Plasma-based VAD preform preparation device and active optical fiber preform preparation method

Abstract

The invention provides a plasma-based VAD preform preparation device and an active optical fiber preform preparation method. The device comprises a front-end feeding system and a plasma torch radiator, the plasma torch radiator is used for providing a plasma torch; the front-end feeding system is used for providing mixed atomized spray; the mixed atomized spray is located at a plasma torch, and deposition substances are generated through high-temperature reaction; the rotary moving mechanism is arranged above the front-end feeding system and controls and adjusts the distance between the base rod and the plasma torch and the distance between the base rod and an outlet of the front-end feeding system, and the deposition matter can be deposited on the surface of the base rod. According to the plasma-based VAD preform preparation device and the corresponding preparation method, the problems of glass phase splitting, crystallization, rare earth ion clustering and the like which are frequently encountered in a heat balance state with a high rare earth doping level can be inhibited, and various doping agents can be deposited in a single treatment step; and the active optical fiber can reach the highest ideal state in the aspects of rare earth doping concentration, core diameter and uniform distribution of doped elements.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber preform processing, and in particular to a plasma-based VAD preform preparation device and an active optical fiber preform preparation method. Background Art

[0002] Optical fiber preform manufacturing technologies primarily include modified chemical vapor deposition (MCVD), plasma chemical vapor deposition (PCVD), outside chemical deposition (OVD), and axial vapor deposition (VAD). Preforms produced using the axial vapor deposition method are defined as VAD (Vapour-Phase Axial Deposition) preforms.

[0003] For laser fibers with excellent beam quality transmission performance, increasing their power to higher levels is limited by nonlinear effects such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS). To maintain excellent beam transmission performance, single-mode fibers typically use small fiber core diameters with low numerical aperture (NA; low refractive index). This approach requires higher dopant concentrations while ensuring a highly uniform dopant distribution. However, this process also raises a series of technical challenges. Specifically, due to the rare earth ion clustering effect in highly doped fibers, glass crystallization and phase separation are easily triggered. In addition, the low solubility of rare earth elements themselves makes it difficult to ensure doping uniformity. Currently, established high-temperature preform manufacturing techniques typically involve a two-step process, such as using enhanced chemical vapor deposition (ECVD) to create an inner deposition tube, followed by soot powder sintering (Repusil) to form the desired core rod. Due to the diffusion-controlled process and two-phase flow balance, as well as the limitations of conventional glass melting in terms of the amount and composition of dopants in silica, doping the various dopants required to alter the refractive index of silica glass into the silica matrix typically involves multiple steps. Each step imposes additional heat input on the doped sample, thus sometimes affecting the overall homogeneity of the core material in a counteracting manner.

[0004] Based on this, the present invention proposes a new plasma-based VAD preform preparation device and an active optical fiber preform preparation method. Summary of the Invention

[0005] Based on the above description, the present invention provides a plasma-based VAD preform preparation device and an active optical fiber preform preparation method to improve the limitations and shortcomings of the conventional microwave plasma vapor phase axial deposition VAD process method in terms of the doping distribution, doping level and core rod diameter of optically active substances that can be incorporated into the preform.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: In a first aspect, the present invention provides a plasma-based VAD preform preparation device, comprising: a front-end feeding system and a plasma torch emitter; The plasma torch emitter is used to provide a plasma torch; The front-end feeding system is used to provide mixed atomized spray; The mixed atomized spray is located at the plasma torch and generates deposition material through high temperature reaction. The distance between the base rod and the plasma torch and the outlet of the front-end feeding system is controlled and adjusted so that the deposition material can be deposited on the surface of the base rod.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the front-end feeding system includes: a liquid atomizer, an atomizing nozzle, a liquid pipe and a gas pipe; The liquid atomizer is connected to the liquid pipe, and the liquid atomizer is used to atomize the liquid in the liquid pipe; The liquid pipe is sleeved outside the gas pipe, the wall of the gas pipe is provided with a through hole, and the liquid pipe and the gas pipe are connected through the through hole; The atomizing nozzle is arranged at the outlet of the gas pipe; when liquid and gas are injected into the liquid pipe and the gas pipe at the same time, the liquid is atomized by the liquid atomizer and then accelerated by the atomizing nozzle to produce the mixed atomized spray.

