JPS62226834A - Optical fiber drawing device - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having uniform outer diameter by detecting the internal pressure of a wire drawing furnace into which an inert gas has been introduced, controlling the flow rate of the inert gas based on the difference between the internal pressure and a specified pressure value, and drawing a preform. CONSTITUTION:An inert gas such as a gaseous He-Ar mixture is introduced into a carbonaceous furnace core tube 2 in the wire drawing furnace 1 from an inner gas feeder 7 through a gas flow controller 6 and gas blowoff pipes 4 and 5. The pressure value in the furnace core tube 2 detected by a pressure gage 9 is outputted to a controller 10, the difference between the pressure value and the preset specified pressure value is calculated, a control signal designating a gas flow rate based on the difference is outputted from the gas flow controller 6 to control the flow rate of the gas to be introduced into the furnace core tube 2 from the blowoff pipes 4 and 5, and the internal pressure of the furnace core tube 2 is kept at the set value. The preform 11 consisting of a multilayer vitreous material is inserted into the furnace core tube 2 from the upper part of the furnace 2, a heater 3 is energized to heat the preform to >=2,000 deg.C, and an optical fiber 12 is drawn while melting the preform 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber drawing device, and particularly to a control device for stabilizing the internal pressure of a drawing furnace.

[Prior Art] FIG. 3 shows the groove configuration of a conventional optical fiber drawing device. A preform 33 is inserted into a furnace core tube 32 installed in a drawing furnace 31, and a heater 3 is placed on the outer periphery of the furnace core tube 32.
4, the preform 33 is heated while heating the inside of the furnace tube 32.
The optical fiber 35 was obtained by drawing. At this time, in order to stably melt and draw the preform 33, an inert gas such as Ar was introduced into the furnace tube 32 from gas blowers 36 and 37.

[Problem to be Solved by the Invention 1] However, the inert gas flow flowing inside the reactor core tube 32 tends to fluctuate due to various factors, and as a result of (a), the internal pressure of the reactor core tube 32 also fluctuates, resulting in 1! ? optical fiber 3
A problem has arisen in that the outer diameter of the tube 5 is non-uniform.

The causes of fluctuations in the inert gas flow include: (1) temperature fluctuations in the core tube 32 due to fluctuations in the supply current that operates the heater 34 and deterioration of the heater 3/I; (2) bending of the preform 33 and irregularities on its surface; ■Changes in inert gas supply pressure, etc.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical fiber drawing apparatus that can solve the problem f+ (of the prior art described above) and make the outer diameter of the optical fiber uniform.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the optical furnace/iva wire drawing apparatus of the present invention includes a pressure detection means for detecting the internal pressure of the drawing furnace, and a pressure detection means for detecting the internal pressure of the drawing furnace. A control means is provided for calculating the difference between the two so that the internal pressure becomes a predetermined pressure value, and controlling the flow rate of the inert gas introduced into the drawing furnace based on this difference.

[Operation 1] With the above configuration, the internal pressure of the drawing furnace is detected by the pressure detection means, and the drawing furnace is controlled by the control means based on the difference between this internal pressure and a predetermined pressure value (set value). The inert gas flow q introduced into the chamber is controlled. As a result, fluctuations in the inert gas flow are suppressed and the preform is melt-drawn in a stable manner, making it possible to obtain an optical fiber with a uniform outer diameter.

[Example] Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an optical fiber drawing apparatus according to an embodiment of the present invention. A carbon core tube 2 is installed in the drawing furnace 1.
A heater 3 for heating is arranged on the outer periphery of the furnace core tube 2. Gas blowers 4 and 5 are installed at the upper and lower portions of the furnace core tube 2, respectively, and a gas flow R adjustment lever 6 is connected to these gas blowers 4 and 5 via a supply pipe. Furthermore, an inert gas supply VS7 is connected to this gas flow m regulator 6. Further, an outlet 8 for detecting the pressure inside the tube is opened at the lower part of the core tube 2, and a pressure gauge 9 is provided at the outlet 8.

