JPS60155537A - Manufacture of optical fiber - Google Patents

Abstract

PURPOSE:To manufacture an optical fiber having low transmission loss, by depositing glass layers for the core and the clad to the inner surface of a quartz glass tube, and collapsing and drawing the tube. CONSTITUTION:The quartz glass tube 1 is clamped rotatably with the glass lathe 2, and CF4+O2 gas is introduced from the gas supplying system 3 into the tube 1 while heating the tube 1 externally with the oxyhydrogen burner 4. CF4 is made to react by this process with SiO2 of the inner wall of the tube 1 to form SiF4, which is evaporated by the intense heat of the oxyhydrogen burner (etching action) and exhausted to the outer atmosphere through the exhaust duct 5. Consequently, the impurities admixed in the etching process can be exhausted completely even if the impurities in the outer atmosphere are intruded into the tube 1 during the setting step. Therefore, the inner wall of the tube can be cleaned sufficiently and easily, and an optical fiber having low transmission loss can be manufactured easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for manufacturing an optical 7-eyeper that easily manufactures a low-loss original fiber.

(Prior art) The conventional method for manufacturing optical fibers is to set a cleaned quartz glass tube in a glass lathe that can be rotated, introduce a reaction raw material gas into the set quartz glass tube, and heat and sweep it from the outside. Then, there is a method of depositing a glass film that will become the core and cladding of the optical fiber on the inner wall of the quartz glass tube, solidifying the quartz glass tube at the edge, and then drawing it to obtain an optical fiber. . Generally, in order to reduce the loss of an optical fiber, it is important to prevent impurities from entering the quartz glass tube from outside air.

However, with this manufacturing method, there is a problem that impurities from outside air tend to get mixed in during the cleaning process inside the quartz glass tube and the process of setting the quartz glass tube on a glass lathe. When such impurities are deposited, the impurities remain between the inner wall of the quartz glass tube and the glass film, and there is a problem in that the impurities adversely affect the transmission loss of the optical fiber. .

Conventionally, cleaning inside the quartz glass tube in this manufacturing method was
The quartz glass tube was filled with an etching solution such as hydrofluoric acid, and the inner wall of the quartz glass tube was etched, followed by washing and drying. However, such a cleaning process is equivalent to etching.

Since rinsing and drying are independent steps, impurities from the outside air tend to get mixed in when switching between these steps, making it difficult to thoroughly clean the inner wall of the quartz glass tube. Furthermore, it was extremely difficult to set the cleaned quartz glass tube inner wall in a glass lathe without exposing it to impurities in the outside air. In addition, in order to prevent impurities from the outside air from entering during switching and setting, a cleaning device and a glass film that will be used as the core of the optical fiber, which can easily manufacture optical fibers with glass torsion loss, are deposited. a second step of solidifying the quartz glass tube on which the glass film is deposited so that its cross section becomes dense; and drawing the solidified optical fiber base material to form an optical fiber. In the method for manufacturing an optical fiber, the method includes a third step in which, before the first step, heptafide gas is introduced into the rotatably held quartz glass tube and the quartz glass tube is heated. Particularly, it is characterized by the addition of a step of etching the inner wall of the quartz glass tube.

(Example) Next, the present invention will be explained in detail using the drawings.

The figure is a configuration diagram of an optical fiber manufacturing apparatus for explaining the present invention in detail. In the figure, first, a quartz glass tube 1 is set on a glass lathe 2 so as to be rotated and held. Next, add CF into the quartz glass tube l.

102 gas is introduced from the supply gas system 3, and the quartz glass tube l is heated by the oxyhydrogen burner 4. By doing this, j7, CF, is 8i0. of the inner wall of the quartz glass tube. This 8iF reacts with to produce SiF4.

vaporizes when heated at high temperatures (etching effect). The SiF4 volatilized here is exhausted to the outside through the exhaust duct 5.

Since the inner wall of the quartz glass tube 1 is etched after the quartz glass tube 1 is set in the glass lathe 2 in this way, even if impurities from the outside air are mixed in during setting as in the conventional method, the inner wall of the quartz glass tube 1 can be etched. Since the etching process is performed, the mixed impurities are sufficiently exhausted. In addition, since the inner wall of the quartz glass tube is etched using fluoride gas,
There is no need for the conventional washing and drying processes, and therefore there is no need for a switching process that can easily introduce impurities from outside air. In this way, the quartz glass tube can be etched after being set on the glass lathe, and a cleaning switching step is not required, so that the inner wall of the quartz glass tube can be thoroughly cleaned. Further, the glass lathe can be a conventional glass lathe, and the cleaning device can be simply constructed by simply equipping a conventional optical manufacturing device with a fluoride gas supply system.

For example, CF410x = 1/20 CF number + O
When etching was carried out by flowing t-gas 101005e into the quartz glass tube, the inner wall of the quartz glass tube was etched by about 10 μm. If the thickness is etched to this extent, impurities on the inner wall of the quartz glass tube can be sufficiently removed.

Next, in this cleaned quartz glass tube 1, sio, +
By introducing the reaction raw material gas of o2 from the supply gas system 3 and heating it with the oxyhydrogen burner 4, the quartz glass tube
The inner wall of the optical fiber is SiO! Then, a reaction raw material gas of 5i (J4+GeCl4 + 02) is introduced from the supply gas system 3, and 8 io, + Gem, which will become the core of the optical fiber, is deposited in the same manner.

Next, the reaction raw material gas from the supply gas system 3 is interrupted, the oxyhydrogen burner 4 is used, and the quartz glass tube 1 is further heated to a high temperature to solidify the quartz glass tube 1 into a solid shape to form an optical fiber. Get wood. Then, one end of the optical fiber base material is melted and drawn to form an optical fiber.

(Effects of the Invention) As explained above, according to the manufacturing method of the present invention, the inner wall of the quartz glass tube can be sufficiently cleaned, so that a low-loss optical fiber without impurities can be obtained. In addition, the optical fiber manufacturing apparatus can be easily constructed.

In this embodiment, CF4+0 gas was used as the fluoride gas, but the present invention is not limited to this, and any fluoride gas may be used. Further, although an oxyhydrogen burner was used as the heat source, it is clear that the heat source is not limited to this.

Furthermore, 810 is used as the core and cladding glass film.
I explained the case using @+GeO@ and 5in2, but
P, 0. , B, 0. , can be used even if it includes F.

[Brief explanation of the drawing]

The figure is a configuration diagram of an optical fiber manufacturing apparatus for explaining an embodiment of the present invention. In the figure, l: quartz glass tube, 2: glass lathe, 3: supply gas system, 4: oxyhydrogen burner, 5: ...This is an exhaust duct.

Claims (1)

[Claims] A first step is to deposit a glass film that will become the core and cladding of an optical fiber on the inner wall of the quartz glass tube, and a second step is to solidify the quartz glass tube on which the glass film is deposited so that its cross section forms a window. and a third step of drawing the solidified optical fiber base material to form an optical core. 1. A method for manufacturing an optical fiber, comprising the additional step of etching the inner wall of the quartz glass tube by introducing fluoride gas into the quartz glass tube and heating the quartz glass tube.