A method for producing a rare earth-doped quartz-based optical fiber using an in-tube melting method after pre-treating a raw material

Abstract

The present application relates to the field of doped optical fiber preparation, and particularly relates to a method for preparing a rare earth doped quartz-based optical fiber by using an in-tube melting method after pretreating raw materials, the method introduces an inorganic compound containing rare earth elements, performs a high-temperature pre-sintering treatment on the mechanically ground raw material, then performs a ball milling process, the raw material is dried and sieved after ball milling, then is converted into a cristobalite block by a second pre-sintering, and is then transferred into a high-melting-point quartz tube to be melted at a temperature above the melting point of cristobalite for a period of time, so that a transparent bubble-free optical fiber is drawn. In the above process, the inorganic compound containing rare earth elements improves the solubility of rare earth ions in quartz glass and reduces the melting point of the quartz raw material; the ball milling process improves the uniformity of the raw material, which is beneficial to improving the uniformity of the later molten glass; the two pre-sintering processes convert the raw material into a cristobalite phase, which significantly reduces the bubbles in the core glass in combination with the vacuum in-tube melting method.

Description

Technical Field

[0001] This invention relates to the field of doped optical fiber preparation, and more particularly to a method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials. Background Technology

[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 fiber is rare-earth-doped silica glass fiber. The solubility of rare-earth ions in silica glass alone is 460 ppm. The limited solubility of rare-earth ions in silica glass makes it difficult to increase the doping concentration, thus limiting the gain, power, and efficiency of the laser. Furthermore, the low concentration of rare-earth ions results in insufficient laser gain per unit length of fiber, requiring compensation by increasing the fiber length, but this increases transmission loss.

[0003] Currently, the main technology for fabricating rare-earth-doped silica-based optical fibers involves depositing fiber preforms using a modified chemical vapor deposition (CVD) method, followed by fiber drawing. However, the modified CVD method suffers from drawbacks such as high equipment costs, complex processes, and low production efficiency.

[0004] To address the above problems, this invention proposes a method for preparing rare earth-doped quartz-based optical fibers using an in-tube melting method after pretreatment of raw materials. This method solves the problems of low rare earth ion doping concentration, complex process, and low production efficiency, thereby achieving the preparation of high-concentration rare earth ion-doped quartz-based glass optical fibers. Summary of the Invention

[0005] The technical solution of this invention is as follows: A method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials, comprising the following steps:

[0006] (1) Weigh rare earth oxides, 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 oxides to inorganic compounds being 1:1 to 1:15.

[0007] (2) The mechanically ground pharmaceutical raw materials are pre-calcined at 1500℃~1650℃ to pre-treat rare earth oxides, silicon dioxide powder and introduced inorganic compounds, and the heat treatment 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. The wet high-energy ball milling process lasts for 6 to 12 hours, with a rotation speed between 500 r / min and 1500 r / min.

[0009] (4) Place the ball-milled pharmaceutical raw materials into an oven to dry at a temperature of 60℃~100℃ for 6h~12h to remove organic solvents.

[0010] (5) After drying, the glass powder is sieved. 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-fired a second time. The temperature is slowly increased 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 increased to 1500°C to 1650°C at a rate of 1°C / min to 5°C / min and held for more than 2 hours to fully transform it into cristobalite phase. Then the furnace is cooled to room temperature.

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

[0013] (8) Install the quartz tube on the drawing tower and melt it at a high temperature of 1715℃~1780℃ (higher than the melting point of cristobalite 1713℃). The raw material melting time is 1h~4h, and the whole process is kept in a vacuum state.

[0014] (9) Then the temperature of the drawing tower is raised to 1850℃~1950℃. After the material head falls off, it is pulled to the auxiliary traction wheel for optical fiber traction. 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 this invention lies in introducing inorganic compounds containing elements such as aluminum (Al), germanium (Ge), phosphorus (P), and boron (B) to pre-calcine mechanically ground pharmaceutical raw materials at high temperatures, followed by ball milling. After ball milling, the raw materials are dried and sieved, then pre-calcineed a second time to transform them into cristobalite blocks. These blocks are then transferred to a high-melting-point quartz tube and vacuum-melted for a period above the melting point of cristobalite before optical fiber drawing. Compared to using an improved chemical vapor deposition method to prepare optical fiber preforms before fiber drawing, this method improves the solubility of rare earth ions in quartz glass. The use of a two-stage pre-calcine process combined with in-tube melting to prepare rare earth-doped quartz-based optical fibers reduces fiber loss caused by inhomogeneity of the 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. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0019] Figure 2 This is a scanning electron microscope (SEM) image of the particles after ball milling in an embodiment of the present invention.

