JPS60186431A - Apparatus for drawing optical fiber preform - Google Patents

Abstract

PURPOSE:To manufacture an optical fiber having high accuracy, stably, by controlling the intensity of a burner to keep the take-up tension applied to the preform at a constant level in the heat-drawing of an optical fiber preform to an optical fiber. CONSTITUTION:Both ends of the optical fiber preform 1 are clamped with the chuck 12 of the stationary stand 14 and the chuck 12' of the movable stand 14', and the preform 1 is rotated around its axis and is heated and softened by the heating burner moving to the left hand (the direction of the arrow). At the same time, the chuck 12' fixed to the stand 14' is transferred to the right hand to draw the preform 1 and reduce its diameter. In the above method, the tension applied to the preform is measured by the tension meter 20 attached to the stationary stand 14, and the measured value m1 is transmitted to the controlling circuit 22, in which the signal is compared with the standard tension m0 (the sign 24 is comparator and 26 is amplifier). The amount of the fuel supplied to the burner 10 is controlled by the flow controller 18 so as to keep the difference between the measured tension and the standard tension to 0. The take-up tension of the preform 1 can be maintained constantly at the standard tension m0 by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber preform drawing apparatus, and more particularly to an optical fiber preform drawing apparatus that maintains a constant tension in the optical fiber preform.

Generally, optical fibers are made by synthesizing only the core base material by, for example, the VAD method, stretching this core FFJ material once to reduce its diameter, covering it with a quartz tube and crushing it into one piece, and then stretching this optical fiber base material. Manufactured by In the conventional optical fiber preform drawing apparatus, both ends of the optical fiber preform are gripped and rotated by the chucks of a lathe, and one chuck is pulled in the axial direction of the optical fiber preform. It is heated by a heating burner drawn in the opposite direction. In this way, the optical fiber base material is drawn, but in this case, the flow rate of hydrogen and oxygen, which are the fuel of the heating burner, is adjusted so that the temperature of the target object becomes 2000'O, and the argument of the heating burner is The speed Vl is on the order of 1 cm/min, while the chuck take-up speed V2 is (R/r)
It is set to have a relationship of Vl. Note that R is the base material diameter before stretching, and r is the finished diameter after stretching. but,
In the actual manufacturing process, it is necessary to stretch both thick and thin base materials.Furthermore, different materials have different compositions, so their temperature-viscosity characteristics vary greatly and the stretching conditions are different. For this reason, it is necessary to set stretching conditions such as the amount of fuel supplied to the heating burner, the withdrawal speed of the heating burner, the withdrawal speed of the chunks, etc. for each piece of base material, but it is difficult to set these conditions. Waka, Hikari Fa.

If the fiber base material is stretched under inappropriate stretching conditions, it will be heated at an insufficiently low temperature for the stretching process, and if the viscosity is high, slip will occur between the two chucks, or the viscosity will be too low. If heated to a certain degree, an excessive amount of fuel is required, which is uneconomical, and excessive glass volatilization occurs from the surface of the optical fiber base material.

The purpose of the present invention is to discover that if the tension of the optical fiber base material is constant, the drawing can be performed under the best processing conditions, and to maintain the temperature of the heating burner at a predetermined level so as to keep the tension of the optical fiber base material constant. An object of the present invention is to provide an apparatus for drawing an optical fiber preform.

Embodiments of the present invention will be described in detail with reference to the drawings. One drawing shows a drawing device 10 for an optical fiber preform of the present invention, and this drawing device 10 grips both ends of an optical fiber preform l to be drawn. a stand 14, 14' each having two chucks 12, 12', and a take-up drive source (not shown) that takes over the stand 14' so that one chuck 12'' gradually separates from the other chuck 12; , a rotary drive source (not shown) that rotates the chuck 12, 12', and a heating burner 16 that heats the optical fiber material 1 that rotates once. The heating burner 16 is taken up by a power source in a direction opposite to the take-up direction of the stand 14. The heating burner 16 is supplied with fuel consisting of, for example, hydrogen and oxygen.

