Optical fiber preform sintering device and method

Abstract

The invention provides an optical fiber preform rod sintering device and method. The optical fiber preform rod sintering device comprises a metal shell, a furnace core pipe, a heat insulation layer, a heating body, a transmission device and a pipeline system, the furnace core pipe is arranged in the metal shell, the heat insulation layer is annularly arranged in the metal cavity, the heating body is annularly arranged on the side, facing the furnace core pipe, of the heat insulation layer in the length direction of the furnace core pipe, the transmission device is arranged on the outer side of the top of the metal shell, and the pipeline system is configured to introduce gas into and / or exhaust gas from the optical fiber preform sintering device. Wherein the transmission device is arranged at the top of the metal shell, and the transmission device comprises a hollow hanging rod; at least part of the hollow suspender extends into the reaction cavity and at least part of the hollow suspender is inserted into the optical fiber preform, and the pipeline system can introduce gas into the optical fiber preform through the hollow suspender. According to the optical fiber preform sintering device and method provided by the invention, the dopant can bidirectionally permeate from the center and the surface layer of the optical fiber preform, so that concentration distribution in various radial directions is realized.

Description

Technical Field

[0001] The present application relates to the field of optical fiber preform manufacturing, and in particular to an optical fiber preform sintering device and method. Background Art

[0002] Optical fiber preform is a quartz glass rod with a specific refractive index profile, which is a semi-finished product for manufacturing optical fiber. Optical fiber preform can be manufactured by vapor phase axial deposition method, in which loose silica powder is deposited on a quartz target rod by hydrolysis, and then the silica powder is sintered at high temperature to form a transparent optical fiber preform. In order to meet specific optical properties, some preforms need to be doped with dopants in the cladding area of ​​the optical fiber preform during the sintering process. During the sintering process, the dopant usually wraps the optical fiber preform in the form of a gas compound and diffuses in the cladding area.

[0003] In the prior art, the diffusion process of the dopant is generally controlled by controlling the uniformity of the heating field, the stability of the gas environment, the density of the powder body, and increasing the immersion time.

[0004] However, it is difficult to control the concentration distribution of the dopant diffused radially along the optical fiber preform by the above technology. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides an optical fiber preform sintering device and method, which can make the dopant penetrate from the center and surface of the optical fiber preform in both directions to achieve a variety of radial concentration distributions.

[0006] The present application provides an optical fiber preform sintering device and method, the optical fiber preform sintering device comprises a metal shell, a furnace core tube, a heat insulation layer, a heating body, a transmission device and a pipeline system; the furnace core tube is arranged inside the metal shell, the furnace core tube divides the internal space of the metal shell into a reaction cavity and a metal cavity, the reaction cavity is configured to accommodate the optical fiber preform, the heat insulation layer is arranged around the metal cavity, the heating body is arranged around the side of the heat insulation layer facing the furnace core tube along the length direction of the furnace core tube, the transmission device is arranged on the outside of the top of the metal shell, and the pipeline system is configured to introduce and / or exhaust gas into the optical fiber preform sintering device.

[0007] The transmission device is arranged on the top of the metal shell, and the transmission device includes a hollow hanger; the hollow hanger at least partially extends to the reaction cavity and is at least partially inserted into the optical fiber preform rod, and the pipeline system can pass gas into the optical fiber preform rod through the hollow hanger.

[0008] The optical fiber preform sintering device provided in the present application includes a reaction cavity and a metal cavity. High-pressure gas is introduced into the reaction cavity and the metal cavity simultaneously through a pipeline system and the pressure difference between the inside and outside of the furnace core tube is controlled within a certain range. This can accelerate the diffusion speed of the dopant in the optical fiber preform and prevent the furnace core tube from rupturing under the action of the high-pressure gas. The dopant gas can be introduced into the center of the optical fiber preform and the reaction cavity at the same time, and penetrate from the center and surface of the optical fiber preform in both directions, so that the radial distribution is more uniform. By controlling the pressure difference between the center and surface of the optical fiber preform, different concentration distributions of the dopant can be achieved.

[0009] As an optional embodiment, the optical fiber preform sintering device provided in the present application also includes a cracking furnace, which is configured to pretreat the dopant gas; the cracking furnace is connected to the pipeline system, and the cracking furnace is configured to transport the cracked dopant ions to the reaction chamber and the hollow hanger through the pipeline system.

[0010] With such an arrangement, the cracking furnace can pre-crackle the dopant, thereby accelerating the reaction rate between the dopant and the optical fiber preform.

[0011] As an optional embodiment, the optical fiber preform sintering device provided in the present application, the pipeline system includes a first pipeline, a second pipeline, a third pipeline and a fourth pipeline, the first pipeline is configured to pass through the metal shell and communicate with the reaction chamber, the second pipeline is configured to communicate with the metal cavity, the third pipeline is configured to communicate with the hollow hanger, and the fourth pipeline is configured to communicate with the reaction chamber.

[0012] With such an arrangement, gas can be introduced into the reaction cavity, the metal cavity and the center of the optical fiber preform rod at the same time, thereby ensuring the stability of the device and controlling the concentration distribution of the dopant along the radial direction.

