A method for improving the concentricity deviation of a horizontal sleeve process of a fluorine-doped quartz tube

Abstract

This invention discloses a method for improving the concentricity deviation of a horizontal sleeve in a fluorinated quartz tube, comprising the following steps: Preparation of a positioning component: welding a quartz ring with a central hole to a tail tube; Etching of the fluorinated quartz tube: welding the tail end of the fluorinated quartz tube to the quartz ring in the positioning component, and etching the fluorinated quartz tube; Treatment of an octagonal mother rod: first cutting a groove at one end of the octagonal mother rod, then welding the air inlet pipe to the grooved end of the octagonal mother rod, welding a handle to the other end of the octagonal mother rod, and then calcining the surface of the octagonal mother rod; Assembly: horizontally inserting the octagonal mother rod into the fluorinated quartz tube, and fixing the handle welded to the octagonal mother rod into the central hole of the quartz ring in the positioning component; Secondary etching; Collapse. This method can reduce the concentricity deviation between the octagonal mother rod and the fluorinated quartz tube, and ensure that there are no impurities between the fluorinated quartz tube and the octagonal mother rod, effectively reducing cladding loss.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber technology, and specifically relates to a method for improving the concentricity deviation in the horizontal sleeve process of fluorine-doped quartz tubes. Background Technology

[0002] Fiber lasers are now widely used in industrial processing, with fiber being the core component. Currently, fiber lasers commonly use double-clad fibers, with an inner cladding of pure silica glass and an outer cladding of low-refractive-index coating. The high refractive index difference between the inner and outer claddings is beneficial for improving pump light absorption, and this is often used in kilowatt-level lasers. However, as laser output power increases, the outer cladding coating needs to withstand higher heat, limiting the increase in output power of high-power fibers. Chinese patent CN 110187437A discloses a triple-clad fiber laser, which can solve the problems of poor stability and low reliability caused by using double-clad passive fibers.

[0003] The high-concentration fluorine-doped quartz tube sleeve is a key technological challenge in the fabrication of triple-clad optical fiber preforms. At high temperatures, the fluorine in the doped layer readily volatilizes, and the resulting gas easily remains between the fluorine-doped quartz layer and the octagonal preform, forming fluorine bubbles. These bubbles become scattering points after the fiber is drawn, and under high-power conditions, they can easily become damage points, significantly reducing the power the fiber can withstand. Chinese Patent Publication No. CN111025459A discloses a method for fabricating a high-concentration fluorine-doped quartz tube sleeve, specifically a scheme to eliminate fluorine bubbles. This involves depositing a pure silicon layer before the sleeve collapses. This pure silicon layer deposition can be performed in advance during the fluorine-doped quartz tube fabrication process, thus solving the problem of fluorine volatilization and bubble formation during high-temperature processing.

[0004] Conventional quartz tube sleeves employ a vertical sleeve process. However, vertical sleeves often utilize induction furnaces or resistance furnaces, which cannot completely remove impurities at the interface between the quartz tube and the mother rod, resulting in significant losses at both ends. The horizontal sleeve process for fluorine-doped quartz tubes presents another challenge: a large concentricity deviation between the octagonal mother rod and the fluorine-doped quartz tube. Chinese patent CN111025459A proposes pre-setting collapse support points on the fluorine-doped quartz tube before the collapse of the octagonal mother rod and the fluorine-doped quartz tube. This method ensures concentricity through these collapse support points. However, since these support points are pre-fitted to the octagonal mother rod after sleeve installation but before collapse, air circulation is difficult, and internal polishing of the fluorine-doped quartz tube is challenging. Furthermore, the fitted area is prone to mirror-like surfaces, which can easily crack or even break during collapse due to temperature changes. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for improving the concentricity deviation in the horizontal sleeve process of fluorine-doped quartz tubes. This method can reduce the concentricity deviation between the octagonal mother rod and the fluorine-doped quartz tube, ensuring the concentricity of optical fiber products and guaranteeing the absence of impurities between the fluorine-doped quartz tube and the octagonal mother rod, thereby effectively reducing cladding loss.

[0006] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0007] A method for improving the concentricity deviation in the manufacturing process of fluorine-doped quartz tube horizontal sleeves includes the following steps:

[0008] (1) Preparation of positioning components: Weld a tail tube to one end of a quartz ring with a central hole. The center of the quartz ring is concentric with the center of the tail tube, and the ring body of the quartz ring also has a vent hole.

