JPS61236627A - Accumulating method for fine glass grain - Google Patents

Abstract

PURPOSE:To secure the stability of an air stream in a period of the accumulation of the fine glass grains and to form a porous glass layer having the superior quality by rotating and transferring slowly a burner along a locus circle in a period of the formation of the porous glass layer. CONSTITUTION:A rodlike base material 21 is interposed between a burner 11 and an exhaust port 18 and rotated in the direction shown in an arrow R and transferred in the V direction. An injection end part of the burner 11 is directed toward a point P of the exhaust port 8 which is deviated from a rotating axial core O of the base material 21. The fine glass grains are injected on an outside periphery of the base material 21 from the burner 11 to form a porous glass layer 22. When a laser beam L circumscribed to the peripheral surface of the base material 21 is interrupted by the accumulated formation of the porous glass layer 22, the burner 11 and an irradiator 19 provided thereby are drawn in the direction shown in an arrow S with a guide rail 13 as the guidance. The angular laser beam is made incident on a detector 20 and the porous glass layer 22 is accumulated up to a prescribed thickness. Thereby the air stream of the burner is smoothly flowed to the exhaust port 18 along the peripheral surface of the porous glass layer 22.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application 1. The present invention relates to a method for depositing glass fine particles for producing various glass base materials for communication and optical applications.

[Conventional technology 1] Generally, when glass base materials for communication and optical applications are manufactured by the OVD method, a burner with a multi-tube structure is fed with vapor-phase glass raw materials, vapor-phase dope materials, fuel gas, auxiliary combustion gas, and buffer gas. A gas or the like is supplied, and glass particles generated by a flame hydrolysis reaction of each of these gases are injected and deposited on the outer periphery of a rotating rod-shaped base material to form a porous glass layer on the outer periphery of the rod-shaped base material.

Thereafter, the porous glass layer is placed in a high-temperature furnace to turn it into transparent glass.

Usually, the formation of the above-mentioned porous glass layer is carried out in a reaction vessel maintained in a clean atmosphere, and at this time, an exhaust port is provided at a position facing the burner with the rod-shaped base material in between.
Exhaust gas during the formation of the glass layer is discharged from the exhaust port.

FIG. 3 shows the state of formation of a conventional porous glass layer.

In the same figure, a porous glass layer 3 is formed on the outer circumferential surface of a rod-shaped base material 1 rotating in the direction of arrow R due to the accumulation of glass particles injected from a burner 2, and the exhaust gas at this time is However, when the outer diameter of the porous glass layer 3 increases due to such glass accumulation, the air flow containing glass particles from the burner 2 is repelled by the porous glass layer 3 with the enlarged diameter, and the burner 2 and the porous glass layer 3 are discharged from the burner 2. An unfavorable vortex is generated between the glass layer 3 and the glass layer 3, and smooth flow to the exhaust port 4 is inhibited.

"Problems to be Solved by the Invention" As described above, in the conventional glass particle deposition means, the glass particles from the eight-cell 2 are repelled by the porous glass layer 3, and smooth flow to the exhaust port 4 is prevented. is inhibited.

As a result, some of the glass particles are scattered inside the reaction vessel, and the scattered glass particles are not discharged outside the vessel, but instead adhere softly to areas of the porous glass layer that are not exposed to the burner flame, causing cracks and foaming. to make.

Or, the scattered glass particles may be deposited on the inner wall of the reaction vessel.
After this adheres to the surface and grows large, it falls onto the porous glass layer, causing even larger bubbles.

Furthermore, in the conventional example described above, since the gas does not flow in a fixed direction, the burner flame undergoes stable oscillations, which increases the variation in the outer diameter of the porous glass layer.

These problems occur in products that use the above-mentioned glass material as a base material, such as optical fibers, as variations in outer diameter, poor strength, increased transmission loss, and poor dimensional accuracy.

In view of the above-mentioned problems, the present invention aims to provide a method for depositing glass particles, which ensures stability of airflow during deposition of glass particles and allows formation of a high-quality porous glass layer.

