Method and device for preparing fluoride glass optical fiber preform by tube suction method

Abstract

The present invention belongs to the technical field of optical fiber preform preparation, and more particularly relates to a method and apparatus for preparing a fluoride glass optical fiber preform using a pipetting method. The method comprises the following steps: S1, heating and melting glass raw materials for the outer cladding, inner cladding, and core; S2, preparing the outer cladding by pipetting; S3, preparing the inner cladding by pipetting within the outer cladding; S4, preparing the core by pipetting within the inner cladding; and S5, annealing the outer cladding, inner cladding, and core to obtain a finished preform. The fluoride glass optical fiber preform prepared by the present invention has the advantages of good core-cladding interface quality, low impurity contamination, uniform core diameter, and a simple preparation process, and can be used to draw low-loss fluoride glass optical fibers.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber preform preparation, and in particular relates to a method and device for preparing a fluoride glass optical fiber preform by a tube suction method. Background Art

[0002] Fluoride glass has the advantages of low phonon energy, excellent mid-infrared transmittance, and high rare earth ion solubility, making it an important precursor glass material for mid-infrared optical fibers. Based on the composition of fluoride glass fibers, there are currently three main categories: fluorine-zirconium glass fibers, fluorine-indium glass fibers, and fluorine-aluminum glass fibers:

[0003] (1) Fluorozirconium glass fiber is mainly composed of ZrF4, whose infrared absorption edge can reach 7μm, and has high infrared transmittance. ZrF4 itself cannot form glass, but after adding BaF2 as a glass network modifier, rare earth elements (La), alkali metal elements (such as Na) and a small amount of AlF3 as glass stabilizers, it can form a stable glass body. The classic composition of fluorozirconium glass fiber is: 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF, that is, ZBLAN glass fiber. Studies have shown that ZBLAN glass fiber has low phonon energy (550cm -1 ), high rare earth solubility, high laser damage threshold, high fracture toughness, good chemical and thermal stability, and can be used as a gain medium for mid-infrared fiber lasers after being doped with rare earths.

[0004] (2) Fluorine-indium glass fiber is mainly composed of InF3, which has a relatively complex composition and involves a variety of heavy metal fluorides and rare earth elements. It can form ternary, quaternary, quinary, hexavalent and even more elemental glass systems. The atomic equivalent mass is large, and the strength of the glass is relatively weak. Therefore, fluorine-indium glass fiber has the lowest phonon energy (510cm) among fluoride glass fibers. -1 ), with an infrared cutoff edge of >8μm. However, due to its looser glass structure, indium fluoride glass is more susceptible to water erosion and more prone to crystallization than ZBLAN glass.

[0005] (3) Fluoroaluminum glass fiber is mainly composed of AlF3, and the classic composition is AYF (AlF3-MgF2-CaF2-SrF2-BaF2-YF3), which has low phonon energy (630cm -1 ) and a low refractive index, with an infrared cutoff of up to 6μm, a high glass transition temperature, and excellent chemical stability, far superior to ZBLAN glass. However, fluoroaluminum glass has shorter material properties than ZBLAN glass and fluorine-indium glass, making it more susceptible to crystallization during the preparation process.

[0006] For fluoride glass optical fibers, loss is one of their most important key indicators. The quality of the optical fiber preform plays a significant role in the magnitude of optical fiber loss. Factors affecting optical fiber preform quality include the core-cladding interface, oxide impurity particles, fluoride microcrystals, bubbles, hydroxyl absorption, and impure metal ions. Among these, oxide impurity particles are primarily ZrO2, which originates from the non-stoichiometric zirconium oxyfluoride formed by ZrF4 hydrate at high temperatures. Fluoride microcrystals originate from glass crystallization and are primarily related to the glass elemental composition, molding process, and impurity crystallization centers. Hydroxyl absorption is caused by the introduction of water from raw materials and the atmosphere during melting, casting, and fiber drawing, resulting in strong absorption at 2.7μm. Impure metal ions are primarily introduced through the raw materials, and metal impurities with specific absorption peaks can significantly increase the absorption loss of the optical fiber. Due to the complex composition of fluoride glass, numerous influencing factors, and the lack of corresponding gaseous compounds, fluoride glass optical fiber preforms cannot be prepared using the vapor deposition method like quartz optical fiber preforms. Currently, the main methods for preparing fluoride glass optical fibers include the tube-rod method, suction injection method, spin casting method, and double crucible method.

