JPS63265838A - Method for drawing optical fiber - Google Patents

Abstract

PURPOSE:To reduce the defective products, to simplify the control system, and to reduce the equipment cost by changing the feed rate of a base material in the previously calculated pattern, and controlling the outer diameter of the optical fiber by the control system with the drawing rate as a manipulated variable. CONSTITUTION:An optical fiber base material 1 is sent to a heating furnace 3 by an optical fiber base material feeder 2, and the heated and melted part at the tip is drawn as an optical fiber 4 at a rate higher than that of the base material. An UV curing resin or a thermosetting resin, etc., are then coated by a coating device 5, and the coated resin is cured by a curing furnace 6 to obtain a coated optical fiber 7. The fiber is received by a takeup capstan 8 and wound on a winder 9. In this method, the optical fiber base material feed rate and the temp. of the heating furnace are changed in the pattern previously calculated from the set values of the drawing rate, outer diameter of the optical fiber, and drawing tension. At the same time, the outer diameter of the optical fiber is constantly controlled by the control system with the drawing rate as a manipulated variable, and the operation is stationarily carried out or stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a control method when drawing an optical fiber.

C) Prior art) The most important point in so-called optical fiber drawing, in which an optical fiber preform is inserted into a heating furnace from its lower end and an optical fiber is spun from the heated part, is to minimize the outer diameter of the optical fiber and the drawing tension. The purpose is to quickly stabilize the set value.

By the way, in the conventional drawing method, the feeding speed of the optical fiber preform to the heating furnace and the drawing speed are respectively increased at a constant gradient from the value at the preparatory stage to a predetermined value, and the drawing speed is increased at a constant gradient. After reaching , it was held constant and waited until the outer diameter of the optical fiber reached a predetermined value.

However, this method has the problem that it takes too much time to reach a steady operating state, and all the optical fibers during that time are defective.

Therefore, the inventor first raised or lowered the feeding speed of the optical fiber preform to the heating furnace (hereinafter simply referred to as the optical fiber preform feeding speed) in a fixed pattern, and adjusted the optical fiber outer diameter and drawing tension. We proposed a method to start up or stop the process while keeping it constant by changing the drawing speed and heating furnace temperature.

However, even in the above-mentioned method, fluctuations in the drawing speed and heating furnace temperature, which are the manipulated variables, may become large or a saturation state may occur. Furthermore, there is also the problem that the control system becomes complicated and the equipment cost increases.

[Purpose of the invention]

In view of the above-mentioned problems, an object of the present invention is to shorten the time required for starting up, speeding up, stopping, and decelerating when drawing optical fibers, thereby reducing product defects and improving the control system. The purpose is to reduce the number of N and reduce equipment costs.

[Structure of the invention]

In order to achieve the above object, the present invention manufactures an optical fiber by feeding an optical fiber preform into a heating furnace, heating it, and drawing the heated portion at a speed faster than the feeding speed of the optical fiber preform. In the optical fiber drawing method, when starting or stopping the operation, a pattern calculated in advance from the set values of the drawing speed, the outer diameter of the optical fiber, and the spinning tension is used.
At least the optical fiber base material feed rate and heating furnace temperature are changed, and at the same time, the outer diameter of the optical fiber is controlled by a control system that uses the drawing speed as the manipulated variable until it reaches a steady operating state or a stopped state. It is characterized by causing the transition.

Embodiments of the invention] Embodiments of the present invention will be described in detail below with reference to the drawings.

In the present invention, as shown in FIG.
It is fed into a heating furnace 3 maintained at 0°C, and the heated and softened portion at the tip is drawn as an optical fiber 4 at a speed faster than the base material feeding speed, and then, for example, an ultraviolet curable resin or a thermosetting resin is drawn. An optical fiber drawing method in which a coated resin or the like is applied by a coating device 5, the coated resin is cured by a curing furnace 6 to form a coated optical fiber 7, which is taken up by a take-up capstan and wound up by a winding machine 9. This applies to Here, reference numeral 10 indicates an outer diameter measuring device for measuring the outer diameter of the optical fiber 4.

