Preparation method of rare earth doped optical fiber preform capable of reducing rare earth ion escape
By combining the main lamp heating unit and the auxiliary lamp heating unit, the problem of rare earth ion escape was solved, and the laser efficiency of rare earth doped optical fiber was improved.
Patent Information
- Application Number
- CN202510340151.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2025-08-01
AI Technical Summary
During the fabrication of rare-earth-doped optical fibers, the escape of rare-earth ions is severe, resulting in a decrease in the concentration of rare-earth ions in the fiber core and a large refractive index depression, which affects the light output efficiency of the optical fiber.
The decomposition heating unit is a combination of a main lamp heating unit and an auxiliary lamp heating unit. The main lamp heating unit uses a seven-wick quartz torch, while the auxiliary lamp heating unit uses a single-wick metal torch, each responsible for different processes, in order to shorten the escape time of rare earth ions and control the escape of rare earth elements.
It effectively shortens the escape time of rare earth ions, increases the concentration of rare earth ion doping in the fiber core, reduces the refractive index depression in the fiber core, and improves the laser efficiency of rare earth doped active optical fibers.
Smart Images
Figure CN120398406A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for preparing a rare-earth doped optical fiber preform for reducing rare-earth ion escape, belonging to the technical field of optical fiber preform preparation. Background Art
[0002] Rare-earth doped active optical fiber refers to an optical fiber core doped with rare-earth elements (such as ytterbium, erbium, thulium, etc.), which can be used to manufacture fiber lasers and fiber amplifiers.
[0003] During the preparation of rare-earth doped active optical fiber, there is a phenomenon of rare-earth ion escape. As a result, the concentration of rare-earth ions in the center of the optical fiber core drops sharply, and the refractive index depression is large, affecting the light output efficiency of the optical fiber. Rare-earth ion escape mainly occurs during the vitrification process of the porous body. The longer the residence time of rare-earth ions in the high-temperature zone, the longer the escape time of rare-earth ions and the larger the ion concentration depression. There is an urgent need for a preparation method that can shorten the escape time of rare-earth ions during the vitrification process of the porous body in the preparation of rare-earth doped optical fiber preform, thereby maximizing the control of rare-earth element escape, increasing the doping concentration of rare-earth ions in the center of the optical fiber core, reducing the refractive index depression in the core center, and improving the laser efficiency of rare-earth doped active optical fiber. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a method for preparing a rare-earth doped optical fiber preform for reducing rare-earth ion escape, which shortens the escape time of rare-earth ions during the vitrification process of the porous layer, maximizes the control of rare-earth element escape, increases the doping concentration of rare-earth ions in the center of the optical fiber core, reduces the refractive index depression in the core center, and improves the laser efficiency of rare-earth doped active optical fiber.
[0005] The technical solution adopted by the present invention to solve the above problems is as follows: A method for preparing a rare-earth doped optical fiber preform for reducing rare-earth ion escape, the preparation method includes the following steps: Step 1: Substrate pre-treatment: Select a quartz substrate with appropriate size, and preheat, dry, and etch the substrate. Step 2: Deposit inner cladding: Deposit the inner cladding on the inner wall of the substrate through the main lamp heating unit. Step 3: Deposit porous layer: Deposit the porous layer on the inner cladding through the main lamp heating unit. Step 4: Soak the porous layer: Soak the substrate with the porous layer in a solution containing rare-earth elements and let it stand for a period of time. Step 5: Oxidation and drying: Introduce N2 into the substrate to volatilize the solvent containing rare-earth elements on the porous layer, then introduce O2 to oxidize the rare-earth elements doped in the porous layer in the substrate. After the oxidation is completed, introduce Cl2, and dry the porous layer in the substrate through the main lamp heating unit. Step 6: Vitrification of the porous layer: Vitrify the oxidized and dried porous layer through the auxiliary lamp heating unit; Step 7: Collapse: Collapse the vitrified transparent base tube into a transparent solid rod through the main lamp heating unit.
[0006] In step 2, the inner cladding is a Ge-Si layer. The deposition temperature of the inner cladding is 1900 - 2200 °C, the deposition flow rate of SiCl4 is 20 - 300 sccm, the flow rate of GeCl4 is 50 - 100 sccm, the deposition speed is 10 - 100 mm / min, and the number of deposition layers is 2 - 5 layers.