[0007] The tube-and-rod method is a widely used method for producing optical fiber preforms. Its key feature is the use of optical grinding and polishing to separately produce the core rod and cladding glass tube. The cladding glass tube and core rod are then sheathed together to form the optical fiber preform. While the tube-and-rod method makes it easy to control the core-cladding diameter ratio, it places extremely high demands on the optical processing quality of the inner surface of the cladding tube and the outer surface of the core rod. The tube-and-rod surface is susceptible to defects such as tiny scratches and pits, and is also easily contaminated by polishing materials and environmental particles. During the fiber drawing process, an air gap forms between the inner surface of the cladding tube and the outer surface of the core rod, making it difficult to completely remove the air and susceptible to contamination from environmental impurities, resulting in high interfacial losses. Furthermore, due to the surface energy of the material, glass is more susceptible to surface crystallization during softening. Consequently, crystallization is also more likely to occur on the inner surface of the cladding tube and the outer surface of the core rod during heating and softening. This crystallization is particularly severe for fluoride glass fibers, resulting in high interfacial losses.

[0008] The suction injection method utilizes the suction generated by the volumetric contraction of fluoride glass during cooling to produce optical fiber preforms. During preform production, a mold and a slug cavity are assembled to generate the contraction suction. The slug cavity and mold must be preheated. The molten cladding glass is poured into the mold, and then the core glass is poured on top of the cladding. As the glass cools, the volume of the molten glass in the mold and the slug cavity below shrinks. Because the temperature at the interface between the glass and the mold is low and the viscosity is high, while the temperature at the center is high and the viscosity is low, the cladding glass flows downward primarily in the center of the liquid column due to the volumetric contraction, thus forming a core-clad structure. The key advantage of the suction injection method is that, unlike the tube-and-rod method, which requires the processing of a sleeve and core rod, it avoids the increased core-clad interface losses associated with the tube-and-rod method. The suction injection method can achieve excellent core-clad interface quality. However, this method also has significant disadvantages. First, the timing and temperature of glass liquid pouring are difficult to accurately control, resulting in poor stability and consistency. Second, the core material injected by suction usually presents a cone shape, making it difficult to obtain a preform with a uniform core diameter. In addition, the pouring method used by the suction injection method determines that it is difficult to produce high-quality glass optical fiber preforms with excellent optical uniformity.

[0009] The spin casting method utilizes the centrifugal force generated by the high-speed rotation of a mold to produce optical fiber preforms. First, cladding glass liquid is poured into the mold and high-speed rotation is initiated. After the cladding glass solidifies, the mold is opened and the fiber core is poured into the mold, forming the optical fiber preform. This method utilizes centrifugal force to evenly distribute the molten glass and eliminate bubbles and inclusions, eliminating the need for additional processing. This avoids the mechanical drilling required in the tube-to-rod method, which can easily lead to glass cracking. Furthermore, the cladding tube's inner wall is smooth, preventing external contamination. Cladding glass tubes with varying outer and inner diameters can be easily produced by varying the mold size or the volume of molten glass poured into the mold. However, optical fiber preforms produced by the spin casting method are prone to numerous air bubble defects at the core-cladding interface.

