JPH06305763A - Production of optical fiber preform - Google Patents

Abstract

PURPOSE:To provide the production method of an optical fiber preform, in which even a large sized preform can be supported with sufficient strength and the transmission loss characteristics is not adversely affected at the time of depositing the porous glass preform for optical fiber on the tip of a starting member by the VAD method, dehydrating the preform thus obtained and converting it into transparent glass. CONSTITUTION:The porous glass preform for optical fiber deposited on the tip of the starting member by the VAD method is suspended by using a jig attached to the starting member and introduced into a furnace to dehydrate the preform and to convert it into transparent glass. At this time, the jig 3 made of platinum is used. Although a jig 3, every part of which is made of platinum, may be used, another jig 3, only the pin 5 of which is made of platinum, can be used when this jig 3 has such structure that the preform 1 is connected to the tip of this jig 3 with the pin 5. Accordingly, the jig 3 has sufficient strength for supporting even a large sized preform since platinum has high mechanical strength and also is not corroded even in a gaseous chlorine based atmosphere of the inside of the furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical fiber preform, and at the time of producing a porous glass preform for an optical fiber by the VAD method and in an obtained furnace of the obtained porous glass preform. The present invention provides a method for supporting a porous glass preform without destroying it during the treatment with.

[0002]

2. Description of the Related Art In the manufacture of optical fiber preforms, VAD
There is a step of depositing glass fine particles for optical fiber on the tip of the starting member by a method to form a porous glass preform, and then introducing this into a furnace and treating it. Here, the treatment means a dehydration treatment of the porous glass preform in a chlorine-based gas atmosphere, a transparent vitrification in an inert gas atmosphere such as He, and the like. FIG. 1 is a schematic view of an apparatus for performing vitrification of a porous glass preform obtained by the VAD method. Reference numeral 1 is a porous glass preform, for example, a porous glass body composed of SiO ₂ —GeO ₂ fine particles. A porous glass layer composed of SiO ₂ glass fine particles for clad is formed around, and 2 is made of SiO ₂ glass as a base material when this porous glass preform is manufactured by the VAD method. The starting member 2 is provided with a through hole 21 which is orthogonal to the lengthwise direction and into which a pin which is a fixing means described later is inserted, and 3 is the starting member 2.
Is a holding jig that vertically supports the hollow cylindrical SiO ₂ rod 4 and a pin 5 made of SiO ₂ glass. The hollow cylindrical SiO ₂ rod 4 is orthogonal to its lower end in the vicinity of its lower end. A pair of pin mounting holes 41, 41 are formed. Then, the starting member 2 is fitted into the lower end portion of the hollow cylindrical SiO ₂ rod 4, and the pin 5 is fitted into and supported by the through hole 21 of the starting member 2 and the pin mounting hole 41 of the rod 4.
Reference numeral 6 is a SiO ₂ tube, which is provided with an opening 61 below it, and is supplied with, for example, chlorine-based gas or He gas. 7 is S
It is a heating element that surrounds the iO ₂ tube 6.

With the above construction, the porous glass preform 1 is vertically hung by the holding jig 3 via the starting member 2 and guided into the SiO ₂ tube 6 at a predetermined speed. SiO
_{(2) The} inside of the tube 6 is set to a mixed gas atmosphere of chlorine-based gas and He gas, and the ambient temperature is set to about 900 by radiant heat from the heating element 7.
If the temperature is maintained at ℃, the porous glass preform 1 is dehydrated. After that, the porous glass preform 1 can be made transparent by setting the atmosphere temperature to about 1500 ° C. in a He gas atmosphere. By the way, conventionally, the holding jig 3, especially the pin 5 is made of Si having the same composition as the porous glass.
O ₂ glass has been used. The reason is to reduce the mixture of impurities, which is the biggest obstacle to the transmission loss of the optical fiber. When using iron or the like as a material, the wavelength band of 1.33 μm and 1.55 μm used for optical communication can be obtained. This is because a peculiar absorption peak that influences appears and the transmission loss of the manufactured optical fiber increases, which is not suitable for practical use. The above is the holding jig for dehydration and transparent vitrification of the porous glass preform 1. When the porous glass preform 1 is deposited on the tip of the starting member by the VAD method, the holding member supports the starting member. The same applies to jigs.

