 1-1.5 s per layer, and the layer thickness is 0.04-0.06 mm; the heat treatment process in the step (3) is: first, increase the temperature from room temperature to 60-80℃ at a rate of 0.13-0.16℃ / min and keep it for 3-5 h, then increase the temperature to 140-160℃ at a rate of 0.08-0.12℃ / min and keep it for 3-5 h, then increase the temperature to 320-380℃ at a rate of 0.4-0.6℃ / min and keep it for 3-5 h, and finally increase the temperature to 580-620℃ at a rate of 0.4-0.6℃ / min and keep it for 1-3 h; the concentration of rare earth ions in the rare earth source solution in the step (4) is 0.001-0.002 mol / L; the time of immersion in the step (4) is 3-5 min; the step (4) is: drop-coat part of the rare earth source and / or bismuth source solution on the surface of the preform precursor for preliminary doping, and then immerse it in the rare earth source and / or bismuth source solution for deep doping to obtain a doped preform precursor. the sintering process in step (5) is: first, heating at a heating rate of 2-4 ℃ / min to 750-850 ℃ for 1-2 h, and then heating at a heating rate of 0.5-1.5 ℃ / min to 1150-1250 ℃ for 1.5-2.5 h.

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