[0009] Furthermore, the front-end feeding system includes a liquid supply source and a gas supply source; The liquid supply source is connected to the liquid pipe and is used to provide liquid to the liquid pipe; The gas supply source is connected to the gas pipe and is used to provide gas to the gas pipe.

[0010] Furthermore, the plasma torch emitter includes a normal pressure microwave plasma system; The atmospheric pressure microwave plasma system excites oxygen into plasma to form a plasma torch.

[0011] Furthermore, the plasma-based VAD preform preparation device further includes a rotating movement mechanism; The rotary moving mechanism is arranged above the front-end feeding system, and is used for clamping the base rod to be deposited and driving the base rod to rotate.

[0012] Furthermore, the plasma-based VAD preform preparation device further includes an infrared temperature measurement camera; The infrared temperature measuring camera is arranged toward the base rod and is used to measure the surface temperature of the base rod.

[0013] Furthermore, the plasma-based VAD preform preparation device further includes a spectrometer; The spectrometer is disposed toward the plasma torch provided by the plasma torch emitter, and is used to analyze an excitation diffusion process occurring in the plasma torch.

[0014] Furthermore, the plasma-based VAD preform preparation device further includes a detection camera; The detection camera is arranged toward the base rod and is used to detect the diameter and length of the base rod to determine the deposition length and deposition efficiency.

[0015] In a second aspect, the present invention provides a method for preparing a VAD preform using the plasma-based VAD preform preparation apparatus as described in the first aspect, comprising the following steps: S1: using a plasma torch emitter to excite oxygen into plasma through a normal pressure microwave plasma system to generate a plasma torch; S2: The mixed atomized material provided by the front-end feeding system is sprayed to the ion torch, and the deposited material is generated through high-temperature reaction and is sprayed with the air flow and attached to the base rod; S3: Simultaneously with step S2, the distance between the plasma torch and the outlet of the front-end feeding system is controlled during the rotation of the base rod, so that the deposition material is uniformly deposited on the surface of the base rod; thus, a VAD preform is obtained.

[0016] On the basis of the above technical solution, the present invention can also be improved as follows.

[0017] Furthermore, in step S2, the front-end feeding system provides mixed atomization, specifically including: Liquid and gas are injected into the liquid pipe and the gas pipe at the same time, and the liquid atomizer atomizes the liquid, which is accelerated through the nozzle to produce the high-speed and uniform mixed atomized spray.

[0018] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The plasma-based VAD preform preparation device provided by the present invention includes a front-end feeding system and a plasma torch emitter. The plasma torch emitter is used to provide a plasma torch. The front-end feeding system is used to provide a mixed atomized spray. The mixed atomized spray is located at the plasma torch and generates a deposition material through a high-temperature reaction. The distance between the plasma torch and the outlet of the front-end feeding system is controlled and adjusted to ensure that the deposition material is deposited on the surface of the base rod. Compared with existing methods, this solution has the following advantages: The front-end feeding system can provide a highly uniform liquid spray; the plasma torch emitter provides a combination of non-equilibrium thermodynamic and kinetic control processes, in which the diffusion limit is broken. Therefore, effects such as phase separation and crystallization effects that often occur in the thermal equilibrium state of the required high rare earth (RE) doping level can be suppressed, improving the limitations and shortcomings of conventional VAD process methods on the doping distribution, doping level and core rod diameter of optically active substances that can be incorporated into the preform rod. At the same time, this device and the corresponding method can deposit multiple dopants in one processing step.