[0013] As an optional embodiment, the optical fiber preform sintering device provided in the present application comprises a metal shell including a metal shell upper cover, a thermal insulation layer is arranged on the lower side of the metal shell upper cover, a hollow hanger penetrates the metal shell upper cover and the thermal insulation layer and at least partially extends to the reaction chamber, and a sealing structure is arranged at the connection between the hollow hanger and the metal shell upper cover, and the sealing structure is configured to seal the gap between the hollow hanger and the metal shell upper cover.

[0014] Such an arrangement can ensure the airtightness of the device.

[0015] As an optional embodiment, the optical fiber preform sintering device provided in the present application has a supporting structure arranged inside the metal shell, the supporting structure is configured to support the furnace core tube, the supporting structure is provided with at least one connecting hole, the connecting hole is used to connect the reaction cavity and the metal cavity, and the connecting hole is configured to be openable or closed.

[0016] With such arrangement, the reaction chamber and the metal chamber can be connected through the connecting hole, and the gas pressure of the reaction chamber and the metal chamber can be balanced under certain conditions.

[0017] As an optional embodiment, the optical fiber preform sintering device provided in the present application has an open top of the furnace core tube, a supporting structure, a metal shell upper cover and side walls form a top space, and the top space and the inner cavity of the furnace core tube together constitute a reaction chamber; a fourth pipe is connected to the top space.

[0018] Such an arrangement can facilitate the placement of the optical fiber preform in the furnace core tube, and the fourth pipe can discharge the gas with a lower density in the reaction cavity.

[0019] As an optional embodiment, in the optical fiber preform sintering device provided in the present application, the first pipeline, the second pipeline, the third pipeline and the fourth pipeline are provided with a pressure regulating device, the pressure regulating device includes an air pump and a control valve, and the air pump is used to introduce and / or extract gas into the reaction chamber, the metal cavity and the hollow hanger.

[0020] With such an arrangement, the air pressure in the reaction cavity, the metal cavity and the center of the optical fiber preform can be adjusted to ensure the stability of the device.

[0021] As an optional embodiment, in the optical fiber preform sintering device provided in the present application, the reaction cavity and the hollow suspension rod are provided with at least one pressure monitoring device, and the metal cavity is provided with multiple pressure monitoring devices along the height direction.

[0022] With such an arrangement, the air pressure in the reaction cavity, the metal cavity and the center of the optical fiber preform can be monitored to ensure that the air pressure is within a preset range.

[0023] As an optional embodiment, in the optical fiber preform sintering device provided in the present application, a water cooling device is provided on the outside of the metal shell, and the water cooling device is configured to control the temperature of the metal shell.

[0024] Such an arrangement can limit the temperature of the metal shell and ensure the safety of the manufacturing process.

[0025] The present application provides a method for sintering an optical fiber preform, which is used in the above-mentioned optical fiber preform sintering device, and the method comprises:

[0026] The fiber preform powder is fed into the reaction chamber, the hollow suspension rod is inserted into the fiber preform and fixed, the upper cover of the metal shell is closed, and the preform is heated to a set temperature by a heating element;

[0027] An oxidizing gas is introduced into the reaction chamber and the hollow suspension rod through an air pump, and a protective gas is introduced into the metal chamber, the pressure difference between the hollow suspension rod and the reaction chamber, and between the reaction chamber and the metal chamber is adjusted within a certain range, and the pressurization is stopped after the pressure in the furnace core tube reaches a first preset value;

[0028] The target gas is introduced into the reaction chamber, the metal chamber and the hollow suspension rod at the same time, the pressure difference between the hollow suspension rod and the reaction chamber, and between the reaction chamber and the metal chamber is adjusted within a certain range, and the pressurization is stopped after the pressure in the furnace core tube reaches a second preset value;

[0029] Depressurizing the hollow suspension rod, the reaction chamber, and the metal chamber, maintaining the pressure difference between the hollow suspension rod and the reaction chamber, and between the reaction chamber and the metal chamber within a certain range, and stopping the pressure relief after the pressure in the furnace core tube reaches a third preset value;

[0030] The temperature is raised to the set temperature by the heating element until sintering is completed.

[0031] The present application provides an optical fiber preform sintering method, which can be used in the above-mentioned optical fiber preform sintering device to achieve different concentration distributions of dopants along the radial direction.

[0032] The present application provides an optical fiber preform sintering device and method, including a metal shell, a furnace core tube, a heat insulation layer, a heating body, a transmission device and a pipeline system; the furnace core tube is arranged inside the metal shell, and the furnace core tube divides the internal space of the metal shell into a reaction cavity and a metal cavity, the reaction cavity is configured to accommodate the optical fiber preform, the heat insulation layer is arranged around the metal cavity, the heating body is arranged around the side of the heat insulation layer facing the furnace core tube along the length direction of the furnace core tube, the transmission device is arranged outside the top of the metal shell, and the pipeline system is configured to introduce and / or exhaust gas to the optical fiber preform sintering device. Among them, the transmission device is arranged on the top of the metal shell, and the transmission device includes a hollow suspension rod; the hollow suspension rod at least partially extends to the reaction cavity and is at least partially inserted into the interior of the optical fiber preform, and the pipeline system can introduce gas into the interior of the optical fiber preform through the hollow suspension rod. The optical fiber preform sintering device and method provided by the present application can make the dopant penetrate from the center and surface of the optical fiber preform in both directions to achieve a variety of radial concentration distributions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A schematic diagram of an optical fiber preform sintering device provided in an embodiment of the present application;

[0035] Figure 2 A schematic diagram of the refractive index of the final cross section provided in Example 1 of the present application;

[0036] Figure 3 A schematic diagram of the refractive index of the final cross section provided in Example 2 of the present application;

[0037] Figure 4 A schematic diagram of the refractive index of the final cross section provided in Example 3 of the present application.

