JPS6250419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for drawing optical fiber, and is capable of reducing defective portions by controlling the drawing speed.

In the production of optical fibers, a base material is heated and softened and drawn to a desired outer diameter, and this fiber is coated to produce an optical fiber strand.

A typical conventional optical fiber drawing device used for drawing optical fibers supplies an optical fiber base material 2 to a heater 3 at a constant speed by a base material supply device 1, as shown schematically in FIG. Then, the heated and softened base material 2 is drawn with a winder 6 to obtain a fiber 4. At this time, the fiber outer diameter is measured online by the fiber outer diameter measuring device 5 immediately after drawing.
The signal is normally fed back to the winder 6, and the drawing speed is controlled so that the outer diameter remains constant. Then, the drawn fiber 4 is immediately coated with a coating resin liquid 8 using a primary coating die 7 and heated and cured in a resin curing furnace 9 to obtain a fiber strand 10 whose periphery is protected by resin.

In this wire drawing process, fluctuations in the wire drawing conditions from the base material and the resin coating conditions have a great effect on the quality of the product, so it is necessary to keep them as constant as possible. In addition, since it is very difficult to continuously supply optical fiber base materials, the base material is usually made larger and the single length of the fiber becomes longer. The increase in defective parts (fiber scrap) is suppressed.

However, the drawing conditions in conventional wire drawing equipment change as shown in Figure 2 a and b, where a is the setting condition for the base material supply speed, and b is the fiber drawing speed corresponding to the base material supply speed. This shows the changes in In addition, Vp ₁ and Vp ₂ in the figure represent the base material supply speed,
Vf ₁ and Vf ₂ are the fiber drawing speeds, t ₁ is the time required to draw the fiber, t ₂ is the time required to reach stable product manufacturing conditions after drawing the fiber, and t ₃
indicates the product manufacturing time, and _t4 indicates the time required to stop the equipment.

Further, in a steady state, the following relationship holds true between the supply speed Vp of the base material and the drawing speed Vf of the fiber.

dp ² · Vp = df ² · Vf where dp is the diameter of the base material and df is the diameter of the fiber.

In normal wire drawing, the base material supply speed Vp is set to Vf ₁ of approximately 20 m/min or less,
Vf ₂ has increased with recent improvements in drawing technology,
It is now possible to increase the speed to over 100m/min.
Therefore, the step response time of the fiber drawing speed to the change in the base material supply speed when the fiber outer diameter is controlled to be constant, that is, the time t ₂ in FIG. 2b.
and t ₄ vary depending on the heating condition of the base material and the outer diameters of the base material and fiber. For example, set the line drawing condition to
FIG. 3 shows the response of the fiber drawing speed Vf when dp = 24 mm and df = 125 μm and Vp was increased stepwise from 0.54 mm/min to 2.17 mm/min. Also, in Figure 4, Vp = 2.17mm/min to 0.54mm/
An example of the response when lowered in steps per minute is shown below. As can be seen from these figures, the response time for ascent takes about 7 minutes, and the response time for descent takes about 10 minutes, and occurs during that time. The defective parts of the optical fibers are approximately 340 m and 390 m long, respectively, which are extremely long, and it is desired to develop a drawing method that can reduce this length.

The present invention was made in view of these needs, and by controlling the position of the base material, it is possible to shorten the response time to a fraction of the above, and to significantly reduce the number of defective parts of the fiber that occur during that time. The object of the present invention is to provide a wire drawing method, and the structure of the wire drawing method that achieves this purpose is to control the position of the base material relative to a heating heater by rapidly changing the feed rate of the base material when heating and drawing the optical fiber base material. It is characterized by the following.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIGS. 5a, 5b, and 5c are schematic explanatory diagrams of the optical fiber drawing method of the present invention. This figure shows an example of a case where the wire drawing speed is rapidly changed while controlling the wire diameter to be kept constant.

In the wire drawing method of the present invention, first, the base material supply rate Vp is maintained until the time T ₁ required for drawing out the fiber.
Set it to Vp ₃ and low speed. The fiber drawing speed Vf at this time was also low at Vf ₃ , and
As shown in the figure, the position of the base material 2 supplied to the heater 3, that is, the position of the base material drawing-off part X, is set at a fixed position, and the wire drawing process is similar to the conventional wire drawing process.

