JPS6037062B2 - Optical fiber preform manufacturing method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides improvements in the method for manufacturing optical fiber preforms;
and a device for that purpose.

One of the manufacturing methods for optical fiber preforms is the vapor-phase deposition method.
ionMethod), but when manufacturing a glass fine particle laminate using this method, as shown in Figure 1, muffle (
A seed tube 2 is inserted into the reaction vessel 1 from above, and the frit gas supplied from the burner 3 undergoes a flame hydrolysis reaction inside the oxyhydrogen flame supplied from the same burner to form glass fine particles. The glass particles are laminated on the tip of the seed rod 2 to form a glass particle laminate (hereinafter referred to as a matrix) 4.

At this time, unreacted gas (SIC14
, Day 2, 02, etc.) and reaction product gases (KO, HCI, etc.)
Since these gases are generated, it is necessary to provide an exhaust pipe 5 to discharge these gases to the outside of the muffle 1.

The seed rod 2 is rotated by a motor 6 and is connected to another drive system (
(not shown), it is pulled upward in accordance with the production speed of the mother village 4.

The burner 3 usually uses concentric multiple tubes, and contains oxygen, hydrogen,
Raw material gas, seal gas, etc. are supplied to the burner boat 7 either individually or in a mixed manner. The gas discharged from the exhaust pipe 5 is guided to the writing removal equipment. In this figure, a cleaning tower 8 is shown as the abatement equipment. To add more information, 9 is a chuck for gripping the treadle, 10 is a rotating bearing, 11 is a coupling for transmitting the rotation of the motor 6 to the rotating shaft and the chuck 9 attached to its tip, and 12 is a bracket for the motor 6. be. 13 is a lid of the muffle 1, 14 is an inlet used for sucking air or other gas into the muffle 1, 15 is a support stand for the burner 3, 16 is a receiver tank,
17 is a pump for pumping liquid pressure, 18 is a shower, 19 is a partition plate for promoting reaction, a fan for suctioning two rivers, and 21 is a liquid feeding pipe.

The liquid commonly used is water or caustic soda, since the gas produced by the reaction is mainly HCI and chloride. Now, if the shape of the base material is expressed as a cylinder, the bulk density and composition of the glass particles constituting the base material must change in a constant manner in the radial direction. For example, fibers used for normal optical communications and image transmission have the highest refractive index at the center, and decrease as the distance from the center increases. As an example, the content of W02 is made highest at the center and least at the periphery.

The pattern of change in content in the radial direction, the refractive index ratio between the center and the periphery, etc., are determined depending on the intended use of the fiber. That is, keeping the pattern of radial refractive index variation as constant as possible in the axial direction of the cylinder is essential for improving fiber quality, and the present invention provides a method for this purpose.

The most important element to keep the pattern of refractive index change stable in all directions is to maintain stability of the oxyhydrogen flame. That is, the flame and the mother village 4
The purpose is to eliminate fluctuations in the relative position between the flow of glass particles inside the flame and the main village 4, and the law of suction force of the exhaust pipe 5 has the greatest and direct effect on this fluctuation. It has the power to attract flame. Gas as an extension of the flame is sucked into the exhaust pipe 5 through the gap between the base plate 4 and the exhaust pipe 5, so it is important to keep this gap, that is, the distance between the tip of the exhaust pipe and the outer periphery of the base metal, constant at the end of the technique. This leads to keeping the relative position between the flame and the base material 4 constant. That is, the present invention mixes and burns glass raw material gas and combustion gas using a burner consisting of a plurality of nozzles, stacks glass particles in the direction of the starting village, and then phosphorsizes them to produce an optical fiber preform. In the method, the optical fiber is characterized in that the distance between the tip of the exhaust pipe for discharging gas in the reaction vessel in which the above-mentioned mixed combustion and production and stacking of glass particles are carried out and the glass particle stack is always controlled to a constant value. The present invention relates to a method for manufacturing a preform.

