JPS62207735A - Method and device for drawing optical fiber - Google Patents

Abstract

PURPOSE:To reduce the variance in the diameter of an optical fiber by uniformly blowing an inert gas on the periphery of the optical fiber along the axis of the furnace core tube of a heating furnace and in parallel with the axis in the title method for drawing the optical fiber while introducing the inert gas into the heating furnace. CONSTITUTION:The optical fiber base material is inserted along the axis of the furnace core tube 6 surrounded with an annular heater 7, the tip end part is heated by the high temp. of the furnace core tube 6 to form a contracted part 2, and the base material is drawn into an optical fiber 3 having a specified outer diameter. In this case, plural concentric cylindrical blow off ports 41-43 coaxial with the furnace core tube 6 are provided on the upper end of the furnace core tube 6, and inert gases g1-g3 are blown off from the respective ports into the furnace core tube 6 along the gap between the furnace core tube 6 and the optical fiber base material.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a drawing method and apparatus for drawing a strong optical fiber from an optical fiber base material.

<Prior art> In an apparatus for heating and melting an optical fiber preform in a heating furnace and drawing an optical fiber, the inner wall of a core tube, which is surrounded concentrically by a heating element and into which the optical fiber preform is inserted, is inside the core tube. In order to prevent the optical fiber from being oxidized and consumed by the oxygen taken into the heating furnace, and to prevent the strength of the optical fiber from decreasing due to dust in the heating furnace, inert gas was traditionally placed horizontally at the top and/or bottom of the heating furnace. 0~60°
The air was blown out in an inclined direction to prevent atmospheric oxygen from flowing into the heating furnace and dust from entering the heating furnace.

<Problems to be Solved by the Invention> An example of such a conventional device is shown in FIG. The inert gas is blown out from the outlet 4 or 4' downward by 0 to 60 degrees from the horizontal (horizontal direction in the example of FIG. 3), and the inert gas blown out is directed toward the optical fiber base material 1 or the optical fiber 3.
The inert gases collide with each other around the inert gas, causing turbulence in the flow and making the flow itself prone to meandering. For this reason, the furnace core tube 6 surrounded by the heater 7 of the heating furnace
A flow containing oxygen in the air mixed in was blown onto the furnace core tube 6, accelerating the wear of the tube wall of the furnace core tube 6. In addition, the dust generated around the core v:6 is blown onto the optical fiber base material 1 or the optical fiber 3, causing a decrease in the strength of the optical fiber 3 or causing uneven temperature distribution in the constriction part 2 of the optical fiber base material 1. This caused variations in the diameter of the drawn wire.

The present invention has been made in view of the problems of the prior art, and provides a method for drawing an optical fiber that reduces the decrease in the strength of the optical fiber, less variation in the diameter of the optical fiber (and less wear and tear on the furnace tube, etc.), and a method for drawing the optical fiber. The purpose is to provide equipment.

Means for Solving the Problems> The method for drawing an optical fiber according to the first invention of the present application which achieves the above object includes inserting an optical fiber preform coaxially into a core tube of a heating furnace, heating and melting it, and performing the above-mentioned method. In a method of drawing an optical fiber by flowing an inert gas into a heating furnace, the inert gas is uniformly blown out parallel to the axis of the core tube of the heating furnace and around the optical fiber preform. It is characterized by this.

The optical fiber drawing method according to the second invention of the present application includes coaxially inserting an optical fiber preform into a core tube of a heating furnace, heating and melting it, and flowing an inert gas into the heating furnace to draw the optical fiber. In the drawing method, inert gas is blown out from one end of the furnace core tube of the heating furnace in parallel to the axis of the furnace core tube and uniformly around the optical fiber preform, and is exhausted from the other end of the furnace core tube. It is characterized in that the gas is exhausted parallel to the axis of the optical fiber.

Further, the optical fiber drawing apparatus, which is the third invention of the present application, inserts an optical fiber preform coaxially into a core tube of a heating furnace, heats and melts it, and flows an inert gas into the heating furnace. Optical fiber 9! The drawing apparatus for drawing wire is characterized in that a plurality of concentric cylindrical outlets coaxial with the axis of the furnace core tube are provided at the upper and lower ends of the furnace core tube of the heating furnace.

Further, the configuration of the optical fiber drawing apparatus according to the fourth invention of the present application is such that an optical fiber preform is coaxially inserted into a core tube of a heating furnace, heated and melted, and an inert gas is flowed into the heating furnace. In a drawing device for drawing an optical fiber, a plurality of concentric cylindrical blow-off ports or exhausts are provided at one end and the other end of the core tube of the heating furnace, and the direction of inert gas blowout or exhaust is parallel to the axis of the core tube. It is characterized by the corresponding arrangement of the mouths.