[0004]

However, as a pin forming a part of the jig, SiO ₂ having the same composition as the porous glass is used.
The use of glass is effective for optical properties, but since glass is a brittle material, it has a risk of breaking. Particularly, due to the increase in weight due to the recent increase in the size of optical fiber preforms, the pins sometimes break when actually holding the porous glass.

[0005]

SUMMARY OF THE INVENTION From the above viewpoints, the present invention is intended to provide a method for producing and supporting a porous glass preform without breaking the jig, and performing the treatment thereof. The invention according to claim 1 is characterized in that the jig is made of platinum when the porous glass preform for an optical fiber is deposited on the tip of the starting member vertically supported by the jig. . Also,
The invention according to claim 2 is characterized in that, when the porous glass preform for optical fiber deposited on the tip of the starting member vertically supported by the jig is introduced into the furnace for processing, the jig is used. Is made of platinum. Furthermore, the invention according to claim 3 characterized in that the jig is
The rod-shaped main body has a mounting portion into which the starting member is fitted and inserted at least at its tip end, and a fixing means for fixing the starting member fitted into the mounting portion. The fixing means is made of platinum. is there. Here, the term "made of platinum" means platinum, an alloy of platinum and rhodium, one in which zirconium oxide is dispersed in platinum, one in which zirconium oxide is dispersed in an alloy of platinum and rhodium, and the like.

[0006]

Since the jig for vertically supporting the porous glass preform for the optical fiber through the starting member is made of platinum, it has sufficient mechanical strength to withstand the increase in size of the porous glass preform and also has a chlorine content. Since it has a substantially stable property even in an atmosphere such as a system gas, it does not contaminate the porous glass.

[0007]

[Example] Three types of pins were prepared as fixing means constituting a part of the jig. (A) SiO ₂ glass rod having a diameter of 3 mmφ and a length of 60 mm (B) Platinum rod of the same size (C) Platinum-zirconium oxide rod of the same size Then, as shown in FIG. 1, using these pins. Suspend the porous glass preform, and 150 in He gas atmosphere.
Transparent vitrification was achieved under the conditions of 0 ° C. and 4 hours. The total weight of the porous glass preform is about 4000g.
Is. Table 1 shows the results of comparing the mechanical reliability (breakage frequency) of the above three types of pins.

[0008]

[Table 1]

Further, when the transmission loss wavelength characteristics of the respective optical fibers obtained by melting and drawing the respective optical fiber preforms transparentized by using the respective pins were examined, the results were inferior to each other. It was

[0010]

According to the method for producing an optical fiber preform according to the method of the present invention, when a porous glass preform is suspended by a jig through a starting member and is introduced into a furnace for treatment,
Since the jig is made of platinum, it has sufficient mechanical strength to support a large-scale porous glass preform and has the advantage that it is not attacked by the atmosphere in the furnace.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an apparatus for performing vitrification of a porous glass preform.

[Explanation of symbols]

1 Porous Glass Preform 2 Starting Member 21 Through Hole 3 Holding Jig 4 Rod 41 Pin Mounting Hole 5 Pin 6 SiO ₂ Tube 61 Opening 7 Heating Element

Claims (3)

[Claims] 1. When depositing a porous glass preform for an optical fiber on a tip of a starting member vertically supported by a jig, the jig is made of platinum, and the jig is made of platinum. Production method. 2. When the porous glass preform for optical fiber deposited on the tip of a starting member vertically supported by a jig is introduced into a furnace for processing, the jig is made of platinum. A method for producing a characteristic optical fiber preform. 3. The jig comprises a rod-shaped main body having a mounting portion into which a starting member is fitted and inserted at least at its tip end, and a fixing means for fixing the starting member fitted into this mounting portion. The method for manufacturing an optical fiber preform according to claim 1, wherein the fixing means is made of platinum.