JP2003342034A - Method and apparatus for drawing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably control the wire diameter in drawing an optical fiber. <P>SOLUTION: The wire diameter of an optical fiber 16 just after drawing is measured with a wire diameter measuring device 5. The wire diameter displacement is divided into 5 steps, step S0 to step S4. PID constants corresponding to each of these steps are input with a touch panel 9 and allotted to these steps. According to the measurement results of the wire diameter, the PID constant is automatically switched with a wire diameter control program 31. Basing on the PID constant, a drive signal is sent from a sequencer 8 to a second motor servo 20, and the take off speed of a take off motor 18 is controlled so as to produce an optical fiber 16 with a desired wire diameter R0. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for drawing a preform into an optical fiber.

[0002]

2. Description of the Related Art When a preform is stretched into an optical fiber, the fiber of the optical fiber is stretched due to a minute difference in molecular weight, a difference in wire diameter, and sometimes foaming caused by heating during the production of the preform. There is a problem of so-called wire diameter deviation in which the diameter deviates from a desired value. This wire diameter deviation not only reduces the value as a product by increasing the optical loss when using it as an optical fiber and causing improper mounting on the connector, but it is also a fatal problem that it cannot be used as an optical fiber. Cause

In the conventional drawing apparatus, the structure shown in FIG. 3 is used to prevent the wire diameter deviation. First, the wire diameter of the optical fiber 101 immediately after drawing is measured by the wire diameter measuring device 102, and the measurement result is converted into a wire diameter measuring signal by the signal converter 103 and transmitted to the sequencer 105 as a feedback signal 104. Then, based on the feedback signal 104, by controlling the output of the motor servo 108 of the take-up motor 107 that drives the take-up roll 106,
The take-up speed of the preform is adjusted so that the desired wire diameter can be obtained. For example, when the optical fiber 101 after drawing is thinner than a desired wire diameter, the wire diameter measurement signal is added as a feedback amount to the take-up speed up to immediately before, and the take-up motor 107 is actuated in the direction of decreasing the rotation speed. In other words, by slowing the take-up speed, the optical fiber 101
Thicken the wire diameter. On the other hand, when the optical fiber 101 is thicker than the desired wire diameter, this adverse effect occurs. At this time, if the take-up speed is simply adjusted only by the proportional portion of the wire diameter displacement, stable control cannot be performed, and
The control is performed using the PID constant of the step.

The optimum value of the PID constant differs depending on various conditions such as the shape of the preform, the drawing speed, the take-up speed, the heating temperature, and the temporal cycle of the wire diameter displacement. Therefore, the conventional stretching device is provided with an input device such as the touch panel 109, and it is possible to input the PID constant with this input device. In this touch panel 109, in addition to setting the PID constant, a reference stretching speed,
It is possible to set a speed correction amount, which is the upper limit of the correction value of the take-up speed, and a time difference correction for performing delay correction from the drawing position to the wire diameter measurement position.

[0005]

The above-described wire diameter control method is effective if the wire diameter displacement has a long time period and the displacement is within the range of the speed correction amount. If there is a large fluctuation with a short cycle, a fluctuation exceeding the control range, or a fluctuation with a short cycle is included in a fluctuation with a long cycle,
There is a problem that a desired wire diameter cannot be obtained stably.
This problem cannot be solved by simply changing the PID constant or the speed correction amount when the shape of the preform or the drawing speed is changed.

An object of the present invention is to provide an optical fiber drawing method and apparatus capable of improving the characteristics of the optical fiber by controlling the diameter of the wire stably.

[0007]

In order to achieve the above object, the present invention provides a method of stretching a preform to form an optical fiber, the step of measuring the diameter of the optical fiber immediately after stretching, Dividing the displacement into two or more steps and assigning PID constants respectively corresponding to these divided steps; automatically switching the PID constant according to the measurement result of the wire diameter; Based on a constant, the step of controlling the speed at which the optical fiber is taken out from the preform so that the optical fiber has a desired diameter is provided.

