Optical fiber coating device and coating method

Abstract

The invention discloses an optical fiber coating device and a coating method, and belongs to the technical field of optical fiber preparation. The optical fiber coating device comprises a coating mold, a material tank and a pressure system, the coating mold comprises an inner cavity, an outer cavity and a base, a material storage cavity used for containing a coating material is formed in the outer cavity, a stepped optical fiber through hole is formed in the inner cavity, a large hole of the optical fiber through hole is located in the material storage cavity, and the upper end of the large hole extends out of the outer cavity to form an optical fiber inlet; a small hole of the optical fiber through hole is located below the storage cavity, the lower end extends out of the outer cavity to form an optical fiber outlet, the optical fiber through hole is communicated with the storage cavity through a via hole formed in the side wall of the inner cavity, and the storage cavity is communicated with the atmosphere; a coating material is stored in the material tank and conveyed to the coating mold through the pressure system. According to the structural design of the coating mold, the coating material can form a stable flow field under the constraint of the inner cavity, so that the coating material continuously and uniformly covers the surface of the optical fiber, and a continuous coating is formed on the surface of the optical fiber.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber preparation, and in particular to an optical fiber coating device and a coating method. Background Art

[0002] A variable-diameter optical fiber is one whose diameter changes along its length. It typically consists of a header, a tapered section, and a pigtail. The diameters of the header and pigtail remain constant, and the tapered section smoothly connects the header and pigtail. Optical fiber generally consists of a core, cladding, and coating. The coating primarily protects the cladding and core, enhancing the fiber's mechanical strength and reducing light attenuation. It also forms a total internal reflection structure with the fiber's core material, allowing light waves to propagate along the fiber.

[0003] Coating quality significantly impacts the mechanical and optical properties, environmental stability, and service life of optical fibers. Existing coating devices can form a uniform coating layer on the surface of normal optical fibers. However, when used to coat variable-diameter optical fibers, the surface area per unit length varies due to the varying diameter of the fiber. Consequently, the coating thickness also varies along the length, leading to defects such as poor concentricity, beading, and surface wavyness. This results in uneven coating, which in turn affects the quality of the fiber. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides an optical fiber coating device and a coating method.

[0005] The technical solution adopted in the present invention is:

[0006] A fiber optic coating device comprises a coating mold, a material tank and a pressure system. The coating mold comprises an inner cavity, an outer cavity and a base. The base is used to fix the coating mold in a drawing tower. The outer cavity is fixed on the base. A storage cavity for accommodating coating material is provided in the outer cavity. The inner cavity is arranged inside the outer cavity. A stepped optical fiber through-hole is provided in the inner cavity. The large hole of the optical fiber through-hole is located in the storage cavity and the upper end extends out of the outer cavity to form an optical fiber inlet. The small hole of the optical fiber through-hole is located below the storage cavity and the lower end extends out of the outer cavity to form an optical fiber outlet. The optical fiber through-hole is connected to the storage cavity through a through hole opened on the side wall of the inner cavity, and the storage cavity is connected to the atmosphere; the diameter of the small hole of the optical fiber through-hole is adapted to the outer diameter of the optical fiber, and the material tank is connected to the outer cavity storage cavity through a pipeline; the coating material is stored in the material tank, and the coating material is transported to the coating mold through the pressure system.

[0007] Existing coating dies typically have a single inner cavity, into which the coating material is injected directly. This makes it difficult to maintain a stable liquid level within the coating area, resulting in coating pressure fluctuations. When the coating pressure is insufficient, the coating cannot fully and quickly fill the gap between the coating die and the optical fiber, easily leading to coating thinning or localized over-thinning. When the coating pressure is too high, excessive coating rapidly flows into the coating die, easily causing the coating to thicken. This can lead to defects such as poor concentricity, beading, and a wavy surface. Furthermore, when the pressure fluctuates, the coating flow rate and flow rate also vary, resulting in inconsistent coating thickness and density at different locations. For example, during a sudden increase in pressure, the coating may form a thicker deposit on the optical fiber surface; while when the pressure decreases, areas of over-thin coating may appear, affecting coating uniformity. Furthermore, the structure of existing coating dies hinders uniform distribution of the resin entering the coating area, making it prone to localized over-speed or over-slow flow rates, resulting in uneven coating thickness.

