JPH06305762A - Burner for producing optical fiber preform and manufacture of the same - Google Patents

Abstract

PURPOSE:To control the refractive index distribution of the outside deposited part of the optical fiber preform by dividing the outermost layer of a multiple tubular burner into at least two sections. CONSTITUTION:The patitions 17 are provided in the inside of the ouermost layer of the concentric multiple tubular burner to divide the layer into two sections, i.e, the upper section 15 and the lower section 16. The porous glass layer consisting of fine glass particles is formed on the periphery of the rod used as the core while supplying GeC1. and SiCL. to the central part 11, Hz to the 12, a seal gas to the third layer 13, 02 to the fourth 2-14, the above seal gas to the upper section 15 of the outermost layer and a smaller amount of the seal gas than the amount supplied to the upper section 15 to the lower section 16 of the outermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner for producing an optical fiber preform by a VAD method or an OVD method and a method for producing an optical fiber preform using the burner. (EN) Provided is a base material having a desired refractive index profile by controlling the index distribution.

[0002]

2. Description of the Related Art A schematic diagram of a typical VAD method is shown in FIG.
A schematic diagram of the VD method is shown in FIG. Reference numeral 1 denotes a porous glass layer serving as a clad. For example, soot generated by using three concentric multi-tube burners 2 is deposited around the rod 3 to a predetermined thickness to form an optical fiber preform. In the VAD method of FIG. 5, the rod 3 is a porous glass-like material that serves as a core, and in the OVD method of FIG. 6, the rod 3 is composed of a core or a core and a part of a clad, and is made of transparent glass. It has been transformed into

[0003]

However, the burner 2 may be mixed with a doping material for changing the refractive index, if necessary. Among them, there is a doping material whose amount that can be doped largely changes depending on the surface temperature of the rod on which soot is deposited.
₄ , BBr ₃ , SnCl ₄ and the like. FIG. 7 shows an example of a cross-section and gas arrangement of a concentric multi-tube burner of this kind.
In the figure, 11 is GeCl ₄ and SiCl ₄ in the central part,
12 O ₂ is supplied Ar, 14 as H _2, 13 is a seal gas at the third layer in the second layer in the fourth layer. When sooting the glass 1 using this burner 2, the deposition state and the surface temperature distribution of the soot deposition portion at that time are as shown in FIG. For example, G
Surface temperature of eO ₂ soot deposit is 500-800 ° C
When the deposition is performed within a certain range, the refractive index of the central portion becomes high as shown in FIG. For this reason, the characteristics of the optical fiber preform manufactured using such a burner may be naturally limited.

[0004]

SUMMARY OF THE INVENTION The present invention provides a burner capable of controlling the refractive index profile of an optical fiber and a method of manufacturing an optical fiber preform using the burner, which is characterized by the above. One of them is that the burner for producing an optical fiber preform has a multi-tube structure, and the outermost layer thereof is divided into at least two. When the area is divided into two, the area ratio may or may not be equal. Another aspect of the present invention is to use a burner having a multi-tube structure, the outermost layer of which is divided into at least two parts, when forming a porous glass layer made of fine glass particles around a core rod. In addition, the porous glass layer is formed while flowing a different flow rate of the seal gas in each of the divided portions. The core rod may be either a transparent glass rod or a porous glass rod.

[0005]

Since the outermost layer of the multi-tube burner is of the split type, it is possible to control the flow rate of the seal gas flowing through this split portion. Therefore, the soot adhesion amount can be controlled by controlling the flow rate of the seal gas when the soot is generated by using the burner and the soot is deposited around the core rod.
In particular, when the dopant includes one that depends on the surface temperature of the deposition part, the surface temperature of the deposition part is controlled by controlling the flow rate of the seal gas, so that the amount of dopant in the soot can be adjusted. The refractive index can be adjusted.

