A method of manufacturing a tapered optical fiber and a tapered optical fiber

Abstract

The application provides a preparation method of a tapered optical fiber and the tapered optical fiber, and relates to the technical field of optical fiber preparation.The preparation method comprises the following steps: preparing a core rod doped with rare earth ions, polishing the core rod, inserting the polished core rod into a sleeve provided with a containing hole to obtain an optical fiber preform, heating a tapered tip of the optical fiber preform, applying a pushing force to a tail part of the core rod when the temperature of the optical fiber preform exceeds a preset temperature value, filling the tapered tip of the core rod into the sleeve after the tapered tip is melted, continuing to heat the tapered tip of the optical fiber preform, keeping the temperature of the optical fiber preform in a preset temperature range, performing fiber drawing, performing vacuumizing on the containing hole of the sleeve, adjusting the inner diameter of a melting area of the tapered tip of the sleeve, and thereby adjusting the core-cladding ratio of the obtained tapered optical fiber at different sections. Thus, by adjusting the negative pressure of the optical fiber preform during vacuumizing and changing the inner diameter of the sleeve, the core-cladding ratio of the tapered optical fiber can be controlled, and the tapered optical fiber required for mass production can be finally obtained.

Description

Technical Field

[0001] This invention relates to the field of optical fiber fabrication technology, and in particular to a method for fabricating tapered optical fibers and the tapered optical fibers themselves. Background Technology

[0002] Tapered optical fibers possess advantages such as high nonlinear effect thresholds and high mode instability thresholds, making them a crucial support for the future development of high-power lasers. Currently, common tapered optical fibers mainly fall into two categories: one type has a constant core-to-cladding ratio (fiber core diameter divided by cladding diameter), characterized by both core and cladding diameters increasing or decreasing simultaneously along the fiber's length; the other type has a variable core-to-cladding ratio, characterized by a constant cladding diameter but a changing core diameter along the fiber's length.

[0003] In the existing technology, the process of preparing optical fibers with varying core-to-cladding ratios first involves processing the core rod into a tapered region. This is done by methods such as heated tapering and mechanical polishing to create the tapered region in the core rod stage. Then, the core rod is inserted into the ferrule and subjected to a melting and shrinking process to obtain an optical fiber preform with a fixed tapered structure in the core. After that, the optical fiber preform is drawn to obtain a tapered optical fiber with a constant cladding diameter but varying core-to-cladding ratio.

[0004] However, in the existing manufacturing process described above, the core rod with the tapered region is fixed inside the optical fiber preform. The taper of the tapered region cannot be adjusted during production, making it difficult to easily adjust the core-to-cladding ratio of the tapered optical fiber. Furthermore, in actual operation, the polishing of the tapered region on the core rod surface requires high precision and is difficult to control, with short processing lengths. This makes it difficult for this preparation method to produce tapered optical fibers with variable core-to-cladding ratios on a large scale and over long periods. Summary of the Invention

[0005] This invention provides a method for preparing tapered optical fiber and a tapered optical fiber, which solves the defect in the prior art that the core-cladding ratio of tapered optical fiber cannot be easily adjusted when preparing optical fibers with varying core-cladding ratios.

[0006] According to a first aspect of the present invention, a method for fabricating a tapered optical fiber is provided, comprising: Prepare a core rod doped with rare earth ions and then polish the core rod. The polished core rod is inserted into a sleeve with a receiving hole to obtain an optical fiber preform. The tip of the optical fiber preform is heated. When the temperature of the optical fiber preform exceeds the preset temperature value, a thrust is applied to the tail of the core rod to melt the tip of the core rod and fill it into the sleeve. Continue heating the tip of the optical fiber preform to maintain its temperature within a preset range. Draw the optical fiber preform into fibers while simultaneously evacuating the accommodating hole of the sleeve. Adjust the inner diameter of the molten region at the tip of the sleeve to adjust the core-to-cladding ratio of the resulting tapered optical fiber at different cross-sections.

[0007] According to a preparation method provided by the present invention, the preparation of a core rod doped with rare earth ions includes: Pickling of precast quartz tubes; A loose layer of glass particles is deposited on the inner wall of a prefabricated quartz tube, and then rare earth ions are doped into the loose layer of glass particles.