[0008] The present application has an inner cavity and an outer cavity that are connected by static pressure. The coating material (such as resin) first enters the outer cavity, is evenly distributed in the outer cavity, and then enters the inner cavity through the via. On the one hand, the resin can be evenly distributed in the coating area to avoid the situation where the local flow rate is too fast or too slow, resulting in uneven coating thickness. On the other hand, the setting of the outer cavity provides a larger buffer space, which can reduce the pressure fluctuations caused by changes in the resin flow rate. In addition, the larger storage volume helps to smooth the flow process of the resin. During the coating process, the flow of the resin is not absolutely uniform, and there will be some small pulsations and irregular changes. The increase in volume can make these irregular changes get a certain degree of buffering and averaging before being transmitted to the coating area, thereby making the resin flow entering the coating area more stable, thereby improving pressure stability and improving coating quality.

[0009] Furthermore, a plurality of via holes are provided, and the plurality of via holes are evenly distributed along the circumference of the inner cavity.

[0010] It is beneficial for the resin to be evenly distributed in the coating area, avoiding the situation where the local flow rate is too fast or too slow, resulting in uneven coating thickness.

[0011] Furthermore, the via hole is conical in shape, with its inlet facing the outer cavity, and the inlet is connected to the side wall of the inner cavity by an arc transition.

[0012] The smooth and gradual inlet design allows the resin to enter the optical fiber channel smoothly, reduces the generation of eddy currents and turbulence, ensures the stability of the resin flow, and thus facilitates the formation of a uniform coating.

[0013] Furthermore, the large hole and the small hole of the optical fiber through hole are connected through a tapered hole.

[0014] It can make the resin flow evenly in the channel, reduce dead angles and turbulence, help form a smooth and uniform coating on the surface of the optical fiber, and improve the density and surface quality of the coating.

[0015] Furthermore, the length of the small hole section of the optical fiber through hole is 20 to 30 times the diameter of the optical fiber through hole.

[0016] If the optical fiber channel is too short, it cannot ensure that the resin reaches a stable laminar flow, resulting in poor coating uniformity; if the optical fiber channel is too long, it will increase the flow resistance of the coating, increase energy consumption, and may also cause the resin to stay in the channel for too long, resulting in solidification or precipitation, affecting the coating quality.

[0017] Furthermore, the inner diameter of the material storage cavity of the outer cavity is 2 to 10 times the diameter of the large hole of the optical fiber through hole of the inner cavity.

[0018] If the storage chamber is too small, it will not have a buffering effect. If it is too large, the system's response time to pressure changes will be longer. Moreover, as the volume increases, the resin residence time is prolonged, which can easily lead to local temperature increases, affecting the viscosity and fluidity of the coating, and thus adversely affecting pressure stability.

[0019] Furthermore, the base is provided with a material receiving cavity, and the base is threadedly connected to the outer cavity.

[0020] When the outlet of the optical fiber through hole is blocked, the resin will overflow from the outer cavity and the inner cavity. The overflowed resin can be recovered through the base to reduce waste.

[0021] Furthermore, the inner cavity and the outer cavity are connected by threads, which facilitates disassembly for maintenance or replacement of parts.

[0022] A coating method, using any one of the above-mentioned optical fiber coating devices, comprises the following steps:

[0023] (1) The optical fiber preform is fed into the drawing heating furnace at a certain speed through a rod feeding device. After being heated and softened, it passes through a coating die for coating, then enters a curing device for curing, and then enters a stretching mechanism for stretching into a variable diameter optical fiber, which is then wound up by a winding device.

[0024] (2) During the coating process, the variable diameter optical fiber passes through the optical fiber through-hole with the small end facing downward in the plumb direction, and the pressure system transports the coating material in the material tank to the outer cavity storage cavity. The coating material in the outer cavity storage cavity passes through the hole and enters the optical fiber through-hole of the inner cavity. Under the action of pressure, the coating material in the optical fiber through-hole is evenly distributed in the annular gap between the optical fiber and the optical fiber through-hole, and forms a continuous coating on the surface of the optical fiber.

