Method for preparing anti-bending optical fiber preform, optical fiber preform and optical fiber

Abstract

The embodiment of the invention provides a method for preparing a bending-resistant optical fiber preform, the optical fiber preform and an optical fiber, and relates to the technical field of optical fibers, the method for preparing the bending-resistant optical fiber preform comprises the following steps: depositing a powder body on a bearing part, and then taking the bearing part out of the powder body to form a hollow powder body; a core rod is inserted into the hollow powder body, and a to-be-sintered part is formed; and soaking and sintering the to-be-sintered part with low-refractive-index gas to form the optical fiber preform. According to the method for preparing the anti-bending optical fiber preform, the optical fiber preform and the optical fiber provided by the embodiment of the invention, the problem of poor quality of the optical fiber preform and an optical fiber finished product in related technologies is solved.

Description

Technical Field

[0001] This application relates to the field of optical fiber technology, and in particular to a method for preparing a bend-resistant optical fiber preform, the optical fiber preform, and the optical fiber. Background Technology

[0002] Optical fiber preforms are the core raw materials for drawing glass fibers (such as optical fibers). Their structure or manufacturing process can directly affect the transmission loss, mechanical strength and environmental adaptability of the final optical fiber.

[0003] In related technologies, the preparation method of optical fiber preforms involves depositing powder on a core rod, and then sintering the core rod and powder together under normal pressure fluorine gas. This forms the optical fiber preform and achieves fluorine doping in the preform.

[0004] However, during the melting and sintering process, uneven penetration of fluorine gas into the optical fiber preform or residual air inside the optical fiber preform can easily occur, affecting the quality of the optical fiber preform and the finished optical fiber. Summary of the Invention

[0005] This application provides a method for preparing a bend-resistant optical fiber preform, an optical fiber preform, and an optical fiber, in order to solve the problem of poor quality of finished optical fiber preforms and optical fibers in related technologies.

[0006] In a first aspect, this application provides a method for preparing a bend-resistant optical fiber preform, comprising the following steps:

[0007] Powder is deposited on a carrier, and then the carrier is removed from the powder to form a hollow powder body;

[0008] A mandrel is inserted into the hollow powder body to form a part to be sintered;

[0009] The part to be sintered is immersed in a low-refractive-index gas and sintered to form an optical fiber preform.

[0010] In one possible implementation, the step of immersing the workpiece in a low-refractive-index gas and sintering includes:

[0011] The pressure during sintering is less than or equal to 20 Pa.

[0012] In one possible implementation, the step of immersing the workpiece in a low-refractive-index gas and sintering includes:

[0013] The workpiece to be sintered is placed in a sintering furnace, and the low refractive index gas is introduced into the sintering furnace through a pipe on the sintering furnace, so that the workpiece to be sintered undergoes a first dehydroxylation sintering, immersion in the low refractive index gas, and a second melting and shrinkage sintering in the sintering furnace in sequence.

[0014] In one possible implementation, the pressure during sintering is less than or equal to 20 Pa, including:

[0015] During both the primary dehydroxylation sintering and the secondary melting and shrinkage sintering, the pressure inside the sintering furnace is controlled to be less than or equal to 20 Pa by the pressure control device on the sintering furnace.

[0016] In one possible implementation, the step of sequentially subjecting the workpiece to be sintered in the sintering furnace to a first dehydroxylation sintering, the low refractive index gas immersion, and a second melting-shrinkage sintering includes:

[0017] The workpiece to be sintered is subjected to the first dehydroxylation sintering in the sintering furnace; wherein the heating temperature is increased at 3~10℃ / min to greater than or equal to 800℃ and less than or equal to 1300℃, and the holding time is greater than or equal to 1h and less than or equal to 4~8h.

[0018] The low-refractive-index gas is introduced into the sintering furnace, and the workpiece to be sintered after the first dehydroxylation sintering is immersed in the low-refractive-index gas in the sintering furnace; wherein, the immersion temperature is greater than or equal to 800℃ and less than or equal to 1300℃, the immersion time is greater than or equal to 0.5h and less than or equal to 6h, and the flow rate of the low-refractive-index gas is greater than or equal to 1L / min and less than or equal to 40L / min;

[0019] Stop feeding the low-refractive-index gas into the sintering furnace, and then perform the secondary melting and shrinkage sintering on the workpiece that has been soaked in the low-refractive-index gas in the sintering furnace; wherein, the heating temperature is increased at 4℃ / min to greater than or equal to 1500℃ and less than or equal to 1800℃ to continue melting and shrinkage sintering, and the holding time is greater than or equal to 2h and less than or equal to 10h.

[0020] In one possible implementation, depositing powder on the carrier includes:

[0021] A cylindrical rod is placed in a deposition chamber, and the powder is deposited on the cylindrical rod by chemical vapor deposition; wherein the density of the powder is greater than or equal to 0.15 g / cm³. 3 And less than or equal to 1.5 g / cm 3 .