In the above optical fiber drawing method, in the present invention,
For example, as shown in FIG.
, a heating furnace 3, a drawing device 11 including a take-up capstan 8, etc.
, the drawing speed setting value U□, the optical fiber base material outer diameter setting value Y
The optical fiber preform feed rate U3 and heating furnace temperature U2 calculated in step 2 are input to the calculation element based on ll and the drawing tension setting value Y■. At the same time, the drawing speed UI calculated in 1 is also input to the calculation element so that the outer diameter of the optical fiber is constant. At this time, the drawing speed U is the above-mentioned U2,
Based on U, a <feed-forward component may be added using the calculation element Kt.

In this way, in the present invention, the optical fiber preform feed rate Uff, heating furnace This is characterized in that the temperature Uz is changed and at the same time the outer diameter of the optical fiber is brought to a steady operating state or a stopped state while being controlled by a control system that uses the drawing speed U as the manipulated variable.

Here, the calculation element 1 may be determined using known control theory, but PID control or a control system in which a term (II element) proportional to the double integral of the deviation is added is particularly effective. The reason for this is that the optical fiber outer diameter often fluctuates in a ramp-like manner during startup.

In addition, the calculation elements 2 and Kt are determined by the shortest time control theory, etc., or the manipulated variables U l, U t, Us, controlled variables Y+ (actual value of optical fiber outer diameter) and YZ (H
An appropriate value is determined by simulation using the actual value of the tensile force in conjunction with the calculation element Kl.

In this embodiment, as the input values of Uz and Us, appropriate values were selected by simulation from a pattern of ramp-like changes from initial state values to steady state values.

Furthermore, by simulation, the heating furnace temperature U2
It has been found that the time required for startup and stopping can be further shortened by changing the optical fiber preform feed rate U to the set value earlier. In particular, the time required to change the heating furnace temperature U2 to the set value is T3, and the time required to change the optical fiber preform feed rate U to the set value is T3.
When set to 2, T+: 'l'', =2: 3~2:
It was also confirmed that setting it to 4 is optimal.

In addition, if the target drawing speed, that is, the steady operating state is relatively low speed, specifically, the drawing speed is 200 m/+i.
In the case of about n, the effect was confirmed even if only the optical fiber preform feed rate U was changed without changing the heating furnace temperature U2.

FIG. 3 shows a specific example of drawing an optical fiber using the method of the present invention. As shown in this article, the outer diameter of the tip fiber is almost constant and the drawing speed U is 40 m/min to 270 m/m.
It can be seen that it takes about 7 minutes to reach "in". still,
It took about 60 minutes to start up using the conventional method.

Although the above-mentioned embodiment mainly describes only the time of startup, it goes without saying that the present invention can also be applied to the case of stopping from a steady state, the case of interruption, or conversely, the case of starting up again after being interrupted. .

〔Effect of the invention〕

As described above, according to the present invention, it is possible to start up to a steady state and stop from a steady state during optical fiber drawing in a short time, thereby reducing product defects, that is, improving yield. can. Furthermore, since the control system is simple, equipment costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an optical fiber drawing device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is an actual measurement graph showing a specific example of the present invention. 1 - Optical fiber preform 2 - Optical fiber preform feeding device 3
~Heating furnace 4~Optical fiber 8~Take-back capsun 9
~ Winding machine 11 ~ Wire drawing device Patent applicant Furukawa Electric Co., Ltd. Figure 1 Figure 2

Claims (4)

[Claims] (1) Feeding the optical fiber preform into a heating furnace and heating it,
In an optical fiber drawing method in which an optical fiber is manufactured by drawing the heated portion at a speed faster than the feeding speed of the optical fiber preform, the drawing speed, the optical fiber outer diameter, , the optical fiber base material feed rate, with a pattern calculated in advance from the set value of the drawing tension,
The heating furnace is characterized by changing at least the optical fiber preform feed rate among the heating furnace temperatures, and at the same time transitioning the optical fiber outer diameter to a steady operating state or a stopped state while controlling it with a control system that uses the drawing speed as the manipulated variable. Optical fiber drawing method. (2) The optical fiber drawing method according to claim 1, characterized in that the heating furnace temperature is changed to a set value before the optical fiber preform feed rate is changed. (3) When the time required to change the heating furnace temperature to the set value is T_1, and the time required to change the optical fiber base material feed speed to the set value is T_2, T_
The optical fiber drawing method according to claim 1 or 2, characterized in that 1:T_2=2:3 to 2:4. (4) The optical fiber drawing method according to claim 1, wherein the pre-calculated pattern is a ramp function.