[0038] In the figure:

[0039] 100-metal shell; 110-furnace core tube; 120-insulation layer; 130-heating body; 140-transmission device; 141-hollow suspension rod; 150-cracking furnace; 160-pipeline system; 161-first pipeline; 162-second pipeline; 163-third pipeline; 164-fourth pipeline; 170-metal shell cover; 180-insulation layer; 190-sealing structure; 200-supporting structure; 201-connecting hole; 202-switch; 210-reaction chamber; 211-top space; 220-metal chamber; 230-pressure regulating device; 231-air pump; 232-control valve; 240-pressure monitoring device. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0041] The terms "first", "second", "third", "fourth", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances. For example, without departing from the scope of this document, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information.

[0042] The word "if" as used herein may be interpreted as "when" or "when" or "in response to determining," depending on the context.

[0043] In general, terms should be understood, at least in part, by the context in which they are used. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "a," "an," or "the" may also be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context.

[0044] It should be easily understood that the terms “on,” “above,” and “over” in this application should be interpreted in the broadest manner, so that “on” means not only “directly on something,” but also includes the meaning of “on something” with intervening features or layers therebetween, and “above” or “over” includes not only the meaning of “above something” or “over,” but also may include the meaning of “above something” or “over” with no intervening features or layers therebetween (i.e., directly on something).

[0045] In addition, spatially relative terms, such as "below," "below," "beneath," "above," "above," etc., may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may have other orientations (rotated 90° or at other orientations), and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0046] It should be further understood that the terms “comprises” and “includes” indicate the existence of features, steps, operations, elements, components, items, types, and / or groups, but do not exclude the existence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, types, and / or groups.

[0047] The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Thus, "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". An exception to this definition will only occur when a combination of elements, functions, steps or operations are inherently mutually exclusive in some manner.

[0048] Optical fiber preform is a quartz glass rod with a specific refractive index profile and is a semi-finished product for manufacturing optical fiber. Optical fiber preform can be manufactured by VAD (vapor axial deposition) process. The manufacturing process is as follows: first, loose silica powder is deposited on the quartz target rod by hydrolysis, and then the silica powder is sintered at high temperature to form a transparent optical fiber preform. Among them, the sintering process is mainly divided into two steps: dehydration and vitrification. The powder body is placed in a high-temperature environment. During this period, different gases are introduced in stages to carry out various physical and chemical reactions, and finally the hydroxyl groups in the powder body are filtered out and made into a transparent quartz rod. In order to meet specific optical properties, some preforms need to be doped with dopants in the cladding area of ​​the optical fiber preform during the sintering process. The dopants usually wrap the outer surface of the powder body in the form of gas compounds and are doped into the cladding area from the outside to the inside in a free diffusion manner. However, when the dopant diffuses in the optical fiber preform, the surface concentration is always high and the center concentration is low, and the concentration distribution is difficult to control.

[0049] In the prior art, the diffusion process of the dopant is generally controlled by controlling the uniformity of the heating field, the stability of the gas environment, the density of the powder body, and increasing the immersion time.

[0050] However, by controlling the uniformity of the heating field and the stability of the gas environment, only the axial uniformity can be improved, but the radial uniformity cannot be improved; by controlling the radial density of the optical fiber preform, the diffusion rate of the inner layer can be accelerated and the doping difference between the inner and outer layers can be reduced, but this technology has very high requirements on the production technology of the powder body and limits the diameter of the powder body; increasing the immersion time will sacrifice production efficiency.

[0051] In response to the above technical problems, the present application provides an optical fiber preform sintering device and method, which can enable dopants to bidirectionally penetrate from the center and surface of the optical fiber preform to achieve a variety of radial concentration distributions.

[0052] The present application provides an optical fiber preform sintering device and method, such as Figure 1 The optical fiber preform sintering device includes a metal shell 100, a furnace core tube 110, an insulation layer 120, a heating body 130, a transmission device 140 and a pipeline system 160; the furnace core tube 110 is arranged inside the metal shell 100, and the furnace core tube 110 divides the internal space of the metal shell 100 into a reaction cavity 210 and a metal cavity 220, and the reaction cavity 210 is configured to accommodate the optical fiber preform, the insulation layer 120 is arranged around the metal cavity 220, the heating body 130 is arranged along the length direction of the furnace core tube 110 on the side of the insulation layer 120 facing the furnace core tube 110, the transmission device 140 is arranged on the outside of the top of the metal shell 100, and the pipeline system 160 is configured to introduce and / or exhaust gas into the optical fiber preform sintering device.