[0009] (2) Etching of fluorine-doped quartz tube: Weld the tail end of the fluorine-doped quartz tube to the quartz ring in the positioning assembly, and perform inner wall etching on the fluorine-doped quartz tube.

[0010] (3) Octagonal mother rod processing: First, cut grooves on the eight faces of one end of the octagonal mother rod, then weld the inlet of the air inlet pipe to the end of the octagonal mother rod with the groove, the groove serving as a reserved air inlet hole. Weld a handle to the other end of the octagonal mother rod, and then burn the surface of the octagonal mother rod to remove surface impurities.

[0011] (4) Assembly: Insert the octagonal mother rod after step (3) into the fluorine-doped quartz tube horizontally, and fix the handle welded on the octagonal mother rod into the center hole of the quartz ring in the positioning assembly to complete the horizontal assembly process of the fluorine-doped quartz tube and the octagonal mother rod. After assembly, weld the air inlet pipe to the head end of the fluorine-doped quartz tube.

[0012] (5) Secondary etching: Gas is introduced between the fluorine-doped quartz tube and the octagonal mother rod through the air inlet pipe and the groove of the octagonal mother rod to perform secondary etching. The introduced gas is discharged through the vent hole of the quartz ring.

[0013] (6) Collapse: The fluorine-doped quartz tube is heated by an oxyhydrogen torch so that it collapses and wraps around the octagonal mother rod.

[0014] Furthermore, a pure silicon layer is pre-deposited on the inner wall of the fluorine-doped quartz tube.

[0015] Further, the etching process of the fluorine-doped quartz tube in step (2) is as follows: a vent pipe is welded to the head end of the fluorine-doped quartz tube, and the tail end of the fluorine-doped quartz tube is welded to the quartz ring in the positioning component. 1000 sccm of oxygen, 500 sccm of helium and 100 sccm of carbon tetrafluoride are introduced into the fluorine-doped quartz tube through the vent pipe, and the pressure at the tail end is controlled at about 85 Pa. The tube is heated for etching. After etching and cooling, high-pressure nitrogen is introduced through the central hole of the quartz ring for purging. Finally, the vent pipe is cut off.

[0016] Furthermore, in step (3), the distance between the welding point between the air intake pipe and the octagonal mother rod and the groove is 0.5 cm.

[0017] Furthermore, the length of the handle is designed based on the total length of the fluorine-doped quartz tube and the quartz ring, as well as the length of the octagonal mother rod.

[0018] Furthermore, in step (3), a hydrogen-oxygen high-temperature flame is used for calcination, with a calcination temperature of 1900-2000℃ and a hydrogen-oxygen flow ratio of 2.5:1.

[0019] Furthermore, the secondary etching process in step (5) is as follows: 200 sccm of oxygen, 200 sccm of helium, and 100 sccm of carbon tetrafluoride are introduced through the air inlet pipe welded to the octagonal mother rod, and the pressure at the tail pipe is controlled at about 40 Pa. The gas enters between the octagonal mother rod and the fluorine-doped quartz tube through the groove of the octagonal mother rod, and is heated for secondary etching. After the etching is completed, the waste gas is discharged through the vent hole on the quartz ring.

[0020] Furthermore, in step (6), the fluorinated quartz tube position corresponding to the welding point between the octagonal mother rod and the handle rod is first subjected to fixed-point collapse. After the fixed-point collapse is completed, the tube is gradually heated and collapsed along the length of the fluorinated quartz tube.

[0021] Furthermore, during point collapse, oxygen is introduced through the intake pipe at a flow rate of 500 sccm, and the pressure at the tailpipe is 45 Pa.

[0022] Furthermore, in step (6), the hydrogen flow rate of the hydrogen-oxygen torch is 90-100 slm, and the moving speed of the hydrogen-oxygen torch is 2-5 mm / min.

[0023] The beneficial effects of this invention are:

[0024] This invention welds the intake pipe to one end of an octagonal mother rod, and a handle rod to the other end of the octagonal mother rod. A special positioning component is welded to the tail end of a fluorine-doped quartz tube. The quartz ring in the positioning component is concentric with the fluorine-doped quartz tube. During assembly of the octagonal mother rod and the fluorine-doped quartz tube, the handle rod is fixed to the central hole of the quartz ring, and the head end of the fluorine-doped quartz tube is welded to the intake pipe. This method allows for the assembly and positioning of the fluorine-doped quartz tube and the octagonal mother rod, ensuring the proper alignment of the fluorine-doped quartz tube with the octagonal mother rod. The concentricity of the rods avoids the softening and twisting problem of the fluorinated quartz tube during collapse. It also eliminates the need to pre-set collapse support points on the fluorinated quartz tube, avoiding premature collapse of the mirror surface and preventing mirror cracking caused by temperature changes during collapse. Furthermore, due to the cooperation between the positioning component with the quartz ring and the rod, the octagonal mother rod will not wobble due to high-temperature softening when welding the fluorinated quartz tube to the air inlet pipe, ensuring the concentricity of the octagonal mother rod and the fluorinated quartz tube.