[0022] In one possible implementation, the deposition of the powder on the cylindrical rod by chemical vapor deposition includes:

[0023] A deposition gas is introduced into at least one torch in the deposition chamber to deposit the powder onto the cylindrical rod; wherein the deposition gas comprises hydrogen, oxygen, argon, and silicon tetrachloride.

[0024] In one possible implementation, the introduction of deposition gas into at least one torch within the deposition chamber includes:

[0025] The deposition gas is introduced into the first, second, third, and fourth blowtorches that are sequentially spaced apart along the length of the cylindrical rod in the deposition chamber.

[0026] In one possible implementation, the deposition gas is introduced into the first, second, third, and fourth blowtorches, which are sequentially spaced apart along the length of the cylindrical rod within the deposition chamber, including:

[0027] The distance between the line connecting the center point of the nozzle of the first blowtorch and the center point of the nozzle of the second blowtorch is set to be greater than or equal to 60mm and less than or equal to 150mm.

[0028] And / or, the distance between the line connecting the center point of the nozzle of the second blowtorch and the center point of the nozzle of the third blowtorch is set to be greater than or equal to 60 mm and less than or equal to 150 mm.

[0029] And / or, the distance between the line connecting the center point of the nozzle of the third torch and the center point of the nozzle of the fourth torch is set to be greater than or equal to 60 mm and less than or equal to 150 mm.

[0030] In one possible implementation, placing the cylindrical rod into the deposition chamber includes:

[0031] One end of the cylindrical rod extending in the direction of extension is inserted into the base, and a connector is used to simultaneously insert the cylindrical rod and the base to fix the cylindrical rod on the base;

[0032] The cylindrical rod is placed into the deposition chamber via the base.

[0033] Secondly, the optical fiber preform provided in this application is manufactured using the method for preparing a bend-resistant optical fiber preform as described in any of the above embodiments.

[0034] Thirdly, the optical fiber provided in this application is made using the optical fiber preform described in the above embodiments. The optical fiber has a low refractive index of -0.1% to -0.45%, a hydroxyl content of less than 0.1 ppm, a bubble rate of less than 0.01%, and an axial refractive index fluctuation of ≤0.02%.

[0035] This application provides a method for preparing a bend-resistant optical fiber preform, an optical fiber preform, and an optical fiber. The method for preparing the bend-resistant optical fiber preform includes the following steps: depositing powder on a carrier, then removing the carrier from the powder to form a hollow powder; inserting a core rod into the hollow powder to form a component to be sintered; and immersing and sintering the component to be sintered in a low-refractive-index gas to form the optical fiber preform. By immersing the component to be sintered in a low-refractive-index gas, fluorine can penetrate the powder in both the axial and radial directions, improving the uniformity of fluorine distribution in the formed optical fiber preform. Fluorine also penetrates to the interface region between the outer surface of the core rod and the inner surface of the hollow powder, forming a fluorine-doped, deeply recessed refractive index layer. This layer has a significantly lower refractive index than the core layer (formed by the core rod) and matches the refractive index of the cladding layer (formed by the hollow powder), creating a stable refractive index distribution. This effectively reduces transmission loss during subsequent optical fiber use (such as during bending), resulting in excellent bend resistance of the optical fiber. This improves the quality of optical fiber preforms and finished optical fibers, solving the problem of poor quality of optical fiber preforms and finished optical fibers in related technologies. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0037] Figure 1 A flowchart illustrating a method for preparing a bend-resistant optical fiber preform provided in this application embodiment;

[0038] Figure 2 This is a schematic diagram of the structure of powder deposited on a carrier in a method for preparing a bend-resistant optical fiber preform provided in an embodiment of this application;

[0039] Figure 3 This is a schematic diagram of the structure of the optical fiber preform formed in a method for preparing a bend-resistant optical fiber preform according to an embodiment of this application;

[0040] Figure 4 This is a schematic diagram of the sintering apparatus used in a method for preparing a bend-resistant optical fiber preform provided in an embodiment of this application.

[0041] Figure 5 A schematic diagram of the deposition chamber in a deposition apparatus used in a method for preparing a bend-resistant optical fiber preform provided in this application embodiment;

[0042] Figure 6 This is a schematic diagram of the mounting structure of the carrier on the base in a method for preparing a bend-resistant optical fiber preform according to an embodiment of this application;

[0043] Figure 7 The refractive index distribution of the fiber preform in Example 1 is shown in the example of a method for preparing a bend-resistant optical fiber preform provided in this application.

[0044] Figure 8 The refractive index distribution of the fiber preform in Comparative Example 1 is shown in the figure. This method for preparing a bend-resistant optical fiber preform is provided in the embodiments of this application.

[0045] Figure 9 The refractive index distribution of the fiber preform is shown in Example 2, which illustrates a method for preparing a bend-resistant fiber preform according to an embodiment of this application.

[0046] Explanation of reference numerals in the attached figures:

[0047] 100 - Load-bearing component;

[0048] 200-Powder body;

[0049] 300-core rod;

[0050] 400-Depression layer;

[0051] 500 - Sintering device; 510 - Sintering furnace; 511 - Heating zone; 512 - Furnace tube; 520 - Pipeline; 530 - Pressure control component;

[0052] 600 - Deposition apparatus; 610 - Deposition chamber; 620 - First blowtorch; 630 - Second blowtorch; 640 - Third blowtorch; 650 - Fourth blowtorch; 660 - Base; 670 - Connector.