[0053] Among them, the transmission device 140 is arranged on the top of the metal shell 100, and the transmission device 140 includes a hollow hanger 141; the hollow hanger 141 at least partially extends to the reaction chamber 210, and is at least partially inserted into the optical fiber preform rod, and the pipeline system 160 can pass gas into the optical fiber preform rod through the hollow hanger 141.

[0054] It can be understood that the metal shell 100 is used as the shell of the entire device to accommodate and connect different components. The metal shell 100 can be set to a double-layer structure, which can play a certain role in heat insulation. The furnace core tube 110 is used as a container for accommodating the optical fiber preform rod, and the internal space of the metal shell 100 is divided into a reaction cavity 210 and a metal cavity 220. The sintering reaction of the optical fiber preform rod is carried out in the reaction cavity 210. The heat insulation layer 120 is annularly arranged in the metal cavity 220, which can be arranged between the metal shell 100 and the furnace core tube 110, and can also be arranged in close contact with the metal shell 100, so as to isolate the heating body 130 from the metal shell 100. To prevent the metal shell 100 from being overheated, the heating body 130 is annularly arranged on the insulation layer 120, facing the side of the furnace core tube 110, and its height is consistent with or longer than the optical fiber preform rod, and is used to provide a high-temperature environment for sintering the optical fiber preform rod. The transmission device 140 includes a hollow suspension rod 141, and one end of the hollow suspension rod 141 extending into the furnace core tube 110 is provided with a connecting sleeve, and the connecting sleeve is used to fix the optical fiber preform rod on the hollow suspension rod 141. The transmission device 140 is used to drive the optical fiber preform rod to rotate along the axis so that the optical fiber preform rod is heated evenly. The pipeline system 160 is used to introduce or exhaust gas to different parts inside the device.

[0055] Optionally, the material of the metal shell 100 may be a corrosion-resistant metal such as copper or stainless steel, the furnace core tube 110 may be a quartz furnace core tube 110, and the heat insulation layer 120 may be a graphite layer.

[0056] As an optional embodiment, the optical fiber preform sintering device provided in the present application also includes a cracking furnace 150, which is configured to pretreat the dopant gas; the cracking furnace 150 is connected to the pipeline system 160, and the cracking furnace 150 is configured to transport the cracked dopant ions to the reaction chamber 210 and the hollow hanger 141 respectively through the pipeline system 160.

[0057] It can be understood that the cracking furnace 150 is used to crack the dopant gas, and the dopant can be CF4, SiF4 or SiCl4. The F and Cl elements in the dopant can change the refractive index of the optical fiber preform. The cracked dopant ions are introduced into the reaction cavity 210 and the center of the optical fiber preform through the first pipe 161 and the third pipe 163 respectively, and the concentration distribution of the dopant diffused radially along the optical fiber preform is improved and controlled by double penetration, so as to prevent the situation that the dopant concentration on the surface of the optical fiber preform is high and the concentration in the center is low.

[0058] As an optional embodiment, the optical fiber preform sintering device provided in the present application, the pipeline system 160 includes a first pipeline 161, a second pipeline 162, a third pipeline 163 and a fourth pipeline 164, the first pipeline 161 is configured to pass through the metal shell 100 and communicate with the reaction chamber 210, the second pipeline 162 is configured to communicate with the metal cavity 220, the third pipeline 163 is configured to communicate with the hollow hanger 141, and the fourth pipeline 164 is configured to communicate with the reaction chamber 210.

[0059] It can be understood that the internal pipeline of the hollow hanger 141 is connected to the center of the optical fiber preform rod, and the first pipeline 161, the second pipeline 162, and the third pipeline 163 can respectively introduce or exhaust gas into or from the reaction cavity 210, the metal cavity 220, and the center of the optical fiber preform rod. The first pipeline 161 can be connected to the bottom of the reaction cavity 210, the second pipeline 162 can be connected to the top of the metal cavity 220, the third pipeline 163 is connected to the center of the optical fiber preform rod through the hollow hanger 141, and the fourth pipeline 164 can be connected to the top of the reaction cavity 210. When exhausting gas, due to the complex gas composition of the reaction cavity 210, gases of different densities can be discharged separately from the first pipeline 161 and the second pipeline 162, wherein, when the first pipeline 161 is connected to the bottom of the reaction cavity 210, high-density gas is more easily discharged from the first pipeline 161.

[0060] As an optional embodiment, the optical fiber preform sintering device provided in the present application, the metal shell 100 includes a metal shell upper cover 170, an insulation layer 180 is arranged on the lower side of the metal shell upper cover 170, the hollow hanger 141 passes through the metal shell upper cover 170 and the insulation layer 180 and at least partially extends to the reaction chamber 210, and a sealing structure 190 is arranged at the connection between the hollow hanger 141 and the metal shell upper cover 170, and the sealing structure 190 is configured to seal the gap between the hollow hanger 141 and the metal shell upper cover 170.

[0061] It can be understood that the metal shell upper cover 170 can be opened to place the optical fiber preform rod, or closed to carry out the sintering process. An insulation layer 180 is arranged on the lower side of the metal shell upper cover 170. The insulation layer 180 covers the metal shell upper cover 170 and the side wall between the metal shell upper cover 170 and the supporting structure 200 for heat insulation and corrosion protection. The insulation layer 180 material can be graphite or other high temperature resistant and corrosion resistant materials. The sealing structure 190 can be a metal seal, a graphite seal, a ceramic seal or other high temperature resistant and corrosion resistant seal to prevent the gas or heat in the reaction chamber 210 from leaking out through the gap between the hollow suspension rod 141 and the metal shell upper cover 170.