[0025] This invention welds the air inlet pipe to one end of an octagonal mother rod and a fluorine-doped quartz tube, and creates grooves on each of the eight faces of the octagonal mother rod. This allows for assembly and positioning using the air inlet pipe and a positioning assembly with a quartz ring, while simultaneously enabling ventilation through the grooves. This facilitates secondary etching of the gap between the fluorine-doped quartz tube and the octagonal mother rod after assembly, ensuring the absence of impurities between them and effectively reducing fiber cladding loss. The vent holes on the quartz ring allow for exhaust, ensuring the secondary etching process and removing residual waste gas between the fluorine-doped quartz tube and the octagonal mother rod, reducing the generation of fluorine bubbles. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a method for improving the concentricity deviation of a fluorine-doped quartz tube horizontal sleeve process according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of the quartz ring in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of the fluorine-doped quartz composite tube formed by the present invention.

[0029] Figure 4 This is a schematic diagram of the 1095nm cladding loss of the fluorine-doped quartz composite tube formed in an embodiment of the present invention.

[0030] Figure 5 This is a cross-sectional diagram showing the refractive index distribution of the fluorine-doped quartz composite tube after drawing, as shown in the embodiment of the present invention.

[0031] In the figure, 1: fluorine-doped quartz tube; 2: octagonal mother rod; 21: groove; 3: tail tube; 4: air inlet pipe; 5: handle; 6: quartz ring; 61: center hole; 62: vent hole. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, the present invention provides a preferred embodiment of a method for improving the concentricity deviation in the manufacturing process of fluorine-doped quartz tube horizontal sleeves, which includes the following steps:

[0034] (2) Preparation of positioning components: A tail tube 3 is welded to one end of a quartz ring 6 with a central hole, and the center of the quartz ring 6 is concentric with the center of the tail tube 3. The inner diameter of the central hole 61 of the quartz ring 6 is 16 mm, and two 5 mm vent holes 62 are symmetrically provided on the ring body of the quartz ring 6; the specifications of the tail tube 3 are an outer diameter of 40 mm * wall thickness of 3 mm, and a tail tube length of at least 500 mm.

[0035] (2) Etching of fluorine-doped quartz tube: The inner wall of the fluorine-doped quartz tube pre-deposited with a pure silicon layer is etched in advance to remove impurities inside the tube; specifically, a vent pipe is welded to the left end of the fluorine-doped quartz tube 1 with an outer diameter of 38 mm and an inner diameter of 30 mm, and the right end is welded to the quartz ring 6 in the positioning assembly, and then it is horizontally welded on an MCVD lathe; 1000 sccm (ml per minute) of oxygen, 500 sccm of helium and 100 sccm of carbon tetrafluoride are introduced into the fluorine-doped quartz tube 1, and the pressure at the tail tube is controlled at about 85 Pa. The tube is etched clean at high temperature; the specific etching conditions are: etching temperature of 1750℃, hydrogen flow rate of 85 slm, and flame torch speed of 80 mm / min; at the same time as etching, the fluorine-doped quartz tube can be checked for the generation of fluorine bubbles at high temperature to prevent the subsequent fluorine-doped quartz tube from being scrapped due to excessive fluorine bubbles. After the fluorinated quartz tube is cooled, it is removed from the MCVD lathe. A high-pressure nitrogen gas tube is inserted into the center hole of the quartz ring of the specially designed positioning component to purge with high-pressure nitrogen gas. Then, the venting tube is cut off with a cutting machine. The purpose of venting at the tail end is to minimize the entry of impurities such as crushed quartz slag. After treatment, the fluorinated quartz tube 1 is sealed with a film for later use.