[0053] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0054] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0055] In related technologies, optical fiber preforms are the core raw materials for drawing glass fibers (such as optical fibers), and their structure or manufacturing process can directly affect the transmission loss, mechanical strength and environmental adaptability of the final optical fiber.

[0056] The optical fiber preform is fabricated by depositing powder onto a core rod, followed by melting and sintering the core rod and powder together under ambient pressure in a fluorine gas environment. This process forms the optical fiber preform and achieves fluorine doping within it.

[0057] However, during melt sintering, uneven permeation of fluorine gas into the optical fiber preform or the presence of residual air inside the preform can easily occur. This results in poor uniformity of fluorine distribution in the prepared optical fiber preform and a tendency to generate bubbles, affecting the quality of both the preform and the finished optical fiber.

[0058] For example, the poor uniformity of fluorine distribution can affect the stability of the refractive index distribution of optical fibers; and bubbles can scatter light signals, which can easily increase the attenuation loss of optical fibers.

[0059] Based on this, embodiments of this application provide a method for preparing a bend-resistant optical fiber preform, an optical fiber preform, and an optical fiber. The method for preparing the bend-resistant optical fiber preform includes the following steps: depositing powder on a carrier, then removing the carrier from the powder to form a hollow powder; inserting a core rod into the hollow powder to form a component to be sintered; and immersing and sintering the component to be sintered in a low-refractive-index gas to form the optical fiber preform. Thus, by immersing the component to be sintered in a low-refractive-index gas, fluorine can penetrate the powder in both the axial and radial directions relatively uniformly, improving the uniformity of fluorine distribution in the formed optical fiber preform. Fluorine also penetrates to the interface region between the outer surface of the core rod and the inner surface of the hollow powder, forming a fluorine-doped, deeply recessed refractive index layer. This layer has a significantly lower refractive index than the core layer (formed by the core rod) and matches the refractive index of the cladding layer (formed by the hollow powder), creating a stable refractive index distribution. This effectively reduces transmission loss during subsequent optical fiber use (such as during bending), resulting in excellent bend resistance of the optical fiber. This improves the quality of optical fiber preforms and finished optical fibers, solving the problem of poor quality of optical fiber preforms and finished optical fibers in related technologies.

[0060] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0061] like Figure 1 , Figure 2 and Figure 3 As shown in the embodiment of this application, a method for preparing a bend-resistant optical fiber preform includes the following steps:

[0062] S101. Deposit powder 200 on the carrier 100;

[0063] S102. Remove the carrier 100 from the powder body 200 to form a hollow powder body 200;

[0064] S103. Insert the mandrel 300 into the hollow powder body 200 to form the part to be sintered. The mandrel 300 can be an ultra-low loss mandrel 300 or a bend-insensitive mandrel 300, etc., and the selection of the mandrel 300 is not limited according to actual needs. Furthermore, before inserting the mandrel 300 into the powder body 200, the mandrel 300 can be pretreated, for example: ultrasonically cleaned in a 12% hydrofluoric acid solution for 18 minutes, rinsed with deionized water at a flow rate of 1.0 L / min for 9 minutes, and then dried in a drying oven at 135℃ for 2.5 hours. Of course, other methods can also be used to pretreat the mandrel 300.

[0065] S104. The part to be sintered is immersed in a low refractive index gas and sintered to form an optical fiber preform.

[0066] Therefore, by immersing the part to be sintered in a low-refractive-index gas, fluorine can penetrate the powder body 200 in a relatively uniform manner in both the axial and radial directions, thereby improving the uniformity of fluorine distribution in the formed optical fiber preform and improving the quality of the optical fiber preform and finished optical fiber.

[0067] Fluorine also permeates to the interface region between the outer surface of the mandrel 300 and the inner surface of the hollow powder body 200, forming a fluorine-doped, uniformly recessed, deeply refractive layer 400. For example... Figure 3 The diagram shows the structure of the formed optical fiber preform. From the inside out, it consists of a core layer (formed by core rod 300), a recessed layer 400, and a cladding layer (formed by hollow powder 200). The refractive index of the recessed layer 400 is significantly lower than that of the core layer, while matching the refractive index of the cladding layer. This creates a stable refractive index distribution, effectively reducing transmission loss during subsequent fiber use (such as bending), resulting in excellent fiber bending resistance. This improves the quality of the optical fiber preform and finished optical fiber, solving the problem of poor quality in related technologies.

[0068] The process of immersing the workpiece in a low-refractive-index gas and sintering it includes sintering at a pressure of less than or equal to 20 Pa.

[0069] Therefore, by controlling the sintering pressure to less than or equal to 20 Pa, moisture in the sintering material can be effectively removed, hydroxyl group formation can be inhibited, and the hydroxyl content in the formed optical fiber preform can be reduced, giving the optical fiber preform low hydroxyl group characteristics. At the same time, it reduces the generation of bubbles in the optical fiber preform, improving the quality of both the optical fiber preform and the finished optical fiber.