Then, the output of the pressure gauge 9 is connected to the controller 10, and the output of the pressure gauge 9 is connected to the controller 10.
The output of Il device 10 is connected to gas flow I11 regulator 6.

Note that it is desirable that the outlet 8 be provided at the lower part of the furnace core tube 2 so as not to affect the gas flow within the furnace core tube 2.

Next, the operation of this embodiment will be explained.

First, a combined He-Arf1 gas is introduced into the entire gas pipe 2 from the inert gas supply device 7 via the gas flow m regulator 6 and the gas blower 4.5. At this time, the pressure inside the reactor core tube 2 is detected by the pressure gauge 9, and a detection signal indicating this pressure value is outputted from the pressure gauge 9 to the controller 10. The controller 10 to which the detection signal is input calculates the difference between the detected pressure value and a preset value, and further outputs a control signal specifying the gas flow rate based on this difference to the gas flow regulator 6. be done. Then, the gas flow rate controller 6 controls the gas flow rate introduced into the reactor core tube 2 based on the m control signal. In this way, the internal pressure of the furnace tube 2 is always maintained at the set value.

In this state, the preform 1 made of multilayer glass material
1 is inserted into the furnace core tube 2 from above and the heater 3 is activated to heat the furnace core tube 2 to a high temperature of 2000° C. or higher. As a result, the preform 11 is melted and drawn, and the optical fiber 12 is pulled out from the lower part of the furnace tube 2.

At this time, even if the preform 11 is bent or uneven, or the heating temperature by the heater 3 fluctuates, the pressure gauge 9. Since the internal pressure of the reactor core tube 2 is maintained at a set value by the controller 10 and the gas flow rate regulator 6, fluctuations in the outer diameter of the optical fiber 12 are suppressed.

Using a sizing device as shown in FIG.
mm, the outer diameter of the optical fiber 12 is 125tI11. The wire drawing operation was performed at a drawing speed of GO1rL/1ain. When the gas flow j was not controlled as in the conventional case, the maximum variation in the outer diameter of the optical fiber 12 was 1.5 Im, as shown in FIG. 2(a). On the other hand, when the gas flow is controlled based on the present invention by setting the internal pressure to 5#1111120 and setting the flow rate change to 250cm3/n1in, as shown in Fig. 2(b). optical fiber 12
The outer diameter variation was 0.5p at maximum.

[Effects of the Invention] As explained above, according to the present invention, the following excellent effects are exhibited.

By controlling the amount of inert gas introduced into the drawing furnace, the internal pressure of the drawing furnace can be maintained at a predetermined pressure value. Therefore, even if there is a change in the current supplied to the heater, deterioration of the heater, bending or unevenness of the preform, fluctuations in the inert gas supply pressure, etc., the pressure inside the drawing furnace is maintained at a constant level, and as a result, the drawing furnace is maintained at a constant pressure. This improves the uniformity of the outer diameter of the optical fiber obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical fiber drawing device according to an embodiment of the present invention, and FIGS. 2(a) and (b) show variations in the outer diameter of an optical fiber drawn by the conventional method and the device of the present invention, respectively. FIG. 3 is a configuration diagram of a conventional example. In the figure, 1 is a drawing furnace, 6 is a gas flow regulator, 9 is a pressure gauge,
10 is a controller, and 11 is a preform.

Claims (1)

[Claims] In an optical fiber drawing apparatus that introduces an inert gas into a drawing furnace and draws a preform in the gas atmosphere, a pressure detection means detects the internal pressure of the drawing furnace, and the pressure detection means detects the internal pressure of the drawing furnace. A control means for calculating the difference between the internal pressure and the predetermined pressure value so that the internal pressure obtained becomes a predetermined pressure value, and controlling the flow rate of the inert gas introduced into the drawing furnace based on the difference. An optical fiber drawing device comprising: