Method for preparing rare earth doped glass optical fiber through sol-gel method and in-tube melting method

Abstract

The invention discloses a preparation process of a doped optical fiber, which is particularly suitable for a rare earth gain optical fiber. A sol precursor is mainly adopted to be mixed with all components in a liquid environment, and a xerogel block is prepared through high-temperature rapid drying. And carrying out heat preservation and heat treatment on the xerogel at a relatively low temperature through subsequent two melting processes to prepare uniform bubble-free rare earth ion doped quartz glass, crushing the glass, carrying out ball milling, and carrying out second high-temperature heat treatment to obtain powdery glass powder. And melting and drawing in a high-temperature tube in a vacuumized graphite furnace to obtain the transparent bubble-free optical fiber. In the process, the glass powder prepared in advance by adopting a sol-gel method improves the doping uniformity and reduces the melting point of the fiber core, and the optical fiber is drawn by adopting the in-tube melting method, so that defects easily caused by machining by adopting a sleeve method are avoided; the glass powder prepared in advance instead of the raw materials of the fiber core glass is fused in the tube, so that the uniformity of the fiber core glass is improved; by melting and drawing the optical fiber in the vacuum tube, the defects such as bubbles on fiber core glass and a core cladding interface are eliminated, so that the loss of the optical fiber is reduced.

Description

Technical Field

[0001] This invention relates to the fabrication process of doped optical fibers, and more particularly to a method for fabricating rare-earth ion-doped glass optical fibers. Background Technology

[0002] Doped glass fibers are core components of fiber lasers, fiber amplifiers, and other similar devices. Currently, the most commonly used rare-earth-doped fibers use quartz glass as the matrix material. The fabrication technology for quartz glass fibers primarily employs a modified chemical vapor deposition (MCVD) method, first preparing an fiber preform, and then drawing the preform into an optical fiber. However, the MCVD method is expensive and has a long production cycle. Furthermore, due to the limited uniformity of mixing of components during the core deposition process, the core size is generally limited, and the doping concentration is relatively low.

[0003] Optical fiber fabrication based on the sol-gel method typically begins with the preparation of a core glass using the sol-gel method. This core glass is then mechanically processed into a core rod glass, which is then nested with a hollow quartz tube to form an optical fiber preform. The optical fiber is subsequently drawn onto a drawing tower. However, the mechanical processing of the core glass rod is prone to defects, resulting in high optical fiber loss.

[0004] To address the above problems, this invention proposes a method for preparing rare earth ion-doped glass optical fibers via sol-gel method and in-tube melting method, in order to solve the problems of low doping concentration, low purity, limited core size, and high loss caused by machining defects, thereby realizing the preparation of high-concentration, low-loss rare earth ion-doped glass optical fibers. Summary of the Invention

[0005] The technical solution of this invention is as follows: A method for preparing rare earth-doped glass optical fibers via sol-gel method and in-tube melting method, comprising the following steps: (1) Sol preparation: The precursor is heated in a water bath and mixed evenly; (2) The prepared sol is placed in an oven and dried at high temperature to form a dry gel block. (3) The dry gel block is pre-fired in a box furnace. First, the temperature is slowly increased at a rate of 20-30 degrees per hour from 200 to 500 degrees to remove moisture and most organic matter. Then, the temperature is increased to 900-1100 degrees per hour from 100-200 degrees and held for 1-4 hours to densify the glass by high temperature viscous flow, thus removing residual organic matter. (4) After crushing the glass, ball milling is performed to further reduce the melting point and to ball mill the raw material into particles with a size of 100nm-5 micrometers. (5) The glass powder is subjected to secondary heat treatment in a box furnace. Before reaching 1000 degrees, the temperature is increased at a rate of 3-5 degrees per minute. Above 1000 degrees, the temperature is increased at a rate of 1-3 degrees to 1600-1750 degrees and held for 1-4 hours. (6) The glass powder after secondary heat treatment is ball-milled and sieved to obtain doped glass powder raw material. (7) Pour the glass powder into a hollow quartz tube with one end closed, install it on the drawing tower, evacuate the quartz tube, and then heat it to 1600-1800 degrees and keep it at that temperature for 1-4 hours. (8) Heat the temperature to 1800-1900 degrees and wait for the material head to fall. Pull it to the auxiliary traction wheel, and use the program to control the feeding and traction speed to pull the optical fiber. Vacuum treatment is carried out inside the quartz tube throughout the process.