[0007] The main lamp heating unit includes a main lamp base, on which a plurality of quartz torches are provided. The plurality of quartz torches are symmetrically and arc-shapedly distributed; each quartz torch has a plurality of wicks.
[0008] In step 3, the porous layer is a silicon dioxide porous layer.
[0009] The deposition temperature of the porous layer is 1300 - 1700 °C, and the deposition flow rate is 100 - 400 sccm.
[0010] The solution containing rare earth elements in step 4 contains rare earth element halides with atomic numbers 57 - 71, the rare earth ion concentration is 0.2 - 0.5 mol / L, and the standing time is 30 min - 60 min.
[0011] In step 5, the temperature of the main lamp heating unit is controlled at 500 °C - 1200 °C, the O2 flow rate is 100 - 300 ml; the Cl2 flow rate is 100 - 300 ml.
[0012] The auxiliary lamp heating unit in step 6 includes an auxiliary lamp base, on which a plurality of metal torches are provided. The plurality of metal torches are symmetrically and arc-shapedly distributed, and each metal torch has a single wick.
[0013] In step 6, the temperature of the auxiliary lamp heating unit is controlled at 1900 °C - 2100 °C, and the H2 flow rate is 20 - 100 LPM.
[0014] In step 7, the collapse temperature is controlled at 2000 °C - 2300 °C, the collapse speed is 8 - 20 mm / min, and the H2 flow rate is 100 - 200 L / min.
[0015] Compared with the prior art, the advantages of the present invention are as follows: A method for preparing a rare earth-doped optical fiber preform for reducing rare earth ion escape, 1. The heating unit includes a main lamp heating unit and a sub-lamp heating unit, and the two heating units play different roles respectively. The main lamp heating unit uses a quartz blowtorch with seven wicks, which has the characteristic of a wide high-temperature zone and is suitable for processes such as loose body deposition, oxidative drying, and collapse. The sub-lamp heating unit uses a metal blowtorch with a single wick, which has the characteristics of a narrow high-temperature zone and concentrated temperature, and is suitable for use in the vitrification process of loose bodies. It can shorten the time of rare earth ion escape during the vitrification of loose bodies, control the escape of rare earth elements to the greatest extent, increase the doping concentration of rare earth ions in the center of the fiber core, reduce the refractive index depression in the center of the fiber core, and improve the laser efficiency of rare earth-doped active fibers.
[0016] 2. The metal blowtorch of the sub-lamp heating unit is made of stainless steel. It does not require water cooling, has a simple structure, and a small installation space. It can be installed together with the main lamp and used as another heat source for MCVD, and can be switched at any time according to the usage requirements. Description of the Drawings
[0017] Figure 1 It is a flowchart of a method for preparing a rare earth-doped fiber preform for reducing rare earth ion escape according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the main lamp heating unit; Figure 3 It is a schematic diagram of a seven-core quartz blowtorch; Figure 4 It is a schematic diagram of the sub-lamp heating unit; Figure 5 It is a schematic diagram of a single-core metal blowtorch; In the figure, 1 is the main lamp base, 2 is the quartz blowtorch, 3 is the quartz wick, 4 is the sub-lamp base, 5 is the metal blowtorch, and 6 is the metal wick. Detailed Embodiment
[0018] The present invention will be further described in detail below with reference to the embodiments of the drawings.
[0019] As Figure 1 shown, a method for preparing a rare earth-doped fiber preform for reducing rare earth ion escape in this embodiment includes the following steps: Step 1: Substrate tube pretreatment: Select a quartz substrate tube with appropriate dimensions, preheat, dry, and etch the substrate tube; eliminate impurities, bubbles, etc. on the inner wall of the substrate tube, and reduce the hydroxyl groups on the inner wall of the quartz substrate tube. Among them, the preheating temperature is 800 °C, and the preheating time is 5 min.
