JPS61117130A - Preparation of parent material for optical fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to a method for manufacturing an optical fiber preform by a vapor deposition (VAD) method.

The method of manufacturing an optical fiber preform by the VAD method is widely known for its excellent productivity. In this manufacturing method, 5iCJ! which becomes the base glass! Raw material gases such as GeCf4 and POCJI3 for controlling the refractive index are inserted together with oxyhydrogen gas from a fixed quartz tube burner, and reacted with heat from an oxyhydrogen flame to form glass fine powder. to be generated. Then, the generated glass fine powder is sequentially deposited on the tip of the target, and the target itself is rotated and pulled up one after another to keep the distance between the burner and the glass fine powder deposition surface at the tip of the target constant. Controlled porous matrix (soot rod)
is manufactured. The refractive index distribution in the radial or longitudinal direction of the final glass is controlled by subtle differences in the deposition conditions at the leading edge of the porous matrix. For this reason, not only the distance between the burner and the leading edge of the target but also the deposition conditions are
Transmission characteristics of optical fibers made from optical fiber base materials,
This is especially important because it has a large effect on the transmission band characteristics of multimode and graded optical fibers.

Conventionally, various methods have been proposed for adjusting the deposition conditions at the leading edge to a constant level, and, for example, with regard to controlling the reaction temperature at the leading edge, there is currently a technology that allows adjustment within the range of ±1°C to 2°C. has been almost established and reproducibility is improving.

However, as the length of the porous base material becomes longer, minute vibrations of the target pulling mechanism or rotation mechanism are transmitted to the porous base material during manufacture, which causes a co-photography phenomenon of the porous base material, which in turn affects the deposition conditions. This changes the positional relationship between the burner and the most important tip of the porous base material, causing a problem in which various adjustment effects become meaningless.

FIG. 2 is a longitudinal cross-sectional view of an apparatus for implementing a method for manufacturing an optical fiber preform by the conventional VAD method. In the figure, 1 is the target, 2 is the chamber, 3 is the porous base material (soot) made of deposited glass fine powder, 4 is the tip of the porous base material at the highest temperature point of the porous base material 3, and 5 is the reaction Temperature side/window window,
6 is an ultraviolet temperature measuring device, and 7 is an oxyhydrogen force flow control device. 8 is a quartz tube burner of an oxyhydrogen burner, and 9 is a chamber stand.

10 is an exhaust port. The quartz tube burner 8 produces 5tCJ of raw material gas from its central burner! a, Gecla, P.
OCj! It has a composite burner structure in which oxygen and hydrogen, argon, nitrogen, etc. are introduced from the outer tube burner.

In the case of manufacturing an optical fiber base material, the raw material gas and oxygen, hydrogen, and other gases are fed into the quartz tube burner 8, and the raw material gas is reacted in an oxyhydrogen flame to generate fine glass powder. The target 1 is sequentially deposited on the tip of the target 1 which is being rotated, and the target 1 is gradually pulled up. In this way, the porous base material 3 is generally formed.

Also, oxygen and hydrogen used for combustion, and gases such as argon and nitrogen used for reaction control.

Alternatively, a part of the generated glass fine powder etc. can be
Air is discharged from the air port 10, and the pressure inside the chamber 2 is always maintained at a constant pressure. At the same time, an infrared moisture measuring device 6 monitors the temperature of the tip 4 of the porous base material, which is most important for the deposition conditions, and feeds this back to the oxyhydrogen gas flow control device 7 for combustion to control the oxyhydrogen gas flow rate. We are trying to stabilize the deposition conditions by adjusting the

However, as mentioned above, as the porous base material becomes longer,
As the target 1 holding the porous base material rotates and pulls up, vibrations are also transmitted to the porous base material 3, making it impossible to accurately measure the reaction temperature or to control the reaction temperature. However, there were problems such as variations in transmission characteristics in the four longitudinal directions.

The present invention was made in view of the above-mentioned circumstances, and aims to provide a method for manufacturing an optical fiber preform that can stabilize transmission characteristics in the longitudinal direction and improve reproducibility. .