[0008] According to a preparation method provided by the present invention, the grinding process of the mandrel includes grinding the diameter of the mandrel to between 5 and 8 mm.

[0009] According to a preparation method provided by the present invention, the step of inserting the polished core rod into a sleeve having a receiving hole to obtain an optical fiber preform includes: A tail shank is coaxially connected to the tail of the core rod, and a support tube is coaxially connected to the tail of the sleeve. The conical tip of the core rod is inserted into the sleeve to obtain the optical fiber preform.

[0010] According to a preparation method provided by the present invention, the tail end of the support tube is provided with a sealing device, and the tail stick can extend through the sealing device to the outside of the support tube.

[0011] According to a preparation method provided by the present invention, the side of the support tube is connected to an air guide tube, one end of the air guide tube is connected to the receiving hole of the sleeve, and the other end is used to connect to a negative pressure device.

[0012] According to a preparation method provided by the present invention, the preset temperature value is 2000℃.

[0013] According to a preparation method provided by the present invention, the preset temperature range is 2100℃ to 2300℃.

[0014] According to a preparation method provided by the present invention, the rare earth ions include one of the following elements: ytterbium, erbium, holmium, and thulium.

[0015] According to a second aspect of the present invention, a tapered optical fiber is provided, which is prepared by the method for preparing a tapered optical fiber according to any one of the first aspects of the present invention.

[0016] The preparation method provided by this invention includes applying a pushing force to the tail of the core rod during the fiber drawing process, allowing the tapered tip of the core rod to melt at a certain temperature and fill into the sleeve. Then, the tapered tip of the sleeve is further heated, and a vacuum is applied to the receiving hole of the sleeve within a preset temperature range, causing the sleeve to shrink at high temperature, thereby adjusting the inner diameter of the tapered tip. Therefore, in this preparation method, the diameter of the sleeve can be changed by adjusting the negative pressure of the vacuum in the fiber preform, achieving controllable core-to-cladding ratio of the tapered fiber, and ultimately enabling mass production of the required tapered fiber. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of a method for preparing a tapered optical fiber according to one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an optical fiber preform for preparing tapered optical fibers according to one embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the relationship between the preform negative pressure and the fiber core-cladding ratio along the length of the optical fiber, according to one embodiment of the present invention. Figure 4 This is a schematic diagram of the structure of a tapered optical fiber according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a tapered optical fiber according to another embodiment of the present invention.

[0019] Figure label: 1. Core rod; 2. Tail shank rod; 3. Sleeve; 4. Support tube; 5. Sealing device; 6. Air guide tube. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] In one embodiment of the present invention, a method for fabricating a tapered optical fiber and a tapered optical fiber are provided. In this method, the viscosity difference between rare-earth-doped glass and cladding glass materials is utilized; specifically, the rare-earth-doped glass has a lower glass transition temperature than the cladding material, resulting in lower core viscosity and better flowability. Since the cladding is relatively thick, negative pressure is required to shrink the inner diameter of the cladding to fit the core. A tapered optical fiber with a controllable core-to-cladding ratio is fabricated by adjusting the pressure within the preform. The following is combined with… Figures 1 to 5 The method for preparing the tapered optical fiber and the tapered optical fiber in this embodiment are further described below.

[0022] like Figure 1 As shown, the method for fabricating the tapered optical fiber in this embodiment includes: S1: Prepare a core rod doped with rare earth ions and polish the core rod. S2: Insert the polished core rod into the sleeve with the receiving hole to obtain the optical fiber preform. S3: Heat the tip of the optical fiber preform. When the temperature of the optical fiber preform exceeds the preset temperature value, apply a thrust to the tail of the core rod to melt the tip of the core rod and fill it into the sleeve. S4: Continue heating the tip of the optical fiber preform to maintain its temperature within the preset range. Draw the optical fiber preform into fibers while simultaneously evacuating the accommodating hole of the sleeve. Adjust the inner diameter of the molten region at the tip of the sleeve to adjust the core-to-cladding ratio of the resulting tapered optical fiber at different cross sections.

[0023] For example, in step S1, production needs may be required to determine the type of rare earth ions to be doped, and the corresponding rare earth ions are doped into the quartz tube to initially obtain a core rod. Then, the core rod is polished so that the outer surface of the core rod is close to the doped area, and the thickness of the quartz glass outside the doped area is minimized to facilitate subsequent processing.

