Preparation method of panda-shaped circle-preserving rotating optical fiber

Abstract

The invention relates to a panda-shaped circle-preserving rotating optical fiber preparation method, which comprises the following steps: adopting a polarization-preserving core rod, and matching with a corresponding sleeve to carry out fusion shrinkage; the method comprises the following steps: stretching a B-doped stress rod to a target core diameter to form two stress rods; the punching rod and the two stress rods are assembled, and the extension rods of the stress rods are fixed; melting and shrinking by using a flame lathe, and carrying out heat preservation treatment on a burning point at the extension joint of the stress rod during melting and shrinking; and stretching the preform to a target diameter after fusion shrinkage, placing the preform in an annealing furnace to remove local stress so as to uniformly distribute the stress, transferring the preform to a drawing tower after extension cleaning, and drawing while rotating to form the panda-shaped circle-keeping rotating optical fiber. The optical fiber single-sleeve output length can be increased through rotary drawing of the preform, and the utilization rate of raw materials is increased; the preform rod is not easy to burst in the melting shrinkage and stretching processes, so that the preform rod can be effectively produced, and the qualification rate in the preparation process is improved; and the uniformity of a stress area and a core area of the preform rod is ensured through two times of melting shrinkage and stretching.

Description

Technical Field

[0001] The invention patent belongs to the technical field of rotating optical fiber preparation, and relates to a method for preparing a panda-shaped circular rotating optical fiber. Background Art

[0002] Panda-type circular rotation optical fiber is a special optical fiber. "Panda-type" refers to the internal structure of the optical fiber. There are two stress areas in its cladding that are shaped like panda eyes. These two stress areas can exert stress on the core, thereby producing a birefringence effect. The circular rotation property allows it to maintain the circular shape of the core during the twisting process, ensuring efficient transmission of light. It combines the polarization-maintaining property and circular rotation property of the panda-type optical fiber. Panda-type circular rotation optical fiber is mainly used in optical fiber current sensors. The working principle of optical fiber current sensors is based on the Faraday magneto-optical effect. The optical fiber current sensor determines the magnitude of the measured current by measuring the angle at which the polarization plane of the light wave rotates when passing through the magneto-optical material due to the magnetic field generated by the current. Optical fiber current sensors are widely used in the power industry and are mainly used to measure the current of high-voltage power systems. Compared with traditional electromagnetic current transformers, optical fiber current sensors have the advantages of higher measurement accuracy, anti-electromagnetic interference capability, and safe operation. Optical fiber current sensors can also be combined with motor manufacturers and measuring instrument manufacturers to develop a series of power system measurement and diagnostic devices such as calibration devices for line accident points and devices for determining accident intervals.

[0003] Currently in the optical fiber manufacturing industry, patent CN92108598.2 "Optical fiber maintaining circular polarization state and its preparation method" adopts the MCVD method to prepare preform rods, and uses stress columns to bury preform rods or thick tubes with thin columns. The optical fiber preform rods are first made, and then they are rotated and drawn into circular optical fibers. This method only embeds a stress rod and does not involve the specific processing method of burying stress columns in preform rods; this method is difficult to prepare preform rods. Patent CN108107504 A "A round optical fiber and its preparation method" uses a core rod to stretch and match a suitable sleeve to shrink, forming a shrink rod, the shrink rod is punched with a small hole with a hole diameter of 2~5mm, the stress rod core diameter is 2~5mm, the punched rod and the stress rod are combined into a preform rod, and a vacuum drawing tower is used to directly rotate and draw the wire, or a vacuum drawing furnace is used to first stretch and then rotate and draw the wire; this method is only suitable for punching small holes in the shrink rod with a hole diameter of 2~5mm. The length of the small holes punched in the industry is not long, and it is not suitable for a hole diameter of more than 5mm; the stress rod core diameter is 2~5mm, which is not suitable for a stress rod core diameter of more than 5mm; and the drawing furnace is vacuum stretched, and the stretched intermediate is easy to burst during practice, and the qualified rate is not high. Summary of the invention

