JPH0738143U - Manufacturing equipment of porous preform for optical fiber - Google Patents

Abstract

(57) [Summary] [Structure] Inside the reaction vessel 1, the upper end is fixed by a gripping device having a rotary motor (not shown) outside the reaction vessel 1, and the lower end is connected to the burner 2 for synthesizing glass particles. The target rod 3 is installed at a position corresponding to the fired flame. An observation window 5 fixed to the side surface of the reaction vessel 1 by an observation window support member 4.
An exhaust port 7 having an exhaust pipe 6 leading to an exhaust gas treatment device (not shown) is provided. Further, a ring 9 for forming an air curtain is provided on the observation window supporting member 4 connecting the reaction container 1 and the observation window 5. A hole 10 for ejecting gas is opened on the ring 9 toward the inside of the reaction container. According to the present invention, the problems that have conventionally occurred can be solved, and a high-quality porous glass preform for optical fibers can be easily and stably manufactured.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an apparatus used for manufacturing a porous preform for optical fibers.

[0002]

[Prior art]

 As one of the general methods for producing a porous glass preform for optical fibers, there is a method using an apparatus for producing a porous glass preform for optical fibers as shown in FIG. In this method, at least the lower end of the target rod 3 installed in the reaction vessel 1 is rotated upward while moving at a predetermined speed, and the glass particles synthesized by the glass particle synthesizing burner 2 are deposited on the lower end of the target rod 3. The porous base material 8 for fiber is manufactured.

The burner 2 for synthesizing glass particles is supplied with a combustion gas, for example, a hydrogen gas which is a combustible gas and an oxygen gas which is a combustion supporting gas, and further is supplied with a glass raw material gas such as SiCl ₄ gas. To do. Next, the glass raw material gas is hydrolyzed by the flame of the combustion gas to generate glass fine particles.

In FIG. 2, reference numeral 5 is an observation window for observing the state of the lower end of the optical glass porous glass preform 8 during production, that is, the production state. This is provided on the side surface of the reaction container 1 through the observation window supporting member 4. Further, reference numeral 7 indicates, for example, glass fine particles, which are generated as unreacted gas or glass fine particles in the reaction container 1, but are not attached to the porous glass preform 8 for an optical fiber and are floating outside the reaction container 1. An exhaust port for exhausting, to which an exhaust pipe 6 is connected.

By the way, according to the conventional method, as the production of the porous glass preform 8 for optical fiber progresses, the glass often floating in the reaction vessel 1 on the inner surface of the observation window 5 with the passage of time. Fine particles are attached. This phenomenon causes a problem that the manufacturing state of the porous glass preform 8 for optical fiber cannot be observed. More specifically, there is a problem that the internal conditions cannot be grasped through the observation window 5, so that even if an abnormality occurs in the manufacturing state, the manufacturing conditions cannot be corrected.

[0006]

[Problems to be solved by the device]

 Therefore, a method for manufacturing a porous glass preform for optical fibers that does not cause the inside of the observation window to become cloudy due to the adhesion of glass particles even during the production of a large-scale porous glass preform for optical fibers. , Specifically, improvement of the observation window was urgent. A method conventionally proposed as a means for solving this problem is to open a gap inside the observation window and eject air from the gap to form an air curtain.

However, in the conventional air curtain, although the amount of the glass particles adhered was reduced, the inside still remained cloudy due to the adhesion of the glass particles until the observation. In particular, in recent years, the size of the porous glass preform for optical fibers to be produced has been increasing, and as a result, the production time for each porous glass preform for optical fibers has become longer. Therefore, the frequency and probability of observation windows becoming cloudy during manufacturing are more likely, and the problem is becoming more serious.

[0008]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention proposes an optical fiber by depositing glass particles produced by a burner for synthesizing glass particles into a rotating target rod in a reaction vessel having an observation window for observing the inside. In a device for manufacturing a porous glass preform for use in the above, a ring having a hole for ejecting gas into the reaction container is provided inside the observation window.

