JPS5992927A - Method for manufacturing focusing optical fiber base material - 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 The present invention relates to a method of manufacturing a preform for a bovine fiber, and particularly to a method of manufacturing a preform for a convergent optical fiber using a vapor phase axial method.

For the production of optical fiber base material, silicon halide as a raw material for quartz glass and a dopant for controlling the refractive index of quartz glass, such as C, eot4-
POO63- etc. are transported with a suitable carrier gas,
This is ejected from the center blade of an oxyhydrogen gas burner, and the combustion flame oxidizes and hydrolyzes it.

A method of spraying the lower part of a rotating refractory target and pulling it up according to the rate of silica deposition to create a cylindrical porous sintered silica body, which is then placed in a high-temperature heating furnace and turned into transparent vitrification. is known, and this is generally called the gas-phase axis method.

A method for producing a base material for a fiber with a real-bundle refractive index distribution using this gas-phase axis method is to use two or more burners or nozzles to feed raw material gases with different dopant concentrations as indicated at @. ) Rabu@useuse, the method is to dehydrate this with oxyhydrogen moxibustion to make a porous silica sintered body with a refractive index, or to increase the dopant concentration from the center of a concentric multi-tube burner. A high raw material gas is supplied, and a raw material gas with a lower peripheral force and dopant concentration is blown out, and the entire gas is wrapped in an acidic water flame for oxidation and hydrolysis to produce porous silica sintered with a concentration distribution. Although methods for obtaining aggregates are known, all of these methods involve blowing out two or more raw material gases having different dopant concentrations from separate blow-off ports.

When the air flow on the silica deposited surface becomes discontinuous, variations in Vc such as temperature tend to occur, making it difficult to maintain a constant appropriate refractive index distribution. Also; Nori=
; and 4 companies Regarding the manufacturing method of the base material for the original fiber with a changed refractive index distribution - deposit silica, change the temperature distribution on the surface of the refractory mark, and change the precipitate shape according to the temperature distribution. Although a method has been proposed in which the refractive index distribution of the base material for optical fiber is adjusted by changing the temperature distribution of the silica deposition surface alone, this method requires the use of flame g]
It is necessary to properly maintain the shape, the linear velocity of the raw material gas, the shape of the deposition surface, the flow of gas on the deposition surface, etc., so it is not possible to achieve the goal with good reproducibility by simply adjusting the temperature distribution. It is not possible to manufacture base materials for optical fibers.

On the other hand, with regard to the porous silica sintered body obtained by this vapor phase axial attachment method, the sintered body is heated in a high-temperature heating furnace in order to remove the moisture that is produced as a by-product when the silica is generated and the OH groups that inevitably remain. A method is used in which chlorine gas or 1,000 onyl chloride gas is allowed to coexist when turning the material into transparent glass through treatment, but in this treatment, germanium dioxide as a dopant is intercalated as germanium tetrachloride.

There is a disadvantage that the concentration distribution of germanium dioxide in the resulting optical fiber base material changes, making it difficult to adjust it to a positive refractive index distribution.To solve this problem, the above-mentioned dehydration method A method has also been proposed in which oxygen is added to chlorine gas during treatment to suppress the reaction between chlorine and germanium dioxide and to reduce changes in temperature distribution, but the amount of volatilization of germanium dioxide depends on the various conditions during dehydration. , for example, chlorine gas concentration, atmospheric gas flow rate, furnace temperature,
The refractive index of the optical fiber base material cannot be adjusted by this alone, as it varies greatly depending on factors such as the density of the porous sintered silica, and these methods are considered to be of little practical use. There is.

The present invention relates to a method for producing an original fiber matrix that solves these disadvantages, and involves flame hydrolysis of a silicon compound and a dopant to produce a porous silica sintered body, which is then heated in a high heat environment. In the method of producing transparent vitrification in a furnace and dividing the original fiber base material into bags, raw material gas with a uniform composition consisting of a silicon compound, a dopant, and a gas is passed through the center of a single concentric multi-tube burner to form a porous material. The method is characterized in that a sintered silica body is produced and then heat treated in a gas atmosphere capable of reacting with the dopant to control the distribution of the dopant and turn it into transparent glass.