[0070] During implementation, a sintering device 500 can be used to immerse the workpiece in a low refractive index gas and perform sintering treatment.

[0071] Specifically, such as Figure 4 As shown, the sintering apparatus 500 includes a sintering furnace 510, a pipeline 520, and a pressure control component 530. Both the pipeline 520 and the pressure control component 530 are connected to the sintering furnace 510. The pipeline 520 is used to introduce low-refractive-index gas into the sintering furnace 510. The pressure control component 530 is used to regulate the internal pressure of the sintering furnace 510. The pressure control component 530 can be a valve, safety valve, air pump, etc., connected to the sintering furnace 510.

[0072] The sintering furnace 510 includes a heating zone 511 and a furnace tube 512 disposed inside the heating zone 511. The heating zone 511 can be heated by high-frequency induction heating, resistance heating, infrared heating, or other methods. In use, the workpiece to be sintered (i.e., the entire assembly of the mandrel 300 and the powder body 200) can be inserted into the furnace tube 512 for heating and sintering. The sintering furnace 510 can also use existing products, and its specific structure is not limited.

[0073] In some embodiments, immersing the workpiece in a low refractive index gas and sintering it further includes:

[0074] The workpiece to be sintered is placed in the sintering furnace 510, and a low refractive index gas is introduced into the sintering furnace 510 through the pipe 520 on the sintering furnace 510, so that the workpiece to be sintered undergoes a first dehydroxylation sintering, a low refractive index gas immersion, and a second melting shrinkage sintering in the sintering furnace 510 in sequence.

[0075] In this embodiment, helium and a low-refractive-index gas can be simultaneously introduced into the sintering furnace 510 through pipe 520. This allows the helium to dilute the low-refractive-index gas, reducing the possibility of excessively high local concentrations of the low-refractive-index gas within the sintering furnace 510. The low-refractive-index gas may include one or more fluorine-containing gases selected from carbon tetrafluoride (CF4), silicon tetrafluoride (SiF4), hexafluoroethane (C2F6), sulfur hexafluoride (SF6), sulfuryl difluoride (SOF2), difluorodichloroethane (C2F2Cl2), and octafluorocyclobutane (C4F8). Furthermore, the low-refractive-index gas can also be selected from helium, neon, etc., depending on actual requirements.

[0076] Therefore, by performing a dehydroxylation sintering on the part to be sintered under low pressure, the moisture in the part to be sintered can be effectively removed, the generation of hydroxyl groups can be inhibited, and the resulting optical fiber preform can be made with low hydroxyl characteristics.

[0077] By immersing the sintering part in a low-refractive-index gas, fluorine can be uniformly permeated in the axial and radial directions of the powder body 200, and also uniformly permeated between the outer surface of the mandrel 300 and the inner surface of the hollow powder body 200.

[0078] By performing secondary melting and shrinkage sintering on the part to be sintered under low pressure, the powder body 200 can be finally melted and shrunk to form a fluorine-doped optical fiber preform with a deep concave profile structure.

[0079] In some embodiments, the pressure during sintering is less than or equal to 20 Pa, including:

[0080] During both the primary dehydroxylation sintering and the secondary melting shrinkage sintering, the pressure (absolute pressure) inside the sintering furnace 510 is controlled to be less than or equal to 20 Pa by the pressure control device 530 on the sintering furnace 510. Of course, the pressure during the immersion of low refractive index gas can also be controlled to be less than or equal to 20 Pa.

[0081] This ensures a low-pressure environment within the sintering furnace 510, effectively removing moisture from the workpiece to be sintered and inhibiting hydroxyl generation; at the same time, it reduces the risk of residual gas within the sintering furnace 510 and promotes the uniform penetration of fluorine into the powder 200.

[0082] In some embodiments, the workpiece to be sintered undergoes a first dehydroxylation sintering, a low-refractive-index gas immersion, and a second melting-shrinkage sintering sequentially within the sintering furnace 510, which may specifically include:

[0083] The workpiece to be sintered is subjected to a single dehydroxylation sintering process in sintering furnace 510; wherein the heating temperature is increased at a rate of 3~10℃ / min to a temperature greater than or equal to 800℃ and less than or equal to 1300℃, and the holding time is greater than or equal to 1h and less than or equal to 4~8h; for example, the heating temperature can be increased at a rate of 6℃ / min, and the holding time can be greater than or equal to 1h and less than or equal to 4h.

[0084] Low refractive index gas (helium and low refractive index gas can also be introduced) is introduced into sintering furnace 510. The workpiece to be sintered after one dehydroxylation sintering is immersed in low refractive index gas in sintering furnace 510. The immersion temperature is greater than or equal to 800℃ and less than or equal to 1300℃, the immersion time is greater than or equal to 0.5h and less than or equal to 6h, and the flow rate of low refractive index gas is greater than or equal to 1L / min and less than or equal to 40L / min.