Further, according to the present invention, in an apparatus for drawing a preform into an optical fiber, a wire diameter measuring means for measuring the wire diameter of the optical fiber immediately after drawing and the displacement of the wire diameter are divided into two or more steps. Then, enter the PID constants corresponding to these divided steps PI
The D constant input means and the P value according to the measurement result of the wire diameter.
PID constant automatic switching means for automatically switching the ID constant, and control means for controlling the speed at which the optical fiber is taken out from the preform so that the optical fiber has a desired diameter based on the PID constant. To do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an optical fiber drawing apparatus according to the present invention. The stretching device 2 includes an elevating device 3, an electric furnace 4, a wire diameter measuring device 5, a take-up roll 6, a winding machine 7, a sequencer 8, and a touch panel 9.
The lifting device 3 includes a lifting motor (M1) 10. The lifting motor 10 vertically moves the clamp holder 12 supporting the preform 11 in the arrow direction. A first pulse generator (PG1) 13 for converting its output into a pulse output is connected to the lifting motor 10. The output signal from the first pulse generator 13 is fed back to the first motor servo (SC1) 14, and the output of the lift motor 10 changes in response to this.

The first motor servo 14 includes a speed setter 1
5 is connected. The drawing speed, which is the reference of the preform 11 and is input to the touch panel 9, is transmitted to the speed setter 15 via the sequencer 8, whereby the speed of the lifting motor 10 is determined via the first motor servo 14. It The clamp holder 12 moves downward at this stretching speed, and the preform 11 is heated by the electric furnace 4. Preform 1 heated to a predetermined temperature in electric furnace 4
No. 1 melts and its tip becomes a meniscus shape, and descends from the tip toward the take-up roll 6 to form the optical fiber 16.

The optical fiber 16 passes through the wire diameter measuring device 5 immediately after the drawing. The wire diameter of the optical fiber 16 is continuously measured online by the wire diameter measuring device 5. The measurement result of the wire diameter is converted into a wire diameter measurement signal by the signal converter 17 and transmitted to the sequencer 8 as a feedback signal.

The take-up roll 6 has a take-up motor (M
2) 18 is provided. This take-up motor 18 has
A second pulse generator (PG2) 19 that converts the output into a pulse output is connected. The output signal from the second pulse generator 19 is the second motor servo (SC
2) It is fed back to 20, and the output of the take-up motor 18 changes accordingly. In addition, the winder 7
A winding motor (M3) 22 controlled by a third motor servo (SC3) 21 is provided. The optical fiber 16 taken up by the take-up roll 6 is continuously taken up by the take-up machine 7. At this time, the winder 7
Is wound with a sufficiently low tension so that the optical fiber 16 is not damaged.

The sequencer 8 incorporates a wire diameter control program (CP) 31 as automatic PID constant switching means. This wire diameter control program 3
1 is the second motor servo 20 based on the feedback signal from the signal converter 17 by the PID constant described later.
Is controlled, and the take-up speed of the preform 11 is adjusted so that a desired wire diameter R0 (see FIG. 2) is obtained.

The touch panel 9 as a PID constant input means has a PID constant for controlling the second motor servo 20, a reference stretching speed, a speed correction amount which is the upper limit of the correction value of the take-up speed, and a line from the drawing position. It is possible to set the time difference correction that corrects the delay to the diameter measurement position.

As shown in FIG. 2, in the wire diameter control program 31, the wire diameter displacement measured by the wire diameter measuring device 5 is divided into five steps S0 around the desired wire diameter R0.
To S4, and for example, as shown in Table 1, PID constants corresponding to these steps S0 to S4 are assigned.

[0016]

[Table 1]

This PID constant is calculated in each step S.
0 to S4 are optimum values for obtaining the desired wire diameter R0, and when the wire diameter displacement is near the desired wire diameter R0 (S
In 0), the filter constant and D value are set to be slightly larger than those in S1 and S2. When the wire diameter displacement is greatly changed (S3, S4), the P value, D
Both values are set extremely high. These PID constants are automatically switched by the wire diameter control program 31 according to the measurement result of the wire diameter. By doing so, it is possible to control the variation of the wire diameter over a wide range. Here, the filter constant is a constant that changes the control amount of the second motor servo 20, and the larger the value, the smoother the control amount. Also, as is well known, P
The ID constant indicates that P is proportional, I is integral, and D is differential. The larger the P value and the D value, the larger the correction output, and the larger the I value, the smaller the correction output.

