JPH02188451A - Method and device for cooling optical fiber - Google Patents

Abstract

PURPOSE:To enable stable resin coating with high quality by setting a cooling gas feeder and uniformly blowing a cooling gas on the periphery of a drawn optical fiber before resin coating to cool the optical fiber. CONSTITUTION:A cooling gas feeder 4 having cooling gas blowholes is set between a furnace 2 for drawing an optical fiber 3 and a die 5 for primary coating. The drawn optical fiber 3 is passed through a vessel 6 surrounding the feeder 4, having top and bottom holes for passing the fiber 3 and setting to form a cooling gas atmosphere and a cooling gas is fed to cool the fiber 3. The cooled fiber 3 is coated with resin by passing through the die 5 and the resin is cured with a curing device 9.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of cooling an optical fiber that has been heated and drawn prior to coating the fiber, and an apparatus used therefor.

<Prior Art> When a transparent vitrified optical fiber base material is heated and drawn to a predetermined diameter, the outer peripheral surface of the optical fiber is generally subsequently coated with a resin.

Normally, optical fibers are drawn and coated with resin as follows. That is, as shown in FIG. 5, an optical fiber preform 1 prepared separately in advance is held in a core tube 2a of a drawing furnace 2, and a wire is drawn with a constant tension from the tip of the heated and melted optical fiber preform 1. The optical fiber 3 is cooled by natural heat dissipation during the drawing process, and passed through a primary coating die 5 containing liquid resin.
After adhering this resin to the surface of the fiber, the resin is solidified in a resin curing device 9, and the resulting optical fiber strand 7 is wound onto a winding drum 8, or a secondary coating is continuously applied. There is.

This is because the surface of the optical fiber 3 is easily scratched due to contact of the optical fiber 3 after drawing with the winding drum 8 or contact between the optical fibers 3, and furthermore, even a very small scratch can occur on the surface of the optical fiber 3. Since the material is a highly brittle material that is different from metal, it has the disadvantage that even a small tensile load of around 100 g or a small bending load can easily cause a flaw to grow, causing brittle fracture and leading to fiber breakage. It is. Therefore, the method described above is adopted in which the surface of the drawn optical fiber 3 is immediately coated with a resin to maintain its tensile strength and bending strength.

This resin coating is generally performed by coating the optical fiber 3 immediately after drawing with a synthetic resin such as an ultraviolet curing resin, but in order to increase the productivity of optical fiber manufacturing, the drawing speed of the optical fiber 3 has been increased. There is a request.

A problem associated with increasing the drawing speed of optical fibers is that the optical fiber 3 is drawn from a heated and melted optical fiber base material 1, and even though it is cooled by heat dissipation during the drawing process. , it may still not be sufficiently cooled, and if it passes through the die 5 for primary coating in such a state, the coating layer will be affected by the heat of the fiber 3, the resin viscosity of the coating resin will decrease, and the thickness of the coating layer will decrease. In some cases, the dimensions were not stable and sufficient tensile strength and bending strength could not be obtained.

In order to solve this problem, a device for forcibly cooling an optical fiber, etc., disclosed in Japanese Patent Laid-Open No. 61-72648, has been known.

As shown in Fig. 6, this is cooled between an inner tube that forms a space for the optical fiber 3 to pass through on the inner circumference side, and an inner tube that is located approximately coaxially with the inner tube on the outer circumference side of the inner tube. This device includes a cooling pipe 19 having an outer pipe that forms a space through which liquid is inserted. The optical eye μ3 is cooled by this device by introducing a cooling gas such as He gas into the space on the inner circumferential side of the inner tube from the inlet 10 of the inner tube, and cooling the outer tube into the space between the inner tube and the outer tube. Entering from liquid inlet 12 Cooling liquid outlet 1
This is done by forcibly transferring the heat of the optical fiber 3 through the inner tube by passing the cooling liquid discharged from the inner tube.

<Problems to be Solved by the Invention> In order to improve the productivity of optical fibers, as the drawing speed of optical fibers is increased, the amount of heat taken from the optical fibers per unit time must be increased. It was necessary to forcibly cool the optical fiber before coating it with resin.

However, in the method described in JP-A-61-72648, in which the cooling gas is flowed parallel to the optical fiber, it is difficult for the cooling gas near the optical fiber to replace the cooling gas outside the vicinity, and due to heat conduction, the cooling gas near the optical fiber is The cooling gas only moves from the cooling gas inside the cooling gas to the cooling gas outside the cooling gas, so we cannot expect much cooling effect.

Therefore, when the drawing speed is increased, the temperature of the optical fiber does not decrease sufficiently, and this thermal influence causes the dimensions of the resin coating layer to become unstable, which poses problems in that it is difficult to achieve high quality and stable quality of the resin coating. There is a “C”.

Furthermore, in order to increase this heat conduction, H
Although e-gas is used, this method consumes a large amount of He gas, and the price of H8 gas is high, which increases the cost of cooling and ultimately increases the product cost of the optical fiber cable. I have issues.