[0019] Therefore, the plasma-based VAD preform preparation device and the corresponding preparation method provided by the present invention can suppress problems such as glass phase separation, crystallization and rare earth ion clustering that are often encountered under the thermal equilibrium state of high rare earth doping levels, and can deposit multiple dopants in a single processing step; it can achieve the highest ideal state of active optical fiber in terms of rare earth doping concentration, core diameter and uniform distribution of doping elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of a plasma-based VAD preform preparation device provided in an embodiment of the present invention; Figure 2 A schematic cross-sectional view of a front-end feeding system according to an embodiment of the present invention; Figure 3 Optical emission spectrum of a microwave power of 1 kW obtained at a distance of (a) x = 5 mm from the nozzle of a pure oxygen plasma with a flow rate of 10 slm provided in an embodiment of the present invention; Figure 4 Optical emission spectrum of a microwave power of 1 kW obtained at a distance of (a) x = 10 mm from the nozzle of a pure oxygen plasma with a flow rate of 10 slm provided in an embodiment of the present invention; Figure 5 Optical emission spectrum of a microwave power of 1 kW obtained at a distance of (a) x = 15 mm from the nozzle of a pure oxygen plasma with a flow rate of 10 slm provided in an embodiment of the present invention; Figure 6 The substrate temperature provided for the embodiments of the present invention is a function of the working distance and the corresponding normalized deposition rate; Figure 7 A sample diagram of plasma deposition provided by an embodiment of the present invention; Figure 8 Backscattered electron images of polished and vitrified plasma treated samples provided by embodiments of the present invention; Figure 9 Electron probe microanalysis line scan provided by an embodiment of the present invention; Figure 10 A dopant distribution histogram provided by an embodiment of the present invention; Figure 11 Raman scattering spectrum of the plasma deposition sample provided in an embodiment of the present invention; Figure 12 Radial Al2O3 and Yb2O3 plasma distributions provided by the embodiments of the present invention - and electron probe microanalysis line scans of sintered melt shrinkage samples with different target concentrations; Figure 13 The radial Al2O3 and Yb2O3 plasma distributions provided by the embodiments of the present invention - as well as histograms of dopant distributions of sintered melt-shrinkage samples with different target concentrations; Figure 14 A graph of refractive index variation calculated from the radius of the plasma-sample and sintering and melting shrinkage treated samples provided by an embodiment of the present invention; Figure 15 A histogram of the refractive index distribution of the plasma-sample and the measured sintering and melting shrinkage treated sample provided by an embodiment of the present invention; Figure 16 The refractive index profile of the 30 / 400 double-clad Yb-doped optical fiber drawn using the novel VAD preform preparation technology and the traditional MCVD+CDS process preparation technology provided by the present invention; Figure 17 Absorption spectra of 30 / 400 double-clad optical fibers drawn using the novel VAD preform preparation technology and the traditional MCVD+CDS process preparation technology provided by the present invention; Figure 18 The optical-to-optical conversion efficiency of the 30 / 400 double-clad optical fiber drawn using the novel VAD preform preparation technology and the traditional MCVD+CDS process preparation technology provided by the present invention; In the accompanying drawings, the components represented by the reference numerals are as follows: 1. Front-end feeding system; 11. Liquid atomizer; 12. Atomizing nozzle; 13. Liquid pipe; 14. Gas pipe; 141. Through hole; 15. Liquid supply source; 16. Gas supply source; 2. Plasma torch emitter; 21. Plasma torch; 3. Rotating movement mechanism; 4. Infrared temperature measurement camera; 5. OSE spectrometer; 6. CCD detection camera; 7. Base stick. DETAILED DESCRIPTION

[0021] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "provided with" and "connected" should be understood in a broad sense. For example, "connected" can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection, an indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0022] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0023] The following is combined with Figures 1 to 15 The embodiments of the present invention are further described in detail with reference to the following examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0024] like Figure 1 As shown, an embodiment of the present invention provides a plasma-based VAD preform preparation device, comprising: a front-end feeding system 1 and a plasma torch emitter 2; The plasma torch emitter 2 is used to provide a plasma torch 21 .

[0025] The plasma torch emitter 2 includes a normal-pressure microwave plasma system, which excites oxygen into plasma to form a plasma torch 21 .

[0026] The front-end feeding system 1 is used to provide mixed atomized spray; the mixed atomized spray is located at the plasma torch 21 and generates deposition material through high-temperature reaction.