[0009]

[Action]

 In this way, by providing a ring for ejecting gas toward the inside of the reaction vessel and forming an air curtain through the ring, it is possible to change the size and number of the ejection holes provided in this ring so that You can change the strength of the air curtain. Therefore, even if the manufacturing conditions of the porous glass preform for optical fiber manufactured in the reaction container are changed, it is possible to easily cope with the change. Further, by changing the positions of the holes in the ring, it is possible to change the ejection angle of the gas, for example, air, and it is possible to easily change the formation position of the air curtain. These actions make it possible to observe the production state of the porous glass preform for optical fibers in the container under more stable conditions, and thus it is possible to produce high-quality porous glass preforms for optical fibers. And are possible.

[0010]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The apparatus for producing a porous glass preform for optical fibers used as an example has a structure as shown in FIG. That is, as in the conventional case, the upper end of the reaction vessel 1 is fixed by a gripping device outside the reaction vessel 1 and having a rotary motor (not shown), and the lower end of the reaction vessel 1 from the burner 2 for synthesizing glass particles. The target rod 3 is installed in a position that corresponds to the fired flame. An exhaust port 7 having an observation window 5 fixed by an observation window supporting member 4 and an exhaust pipe 6 leading to an exhaust gas treatment device (not shown) is provided on the side surface of the reaction vessel 1. Further, a ring 9 for forming an air curtain is provided on the observation window supporting member 4 connecting the reaction container 1 and the observation window 5. It should be noted that holes 10 for ejecting gas are provided on the ring 9 at predetermined intervals in the circumferential direction, and each hole 10 is opened toward the inside of the reaction vessel 1.

When the porous glass preform for optical fibers was manufactured using the above-described manufacturing apparatus, glass microparticles were formed inside the observation window 5 until the porous glass preform for optical fibers had a desired size. It did not adhere.

Hereinafter, a comparative example of the present invention will be described in detail. As a comparative example, a porous glass preform for optical fibers was manufactured using a conventional manufacturing apparatus as shown in FIG. Specifically, the upper end of the reaction vessel 1 is fixed by a gripping device having a rotary motor (not shown), and the lower end of the reaction vessel 1 is provided with the target rod 3 at a position where it hits the flame ejected from the burner 2 for synthesizing glass particles. On the side surface of the reaction vessel 1, there is provided an observation window 5 fixed by an observation window supporting member 4 and an exhaust port 7 having an exhaust pipe 6 leading to an exhaust gas treatment apparatus (not shown). Is. When a porous glass preform for optical fibers was manufactured with this device, when the final desired length was reduced to about one-tenth, glass particles adhered to the observation window, making observation impossible. .

In this example, the example of manufacturing the porous glass preform for optical fiber by the VAD method using only one burner for synthesizing fine glass particles was used, but a plurality of burners for synthesizing fine glass particles were used. Therefore, it is clear that it is also effective in the case of simultaneously synthesizing the core part and the clad part.

In the present invention, the gas supplied to the ring may be supplied once through the filter. In this way, a clean gas, for example, air can be ejected from the ring, so that it is easy to prevent impurities from being mixed into the reaction vessel from the outside. Furthermore, since the gas to be ejected from the ring hole can be freely selected, the atmosphere inside the reaction vessel can be freely set.

[0015]

[Effect of device]

 According to the manufacturing apparatus of the present invention, the problems that have conventionally occurred can be solved, and a high quality porous glass preform for optical fibers can be easily and stably manufactured.

[Brief description of drawings]

FIG. 1 is an apparatus for producing a porous glass preform for optical fibers used in this example.

FIG. 2 is an apparatus for manufacturing a porous glass preform for an optical fiber used in this comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reaction container 2 ... Burner for synthesizing glass particles 3 ... Target rod 4 ... Observation window support member 5 ... Observation window 6 ... Exhaust pipe 7 ... Exhaust port 8 ... Porous glass preform for optical fiber 9 ... Ring 10 ... Hole

Claims (1)

[Scope of utility model registration request] 1. A porous glass preform for optical fibers is manufactured by depositing glass particles produced by a burner for synthesizing glass particles in the form of a rotating target rod in a reaction vessel having an observation window for observing the inside. In the apparatus described above, a ring having a hole for ejecting gas into the reaction vessel is provided inside the observation window, and the apparatus for producing a porous preform for optical fibers.