[0004] The technical problem to be solved by the patent of this invention is to provide a method for preparing a panda-shaped circular rotating optical fiber, increase the output length of a single set of optical fibers, avoid bursting when stretching the intermediate, and ensure the uniformity of the stress zone and core zone of the preform rod through two melting and stretching.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a panda-shaped circular rotating optical fiber, comprising the following steps: S1, using a polarization-maintaining core rod and matching the corresponding sleeve for melting and shrinking; S2, using a B-doped stress rod stretched to the target core diameter to form two stress rods; S3, assembling the punching rod and the two stress rods, and fixing the extension rods of the stress rods; S4, use flame lathe to melt and shrink, and perform heat preservation treatment on the burnt points where the stress rods are connected during melting and shrinking; S5, after melting and shrinking, the preform is stretched to the target diameter, placed in an annealing furnace to remove local stress and make the stress evenly distributed. After cleaning, it is moved to a drawing tower and drawn into a panda-shaped circular rotating optical fiber while rotating.

[0006] In S1, the melt-shrink rod is stretched to the target diameter and then punched, and the two ends are connected to auxiliary pipes, and then corroded, cleaned and dried.

[0007] In S2, two stress rods are connected to pure silicon rods at both ends and then polished to the target diameter, and one end of the pure silicon rod is tapered, corroded, cleaned and dried.

[0008] In S4, the combined preform rod is melted and shrunk. After the melting and shrinking is completed, the outer diameter of the melted and shrunk rod is larger. During the stretching, the outer diameter of the melted and shrunk rod is reduced, and at the same time, the core diameter of the melted and shrunk rod is reduced accordingly.

[0009] In S4, the temperature during melting and shrinkage is between 1900-2300°C, and the negative pressure in the tube is between -50kPa and -100kPa.

[0010] The main beneficial effects of the present invention are mainly reflected in: Preform rod rotary drawing can increase the output length of a single set of optical fiber and improve the utilization rate of raw materials.

[0011] To avoid the intermediate from bursting when being stretched, if the stress rod is directly combined into the punching rod, the intermediate is stretched through a drawing tower, and a single intermediate is collected, the intermediate will be easily burst due to high stress during cutting. Using this method, the preform is not easy to burst during the melting and stretching process, and the preform can be effectively produced, thereby improving the qualified rate in the preparation process.

[0012] Through the two processes of melting and stretching, although there is volatility during melting and stretching, the uniformity of the stress zone and the core zone of the preform can be ensured, and a good "panda-shaped" structure can be maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0014] Figure 1 It is a front schematic diagram of the melt-shrink rod of the present invention.

[0015] Figure 2 for Figure 1 Schematic side view of .

[0016] Figure 3 It is a front schematic diagram of the punching rod of the present invention.

[0017] Figure 4 for Figure 3 Schematic side view of .

[0018] Figure 5 This is a schematic front view of the polished stress rod of the present invention.

[0019] Figure 6 for Figure 5 Schematic side view of .

[0020] Figure 7 It is a schematic diagram of the combined preform rod of the present invention.

[0021] Figure 8 This is a schematic front view of the panda-shaped circular-preserving rotating optical fiber of the present invention.

[0022] Fig. 9 for Figure 8 Schematic side view of .

[0023] In the figure: core rod 1; sleeve 2; first preform rod 3; melt-shrink rod 4; punch rod 5; stress rod a; stress rod b; stress rod c; cleaned and dried punch rod 6; second preform rod 7; third preform rod 8; panda-type round-preserving rotated optical fiber 9. DETAILED DESCRIPTION

[0024] like Figure 1 to Figure 9 A method for preparing a panda-shaped circularly rotating optical fiber comprises the following steps: S1, using a polarization-maintaining core rod and matching the corresponding casing for melting and shrinking; after the melting and shrinking rod is stretched to the target diameter, holes are punched, and auxiliary pipes are connected at both ends, and then corroded, cleaned and dried; S2, using a B-doped stress rod stretched to the target core diameter to form two stress rods; S3, assembling the punching rod and the two stress rods, and fixing the extension rods of the stress rods; S4, use flame lathe to melt and shrink, and perform heat preservation treatment on the burnt points where the stress rods are connected during melting and shrinking; S5, after melting and shrinking, the preform is stretched to the target diameter, placed in an annealing furnace to remove local stress and make the stress evenly distributed. After cleaning, it is moved to a drawing tower and drawn into a panda-shaped circular rotating optical fiber while rotating.