[0020] Step 2: Depositing the inner cladding layer: Deposit a Ge-Si layer on the inner wall of the base tube as the inner cladding layer through the main lamp heating unit; the Ge-Si layer is SiCl4 and GeCl4. The inner cladding layer can effectively reduce the core loss. By adjusting the flow rate of Ge, the refractive index height of the inner cladding layer is controlled to meet the NA design requirements of the core layer. The deposition temperature during the deposition of the inner cladding layer is 1900 - 2200 °C, the deposition flow rate of SiCl4 is 20 - 300 sccm, the deposition flow rate of GeCl4 is 50 - 100 sccm, the deposition speed is 10 - 100 mm / min, and the number of deposition layers is 2 - 5 layers.
[0021] As Figure 2 , 3 shown, the main lamp heating unit includes 6 quartz torches, and the 6 quartz torches are distributed in a symmetric circular arc. 7 lamp wicks are arranged in each quartz torch. The outer diameter of each quartz torch is 40 - 50 mm, and the outer diameter of each lamp wick is 5 - 8 mm.
[0022] Step 3: Depositing the porous layer: Deposit a silica porous layer on the inner cladding layer using the main lamp heating unit; the deposition temperature of the silica porous layer is 1300 - 1700 °C, and the deposition flow rate of SiCl4 is 100 - 400 sccm.
[0023] Step 4: Soaking the porous layer: Soak the base tube with the porous layer in a solution containing rare earth elements and let it stand for 30 min - 60 min; the solution containing rare earth elements contains Yb or Er elements, and the concentration of rare earth ions is 0.2 - 0.5 mol / L.
[0024] Step 5: Oxidation and drying: Pass N2 into the base tube to volatilize the solvent on the porous layer, and then pass O2 with a flow rate of 100 - 300 ml to oxidize the rare earth elements doped in the porous layer in the base tube. After the oxidation is completed, pass dry Cl2 with a flow rate of 100 - 300 ml to dry the porous layer in the base tube. The main lamp heating unit is used as the heat source during drying, and the temperature of the main lamp heating unit is controlled at 500 °C - 1200 °C.
[0025] Step 6: Vitrification of the porous layer: Vitrify the porous layer after oxidation and drying through the auxiliary lamp heating unit. The vitrification temperature is controlled at 1900 °C - 2100 °C, and the H2 flow rate is 20 - 100 LPM.
[0026] As Figure 4 , 5As shown, the auxiliary lamp heating unit includes 6 metal torches, which are distributed in a symmetric circular arc. The metal torches are made of stainless steel, and each metal torch has 1 wick; the outer diameter of the metal torch is 40 - 50 mm, and the outer diameter of the wick is 5 - 8 mm. This kind of metal torch is independently composed and does not require a cooling system like a conventional quartz torch. Therefore, the entire auxiliary lamp heating unit has a simple structure and a small installation space. The main lamp heating unit and the auxiliary lamp heating unit are installed together on the MCVD lathe. The distance between the main lamp heating unit and the auxiliary lamp heating unit is 80 - 100 mm, and the auxiliary lamp heating unit is located on the left side of the main lamp heating unit; it can be switched at any time according to the usage requirements.
[0027] Step 7: Collapse: Collapse the vitrified transparent substrate tube into a transparent solid rod through the main lamp heating unit; the collapse temperature is controlled at 2000°C - 2300°C, the collapse speed is 8 - 20 mm / min, and the H2 flow rate is 100 - 200 L / min.
[0028] The heating unit is divided into a main lamp heating unit and an auxiliary lamp heating unit, and the two heating units play different roles respectively. The main heating unit uses a quartz torch with seven wicks, which has the characteristic of a wide high-temperature zone and is suitable for processes such as depositing a loose body layer, oxidation drying, and collapse. The auxiliary heating unit uses a metal torch with a single wick, which has the characteristics of a narrow high-temperature zone and concentrated temperature, and is suitable for use in the vitrification process of the loose body layer. It can shorten the time for rare earth ions to escape during the vitrification process of the loose body layer, control the escape of rare earth elements to the greatest extent, increase the doping concentration of rare earth ions in the center of the fiber core, reduce the refractive index depression in the center of the core, and improve the laser efficiency of the rare earth-doped active fiber. The auxiliary heating unit is made of metal stainless steel, does not require water cooling, has a simple structure and a small installation space, can be installed together with the main heating unit, and is used as another heat source for the MCVD, and can be switched at any time according to the usage requirements.
