JPH01234341A - Method and device for drawing optical fiber - Google Patents

Abstract

PURPOSE:To uniformize the outer diameter of an optical fiber when drawn by introducing an inert gas into a drawing furnace so that the pressure difference between the outlet side and inlet side is fixed at the time of drawing an optical fiber by the title drawing device. CONSTITUTION:The pressure detectors 20 and 21 having sensors 20a and 21a are set in the gas-sealed airtight members 6 and 7 provided at the upper opening 1a and lower opening 1b of the drawing furnace 1 of an optical fiber drawing device. The pressure of an inert gas G to be supplied to the airtight members 6 and 7 is always detected by the pressure detectors 20 and 21, the detection signal is processed by an arithmetic controller 22 into a processing signal P which is sent to a flow controller 23 to adjust the supply of the inert gas G to the airtight members 6 and 7. As a result, the pressure difference between the vicinity of the upper opening 1a as the inlet side and the lower opening 16 as the outlet side is kept constant. Under such conditions, an optical fiber preform 4 is drawn, and an optical fiber 5 is stably obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical fiber drawing method and a drawing apparatus for drawing an optical fiber with little variation in diameter.

Prior Art> Optical fibers are produced by feeding an optical fiber base material made of quartz or the like from the top of a drawing furnace, heating and melting its tip, and then
The molten portion is drawn from the lower part of the drawing furnace and drawn into a wire by reducing the diameter to a desired diameter.

During this drawing process, the drawing furnace is usually filled with inert gas to prevent the presence of foreign matter, oxygen, etc. in the air around the molten optical fiber tip in the drawing furnace. This prevents the mechanical strength of the optical fiber from decreasing. Also,
In order to prevent variations in the diameter of the optical fiber due to variations in airflow around the heated and melted part of the optical fiber base material in the drawing furnace,
Airtight members with gas seals are provided at the upper and lower ends of the drawing furnace to form a steady flow of inert gas within the drawing furnace and to stabilize the flow of inert gas within the drawing furnace.

FIG. 3 shows such a conventional optical fiber drawing apparatus. As shown in the figure, a heater 2 and a furnace core tube 3 are provided in the drawing furnace 1, and an optical fiber preform 4 is inserted through the upper opening 1a of the drawing furnace 1 and drawn. optical fiber 5
The material is cotton-pulled from the lower opening 1b. Here, in the upper and lower openings 1a and lb of the drawing furnace 1,
Airtight members 6 and 7 with gas seals are provided respectively. These airtight members 6 and 7 have an annular space,
The inert gas G supplied from the gas supply pipes 8 and 9 to these spaces is directed inward from the inner peripheral surfaces 6m and 7m of the airtight members 6 and 7, that is, through the optical fibers located near the upper and lower openings 1a and lb. It is blown onto the outer peripheral surfaces of the base material 4 and the optical fiber 5.

That is, by blowing inert gas G into the vicinity of the upper and lower openings 1a and lb from the inner circumferential surfaces 6a and 7a of these airtight members 6 and 7, the openings 1a and lb are made airtight with the inert gas G in a non-contact state. At the same time, the inside of the drawing furnace 1 is made into an atmosphere of inert gas G. Also, this inert gas G
is supplied from a gas supply device 10, and the gas supply amount of the inert gas G is distributed and adjusted by a gas flow rate setting device 11 so that the flow rate is always constant.

<Problems to be Solved by the Invention> However, in the conventional optical fiber drawing apparatus, since the amount of inert gas G supplied to the airtight members 6 and 7 was constant, for example, when the outside of the optical fiber preform 4 Due to changes in diameter or bending, etc., the clearance between the outer circumferential surface 4a of the optical fiber preform 4 and the inner circumferential surface 6a of the inlet side airtight member 6 changes, resulting in a change in the pressure distribution inside the drawing furnace 1. There is a problem with this.

Therefore, the flow of the inert gas G around the optical fiber preform 4 and the optical fiber 5 changes due to the change in the pressure distribution, which causes a problem that the outer diameter of the optical fiber 5 fluctuates. be.

In view of the above-mentioned circumstances, the present invention has been developed by keeping the pressure distribution and flow of inert gas in the drawing furnace constant even if the supplied optical fiber base material varies, for example, in the outer diameter. An object of the present invention is to provide an optical fiber drawing method and a drawing device that can make the outer diameter of the optical fiber uniform.

<Means for solving AMI> The structure of the optical fiber drawing method of the present invention for achieving the above object is that an inert gas is introduced into the drawing furnace from the inlet side and the outlet side of the drawing furnace. At the same time, in the optical fiber drawing method of heating and melting the optical fiber preform and drawing it in the inert gas atmosphere, the inert gas is used so that the pressure difference between the inlet side and the outlet side of the drawing furnace is constant. The drawing device for the end fiber is characterized by controlling the gas, and heating the optical fiber preform while introducing an inert gas into the drawing furnace from the inlet and outlet of the drawing furnace. In an optical fiber drawing device that melts and draws a wire, it includes a pressure detection means for detecting pressure at an inlet and an outlet of the drawing furnace, and a pressure detection means that calculates the difference between the pressures detected by the pressure detection means and calculates the pressure difference. The present invention is characterized by comprising a control means for controlling the flow rate or pressure of the inert gas introduced into the drawing furnace to a predetermined value.