[0062] As an optional embodiment, the optical fiber preform sintering device provided in the present application has a supporting structure 200 disposed inside the metal shell 100, and the supporting structure 200 is configured to support the furnace core tube 110. The supporting structure 200 is provided with at least one connecting hole 201, and the connecting hole 201 is used to connect the reaction cavity 210 and the metal cavity 220, and the connecting hole 201 is configured to be openable or closed.

[0063] It can be understood that the supporting structure 200 is annularly arranged on the top of the metal shell 100 and is connected to the metal shell 100. The top outer edge of the furnace core tube 110 overlaps the supporting structure 200, and the bottom is suspended. The material of the supporting structure 200 can be graphite, or other high temperature resistant and corrosion resistant materials; the number of connecting holes 201 can be two, which are symmetrically arranged along the axis of the furnace core tube. The connecting holes 201 are in a closed state during the sintering process of the optical fiber preform rod, and can be opened in specific scenarios.

[0064] For example, during the debugging of the device, the same gas is introduced into the reaction chamber 210 and the metal chamber 220 . At this time, the connecting hole 201 can be opened to balance the gas pressure of the reaction chamber 210 and the metal chamber 220 .

[0065] As an optional embodiment, the optical fiber preform sintering device provided in the present application has an open top of the furnace core tube 110, and the supporting structure 200, the metal shell upper cover 170 and the side walls are arranged to form a top space 211, and the top space 211 and the inner cavity of the furnace core tube 110 together constitute a reaction chamber 210; the fourth pipe 164 is connected to the top space 211.

[0066] It can be understood that after the tube mouth of the furnace core tube 110 is opened, the internal space of the furnace core tube 110 and the top space 211 of the metal shell 100 are connected, and together they constitute the reaction chamber 210. A non-completely sealed sealing cover can be provided at the tube mouth of the furnace core tube 110 to prevent debris and dust from falling into the furnace core tube 110. The fourth pipe 164 is connected to the top space 211 of the metal shell 100, and can be used to discharge the gas from the reaction chamber 210, wherein the gas with low density is more easily discharged from the fourth pipe 164.

[0067] As an optional embodiment, in the optical fiber preform sintering device provided in the present application, the first pipeline 161, the second pipeline 162, the third pipeline 163 and the fourth pipeline 164 are provided with a pressure regulating device 230, and the pressure regulating device 230 includes an air pump 231 and a control valve 232. The air pump 231 is used to introduce and / or extract gas into the reaction chamber 210, the metal cavity 220 and the hollow suspension rod 141.

[0068] It is understandable that during the sintering process, high-pressure gas can be pumped into the reaction cavity 210 and the metal cavity 220 through the air pump 231 at the same time to increase the diffusion rate of the dopant, and the pressure difference on both sides of the furnace core tube 110 can be controlled within a certain range to prevent the furnace core tube 110 from breaking under a high-pressure environment; by controlling the pressure difference between the reaction cavity 210 and the center of the optical fiber preform rod through the air pump 231, the diffusion direction of the dopant can be controlled to achieve different concentration distributions.

[0069] The pressure regulating device 230 may also include a buffer tank and a high-pressure gas storage tank to prevent excessive fluctuations in the internal air pressure of the device.

[0070] In some possible scenarios, the air pump 231 can also extract the gas in the device to make the inside of the device a negative pressure or vacuum state.

[0071] As an optional embodiment, in the optical fiber preform sintering device provided in the present application, the reaction cavity 210 and the hollow suspension rod 141 are provided with at least one pressure monitoring device 240, and the metal cavity 220 is provided with multiple pressure monitoring devices 240 along the height direction.

[0072] Optionally, the pressure monitoring device 240 can be a pressure gauge, which is used to cooperate with the pressure regulating device 230 to adjust the air pressure in the center of the reaction cavity 210, the metal cavity 220 and the optical fiber preform rod, wherein the pressure gauges used to monitor the center of the reaction cavity 210 and the optical fiber preform rod are connected to the first pipe 161 and the third pipe 163 respectively, and there can be multiple pressure gauges used to monitor the metal cavity 220, which are arranged at different heights along the side wall of the metal shell 100 to monitor the air pressure at different heights of the metal cavity 220.

[0073] As an optional embodiment, in the optical fiber preform sintering device provided in the present application, a water cooling device is provided on the outside of the metal shell 100 , and the water cooling device is configured to control the temperature of the metal shell 100 .

[0074] It can be understood that the thermal insulation layer 180 and the heat insulating layer 120 can limit the upper temperature limit of the metal shell 100, but the high-temperature air in the metal cavity 220 is still in contact with the metal shell 100, causing the metal shell 100 to heat up. Adding a water cooling device can further reduce the temperature of the metal shell 100 and increase safety. The water cooling device can be set on the outside of the metal shell 100 or between the double-layer structure of the metal shell 100.