[0085] Stop introducing low-refractive-index gas into sintering furnace 510, and perform secondary melting and shrinkage sintering on the workpiece soaked in low-refractive-index gas in sintering furnace 510; wherein, the heating temperature is increased at 4℃ / min to greater than or equal to 1500℃ and less than or equal to 1800℃ to continue melting and shrinkage sintering, and the holding time is greater than or equal to 2h and less than or equal to 10h.

[0086] In practice, the optical fiber preform formed after secondary melting and sintering in the sintering furnace 510 can also undergo cooling post-treatment, for example, cooling the optical fiber preform to 400°C within 30 minutes. Finally, the optical fiber preform is removed from the sintering furnace 510.

[0087] Therefore, by implementing segmented primary dehydroxylation sintering, low-refractive-index gas immersion, and secondary melting-shrinkage sintering, and by controlling the temperature gradient (e.g., 6℃ / min heating for primary dehydroxylation sintering and 4℃ / min heating for secondary melting-shrinkage sintering) and pressure, precise control of the material structure can be achieved. This facilitates the removal of residual gas from the sintered part, reduces bubble formation, promotes uniform fluorine penetration and dehydroxylation, and simultaneously improves mechanical strength. The resulting optical fiber preform can achieve a refractive index of -0.1% to -0.45% in the deep recess (i.e., the 400-degree recessed layer) and a hydroxyl content of less than 0.1 ppm.

[0088] In practice, a deposition apparatus 600 can be used to deposit the powder 200 onto the carrier 100. Specifically, such as... Figure 5 and Figure 6 As shown, the deposition apparatus 600 includes a deposition chamber 610, a first blowtorch 620, a second blowtorch 630, a third blowtorch 640, a fourth blowtorch 650, a base 660, and a connector 670. The deposition chamber 610 is used to accommodate the carrier 100. The first blowtorch 620, the second blowtorch 630, the third blowtorch 640, and the fourth blowtorch 650 are all disposed in the deposition chamber 610 and are distributed sequentially at intervals along the length of the carrier 100 to perform segmented deposition on the carrier 100.

[0089] The base 660 has a socket, allowing one end of the carrier 100 in the extending direction to be inserted into the base 660. The connector 670 simultaneously inserts into the carrier 100 and the base 660 to secure the carrier 100 to the base 660.

[0090] In practice, the base 660 can be a quartz spherical tailstock, or other shapes or structures, without limitation. The connector 670 can be a quartz connecting rod, or other structures such as a pin, insert, etc.

[0091] Based on this, in some embodiments, depositing powder 200 on the carrier 100 includes:

[0092] A cylindrical rod is placed in the deposition chamber 610, and powder 200 is deposited on the cylindrical rod by chemical vapor deposition; wherein the density of powder 200 is greater than or equal to 0.15 g / cm³. 3 And less than or equal to 1.5 g / cm 3 In other words, in this embodiment, the support member 100 is set as a cylindrical rod. Of course, the support member 100 can also be set as a tubular or other shaped rod, and there is no limitation on this.

[0093] Thus, a loose powder body 200 is deposited on a cylindrical rod by chemical vapor deposition, and the powder body 200 has a better density.

[0094] For example, the selected cylindrical rod may have an outer diameter of 10mm to 100mm, preferably 50mm; and a length of 800mm to 2500mm, preferably 1000mm to 1800mm. The deposited powder body 200 may have an outer diameter of 150mm to 400mm, preferably 300mm to 380mm.

[0095] Specifically, the deposition of powder 200 on the cylindrical rod via chemical vapor deposition includes:

[0096] A deposition gas is introduced into at least one torch in the deposition chamber 610 to deposit powder 200 on a cylindrical rod; wherein the deposition gas includes hydrogen (H2), oxygen (O2), argon (Ar) and silicon tetrachloride (SiCl4).

[0097] Thus, by introducing hydrogen, oxygen, argon and silicon tetrachloride into at least one torch, a loose powder body 200 is deposited on a cylindrical rod.

[0098] Introducing deposition gas into at least one torch within the deposition chamber, including:

[0099] Deposition gas is introduced into the first blowtorch 620, the second blowtorch 630, the third blowtorch 640 and the fourth blowtorch 650, which are distributed sequentially and at intervals along the length of the cylindrical rod (i.e. the support member 100) in the deposition chamber 610.

[0100] Therefore, the powder 200 can be deposited in segments on the cylindrical rod by the first torch 620, the second torch 630, the third torch 640 and the fourth torch 650, which makes it easier to control the density of the powder 200 in different areas and improves the deposition efficiency.

[0101] For example, the density of the powder deposited at the first blowtorch 620 can be 0.15~1.5 g / cm³. 3 The preferred concentration is 0.25~0.35 g / cm³. 3 The density of the powder deposited at the second blowtorch 630, the third blowtorch 640, and the fourth blowtorch 650 is 0.15~1.5 g / cm³. 3 The preferred concentration is 0.28~0.38 g / cm³. 3 This results in the powder 200 having a better density distribution.

