JPS59184736A - Transparent vitrification of optical porous glass - Google Patents

Abstract

PURPOSE:To prolong the life of furnace core pipe and to perform transparent vitrification for obtg. products of high quality and stability by using a furnace core pipe comprising an opaque quartz pipe having a high purity quartz glass layer laminated on its inside peripheral face in the stage of transforming an optical porous glass to transparent glass. CONSTITUTION:A furnace core pipe 3 is constructed by laminating a layer of high puriy puartz glass layer 5 on the inside peripheral face of an opaque quartz pipe 4 formed with an opaque quartz glass body contg. bubbles. Said opaque quartz pipe 4 has heat resistance and said quartz glass layer 5 contains substantially no heavy metallic impurities which are undesirable for obtg. requiresd light transmitting characteristics. The furnace core pipe 3 is installed to a heating furnace 1 having a heating element 2 built therein. The porous glass is fed into the furnace core pipe 3 and is heated with said heating element 2 and transparent vitrification is performed while supplying a gaseous mixture consisting of He and Cl2.

Description

[Detailed description of the invention] Uninvented (base material for optical fiber, t for Rondo lens, :r
: 4; Relates to a transparent vitrification method for porous glass, which is one of the steps in producing l, etc.

VAD method, CVD method, etc.
When making J material, a gas phase chemical reaction (produced from this, tI
The sooty glass is deposited as porous glass in a predetermined shape.

For example, in the case of the VAD method, the above-mentioned soot-like glass is deposited in the shape of a rod to create a rod-shaped porous glass.
In method D, is the crow pay -17'j the outer circumference of the crow pipe? This bη porous glass is formed in layers.

The porous glass formed in this way is then turned into transparent glass by heating which also serves as a dehydration process.・
To prevent contamination with impurities, prepare a
By l3? Generally, the porous glass is heated (to 4400° C.) in the furnace tube in a mixed gas atmosphere.

When the above-mentioned transparent glass is made, gases such as HCl are generated from the porous glass, but the furnace, glass, and tube (furnace, glass, and tube) are safe to use to protect the heater of the heating furnace.

However, in the case of stone pod making furnaces and b-tubes, the 1ill1
However, when exposed to high heat as mentioned above, υζ
In addition, the outer circumferential surface becomes crystallized, devitrified, and easily damaged, resulting in the uneconomical need to replace the furnace top and tube with ♀jυ1, which is discarded. If it is used continuously, stable and good transparent vitrification cannot be expected.

The present invention has been made to eliminate the above-mentioned problems, and a specific method thereof will be explained below with reference to drawings and examples.

In the figure, 1 is a heating furnace, and this heating furnace 1 includes a heating element 2 such as a heating element, a carbon heating element, a fulconium heating element, etc.

In addition, (3) is made of a quartz-based glass body that has become opaque due to the inclusion of bubbles, etc. A high-purity quartz glass layer is placed on the inner circumferential wall 11 of the opaque quartz tube 4. The opaque quartz tube 4 has heat resistance, and the quartz glass layer 6 is composed of a heavy metal 1.5 which is not suitable for light transmission characteristics.
- Spring blunt (Fe1Cu.

Cr, etc.) is close to O (substantially (O)) and has a high purity.

The above-mentioned high-purity quartz glass layer 5 is formed on the inner peripheral surface of the opaque quartz tube 4 by depositing a predetermined oxide produced by known ΦCVD method on the inner peripheral surface of the opaque quartz tube 4. Alternatively, an organic compound (high purity) such as lincone may be applied to the inner circumferential surface of the opaque stone trachea 4, and this may be vitrified by heating.

In the figure, reference numeral 6 indicates porous glass, and this porous glass 6 may be made by the above-mentioned VAD method or by the external CVD method.

In the present invention, the porous glass 6 is placed in the furnace tube 3 and heated by the heating element. At this time, a mixture of He, Cr2, etc. is supplied into the furnace tube 3, and under these conditions Below, the porous glass 6 is made into transparent glass.

As a specific example, the porous glass 6 was made into transparent glass according to the following article (11).

Heating element 2 of heating furnace 1 Opaque quartz tube 4 of furnace core tube 3: outer diameter 90 + + + m, inner diameter 8
0 mm Quartz glass layer 5 of core/tube 3: 5I with a thickness of 2007 zm
Formed from O2 by MC VD method.

Temperature inside the furnace tube 3: 1450°C Gas atmosphere inside the furnace tube 3: f(e 201/mjn, '0211/win accompanied by 5ocz2 bubbled at room temperature.

Porous glass 6: VAD method [Koyorimono, GeO2-8
For bladed index optical fiber with 10□ core.

When a large number of porous glasses 6 were successively turned into transparent glass in the above process, the core tube 3 did not deform for a long time due to the thermal properties of the opaque quartz tube 4, and due to the presence of the high-purity quartz glass layer 5, No impurities were observed in the furnace core tube 3, and the following good results were obtained.

-j: 9, "÷" of a quartz tube (conventional example) made of -1+'+- material. In the case of the 5th case, abnormality occurred in the furnace and tube after about two weeks, but the furnace and tube 3 developed by the uninvented company withstood enough use for about one and a half months.

In the conventional example, it is not possible to obtain a base material with good optical transmission characteristics due to the abnormality of the furnace tube, but in the case of the optical fiber obtained by spinning the transparent vitrified base material according to the present invention, on average 2.4
It showed good transmission characteristics with saB/Km (λ=0.8571m).

As explained above, the present invention is a method of heating porous glass for optical systems in a heating furnace to make it transparent vitrification. The 44 characteristics are that porous optical glass is placed inside the furnace, tubes, and tubes to make it transparent, so abnormalities in the core and tubes, such as thermal deformation and the generation of impurities, can be suppressed for a long period of time. As a result, high-quality, stable and transparent glass can be achieved, and considerable savings can be achieved due to the long life of the reactor core tube and the reduced number of replacement operations. We are trying to reduce the cost of products.

[Brief explanation of drawings]

The drawing is an explanatory diagram showing one embodiment of the non-inventive method. 1...Carothermal furnace 2... Heating element ３　・・・・・・Heart/Suga 4... Opaque quartz tube 6...High-purity Ishifu glass eyebrows 6...Porous glass patent applicant Agent: Patent Attorney Makoto Ifuji Instep

Claims (1)

[Claims] In a method of heating porous optical glass in a heating furnace to make it transparent, the inner periphery of the opaque stone tube is
A furnace tube made of laminated iC high-purity quartz glass layers is provided in the heating furnace, and a porous optical system glass is placed inside the core layer to convert it into transparent glass. Transparent vitrification method for optical porous glass.