From this state, conventionally the base material supply speed Vp was reduced to Vp ₅
However, at this speed, many fibers are wasted before a stable product can be obtained. Therefore, the base material supply rate Vp is rapidly increased to Vp ₄ and maintained until time T ₂ . At this time, the fiber drawing speed Vf ₄ changes as shown in FIG. 5c. This change has a slope corresponding to Vp ₄ . Also, the base material withdrawal part position
X ₁ in the drawing direction as the base material supply speed Vp ₄ changes
move only. Rather than moving as the base material supply speed Vp changes,
This change in position X occurs in order to change Vp.

Next, the base material supply speed Vp is returned to the low speed Vp ₃ again until time T ₃ , so that the fiber drawing speed Vf remains constant at the required speed Vf ₄ . After this,
As before, if _{the base material supply speed Vp is maintained from time T 3 ,} the fiber drawing speed Vf is reduced to the required speed Vf.
can be stabilized.

On the other hand, when the base material runs out and the wire drawing process is to be stopped, contrary to the _above , the base material drawing _part position The temperature is changed to O in a pulsed manner. As a result, the fiber drawing speed changes in accordance with the response characteristic of the base material supply speed Vp ₆ and stops in a short time.

Next, a specific example of the present invention will be explained with reference to FIG.

The drawing conditions shown in the same figure are the diameter of the base material dp = 24
mm, fiber diameter df = 125 μm, drawing speed
Vf=80m/min.

The base material supply speed Vp at this time was maintained at Vp ₃ = 0.54 mm/min to Vp ₄ = 40 mm/min for 9 seconds, and after 1.5 minutes, was changed to Vp ₅ = 2.17 mm/min, and the result was
This is indicated by a solid line a in the figure. In this case, the drawing speed
It took approximately 2.5 minutes for Vf to stabilize at 80 m/min, and the amount of debris radiation generated during that time was extremely small at approximately 130 m/min.

In addition, the broken line b in the same figure indicates the base material supply speed Vp by 2.
The graph shows the change in fiber drawing speed when the holding time is doubled, but since the amount of change in the position of the drawing part of the base material is the same, the change is the same as that of the solid line a.

Figure 8 shows an example when the drawing speed is reduced, where the diameter of the base material dp = 24 mm and the diameter of the fiber df = 125.
The conditions were the same as in the case of μm and FIG. 7, and the base material supply rate Vp was maintained at Vp ₆ =40 mm/min for 7 seconds. As a result, the fiber drawing speed Vf is 80 after 1.5 minutes.
m/min to 20m/min, and the generated waste dose is approximately
It has become extremely short at 45m.

FIG. 9 is a schematic diagram of an embodiment of an apparatus for carrying out the optical fiber drawing method of the present invention.
In addition, in the figure, parts that are the same as before are marked with the same symbols,
Explanation will be omitted.

The base material supply device 11 is composed of a main feed device 12 and a sub-feed device 13. The main feed device 12 provides a steady supply speed Vp to the base material 2, and the sub-feed station 13 is configured to provide a steady supply speed Vp to the base material 2. It is possible to move the base material 2 up and down at a speed several times faster than that of the base material 2.

Therefore, the fiber drawing speed can be rapidly reduced or increased by means of the sub-feed station 13.

As described above in detail with the embodiments, according to the present invention, the response time of the fiber drawing speed can be shortened, and the amount of fiber waste generated during this time can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional optical fiber drawing device, Figures 2a and b are explanatory diagrams of base material supply speed and fiber drawing speed under conventional drawing conditions, and Figures 3 and 4 are diagrams of conventional optical fiber drawing equipment. Graphs showing experimental results of fiber drawing speed in different drawing methods, Figures 5a, b,
c is a schematic explanatory diagram of the method of the present invention, FIG. 6 is an explanatory diagram of the position of the base material drawing part, FIGS. 7 and 8 are graphs showing the experimental results of the fiber drawing speed by the method of the present invention, and FIG. 1 is a schematic diagram of an apparatus for carrying out the optical fiber drawing method of the present invention; FIG. In the drawing, 2 is an optical fiber base material, 3 is a heater, 4 is a fiber, 5 is a fiber outer diameter measuring device, 6
is the winding machine, 7 is the primary coating die,
8 is a coating resin liquid, 9 is a resin curing furnace, 10
11 is the fiber raw wire, 11 is the base material supply device, 12 is the main feeding station, 13 is the sub-feeding station, Vp, Vp ₁ to Vp ₆ are the base material feeding speed, and Vf, Vf ₁ to Vf ₄ are the fiber drawing speeds. , X, X ₁ ~ _{X 2} is the position of the base material withdrawal part, T ₁
~T ₆ is the time.

Claims (1)

[Claims] 1. A method for drawing an optical fiber by heating, the method comprising: rapidly changing the supply speed of the preform to control the position of the preform relative to a heater;