Means for Solving the Problems> The method for cooling an optical fiber according to the present invention includes passing a drawn optical fiber through a cooling gas atmosphere before coating the optical fiber with a resin, and cooling the optical fiber in the cooling gas atmosphere. The cooling gas forming the cooling gas atmosphere is blown out almost uniformly from around the optical fiber to the optical fiber, and the optical fiber cooling device includes an optical fiber drawing furnace and a primary coating. A cooling gas supply device is provided between the die and the optical fiber so as to surround the optical fiber, and a cooling gas is supplied thereto; It is comprised of a plurality of cooling gas outlets for blowing out a gas flow, and a container that surrounds the cooling gas supply device, has an insertion port for the optical fiber at the upper and lower ends, and forms a cooling gas atmosphere. This is a characteristic feature.

The optical fiber is drawn from the tip of the optical fiber base material heated and melted by a heating source. Cooling gas is blown toward the optical fiber from the outlet of the cooling gas supply device in a container that forms a cooling gas atmosphere. Cool efficiently.

At this time, since the cooling gas flow is sprayed almost evenly around the optical fiber, the optical fiber is cooled without being swayed in the direction of the cooling gas flow.

Embodiment Example A preferred embodiment of the present invention will be described with reference to FIGS. 1 to 4. Incidentally, the same members as in FIGS. 5 and 6 are given the same reference numerals, and redundant explanation will be omitted.

A cooling cylinder 6, which is a container into which the drawn optical fiber 3 is pushed, is located at the bottom of the drawing furnace 2. At the upper and lower ends of the cooling cylinder 6, end plates 18a and 18b are integrally attached, each having a hole 15a and 15b formed in the center thereof, which serves as an insertion opening for the optical fiber 3 and has a diameter slightly larger than that of the optical fiber 3. ing. Further, the cooling cylinder 6 has a cylindrical shape and an outer wall 17 having the pores 15a and 15b approximately in the center, and the pore 15a.

It has an inner wall 14 on the inner circumferential side of the outer wall 17 that is approximately centered on the outer wall 15b and forms a space through which the cooling liquid is forced.
8a and 18b. Further, the outer wall 17 has a coolant port 12 connected to a space through which the coolant passes at its lower end, and a coolant outlet 13 for discharging the coolant at its upper end. Exit 13
are each connected to a coolant circulation system having a heat dissipation device (not shown).

Further, on the inner circumferential side of the inner wall 14, a supply pipe 4, which is a cooling gas supply device, is disposed in a spiral shape, being forced through the small hole 15a and coaxial with the optical fiber 3, and surrounding the optical fiber 3. ing. The upper and lower ends of the supply pipe 4 penetrate the inner wall 14 and the outer wall 17, respectively, and form cooling gas inlets 10a and 10b on the outside of the cooling cylinder 6, and the inlets 10g and 10b are not shown in the figure, respectively. connected to a non-cooling gas supply. Furthermore, the blow-off ports 16 for blowing out the cooling gas supplied from the cooling gas supply source to the optical fiber 3 are located at positions facing the optical fibers 3 of the supply pipe 4, and are arranged at equal intervals in the longitudinal direction of the supply pipe 4. A plurality of blow-off ports 16 are provided, and the hole diameters of the blow-off ports 16 are set so that the cooling gas blow-off speeds are all approximately the same. Therefore, the sum of the velocity vectors of the cooling gas flow blown out from the outlet 16 is approximately zero, and the cooling gas is blown out from the outlet 16 to the optical fiber 3 almost evenly. From the above, the optical fiber 3 is cooled by first passing the cooling gas from the cooling gas supply source to the inlets 10a and 10b of the supply pipe 4.
As a result, the cooling gas blown out from the plurality of outlets 16 is blown onto the optical fiber 3 which is coaxial with the center axis of the spiral of the supply pipe 4, so that the cooling gas is constantly introduced into the vicinity of the optical fiber 3. This is done by the presence of a low-temperature cooling gas and the cooling gas taking away the heat from the optical fiber 3.

Further, the optical fiber 3 is cooled by the cooling gas blown into the space on the inner peripheral side of the inner wall 14 through the pores 15a.

Although a portion of the cooling gas flows out of the cooling cylinder 6 from the optical fiber 15b, the inner circumferential space is filled with the cooling gas and forms a cooling gas atmosphere, so a convection of the cooling gas occurs and the cooling gas flows near or around the optical fiber 3. This is also achieved by constantly introducing low-temperature cooling gas by convection.

Furthermore, tap water, which is a cooling liquid for lubricating, is supplied from the cooling liquid supply device 12 between the inner wall 14 and the outer wall 17, and this cooling liquid fills the inner wall 14 and the space on the inner peripheral side of the inner wall 14. The supply pipe 4, the supply pipe 4
This can also be done by removing heat from the cooling gas inside the optical fiber 3 and the optical fiber 3 by thermal conduction. Also, the cooling gas is connected to the optical fiber 3.
Since the air is blown onto the optical fiber 3 from the plurality of air outlets 16 around the cooling gas flow, the stress on the optical fiber 3 due to the cooling gas flow is canceled out, and as a result, the deflection and vibration of the optical fiber 3 are prevented, and the There is no risk of varying the wire diameter.