1. Means for Solving Problems j The present invention is characterized in that the injection end of the burner faces one side of the outer periphery of the rod-shaped base material, and the exhaust port of the exhaust system faces the other side of the outer periphery of the rod-shaped base material. The glass particles ejected from the burner are injected and deposited on the outer periphery of the rotating rod-shaped base material to form a porous glass layer around the outer periphery of the rod-shaped base material, and the waste gas at this time is discharged from the exhaust port. In the method for depositing glass particles, the injection end of the burner is directed toward a point on the exhaust port side that is offset from the rotation axis of the rod-shaped substrate, and a porous glass layer is formed on the outer periphery of the rod-shaped substrate via the burner. As the outer diameter of the porous glass layer increases, the burner is gradually rotated along a locus circle centered on the one point.

1 Effect J The method of the present invention is fundamentally different from existing OVD methods in that glass fine particles injected from a burner are injected and deposited on the outer periphery of a rotating rod-shaped substrate to form a porous glass layer on the outer periphery. However, at this time, the injection end of the burner is directed toward a point on the exhaust port side that is offset from the rotation axis of the rod-shaped base material.

In this way, when the direction of the injection end of the eight is shifted from the rotation axis of the rod-shaped base material, the direct opposition between the two occurs when the injection end is directed toward the rotation axis of the rod-shaped base material. is avoided.

Therefore, the impact when the burner air flow containing glass particles collides with the outer circumferential surface of the rod-shaped base material is alleviated, the generation of harmful vortices is suppressed, and the gas flow toward the exhaust port is smoothed, and the glass particles are hardly scattered around. It is deposited on the outer peripheral surface of the rod-shaped base material without any damage.

Due to the deposition of such glass particles, a porous glass layer is formed on the outer peripheral surface of the rod-shaped base material, and as the deposition progresses, the outer diameter of the porous glass layer increases.

As the outer diameter of the porous glass layer increases, the impact area of the burner air flow against its circumferential surface increases, causing harmful eddy currents to occur and glass particles to scatter, but after the glass particles begin to accumulate, the porous glass layer As the outer diameter of the layer increases, the burner is gradually rotated along a locus circle centered on a predetermined point.

In such a case, the collision area of the burner air flow against the circumferential surface of the porous glass layer does not change much, and the above-described favorable glass particle deposition state can be maintained as it is.

In this way, the stability of the airflow during the deposition of glass fine particles, the suppression of the scattering of glass fine particles, etc. can be achieved, and a high-quality porous glass layer without bubbles or fluctuations in outer diameter can be formed.

Embodiment J Specific embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, 11 is a burner having a multi-tube structure.

An engaging member 12 is attached to the burner 11, and this engaging member 12 engages with a guide rail 13 bent into a suitable circular arc shape.

Reference numeral 14 denotes a traction device for pulling the burner 11 along the guide rail 13, and the traction device 14 includes a wire 15, a wire winder 16, and a controller 1 for the wire winder 18.
7, and the end of the wire 15 is connected to the eighth 11.

18 is an exhaust system equipped with pipes, etc., and this exhaust system 18
The exhaust port is located opposite the burner.

1) If a point on the exhaust port side of the exhaust system 18 is P, the guide rail 13 described above has the same radius of curvature as the trajectory circle centered on that point P.

18 is a laser beam irradiator, 20 is a laser beam detector, the irradiator 19 is attached to the burner 11, and the detector 20 is attached to the exhaust port end side of the exhaust system 18, so that they can transmit and receive light from each other. Compatible.

In the figure, 21 is a rod-shaped base material made of quartz rod, alumina rod, etc.;
2 is a porous glass layer deposited on the outer periphery of the rod-shaped base material.

When forming the porous glass layer 22 on the outer periphery of the rod-shaped base material 21 in FIGS. 1 and 2, the rod-shaped base material 21 is connected to the burner 11 at the starting position A in FIG.
8), and is rotated in the direction of arrow R and moved forward in the direction of arrow (■).