[0075] The present application provides a method for sintering an optical fiber preform, which is used in the above-mentioned optical fiber preform sintering device, and the method comprises:

[0076] The optical fiber preform powder is fed into the reaction chamber 210, the hollow suspension rod 141 is inserted into the optical fiber preform and fixed, the metal shell upper cover 170 is closed, and the preform is heated to a set temperature by a heating element.

[0077] An oxidizing gas is introduced into the reaction chamber 210 and the hollow suspension rod 141 through the air pump 231, and a protective gas is introduced into the metal chamber 220. The pressure difference between the hollow suspension rod 141 and the reaction chamber 210, and between the reaction chamber 210 and the metal chamber 220 is adjusted within a certain range, and the pressurization is stopped after the pressure in the furnace core tube 110 reaches a first preset value.

[0078] The target gas is introduced into the reaction chamber 210, the metal chamber 220 and the hollow suspension rod 141 at the same time, the pressure difference between the hollow suspension rod 141 and the reaction chamber 210, and between the reaction chamber 210 and the metal chamber 220 is adjusted within a certain range, and the pressurization is stopped after the pressure in the furnace core tube 110 reaches a second preset value.

[0079] The hollow suspension rod 141, the reaction chamber 210 and the metal chamber 220 are depressurized to maintain the pressure difference between the hollow suspension rod 141 and the reaction chamber 210, and between the reaction chamber 210 and the metal chamber 220 within a certain range, and the depressurization is stopped after the pressure in the furnace core tube 110 reaches a third preset value.

[0080] The temperature is raised to the set temperature by the heating element until sintering is completed.

[0081] Several specific embodiments are provided below, and different embodiments correspond to sintering methods for optical fiber preforms with different refractive indices.

[0082] Embodiment 1:

[0083] S1: Deposition of high-density silica powder on a coreless target rod by hydrolysis reaction.

[0084] S2: The powder is placed in a sintering furnace, the furnace is sealed, and the heating body 130 is turned on to raise the temperature to 600°C to 900°C.

[0085] S3: Pump oxygen into the reaction chamber 210 through the first pipe 161, and pump nitrogen into the metal chamber 220 through the second pipe 162, keep the pressure difference between the inside and outside of the furnace core tube 110 less than 0.05Mpa, and stop the air pump 231 after the pressure in the furnace core tube 110 reaches 5Mp~8Mpa.

[0086] S4: Open the cracking furnace 150, introduce CF4 into the furnace core tube 110 through the first pipeline 161, and simultaneously continue to pump nitrogen into the metal cavity 220, while still maintaining the pressure difference between the inside and outside of the furnace core tube 110 less than 0.05Mpa, and stop the air pump 231 after the pressure in the furnace core tube 110 reaches 6Mpa~10Mpa.

[0087] S5: Maintain the above atmosphere for 20 minutes, then gradually open the control valve 232 to release the pressure, and maintain the pressure difference between the inside and outside of the furnace core tube 110 less than 0.05 MPa until the pressure inside the furnace core tube 110 drops to 1 MPa.

[0088] S6: Raise the temperature of the heating body 130 to 1350° C. to complete sintering.

[0089] The refractive index δ1 of the final profile is between -0.05% and -0.40%, and δ2 is between -0.07% and -0.40%. The difference between δ1 and δ2 is less than 0.02%, where δ1 represents the refractive index of the core layer of the optical fiber preform, and δ2 represents the refractive index of the cladding region of the optical fiber preform. The refractive index distribution is as follows: Figure 2 shown.

[0090] Embodiment 2:

[0091] S1: Deposit high-density silica powder on the ceramic target rod through hydrolysis reaction, requiring the ceramic rod to be completely wrapped at the end and the ceramic rod to be pulled out after the deposition is completed.

[0092] S2: The powder is placed in a sintering furnace, and the metal shell upper cover 170 is closed. The heating body 130 is turned on to raise the temperature to 600° C. to 900° C.

[0093] S3: Chlorine is pumped into the reaction chamber 210 through the first pipe 161, nitrogen is pumped into the metal chamber 220 through the second pipe 162, and oxygen is pumped into the powder body through the third pipe 163, the pressure difference between the inside and outside of the furnace core tube 110 is kept less than 0.05Mpa, the pressure difference between the inside and outside of the powder body is kept less than 0.05Mpa, and the air pump 231 is stopped after the pressure in the furnace core tube 110 reaches 3Mp~4Mpa.

[0094] S4: SiCl4 is introduced into the furnace core tube 110 through the first pipeline 161, and nitrogen and chlorine in the furnace core tube 110 are simultaneously pumped into the metal cavity 220 to ensure that the pressure difference between the inside and outside of the furnace core tube 110 is less than 0.05Mpa, and the pressure difference between the inside and outside of the powder body is +0.02Mpa~+0.04Mpa, and the air pump 231 is stopped after the pressure in the furnace core tube 110 reaches 4Mpa~5Mpa.

[0095] S5: Maintain the above atmosphere for 30 minutes, then gradually open the control valve 232 to release the pressure, keep the pressure difference between the inside and outside of the furnace core tube 110 less than 0.05 MPa, and keep the pressure difference between the inside and outside of the powder less than 0.05 MPa, until the pressure inside the furnace core tube 110 drops to 1 MPa.

