Method for preparing rare earth doped quartz-based optical fiber by using in-tube melting method after raw material pretreatment

Abstract

The invention relates to the field of doped optical fiber preparation, in particular to a method for preparing a rare earth doped quartz-based optical fiber by using an in-tube melting method after raw material pretreatment, which comprises the following steps: introducing an inorganic compound containing rare earth elements, carrying out primary high-temperature pre-sintering treatment on the mechanically ground medicine raw material, and then carrying out a ball milling process to prepare the rare earth doped quartz-based optical fiber. The raw materials are dried and sieved after being subjected to ball milling, then are subjected to secondary presintering to be converted into cristobalite blocks, and then are transferred into a high-melting-point quartz tube to be subjected to vacuum melting for a period of time at the temperature above the melting point of cristobalite, so that the drawing of the transparent bubble-free optical fiber is realized. In the process, an inorganic compound of rare earth elements is introduced, so that the solubility of rare earth ions in the quartz glass is improved, and the melting point of the quartz raw material is reduced; by adopting a ball milling process, the uniformity of the raw materials is improved, and the improvement of the uniformity of later molten glass is facilitated; the raw materials are converted into cristobalite phases through two times of pre-sintering, and the effect of reducing bubbles of fiber core glass by combining an in-vacuum-tube melting method is remarkable.

Description

Technical Field

[0001] The present invention relates to the field of doped optical fiber preparation, in particular to a method for preparing rare earth doped quartz-based optical fiber by pre-sintering raw materials twice in combination with an in-tube melting method. Background Art

[0002] Rare-earth-doped silica-based optical fibers are used as gain media in fiber lasers and fiber amplifiers. Currently, the most commonly used rare-earth-doped optical fiber is rare-earth-doped silica glass fiber. The solubility of rare-earth ions alone in silica glass is 460 ppm. The limited solubility of silica glass for rare-earth ions makes it difficult to increase the doping concentration, thereby limiting the gain power and efficiency of the laser. Furthermore, low rare-earth ion concentrations result in insufficient laser gain per unit length of the fiber, necessitating compensation by increasing the fiber length, which in turn increases transmission losses.

[0003] Currently, the fabrication technology for rare-earth-doped silica-based optical fibers primarily involves depositing an optical fiber preform through a modified chemical vapor deposition method, followed by fiber drawing. However, this modified chemical vapor deposition method has drawbacks such as high equipment cost, complex process, and low production efficiency.

[0004] To address the above issues, the present invention proposes a method for preparing rare earth-doped silica-based optical fibers by combining double pre-sintering of raw materials with an in-tube melting method. This method solves the above-mentioned problems of low rare earth ion doping concentration, complex process, and low production efficiency, thereby realizing the preparation of high-concentration rare earth ion-doped silica-based glass optical fibers. Summary of the Invention

[0005] The technical solution of the present invention is as follows: A method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with an in-tube melting method, comprising the following steps:

[0006] (1) Weigh rare earth oxide, silicon dioxide powder and inorganic compounds containing elements such as aluminum (Al), germanium (Ge), phosphorus (P) or boron (B), with the mass ratio of rare earth oxide to inorganic compound being 1:1 to 1:15.

[0007] (2) The mechanically ground pharmaceutical raw materials are pre-sintered at a high temperature of 1500°C to 1650°C to pre-treat the rare earth oxides, silica powder and introduced inorganic compounds, and the heat preservation time is more than 1 hour.

[0008] (3) The raw materials after high-temperature pre-calcination are ball-milled, using a volatile and non-toxic organic liquid as a solvent, and wet high-energy ball milling for 6h to 12h at a rotation speed between 500r / min and 1500r / min.

[0009] (4) The ball-milled raw materials are placed in an oven for drying at a temperature of 60°C to 100°C for 6 hours to 12 hours to remove the organic solvent.

[0010] (5) After drying, the glass powder is sieved, and the particle size of the sieved glass powder is in the range of 10nm to 500nm.

[0011] (6) The raw material powder that has been ball-milled to form a particle size distribution is pre-sintered for the second time, and the temperature is slowly raised from room temperature to 200 °C to ensure that there is no organic solvent residue in the raw material after ball milling and drying. The temperature is then raised to 1500 °C to 1650 °C at a rate of 1 °C / min to 5 °C / min, and kept at this temperature for more than 2 h to fully transform it into the cristobalite phase, and then cooled to room temperature with the furnace.