[0027] It also includes a rotating and moving mechanism 3; the rotating and moving mechanism 3 is arranged above the front-end feeding system 1, and the rotating and moving mechanism 3 is used to clamp the base rod 7 to be deposited, drive the base rod 7 to rotate, and control and adjust the distance between the base rod 7 and the plasma torch 21 and the outlet of the front-end feeding system 1 so that the deposition material is deposited on the surface of the base rod 7.

[0028] Specifically, if Figure 2 As shown, the front-end feeding system 1 includes: a liquid atomizer 11, an atomizing nozzle 12, a liquid pipe 13 and a gas pipe 14.

[0029] The liquid atomizer 11 is connected to the liquid pipe 13 and is used to atomize the liquid in the liquid pipe 13 .

[0030] The liquid pipe 13 is sleeved on the outside of the gas pipe 14 . A through hole 141 is provided on the wall of the gas pipe 14 . The liquid pipe 13 and the gas pipe 14 are communicated with each other through the through hole 141 .

[0031] The atomizing nozzle 12 is provided at the outlet of the gas pipe 14; when liquid and gas are simultaneously injected into the liquid pipe 13 and the gas pipe 14, the liquid is atomized by the liquid atomizer 11 and then accelerated by the atomizing nozzle 12 to produce a mixed atomized spray.

[0032] In an optional embodiment, preferably, the atomizing nozzle 12 is a Laval nozzle.

[0033] Furthermore, the front-end feeding system 1 includes a liquid supply source 15 and a gas supply source 16 .

[0034] The liquid supply source 15 is connected to the liquid pipe 13 for supplying liquid to the liquid pipe 13 .

[0035] The gas supply source 16 is connected to the gas pipe 14 for providing gas to the gas pipe 14 .

[0036] On the basis of the above embodiment, the plasma-based VAD preform rod preparation device further includes an infrared temperature measuring camera 4 ; the infrared temperature measuring camera 4 is arranged toward the base rod 7 and is used to measure the surface temperature of the base rod 7 .

[0037] On the basis of the above embodiment, the plasma-based VAD preform rod preparation device further includes a spectrometer 5, preferably an OSE spectrometer; the spectrometer 5 is set towards the plasma torch provided by the plasma torch emitter 2, and is used to analyze the excitation diffusion process occurring in the plasma torch 21.

[0038] On the basis of the above embodiment, the plasma-based VAD preform rod preparation device further includes a detection camera 6, preferably a CCD detection camera; the detection camera 6 is set toward the base rod 7, and is used to detect the diameter and length of the base rod 7 to determine the deposition length and deposition efficiency.

[0039] It should be noted that parameters such as the surface temperature of the base rod 7 , the deposition rate, and the distance between the base rod 7 and the atomizing nozzle 12 can be set according to actual needs and are not specifically limited here.

[0040] In order to better explain the plasma-based VAD preform preparation device provided by an embodiment of the present invention, a preparation method of an active optical fiber preform is provided below.

[0041] The specific steps are as follows: Step S1: using a plasma torch emitter to excite oxygen into plasma through a 2.45 GHz atmospheric pressure microwave plasma system to generate a plasma torch.

[0042] Step S2: The mixed atomized material provided by the front-end feeding system is sprayed to the plasma torch, where it undergoes a high-temperature reaction to generate a deposition material, which is then sprayed with the airflow and attached to the base rod.

[0043] Among them, the front-end feeding system provides mixed atomization specifically including: liquid and gas are injected into the liquid pipe and gas pipe at the same time, the liquid atomizer atomizes the liquid, and accelerates the production of high-speed and uniform mixed atomized spray through the nozzle.

[0044] Step S3: Simultaneously with step S2, the rotary moving mechanism drives the base rod to rotate, and during the rotation, the distance between the plasma torch and the outlet of the front-end feeding system is controlled so that the deposition material is evenly deposited on the surface of the base rod; thus, an active optical fiber preform is obtained.