Function> In an optical fiber drawing device that draws an optical fiber base material, the pressure on the inlet and outlet sides of the drawing furnace is always detected by a pressure detection device, and for example, the pressure on the detected inlet and outlet sides is If a change occurs in the pressure difference, the control means controls the gas supply pan or pressure. As a result, the fluctuating pressure is immediately corrected, and the pressure difference between the inlet side and the outlet side is always maintained at the set pressure difference.

<Embodiment> Hereinafter, a preferred embodiment of an optical fiber drawing apparatus for carrying out the method of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows an optical fiber drawing apparatus according to this embodiment. Note that the same members as those in FIG. 3 according to the prior art are given the same reference numerals and redundant explanations will be omitted.

As shown in the figure, this embodiment has an upper opening 1 of a drawing furnace 1.
& Pressure detection means 20 and 21 having sensor portions 20a and 21g are provided in the gas-sealed airtight members 6 and 7 provided in the lower openings 1b, respectively, and the upper and lower openings 1a in the airtight members 6 and 7 are provided. neighborhood and 1b′ixt! Measure the internal pressure at # and
I am sending it to 2. The arithmetic and control device 22 calculates the pressure difference between the vicinity of the upper opening 1a and the vicinity of the lower opening 1b from this detection result, and also calculates the difference between the calculated pressure difference and a predetermined pressure difference. A processed signal P is output depending on the difference and the fluctuation in either the upper or lower pressure. The processed signal P is transmitted from the inert gas supply device 10 to the gas supply pipes 8 and 9.
The inert gas G is sent to the gas flow rate regulator @#23 which distributes the inert gas G to the airtight members 6 and 7 via the gas. Gas flow j: The regulator 23 separately adjusts the flow rate or pressure of the inert gas G sent to the airtight members 6 and 7 via the gas supply pipe 8.9 in accordance with the processing signal P, and adjusts the supply amount thereof. is designed to be controlled.

Next, an example of the method of the present invention using the optical fiber drawing apparatus of this example will be described.

A pressure detection device 20.21 measures the pressure of the inert gas G supplied to the airtight members 6 and 7 near the upper opening 1a and the lower opening 1b of the drawing furnace 1 for drawing the optical fiber 5.
The arithmetic and control unit 22 performs arithmetic processing on these detection signals. The processing signal P processed here is sent to the gas flow rate regulator 23, which adjusts the amount of inert gas G supplied to the airtight members 6 and 7, so that the amount is always constant. Near the upper and lower openings 1a, and 1
The optical fiber 5 is stably drawn by controlling to maintain the pressure difference with the vicinity of b.

In the description of the optical fiber drawing apparatus of this embodiment, the pressure in the upper and lower openings is controlled by controlling the pressure in the vicinity of the upper opening 1a and the vicinity of the lower opening 1b to a predetermined pressure, respectively. Although the difference is adjusted and controlled to a predetermined pressure difference, the method of the present invention is not limited to this.
For example, these upper and lower openings are 1m.

Adjustment control may be performed so that the pressure difference remains a predetermined pressure difference while the pressure of 1b increases or decreases.

The outer diameter of the optical fiber manufactured in the drawing furnace of this example had a variation range of about 0.5 μm.

This variation range was approximately 173 μm, which was significantly lower than the variation range of about 1.5 μm of the optical fiber manufactured using the conventional drawing furnace described above.

The measurement results of these fluctuation ranges are shown in Figure 2 (al, (b)
). FIG. 2 (al indicates the variation width of the optical fiber produced with the drawing apparatus of this embodiment, and FIG. 2 (bl indicates the variation width of the optical fiber produced with the conventional drawing apparatus).

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, even if the pressure distribution of the inert gas changes due to fluctuations in the outer diameter of the optical fiber base material, the pressure on the inlet side and the outlet side remains constant. Since the difference is always kept constant, the flow of the gas can be kept constant, and the influence of the gas flow on the drawing of the optical fiber can be suppressed. Cotton drawing becomes possible.

[Brief explanation of the drawing]

FIG. 1 shows an optical fiber drawing apparatus according to a preferred embodiment of the method of the present invention, and FIG. 2(a) shows it. (b) is a diagram of measurement data of the outer diameter variation state of the drawn optical fibers according to the present embodiment and the conventional example, and FIG. 3 is a diagram of the optical fiber drawing apparatus according to the conventional example. In the drawing, 1 is a drawing furnace, 2 is a heater, 3 is a furnace core tube, 4 is an optical fiber base material, 5 is an optical fiber, 6.7 is an airtight member, 10 is a gas supply device, 20.21 is a pressure Detector, 22 is an arithmetic and control unit, 23 is a gas flow rate regulator, G is an inert gas, and P is a processed signal.

Claims (1)

[Claims] 1) Light for introducing an inert gas into a drawing furnace from the inlet and outlet sides of the drawing furnace, heating and melting the optical fiber preform in the inert gas atmosphere, and drawing the optical fiber. A method for drawing an optical fiber, characterized in that the inert gas is controlled so that the pressure difference between the inlet side and the outlet side of the drawing furnace is constant. 2) In an optical fiber drawing device that heats and melts an optical fiber preform and draws it while introducing an inert gas into the drawing furnace from the inlet and outlet of the drawing furnace, the inlet of the drawing furnace and a pressure detecting means for detecting the pressure at the outlet, and calculating the difference between the pressures detected by the pressure detecting means and introducing the inert gas into the drawing furnace so that the pressure difference becomes a predetermined value. 1. An optical fiber drawing device, comprising: control means for controlling flow rate or pressure.