[0025] By using the above method, a layer of coating material can be evenly coated on the circumference of the surface of the variable-diameter optical fiber, and the outer surface of the optical fiber after coating is smooth and flat without beads.

[0026] Furthermore, the pressure system controls the liquid level of the coating material in the outer cavity and the stability of the coating pressure. The pressure system controls the flow rate and pressure of the coating material and further controls the liquid level of the coating material to ensure the stability of the coating pressure.

[0027] Beneficial effects of the present invention:

[0028] 1. The structural design of the coating mold can make the resin form a stable flow field under the constraint of the inner cavity, so that the resin can cover the surface of the optical fiber continuously and evenly and form a continuous coating on the surface of the optical fiber.

[0029] 2. The diameter of the pigtail section of the variable diameter optical fiber is relatively thin and its mechanical strength is relatively weak. After being coated by this device, the outer diameter of the variable diameter optical fiber is consistent with the aperture diameter of the optical fiber through hole, and the coating of the pigtail section is thicker, which is beneficial to improving the overall mechanical strength of the optical fiber and increasing the service life of the variable diameter optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of the optical fiber coating device of Example 1.

[0031] Figure 2 Schematic diagram of the coating mold structure.

[0032] Figure 3 for Figure 2 A partial enlarged view of point A.

[0033] Figure 4 This is a diagram of the optical fiber coating device in use.

[0034] Figure 5 This is a schematic structural diagram of the optical fiber coating device of Example 2. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and preferred embodiments.

[0036] Example 1

[0037] See Figure 1-Figure 3The present embodiment provides an optical fiber coating device, including a coating mold 100, a material tank 1 and a pressure system. The coating mold includes an inner cavity 30, an outer cavity 20 and a base 10. The base is used to fix the coating mold in the drawing tower. The outer cavity is fixed on the base. The outer cavity is provided with a storage cavity 201 for accommodating the coating material. The inner cavity 30 is provided inside the outer cavity 20. The inner cavity is provided with a stepped optical fiber through hole. The large hole 32 of the optical fiber through hole is located in the storage cavity and the upper end is An optical fiber inlet 301 is formed by extending out of the outer cavity, and a small hole 33 of the optical fiber through hole is located below the storage cavity and the lower end extends out of the outer cavity to form an optical fiber outlet 302. The optical fiber through hole is connected to the storage cavity 201 through a through hole 31 opened on the side wall of the inner cavity, and the storage cavity 201 is connected to the atmosphere; the small hole diameter of the optical fiber through hole is adapted to the outer diameter of the optical fiber, and the material tank is connected to the outer cavity storage cavity through a pipeline; the coating material is stored in the material tank 1, and the coating material is transported to the coating mold through a pressure system.

[0038] In this embodiment, the base 10 is a short cylindrical shape with a circular groove inside. The inner bottom surface of the central portion of the circular groove protrudes inward to form an upper boss, while the outer bottom surface protrudes outward to form a lower boss. Threaded holes are provided in the centers of the upper and lower bosses. The upper boss supports and is threadedly connected to the inner cavity. The annular space 11 formed between the outer wall of the upper boss and the circular groove is used to collect coating material overflowing from the upper and lower cavities. The lower boss is used to threadably connect to the inner cavity and clamp the coating die into the wire drawing machine.

[0039] The outer cavity 20 is a stepped cylindrical structure that is larger at the top and smaller at the bottom. The outer diameter of the large cylindrical section is consistent with the outer diameter of the upper boss of the base, while the outer diameter of the small cylindrical section is consistent with the inner diameter of the threaded hole of the upper boss. The outer cavity 201 is provided with a circular cavity for accommodating the coating material. The small cylindrical section is provided with a threaded hole for threaded connection to the inner cavity. The upper end of the threaded hole is connected to the storage cavity, and the lower end extends through the bottom surface of the outer cavity 20. The outer cavity 20 is threadedly connected to the base 10 via the external threads of its small cylindrical section. The storage cavity 201 is provided with a top cover. The center of the top cover is designed to pass through the central hole of the inner cavity 20, and the inner diameter of the central hole is larger than the outer diameter of the inner cavity 20. The provision of the top cover prevents dust and other substances from contaminating the coating material. The lower end of the storage cavity 201 is provided with a feed port 21. The feed port 21 is arranged at the lower end of the storage chamber 201, which is beneficial to reducing the impact on the coating material in the storage chamber, keeping the liquid surface stable, and facilitating stable control of the liquid level.