[0096] S6: Raise the temperature of the heating body 130 to 1350° C. to complete sintering.

[0097] S7: The hollow part of the powder body is evacuated through the suspension rod to achieve a vacuum state, and then the quartz rod is lifted up and then gradually lowered through a high temperature zone of 1450°C, so that the hollow core rod collapses into a solid rod.

[0098] The refractive index δ1 of the final profile is between +0.15% and +0.30%, and l1 can reach 15 cm to 60 cm, where δ1 represents the refractive index of the core layer of the optical fiber preform, and l1 represents the thickness of the core layer of the optical fiber preform. The refractive index distribution is as follows: Figure 3 shown.

[0099] Embodiment 3:

[0100] S1: Deposit high-density silica powder on the ceramic target rod through hydrolysis reaction, requiring the ceramic rod to be completely wrapped at the end and the ceramic rod to be pulled out after the deposition is completed.

[0101] S2: The powder is placed in a sintering furnace, and the metal shell upper cover 170 is closed. The heating body 130 is turned on to raise the temperature to 600° C. to 900° C.

[0102] S3: Chlorine is pumped into the reaction chamber 210 through the first pipe 161, nitrogen is pumped into the metal chamber 220 through the second pipe 162, and oxygen is pumped into the powder body through the third pipe 163, the pressure difference between the inside and outside of the furnace core tube 110 is kept less than 0.05Mpa, the pressure difference between the inside and outside of the powder body is kept less than 0.05Mpa, and the air pump 231 is stopped after the pressure in the furnace core tube 110 reaches 3Mp~4Mpa.

[0103] S4: SiCl4 is introduced into the furnace core tube 110 through the first pipe 161, and the nitrogen in the metal cavity 220 and the chlorine in the furnace core tube 110 are simultaneously opened to ensure that the pressure difference between the inside and outside of the furnace core tube 110 is less than 0.05Mpa, and the pressure difference between the inside and outside of the powder body is +0.02Mpa~+0.04Mpa, and the air pump 231 is stopped after the pressure in the furnace core tube 110 reaches 4Mpa~5Mpa.

[0104] S5: Maintain the above atmosphere for 30 minutes, then gradually open the control valve 232 of the third pipeline 163 to release the pressure, so that the internal and external pressure difference of the powder body is less than 0.01Mpa, and then introduce CF4 into the furnace core tube 110 until the internal and external pressure difference of the powder body is -0.02Mpa~-0.04Mpa, and maintain the above atmosphere for 15 minutes.

[0105] S6: Open all control valves 232 to release pressure, keep the pressure difference between the furnace core tube 110 and the powder less than 0.05 MPa, until the pressure in the reaction chamber 210 drops to 1 MPa.

[0106] S6: Raise the temperature of the heating body 130 to 1350° C. to complete sintering.

[0107] S7: The hollow part of the powder body is evacuated through the suspension rod to achieve a vacuum state, and then the quartz rod is lifted up and then gradually lowered through a high temperature zone of 1450°C, so that the hollow core rod collapses into a solid rod.

[0108] The refractive index δ1 of the final profile is between +0.15% and +0.30%, and δ2 is between -0.05% and +0.25%, where δ1 represents the refractive index of the core layer of the optical fiber preform, and δ2 represents the refractive index of the cladding region of the optical fiber preform. The refractive index distribution is as follows: Figure 4 shown.

[0109] The present application provides an optical fiber preform sintering device and method, comprising a metal shell 100, a furnace tube 110, an insulation layer 120, a heating body 130, a transmission device 140 and a pipeline system 160; the furnace tube 110 is arranged inside the metal shell 100, the insulation layer 120 is arranged around the metal cavity 220, the heating body 130 is arranged around the insulation layer 120 along the length direction of the furnace tube 110 and on the side of the furnace tube 110 facing the furnace tube 110, the transmission device 140 is arranged outside the top of the metal shell 100, and the pipeline system 160 is configured to pass gas into and / or exhaust gas from the optical fiber preform sintering device. Among them, the transmission device 140 is arranged at the top of the metal shell 100, and the transmission device 140 includes a hollow suspension rod 141; the hollow suspension rod 141 at least partially extends to the reaction cavity 210, and is at least partially inserted into the optical fiber preform, and the pipeline system 160 can pass gas into the optical fiber preform through the hollow suspension rod 141. The optical fiber preform sintering device and method provided in the present application can allow the dopant to bidirectionally penetrate from the center and the surface of the optical fiber preform, thereby achieving concentration distributions in various radial directions.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An optical fiber preform sintering device, characterized in that: The invention comprises a metal shell (100), a furnace core tube (110), a heat insulation layer (120), a heating body (130), a transmission device (140) and a pipeline system (160); the furnace core tube (110) is arranged inside the metal shell (100); the furnace core tube (110) divides the internal space of the metal shell (100) into a reaction cavity (210) and a metal cavity (220); the reaction cavity (210) is configured to accommodate an optical fiber preform; the heat insulation layer (120) is arranged around the metal cavity (220); the heating body (130) is arranged around the side of the heat insulation layer (120) facing the furnace core tube (110) along the length direction of the furnace core tube (110); the transmission device (140) is arranged outside the top of the metal shell (100); and the pipeline system (160) is configured to introduce and / or exhaust gas into the optical fiber preform sintering device; The transmission device (140) is arranged on the top of the metal shell (100), and the transmission device (140) comprises a hollow suspension rod (141); the hollow suspension rod (141) at least partially extends to the reaction chamber (210) and is at least partially inserted into the interior of the optical fiber preform, and the pipeline system (160) can pass gas into the interior of the optical fiber preform through the hollow suspension rod (141).