[0029] In addition to the above embodiments, the present invention also includes other implementation manners. Any technical solutions formed by equivalent transformation or equivalent substitution shall fall within the protection scope of the claims of the present invention.
Claims
1. A method for preparing a rare-earth doped fiber preform for reducing the escape of rare-earth ions, characterized in that: The preparation method includes the following steps: Step 1: Substrate tube pretreatment: Select a quartz substrate tube with appropriate dimensions, and preheat, dry, and etch the substrate tube; Step 2: Deposit the inner cladding layer: Deposit the inner cladding layer on the inner wall of the substrate tube through the main lamp heating unit; Step 3: Deposit the porous layer: Deposit the porous layer on the inner cladding layer through the main lamp heating unit; Step 4: Immerse the porous layer: Immerse the substrate tube with the porous layer in a solution containing rare earth elements and let it stand for a period of time; Step 5: Oxidation and drying: Introduce N2 into the substrate tube to volatilize the solvent containing rare earth elements on the porous layer, then introduce O2 to oxidize the rare earth elements doped in the porous layer in the substrate tube. After the oxidation is completed, introduce Cl2, and dry the porous layer in the substrate tube through the main lamp heating unit; Step 6: Vitrification of the porous layer: Vitrify the completed oxidized and dried porous layer through the auxiliary lamp heating unit; Step 7: Collapse: Collapse the vitrified transparent substrate tube into a transparent solid rod through the main lamp heating unit.
2. The preparation method of a rare-earth doped fiber preform for reducing rare-earth ion escape according to claim 1, characterized in that: In Step 2, the inner cladding layer is a Ge-Si layer. The deposition temperature of the inner cladding layer is 1900 - 2200 °C, the deposition flow rate of SiCl4 is 20 - 300 sccm, the flow rate of GeCl4 is 50 - 100 sccm, the deposition speed is 10 - 100 mm / min, and the number of deposition layers is 2 - 5 layers.
3. The preparation method of a rare earth doped fiber preform for reducing rare earth ion escape according to claim 1, characterized in that: The main lamp heating unit includes a main lamp base, and a plurality of quartz torches are provided on the main lamp base. The plurality of quartz torches are symmetrically distributed in an arc shape; each quartz torch has a plurality of wicks.
4. The preparation method of a rare-earth doped fiber preform for reducing rare-earth ion escape according to claim 1, characterized in that: In Step 3, the porous layer is a silicon dioxide porous layer.
5. The preparation method of a rare earth doped fiber preform for reducing the escape of rare earth ions according to claim 4, characterized in that: The deposition temperature of the porous layer is 1300 - 1700 °C, and the deposition flow rate is 100 - 400 sccm.
6. The preparation method of a rare earth doped fiber preform for reducing rare earth ion escape according to claim 1, characterized in that: In the solution containing rare earth elements in Step 4, it contains rare earth element halides with atomic numbers 57 - 71, the rare earth ion concentration is 0.2 - 0.5 mol / L, and the standing time is 30 min - 60 min.
7. The preparation method of a rare earth doped fiber preform for reducing rare earth ion escape according to claim 1, characterized in that: In Step 5, the temperature of the main lamp heating unit is controlled at 500 °C - 1200 °C, the O2 flow rate is 100 - 300 ml; the Cl2 flow rate is 100 - 300 ml.
8. The preparation method of a rare-earth doped fiber preform for reducing rare-earth ion escape according to claim 1, characterized in that: The auxiliary lamp heating unit in Step 6 includes an auxiliary lamp base, and a plurality of metal torches are provided on the auxiliary lamp base. The plurality of metal torches are symmetrically distributed in an arc shape, and each metal torch has a single wick.
9. The method for preparing a rare earth doped optical fiber preform for reducing rare earth ion escape according to claim 8, wherein: In Step 6, the temperature of the auxiliary lamp heating unit is controlled at 1900 °C - 2100 °C, and the H2 flow rate is 20 - 100 LPM.
10. The preparation method of a rare earth doped fiber preform for reducing the escape of rare earth ions according to claim 1, characterized in that: In Step 7, the collapse temperature is controlled at 2000 °C - 2300 °C, the collapse speed is 8 - 20 mm / min, and the H2 flow rate is 100 - 200 L / min.