[0045] Furthermore, in order to better explain the beneficial effects of the plasma-based VAD preform preparation apparatus and the corresponding preparation method provided in the embodiments of the present invention, a series of verifications of relevant parameter limits are provided as examples: Figure 3 Shown are the optical emission spectra of pure oxygen plasma with a flow rate of 10 slm and a microwave power of 1 kW obtained at (a) a distance of x = 5 mm (from the atomizing nozzle); Figure 4 Shown are the optical emission spectra of pure oxygen plasma with a flow rate of 10 slm and a microwave power of 1 kW obtained at (b) a distance of x = 10 mm (base rod to atomizing nozzle); Figure 5 Shown is the optical emission spectrum of a microwave power of 1 kW obtained at a distance of (c) x = 15 mm (base rod to atomizing nozzle) for pure oxygen plasma with a flow rate of 10 slm; from the comparison of these three figures, it can be found that within a certain range, the carbon atom content decreases with the increase of the distance between the axis of the discharge tube and the axis of the atomizing nozzle. Therefore, the distance x can be set to about 15 mm for solidification.

[0046] Figure 6 Shown is the substrate temperature as a function of working distance and the corresponding fitted normalized deposition rate. According to the online infrared camera measurement, for a working distance of 50 mm, the maximum substrate temperature reached during deposition is about 1100°C, and the deposition rate is measured to be the highest at this position.

[0047] Figure 7Shown are images of the sample as deposited and after vitrification. Plasma deposition of Al2O3- and Yb2O3-doped SiO2 was performed with a target concentration of 3 mol % Al2O3 and 0.3 mol % Yb2O3 using a microwave power of 3 kW, a deposition time of 30 minutes, a precursor feed jet flow rate of 2 g / min, a working distance of 50 mm, an oxygen flow rate of 12 slm, and a maximum surface temperature of 1100°C. Because direct vitrification during deposition can only be achieved at deposition temperatures above 1750°C, the deposited sample did not fully vitrify during the process. However, it is anticipated that direct vitrification could be achieved with increased power.

[0048] Figure 8 Shown above Figure 7 Backscattered electron images of the polished sample after vitrification and the sample treated with vitrified plasma show no visible phase separation and crystallization at the micrometer scale.

[0049] Figure 9 The radial sample distribution of Al2O3 and Yb2O3 concentrations obtained from EPMA line scans is shown. For better comparison, the scale factor in the figure is kept the same for both dopants. In order to quantitatively describe the dopant uniformity of Al2O3 and Yb2O3, the data are converted into histograms (e.g. Figure 10 The data directly depicts the mean (µ) and standard deviation (σ) indicators related to the molar concentration; the data in the two figures show that the doping homogeneity of Al2O3 and Yb2O3 is good.

[0050] Figure 11 Shown are Raman scattering spectra of plasma deposited samples with target concentrations of 3 mol % Al2O3 and 0.3 mol % Yb2O3. The Raman scattering spectra obtained from line scans are collected and show the corresponding maximum fluctuations in intensity and frequency, which are determined by Figure 11 As indicated by the medium green bar, only minor fluctuations are observed, indicating a very homogeneous structure, which is in good agreement with the EPMA measurement observations.

[0051] Figure 12 Shown are radial Al2O3 and Yb2O3 plasma distributions - and electron probe microanalysis line scans of sintered melt shrinkage samples with different target concentrations; Figure 13Shown are histograms of radial Al2O3 and Yb2O3 plasma distributions and dopant distributions for sintered melt samples at different target concentrations. For proper comparison, representative plasma-treated samples were compared with samples processed by a sintered melt process with a stoichiometric ratio of Al2O3:Yb2O3 close to 10:1. Electron probe microanalysis line scans of radial Al2O3 and Yb2O3 plasma distributions and dopant distributions for sintered melt samples at different target concentrations are provided, as well as histograms of radial Al2O3 and Yb2O3 plasma distributions and dopant distributions for sintered melt samples at different target concentrations.