[0102] In some embodiments, deposition gas is introduced into the first blowtorch 620, the second blowtorch 630, the third blowtorch 640, and the fourth blowtorch 650, which are sequentially spaced along the length of the cylindrical rod in the deposition chamber 610. This may include:

[0103] The distance between the center point of the nozzle of the first blowtorch 620 and the center point of the nozzle of the second blowtorch 630 is set to be greater than or equal to 60 mm and less than or equal to 150 mm, preferably greater than or equal to 70 mm and less than or equal to 120 mm.

[0104] And / or, the distance between the line connecting the center point of the nozzle of the second torch 630 and the center point of the nozzle of the third torch 640 is set to be greater than or equal to 60 mm and less than or equal to 150 mm, preferably greater than or equal to 70 mm and less than or equal to 120 mm.

[0105] And / or, the distance between the line connecting the center point of the nozzle of the third torch 640 and the center point of the nozzle of the fourth torch 650 is set to be greater than or equal to 60 mm and less than or equal to 150 mm, preferably greater than or equal to 70 mm and less than or equal to 120 mm.

[0106] In this embodiment, the distance between the line connecting the center points of the nozzles of any two adjacent blowtorches in the first blowtorch 620, second blowtorch 630, third blowtorch 640 and fourth blowtorch 650, which are distributed at intervals in sequence, can be set to 60mm~150mm, preferably 70mm~120mm.

[0107] By rationally setting the distribution position of each torch, the corresponding deposition area of ​​the torch on the cylindrical rod can be rationally allocated, thereby optimizing the deposition effect.

[0108] In some embodiments, placing the cylindrical rod into the deposition chamber 610 includes:

[0109] One end of the cylindrical rod extending in the direction of extension is inserted into the base 660, and the cylindrical rod and the base 660 are simultaneously inserted into the connector 670 to fix the cylindrical rod on the base 660.

[0110] The cylindrical rod is placed into the sedimentation chamber 610 via the base 660.

[0111] Therefore, the cylindrical rod can be detachably connected to the base 660 via the connector 670 (the cylindrical rod is suspended on the base 660), making it easy to separate the cylindrical rod from the base 660 after deposition. The cylindrical rod can also be placed into the deposition chamber 610 by controlling the base 660, improving the convenience of controlling the cylindrical rod.

[0112] In summary, the method for preparing a bend-resistant optical fiber preform provided in this application involves immersing the part to be sintered in a low-refractive-index gas, allowing fluorine to penetrate relatively uniformly in both the axial and radial directions of the powder body 200, thereby improving the uniformity of fluorine distribution in the formed optical fiber preform. Fluorine also penetrates to the interface region between the outer surface of the core 300 and the inner surface of the hollow powder body 200, forming a fluorine-doped, uniformly recessed refractive index layer 400. The refractive index of the recessed layer 400 is significantly lower than that of the core layer, matching the refractive index of the cladding, thus creating a stable refractive index distribution and effectively reducing transmission loss during subsequent optical fiber use. By controlling the pressure during fusion sintering to less than or equal to 20 Pa, moisture in the part to be sintered is effectively removed, hydroxyl group formation is inhibited, and the hydroxyl content in the formed optical fiber preform is reduced, giving the optical fiber preform low-hydroxyl characteristics. Simultaneously, the generation of bubbles in the optical fiber preform is reduced, improving the quality of the optical fiber preform and the finished optical fiber. This solves the problem of poor quality of optical fiber preforms and finished optical fibers in related technologies.

[0113] The following examples, namely Example 1, Example 2, Comparative Example 1 and Comparative Example 2, further illustrate the method for preparing the bending-resistant optical fiber preform.

[0114] Example 1:

[0115] 1. Pretreatment of mandrel 300: Select a high-purity ultra-low loss mandrel with a diameter of 40mm and a length of 1800mm, place it in a 12% hydrofluoric acid solution for ultrasonic cleaning for 18min, rinse with 1.0L / min deionized water for 9min, and then place it in a drying oven at 135℃ for 2.5h.

[0116] 2. Powder 200 deposition: A specially made cylindrical rod with an outer diameter of 45 mm and a length of 1600 mm is suspended by a quartz spherical tail shank and a quartz connecting rod. Loose powder 200 is deposited on the cylindrical rod by a deposition device 600 and chemical vapor deposition. The specially made cylindrical rod is then removed to form a hollow powder 200.

[0117] 3. Sintering, dehydroxylation and fluorine doping: The combination of ultra-low loss mandrel 300 and hollow powder body 200 (i.e. the part to be sintered) is sent into sintering furnace 510. The absolute pressure of sintering furnace 510 is controlled within 20 Pa. The temperature is increased to 1100℃ at 6℃ / min and held for 2.5h. After the holding period, helium and 5% molar ratio CF4 (i.e. low refractive index gas) are introduced. The powder body 200 is immersed in the low refractive index gas for 2h and then the helium and low refractive index gas are turned off.

[0118] 4. Melt shrinkage molding: Re-control the pressure to within 20Pa, raise the temperature to 1600℃ at 4℃ / min, and sinter for 4h to shrink the diameter of the part to be sintered to 66mm to form an optical fiber preform.