When the burner 1 is at the start position A, the injection end of the burner +1 is directed to the point P on the exhaust port side that is offset from the rotation axis 0 of the rod-shaped base material 21, and the irradiator lθ and the detector 2
The laser beam extending over 0 is close to the circumferential surface of the rod-shaped base material 21.

On the other hand, the burner 1 is supplied with various gases such as a gaseous glass raw material, a gaseous dope raw material, a fuel gas, a combustion assisting gas, and a buffer gas, and the glass fine particles generated by the flame hydrolysis ash of these gases are , the rod-shaped base material 21 in the rotating state
is injected to the outer periphery of the

At this time, the airflow from the eighth 11 flows smoothly along the circumferential surface of the rod-shaped base material 21 as shown by the dotted line in FIG. 1, and reaches the exhaust port of the exhaust system IB.

Glass particles are injected from the burner 1 toward the rotating rod-shaped substrate 21, and when the rod-shaped substrate 21 moves forward in the direction of the arrow V and backward in the opposite direction of the arrow V, the rod-shaped substrate 21 A porous glass layer 22 is formed on the outer periphery of 21 by depositing glass fine particles along its longitudinal direction.

When the deposition of the porous glass layer 22 is started in this manner, the laser light circumscribing the circumferential surface of the rod-shaped base material 2I is blocked by the porous glass layer 22, and the laser light is not incident on the detector 20. It disappears.

At this time, the controller 17 of the winder 1B detects the state in which light is cut off to the detector 20, and winds a minute amount of the wire 15 by operating the winder 4111B.

When the wire 15 is wound up, the burner 11 and the irradiator 18 attached thereto are guided by the guide rail 13 and the first
When the laser beam from the irradiator 1B slightly exceeds the circumferential surface of the porous glass layer 22, due to this traction,
Laser light is made incident on the detector 20 again.

When the laser beam enters the detector 20 again, the controller 17 stops the winder 16.

Thereafter, the burner 11 and the irradiator 18 are intermittently pulled in the direction of the arrow S until the porous glass layer 22 of a predetermined thickness is formed on the outer periphery of the rod-shaped base material 21. 22, and flows smoothly to the exhaust port.

Next, specific examples of the method of the present invention and comparative examples thereof will be explained.

Specific example As a rod-shaped base material, a single mode optical fiber base material was used, which was produced by the VAD method and had a core glass of 0.3% and an outer diameter ratio of core glass/cladding glass of 6.0. .

A ready-made five-tube burner was used as the burner, and its first flow path (center flow path) contained 1.5 IL/win of silicon tetrachloride,
, the second flow path contains hydrogen lO! ;L/l1in, argon 341/win in the third flow path, oxygen 1/win in the fourth flow path
01 /+*in were supplied respectively.

The outline of the entire apparatus, including the burner guide means and traction means, is shown in Figures 1 and 2. In this case, the laser photodetector was installed by drilling a small hole in the reaction vessel and connecting it to the exhaust port. Installed on the side.

A light guide connected to a light source was attached to the side of the burner, and the laser light was emitted from there.

The distance from the tip of the burner to the detector was 80 mm, and the distance from the rotation axis of the rod-shaped base material to the detector was 35 mm.

The rod-shaped base material was rotated at 3 Or, p, m and reciprocated for 500 m11 in the axial direction, and the moving speed at that time was 80 m/recommendation.

The above-mentioned glass fine particles were deposited under the above-mentioned conditions to form a porous glass layer having an outer diameter (diameter) of 50+ am around the outer periphery of the rod-shaped base material.

When the outer diameter of the porous glass layer formed in this specific example was measured, a portion with a stable outer diameter of 400 + sm could be secured in a 50Il±1 layer.