[0006] The key point of this invention lies in first preparing highly uniform rare-earth-doped non-static glass using a sol-gel method. The glass is then ball-milled once, followed by high-temperature treatment, and then ball-milled again to obtain uniformly doped core glass powder. This powder is then drawn into optical fibers via vacuum melting within a tube. Compared to the traditional sol-gel method for fiber fabrication, this method eliminates the need for core rod machining, reducing fiber loss caused by machining. Furthermore, compared to the traditional in-tube melting method, using the doped glass powder obtained directly from the sol-gel process as raw material reduces fiber loss caused by core glass inhomogeneity during melting. Attached Figure Description Appendix Figure 1 This is a process flow diagram of the present invention; Appendix Figure 2 The images include wet gels, dry gels, gel powders, optical fiber tips, and microscopic photographs and pictures of optical fibers. Detailed Implementation

[0007] The present invention will be further described below with reference to its implementation, but this should not be construed as limiting the scope of protection of the present invention.

[0008] A method for preparing rare-earth-doped glass optical fibers via sol-gel method and in-tube melting method includes the following steps: (1) According to the designed glass composition SiO2-Al2O3-Yb2O3, the raw materials used are tetraethyl silicate, aluminum nitrate nonahydrate, and ytterbium oxide. Weigh each raw material according to the composition. In this case, the total amount of glass oxide is 30g. (2) Place the prepared sol in an oven and dry it at 75 degrees for 2 days before taking it out. (3) Perform the first heat treatment, raising the temperature at 200-500 degrees Celsius at a rate of 15 degrees Celsius per hour and then at a rate of 150 degrees Celsius per hour to 1100 degrees Celsius and holding for 1 hour. (4) Crush the glass block in an agate mortar and grind it in a ball mill. The grinding time is 2 hours. (5) Perform a second heat treatment. Before reaching 1000 degrees, use a heating rate of 5 degrees per minute. After reaching 1000 degrees, use a heating rate of 3 degrees per minute to reach 1750 degrees and hold for 2 hours. (6) After the glass powder is ball-milled and sieved twice, it is poured into a hollow quartz tube, installed on the drawing tower, and heated to 1780 degrees Celsius under vacuum for two hours. (7) When heated to 1820 degrees, the material softens and falls off under the action of gravity. The auxiliary traction wheel is pulled, and the fiber of the required size is drawn by controlling the feeding rod and traction speed.

Claims

1. A method of making a rare earth doped glass optical fiber via a sol-gel process and an in-tube melting process, characterized in that The sol-gel method is used to achieve molecular uniformity and high purity under liquid conditions. The organic matter is removed by oven drying, a first heat treatment, ball milling, a second heat treatment, and then a second ball milling. The powder is obtained after the second heat treatment. The powder is combined with a hollow quartz tube to form a fiber preform, which is then vacuumed and melted at high temperature to draw the fiber.

2. The method of claim 1, wherein the method of making a rare earth doped glass optical fiber via a sol-gel process and an in-tube melting process is characterized by: The core glass powder obtained by the sol-gel method is subjected to a second heat treatment and ball milling process. The first heat treatment is at a temperature of 200 to 500, with a temperature rising rate of 20-30 degrees per hour, to remove moisture and most of the organic matter. Then, the temperature is raised to 900-1100 at a rate of 100-200 degrees per hour for 1-4 hours. The second heat treatment is at a temperature of 1000 degrees, with a temperature rising rate of 3-5 degrees per minute before 1000 degrees, and a temperature rising rate of 1-3 degrees per minute after 1000 degrees, to a temperature of 1600-1750 degrees for 1-4 hours. The particle size of the glass powder after the first ball milling is between 100-1500 nm. The particle size of the glass powder after the second ball milling is between 0.5 to 5 microns.

3. The method of claim 1, wherein the method of making a rare earth doped glass optical fiber via a sol-gel process and an in-tube melting process is characterized by: The core raw material for the in-tube melting is highly uniform glass powder obtained by the sol-gel method, including but not limited to, and is not limited to, the glass component raw materials.

4. The method of claim 1, wherein the method of making a rare earth doped glass optical fiber via a sol-gel process and an in-tube melting process is characterized by: The vacuuming is performed while the tube is being melted to remove air bubbles from the core glass in the tube, the vacuum degree being 10 2 -10 -5 Pa.

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