To explain this, the present defenders have conducted various studies on the target optical fiber base material σ] refraction; 4S adjustment method, and in particular, have conducted detailed research on the volatilization phenomenon of germanium dioxide as a lever dopant. This amount of volatilization reaches a certain equilibrium state depending on the density distribution of the porous silica sintered body and the type and degree of atmospheric gas in the Toguchi thermal furnace when it is vitrified, and after reaching this equilibrium state, almost no It was discovered that the dopant does not volatilize and becomes a kind of stable state, and if the a-degree distribution of the dopant contained in this porous silica sintered body has a shape close to the desired distribution at least in the center, It does not necessarily have to be a radial, so-called square distribution, and therefore, the production of this porous silica sintered body does not require a complicated burner like the conventional technology, and instead has a single circular center The present invention was completed by confirming that it is sufficient to introduce raw material gas of uniform composition from the center of the city burner.

Therefore, the method of the present invention is to flame-hydrolyze raw materials consisting of a dopant compound, a dopant, and a dopant 1 using an oxyhydrogen flame, so that the concentration of the dopant is as low as a dopant from the center to the outer periphery. The process consists of two steps: creating a porous silica sintered body with progressively smaller pores, and then heat-treating it in a gas atmosphere that reacts with the dopant. can be produced by supplying this raw material gas from the center of a single central multi-tube burner and subjecting it to flame hydrolysis.In this case, the composition of the raw material gas may be two or more. There is no need to eject these from separate nozzles or to use two or more burners to precisely adjust the distribution when the porous sintered silica is compacted. By simplifying the burner structure, it is possible to reduce the factors that depend on the burner structure, as well as reduce the variable factors such as temperature, substitution, and pressure in the raw material supply system. This is because the porous silica sintered body can be manufactured with extremely good developability, and in fact, this makes it easy to maintain various conditions at the same time, so the density of the porous silica sintered body and the concentration distribution of the dopant can be easily controlled. It is possible to easily obtain a porous silica sintered body having a substantially constant value.

The production of this porous silica sintered body is specifically B'. The central part is a raw material gas supply pipe in which a silicon compound, a dopant, and an inert gas for transportation are uniformly mixed, and the outside is a hydrogen gas supply pipe. A single concentric multi-tube is used in which supply pipes and oxygen gas supply pipes are sequentially arranged circularly, and where necessary, inert gas supply pipes are arranged concentrically to control the combustion speed of this oxyhydrogen flame. This silicon compound is 5iOt4.
, H81Ct3-0H3SiCchi -8iH4-5i(
QC2I(+)4 etc. - Also Ge as a dopant
Examples include Cl4-pocz3BBr3. This raw material gas is supplied from the center of the single concentric multi-tube burner mentioned above, and is converted into 5IO2 and C) by flame water decomposition.
e 02-P2O3,P, 203 is deposited on a quartz rod, thereby obtaining a porous silica sintered body containing the dopant.

In the present invention, the distribution of the dopant is controlled by heat-treating this porous '0' silica sintered body in a gas atmosphere capable of reacting with the dopant.

This allows the excess dopant contained in the porous silica sintered body to volatilize, thereby controlling the concentration distribution of the dopant in the optical fiber matrix used as the opening. To explain this using GeO2, which contributes most significantly to the refractive index distribution, as an example, when this porous silica sintered body is heated in a heating furnace in an atmosphere containing chlorine gas, the GeO2
2, a part of which becomes Ge0L4 according to the following formula % formula % (1) and one car is emitted, but this () e
Although the reaction rate of 02 to GeCl4 depends on the chlorine concentration and temperature, once a certain amount of GeC44 has volatilized, it will not proceed any further even if the treatment time is increased, and therefore the vitrified optical fiber The amount of GeO2 in the base material remains constant. This is because the amount of GeO2 remaining in the optical fiber base material mainly depends on the density or degree of sintering of the porous silica sintered body.

When treated under the same conditions, the lower the density ()e○2
On the other hand, the density of the porous silica sintered body tends to be lower towards the periphery where the center is worn out. Optical fiber base material can be easily obtained. Conventionally, this optical fiber base material is provided with a ground layer that does not contain any dobber (J) at its outermost layer.

A porous silica layer for the cladding is deposited on a porous silica sintered body using a separate burner, or a cladding layer is made to resemble a rough tube over a glass sintered core for an optical fiber. However, according to the method of the present invention, it is possible to provide a low-density porous sintered silica layer on the outermost part of this single burner by changing the conditions. It can be obtained by a step of forming an optical fiber base material having substantially a cladding.