[0119] 5. Post-cooling treatment: Cool to 400℃ for 30 minutes and remove the optical fiber preform;

[0120] After testing, such as Figure 7 As shown, the deep recess refractive index of this optical fiber preform is -0.22%, the radial refractive index change is <0.02%, and the bubble rate is 0.01%, which meets the processing requirements of ultra-low loss optical fiber preforms.

[0121] Comparative Example 1:

[0122] The difference from Example 1 is that, during the sintering dehydroxylation and fluorine doping process, the powder 200 was immersed in a low-refractive-index gas for 0.5 hours and then the helium and low-refractive-index gas were turned off. The other steps are the same as in Example 1.

[0123] After testing, such as Figure 8 As shown, the deep recess refractive index of this optical fiber preform is -0.14%, and the radial refractive index change is >0.2%, which does not meet the processing requirements for ultra-low loss optical fiber preforms.

[0124] Example 2:

[0125] 1. Pretreatment of core rod 300: Select a bend-insensitive fiber core rod 300 with a diameter of 60 mm and a length of 1800 mm, immerse it in a 12% hydrofluoric acid solution for ultrasonic cleaning for 18 min, rinse it with deionized water at a flow rate of 1.0 L / min for 9 min, and then place it in a drying oven at 135℃ for 2.5 h.

[0126] 2. Powder 200 deposition: A specially made cylindrical rod is suspended by a quartz spherical tail shank through a quartz connecting rod. The cylindrical rod has an outer diameter of 65 mm and a length of 1600 mm. Loose powder 200 is deposited on the cylindrical rod by chemical vapor deposition through a deposition device 600. The specially made cylindrical rod is then removed to form a hollow powder 200.

[0127] 3. Sintering, dehydroxylation and fluorine doping: The combination of special core rod 300 and hollow powder body 200 (i.e. the part to be sintered) is sent into sintering furnace 510. The absolute pressure inside the furnace is controlled within 10 Pa. The temperature is increased to 1100℃ at 6℃ / min and held for 3 hours. After the holding period, helium and CF4 (i.e. low refractive index gas) with a molar ratio of 12% are introduced. The powder body 200 is immersed in the low refractive index gas for 2 hours and then the helium and low refractive index gas are turned off.

[0128] 4. Melt shrinkage molding: The absolute pressure inside the furnace is controlled again to be below 20 Pa, and the temperature is increased to 1600℃ at 4℃ / min. Sintering is carried out for 4 hours to shrink the diameter of the part to be sintered to 94 mm, forming an optical fiber preform.

[0129] 5. Post-cooling treatment: Cool to 400℃ for 30 minutes and remove the optical fiber preform;

[0130] After testing, such as Figure 9 As shown, the deep recess refractive index of this optical fiber preform is -0.32%, the axial refractive index change is <0.02%, the bubble rate is 0.01%, and the fluorine doping hydroxyl group is <1ppm, which meets the processing requirements of bend-insensitive optical fiber preforms.

[0131] Comparative Example 2:

[0132] The difference from Example 2 is that the absolute pressure inside the sintering furnace 510 is atmospheric pressure during the sintering dehydroxylation and fluorine doping step. The remaining steps are the same as in Example 2.

[0133] Testing revealed that the deep recess refractive index of the optical fiber preform was -0.32%, the axial refractive index change was <0.02%, the bubble rate was 0.01%, and the fluorine doping hydroxyl group was >1ppm, which did not meet the processing requirements for attenuation of the bend-insensitive optical fiber 1383.

[0134] This application provides an optical fiber preform manufactured using the method for preparing a bend-resistant optical fiber preform described in any of the above embodiments. This allows the refractive index of the deep recess (i.e., the recessed layer 400) of the optical fiber preform to reach -0.1% to -0.45%, the hydroxyl content to be less than 0.1 ppm, and the bubble rate to be less than 0.01%. It also allows the axial refractive index fluctuation of the optical fiber preform to be ≤0.02%. Furthermore, it possesses superior bend resistance.

[0135] It should be noted that this optical fiber preform can be drawn into optical fibers or other glass fibers, and can also be used in special communication optical fibers, optical fiber sensing, laser transmission and other fields. Applicable scenarios include long-distance trunk communication, submarine optical cables, industrial sensor networks and so on.

[0136] The optical fiber provided in this application embodiment is made using the optical fiber preform in the above embodiment. The optical fiber has a low refractive index of -0.1% to -0.45%, a hydroxyl content of less than 0.1 ppm, a bubble rate of less than 0.01%, and an axial refractive index fluctuation of ≤0.02%. The low refractive index of the optical fiber refers to the refractive index when the refractive index distribution of the optical fiber is at its lowest point (that is, the refractive index of the depression layer 400).

[0137] It should be noted that existing fusion drawing equipment can be used to draw the optical fiber preform into finished optical fiber.

[0138] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing a bend-resistant optical fiber preform, characterized in that, Includes the following steps: Powder (200) is deposited on a carrier (100), and then the carrier (100) is removed from the powder (200) to form a hollow powder (200). A mandrel (300) is inserted into the hollow powder body (200) to form a part to be sintered; The part to be sintered is immersed in a low-refractive-index gas and sintered to form an optical fiber preform.