[0036] (3) Octagonal mother rod processing: First, cut 1cm long grooves 21 on each of the eight faces of one end of the octagonal mother rod 2. Then, weld the inlet of the air inlet pipe 4 to the end of the octagonal mother rod 2 with grooves. Each welding point is 0.5cm away from the groove. The groove 21 serves as a reserved air inlet hole. Weld a handle 5 with a diameter of 15.4-15.6mm and a length of at least 300mm to the other end of the octagonal mother rod 2. Then, use a hydrogen-oxygen high-temperature flame to burn the surface of the octagonal mother rod 2 to remove surface impurities. The burning temperature is 1900-2000℃ and the hydrogen-oxygen flow ratio is 2.5:1.

[0037] (4) Assembly: After fixing the octagonal mother rod 2, which has been processed in step (3), onto the left chuck of the MCVD machine tool, fix the fluorinated quartz tube 1 with the tail tube 3 and quartz ring 6 onto the right chuck of the machine tool. Insert the octagonal mother rod 2 horizontally into the fluorinated quartz tube 1, and fix the handle 5 welded on the octagonal mother rod 2 into the center hole 61 of the quartz ring 6. This completes the horizontal assembly process of the fluorinated quartz tube 1 and the octagonal mother rod 2. After assembly, weld the end of the air inlet pipe 4 to the end of the fluorinated quartz tube 1. During welding, the handle 5 mates with the center hole 61 of the quartz ring 6. The small gap of 0.2-0.3mm between the handle 5 and the center hole 61 of the quartz ring 6 ensures that the octagonal mother rod 2 and the fluorinated quartz tube 1 are on the same center line, thereby ensuring concentricity.

[0038] It should be noted that the length of the handle is designed based on the total length of the fluorine-doped quartz tube and the quartz ring, as well as the length of the octagonal mother rod, to ensure that the handle can cooperate with the positioning component with the quartz ring, and that the left end of the fluorine-doped quartz tube can be close to the end of the air inlet pipe after assembly, so as to facilitate welding.

[0039] (5) Secondary Etching: Gas is introduced into the space between the fluorinated quartz tube 1 and the octagonal mother rod 2 through the inlet pipe 4 and the groove 21 of the octagonal mother rod 2 for secondary etching. The introduced gas is discharged through the vent hole 62 of the quartz ring 6. The specific process of secondary etching is as follows: 200 sccm of oxygen, 200 sccm of helium, and 100 sccm of carbon tetrafluoride are introduced through the inlet pipe 4 welded to the octagonal mother rod 2, and the pressure at the tail pipe is controlled at about 40 Pa. The gas enters the space between the octagonal mother rod 2 and the fluorinated quartz tube 1 through the groove 21 of the octagonal mother rod 2, and is heated for secondary etching. The secondary etching temperature is 1850℃, the hydrogen flow rate is 80 slm, and the torch speed is 50 mm / min. After etching, the waste gas is discharged through the vent hole 62 on the quartz ring 6. After etching, heating is stopped, and pure oxygen is introduced to purge for 10 minutes to remove the carbon tetrafluoride in the tube.

[0040] (6) Collapse: The fluorinated quartz tube 1 is heated using an oxyhydrogen torch to cause it to collapse and wrap around the octagonal mother rod 2. During collapse, the fluorinated quartz tube is first collapsed at the location corresponding to the welding point between the octagonal mother rod 2 and the handle rod 5 (marked as A in the figure). After the point collapse is completed, the tube is gradually heated and collapsed from right to left along its length. During point collapse, oxygen is introduced through the inlet pipe 4 at a flow rate of 500 sccm, and the pressure at the tail pipe is 45 Pa. During the collapse from right to left, the pressure at the inlet pipe is 10 Pa. The pressure is controlled by PID control. Positive pressure collapse ensures that the thickness difference of the fluorinated layer after the fluorinated quartz tube is wrapped around the octagonal mother rod is small, ensuring that the outermost ring is circular. During the collapse, the hydrogen flow rate of the oxyhydrogen torch is 90-100 slm, and the moving speed of the oxyhydrogen torch is 2-5 mm / min.

[0041] After the collapse is complete, the positioning component with the quartz ring, the air inlet pipe, and the handle are cut off. The resulting fluorine-doped quartz composite tube is then ground and polished to obtain the desired result. Figure 3 The finished product shown. Figure 4 A schematic diagram of the 1095nm cladding loss of the fluorine-doped quartz composite tube formed in this embodiment is shown. Figure 5 The diagram shows the refractive index profile of the fluorine-doped quartz composite tube formed in this embodiment after wire drawing. Figure 4 It can be seen that the cladding loss of the fluorine-doped quartz composite tube prepared by the method of the present invention is small, with a cladding loss of about 5 dB / km at 1095 nm; at the same time, the concentricity deviation is small, with the concentricity deviation between the octagonal mother rod and the fluorine-doped quartz tube being less than 2 μm.