[0018]

EXAMPLE Next, in the stretching apparatus 2 having the above-mentioned structure, a desired wire diameter R0 = 750 μm and a standard stretching speed = 3.6 m.
/ Min (take-off motor 18 rpm = 387 rp
m), speed correction amount = 35 rpm / step and 105
rpm / full span, time difference correction = 0 sec, the rotation speed of the lifting motor 22 = 758 rpm, and the optical fiber 1
6 was stretched. Further, the number of steps is set to one step (S0) of the related art, speed correction amount = 18 rpm / full span, PID constant = setting corresponding to the case where the temporal period is short and the variation amount of the wire diameter is small (Comparative Example 1), And speed correction amount = 35 rpm / full span, PID constant = setting corresponding to the case where the temporal period is long and the variation amount of the wire diameter is large (Comparative Example 2), and the other conditions are the same as above. It was Table 2 shows the evaluation results of the optical fibers manufactured in these three examples.

[0019]

[Table 2]

In Comparative Example 1, since it is not possible to deal with a case where the time period is long and the variation of the wire diameter is large, the variation of the wire diameter is R0 ± 100 μm or less and the optical loss is 220 to 270 dB.
/ Km is large. Similarly, Comparative Example 2 cannot cope with a case where the time period is short and the variation of the wire diameter is small. Therefore, the variation of the wire diameter is R0 ± 50 μm or less and the optical loss is 20.
It is as large as 0 to 250 dB / km. On the other hand, in the example, the variation of the wire diameter is R0 ± 10 μm or less, and the optical loss is 160 to 1
80 dB / km, which is smaller than that of Comparative Examples 1 and 2. From this result, it was confirmed that the stable control of the wire diameter was performed regardless of the type of fluctuation of the wire diameter, and that the optical fiber with good characteristics could be obtained.

[0021]

As described above, according to the optical fiber drawing method and apparatus of the present invention, the wire diameter of the optical fiber immediately after drawing is measured, and the displacement of the wire diameter is divided into two or more steps. A PID constant corresponding to each of these divided steps is assigned, the PID constant is automatically switched according to the measurement result of the wire diameter, and the optical fiber is taken out from the preform so that the optical fiber has a desired wire diameter based on this PID constant. Since the speed is controlled, stable wire diameter control can be performed. Therefore, it is possible to improve the characteristics of the optical fiber.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical fiber drawing apparatus embodying the present invention.

FIG. 2 is a diagram showing a time change of a wire diameter displacement.

FIG. 3 is a configuration diagram showing a method of controlling a wire diameter in a conventional drawing device.

[Explanation of symbols]

2 Stretching device 5 Wire diameter measuring device (wire diameter measuring means) 6 Take-up roll 8 Sequencer (control means) 9 Touch panel (PID constant input means) 11 Preform 16 Optical fiber 18 Take-up motor 20 Second motor servo 31 Wire diameter control program ( PID constant automatic switching means)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahito Miyoshi             200, Onakazato, Fujinomiya City, Shizuoka Prefecture Fuji Photo             Within Film Co., Ltd. F-term (reference) 4G021 HA05

Claims (2)

[Claims] 1. A method of stretching an optical fiber by stretching a preform, the step of measuring the diameter of the optical fiber immediately after stretching, and the displacement of the diameter is divided into two or more steps, and these divisions are made. Assigning a PID constant corresponding to each step, automatically switching the PID constant according to the measurement result of the wire diameter, and adjusting the optical fiber to a desired wire diameter based on the PID constant. And a step of controlling a speed of taking out from the preform. 2. An apparatus for drawing a preform into an optical fiber, wherein a wire diameter measuring means for measuring the wire diameter of the optical fiber immediately after drawing, and the displacement of the wire diameter are divided into two or more steps, PID constant input means for inputting a PID constant corresponding to each divided step, PID constant automatic switching means for automatically switching the PID constant according to the measurement result of the wire diameter, and based on the PID constant, An optical fiber drawing apparatus comprising: a control unit that controls a speed at which the optical fiber is drawn from a preform so that the optical fiber has a desired wire diameter.