[0025] Example 1. Use chemical vapor deposition equipment to prepare a core rod 1 of an optical fiber with a wavelength of 1310nm and a cladding diameter of 125μm, a core diameter of 2.0mm, NA=0.18, and an outer diameter of 20mm, and extend, clean, and dry the core rod.

[0026] 2. Select D52*14.5*650 casing 2 for extension, cleaning and drying.

[0027] 3. Assemble the cleaned and dried core rod 1 and the cleaned and dried sleeve 2, and install a special fixture to assemble them into a first preform rod 3.

[0028] 4. Use flame lathe equipment, with the flame torch moving speed of 10mm / min-20mm / min, the flame temperature of 1900℃-2300℃, and the negative pressure in the control tube at -50kpa to -100kpa to melt and shrink the first preform rod 3. After the melting and shrinking is completed, the outer diameter of the melted rod is 50mm. Pull the outer diameter of the melted rod to D30mm. At this time, the core diameter of the melted rod is 1.2mm. After stretching, cut off the 550mm long melted rod 4.

[0029] 5. Use deep hole drilling and grinding equipment with a D10mm cutter head to drill holes, set a specific program, and drill two holes with a specific spacing. The hole diameter is 10mm, and the distance between the centers of the two holes is 13mm. The shrinkage rod 4 becomes a punching rod 5 after drilling; Extend the two ends of the punching rod 5 with extension tubes, one end slightly shrinks the inner hole, and the other end requires that the inner hole does not shrink. After extension, clean and dry to remove impurities in the inner hole of the punching rod to ensure the cleanliness of the punching rod. At this time, the punching rod 5 becomes a cleaned and dried punching rod 6. 6. Prepare stress rod a with a core diameter of 17 mm by chemical vapor deposition equipment, and stretch it into two stress rods b and stress rod c with a core diameter of 8.4 mm, an outer diameter of 20 mm, and a length of 500 mm; both ends of stress rod b and stress rod c are respectively connected with pure silicon rods with a length of 20 mm and an outer diameter of 10 mm to ensure the quality of the joints, and use an external cylindrical grinder to grind the outer diameters of stress rods b and stress rods c to 10 mm, respectively. One end of the ground stress rods b and stress rods c is tapered, and the other end is connected with a pure silicon rod with an outer diameter of 10 mm. The outer diameters of the two stress rods are controlled at 9.9 mm through corrosion cleaning to remove impurities on the surface of the stress rods and ensure the cleanliness of the stress rods.

[0030] 7. Assemble the cleaned stress rods b and c into the cleaned and dried punched rods 6 to form a second preform rod 7. Install a special fixture to fix the pure silicon rods of stress rods b and c. The special fixture contains a rotating joint to ensure that negative pressure can be drawn during melting and shrinkage.

[0031] 8. Use a flame lathe, with a flame torch moving speed of 12mm / min-20mm / min, a flame temperature of 1900℃-2300℃, and a negative exhaust pressure of -50kpa to -100kpa to melt and shrink the second preform rod 7 (containing two stress rods). During melting and shrinking, first burn the pure silicon rod in front of the stress rod, and then burn the stress rod as the lamp head moves. After burning, the joint between the stress rod and the pure silicon rod is insulated (at this time, the stress is concentrated there, and there is a risk of bursting). After melting and shrinking, the outer diameter of the preform rod is about 29.8mm. The outer diameter of the preform rod is stretched to D20mm to become the third preform rod 8, which is placed in an annealing furnace to remove local stress and make the stress distribution uniform.