Comparative Example A porous glass layer was formed on the outer periphery of the rod-shaped substrate in the same manner as in the specific example above, except that the relationship between the burner, rod-shaped substrate, and exhaust port was set as shown in Figure 3, and the burner was kept in a fixed state. .

When the outer diameter of the porous glass layer formed in this comparative example was measured, it was found that the maximum outer diameter part was 47 layers, and the smallest outer diameter part was 52 m+*, and the outer diameter variation was large.

” - The porous glass layers formed on each side were each made into transparent glass in a helium-containing atmosphere at 1600°C, and white light was applied from one end of each transparent glass layer to examine the number of bubbles. There were 2 bubbles in the transparent glass layer of Example 1, whereas as many as 15 bubbles were observed in the glass layer of Comparative Example.

Furthermore, each base material consisting of the rod-shaped base material and the transparent glass layer was spun to have an outer diameter of 1251 Lm, and a silicone coating layer was formed on the outer periphery of the optical fiber immediately after the spinning.

Regarding the transmission characteristics of these optical fibers, the wavelength is 1.30 g.
When measured, the transmission loss of the specific example was as small as 0.38 dB/, while that of the comparative example was as large as 0.58 dB/.

Regarding the loss value caused by bubbles, the specific example is OdB.
/ks, and that of the comparative example is 0°15 dB/.

Furthermore, in a screening test with a measurement length of lO■,
The average breaking strength of the specific example was 5.1 kg, and the average breaking strength of the comparative example was 4.2 kg, and the specific example was excellent in this respect as well.

In addition, the results of cutting an optical fiber with a total length of 15 km every 1k11 and measuring the core diameter showed that the specific example had a small outer diameter variation of 8.5 ± 0.11 Lm, while the comparative example The diameter of the sample was 8.5±0.3 gm, which was accompanied by a large variation in outer diameter.

In addition, guide rails with various cross-sectional shapes, rollers, screw shafts, gears, etc. can be used as guide means for the burner.
By equipping the burner with a self-propelled traveling machine, the burner can also be made to travel along the guide rail.

Effects of the Invention J As explained above, when using the method of the present invention, when a porous glass layer is formed by injecting and depositing glass particles on the outer periphery of a rod-shaped base material, the burner is moved in a predetermined direction and the burner airflow is It is possible to form a porous glass layer with good properties and quality.

[Brief explanation of drawings]

1 and 2 are a plan view and a side view schematically showing an embodiment of the method of the present invention, and FIG. 3 is an explanatory diagram schematically showing a conventional method. 11-... Burner 13φ- Burner guide rail 14# Skewer Burner traction device 18φ... Exhaust system 19#φ Laser light irradiator 20 φ Laser light detector 21 φ Rod-shaped base material 2211φ・Porous glass layer O-φ・One point P on the exhaust port side...Rotation axis representative of rod-shaped base material Yoshio Saito, patent attorney Figure 1 Figure 2 F [

Claims (2)

[Claims] (1) The injection end of the burner faces one side of the outer periphery of the rod-shaped substrate, and the exhaust port of the exhaust system faces the other side of the outer periphery of the rod-shaped substrate, and the glass particles injected from the burner are
In a method for depositing glass fine particles, in which a porous glass layer is formed on the outer periphery of a rotating rod-shaped substrate by injecting and depositing the same, and the waste gas at this time is discharged from an exhaust port, injection of a burner is performed. The end is directed toward a point on the exhaust port side that is offset from the rotation axis of the rod-shaped substrate, and when forming a porous glass layer on the outer periphery of the rod-shaped substrate through the burner, the outer diameter of the porous glass layer is A method for depositing glass fine particles, characterized in that a burner is gradually rotated along a locus circle centered on the above-mentioned point as the glass particles increase in size. (2) The laser beam moving together with the burner is incident on the light receiving detector while circumscribing the glass deposition surface on the outer periphery of the rod-shaped base material, and each time the laser beam is blocked by the porous glass layer, the burner is A method for depositing glass particles according to claim 1, wherein the glass particles are moved in a predetermined direction.