Embodiment> An embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the structure of an embodiment of an optical fiber drawing apparatus according to the present invention. In FIG. 1, an optical fiber preform 1 is inserted along the tube axis of a furnace tube 6 surrounded by an annular heater 7 of a heating furnace, and its tip is heated and melted at the high temperature of the furnace tube 6.
(A fin 2 is formed, and an optical fiber 3 having a predetermined outer diameter is drawn. At this time, a plurality of fibers coaxial with the tube axis of the furnace core tube 6 provided at the upper part of the heating furnace, that is, at the upper end of the furnace core tube 6. Inert gas g s is discharged from concentric cylindrical outlets 41, 42, and 43
p g 2 ) g 3 is blown out into the reactor core v6 in a laminar flow along the gap between the reactor core tube 6 and the optical fiber preform 1,
The optical fiber preform 1 flows uniformly along the constricted portion 2 of the optical fiber preform 1 and is exhausted from the lower end of the core tube 6 in a substantially laminar flow state.

In this case, since no turbulent flow of inert gas occurs especially in the constriction 2 of the optical fiber preform 1, the temperature distribution in the constriction 2 of the optical fiber preform 1 is maintained uniformly, and light with a uniform outer diameter is maintained. The fiber 3 can be drawn.

The one shown in FIG.
A plurality of concentric cylindrical outlets 41, 4 coaxial with the tube axis of
□, 43 has been described, but a plurality of concentric cylindrical outlets coaxial with the tube axis of the furnace core tube 6 are provided at the lower end of the furnace core tube 6, and a plurality of concentric cylindrical air outlets are provided at the lower end of the furnace core tube 6, and the air outlets are arranged upward parallel to the tube axis of the furnace core tube 6. Even if the inert gas is blown out in a laminar flow state and discharged from the upper end of the furnace tube 6 to the outside air, no turbulence is caused in the constriction 2 of the optical fiber base material, and the same effect as in the above case can be obtained. It will be done.

FIG. 2 is a schematic diagram showing the structure of another embodiment of the optical fiber drawing apparatus according to the present invention. In FIG. 2, the optical fiber preform 1 inserted along the tube axis of the furnace core tube 6 surrounded by the annular heater 7 of the heating furnace is heated and melted in the high temperature part of the furnace core tube 6 heated by the heater 7. Then, the optical fiber 3 is drawn. At this time, in the upper part of the heating furnace, that is, at the upper end of the furnace core tube 6, there are a plurality of concentric cylindrical air outlets 4 coaxial with the tube axis of the furnace core tube 6. 4. 4 are provided,
From them, inert gas g1p g2t g3 is transferred to the furnace core tube 6
It is blown out in a laminar flow along the gap between the optical fiber preform 1 and the optical fiber preform 1. The blown out inert gas flows down in a laminar flow along the gap between the core tube 6 and the optical fiber base material 1, passes near the constriction 2 of the optical fiber base material 1, and flows again into a laminar flow at the lower end of the core tube 6. A plurality of concentric cylindrical exhaust ports 51, 5□ are formed coaxially with the tube axis of the furnace core tube 6 at the lower end of the furnace core tube 6.
, 53, and is discharged from the exhaust port to the outside of the reactor core tube 6.

In the embodiment of the present invention shown in FIG. 2, compared to that in FIG.
A plurality of concentric cylindrical exhaust ports coaxial with the tube axis of the core IrM: 6 similar to the air outlets5. ．． 5□.

5 is arranged, the inert gas at each outlet and exhaust port becomes a laminar flow with the same direction.
The blown inert gas is exhausted in a laminar flow, so that it flows without colliding with the optical fiber preform 1 or with each other. Therefore, the flow of the inert gas in the furnace core tube 6 can maintain a more uniform laminar flow along the optical fiber preform 1 and the optical fiber 3 without causing turbulence or meandering.

In the embodiment of the present invention shown in FIG.
□, 43 are provided, and an exhaust port 5125 is provided at the lower end of the furnace core tube 6.
The explanation has been made for the case where concentric cylindrical air outlets 4□, 42, 4° are provided at the lower end of the furnace core tube 6, and concentric cylindrical exhaust ports 5 are provided at the upper end of the furnace core tube 6. ．． ,5
2.5. A similar effect can be obtained by providing a.

In the embodiment of the present invention shown in FIGS. 1 and 2, the air outlets 41, 4°, 4. Each inert gas g (p g2y g3 flow rate v,, v2. v
Regarding 3, in view of the fact that if the flow velocity of the inert gas flowing in contact with the core tube wall and the outer wall of the optical fiber base material is increased more than necessary, turbulence will occur, so as shown in Figures 1 and 2, Blowout flow velocity v,, v2. Let the velocity distribution of v be v2〉
The laminar flow state of the inert gas in the reactor core tube 6 can be further improved by increasing the flow velocity at the center as shown in v□t v a ) v 3 .