[0032] 9. Connect the third preform rod 8 to the D20 extension rod, clean and dry it, and then move it to the drawing tower. Draw the fiber while rotating it to form a panda-shaped circular rotating optical fiber 9. Figures 8 and 9 shown.

[0033] Compared with the methods currently widely used in the industry, the above method has the following innovations: Conventional melting and shrinking core rods and melting and shrinking rod stretching, mechanical equipment drilling, and stress rod grinding are used. Before grinding, pure silicon rods need to be extended at both ends of the stress rods, and finally the stress rods are combined into the punched rods, and the combined rods are melted and stretched. The melting and shrinking process requires insulation treatment at the extended parts of the stress rods. There is a probability of explosion at the extended parts during the melting and shrinking process, which leads to failure of preform preparation. If the stress rods are not connected with pure silicon rods at both ends, they are prone to explosion due to preheating before melting and shrinking. Therefore, it is critical to melt and shrink the combined preforms, including the stress rods.

[0034] The combined preform is melted and stretched twice, which is suitable for the preparation of panda-shaped circular rotating optical fiber preforms of different sizes.

[0035] The preformed rod may contain a plurality of stress rods. In addition to the panda-type circularity-preserving rotating optical fiber preformed rod, the method can also be used to prepare a combined preformed rod containing a plurality of stress rods.

[0036] Therefore, it has the following advantages: The method is adopted to prepare a panda-shaped circularity-preserving rotating optical fiber preform rod. The rotating drawing of the preform rod can increase the output length of a single set of optical fibers and improve the utilization rate of raw materials.

[0037] It can avoid the bursting of the intermediate during stretching. If the stress rod is directly combined with the punching rod, the intermediate is stretched through a drawing tower, and a single intermediate is collected. When cutting, the stress of the intermediate is large and it is easy to burst. Using this method, the preformed rod is not easy to burst during the melting and stretching process, and the preformed rod can be effectively produced, which improves the qualified rate in the preparation process.

[0038] This method involves two passes of melting and stretching. Although there is volatility during melting and stretching, it can ensure the uniformity of the stress zone and the core zone of the preform and maintain a good "panda-shaped" structure.

[0039] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The embodiments and features in the embodiments in this application can be combined with each other in any way without conflict. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for preparing a panda-shaped circular rotating optical fiber, characterized in that: The steps include: S1, using a polarization-maintaining core rod and matching the corresponding sleeve for melting and shrinking; S2, using a B-doped stress rod stretched to the target core diameter to form two stress rods; S3, assembling the punching rod and the two stress rods, and fixing the extension rods of the stress rods; S4, use flame lathe to melt and shrink, and perform heat preservation treatment on the burnt points where the stress rods are connected during melting and shrinking; S5, after melting and shrinking, the preform is stretched to the target diameter, placed in an annealing furnace to remove local stress and make the stress evenly distributed. After cleaning, it is moved to a drawing tower and drawn into a panda-shaped circular rotating optical fiber while rotating.

2. The method for preparing a panda-shaped circularly preserved rotating optical fiber according to claim 1, wherein: In S1, the melt-shrink rod is stretched to the target diameter and then punched, and the two ends are connected to auxiliary pipes, and then corroded, cleaned and dried.

3. The method for preparing a panda-shaped circularity-preserving rotating optical fiber according to claim 1, wherein: In S2, two stress rods are connected to pure silicon rods at both ends and then polished to the target diameter, and one end of the pure silicon rod is tapered, corroded, cleaned and dried.

4. The method for preparing a panda-shaped circularly preserved rotating optical fiber according to claim 1, wherein: In S4, the combined preform rod is melted and shrunk. After the melting and shrinking is completed, the outer diameter of the melted and shrunk rod is relatively large. During the stretching, the outer diameter of the melted and shrunk rod is reduced, and at the same time, the core diameter of the melted and shrunk rod is reduced accordingly.

5. The method for preparing a panda-shaped circularity-preserving rotating optical fiber according to claim 1, wherein: In S4, the temperature during melting and shrinkage is between 1900-2300°C, and the negative pressure in the tube is between -50kPa and -100kPa.

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