[0052] in, Figure 13 Figure 3 shows the dopant distribution of the sintered melt-treated and plasma-treated samples, i.e., the dopant distribution of Al2O3 and Yb2O3 obtained by EPMA line scan. For better comparison, the scaling coefficients in the graph remain unchanged for both dopants. The target concentration of Al2O3 for the plasma-treated and sintered melt-treated samples is shown again as 3 mol%, while the target concentration of Yb2O3 for the sintered melt-treated sample is 0.25 mol%, and the target concentration of Yb2O3 for the plasma-treated sample is 3 mol%. The Al2O3 line scan results for the sintered melt-treated sample are compared with the Figure 12 Compared with the Al2O3 line scan results of the plasma treated sample in , the maximum molar change rate Amax of the plasma treated sample is about one quarter of that of the sintered melt shrinkage sample, which indicates that its uniformity is better.

[0053] from Figure 12 and Figure 13 It can be seen that the uniformity of plasma-treated samples is higher than that of sintered and melt-shrunk samples.

[0054] In order to achieve low refractive index profile variation (ignoring any effects caused by fiber drawing), a high degree of doping uniformity is required. The theoretical refractive index profile is derived by using the EPMA radial concentration profiles of Al2O3 and Yb2O3, the mole fraction c [mol%] and the refractive index increment, as shown in the following formula:

[0055] Figure 14 The sum of the fluctuations in doping concentration is shown as the fluctuation in the refractive index distribution. The maximum fluctuation Δn calculated for the plasma-treated sample is about three times lower than that for the sintered and melt-shrunk sample, indicating excellent refractive index uniformity.

[0056] Figure 15 The mean μΔn and standard deviation σ Δ n of the refractive index distribution are shown. From the standard deviation σ Δ n, it can be concluded that the refractive index fluctuation of the plasma-treated sample is about 3.5 times lower than that of the sintering and melting-processed sample, indicating its excellent refractive index uniformity.

[0057] Figure 16 The refractive index profiles of 30 / 400 double-clad Yb-doped optical fibers produced using the novel VAD preform preparation technology and the traditional MCVD+CDS process are shown. It can be seen that compared to the traditional MCVD preparation technology (black curve), the novel VAD preform preparation technology (red curve) achieves a more uniform refractive index distribution in the fiber core, with a smaller fluctuation range and a smoother refractive index profile. This indicates that optical fibers produced using the novel VAD preform preparation technology will have a higher yield.

[0058] Figure 17 The absorption spectra of 30 / 400 double-clad optical fibers produced using the novel VAD preform preparation technology and the traditional MCVD+CDS process are shown. As can be seen, the absorption peaks at 915 nm and 976 nm for the novel VAD preform preparation technology (red curve) are significantly higher than those for the traditional MCVD preparation technology (black curve). This demonstrates that the novel VAD preform preparation technology enables better control of the fiber's dopant distribution, thereby improving the fiber's absorption performance at specific wavelengths.

[0059] Figure 18 The optical-to-optical conversion efficiency of 30 / 400 double-clad optical fibers produced using the novel VAD preform preparation technology and the traditional MCVD+CDS process is shown. The figure shows that the optical-to-optical conversion efficiency achieved with the novel VAD preform preparation technology (blue solid line) reaches 80%, approximately 10% higher than that achieved with the traditional MCVD preparation technology (red solid line).

[0060] In summary, the present invention can obtain a VAD preform with high concentration (absorbed light conversion efficiency (80%)), good consistency (good refractive index profile and yield), and large core diameter (more optical fibers can be drawn).

[0061] The above comparative tests have proved that this innovative PVAD technology based on atmospheric pressure microwave plasma can be used to deposit and manufacture highly uniform rare earth doped preform materials.

[0062] Compared with the existing preform rod manufacturing technology (MCVD / VAD+sintering and melting), the method based on atmospheric pressure plasma torch plus front-end atomization feeding provided by this embodiment can significantly improve the maximum doping level of rare earth elements and the uniformity of the overall dopant distribution, and can achieve one-time sintering and vitrification molding, which has very broad application prospects and technical value.