[0010] Chinese patent CN201510478413.5 discloses a double-crucible method for producing optical fiber preforms based on the laminar flow effect. This method utilizes inner and outer crucibles to melt glass material. The injection rate is controlled by the piston's downward movement speed. By controlling the viscosity of the molten glass and the injection rate, the Reynolds number during the injection process is controlled to ensure laminar flow. Its greatest advantage is that, unlike the tube-and-rod method, which requires the processing of a sleeve and core rod, and unlike the suction injection method, which struggles to produce a preform with a uniform core diameter, the double-crucible laminar injection method achieves excellent core-cladding interface quality and a constant core diameter. However, when fluoride glass is melted, precipitates and highly adherent bubbles inevitably form at the bottom of the crucible. This is due to the high sensitivity of fluoride glass to air moisture and the nonstoichiometric zirconium oxyfluoride formed by ZrF4 hydrate at high temperatures. The double-crucible laminar injection method distributes these precipitates and bubbles within the preform through the laminar flow effect.

[0011] In summary, among the existing methods for preparing fluoride glass optical fiber preforms, the tube-rod method is difficult to process, has many defects on the internal and external surfaces, and is easily contaminated by the external environment; the suction injection method has poor stability and consistency, the core shape is conical, and it is difficult to obtain a preform with a uniform core diameter; the spin casting method is prone to bubble defects at the core-cladding interface; and the double crucible method is inevitably affected by sediment at the bottom of the crucible and bubbles with high adhesion.

[0012] Therefore, it is necessary to design a method and device for preparing fluoride glass optical fiber preform by tube suction method to solve the above problems. Summary of the Invention

[0013] The object of the present invention is to provide a method and apparatus for preparing a fluoride glass optical fiber preform by a tube aspiration method, so as to solve the above-mentioned problems and achieve the purpose of preparing a fluoride glass optical fiber preform with good core-cladding interface quality, less crucible impurity contamination, uniform core diameter and simple preparation process.

[0014] To achieve the above object, the present invention provides the following solution: a method for preparing a fluoride glass optical fiber preform by a tube suction method, comprising the following steps:

[0015] S1. Heat and melt the glass raw materials of the outer cladding, inner cladding and core;

[0016] S2, preparing the outer layer by suction;

[0017] S3, preparing an inner cladding by absorbing inside the outer cladding;

[0018] S4, preparing the fiber core by absorbing inside the inner cladding;

[0019] S5. Annealing the outer cladding, inner cladding and fiber core to obtain a preformed rod.

[0020] Preferably, in S1, the glass raw materials for the outer cladding, inner cladding and core are respectively placed in a platinum crucible, and the platinum crucible is placed in a furnace at 700° C.-900° C. and kept warm for 1 h-2 h to melt all the glass raw materials.

[0021] Preferably, in S2, the platinum crucible containing the molten raw material is taken out of the furnace and placed on a mobile platform. The temperature of the molten raw material is monitored using infrared temperature measurement. When the temperature of the molten raw material drops to 450°C-550°C, the quartz tube is inserted into the molten raw material of the outer cladding, and the molten raw material is sucked by negative pressure. After the suction is completed, the pressure is maintained for 5s-30s, the negative pressure is released, and the excess raw material is discharged to complete the preparation of the outer cladding.

[0022] Preferably, in S3, the platinum crucible containing the molten raw material of the inner cladding is moved to the bottom of the quartz tube by a mobile platform, and the quartz tube with the outer cladding is inserted into the molten raw material of the inner cladding. The molten raw material is sucked by negative pressure. After the suction is completed, the pressure is maintained for 5s-10s, the negative pressure is released, and the excess raw material is discharged to complete the preparation of the inner cladding.

[0023] Preferably, in S4, the platinum crucible containing the core molten raw material is moved to the bottom of the quartz tube by a mobile platform, and the quartz tube with the outer cladding and the inner cladding is inserted into the core molten raw material. The molten raw material is sucked by negative pressure, and the pressure is maintained for 10s-30s after the suction is completed. After the core raw material is solidified, the negative pressure is released.