2. The method for preparing a bend-resistant optical fiber preform according to claim 1, characterized in that, The step of immersing the workpiece in a low-refractive-index gas and sintering it includes: The pressure during sintering is less than or equal to 20 Pa.

3. The method for preparing a bend-resistant optical fiber preform according to claim 2, characterized in that, The step of immersing the workpiece in a low-refractive-index gas and sintering it further includes: The workpiece to be sintered is placed in the sintering furnace (510), and the low refractive index gas is introduced into the sintering furnace (510) through the pipe (520) on the sintering furnace (510) so that the workpiece to be sintered undergoes a first dehydroxylation sintering, immersion in the low refractive index gas and a second melting sintering in the sintering furnace (510).

4. The method for preparing a bend-resistant optical fiber preform according to claim 3, characterized in that, The sintering pressure is less than or equal to 20 Pa, including: During the first dehydroxylation sintering and the second melting shrinkage sintering, the pressure inside the sintering furnace (510) is controlled to be less than or equal to 20 Pa by the pressure control device (530) on the sintering furnace (510).

5. The method for preparing a bend-resistant optical fiber preform according to claim 3, characterized in that, The process of subjecting the workpiece to be sintered to sequential dehydroxylation sintering, low-refractive-index gas immersion, and secondary melting-shrinkage sintering in the sintering furnace (510) includes: The workpiece to be sintered is subjected to the first dehydroxylation sintering in the sintering furnace (510); wherein the heating temperature is increased at 3~10℃ / min to greater than or equal to 800℃ and less than or equal to 1300℃, and the holding time is greater than or equal to 1h and less than or equal to 4~8h. The low-refractive-index gas is introduced into the sintering furnace (510), and the workpiece to be sintered after the first dehydroxylation sintering is immersed in the low-refractive-index gas in the sintering furnace; wherein the immersion temperature is greater than or equal to 800°C and less than or equal to 1300°C, the immersion time is greater than or equal to 0.5h and less than or equal to 6h, and the flow rate of the low-refractive-index gas is greater than or equal to 1L / min and less than or equal to 40L / min; Stop introducing the low-refractive-index gas into the sintering furnace (510), and perform the secondary melting and shrinkage sintering in the sintering furnace after the low-refractive-index gas has been soaked in the gas; wherein, the heating temperature is increased at 4℃ / min to greater than or equal to 1500℃ and less than or equal to 1800℃ to continue melting and shrinkage sintering, and the holding time is greater than or equal to 2h and less than or equal to 10h.

6. The method for preparing a bend-resistant optical fiber preform according to any one of claims 1-5, characterized in that, The deposition of powder (200) on the carrier (100) includes: A cylindrical rod is placed in a deposition chamber (610), and the powder (200) is deposited on the cylindrical rod by chemical vapor deposition; wherein the density of the powder (200) is greater than or equal to 0.15 g / cm³. 3 And less than or equal to 1.5 g / cm 3 .

7. The method for preparing a bend-resistant optical fiber preform according to claim 6, characterized in that, The deposition of the powder (200) on the cylindrical rod by chemical vapor deposition includes: A deposition gas is introduced into at least one torch in the deposition chamber (610) to deposit the powder (200) on the cylindrical rod; wherein the deposition gas includes hydrogen, oxygen, argon and silicon tetrachloride; And / or, the placement of the cylindrical rod into the deposition chamber (610) includes: One end of the cylindrical rod extending in the direction of extension is inserted into the base (660), and the cylindrical rod and the base (660) are simultaneously inserted using a connector (670) to fix the cylindrical rod onto the base (660); The cylindrical rod is placed into the deposition chamber (610) via the base (660).

8. The method for preparing a bend-resistant optical fiber preform according to claim 7, characterized in that, The process of introducing deposition gas into at least one torch within the deposition chamber (610) includes: The deposition gas is introduced into the first blowtorch (620), the second blowtorch (630), the third blowtorch (640) and the fourth blowtorch (650) that are distributed at intervals along the length of the cylindrical rod in the deposition chamber (610); The distance between the center point of the nozzle of the first blowtorch (620) and the center point of the nozzle of the second blowtorch (630) is set to be greater than or equal to 60 mm and less than or equal to 150 mm. And / or, the distance between the line connecting the center point of the nozzle of the second blowtorch (630) and the center point of the nozzle of the third blowtorch (640) is set between 60 mm and 150 mm. And / or, the distance between the line connecting the center point of the nozzle of the third torch (640) and the center point of the nozzle of the fourth torch (650) is set between 60 mm and 150 mm.

9. An optical fiber preform, characterized in that, It is prepared by the method for preparing bend-resistant optical fiber preforms according to any one of claims 1-8.

10. An optical fiber, characterized in that, The optical fiber is made using the optical fiber preform as described in claim 9, wherein the optical fiber has a low refractive index of -0.1% to -0.45%, a hydroxyl content of less than 0.1 ppm, a bubble rate of less than 0.01%, and an axial refractive index fluctuation of ≤0.02%.

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