JPS62153137A - Wire drawing of optical fiber - Google Patents

Abstract

PURPOSE:To rapidly change wire drawing speed while keeping the wire diameter at a constant value, by suitably changing the heating temperature of a preform in changing the wire drawing speed thereof by changing the feed speed of the preform for optical fibers. CONSTITUTION:A preform 2 for optical fibers is fed to a wire drawing furnace 3 at a constant speed, softened and drawn into a fiber while heating with a heating heater 4 and the resultant optical fiber 5 is passed through a coating device 7 and curing furnace 8 to give an element wire 9, while is then wound by a winder 10. In the process, the outside diameter of the optical fiber 5 is measured by a measuring instrument 6 and output to a wire diameter control device 11 to control the wire drawing speed and kept the outside diameter of the optical fiber 5 at a constant value. In the operation, the feed speed of the preform 2 for optical fibers is changed to change the wire drawing speed. In this case, the heating temperature by the heater 4 is suitably changed to move a neck-down part of the preform 2 at a position (b) to a position (a) or (c). Furthermore, the feed rate of an inert gas to be fed to a gap between the preform 2 and the heater 4 can be changed to delicately adjust the heating temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of drawing an optical fiber in which the drawing speed can be rapidly changed as required while keeping the diameter constant.

<Prior Art> As shown in FIG. 5, which shows the schematic configuration of a typical conventional optical fiber drawing apparatus, an optical fiber preform 2 is supplied to a drawing furnace 3 at a constant speed by a preform supply apparatus 1. The optical fiber 5 is drawn while being heated and softened by a heater 4, and then wound by a winder 10 as an optical fiber 5. At this time, the outer diameter of the optical fiber 5 is measured online using a fiber outer diameter measuring device 6 immediately after drawing, and is generally fed back to the winder 10 so that the outer diameter of the optical fiber 5 is constant. Then, the wire diameter control device 11 controls the wire drawing speed. Immediately after the drawn optical fiber 5 is drawn, a coating resin is applied by a primary coating device 7, and the coating resin is cured in a curing furnace 8 to form an optical fiber strand 9.

In such a drawing process, variations in the drawing conditions and resin coating conditions of the optical fiber 5 have a large effect on the quality of the product, and therefore it is necessary to suppress these variations as much as possible. In recent years, the length of the optical fiber 5 per optical fiber preform 2 has been increased to prevent a decrease in the operating rate of the optical fiber equipment and a decrease in the yield of optical fibers caused by installation of the optical fiber preform 2, setup, etc. It's coming.

When the set value of the supply speed of the optical fiber preform 2 during drawing is changed for some reason using such an optical fiber drawing apparatus, the supply speed of the optical fiber preform 2 and the drawing speed of the optical fiber 5 at this time are changed. As shown in Figure 6, which shows the relationship between
t2 is t1 at which the time required for opening the optical fiber ends
It is the time when a stable drawing state is entered after t4
is the manufacturing end time t3 of a product with stable line drawing
This is the time when the drawing speed has been changed to another one in response to the change in the supply speed of the optical fiber preform 2. These t2F
The time t4 is a transitional period until the drawing speed of the optical fiber 5 is changed to another stable drawing speed in response to a change in the supply speed of the optical fiber preform 2, and during this period, the However, the dimensional accuracy is not stable, leading to a decrease in yield.

<Problems to be Solved by the Invention> In the conventional optical fiber drawing apparatus shown in FIG. 5, the feeding speed V of the optical fiber preform 2 and the drawing speed V of the optical fiber 5
, there is the following relationship in a steady state where stable line drawing is performed.

d-V=d-V However, 4 is the outer diameter of the optical fiber preform 2, d( is the outer diameter of the optical fiber 5, 马 is the supply speed of the optical fiber preform 2, and ■ is the drawing speed of the optical fiber 5. Normally, outside the supply speed of the optical fiber preform 2, the drawing speed of the optical fiber 5 is generally v,
(approximately 20 meters per minute). In addition, the drawing speed V of the optical fiber 5 has been increased in recent years.
The rate is increasing due to improvements in drawing technology, and is 200 per minute.
It has become possible to exceed meters.