[0024] Preferably, in S5, the quartz tube with the outer cladding, the inner cladding and the fiber core is placed in an annealing furnace for annealing. The annealing temperature is 10°C-20°C higher than the glass transition temperature. The annealing holding time is 2h-4h. After the holding is completed, the temperature is lowered to room temperature at a rate of 10°C / h to obtain a preformed rod product.

[0025] Preferably, a single-clad preform product can also be produced.

[0026] A device for preparing a fluoride glass optical fiber preform by a tube suction method comprises a movable platform, a platinum crucible is placed on top of the movable platform, a lifting column is provided on one side of the movable platform, the lifting column is fixedly connected to a valve body via a bracket, the valve body is fixedly connected to a quartz tube, the quartz tube is located above the platinum crucible, and the valve body is also fixedly connected to two hoses, one of which is fixedly connected to an aspirator, and the other is fixedly connected to an air release valve via a quick connector.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] 1. Good quality of the core-cladding interface: The inner wall of the prepared cladding tube is a surface naturally formed by glass liquid, and there is no defect or pollution caused by optical processing. In addition, the fiber core is smoothly drawn from the bottom up, and there is no need for optical processing of the core rod, which can obtain an excellent quality core-cladding interface, avoiding the negative impact of defects, pollution and crystallization on the core-cladding interface in the tube-rod method on optical fiber drawing, and greatly reducing the fiber interface loss.

[0029] 2. Less impurity contamination: Fluoride glass is volatile during melting, often resulting in a large amount of particulate matter and impurities adhering to the inner wall of the crucible. Directly pouring the molten glass from the crucible inevitably contaminates the molten glass. The present invention inserts the quartz glass tube directly into the cladding or core molten glass during operation, removing the molten glass from the crucible. This completely avoids contamination of the molten glass by impurities on the inner wall of the crucible, thereby reducing impurity scattering losses in the optical fiber.

[0030] 3. Uniform core diameter: Although the suction injection method can also obtain a good core-package interface, the obtained core shape presents a conical structure, and it is impossible to obtain a long optical fiber with a uniform core diameter. The optical fiber preform obtained by the present invention has good core diameter uniformity.

[0031] 4. Simple preparation process: Due to the large difference in thermal expansion coefficients between fluoride glass and quartz, the preform rod and the quartz tube will shrink to varying degrees after cooling, causing the preform rod to separate naturally from the inner wall of the quartz tube. The outer surface of the obtained preform rod is smooth and does not require polishing, and the overall preparation process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work.

[0033] Figure 1 Schematic diagram of the structure of the device of the present invention;

[0034] Figure 2 A flow chart for preparing a double-clad preform according to the present invention;

[0035] Figure 3 The flowchart of the preparation of single-clad preform rods of the present invention is shown.

[0036] Among them, 1. Mobile platform; 2. Platinum crucible; 3. Quartz tube; 4. Bracket; 5. Valve body; 6. Lifting column; 7. Quick connector; 8. Air release valve; 9. Hose; 10. Extractor. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Reference Figures 1 to 3 As shown, the present invention provides a method for preparing a fluoride glass optical fiber preform by a pipetting method, comprising the following steps:

[0040] S1. Heat and melt the glass raw materials of the outer cladding, inner cladding and core;

[0041] S2, preparing the outer layer by suction;

[0042] S3, preparing an inner cladding by absorbing inside the outer cladding;

[0043] S4, preparing the fiber core by absorbing inside the inner cladding;

[0044] S5. Annealing the outer cladding, inner cladding and fiber core to obtain a preformed rod.

[0045] To further optimize the solution, in S1, the glass raw materials for the outer cladding, inner cladding and core are respectively placed in a platinum crucible 2, and the platinum crucible 2 is placed in a furnace at 700°C-900°C and kept warm for 1h-2h to melt all the glass raw materials.