[0012] (7) Transfer the cristobalite block into a high-purity quartz tube with one end sealed and the other end connected to a vacuum pump with a vacuum degree of 10 2 Pa~10 5 Pa.

[0013] (8) The quartz tube is installed on the drawing tower and melted at a high temperature of 1715°C to 1780°C (higher than the melting point of cristobalite 1713°C). The raw material melting time is 1h to 4h, and the vacuum state is maintained throughout the process.

[0014] (9) The temperature of the drawing tower is then raised to 1850°C to 1950°C. After the material head falls, it is pulled to the auxiliary pulling wheel for optical fiber pulling. The optical fiber is drawn by controlling the rod feeding speed and the optical fiber drawing speed.

[0015] Furthermore, inorganic compounds containing elements such as aluminum (Al), germanium (Ge), phosphorus (P) or boron (B) include but are not limited to oxides such as Al2O3, GeO2, P2O5, and B2O3.

[0016] The key point of the present invention is to introduce inorganic compounds containing elements such as aluminum (Al), germanium (Ge), phosphorus (P), and boron (B), and then perform a high-temperature pre-sintering treatment on the mechanically ground raw materials. The materials are then ball-milled, dried, and screened, followed by a second pre-sintering process to transform them into cristobalite blocks. The blocks are then transferred to a high-melting-point quartz tube and vacuum-melted above the melting point of cristobalite for a period of time before optical fiber drawing. Compared to using an improved chemical vapor deposition method to prepare optical fiber preforms and then drawing them, the solubility of rare earth ions in quartz glass is increased. The use of two pre-sinterings of raw materials combined with an in-tube melting method to prepare rare earth-doped silica-based optical fibers reduces the optical fiber loss caused by uneven core glass during melting. The doping concentration of rare earth ions can be increased from 460 ppm for single doping to 800 ppm to 3800 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the drawings required for describing the specific implementation or the prior art will be briefly introduced below. Obviously, the drawings described below are only one implementation of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a process flow chart of an embodiment of the present invention;

[0019] Figure 2 This is a scanning electron microscope image of the particles after ball milling according to an embodiment of the present invention;

[0020] Figure 3 This is a picture of the powder after sieving in an embodiment of the present invention;

[0021] Figure 4 This is a picture of a cristobalite block after the second pre-firing in an embodiment of the present invention;

[0022] Figure 5 This is a picture of the embodiment of the present invention before heating by the vacuum tube melting method;

[0023] Figure 6 This is a picture of the glass head according to an embodiment of the present invention;

[0024] Figure 7 is the refractive index of the rare earth-doped silica-based optical fiber according to an embodiment of the present invention;

[0025] Figure 8 The optical fiber loss of the rare earth-doped silica-based optical fiber at 1540 nm according to an embodiment of the present invention;

[0026] Figure 9 This is the amplified spontaneous emission spectrum of the rare earth-doped silica-based optical fiber according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the technical solutions in the specific implementation methods of the present invention are clearly and completely described below to further illustrate the present invention. Obviously, the specific implementation methods described are only part of the implementation methods of the present invention, rather than all styles.

[0028] Example 1: A method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice and melting in a tube, such as Figure 1 As shown, the following steps are included:

[0029] (1) According to the designed glass composition SiO2-Pr2O3-Al2O3, the raw materials used are silicon dioxide, praseodymium oxide, and aluminum oxide. The mass ratio of praseodymium oxide to aluminum oxide is 1:10. The raw materials are weighed according to the raw material composition. In this case, the total amount of raw materials weighed is 50g.

[0030] (2) The mechanically ground raw materials were pre-burned at 1650°C for 1 hour.

[0031] (3) The raw materials after high-temperature pre-calcination were ball-milled using anhydrous ethanol as a solvent and wet high-energy ball milling for 8 hours at a speed of 1000 r / min. The scanning electron microscope image of the particles after ball milling is as follows: Figure 2 shown.

[0032] (4) Place the ball-milled raw materials in a 100°C oven and dry for 8 hours.

[0033] (5) After drying, the glass powder is sieved. The sieved glass powder particles are as follows Figure 3 As shown, the particle size is in the range of 10 nm to 500 nm.

[0034] (6) The sieved glass powder particles are pre-fired for the second time, and the temperature is slowly raised from room temperature to 200 ° C to ensure that there is no organic solvent residue in the raw material after ball milling and drying. Then the temperature is raised to 1650 ° C at 5 ° C / min and kept at this temperature for 2 hours to fully transform it into the cristobalite phase. Then it is cooled to room temperature in the furnace. The obtained cristobalite block is as follows Figure 4 shown.