Conventional optical fiber drawing equipment controls the drawing speed so that the outer diameter of the optical fiber is constant, and draws vP in steps outside the supply speed of the optical fiber preform 2 as shown in FIG.
, to increase from vP□ or decrease from Vp□ to vPl, the drawing speed vL of the optical fiber changes from low speed v, 1 to high speed ■, 2, or from high speed vI2 to low speed v, 1.

At this time, the drawing speed V of the optical fiber 5 cannot immediately follow the change in the supply speed v2 of the optical fiber preform;
This will involve a transient period with a time delay of 2.14.

The length of this transition period is related to the heating state of the optical fiber preform, its outer diameter, and the outer diameter noise of the optical fiber.

In the optical fiber drawing apparatus shown in FIG. 5, the outer diameter d of the optical fiber preform 2 is 24 mm, the outer diameter d of the optical fiber 5 is 125 um, and the supply speed of the optical fiber preform 2 is VP, = 0.54 mm/min to V = 2
．． FIG. 7 shows the response pattern of the drawing speed (■) when the drawing speed was increased stepwise to 17 mm/7 min.

Conversely, the supply speed v2 of the optical fiber preform 2 is set to vp□=2.
FIG. 8 shows the response of the drawing speed V when the drawing speed was lowered stepwise from 17 speeds/minute to V=0.54 speeds/minute. According to this, the response time for drawing speed ■ when going up is about 7 minutes, and the response time for drawing speed & when going down is about 10 minutes.
It takes minutes. The optical fiber 5 drawn during this response period becomes a scrap wire that cannot be shipped as a product because the product accuracy is not guaranteed, and the amount of scrap wire for these wires is about 340 m and about 390 m, respectively.

As the demand for optical fiber increases, the manufacturing speed of optical fiber is increasing in order to reduce its cost, but as a result, the proportion of waste radiation of such optical fiber increases and the yield decreases. The issue of doing so has become important.

The present invention was made in view of the deficiencies of the prior art, and makes it possible to rapidly change the drawing speed while keeping the outer diameter of the optical fiber constant, thereby significantly reducing the amount of waste. The purpose is to provide a fiber drawing method.

Means for Solving Problems> The method for drawing an optical fiber according to the present invention is such that when heating and melting an optical fiber preform and drawing it into an optical fiber, the supply speed of the optical fiber preform is adjusted to the first supply speed. When the drawing speed of the optical fiber is changed from the first drawing speed to the second drawing speed by changing the feeding speed from the first feeding speed to the second feeding speed, the heating temperature of the optical fiber preform is changed to change the drawing speed of the optical fiber. This is characterized in that the outer diameter of the optical fiber is kept constant.

<Function> In the optical fiber drawing method according to the present invention, when the supply rate of the optical fiber preform is changed, the heating rate of the optical fiber preform is also changed at the same time. That is, when increasing the optical fiber drawing speed V by increasing the supply speed of the optical fiber preform, the heating temperature of the optical fiber preform is increased, and conversely, when it is desired to decrease the supply speed V of the optical fiber preform. In this case, the heating temperature of the optical fiber preform is lowered.

The first diagram representing the principle of the optical fiber drawing method according to the present invention
As shown in the figure, when the optical fiber preform 2 is being drawn in a steady state by heating from the heater 4, and the neck-down part of the optical fiber preform 2 is at position b, the light to the heater 4 is If the relative position of the fiber preform 2 is moved to position C, the time the optical fiber preform 2 is exposed to the heater 4 becomes longer, the amount of melting of the optical fiber preform 2 increases, and the line of the optical fiber 5 increases. Since the diameter is about to be increased, the wire diameter control device 11 (see FIG. 5) acts to increase the wire drawing speed. That is, the drawing speed of the optical fiber 5 changes to a faster drawing speed than in the steady state. On the other hand, if the relative position of the optical fiber preform 2 is forcibly moved from the state b to the position a, the amount of heat that the optical fiber preform 2 receives from the heater 4 will decrease, so the optical fiber 5 will be drawn at a constant drawing speed. The diameter of the optical fiber 5 decreases when it is drawn, so the diameter control device 11 lowers the drawing speed to keep the diameter constant, and the drawing speed of the optical fiber 5 is set to a drawing speed that is lower than the steady state. Changes to In any of the above cases, b
If the relative displacement from the state is large, it is possible to change the drawing speed to a large extent correspondingly. However, even if the amount of displacement is large, if there is no change in the heating amount and supply speed of the optical fiber preform 2, it will take time to return to the steady state.