In addition, the reaction of formula (1) described above does not proceed unless it is above 800°C2j, and when the temperature exceeds 1000°C, vitrification of the porous silica sintered body begins to progress, and along with this, Ge044
Since the volatilization of the porous silica sintered body is suppressed, in this case there is a disadvantage that the adjustment of the processing temperature, time-gas concentration, density of the porous silica sintered body, etc. becomes complicated. Shika L,
In this case, when hydrogen chloride is used as the treatment agent, the reaction proceeds according to the following formula 4 (2), and this also proceeds at temperatures below 800°C, which is faster than the reaction according to the above formula (1). Since the reaction rate of
You can start the car. In addition, the use of CO gas is also effective for the volatilization of Ge 02, and in this case, the following formula % formula % (3) When V is used together with gas, it has the effect of promoting the volatilization of GeO2 by chlorine gas according to the linear formula % formula % (4), and according to this, chlorine gas alone has the effect of accelerating the volatilization of GeO2 by
The gas concentration required for 5% can be set to a chlorine a degree of 0.1 to 1Jf%, and when a high concentration of chlorine gas is used, chlorine gas remains in the optical fiber base material. The effect is given when the bubbles are prevented, but phosgene gas may also be used, and this C twist is Q (2GeO2+2CoC42→GeCt4+C○2
-(5) allows Ge○2 to be completely volatilized.

Therefore, the method of the present invention uses chlorine, hydrogen chloride, and carbon 4i as gases capable of reacting the porous silica sintered body produced by the above-described method with a dopant.

Heat treatment is performed in a mixed gas atmosphere containing one or two types of phosgene, etc., but this gas is argon,
It may be used after being diluted with an inert gas such as nitrogen or helium, and these may normally be used at a degree of 0.1 to 15 volume. If the fi8 temperature of this process is below 400℃, the volatilization of the dopant will be insufficient;
If the temperature is higher than this, the volatilization of the porous silica sintered body will be suppressed as the vitrification progresses, so it is preferable that the temperature is in the range of 400 to 1200°C.

Although the method of the present invention has been described above with respect to the gas phase axial method, it can also be effectively used in the external method as well.

Next, examples of the method of the present invention will be given.

Example 1 5icz4 in the center of the quartz burner 1 with concentric 4-grain pattern
1o 5v-1/min, ()e Ct420 mA'
7 minutes, argon gas 3 for transporting POO433ml/H
A uniformly mixed raw material gas of 70rni/min was heated on the outside with H23, 2!1 min-Ar O, 6L15f, 026.
7! 1 minute, and flame hydrolyzes it in a reactor 2 as shown in FIG. When a porous silica sintered body 4 was prepared with a length of 5i, the apparent density of this body was 0.22.

Next, this porous silica sintered body is 0! , gas, HOl
When the reaction rate was examined by heating the gas to 1000°C in an atmosphere of C4 gas containing 2 volumes of CO gas, the results shown in Figures 2 and 3 were obtained. For HOt gas, its processing temperature is 70°C.
When the test was carried out at 0 to 1200°C, the results shown in Figure 4 were obtained. When the reaction rate at 100°C was investigated, the results shown in Figure 5 were obtained - it was confirmed that the lower the density, the higher the reaction rate.

In addition, the porous lyrica sintered body C obtained by the same method as described above has a density of 0.22) and A containing Ct2 gas with an IO capacity of
r gas (A) + A containing HCt gas of 5 volumes
It was treated at 800°C for 2 hours in r gas (B) + Ar gas (0) containing 3% by volume of Ct2 gas and 2% by volume of CO gas, and then vitrified in a high-temperature furnace at 1500°C. By using this as the base material for optical phino (-) and finding out the refractive index of these, it became as shown in Fig. An investigation of the transmission characteristics of a 0.85 μm optical fiber (-NitsuX,) made by
These results were as shown in Table 1.