[0046] To further optimize the solution, in S2, the platinum crucible 2 containing the molten raw material is taken out of the furnace and placed on the mobile platform 1. The temperature of the molten raw material is monitored by infrared temperature measurement. When the temperature of the molten raw material drops to 450°C-550°C, the quartz tube 3 is inserted into the molten raw material of the outer cladding, and the molten raw material is sucked in by negative pressure. After the suction is completed, the pressure is maintained for 5s-30s, the negative pressure is released, and the excess raw material is discharged to complete the preparation of the outer cladding.

[0047] The quartz tube 3 is a mold for preparing preformed rods, and preformed rods of different sizes can be prepared using different diameters and lengths.

[0048] To further optimize the solution, in S3, the platinum crucible 2 containing the molten raw material for the inner cladding is moved to the bottom of the quartz tube 3 by the mobile platform 1, and the quartz tube 3 with the outer cladding is inserted into the molten raw material for the inner cladding. The molten raw material is sucked in by negative pressure. After the suction is completed, the pressure is maintained for 5s-10s, the negative pressure is released, and the excess raw material is discharged to complete the preparation of the inner cladding.

[0049] To further optimize the solution, in S4, the platinum crucible 2 containing the core molten raw material is moved to the bottom of the quartz tube 3 by the mobile platform 1, and the quartz tube 3 with the outer cladding and the inner cladding is inserted into the core molten raw material. The molten raw material is sucked by negative pressure. After the suction is completed, the pressure is maintained for 10s-30s. After the core raw material is solidified, the negative pressure is released.

[0050] The thickness of the cladding glass is controlled by controlling the pressure holding time after the molten raw material is sucked.

[0051] To further optimize the solution, in S5, the quartz tube 3 with the outer cladding, inner cladding and fiber core is placed in an annealing furnace for annealing. The annealing temperature is 10°C-20°C higher than the glass transition temperature. The annealing holding time is 2h-4h. After the holding is completed, the temperature is lowered to room temperature at a rate of 10°C / h to obtain a preformed rod product.

[0052] By further optimizing the solution, it is also possible to produce single-clad preform rod products.

[0053] When preparing a single-clad preform rod, only one cladding raw material melt and one core raw material melt need to be prepared. At the same time, step S3 is omitted, step S4 is changed to preparing the core by absorbing inside the outer cladding, and step S5 is changed to annealing the outer cladding and the core to obtain a finished single-clad preform rod.

[0054] The number of platinum crucibles 2 is 3 or 2. When the number of platinum crucibles 2 is 3, they are used to prepare double-clad preform rods. When the number of platinum crucibles 2 is 2, they are used to prepare single-clad preform rods. Different platinum crucibles 2 are used to hold different core and cladding raw material melts.

[0055] A device for preparing a fluoride glass optical fiber preform by a tube suction method includes a movable platform 1, a platinum crucible 2 placed on top of the movable platform 1, a lifting column 6 provided on one side of the movable platform 1, the lifting column 6 fixedly connected to a valve body 5 via a bracket 4, the valve body 5 fixedly connected to a quartz tube 3, the quartz tube 3 being located above the platinum crucible 2, and the valve body 5 further fixedly connected to two hoses 9, one of which fixedly connected to an aspirator 10, and the other of which fixedly connected to an air release valve 8 via a quick connector 7.

[0056] The mobile platform 1 has a programmable movement function, which can drive the placed platinum crucible 2 to move; the quartz tube 3 is assembled on the valve body 5 and sealed with an O-ring; the bracket 4 is installed on the lifting column 6, which has a programmable lifting function and can drive the valve body 5 and the quartz tube 3 to rise and fall and extend into the platinum crucible 2; the air release valve 8 and the aspirator 10 are connected to the valve body 5 via a quick connector 7 and a hose 9 respectively.

[0057] The air release valve 8 has a program control function, which maintains or releases the negative pressure in the quartz tube 3 through program control.

[0058] The aspirator 10 has a program-controlled function. By moving the piston to generate negative pressure, the glass liquid can be sucked or discharged under program control.