[0020] Figure 3 Images of powder after sieving according to an embodiment of the present invention;

[0021] Figure 4 This is an image of the cristobalite block after the second pre-firing according to an embodiment of the present invention;

[0022] Figure 5 This is a picture taken before heating using the vacuum tube melting method in an embodiment of the present invention.

[0023] Figure 6 Images of glass feedstock from embodiments of the present invention;

[0024] Figure 7 The refractive index of the rare earth-doped quartz-based optical fiber in this embodiment of the invention;

[0025] Figure 8 This refers to the fiber loss at 1540 nm of rare-earth-doped quartz-based optical fiber in an embodiment of the present invention.

[0026] Figure 9 This is an amplified spontaneous emission spectrum of a rare-earth-doped quartz-based optical fiber according to an embodiment of the present invention. Detailed Implementation

[0027] To make the technical means, creative features, objectives and effects of this invention easier to understand, the technical solutions in the specific embodiments of this invention are described clearly and completely below to further illustrate this invention. Obviously, the specific embodiments described are only a part of the embodiments of this invention, and not all of them.

[0028] Example 1: A method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials, such as... Figure 1 As shown, it includes the following steps:

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

[0030] (2) The mechanically ground pharmaceutical raw materials were pre-calcined at 1650℃ for 1 hour.

[0031] (3) The raw material after high-temperature pre-calcination was ball-milled using anhydrous ethanol as solvent. Wet high-energy ball milling was performed for 8 hours at a speed of 1000 r / min. The scanning electron microscope image of the particles after ball milling is shown below. Figure 2 As shown.

[0032] (4) Place the ball-milled pharmaceutical raw materials in a 100℃ 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 10nm to 500nm.

[0034] (6) The sieved glass powder is pre-fired a second time, slowly heated 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 increased to 1650°C at 5°C / min and held for 2 hours to fully transform it into the cristobalite phase. Then, it is cooled to room temperature with the furnace. The obtained cristobalite blocks are as follows: Figure 4 As shown.

[0035] (7) Transfer the cristobalite block into a high-purity quartz tube that is sealed at one end, such as... Figure 5 As shown, the other end is connected to a vacuum pump, with a vacuum level of 8×10⁻⁶. 2 Pa.

[0036] (8) Install the quartz tube on the drawing tower and melt it at a high temperature of 1750℃ (higher than the melting point of cristobalite 1713℃). The raw material melting time is 2 hours, and the whole process is kept in a vacuum state.

[0037] (9) Subsequently, the temperature of the drawing tower is raised to 1900℃. After the filament head falls off, it is pulled to the auxiliary traction wheel for optical fiber traction. The optical fiber is drawn by controlling the bar feeding speed and the optical fiber drawing speed. The filament head is as follows: Figure 6 As shown.

[0038] To verify the performance of the rare-earth-doped silica-based optical fiber obtained in this embodiment, tests were conducted on the fiber. Figure 7 The refractive index of rare earth-doped silica-based optical fiber is higher than that of Pr. 3+In monodoped quartz glass, the introduction of Al and Ge can increase the refractive index, while the introduction of F can decrease it. The refractive index and the solubility of rare earth ions can be altered by controlling the types of co-doped ions and their ratio with rare earth ions. Table 1 shows the glass homogeneity of rare earth-doped quartz-based optical fibers. The glass homogeneity Δn is ±0.0006, indicating excellent glass homogeneity. Figure 8 The fiber loss at 1540 nm is 0.903 dB / m for the doped silica-based optical fiber. Figure 9 The amplified spontaneous emission spectrum of rare-earth-doped quartz-based optical fiber is expected to enable laser output in the 600nm, 615nm, 645nm, 886nm and 1056nm bands.

[0039] Table 1 Glass homogeneity of rare earth-doped silica-based optical fibers

[0040]

[0041] Example 2: A method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials, comprising the following steps:

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

[0043] (2) The mechanically ground pharmaceutical raw materials were pre-calcined at 1650℃ for 2 hours.

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

[0045] (4) Place the ball-milled pharmaceutical raw materials in a 100℃ 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 glass powder after sieving is pre-fired twice. The temperature is slowly increased from room temperature to 200°C, and then increased to 1500°C at 2°C / min. The temperature is held for 2 hours to allow it to fully transform into the cristobalite phase. Then the powder is cooled to room temperature with the furnace.