[0024] Common methods for fabricating core rods include chemical vapor deposition (MCVD), external vapor deposition (OVD), axial chemical vapor deposition (VAD), and plasma chemical vapor deposition (PCVD). This embodiment uses chemical vapor deposition to fabricate the doped core rod.

[0025] Specifically, in this embodiment, the preparation of the rare-earth-doped core rod includes: Pickling of precast quartz tubes; A loose layer of glass particles is deposited on the inner wall of a prefabricated quartz tube, and then rare earth ions are doped into the loose layer of glass particles.

[0026] Understandably, after selecting or preparing the pre-made quartz tube, acid washing of the pre-made quartz tube can effectively reduce the introduction of impurities and ensure the processing quality of the tapered optical fiber.

[0027] In some examples, prefabricated quartz tubes can be immersed in hydrofluoric acid solution for a time of 200 minutes or more to remove impurities.

[0028] After the precast quartz tube is acid-washed, a rotary joint is installed at the air inlet end of the precast quartz tube. The precast quartz tube is then installed on a deposition lathe. An improved chemical vapor deposition method can be used to deposit a loose layer of glass particles on the inner wall of the precast quartz tube, and then rare earth ion doping is performed on the loose layer of glass particles.

[0029] In one specific embodiment, the prefabricated quartz tube is first preheated externally using an oxyhydrogen flame, and during the preheating process, the temperature of the prefabricated quartz tube is gradually increased to 1200°C.

[0030] Then, a gaseous feedstock is introduced into the precast quartz tube at a preset flow rate. The gaseous feedstock is any one or a combination of at least two of SiCl4, BCl3, GeCl4, and POCl3. Prior to this, SF6 is introduced into the precast quartz tube to etch the inner wall of the tube several times, and the tube is then heated while the gaseous feedstock is introduced.

[0031] When the gas raw material is introduced, the temperature of the precast quartz tube is controlled to be heated to 1400℃~1700℃, and the precast quartz tube is controlled to rotate until a loose layer of glass particles of a specified thickness is deposited on the inner wall surface of the precast quartz tube.

[0032] During or after the deposition of the porous glass particle layer, rare earth ions can be doped into the porous glass particle layer to obtain the desired core rod doped with rare earth ions.

[0033] Furthermore, the diameter of the mandrel obtained in conventional processes is typically 10 to 20 mm, and the diameter of the rare earth ion-doped region is approximately 2 to 5 mm.

[0034] As mentioned above, after the preparation of the core rod 1 by doping with rare earth ions, the outer surface of the core rod 1 needs to be polished to the doped area or the nearby area in order to minimize the thickness of the pure silicon layer outside the doped area and avoid affecting the fluidity of the core rod after melting.

[0035] In order to facilitate the subsequent wire drawing process, in this embodiment, the mandrel is polished, including: polishing the diameter of the mandrel to between 5 and 8 mm.

[0036] For example, in step S2, a suitable sleeve needs to be selected based on the structure and length of the target tapered fiber core-cladding ratio. For example, adjustments such as the range of core-cladding ratio variation and the required range of tapered length can be considered. Then, the core rod obtained in step S1 and the selected sleeve are assembled to obtain an optical fiber preform that can be placed on a drawing tower for drawing.

[0037] Specifically, the polished core rod is inserted into a sleeve with a receiving hole selected according to production requirements to obtain an optical fiber preform, including: A tail shank is coaxially connected to the tail of the core rod, and a support tube is coaxially connected to the tail of the sleeve. The conical tip of the core rod is inserted into the sleeve to obtain the optical fiber preform.

[0038] For example, Figure 2 An optical fiber preform of this embodiment is shown. In this optical fiber preform, the core rod 1 is obtained via step S1, wherein the rare earth ions doped into the core rod 1 include, but are not limited to, elements such as ytterbium, erbium, holmium, and thulium. For example, the core rod in this embodiment is a ytterbium-doped core rod with high phosphorus doping. The two ends of the core rod 1 along its length are a head and a tail, respectively, and the head of the core rod 1 is formed into a conical tip.

[0039] The tail rod 2 can be a glass rod, and its diameter is approximately equal to that of the core rod 1. The tail rod 2 is coaxially connected to the tail of the core rod 1. The tail rod 2 is used to transfer external thrust to the core rod 1 during the wire drawing process.