[0042] 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 invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0043] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider 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 improving the concentricity deviation in the manufacturing process of fluorine-doped quartz tube horizontal sleeves, characterized in that, Includes the following steps: (1) Preparation of positioning components: Weld a tail tube to one end of a quartz ring with a central hole. The center of the quartz ring is concentric with the center of the tail tube, and the ring body of the quartz ring also has a vent hole. (2) Etching of fluorine-doped quartz tube: Weld the tail end of the fluorine-doped quartz tube to the quartz ring in the positioning assembly, and perform inner wall etching on the fluorine-doped quartz tube. (3) Octagonal mother rod processing: First, cut grooves on the eight faces of one end of the octagonal mother rod, then weld the inlet of the air inlet pipe to the end of the octagonal mother rod with the groove, the groove serving as a reserved air inlet hole. Weld a handle to the other end of the octagonal mother rod, and then burn the surface of the octagonal mother rod to remove surface impurities. (4) Assembly: Insert the octagonal mother rod after step (3) into the fluorine-doped quartz tube horizontally, and fix the handle welded on the octagonal mother rod into the center hole of the quartz ring in the positioning assembly to complete the horizontal assembly process of the fluorine-doped quartz tube and the octagonal mother rod. After assembly, weld the air inlet pipe to the head end of the fluorine-doped quartz tube. (5) Secondary etching: Gas is introduced between the fluorine-doped quartz tube and the octagonal mother rod through the air inlet pipe and the groove of the octagonal mother rod to perform secondary etching. The introduced gas is discharged through the vent hole of the quartz ring. (6) Collapse: The fluorine-doped quartz tube is heated by an oxyhydrogen torch so that it collapses and wraps around the octagonal mother rod.

2. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, The inner wall of the fluorine-doped quartz tube is pre-deposited with a layer of pure silicon.

3. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, The etching process of the fluorine-doped quartz tube in step (2) is as follows: a vent pipe is welded to the head end of the fluorine-doped quartz tube, and the tail end of the fluorine-doped quartz tube is welded to the quartz ring in the positioning assembly. 1000 sccm of oxygen, 500 sccm of helium and 100 sccm of carbon tetrafluoride are introduced into the fluorine-doped quartz tube through the vent pipe, and the pressure at the tail end is controlled at about 85 Pa. The tube is heated for etching. After etching and cooling, high-pressure nitrogen is introduced through the central hole of the quartz ring for purging. Finally, the vent pipe is cut off.

4. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, In step (3), the distance between the welding point between the air intake pipe and the octagonal mother rod and the groove is 0.5cm.

5. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, The length of the handle is designed based on the total length of the fluorine-doped quartz tube and the quartz ring, as well as the length of the octagonal mother rod.

6. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, In step (3), a hydrogen-oxygen high-temperature flame is used for calcination at a temperature of 1900-2000℃ and a hydrogen-oxygen flow ratio of 2.5:

1.

7. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, The secondary etching process in step (5) is as follows: 200 sccm of oxygen, 200 sccm of helium and 100 sccm of carbon tetrafluoride are introduced through the air inlet pipe welded to the octagonal mother rod, and the pressure at the tail pipe is controlled at about 40 Pa. The gas enters between the octagonal mother rod and the fluorine-doped quartz tube through the groove of the octagonal mother rod, and is heated for secondary etching. After the etching is completed, the waste gas is discharged through the vent hole on the quartz ring.

8. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 1, characterized in that, In step (6), the fluorinated quartz tube position corresponding to the welding point between the octagonal mother rod and the handle rod is first subjected to fixed-point collapse. After the fixed-point collapse is completed, the tube is gradually heated and collapsed along the length of the fluorinated quartz tube.

9. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 8, characterized in that, During point collapse, oxygen is introduced through the intake pipe at a flow rate of 500 sccm, and the pressure at the tailpipe is 45 Pa.

10. The method for improving the concentricity deviation in the horizontal sleeve process of a fluorine-doped quartz tube according to claim 8, characterized in that, In step (6), the hydrogen flow rate of the hydrogen-oxygen torch is 90-100 slm, and the moving speed of the hydrogen-oxygen torch is 2-5 mm / min.

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