Here, (N, (B), and (C) in Fig. 6 correspond to the above gas compositions, respectively, and (D) &
This shows the results obtained when such dopant volatilization treatment is not carried out at all, and also the O part in which the maximum refractive index difference + ro indicates the core diameter.
1 Table Example 2゜H2 and 02' in the method of Example 1! i7 (711) was treated in the same manner at 2.8℃ for 1 minute and at 5.617 minutes, respectively, to produce a porous silica sintered body, which had a relatively low density of 0.08 g/-. It became a thing.

Next, when this is made into transparent glass in a high temperature furnace at 500°C, it is mixed with 5 volumes of at2 and 3 volumes of CO2.
When the test was carried out in an Ar gas atmosphere containing gas, it was found that the density of the surrounding area was extremely low. It became the base material.

[Brief explanation of the drawing]

The if diagram is a schematic vertical cross-sectional view of the reactor used in the examples of the present invention, Figure 2 is a diagram showing the relationship between these concentrations and reaction rates when Hat +' at2 e- is used, and Figure 3 is a diagram showing the relationship between the concentration and reaction rate when Hat +' at2 e- is used. Figure 4 shows the relationship between CO gas concentration and reaction g when using 7JDC62 gas, Figure 4 shows the relationship between processing temperature and reaction rate when using HCl and C42 gas, and Figure 5 shows only the porous silica sintered body. Figure 6 shows the refractive index of optical fiber base materials obtained by using various treatment agents. Figure 7 shows the relationship between density and reaction rate. Figure 7 shows the relationship between density and reaction rate. rr?
2 shows the refractive index of the original fiber base material obtained by processing the porous sintered silica body according to the method of the present invention. DESCRIPTION OF SYMBOLS 1... Burner, 2... Reverberatory furnace, 3... Substrate, 4... Porous silica sintered body. Patent Applicant: Shin-Etsu Chemical Co., Ltd.
)-Yuyxsya (00)
- Miga 1 Bunu & (g/c Roy) Figure 6 6n Procedural Amendment December 1982] 5 ['' 1. Indication of the case 1982 Patent Application No. 200105 2. Name of the invention Focusing type optical fiber motherboard 9 Manufacturing method of lumber 3, relationship with the case of the person making the amendment Patent applicant name Shin-Etsu Chemical Co., Ltd. 4 Agent address 270 Nagai Hill ljC Tokyo, 4-9 Nipponka Honmachi, Chuo-ku, Tokyo 103 0858□O859
) 6. "Claims", "Detailed Description of the Invention" and "Drawings (Figure 6)" of the specification to be amended 1) Specification difference 9 ↓ Page 1, line 4 to page 2 The claims stated on the second line are amended as shown in the attached sheet. 2) Table 1 described on page 17, lines 1 to 6 of the specification is amended as follows. 3) Amend Figure 6 as shown in the attached sheet. Above (Attachment) Claim 1: A silicon compound and a dopant are flame-hydrolyzed to produce a porous silica sintered body, which is then turned into transparent vitrification in a high-temperature heating furnace to produce an optical fiber matrix. In the method,
A raw material gas with a uniform composition consisting of a silicon compound and a dopant is passed through the center of a single concentric multi-tube burner.
The focusing process is characterized by producing a porous sintered silica body, which is then heat-treated in a gaff atmosphere that can react with the dopant to control the distribution of the dopant and turn it into transparent vitrification. Method for manufacturing molded optical fiber base material. 2 The gas that can react with the dopant is halogen gas. Claim 1 is one or more selected from hydrogen halide, -carbon oxide, and phosgene.
A method for producing a convergent optical fiber preform as described in Section 1. No. 6 4-f diameter-

Claims (1)

[Claims] 1. A silicon compound and a dopant are flame-hydrolyzed to produce a porous sintered silica, which is then turned into transparent glass in a high-temperature furnace to produce a base material for optical fiber. In the manufacturing method, a raw material gas with a uniform composition consisting of a silicon compound, a dopant, and a sinter is flowed from the center of a single concentric multi-tube burner to produce a porous silica sintered body, which is then injected with a dopant. 1. A method for producing a convergent optical fiber preform, which comprises controlling the distribution of a dopant by performing n1 heat treatment in a gas atmosphere capable of reacting with the preform, thereby converting it into transparent glass. 2. The focusing optical fiber motherboard according to claim 1, wherein the gas capable of reacting with the dopant is one or more selected from halogen gun, hydrogen halide-carbon monoxide, and phosgene force. Method of manufacturing wood.