[0040] The sleeve 3 can be a high-purity quartz glass tube. The inner diameter of the sleeve 3 is small while the outer diameter is large, so the cross-sectional area of ​​the sleeve 3 is also large. During the wire drawing process, the inner diameter will only shrink under very high temperature and negative pressure conditions. The two ends of the sleeve 3 along its length are the head and the tail, respectively. The head of the sleeve 3 is formed into a cone tip.

[0041] In this embodiment, the sleeve 3 is the main material constituting the optical fiber cladding structure, and it is combined with the core rod 1 to form the optical fiber cladding structure.

[0042] The support tube 4 can also be a glass tube. The outer diameter of the support tube 4 is approximately equal to the outer diameter of the sleeve 3, and the inner diameter of the support tube 4 is smaller than the inner diameter of the sleeve 3. Optionally, the wall thickness of the support tube 4 can be 3 to 8 mm. The support tube 4 is also coaxially connected to the tail of the sleeve 3. The support tube 4 can serve as a support structure so that the entire optical fiber preform is clamped on the drawing tower.

[0043] In order to enable the receiving hole of the sleeve 3 to effectively form a negative pressure and ensure that the external thrust can be transmitted to the mandrel 1, a sealing device 5 is provided at the tail end of the support tube 4. The sealing device 5 can seal the tail end of the support tube 4, and the tail stick 2 can extend through the sealing device 5 to the outside of the support tube 4.

[0044] As one implementation, the sealing device 5 has a through hole at its center, the inner diameter of which is slightly smaller than the outer diameter of the tail rod 2. The tail rod 2 can be inserted into the through hole, and a sealing ring is provided between the through hole and the tail rod 2, and the sealing is achieved with sealing grease. This ensures that the receiving hole of the sleeve 3 has sufficient airtightness, and at the same time, the tail rod 2 can move axially relative to the sealing device 5.

[0045] In this embodiment, during the wire drawing process, a vacuum treatment needs to be performed on the receiving hole of the sleeve 3 to create a negative pressure inside the sleeve 3, thereby controlling the change in the diameter of the sleeve 3. For this purpose, as follows... Figure 2 As shown, a gas guide pipe 6 is connected to the side of the support tube 4. One end of the gas guide pipe 6 is connected to the receiving hole of the sleeve 3, and the other end is used to connect to the negative pressure device. Thus, in actual use, the negative pressure device can perform vacuum treatment on the receiving hole of the sleeve 3, thereby achieving a negative pressure state in the sealed space inside the optical fiber preform.

[0046] As one implementation, the gas guide tube 6 can be constructed as a glass tube. When the gas guide tube 6 needs to be installed, a hole can be drilled at one end of the support tube 4 near the sealing device 5, and then the gas guide tube 6 can be connected to the through hole by flame welding. Optionally, the outer diameter of the gas guide tube 6 can be controlled to be 4 to 6 mm.

[0047] Once the fiber preform in step S2 is assembled, it can be installed on the drawing tower for drawing.

[0048] Specifically, in this embodiment, in step S3, the entire optical fiber preform can be fixed on the drawing tower by means of the support tube 4 with the conical tip of the sleeve 3 facing down and the tail of the support tube 4 facing up, while the negative pressure device is connected to the air duct 6.

[0049] Then, the tip of the optical fiber preform (i.e. the tip of sleeve 1) is heated until the head temperature of the optical fiber preform exceeds 2000℃, that is, the preset temperature value can be 2000℃.

[0050] Next, a downward thrust can be applied to the tail rod 2. During this thrust application, it is crucial to ensure that the mandrel 1 does not break. It is understood that because the inner diameter of the sleeve 3 is larger than the outer diameter of the mandrel 1, the molten mandrel 1 needs to fall at a certain speed to completely fill the receiving hole of the sleeve 3. Applying pressure allows the mandrel 1 to fall normally and at a uniform speed, ensuring the stability of the volume of rare-earth-doped glass molten per unit time.

[0051] Since the core rod 1 is doped with rare earth ions, the doped region in the core rod 1 has a relatively low glass transition temperature. In step S3, at this current temperature, the head of the core rod 1 can be melted in small amounts in advance and fully filled into the receiving hole of the sleeve 3.