This heating burner 16 is supplied with fuel regulated by a flow regulator 18 .

The stretching device 10 of the present invention includes a tension measuring device 20 such as a strain gauge provided on a stand 14 on the fixed side to electrically measure the tension of the optical fiber base material l being stretched; a control circuit (control means) 22 that compares the measured value ml from 20 with a tension reference value mO and changes the regulator of the flow rate regulator 18 of the heating/hener 16 so that a tension corresponding to this reference value is obtained; It also has the following. The control circuit 22 includes a comparator 2 that compares the measured value m1 and the reference value mO.
4 and an amplifier 26. Reference value mo can be generated by variable resistor 28.

Therefore, the measured value m1 from the tension measuring device 20 is the reference value mo
, the difference signal mlO is supplied to the flow regulator 18 via the amplifier 26, and the amount of fuel supplied to the heating burner 16 is adjusted so that the tension of the optical fiber base material 1 is constant. In this way, the pulling tension (stretching tension) of the optical fiber base material 1 is kept constant, and the stretching process can be stably performed. This means that the temperature of the heating point at which the heating head 16 heats the optical fiber base material 1 is automatically set according to the diameter and composition of the base material.

To describe a specific example of the present invention, when drawing a quartz-based optical fiber base material with an outer diameter of 25 mm to 15 mm, the pulling speed of the chunk is 28 mm/min while the heating heating speed is 10 mm/min.
mm/min, and the standard tension was set to 5 kg. The average fuel flow rate in this case is 105 liters/min of hydrogen and 3 liters/min of oxygen.
The flow rate was 8 liters/min. In this specific example, when the outer diameter of the base material after stretching was measured over the entire length, the finished outer diameter only varied within ±0.05 mm from the target value of 15.00 mm. Therefore, it can be seen that stretching was possible with extremely high precision.

In order to clarify the effects of the present invention in more detail, a comparative test was conducted as follows. Using a conventional stretching method, that is, a method that does not control tension at all, a 5-wood quartz rod with a diameter of 25 mm was stretched to a diameter of 15 mm by different operators.

The results were as shown in the table below.

Table No., combustion gas amount Finishing accuracy (Rindle 7 minutes) -H202--x concave plate y 1 97 33 ± 0.2 2 115 39 ≦ ± 0.05 3 120 40 ≦ ± 0.05 4 80 29 ± 0. 4 5 103. 37 ± 0.1'' = It is better not to manage the tension as in the past, because the variation in each work unit is large, and if the firepower is below the appropriate firepower (appropriate tension), the finishing accuracy is poor, and - It will be understood that when the accuracy is good, excessive combustion gas is consumed. As is clear from the following two comparisons, the method of the present invention, which automatically maintains the tension at an appropriate value, can prevent variations in each work unit, improve dimensional accuracy, and reduce fuel consumption. I understand.

According to the present invention, as described above, the drawing process can be performed stably, and therefore an optical fiber can be obtained with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of an optical fiber preform drawing apparatus according to the present invention. 1-----1 optical fiber preform, 10-----optical fiber preform stretching device, 12.12''--111 chuck,
l 6---Heating burner. 18-----First flow regulator, 20-----Tension measuring device, 22-----One control circuit (control means). Patent applicant representative Patent attorney Arata Kikuchi

Claims (1)

[Claims] A chuck that grips the optical fiber base material to be drawn, a take-up drive source that pulls one chuck from the other chuck in the axial direction of the optical fiber base material, a rotation drive source that rotates the chuck, and the one chuck. In an optical fiber preform stretching device comprising a drawing direction and a heating burner that heats the optical fiber preform rotating while being gripped by the chuck while being taken in the opposite direction, the tension of the optical fiber preform between the chucks is measured. a tension measuring device that adjusts the fuel flow rate of the heating burner; and a fuel regulator that adjusts the fuel flow rate of the heating burner; and changing the adjusting device of the fuel regulator based on the measured value of the tension measuring device so that the measured value of the tension measuring device becomes a constant value. 1. A drawing device for an optical fiber base material, comprising: a control means.