[0059] The production process of the present invention includes: operating a high-temperature furnace to melt the cladding and core glass separately in multiple platinum crucibles 2. After the core and cladding glass melts are complete, they are placed on a mobile platform 1 to monitor the temperature. When the temperature is appropriate, the glass melt is drawn into a quartz tube 3 to form a preform. The draw temperature is determined by the viscosity of the glass melt, and the cladding thickness is controlled by the dwell time. Cladding thickness is controlled by controlling the viscosity and dwell time of the glass melt, and the number of cladding layers is controlled by the number of draws. After annealing is complete, the quartz tube 3 is removed to obtain the desired optical fiber preform.

[0060] The movement of the piston in the aspirator 10 creates negative pressure to draw in the molten glass. After the molten glass cools to a certain temperature, the excess is expelled to form the cladding tube. This process can be controlled by controlling the temperature of the molten glass and the holding time after aspiration to achieve the desired cladding thickness. A bubble-free, good interface between the cladding and the fiber core is achieved by the excellent wettability of the glass surface at high temperatures. Furthermore, the differential thermal expansion between the quartz tube 3 and the fluoride glass allows for automatic demolding of the preform.

[0061] Example 1: A fluorine-zirconium-based double-clad fluoride glass optical fiber preform

[0062] 1. Place the fluorine zirconium-based outer cladding, inner cladding, and core glass into two 100 ml and one 75 ml platinum crucibles 2, respectively. Place the platinum crucibles 2 in a silicon carbon rod furnace and melt them at 700°C for 1 hour to completely melt the glass raw materials into a liquid state. Then stir with a platinum blade for 30 minutes at a stirring speed of 60 rpm to keep the glass liquid in the platinum crucible 2 at 700°C for standby use.

[0063] 2. Select a quartz tube 3 with an inner diameter of 15 cm and a length of 20 cm according to the target optical fiber size, insert the quartz tube 3 into the tenon of the valve body 5, and complete the fixation of the quartz tube 3.

[0064] 3. Take out the outer cladding, inner cladding and core glass liquid at intervals of 1 minute and 30 seconds respectively, and place them on the mobile platform 1. Use infrared temperature measurement to monitor the glass liquid temperature. After the temperature of the outer cladding glass liquid drops to 480℃, start the program, insert the quartz tube 3 into the outer cladding glass liquid, and draw the glass liquid until the liquid level is slightly higher than the required preform rod length.

[0065] 4. After the absorption is completed, lift the quartz tube 3 out of the liquid surface, maintain the pressure for 30 seconds, release the negative pressure, discharge the excess glass liquid, and complete the outer cladding preparation.

[0066] 5. Execute the program to align the quartz tube 3 with the inner cladding glass liquid, insert the quartz tube 3 with the outer cladding tube into the inner cladding glass liquid, and draw the inner cladding glass liquid until the liquid level is slightly higher than the outer cladding length.

[0067] 6. After the absorption is completed, lift the quartz tube 3 out of the liquid surface, maintain the pressure for 10 seconds after the absorption is completed, release the negative pressure, discharge the excess glass liquid, and complete the preparation of the inner cladding.

[0068] 7. Execute the program to align the quartz tube 3 with the core glass liquid, insert the quartz tube 3 with the cladding tube into the core glass liquid, and draw the core glass liquid until the liquid level is slightly higher than the inner cladding length.

[0069] 8. After the absorption is completed, lift the quartz tube 3 out of the liquid surface and maintain the pressure for 30 seconds. After the core glass liquid solidifies, release the negative pressure, remove the quartz tube 3, and immediately place it in the precision annealing furnace for annealing. Set the annealing starting temperature to 250℃, keep it at this temperature for 3 hours, and then cool it to room temperature at a rate of 10℃ / h.

[0070] 9. After annealing, the fluoride glass rod is taken out from the quartz tube 3 to obtain a fluorine zirconium-based glass optical fiber preform with a double-cladding structure.