[0052] It is understandable that the outer diameter of the mandrel 1 is smaller than the inner diameter of the receiving hole of the sleeve 3. After the mandrel 1 is inserted into the receiving hole of the sleeve 3, there is a small gap between the mandrel 1 and the inner wall of the receiving hole of the sleeve 3. At this time, under high temperature environment, the mandrel 1 will melt and fully fill the receiving hole.

[0053] Next, in step S4, the tip of the optical fiber preform is heated further, causing the temperature of the tip to continue to rise. When the temperature of the tip of the optical fiber preform reaches between 2100°C and 2300°C, that is, within the preset temperature range of 2100°C to 2300°C, the tip of the sleeve 3 reaches the melting temperature. A portion of the tip of the sleeve 3 changes from a solid state to a fluid state, and this region is the melting region. Then, the optical fiber preform can be drawn into fibers. At the same time, a vacuum is drawn into the receiving hole of the sleeve 3 using a negative pressure device, creating a negative pressure inside the sleeve 3.

[0054] During the fiber drawing process, the sleeve 3 will shrink according to the current negative pressure, and the diameter of the sleeve 3 will change, ultimately altering the core-to-cladding ratio of the optical fiber at different cross-sections. Furthermore, the negative pressure within the receiving hole prevents defects such as bubbles from forming at the molten interface.

[0055] In practice, by setting different negative pressure values ​​at different positions along the length of the optical fiber preform, the core-to-cladding ratio along the fiber length can be effectively controlled. Moreover, during the fiber drawing process, PID control of the cladding can be adopted to keep the cladding diameter of the fiber stable, ultimately resulting in a tapered fiber with a constant cladding diameter but a gradually changing core-to-cladding ratio.

[0056] As described above, this embodiment also provides a tapered optical fiber, which is prepared by the preparation method described in the above embodiment.

[0057] Figure 3The graph shows the relationship between the negative pressure in the sealed space of the optical fiber preform and the core-to-cladding ratio of the optical fiber along the length of the optical fiber. It can be clearly seen from the graph that as the negative pressure in the preform increases, the core-to-cladding ratio of the optical fiber will gradually decrease.

[0058] In one embodiment, when it is necessary to prepare a cladding diameter of 400 μm, a variable core-to-cladding ratio, ytterbium doping, and a shape as shown... Figure 4 When preparing the spindle-shaped tapered optical fiber, firstly, a ytterbium-doped core rod can be prepared, wherein the diameter of the ytterbium-doped region is controlled to be 3 mm. Then, the core rod is polished to an outer diameter of about 6 mm. Next, a sleeve with an inner diameter of 10 mm, an outer diameter of 36 mm, and a length of 400 mm is selected, and the optical fiber preform is assembled with the help of a tail rod, a support tube, and a sealing device.

[0059] Next, the obtained optical fiber preform is installed in a drawing tower for drawing. During the drawing process, the drawing temperature is controlled at 2180℃, that is, the head of the optical fiber preform is heated to about 2180℃, and then the drawing speed is about 12m / min. A vertical downward pressure of 1N is applied to the tail of the core rod, that is, a vertical downward thrust of 1N is applied to the tail of the tail rod. At the same time, a vacuum is applied to the sealed space in the optical fiber preform using a negative pressure device, so that the negative pressure of the sealed space varies within the range of 5kPa to 90kPa, resulting in an optical fiber cross-section with a core-to-cladding ratio in the range of 0.05-0.15. Then, the pressure curve of the preform is designed into a periodic variation program using software to change the pressure at different positions of the preform. Finally, the desired optical fiber cross-section can be obtained. Figure 4 The tapered optical fiber shown.

[0060] In yet another embodiment, when it is necessary to prepare a cladding diameter of 800 μm, a variable core-to-cladding ratio, ytterbium doping, and a shape as shown... Figure 5 When preparing the stepped tapered optical fiber shown, firstly, a ytterbium-doped core rod can be prepared, wherein the diameter of the ytterbium-doped region is controlled to be 3 mm. Then, the core rod is polished to an outer diameter of about 4 mm. Next, a sleeve with an inner diameter of 7 mm, an outer diameter of 36 mm, and a length of 400 mm is selected, and the fiber preform is assembled with the help of a tailstock rod, a support tube, and a sealing device.