[0048] (7) Transfer the cristobalite block into a high-purity quartz tube sealed at one end, and connect the other end to a vacuum pump with a vacuum level of 8×10⁻⁶. 2 Pa.

[0049] (8) Install the quartz tube on the drawing tower and melt it at a high temperature of 1780℃ (higher than the melting point of cristobalite 1713℃). The raw material melting time is 2 hours, and the whole process is kept in a vacuum state.

[0050] (9) Then the temperature of the drawing tower is raised to 1900℃. After the material head falls off, it is pulled to the auxiliary traction wheel for optical fiber traction. 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 fibers using an in-tube melting method after pretreatment of raw materials, comprising the following steps:

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

[0053] (2) The mechanically ground pharmaceutical raw materials were pre-calcined at 1550℃ for 2 hours.

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

[0055] (4) Place the ball-milled pharmaceutical raw materials in a 100℃ 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 glass powder after sieving is pre-fired twice. The temperature is slowly increased from room temperature to 200°C, and then increased to 1500°C at 4°C / min. The temperature is held for 2 hours to allow it to fully transform into the cristobalite phase. Then the powder is cooled to room temperature with the furnace.

[0058] (7) Transfer the cristobalite block into a high-purity quartz tube sealed at one end, and connect the other end to a vacuum pump with a vacuum level of 8×10⁻⁶. 2 Pa.

[0059] (8) Install the quartz tube on the drawing tower and melt it at a high temperature of 1750℃ (higher than the melting point of cristobalite 1713℃). The raw material melting time is 2 hours, and the whole process is kept in a vacuum state.

[0060] (9) Then the temperature of the drawing tower is raised to 1950°C. After the material head falls off, it is pulled to the auxiliary traction wheel for optical fiber traction. 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 their ratio with rare earth ions. They have advantages such as excellent glass uniformity, short production cycle and low cost, and are suitable for preparing rare earth ion doped gain optical fibers.

[0062] The main technical features, basic principles, and related advantages of the present invention have been described above. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the concept or basic characteristics of the invention. Therefore, the above-described embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0063] Furthermore, it should be understood that although this specification describes various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials, characterized in that: Weigh silica powder, rare earth oxides and inorganic compounds containing aluminum, germanium, phosphorus or boron as raw materials. After mechanical grinding, the raw materials are subjected to a high-temperature pre-calcination treatment, followed by ball milling. After ball milling, the raw materials are dried and sieved, and then subjected to a second pre-calcination to transform them into cristobalite blocks. They are then transferred to a high-melting-point quartz tube for vacuum melting above the melting point of cristobalite, and then drawn into optical fibers. The process of secondary pre-calcining of the dried and sieved raw material powder is as follows: the temperature is slowly raised from room temperature to 200℃ to ensure that there is no organic solvent residue in the raw material, and then the temperature is raised to 1500℃~1650℃ at a rate of 1℃ / min~5℃ / min, and held for more than 2 hours to fully transform it into the cristobalite phase, and then cooled to room temperature with the furnace.

2. The method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials as described in claim 1, characterized in that: The inorganic compounds containing aluminum, germanium, phosphorus, or boron are: Al2O3, GeO2, P2O5, or B2O3.

3. The method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials as described in claim 1, characterized in that: The mechanically ground raw material is pre-fired at a high temperature of 1500℃~1650℃ for a holding time of more than 1 hour.

4. The method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials as described in claim 1, characterized in that: During ball milling, a volatile and non-toxic organic liquid is used to mix the raw material that has been pre-calcined at high temperature. The wet high-energy ball milling process lasts for 6 to 12 hours, with a rotation speed between 500 r / min and 1500 r / min.

5. The method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials as described in claim 4, characterized in that: The particle size after drying and sieving is between 10 nm and 500 nm.

6. The method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials as described in claim 1, characterized in that: The in-tube melting method uses a high-purity quartz cladding as the reaction vessel, and melting is carried out at 1715℃~1780℃ under a vacuum of 10. 2 Pa~10 5 Pa, melting time 1h to 4h, vacuum state maintained throughout.

7. The method for preparing rare earth-doped silica-based optical fibers using an in-tube melting method after pretreatment of raw materials as described in claim 1, characterized in that: The process of drawing optical fiber involves heating the drawing tower to 1850℃~1950℃, dropping the fiber head, and then pulling it to the auxiliary traction wheel for fiber traction. The fiber is drawn by controlling the bar feeding speed and the fiber drawing speed.

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