JPH05139771A - Method for controlling optical fiber drawing furnace - Google Patents

Abstract

PURPOSE:To dispense with controlling the electric power of a heating furnace according to a change in drawing speed and a thermometer for detecting a drawing temp. and to prevent the excessively large or small throwing of the electric power by controlling the electric power of the heating furnace in such a manner as to maintain the specified ratio between the drawing tension and drawing speed of an optical fiber. CONSTITUTION:An optical fiber base material 10 is continuously heated and melted by the heating furnace 12 and is drawn as an optical fiber 16. The outputs of a tension gage 30 and a speedometer 34 are inputted to a controller 36 where the ratio T/v between the drawing tension T and the drawing speed v is computed. The electric power of the heating furnace 12 is then so feedback controlled as to maintain the specified ratio, i.e., the specified viscosity eta of the molten part of the base material 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an optical fiber drawing furnace.

[0002]

2. Description of the Related Art In FIG. 2, an optical fiber preform 10 is continuously heated and melted in a heating furnace 12 and drawn as an optical fiber 16. Reference numeral 14 is a temperature control device for the heating furnace, and 15 is a thermometer for detecting the drawing temperature. 18 is a cooling cylinder, 20 is a coating device for the primary coating material, 22 is a cross-linking cylinder, 24 is a turn pulley, 26 is a take-up machine, and 28 is a take-up machine.

A tension meter 30 monitors the drawing tension of the optical fiber 16, and the heating furnace 12 keeps the tension constant.
Adjust the power input to the wire and adjust the drawing temperature. When the drawing tension is high, the electric power of the heating furnace 12 is increased and the melting temperature of the optical fiber preform 10 is increased to decrease the viscosity,
The drawing tension can be lowered. If the drawing tension is low, the reverse is done. Since the drawing tension has a great influence on the characteristics of the optical fiber, it should be kept as constant as possible.

Further, the optical fiber 1
The outer diameter of No. 6 is monitored, and the result is fed back to the take-up machine 26 to control the drawing speed to maintain a predetermined outer diameter. 34 is a speedometer.

[0005]

For example, the outer diameter of the optical fiber 16 may change due to a change in the shape of the optical fiber preform 10. At that time, the drawing speed is changed in order to correct the outer diameter of the optical fiber 16. Then, even when the temperature of the optical fiber preform 10 is appropriate, the drawing tension changes with the change in the drawing speed. If feedback control is performed directly on the drawing tension to stabilize the drawing tension, when the drawing tension changes, the control system that changes the electric power of the heating furnace 12 works as described above, although it is not necessary originally. ..

Further, the heating furnace 1 based on the above drawing tension
Since the power control system of No. 2 and the control system of the outer diameter of the optical fiber 16 are different systems, fluctuations in the drawing tension (actually the heating furnace 1
2) and the fluctuation of the drawing speed (for controlling the outer diameter of the optical fiber 16) may occur at the same time. In such a case, the power input to the heating furnace 12 may become excessively large or excessively small, and when feedback is actually applied, there is a tendency that the electric power is diverged even if the gain is reduced.

[0007]

The heating furnace 1 is provided so that the ratio of the drawing tension and the drawing speed of the optical fiber 16 becomes constant.
Adjust the power of 2.

When the drawing tension is T and the drawing speed is v, T / v is controlled to be constant.
T / v has a certain relationship with the viscosity η of the fused portion of the optical fiber preform 10 as described below.

[Equation 1]

Adjusting the electric power of the heating furnace 12 so that T / v becomes constant also means that the viscosity η of the melted portion of the optical fiber preform 10 becomes constant. is there.

Specifically, as shown in FIG. 1, the outputs of the tensiometer 30 and the speedometer 34 are input to the control device 36, where T /
v or the viscosity η is calculated, and the electric power of the heating furnace 12 is feedback-controlled so that it becomes constant.

In addition to glass, the drawing tension has a share of coating. The tension of the coating share also changes in proportion to the drawing speed. However, changes in tension due to changes in coating viscosity and thickness are generally negligible,
It does not hinder the control by this method.

[0012]

[Advantageous effects of the invention]

(1) For example, as the drawing speed of the optical fiber 16 increases, the drawing tension also increases, so the value of T / v does not change significantly. Therefore, as described above, it is not necessary to control the electric power of the heating furnace 12 which is originally unnecessary because the temperature of the optical fiber preform is appropriate as the drawing speed changes. (2) It is possible to prevent excessive or excessive power input. (3) The thermometer 15 becomes unnecessary.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 10 Optical Fiber Base Material 12 Heating Furnace 14 Temperature Control Device for Heating Furnace 15 Thermometer 16 Optical Fiber 18 Cooling Tube 20 Primary Coating Material Coating Device 22 Crosslinker 24 Turn Pulley 26 Pulling Machine 28 Winding Machine 30 Tensile Meter 32 Outer Diameter Measuring Instrument 34 Speedometer 36 Control device

Claims (1)

[Claims] 1. A heating furnace in which an optical fiber base material is continuously heated and melted in a heating furnace to draw a fiber as an optical fiber so that a ratio between a drawing tension and a drawing speed of the optical fiber becomes constant. Control method of optical fiber drawing furnace, which adjusts the electric power of.