[Summary of the Invention] The method for producing an optical fiber preform of the present invention involves reacting raw material gases such as silicon chloride and germanium chloride in an oxyhydrogen flame generated by feeding oxygen and hydrogen into an oxyhydrogen burner. When manufacturing an optical fiber preform by depositing glass fine powder on the tip of a target to form a porous preform and heating and making the porous preform transparent, during the deposition and connection of the porous preform, The target supporting the deposition surface of the upper and second porous base materials is fixed to a vibration isolating table, and the oxyhydrogen burner disposed below the target is rotated and moved downward one by one to deposit the upper and lower porous base materials. This is a method of depositing a porous matrix.

[Example] Hereinafter, using an example of the method for manufacturing an optical fiber preform of the present invention, the same parts as those in the H position for implementing the conventional method for manufacturing an optical fiber preform will be denoted by the same reference numerals, and the structure of the same part will be explained. The explanation will be omitted with reference to FIG. The first is a longitudinal sectional view of the implementation device. The difference between this embodiment and the conventional manufacturing method is that in the conventional method, the target 1 is pulled upward while being rotated and the quartz tube burner 8 is fixed, whereas in this embodiment, the target 1 is Fixed and held in a vibration-resistant structure holder,
Instead, the quartz tube burner 8 is rotated and lowered. In FIG. 1, 11 is a rotating burner holder.

Reference numeral 12 denotes a rotary gas introduction inlet, and reaction gas and the like are introduced into the quartz tube burner 8 supported by the rotary burner holder 11 via the rotary gas inlet 12. The rotary burner holder 11 is rotatably driven by a drive device (not shown), and the chamber stand 9. The infrared temperature measuring device 6 and the like are gradually lowered by a connected lowering device (not shown).

In the case of manufacturing the porous base material 3, the target 1 is stopped and glass fine powder is sequentially deposited on the tip of the target 1, and the jumper 2° quartz tube burner 8. Infrared temperature measuring device6. The oxyhydrogen gas flow measuring device 7 and the like are pulled down in the direction of the arrow to maintain a constant distance between the quartz tube burner 8 and the surface of the porous base material tip 4 on which the fine glass powder is deposited. Further, the quartz tube burner 8 is simultaneously driven to rotate via a rotary burner holder 11. Therefore, even if the porous base material 3 becomes longer, since the target 1 is stopped, stable reaction can continue, and the porous base material 3 becomes longer.
It became clear that the shaking phenomenon of material 1 was extremely reduced and the stabilization of the transmission characteristics in the longitudinal direction was improved. In addition, reproducibility can also be improved.

In this way, in the optical fiber preform manufacturing method of this embodiment, the target on which the porous preform is deposited is stopped,
Since the quartz tube burner is rotated and pulled down, it is possible to reduce the vibration phenomenon of the porous base material during the deposition of fine glass powder, thereby improving the stability and reproducibility of the transmission characteristics in the longitudinal direction. .

[Advantageous Effects of the Invention 1] As described above, the method for manufacturing an optical fiber preform of the present invention has the effect of stabilizing the transmission characteristics in the longitudinal direction and improving reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an apparatus for carrying out the method for manufacturing an optical fiber preform of the present invention, and FIG. 2 is a longitudinal cross-sectional view of an apparatus for carrying out the conventional method for producing an optical fiber preform. 1...Target, 2...Chamber, 3...Porous base material. 8...Quartz tube burner, 11...Rotating burner holder. 12...Rotating gas inlet section. 1st item

Claims (1)

[Claims] (1) Oxygen and hydrogen are sent to an oxyhydrogen burner to create a generated oxyhydrogen flame, and raw material gases such as silicon tetrachloride and germanium tetrachloride are reacted to produce fine glass powder, which is deposited on the tip of the target to create a porous hole. In the method for manufacturing an optical fiber preform by forming a porous preform and heating the porous preform to make it transparent, the above-mentioned member supporting the deposition surface of the porous preform while the deposition of the porous preform continues. An optical fiber motherboard characterized in that a target is fixed to a vibration isolating table, and the oxyhydrogen burner disposed below the target is sequentially moved downward while rotating to deposit the porous base material on the target. Method of manufacturing wood.