2. The optical fiber preform sintering device according to claim 1, characterized in that: It also includes a cracking furnace (150), wherein the cracking furnace (150) is configured to pre-treat the dopant gas; the cracking furnace (150) is connected to the pipeline system (160), and the cracking furnace (150) is configured to transport cracked dopant ions to the reaction chamber (210) and the hollow suspension rod (141) respectively through the pipeline system (160).

3. The optical fiber preform sintering device according to claim 2, characterized in that: The pipeline system (160) includes a first pipeline (161), a second pipeline (162), a third pipeline (163) and a fourth pipeline (164), wherein the first pipeline (161) is configured to pass through the metal shell (100) and communicate with the reaction chamber (210), the second pipeline (162) is configured to communicate with the metal chamber (220), the third pipeline (163) is configured to communicate with the hollow hanger (141), and the fourth pipeline (164) is configured to communicate with the reaction chamber (210).

4. The optical fiber preform sintering device according to claim 3, characterized in that: The metal shell (100) comprises a metal shell upper cover (170), a heat-insulating layer (180) is arranged on the lower side of the metal shell upper cover (170), the hollow suspension rod (141) passes through the metal shell upper cover (170) and the heat-insulating layer (180) and at least partially extends to the reaction chamber (210), and a sealing structure (190) is arranged at the connection between the hollow suspension rod (141) and the metal shell upper cover (170), and the sealing structure (190) is configured to seal the gap between the hollow suspension rod (141) and the metal shell upper cover (170).

5. The optical fiber preform sintering device according to claim 4, characterized in that: A supporting structure (200) is arranged inside the metal shell (100), the supporting structure (200) is configured to support the furnace core tube (110), the supporting structure (200) is provided with at least one connecting hole (201), the connecting hole (201) is configured to connect the reaction cavity (210) and the metal cavity (220), and the connecting hole (201) is configured to be openable or closable.

6. The optical fiber preform sintering device according to claim 5, characterized in that: The furnace core tube (110) is open at the top, the supporting structure (200) and the metal shell upper cover (170) and the side walls are arranged to form a top space (211), and the top space (211) and the inner cavity of the furnace core tube (110) together constitute a reaction chamber (210); the fourth pipeline (164) is in communication with the top space (211).

7. The optical fiber preform sintering device according to claim 3, characterized in that: The first pipeline (161), the second pipeline (162), the third pipeline (163) and the fourth pipeline (164) are provided with a pressure regulating device (230), the pressure regulating device (230) comprising an air pump (231) and a control valve (232), the air pump (231) being used for introducing and / or extracting gas into the reaction chamber (210), the metal chamber (220) and the hollow suspension rod (141).

8. The optical fiber preform sintering device according to claim 7, characterized in that: The reaction chamber (210) and the hollow suspension rod (141) are provided with at least one pressure monitoring device (240), and the metal chamber (220) is provided with a plurality of pressure monitoring devices (240) along a height direction.

9. The optical fiber preform sintering device according to any one of claims 1 to 3, characterized in that: A water cooling device is provided outside the metal shell (100), and the water cooling device is configured to control the temperature of the metal shell (100).

10. A method for sintering an optical fiber preform, characterized in that: The method is used for the optical fiber preform sintering device according to any one of claims 1 to 9, and the method comprises: The prefabricated optical fiber preform powder is fed into the reaction chamber (210), the hollow suspension rod (141) is inserted into the optical fiber preform and fixed, the metal housing upper cover (170) is closed, and the heating element is used to heat the preform to a set temperature; An oxidizing gas is introduced into the reaction chamber (210) and the hollow suspension rod (141) through an air pump (231), and a protective gas is introduced into the metal chamber (220), the pressure difference between the hollow suspension rod (141) and the reaction chamber (210), and between the reaction chamber (210) and the metal chamber (220) is adjusted within a certain range, and pressurization is stopped after the pressure in the furnace core tube (110) reaches a first preset value; Simultaneously introducing a target gas into the reaction chamber (210), the metal chamber (220), and the hollow suspension rod (141), adjusting the pressure difference between the hollow suspension rod (141) and the reaction chamber (210), and between the reaction chamber (210) and the metal chamber (220) within a certain range, and stopping pressurization after the pressure in the furnace core tube (110) reaches a second preset value; Relieving pressure from the hollow suspension rod (141), the reaction chamber (210), and the metal chamber (220), maintaining the pressure difference between the hollow suspension rod (141) and the reaction chamber (210), and between the reaction chamber (210) and the metal chamber (220) within a certain range, and stopping the pressure relief after the pressure in the furnace core tube (110) reaches a third preset value; The temperature is raised to a set temperature by the heating element until sintering is completed.

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