Furthermore, the relative position of the neck-down portion of the optical fiber preform 2 with respect to the heater 4 depends on the heating temperature by the heater 4, so when the temperature of the heater 4 is increased, the neck-down portion moves to position a, causing the heater temperature to increase. If it is lowered, it moves to position b. This is because the optical fiber preform 2 forms a neck-down in the heating temperature range formed by the heating element 4.

That is, by changing the heating temperature of the optical fiber base material 2 by the heater 4, the position of the neck-down part in the steady state shown in FIG. 1 is changed from b to a or C, and the transient state is forcibly changed. This makes it possible to rapidly change the drawing speed.

In this case, the heating temperature of the optical fiber base material 2 can be changed by adjusting the power supplied to the heater 4, but generally the heater 4 is covered with a heat insulating material and has a large heat capacity, and the heater 4 and the optical fiber base material 2, the heating temperature of the optical fiber preform 2 changes more slowly with respect to the temperature change of the heater 4 due to changes in the supplied power. Note that an inert gas for preventing oxidation is supplied between the optical fiber base material 2 and the heater 4, and by changing the amount of gas supplied, the heating temperature of the optical fiber base material 2 can be adjusted slightly. It can be adjusted to

<Example> FIG. 2 shows the relationship among the optical fiber preform supply speed, heater supply power, inert gas injection amount, optical fiber preform heating temperature, and optical fiber drawing temperature according to an embodiment of the method of the present invention. and as shown in FIG. 1, the supply speed of the optical fiber preform 2; 2. At 1.7 o'clock, the power supply to the heater 4 of the drawing furnace 3 (see FIG. 5) was changed stepwise from P1 to P2. As a result, the heating temperature of the optical fiber preform 2 is gradually increased from T1 to T2, and at the same time, the drawing speed V of the optical fiber 5 is accelerated, and the drawing speed V passes through a transient period and reaches a steady state of low speed vi at time t2'. Rapidly from state drawing speed to high speed vi
It is possible to change the steady-state drawing speed to 2.

Next, at time t3', the supply speed ■ of the optical fiber preform 2 is set to vP
The heating temperature of the optical fiber preform 2 is increased from T2 by decreasing the heating temperature of the optical fiber preform 2 in a stepwise manner from 2 to vP and gradually increasing the amount of inert gas blown from q to q to increase the cooling effect of the optical fiber preform 2. T, thereby decelerating the drawing speed V of the optical fiber 5, and changing from the steady state vi2 to (1) during the transient period t4'. Be able to rapidly decelerate.

In this embodiment, the supply speed V of the optical fiber preform 2 is V. As a means of increasing the heating temperature of the optical fiber preform 2 at the same time as increasing the temperature, the power supplied to the heater 4 is changed from Pl to 2.
2, the heating temperature of the optical fiber preform 2 can also be increased by adjusting the amount Q of inert gas blown instead. Of course, these means may be used in combination. Similarly, when lowering the optical fiber preform 2 at a rate other than the supply speed, the heating temperature of the optical fiber preform 2 may be lowered by changing the power supplied to the heater 4 or the amount Q of inert gas blown. It is also possible to use them together.