[0006]

【Example】

Embodiment 1 FIG. 1 is a burner for manufacturing an optical fiber preform according to the present invention. This burner has a concentric quintuple tube structure, and a partition 17 for dividing the inside is provided in the outermost layer to form an upper part 15 and a lower part 16 which are divided into two parts, and Ar for sealing flows into each of them. Be done. Other configurations are the same as those in FIG. 7, and GeCl ₄ and SiCl ₄ in the central portion 11, H _{2 in} the second layer 12, Ar as a seal gas in the third layer 13,
O ₂ is supplied to the fourth layer 14. The upper part 15,
The amount of gas supplied to the lower portion 16 can be independently controlled, and the partition 17 is formed so as to be horizontal by connecting the central axes of the burners. When the amount of Ar gas flowing in the upper part 15 is larger than the amount of Ar gas flowing in the lower part 16, the amount of the soot adhered is hindered by the seal gas at the upper part of the generated soot, and the adhesion efficiency decreases. FIG. 2 shows the soot deposition shape and temperature distribution when a large amount of seal gas is supplied to the upper portion 15, and FIG. 3 shows the soot accumulation shape and temperature distribution when a large amount of seal gas is supplied to the lower portion 16. In other words, the refractive index profile is adjusted by moving the soot adhering region with respect to the surface temperature distribution of the soot deposition portion formed by the burner fire.

Example 1 Soot was deposited around a pure quartz rod having an outer diameter of 25 mmφ using the burner shown in FIG. SiCl in the central part 11
₄ : 1.0 liters / minute GeCl ₄ : 0.01 liters / minute Second layer 12 has H ₂ : 12 liters / minute Third layer 13 has seal gas Ar: 0.4 liters / minute Fourth layer 1
4 to O _2: 16 liters / min, the surface temperature of the soot deposition unit that the maximum temperature was 700 ° C.. Under these conditions, the flow rates of the upper 15 seal gas and the lower 16 seal gas in the outermost layer of the burner were set to three types, a, b and c, as shown in Table 1. The refractive index profile at this time is shown in FIGS.
In this way, the refractive index profile can be controlled by changing the flow rate of the seal gas.

The number of divisions of the outermost layer of the burner may be arbitrary, and the division ratio is not limited to equal division and can be appropriately selected.
In addition to Ar, He or N ₂ can be used as the seal gas.

[0009]

INDUSTRIAL APPLICABILITY As described above, the present invention can easily provide a burner suitable for depositing SiO ₂ soot containing a dopant such as GeO ₂ on a rod, and by using this burner, a desired refraction index can be obtained. An optical fiber preform having a rate distribution can be manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view of a burner for manufacturing an optical fiber preform according to the present invention.

FIG. 2 is an explanatory view showing an example when soot is deposited using the burner according to the present invention shown in FIG.

FIG. 3 is an explanatory view showing another example when soot is deposited using the burner according to the present invention shown in FIG.

4 is an explanatory view showing each example of a refractive index profile when soot is deposited around a rod using the burner according to the present invention shown in FIG.

FIG. 5 is a schematic diagram of a typical VAD method.

FIG. 6 is a schematic diagram of a typical OVD method.

FIG. 7 is a cross-sectional view of a conventional burner used in the method of FIGS.

8 is a temperature distribution diagram of a soot accumulation state and a soot accumulation portion by the burner shown in FIG.

9 is a refractive index profile of a soot deposited portion by the burner shown in FIG.

[Explanation of symbols]

 1 Porous Glass 2 Burner 3 Rod 11 Center Part (1st Layer) 12 2nd Layer 13 3rd Layer 14 4th Layer 15 Upper 16 Lower 17 Partition

Claims (5)

[Claims] 1. A burner for producing an optical fiber preform, which is a multi-tube burner for producing an optical fiber preform, wherein an outermost layer thereof is divided into at least two parts. 2. A multi-tube burner for producing an optical fiber preform, wherein the outermost layer is divided into two and the division area ratios thereof are equal to each other. For burner. 3. A multi-tube burner for producing an optical fiber preform, wherein the outermost layer is divided into two and the division area ratios are different from each other. For burner. 4. A multi-tube burner, the outermost layer of which is divided into at least two, is used to form a porous glass layer composed of glass fine particles around a core rod. A method for producing an optical fiber preform, wherein the porous glass layer is formed while flowing a different flow rate of a seal gas in each part. 5. The rod for core is a transparent glass rod or a porous glass rod.
A method for manufacturing the optical fiber preform described above.