JPS60112637A - Method and apparatus for manufacture optical fiber - Google Patents

Abstract

PURPOSE:To improve the transmission characteristics and mechanical strength by heating a glass base material from the outside in a heating furnace while heating it from the inside by introducing laser light. CONSTITUTION:A glass base material 1 for an optical fiber is put in a resistance heating furnace 2 made of high purity carbon, and the material 1 is heated from the outside. At the same time, HF laser light 3 is introduced into the material 1 from the top to heat the material 1 from the inside. The wavelength of the laser light 3 is in a region where the absorption coefft. of the material 1 becomes 0.01-1cm<-1>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for drawing a rod-shaped optical fiber glass preform into a fibrous optical fiber.

The conventional optical fiber drawing method uses a resistance heating furnace or high-frequency induction heating furnace to heat and heat a rod-shaped glass base material from the outside.
The glass base material is softened and drawn into optical fibers, and if you try to heat it above the softening temperature at which it is possible to draw the inside of the glass base material, the temperature on the surface of the glass base material will become too high, and the glass composition on the surface of the glass base material will become too high. Some of the elements may evaporate and the glass composition may change, or the glass composition distribution may change due to the diffusion of some of the elements. The evaporated elements cause contamination inside the drawing furnace, which has the disadvantage of reducing the strength characteristics of the optical fiber.

The present invention is a method for heating a glass base material for optical fiber during the optical fiber drawing process, in which the glass base material is heated from the outside in a heating furnace, and the glass base material is heated from the inside by passing a laser beam into the inside of the glass base material. It is characterized by heating the glass base material by dual means from inside and outside, and its purpose is to soften the glass base material so that wire can be drawn to the inside of the glass base material without raising the temperature of the surface of the glass base material more than necessary. The object of the present invention is to provide a method and apparatus for drawing an optical fiber in which evaporation and diffusion of glass constituent elements on the surface of a glass base material do not occur due to heating above the temperature.

FIG. 1 is a diagram showing an embodiment of the optical fiber drawing method of the present invention, in which ■ is a quartz-based glass base material for optical fibers, 2 is a high-purity carbon resistance heating furnace, 8 is an HF laser, and 4 is a fiber drawing method. −
It is a shaped optical fiber.

To carry out this, the glass preform 1 for optical fiber is inserted into a resistance heating furnace 2 made of high-purity carbon, and the glass preform 1 is heated from the outside.
The light from the HF laser 8 is incident from the upper end of the glass base material 1 to heat the glass base material 1 from the inside as well.

FIG. 2 shows an example of measuring the relationship between the distance from the top of the glass base material and the temperature rise when HF laser light is irradiated from the top of the glass base material. From this, it can be seen that the temperature inside the glass base material can be raised by about 50'C using the HF laser. In this measurement example, the wavelength of the HF laser is 2.
7-3.26μm1 output is 1L, 75kW, beam diameter is 10mm.

When we conducted a drawing experiment on a silica glass optical fiber using the method described above, we found that when the glass base material was heated only with a high-purity carbon resistance heating furnace, the surface temperature of the glass base material was 18.
It was not possible to draw a line unless the temperature was above 00℃, but with HF
When a laser is used together, the surface temperature of the glass base material is 10
Drawing was possible even at 00°C.

Furthermore, when the glass base material was drawn at a surface temperature of 1800'Q, evaporated matter from the surface of the glass base material was observed in the drawing furnace and on the remaining glass base material after drawing, and the optical fiber The glass composition distribution on the surface also changed from that of the glass base material, and the higher the surface temperature of the glass base material, the more remarkable this tendency was. On the other hand, when the glass base material was drawn at a surface temperature of 1700° C., there was almost no contamination in the drawing furnace, and no change in the glass composition distribution on the surface of the optical fiber was observed.

In the above example, a resistance heating furnace made of high purity carbon was used as a means for heating the glass base material from the outside, and an HF laser was used as a means for heating the glass base material from the inside, but the present invention is not limited to this. isn't it. The former may be any resistance heating furnace made of molybdenum, tungsten, or Kryptor, a high-frequency induction heating furnace, a carbon dioxide laser, an oxyhydrogen flame, a plasma flame, etc., as long as it can heat the glass base material to a temperature higher than its softening temperature. The latter may be a laser having an oscillation wavelength in a region where the absorption coefficient of the glass base material is o, ot-1, , 71, and an output of about 1 kW or more.

In the case of a quartz glass base material, a laser having an oscillation wavelength of around 3 μm is desirable.

As explained above, according to the present invention, it is possible to heat the glass base material to a temperature higher than the softening temperature at which wire can be drawn to the inside of the glass base material without raising the temperature of the surface of the glass base material more than necessary. By causing evaporation and diffusion of the glass constituent elements on the surface of 'jc<, it is possible to draw an optical fiber, which has the advantage that an optical fiber with excellent transmission characteristics and mechanical strength characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram of an embodiment of the optical fiber drawing method of the present invention;
FIG. 2 is a side view of measuring the temperature rise of the glass base material when HF laser is irradiated from the upper end of the quartz glass base material. ■... Glass base material for optical fiber, 2... High purity carbon resistance heating furnace, 3... HF laser, 4... Optical fiber.

Claims (1)

[Claims] L A rod-shaped glass base material for optical fiber is heated and softened,
In the process of drawing a fibrous optical fiber, the method of heating the glass preform for optical fiber is to heat the glass preform from the outside in a heating furnace, and heat it from the inside by passing a laser beam into the inside of the glass preform. A method for manufacturing an optical fiber characterized by heating the glass base material by dual means from inside and outside 0 2 The wavelength of the laser beam is such that the absorption coefficient of the glass base material is 0 and O1
A method for producing an optical fiber according to claim 1, characterized in that the region is 1 cm-''. A holding device that holds a glass base material for optical fiber in the center, a drawing device that draws softened glass from the heated side end of the glass base material for optical fiber, 1. An optical fiber manufacturing apparatus comprising a light input device and a light source that input laser light from an end opposite to the side to be heated.