[0061] Next, the obtained optical fiber preform is installed in a drawing tower for drawing. During the drawing process, the drawing temperature is controlled at 2250℃, that is, the head of the optical fiber preform is heated to about 2250℃, and then the drawing speed is about 8m / min. A vertical downward pressure of 1.5N is applied to the tail of the core rod, that is, a vertical downward thrust of 1.5N is applied to the tail of the tail rod. At the same time, a vacuum is applied to the sealed space in the optical fiber preform using a negative pressure device, so that the negative pressure of the sealed space varies within the range of 20kPa to 95kPa, resulting in an optical fiber cross-section with a core-to-cladding ratio in the range of 0.05-0.15. Then, the pressure curve of the preform is designed into a periodic variation program using software to change the pressure at different positions of the preform. Finally, the desired optical fiber cross-section can be obtained. Figure 5 The tapered optical fiber shown.

[0062] Therefore, the method for fabricating the tapered optical fiber in this embodiment has the following advantages: In the preparation method of this embodiment, the drawing process includes applying a pushing force to the tail of the core rod, allowing the cone tip of the core rod to melt at a certain temperature and fill into the sleeve. Then, the cone tip of the sleeve is further heated, and a vacuum is applied to the receiving hole of the sleeve within a preset temperature range, causing the sleeve to shrink at high temperature, thereby adjusting the inner diameter of the sleeve cone tip. Therefore, in this preparation method, the diameter of the sleeve can be changed by adjusting the negative pressure of the vacuum in the fiber preform, achieving controllable core-to-cladding ratio of the tapered fiber, and ultimately enabling mass production of the desired tapered fiber.

[0063] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a tapered optical fiber, characterized in that, include: Prepare a core rod doped with rare earth ions and then polish the core rod. The polished core rod is inserted into a sleeve with a receiving hole to obtain an optical fiber preform. The tip of the optical fiber preform is heated. When the temperature of the optical fiber preform exceeds the preset temperature value, a thrust is applied to the tail of the core rod to melt the tip of the core rod and fill it into the sleeve. Continue heating the tip of the optical fiber preform to maintain its temperature within a preset range. Draw the optical fiber preform into fibers while simultaneously evacuating the accommodating hole of the sleeve. Adjust the inner diameter of the molten region at the tip of the sleeve to adjust the core-to-cladding ratio of the resulting tapered optical fiber at different cross sections. Among them, the core-to-cladding ratio in the fiber length direction is controlled by setting different negative pressure values ​​at different positions along the fiber preform length, and the cladding diameter of the fiber is kept stable by adopting PID control of the cladding during the fiber drawing process.

2. The preparation method according to claim 1, characterized in that, The preparation of the core rod doped with rare earth ions includes: Pickling of precast quartz tubes; A loose layer of glass particles is deposited on the inner wall of a prefabricated quartz tube, and then rare earth ions are doped into the loose layer of glass particles.

3. The preparation method according to claim 1, characterized in that, The grinding process of the mandrel includes grinding the diameter of the mandrel to between 5 and 8 mm.

4. The preparation method according to claim 1, characterized in that, The step of inserting the polished core rod into a sleeve with a receiving hole to obtain an optical fiber preform includes: A tail shank is coaxially connected to the tail of the core rod, and a support tube is coaxially connected to the tail of the sleeve. The conical tip of the core rod is inserted into the sleeve to obtain the optical fiber preform.

5. The preparation method according to claim 4, characterized in that, The tail end of the support tube is provided with a sealing device, and the tail stick can extend through the sealing device to the outside of the support tube.

6. The preparation method according to claim 4, characterized in that, The side of the support tube is connected to an air guide tube. One end of the air guide tube is connected to the receiving hole of the sleeve, and the other end is used to connect to a negative pressure device.

7. The preparation method according to claim 1, characterized in that, The preset temperature value is 2000℃.

8. The preparation method according to claim 1, characterized in that, The preset temperature range is 2100℃ to 2300℃.

9. The preparation method according to claim 1, characterized in that, The rare earth ions include one of the following elements: ytterbium, erbium, holmium, and thulium.

10. A tapered optical fiber, characterized in that, The tapered optical fiber is prepared using the method for preparing tapered optical fibers as described in any one of claims 1 to 9.

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