[0071] Example 2: A fluorine-zirconium-based single-clad fluoride glass optical fiber preform

[0072] 1. Place the fluorine zirconium-based outer coating and core glass into two 100ml platinum crucibles 2 respectively. Place the platinum crucibles 2 in a silicon carbon rod furnace and melt them at 700°C for 1 hour to completely melt the glass raw materials into liquid. Then stir with a platinum blade for 30 minutes at a stirring speed of 60 rpm to keep the glass liquid in the platinum crucible 2 at 700°C for standby use.

[0073] 2. Select a quartz tube 3 with an inner diameter of 10 cm and a length of 20 cm according to the target optical fiber size, insert the quartz tube 3 into the tenon of the valve body 5, and complete the fixation of the quartz tube 3.

[0074] 3. Take out the outer cladding and core glass liquid after a 1-minute interval, place them on the mobile platform 1, use infrared temperature measurement to monitor the glass liquid temperature, start the program after the outer cladding glass liquid temperature drops to 450°C, insert the quartz tube 3 into the outer cladding glass liquid, and draw the glass liquid until the liquid level is slightly higher than the required preform rod length.

[0075] 4. After the absorption is completed, lift the quartz tube 3 out of the liquid surface, maintain the pressure for 10 seconds, release the negative pressure, discharge the excess glass liquid, and complete the outer cladding preparation.

[0076] 5. Execute the program to align the quartz tube 3 with the core glass liquid, insert the quartz tube 3 with the cladding tube into the core glass liquid, and draw the core glass liquid until the liquid level is slightly higher than the outer cladding length.

[0077] 6. After the absorption is completed, lift the quartz tube 3 out of the liquid surface and maintain the pressure for 10 seconds. After the core glass liquid solidifies, release the negative pressure, remove the quartz tube 3, and immediately place it in the precision annealing furnace for annealing. Set the annealing starting temperature to 250℃, keep it at this temperature for 2 hours, and then cool it to room temperature at a rate of 10℃ / h.

[0078] 7. After annealing, the fluoride glass rod is taken out from the quartz tube 3 to obtain a fluorine zirconium-based glass optical fiber preform with a single cladding structure.

[0079] Example 3: A Fluorine-Indium-Based Double-Clad Fluoride Glass Optical Fiber Preform

[0080] 1. Place the fluorine-indium-based outer cladding, inner cladding, and core glass into two 100 ml and one 75 ml platinum crucibles 2, respectively. Place the platinum crucibles 2 in a silicon carbon rod furnace and melt them at 900°C for 1 hour to completely melt the glass raw materials into a liquid state. Then stir with a platinum blade for 30 minutes at a stirring speed of 60 rpm to keep the glass liquid in the platinum crucible 2 at 800°C for standby use.

[0081] 2. Select a quartz tube 3 with an inner diameter of 12 cm and a length of 20 cm according to the target optical fiber size, insert the quartz tube 3 into the tenon of the valve body 5, and complete the fixation of the quartz tube 3.

[0082] 3. Take out the outer cladding, inner cladding and core glass liquid at intervals of 1.5 minutes and 30 seconds respectively, and place them on the mobile platform 1. Use infrared temperature measurement to monitor the glass liquid temperature. After the temperature of the outer cladding glass liquid drops to 550°C, start the program, insert the quartz tube 3 into the outer cladding glass liquid, and draw the glass liquid until the liquid level is slightly higher than the required preform rod length.

[0083] 4. After the absorption is completed, lift the quartz tube 3 out of the liquid surface and hold it for 30 seconds to release the negative pressure and discharge the excess glass liquid to complete the outer cladding preparation.

[0084] 5. Execute the program to place the quartz tube 3 against the inner cladding glass liquid, insert the quartz tube 3 with the outer cladding tube into the inner cladding glass liquid, and draw the inner cladding glass liquid until the liquid level is slightly higher than the outer cladding length.

[0085] 6. After the absorption is completed, lift the quartz tube 3 out of the liquid surface, maintain the pressure for 5 seconds after the absorption is completed, release the negative pressure, discharge the excess glass liquid, and complete the preparation of the inner cladding.