Further, the velocity distribution of the flow velocity at the blowout port and the exhaust port are not the same, and the velocity distribution of the flow velocity at the exhaust port is determined by the expansion of the inert gas due to high temperature heating and the difference in the cross-sectional area of the gas passage. Further, from the viewpoint of laminar flow, it is preferable that the number of each blowout port and exhaust port be large, but the number is determined to be structurally appropriate from the dimensions of the furnace core tube 6 and the optical fiber 1.

Further, the thinner the thickness of the partition wall between the openings constituting the blow-off or exhaust port, the better, but it is necessary to make it as thin as is convenient for the design.

<Effects of the Invention> According to the optical fiber drawing apparatus according to the present invention, by providing a plurality of concentric cylindrical outlets or an outlet and an exhaust outlet in the core tube in the heating furnace, the core tube, the optical fiber preform, and the The flow of inert gas in the gap between the optical fibers can be made into a laminar flow state without generating turbulence, which allows oxygen from the outside air to be taken in and prevents the core tube from being oxidized and consumed. This eliminates variations in the outer diameter of the drawn optical fiber due to uneven temperature distribution at the constriction of the heated and melted optical fiber base material, making it possible to control the wire diameter with extremely high precision, resulting in excellent quality with high precision and high strength. It became possible to produce optical fibers with

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of an optical fiber drawing device according to the present invention, FIG. It is a schematic diagram showing the composition of a wire drawing device. In the drawings, 1 is an optical fiber base material, 2 is a constriction part, 3 is an optical fiber, and 4. ．． 42,4. is the air outlet, 51.5□, 5
3 is an exhaust port, 6 is a furnace tube, and 7 is a heater. Patent application agent Sumitomo Electric Industries Co., Ltd.

Claims (10)

[Claims] (1) In a method in which an optical fiber preform is coaxially inserted into a core tube of a heating furnace, heated and melted, and an inert gas is introduced into the heating furnace to draw an optical fiber, the core tube of the heating furnace is An optical fiber drawing method characterized by uniformly blowing an inert gas out parallel to the axis of the optical fiber and around the optical fiber base material. (2) The inert gas is blown out in a layered manner around the optical fiber preform, giving a predetermined flux distribution of the blowing speed in the radial direction.
Optical fiber drawing method described in section. (3) In a method in which an optical fiber preform is coaxially inserted into a core tube of a heating furnace, heated and melted, and an inert gas is introduced into the heating furnace to draw an optical fiber, the core tube of the heating furnace is Inert gas is blown out from the upper or lower part of the core tube in parallel to the axis of the core tube and uniformly around the optical fiber base material, while exhaust gas is blown out from the lower or upper part of the core tube in parallel to the axis of the core tube. A method for drawing an optical fiber, characterized by evacuation. (4) The inert gas is blown out in a layered manner around the optical fiber preform, giving a predetermined flow velocity distribution of the blowing velocity in the radial direction.
Optical fiber drawing method described in section. (5) In an apparatus for coaxially inserting an optical fiber preform into a core tube of a heating furnace, heating and melting it, and drawing an optical fiber by flowing an inert gas into the heating furnace, the core tube of the heating furnace is A light comprising a plurality of concentric cylindrical outlets coaxial with the axis of the optical fiber base material, which blow out inert gas in a blowing direction parallel to the axis of the core tube, at the upper or lower part. Fiber drawing equipment. (6) The optical fiber according to claim 5, characterized in that the flow velocity of the gas blown out from the plurality of concentric cylindrical outlets has a predetermined flow velocity for each outlet. line drawing device. (7) In a drawing device that coaxially inserts an optical fiber preform into a core tube of a heating furnace, heats and melts it, and draws an optical fiber by flowing an inert gas into the heating furnace, the core of the heating furnace A light source characterized in that a plurality of concentric cylindrical blow-off ports and exhaust ports coaxial with the axis of the core tube for blowing out and exhausting inert gas are arranged at one end and the other end of the tube. Fiber drawing equipment. (8) The optical fiber drawing device as set forth in claim 7, wherein the furnace tube is provided with a blowout port in the upper part and a discharge port in the lower part. (9) The optical fiber drawing device as set forth in claim 7, wherein the furnace tube is provided with a blowout port at the bottom and a discharge port at the top. (10) Claims 7 or 9, characterized in that the flow velocity of the gas blown out from the plurality of concentric cylindrical outlets has a predetermined flow velocity for each outlet. Optical fiber drawing equipment as described.