Experimental Example 1 In the optical fiber drawing apparatus shown in Fig. 5, the outer diameter is 24 mm.
A millimeter optical fiber preform 2 is supplied to a drawing furnace 3,
When drawing an optical fiber 5 with an outer diameter of 125 micrometers while controlling the wire diameter, the feeding speed of the optical fiber preform 2 is increased stepwise from 0.545'J meters per minute to 2.17 mm, and at the same time. , the flow rate of nitrogen gas flowing through the drawing furnace 3 was decreased from 10.51 Jttle per minute to 10.2 liters per minute, and the heating temperature of the optical fiber preform 2 was increased from 2210°C to 2240°C. . In this case, compared to the case where the heating temperature of the optical fiber preform 2 is not changed as shown in FIG. is approximately 2 minutes, which is approximately 1
It was shortened to /4. The experimental results at this time are shown in Figure 3, and the debris radiation dose during the transient period was only about 70 meters. Therefore, by increasing the heating temperature of the optical fiber base material 2 by decreasing the amount of inert gas around the optical fiber base material 2, the amount of waste radiation is significantly reduced compared to the conventional case where the heating temperature is not changed. I was able to reduce it.

Experimental Example 2 In the optical fiber drawing apparatus shown in Fig. 5, the outer diameter is 24 mm.
A millimeter optical fiber preform 2 is supplied to a drawing furnace 3,
When drawing the optical fiber 5 with an outer diameter of 125 micrometers while controlling the wire diameter, the supply rate of the optical fiber preform 2 was varied from 2.17 millimeters per minute to 0.1 millimeters per minute.
54 mm in steps, and the power supplied to heater 4 from 12.5 kW to 12.2 kW.
The heating temperature of the optical fiber preform 2 was lowered from 2150°C to 2100°C by decreasing the heating temperature in kilowatt hours in steps. This rapidly reduced the drawing speed of the optical fiber 5 from 80 meters per minute to a steady state drawing speed of 20 meters per minute, and the time required for this transition period was approximately 4 minutes. Compared to the conventional case in which the heating temperature of the optical fiber preform was not changed, the drawing speed could be rapidly reduced as shown in FIG. As a result, the amount of waste radiation generated during the transition period was also significantly reduced.

<Effects of the Invention> According to the optical fiber drawing method of the present invention, the optical fiber is drawn in a steady state while heating and melting the optical fiber base material and maintaining the outer diameter of the optical fiber at a predetermined size using an outer diameter control device. When changing the optical fiber drawing speed to another value by changing the supply speed of the optical fiber preform, the heating temperature of the optical fiber preform should also be changed, so the drawing speed should be changed rapidly. It is now possible to match the drawing speed of optical fiber. Therefore, the amount of waste radiation when changing the drawing speed is extremely reduced, making it possible to manufacture optical fibers with a high yield.

[Brief explanation of drawings]

FIG. 1 is a conceptual work diagram showing the principle of the optical fiber drawing method according to the present invention, FIG. 2 is a graph showing the control state of control factors in an embodiment of the optical fiber drawing method according to the present invention □, and FIG. Figures 4 and 4 are graphs showing changes in optical fiber drawing speed in experimental examples of the present invention, Figure 5 is a conceptual diagram of the optical fiber drawing device that is the object of the present invention, Figure 6
is a graph showing the relationship between the supply speed of the optical fiber preform and the drawing speed of the optical fiber, and FIGS. 7 and 8 are graphs showing actual experimental examples of changes in the drawing speed of the conventional optical fiber. In the drawings, 1 is an optical fiber preform supply device, 2 is an optical fiber preform, 3 is a drawing furnace, 4 is a heater, 5 is an optical fiber, and 11 is a wire diameter control device. Figure 2

Claims (2)

[Claims] (1) When heating and melting the optical fiber preform and drawing it into an optical fiber, the drawing speed of the optical fiber is changed by changing the supply speed of the optical fiber preform from the first supply speed to the second supply speed. When changing the drawing speed from the first drawing speed to the second drawing speed, the heating temperature of the optical fiber preform is changed so that the outer diameter of the optical fiber to be drawn is kept constant. How to draw fiber. (2) The heating temperature of the optical fiber preform is controlled by changing the flow rate of the inert gas fed between the optical fiber preform and the heater that heats the optical fiber preform. A method for drawing an optical fiber according to claim 1.