[0035] (7) Transfer the cristobalite block into a high-purity quartz tube with one end sealed, such as Figure 5 As shown, the other end is connected to a vacuum pump with a vacuum degree of 8×10 2 Pa.

[0036] (8) The quartz tube is mounted on a drawing tower and melted at a high temperature of 1750°C (higher than the melting point of cristobalite 1713°C). The raw material melting time is 2 hours, and the vacuum state is maintained throughout the process.

[0037] (9) Then the drawing tower temperature is raised to 1900℃. After the material head falls, it is pulled to the auxiliary pulley for optical fiber pulling. The optical fiber is drawn by controlling the rod feeding speed and the optical fiber drawing speed. Figure 6 shown.

[0038] In order to verify the performance of the rare earth-doped silica-based optical fiber obtained in this embodiment, the rare earth-doped silica-based optical fiber obtained in this embodiment was tested. Figure 7 is the refractive index of rare earth doped silica-based optical fiber, which is higher than Pr 3+In single-doped silica glass, the introduction of Al and Ge can increase the refractive index, while the introduction of F can reduce the refractive index. By controlling the type of co-doped ions and the ratio with rare earth ions, the glass refractive index and the solubility of rare earth ions can be changed. Table 1 shows the glass uniformity of rare earth-doped silica-based optical fiber. The glass uniformity △n is ±0.0006, which is excellent. Figure 8 The fiber loss of doped silica-based optical fiber at 1540nm is 0.903dB / m; Figure 9 The amplified spontaneous emission spectrum of rare-earth-doped silica-based optical fiber is expected to achieve laser output in the 600nm, 615nm, 645nm, 886nm and 1056nm bands.

[0039] Table 1 Glass uniformity of rare earth doped silica-based optical fiber

[0040]

[0041] Example 2: A method for preparing a rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with an in-tube melting method, comprising the following steps:

[0042] (1) According to the designed glass composition SiO2-GeO2-Er2O3-Yb2O3, the raw materials used are silicon dioxide, germanium oxide, erbium oxide, and ytterbium oxide. The mass ratio of erbium oxide: ytterbium oxide: germanium oxide is 1:2:6. Weigh the raw materials according to the raw material composition. In this case, the total amount of raw materials weighed is 50g.

[0043] (2) The mechanically ground raw materials were pre-burned at 1650°C for 2 hours.

[0044] (3) The raw materials after high-temperature pre-calcination were ball-milled using anhydrous ethanol as a solvent and wet high-energy ball milling for 8 hours at a rotation speed of 500 r / min.

[0045] (4) Place the ball-milled raw materials in a 100°C oven and dry for 10 hours.

[0046] (5) After drying, the glass powder is sieved and the particle size is in the range of 10nm to 500nm.

[0047] (6) The sieved glass powder particles are pre-sintered for the second time, slowly heating from room temperature to 200 °C, then heating to 1500 °C at a rate of 2 °C / min, and keeping the temperature for 2 h to fully transform it into the cristobalite phase, and then cooling to room temperature with the furnace.

[0048] (7) Transfer the cristobalite block into a high-purity quartz tube with one end sealed and the other end connected to a vacuum pump with a vacuum degree of 8×10 2 Pa.

[0049] (8) The quartz tube is mounted on a drawing tower and melted at a high temperature of 1780°C (higher than the melting point of cristobalite 1713°C). The raw material melting time is 2 hours, and the vacuum state is maintained throughout the process.

[0050] (9) The temperature of the drawing tower is then raised to 1900°C. After the material head falls, it is pulled to the auxiliary pulling wheel for optical fiber pulling. The optical fiber is drawn by controlling the rod feeding speed and the optical fiber drawing speed.

[0051] Example 3: A method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with an in-tube melting method, comprising the following steps:

[0052] (1) According to the designed glass composition SiO2-Al2O3-Tm2O3, the raw materials used are silicon dioxide, aluminum oxide, and thulium oxide. The mass ratio of thulium oxide to aluminum oxide is 1:5. Weigh the raw materials according to the raw material composition. In this case, the total amount of raw materials weighed is 50g.

[0053] (2) The mechanically ground raw materials were pre-burned at 1550°C for 2 hours.

[0054] (3) The raw materials after high-temperature pre-calcination were ball-milled using anhydrous ethanol as a solvent and wet high-energy ball milling for 10 hours at a rotation speed of 1500 r / min.

[0055] (4) Place the ball-milled raw materials in a 100°C oven and dry for 6 hours.

[0056] (5) After drying, the glass powder is sieved and the particle size is in the range of 10nm to 500nm.

[0057] (6) The sieved glass powder particles are pre-fired for the second time, slowly heating from room temperature to 200 °C, then heating to 1500 °C at 4 °C / min, and keeping warm for 2 h to fully transform it into the cristobalite phase, and then cooling to room temperature with the furnace.

[0058] (7) Transfer the cristobalite block into a high-purity quartz tube with one end sealed and the other end connected to a vacuum pump with a vacuum degree of 8×10 2 Pa.

[0059] (8) The quartz tube is mounted on a drawing tower and melted at a high temperature of 1750°C (higher than the melting point of cristobalite 1713°C). The raw material melting time is 2 hours, and the vacuum state is maintained throughout the process.

[0060] (9) The temperature of the drawing tower is then raised to 1950°C. After the material head falls, it is pulled to the auxiliary pulling wheel for optical fiber pulling. The optical fiber is drawn by controlling the rod feeding speed and the optical fiber drawing speed.

[0061] The optical fibers prepared in the above three cases can change the glass refractive index and the solubility of rare earth ions by controlling the type of co-doped ions and the ratio with rare earth ions. They have the advantages of excellent glass uniformity, short production cycle and low cost, and are suitable for the preparation of rare earth ion-doped gain fibers.

[0062] The above describes the main technical features and basic principles of the present invention and the related advantages. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the concept or essential characteristics of the present invention. Therefore, from all perspectives, the above-mentioned specific embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing description, and it is intended that all changes that come within the meaning and range of equivalents of the claims be included within the present invention.

[0063] In addition, it should be understood that although this specification is described according to various implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with an in-tube melting method, characterized in that: Silica powder, rare earth oxides and co-doped inorganic compounds containing aluminum, germanium, phosphorus or boron are weighed, and the mechanically ground pharmaceutical raw materials are subjected to a high-temperature pre-sintering treatment, followed by a ball milling process. After ball milling, the raw materials are dried and sieved, and then pre-sintered for a second time to transform into cristobalite blocks, which are then transferred to a high-melting-point quartz tube and vacuum-melted above the melting point of cristobalite before optical fiber drawing.

2. The method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with in-tube melting as claimed in claim 1, characterized in that: The co-doped inorganic compound containing aluminum, germanium, phosphorus or boron elements is: Al2O3, GeO2, P2O5 or B2O3.

3. The method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with in-tube melting as claimed in claim 1, characterized in that: The mechanically ground pharmaceutical raw materials are pre-fired at a high temperature of 1500°C to 1650°C to pre-treat the rare earth oxides, silicon dioxide powder and introduced inorganic compounds, and the heat preservation time is greater than 1 hour.

4. The method for preparing rare earth-doped silica-based optical fiber by double pre-sintering of raw materials combined with in-tube melting as claimed in claim 1, characterized in that: During ball milling, a volatile and non-toxic organic liquid is used to mix the raw materials pre-burned at a high temperature. The wet high-energy ball milling is performed for 6 hours to 12 hours at a rotation speed of 500 r / min to 1500 r / min.

5. The method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with in-tube melting as claimed in claim 4, characterized in that: The particle size after drying and sieving is in the range of 10nm to 500nm.

6. The method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with in-tube melting as claimed in claim 1, characterized in that: The process of secondary pre-calcination of the dried and sieved raw material powder is to slowly heat it from room temperature to 200°C to ensure that there is no organic solvent residue in the raw material after ball milling and drying, and then heat it to 1500°C~1650°C at a rate of 1°C / min~5°C / min, keep it warm for more than 2 hours to fully transform it into cristobalite phase, and then cool it to room temperature with the furnace.

7. The method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with in-tube melting as claimed in claim 1, characterized in that: The tube melting method uses a high-purity quartz cladding as a reaction vessel, melts at 1715℃~1780℃, and the vacuum degree is 10 2 Pa~10 5 Pa, melting time 1h~4h, keep vacuum state throughout the process.

8. The method for preparing rare earth-doped silica-based optical fiber by pre-sintering raw materials twice in combination with in-tube melting as claimed in claim 1, characterized in that: The process of drawing optical fiber is to raise the temperature of the drawing tower to 1850℃~1950℃. After the material head falls, it is pulled to the auxiliary pulling wheel for optical fiber drawing. The optical fiber is drawn by controlling the rod feeding speed and the optical fiber drawing speed.

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