[0086] 7. Execute the program to align the quartz tube 3 with the core glass liquid, insert the quartz tube 3 with the cladding tube into the core glass liquid, and draw the core glass liquid until the liquid level is slightly higher than the inner cladding length.

[0087] 8. After the absorption is completed, lift the quartz tube 3 out of the liquid surface and maintain the pressure for 30 seconds. After the core glass liquid solidifies, release the negative pressure, remove the quartz tube 3, and immediately place it in the precision annealing furnace for annealing. Set the annealing starting temperature to 230℃, keep it at this temperature for 4 hours, and then cool it to room temperature at a rate of 10℃ / h.

[0088] 9. After the annealing is completed, the fluoride glass rod is taken out from the quartz tube 3 to obtain a fluorine-indium-based glass optical fiber preform with a double-cladding structure.

[0089] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0090] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a fluoride glass optical fiber preform by a tube suction method, characterized in that: The following steps are included S1. Heat and melt the glass raw materials of the outer cladding, inner cladding and core; Putting the glass raw materials of the outer cladding, inner cladding and core into platinum crucibles (2) respectively, placing the platinum crucible (2) in a furnace at 700° C.-900° C., and keeping the temperature for 1 hour-2 hours to melt all the glass raw materials; S2, preparing the outer layer by suction; The platinum crucible (2) containing the molten raw material is taken out of the furnace and placed on the mobile platform (1). The temperature of the molten raw material is monitored by infrared temperature measurement. When the temperature of the molten raw material drops to 450° C.-550° C., the quartz tube (3) is inserted into the outer cladding molten raw material, and the molten raw material is sucked by negative pressure. After the suction is completed, the pressure is maintained for 5 seconds-30 seconds, and the negative pressure is released to discharge excess raw material, thereby completing the preparation of the outer cladding; S3, preparing an inner cladding by absorbing inside the outer cladding; The platinum crucible (2) containing the inner cladding molten raw material is moved to the bottom of the quartz tube (3) by the moving platform (1), and the quartz tube (3) with the outer cladding is inserted into the inner cladding molten raw material, and the molten raw material is sucked by negative pressure. After the suction is completed, the pressure is maintained for 5s-10s, and the negative pressure is released to discharge the excess raw material, thereby completing the preparation of the inner cladding; S4, preparing the fiber core by absorbing inside the inner cladding; The platinum crucible (2) containing the fiber core molten raw material is moved to the bottom of the quartz tube (3) by a movable platform (1), and the quartz tube (3) with an outer cladding and an inner cladding is inserted into the fiber core molten raw material. The molten raw material is sucked by negative pressure, and the pressure is maintained for 10s-30s after the suction is completed. After the fiber core raw material is solidified, the negative pressure is released; S5, annealing the outer cladding, inner cladding and core to obtain a preformed rod; The quartz tube (3) with the outer cladding, the inner cladding and the fiber core is placed in an annealing furnace for annealing. The annealing temperature is 10-20°C higher than the glass transition temperature. The annealing holding time is 2h-4h. After the holding is completed, the temperature is lowered to room temperature at a rate of 10°C / h to obtain a prefabricated rod product.

2. A device used in the method for preparing a fluoride glass optical fiber preform by a pipetting method according to claim 1, characterized in that: The invention comprises a mobile platform (1), a platinum crucible (2) is placed on the top of the mobile platform (1), a lifting column (6) is provided on one side of the mobile platform (1), the lifting column (6) is fixedly connected to a valve body (5) through a bracket (4), the valve body (5) is fixedly connected to a quartz tube (3), the quartz tube (3) is located above the platinum crucible (2), and the valve body (5) is also fixedly connected to two hoses (9), one of the hoses (9) is fixedly connected to an extractor (10), and the other hose (9) is fixedly connected to an air release valve (8) through a quick interface (7).

Images