As the cooling gas used here, it is effective to use a gas with good thermal conductivity other than air to improve the cooling efficiency, but the amount of gas used is , which cools the optical fiber 3 using heat conduction, is significantly less than the conventional device described in Japanese Patent Application Laid-open No. 61-72648.

Using the manufacturing apparatus with the above configuration, the optical fiber 3 has a diameter of 12 mm.
It is a 5 μm quartz fiber, and the cotton drawing speed is 400 per minute.
m, from the lower end of the drawing furnace 2
．． The cooling cylinder 6 is installed so that the upper end of the cooling cylinder 6 with a vertical length of 2 m is located 5 m below, and the He
Gas was flowed at a rate of 31 per minute. At this time, the temperature of the optical fiber 3 at the lower end of the cooling cylinder 6 is 55°C, which is much higher than the value of 270°C measured using the apparatus shown in Fig. 5 with the same fiber diameter, material, drawing speed, and measurement position. optical fiber 3
I was able to lower the temperature. For comparison, a conventional cooling pipe 19 as shown in FIG. 6 is installed at the same position with the same vertical length, and the optical fiber 3 reaches 55°C with the same fiber diameter, material, drawing speed, He gas temperature, and measurement position. 1 per minute
It was necessary to flow He gas at a rate of 2I.

The locations of the outlets W1 that blow out cooling gas from around the optical fiber 3 to the fiber do not necessarily have to be at equal intervals along the longitudinal direction of the supply pipe 4, and the force in the direction perpendicular to the drawing direction is applied to the optical fiber 3. Any position that does not interfere with the flow may be used.

Further, instead of the spiral supply pipe 4, other pipe structures such as a plurality of pipes installed in parallel to the drawing direction may be used, or other supply devices other than pipe structures may be used.

The cooling gas used in the present invention is preferably an inert gas with high thermal conductivity, and He gas alone or a mixed gas containing He gas is excellent, but it is also possible to use other gases with good thermal conductivity. . Furthermore, although tap water was used as the coolant in this example, the coolant is not limited to tap water, and may be any fluid that has a freezing point below the operating temperature, has a high cooling effect, and is inexpensive. Bye.

<Effects of the Invention> According to the present invention, the position of the optical fiber does not change even if cooling gas is flowed around the optical fiber from the position when no cooling gas is flown. Cooling gas can flow through it without affecting the shape.

Therefore, the temperature of the cooling gas near the optical fiber can be kept low at all times, and the maximum cooling capacity is demonstrated by the cooling gas, making it possible to manufacture high-quality, stable, and low-cost optical fiber wires. .

Further, according to the optical fiber cooling method and cooling device according to the embodiment, heat conduction is performed through the cooling gas filled in the cooling cylinder 6, which is a container, and the cooling effect is achieved by causing convection of the cooling gas inside the container. The cooling effect can be significantly improved compared to conventional methods, and the consumption of cooling gas required to achieve the same level of cooling effect as conventional methods can be significantly reduced, allowing high-quality and stable resin coating to be achieved at low cost. It can be made possible.

[Brief explanation of the drawing]

FIG. 1 is an overall view of an optical fiber manufacturing process and apparatus according to an embodiment of the present invention, FIG. 2 is a side view of an optical fiber cooling device according to an embodiment of the present invention, and FIG. 3 is an overall view of an optical fiber cooling device according to an embodiment of the present invention. An explanatory diagram of the supply pipe according to the embodiment, FIG. 4 is a plan view of the supply pipe of FIG. 3,
FIG. 5 is an overall view of an optical fiber manufacturing process and apparatus according to the prior art, and FIG. 6 is an overall view of an optical fiber manufacturing process and apparatus according to another prior art. In the drawing, 1 is an optical fiber base material, 2 is a drawing furnace, 3 is an optical fiber, 4 is a supply pipe, 5 is a die, 6 is a cooling cylinder, 7 is an optical fiber wire, 8 is a winding drum, 9 10, 10a, 10b are resin curing devices, 10, 10a, 10b are inlets, 12 are coolant inlets, 13 are coolant outlets, 14 are inner walls, 15a, 15b are pores, 16C are air outlets, 17 are outer walls, 18a, 18b are The end plate 19 is a cooling pipe.

Claims (2)

[Claims] (1) Prior to coating a drawn optical fiber with resin, the optical fiber is passed through a cooling gas atmosphere, and in this cooling gas atmosphere, a cooling gas forming the cooling gas atmosphere is applied to the optical fiber from around the optical fiber. A method for cooling an optical fiber, characterized in that the optical fiber is blown out almost evenly. (2) A cooling gas supply device provided between the optical fiber drawing furnace and the primary coating die to surround the optical fiber and supplying cooling gas; A plurality of cooling gas outlets that blow out a cooling gas flow almost uniformly from the periphery of the fiber to the optical fiber, and an insertion opening for the optical fiber surrounding the cooling gas supply device and at the upper and lower ends, and providing a cooling gas atmosphere. 1. An optical fiber cooling device comprising: a container for forming an optical fiber;