[0040] The inner cavity 30 is in the shape of a stepped cylinder, with an external thread provided in the middle section of the cylinder. The inner cavity 30 is threadedly connected to the outer cavity 20 via the threaded portion of the middle section. The upper and lower ends of the inner cavity 30 extend from the upper cover and bottom surface of the outer cavity, respectively. The large hole 32 of the optical fiber through hole is provided in the large diameter cylindrical section, and the small hole 33 of the optical fiber through hole is provided in the middle section and the small diameter cylindrical section. The large hole 32 of the optical fiber through hole is located in the storage cavity 201. A plurality of through holes 31 are uniformly formed around the lower end of the side wall of the large hole 32. The storage cavity 201 is connected to the large hole 32 of the optical fiber through hole through the plurality of through holes 31. The storage cavity 201 is connected to the atmosphere via its central through hole. The liquid levels in the outer and inner cavities are in the same horizontal plane under the action of atmospheric pressure. By controlling the liquid level of the coating material in the outer cavity through the pressure system, the liquid level of the coating material in the inner cavity can be controlled, that is, the static pressure of the coating can be controlled.

[0041] The large hole 32 is connected to the small hole 33 through a tapered hole, and the small hole section extends out of the outer cavity and the base to form a coating nozzle.

[0042] See Figure 3 In this embodiment, the through hole 31 is conical in shape, with its inlet facing the outer cavity, and the inlet is connected to the side wall of the inner cavity by an arc transition.

[0043] The inner diameter of the small hole 33 is set to D1, and the length of the small hole 33 is preferably selected within the range of 20 to 30 times D1; ​​the inner diameter of the large hole 32 is set to D2, and the inner diameter of the storage cavity 201 is preferably selected within the range of 2 to 10 times D2.

[0044] The pressure system is a prior art system, such as a pneumatic or hydraulic system. In the present embodiment, the pressure system includes a feed pump 2, preferably a positive displacement pump such as a gear pump or a screw pump, which helps maintain a stable flow rate. The inlet of the feed pump 2 is connected to the feed tank 1 via a pipeline and a feed valve, and the outlet is connected to the feed port 21 of the storage chamber via a pipeline and a discharge valve. A flow meter 3 is provided on the pipeline, and the flow meter 3 can be interlocked with the feed pump 2 to maintain a stable flow rate. A pressure gauge 4 is also provided on the pipeline for monitoring the pump outlet pressure.

[0045] Example 2

[0046] See Figure 5 The difference between this embodiment and embodiment 1 is that it also includes a water bath temperature control system; the water bath temperature control system is used to accurately control the temperature of the coating liquid, eliminate local temperature differences, avoid side reactions or abnormal curing due to overheating or overcooling, and avoid uneven coating thickness or changes in material properties due to temperature fluctuations; and can maintain the coating material in an optimal viscosity range to ensure coating smoothness and post-coating quality.

[0047] Water bath temperature control systems are conventional technology. In this embodiment, for example, the system includes a jacket 40 disposed outside an outer chamber 20, a temperature controller 50, and a temperature control system (not shown). The jacket is provided with a medium inlet and a medium outlet. The medium inlet is located at the bottom and is used to introduce a constant-temperature liquid, such as hot water, cold water, or thermal oil. The medium outlet is located at the top and is used to discharge the circulated medium, forming a closed loop. The temperature control system is used to regulate the medium temperature.

[0048] Example 3

[0049] See Figure 4 The present application also provides a coating method, using the optical fiber coating device 100 of Example 1, which specifically includes the following steps:

[0050] (1) The optical fiber preform is fed into a drawing heating furnace (not shown) at a certain speed by a rod feeding device. After being heated and softened, it passes through a coating die for coating, then enters a curing device (not shown) for curing, and then enters a stretching mechanism (not shown) to be stretched into a variable diameter optical fiber, which is then wound by a winding device (not shown).