[0063] In summary, compared with the prior art, this embodiment can achieve the following technical effects: The plasma-based VAD preform preparation device and corresponding preparation method provided in the embodiments of the present invention can suppress phase separation and crystallization, which are often encountered in the thermal equilibrium state of high rare earth (RE) doping levels, and can deposit multiple dopants in a single processing step; compared with existing preform manufacturing technologies, this method can achieve the highest ideal state of active optical fiber in terms of rare earth doping concentration, core diameter and uniform distribution of doping elements.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A plasma-based VAD preform preparation device, characterized in that: include: Front-end feeding system and plasma torch emitter; The plasma torch emitter is used to provide a plasma torch; The front-end feeding system is used to provide mixed atomized spray; The mixed atomized spray is located at the plasma torch and generates deposition material through high temperature reaction. The distance between the base rod and the plasma torch and the outlet of the front-end feeding system is controlled and adjusted so that the deposition material can be deposited on the surface of the base rod.

2. The plasma-based VAD preform preparation device according to claim 1, characterized in that: The front-end feeding system includes: a liquid atomizer, an atomizing nozzle, a liquid pipe and a gas pipe; The liquid atomizer is connected to the liquid pipe, and the liquid atomizer is used to atomize the liquid in the liquid pipe; The liquid pipe is sleeved outside the gas pipe, a through hole is provided on the wall of the gas pipe, and the liquid pipe and the gas pipe are connected through the through hole; The atomizing nozzle is arranged at the outlet of the gas pipe; when liquid and gas are injected into the liquid pipe and the gas pipe at the same time, the liquid is atomized by the liquid atomizer and then accelerated by the atomizing nozzle to produce the mixed atomized spray.

3. The plasma-based VAD preform preparation device according to claim 2, characterized in that: The front-end feeding system includes a liquid supply source and a gas supply source; The liquid supply source is connected to the liquid pipe and is used to provide liquid to the liquid pipe; The gas supply source is connected to the gas pipe and is used to provide gas to the gas pipe.

4. The plasma-based VAD preform preparation device according to claim 1, characterized in that: The plasma torch emitter includes a normal pressure microwave plasma system; The atmospheric pressure microwave plasma system excites oxygen into plasma to form a plasma torch.

5. The plasma-based VAD preform preparation device according to claim 1, characterized in that: The plasma-based VAD preform preparation device further includes a rotation and movement mechanism; The rotary movement mechanism is arranged above the front-end feeding system, and is used for clamping the base rod to be deposited and driving the base rod to rotate.

6. The plasma-based VAD preform preparation device according to claim 1, characterized in that: The plasma-based VAD preform preparation device also includes an infrared temperature measurement camera; The infrared temperature measuring camera is arranged toward the base rod and is used to measure the surface temperature of the base rod.

7. The plasma-based VAD preform manufacturing device according to claim 1, characterized in that: The plasma-based VAD preform preparation apparatus further includes a spectrometer; The spectrometer is disposed toward the plasma torch provided by the plasma torch emitter, and is used to analyze an excitation diffusion process occurring in the plasma torch.

8. The plasma-based VAD preform preparation device according to claim 7, characterized in that: The plasma-based VAD preform preparation apparatus further includes a detection camera; The detection camera is arranged toward the base rod and is used to detect the diameter and length of the base rod to determine the deposition length and deposition efficiency.

9. A method for preparing an active optical fiber preform, characterized in that: The steps include: S1: using a plasma torch emitter to excite oxygen into plasma through a normal pressure microwave plasma system to generate a plasma torch; S2: The mixed atomized material provided by the front-end feeding system is sprayed to the ion torch, and the deposited material is generated through high-temperature reaction and is sprayed with the air flow and attached to the base rod; S3: Simultaneously with step S2, the distance between the plasma torch and the outlet of the front-end feeding system is controlled during the rotation of the base rod, so that the deposition material is uniformly deposited on the surface of the base rod; thus, a VAD preform is obtained.

10. The preparation method according to claim 9, characterized in that In step S2, the front-end feeding system provides mixed atomization, specifically including: Liquid and gas are injected into the liquid pipe and the gas pipe at the same time, and the liquid atomizer atomizes the liquid, which is accelerated through the nozzle to produce the high-speed and uniform mixed atomized spray.

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