The above object can be achieved by passing light between the tip of the exhaust pipe and the glass particle stack and moving the exhaust pipe so that the amount of light is constant. In an optical fiber preform production device consisting of a Matsufuru furnace with a seed comb and an exhaust pipe inserted into the furnace, a light beam is placed on a movable table to which the exhaust pipe is fixed, so that the light passes between the glass particle stack and the tip of the exhaust pipe. The oscillation and light receiving device is fixedly provided, and the light device and a motor that horizontally moves the moving table are linked to keep the distance between the tip of the exhaust pipe and the glass particle stack always constant The present invention relates to an optical fiber preform manufacturing device for controlling the optical fiber preform value. To further explain the device of the present invention with reference to FIG. 1, the exhaust pipe 5 is fixed to the movable table 22, and
is driven by the arrow 26 by the motor 24 via the screw shaft 23.
On the other hand, the phototube 26 is fixed to the movable table 22 by a supporting rod 27 in the same way as the exhaust pipe 5 (see the sectional view in FIG. 2).

For example, 26a is the light emitting side and 26b is the light receiving side, and the beam 28 is irradiated from the light emitting side to the light receiving side through a window 29 provided in the muffle 1. Therefore, the distance between the tip of the exhaust pipe 5 and the base material 4 is equivalent to the distance between the tip of the exhaust pipe 5 and the beam 28, and the amount of light received by the light-receiving phototube 26b is converted into, for example, a voltage, and this voltage is kept constant. The purpose of the present invention can be achieved by moving the movable table 22 using the motor 24 so as to maintain the exhaust pipe 5 at a constant temperature. As the set voltage, it is sufficient to use, for example, a voltage corresponding to the amount of light received by the light-receiving phototube 26b when 1/2 of the beam 28 is blocked by the base material 4. It goes without saying that the object of the present invention can also be achieved by using, for example, a laser oscillation tube and a light receiving diode instead of the phototubes 26a and 26b.

Example A quadruple tube burner (concentric 4-layer burner) with the cross-sectional structure shown in Fig. 3 was used, and from the first layer B, SIC141.5 /
and QC140.2 pm/min by bubbling method, hydrogen 4 so/min from the second layer string, argon 2 so/min from the third layer B3, and oxygen 7 so/min from the fourth layer string. 250 cc/min of argon was used as the carrier gas.

The muffle is 30mm tall x 80mm wide, and the exhaust pipe has an inner diameter of 40mm.
Side ◇, outer diameter 45 side, displacement was 300〆/min.

Under the above conditions, the outer diameter of mosquitoes is 5 mm? , final production length 400'
The base material is deposited at a manufacturing rate of 0.
．． 4 times per minute. The above conditions were the same, Example 1 adopted the control according to the present invention, and Comparative Example 1 did not employ the control, and after making the fiber exhibit the effect of the present invention, it was evaluated by the banding characteristics.

Table 1 Table 1 is nothing but a comparison of the stability of the manufacturing process in one base material, but the present invention is also very useful for suppressing variations in quality when multiple base materials are manufactured under the same conditions. It is valid.

In the following example, five base materials were manufactured and compared in terms of variation in band characteristics. Table 2

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view for explaining the method of the present invention and showing an example of the apparatus of the present invention, and FIG. 2 is a cross-sectional view showing details of the characteristic parts of the apparatus of the present invention shown in FIG. FIG. 3 is a cross-sectional view of the burner used in the present invention. Eagle 2 Figure 3 Figure 1

Claims (1)

[Claims] 1 A burner consisting of a plurality of nozzles is used to mix and burn glass raw material gas and combustion gas to stack glass particles in the axial direction of a starting base material, which is then sintered to form an optical fiber preform. A method for producing a glass particle stack, characterized in that the distance between the glass particle stack and the tip of an exhaust pipe for discharging gas in the reaction vessel in which the above-mentioned mixed combustion and generation and stacking of glass particles are carried out is always controlled to a constant value. A method for manufacturing an optical fiber preform. 2. In an optical fiber preform manufacturing device consisting of a Matsufuru furnace having a burner, a seed rod inserted so as to be able to move up and down, and an exhaust pipe, light is transmitted between the glass particle stack and the tip of the exhaust pipe on a movable table to which the exhaust pipe is fixed. A tip of an exhaust pipe and a glass particle laminate, characterized in that a light oscillation and light receiving device is fixedly provided so that the light passes through, and the light device and a motor that horizontally moves a moving table are linked. Optical fiber preform manufacturing equipment to always control the distance to a constant value.