[0051] (2) During the coating process, the variable diameter optical fiber 5 passes through the optical fiber through hole along the plumb bob direction with the small end facing downward, and the feed pump 2 extracts the coating material in the material tank 1 and transports it to the outer cavity storage chamber 201. The coating material in the outer cavity storage chamber enters the optical fiber through hole of the inner cavity through the hole 31. The coating material in the optical fiber through hole is evenly distributed in the annular gap between the optical fiber and the optical fiber through hole under the action of pressure, and forms a continuous coating 51 on the surface of the optical fiber.

[0052] During the coating process, the flow rate and pressure of the feed pump 2 are controlled to be stable, thereby controlling the liquid levels in the inner and outer cavities to be stable, thereby ensuring the stability of the coating pressure.

[0053] The drawing device and drawing process are both existing technologies. This application uses the structural design of the coating mold to enable the resin to form a stable flow field under the constraint of the inner cavity, so that the resin can continuously and evenly cover the surface of the optical fiber and form a continuous coating on the surface of the optical fiber.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also within the scope of protection of the present invention.

Claims

1. An optical fiber coating device, characterized in that: The coating mold comprises an inner cavity, an outer cavity and a base. The base is used to fix the coating mold in the drawing tower. The outer cavity is fixed on the base. The outer cavity is provided with a storage cavity for accommodating the coating material. The inner cavity is arranged inside the outer cavity. The inner cavity is provided with a stepped optical fiber through-hole. The large hole of the optical fiber through-hole is located in the storage cavity and the upper end extends out of the outer cavity to form an optical fiber inlet. The small hole of the optical fiber through-hole is located below the storage cavity and the lower end extends out of the outer cavity to form an optical fiber outlet. The optical fiber through-hole is connected to the storage cavity through a through-hole opened on the side wall of the inner cavity, and the storage cavity is connected to the atmosphere. The diameter of the small hole of the optical fiber through-hole is adapted to the outer diameter of the optical fiber. The material tank is connected to the storage cavity of the outer cavity through a pipeline. The coating material is stored in the material tank, and the coating material is transported to the coating mold through the pressure system.

2. The optical fiber coating device according to claim 1, characterized in that: A plurality of through holes are provided, and the plurality of through holes are evenly distributed along the circumference of the inner cavity.

3. The optical fiber coating device according to claim 1, characterized in that: The through hole is conical in shape, with its inlet facing the outer cavity, and the inlet is connected to the side wall of the inner cavity by an arc transition.

4. The optical fiber coating device according to claim 1, characterized in that: The large hole and the small hole of the optical fiber through hole are connected by a tapered hole.

5. The optical fiber coating device according to claim 1, characterized in that: The length of the small hole section of the optical fiber through hole is 20 to 30 times its diameter.

6. The optical fiber coating device according to claim 1, characterized in that: The inner diameter of the material storage cavity of the outer cavity is 2 to 10 times the diameter of the large hole of the optical fiber through hole of the inner cavity.

7. The optical fiber coating device according to claim 1, characterized in that: The base is provided with a material receiving cavity, and the base is threadedly connected to the outer cavity.

8. The optical fiber coating device according to claim 1, characterized in that: The inner cavity and the outer cavity are connected through threads.

9. A coating method, characterized in that: Using the optical fiber coating device according to any one of claims 1 to 8 comprises the following steps: (1) The optical fiber preform is fed into the drawing heating furnace at a certain speed through a rod feeding device. After being heated and softened, it passes through a coating die for coating, then enters a curing device for curing, and then enters a stretching mechanism for stretching into a variable diameter optical fiber, which is then wound up by a winding device. (2) During the coating process, the variable diameter optical fiber passes through the optical fiber through-hole with the small end facing downward in the plumb direction, and the pressure system transports the coating material in the material tank to the outer cavity storage cavity. The coating material in the outer cavity storage cavity passes through the hole and enters the optical fiber through-hole of the inner cavity. Under the action of pressure, the coating material in the optical fiber through-hole is evenly distributed in the annular gap between the optical fiber and the optical fiber through-hole, and forms a continuous coating on the surface of the optical fiber.

10. A coating method according to claim 9, characterized in that: The liquid level of the coating material in the outer cavity is controlled by the pressure system to control the stability of the coating pressure.

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