JP2888448B2 - Optical fiber preform manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an apparatus for manufacturing an optical fiber preform, and more particularly to an improvement in an apparatus for manufacturing an optical fiber preform by a method generally called an external method.

[Prior art]

In a method generally called an external method, glass fine particles are deposited around a target member to produce an optical fiber preform. Glass particles are produced in the flame of the burner and adhere to the surface of the target member. When manufacturing an optical fiber preform by these methods, the target member and the burner are covered with an exhaust chamber so that glass fine particles generated in the flame of the burner uniformly and efficiently adhere to the surface of the target member, I try to regulate the air flow. Therefore, conventionally, an apparatus for manufacturing an optical fiber preform by these methods usually has a structure as shown in FIG. 3 and FIG. FIG. 3 is a schematic plan view of the optical fiber preform manufacturing apparatus as viewed from above, and FIG. 4 is a cross-sectional view taken along line IV of FIG. In these figures, the target member 1 is rotated while its both ends are held by a glass lathe or the like, and a burner 3 is arranged in a lateral direction of the target member 1. The target member 1 may be removed later, or may be a silica-based glass rod that will later become the core of the optical fiber. Burner 3
Is supplied with a fuel gas and an auxiliary combustion gas to generate a flame 4. Further, a glass raw material gas is supplied to the burner 3, and the glass raw material gas is introduced into the flame 4. A hydrolysis reaction is caused, and Si
Glass particles such as O2 are generated. The glass particles are sprayed on the surface of the target member 1, and the glass particles adhere to the surface of the target member 1. The target member 1 is rotating, and the burner 3 moves (traverses) in the axial direction of the target member 1, so that the glass particle deposition layer 2 is formed in a column shape around the target member 1. By traversing one burner 3 many times, or by using a plurality of burners 3 and traversing them once, the columnar glass particle deposition layer 2 is formed. The exhaust chamber 5 is formed so as to cover the flame 4 generated from the target member 1 and the burner 3, and regulates the flow of the glass particles by rectifying the exhaust. In this figure, the exhaust chamber 5 includes the target member 1
Covers the entire area where the glass fine particle deposition layer 2 is formed, but covers only a narrow area of the flame 4 (glass fine particle flow), and traverses integrally with the burner 3. It may be configured as follows. When the glass fine particle deposition layer 2 reaches a predetermined size, the deposition is completed, and the completed glass fine particle deposit, which is a composite of the target member 1 and the glass fine particle deposition layer 2, is later heated in a high-temperature furnace. It is processed, and the portion of the glass particle deposition layer 2 is sintered and turned into a transparent glass, and then becomes a base material for making an optical fiber. The exhaust chamber 5 is used for rectifying the flow of glass particles as described above. However, if glass particles or the like adhere to the inner surface, the desired rectifying action cannot be obtained, and uniform deposition of glass particles cannot be achieved. Therefore, it is necessary to clean the inner surface of each glass particle deposition step. Therefore, in consideration of ease of handling and easy-to-handle weight at that time, the exhaust chamber 5 is usually made of a thin material such as titanium (5 mm).
Degree) It is composed of a metal plate.

[Problems to be solved by the invention]

However, the exhaust chamber made of such a thin metal plate is deformed by heat in the glass particle deposition process, the air flow in the chamber changes, and the function of uniform deposition of glass particles is not performed. There is a problem that there is. That is, considerable heat is generated from the flame of the burner in the glass particle deposition step, and the temperature of the exhaust chamber may rise to 300 ° C. or more due to the radiant heat. At this temperature, the metal plate undergoes thermal deformation, resulting in breakage of the chamber and plastic deformation. Such breakage or deformation may cause a gap in a part of the chamber to cause a change in the air flow in the chamber, resulting in a failure to uniformly deposit the desired glass particles. In view of the above, an object of the present invention is to provide an apparatus for manufacturing an optical fiber preform improved so that the chamber is not deformed by heat during the deposition of glass fine particles so that uniform deposition of glass fine particles can be stably performed. Aim.

[Means for Solving the Problems]

In order to achieve the above object, according to the present invention, a holding device for holding a target rod so as to rotate, a glass particle generating device traversed in the axial direction with respect to the target rod, and a glass particle An apparatus for manufacturing an optical fiber preform having a chamber for rectifying a flow of glass fine particles generated from a generator, wherein a heat shield plate is provided inside the chamber so that the chamber is not deformed even if it is thermally deformed. It is characterized in that it is loosely fixed.

[Action]

A heat shield plate is provided inside the chamber for rectifying the glass particle flow. Therefore, the heat generated by the glass particle generator is not directly radiated to the wall of the chamber, and the temperature rise of the chamber wall can be suppressed, and the deformation of the chamber due to the temperature rise can be eliminated. In addition, the heat shield plate itself may be heated and deformed by the heat generated by the glass particle generator, but even if it is thermally deformed, it is loosely fixed to the chamber so as not to cause deformation of the chamber. ing. for that reason,
Even if the heat shielding plate is thermally deformed, there is no disadvantage that the chamber is deformed. Therefore, it is possible to avoid a situation in which the chamber is deformed or damaged due to the heat of the glass particle generator during the deposition of the glass particles, and the flow of the glass particles is not as expected, and stable glass particle deposition is possible. Become.

【Example】

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 and 2 schematically show an apparatus for manufacturing an optical fiber preform according to an embodiment of the present invention. FIG. 1 is a plan view seen from above, and FIG.
FIG. 2 is a sectional view taken along line II. The apparatus for manufacturing an optical fiber preform shown in these figures is basically the same as the apparatus for manufacturing an optical fiber preform shown in FIGS. 3 and 4, and corresponding portions are denoted by corresponding numbers. And a detailed description is omitted. According to the present invention, as shown in FIGS. 1 and 2, the heat shield plate 6 is hung on the inner surface of the upper surface of the exhaust chamber 5 in a relatively loose state. That is, it is suspended by, for example, several springs or attached to the inner surface of the upper surface of the chamber 5 via a flexible thin pin or the like. The heat shield plate 6 is used to block the transfer of heat to the upper surface of the chamber 5 that is particularly heated by the flame 4 from the burner 3, and is made of the same material (for example, titanium) and the same thickness (for example, titanium) as the exhaust chamber 5. For example, it is composed of a 5 mm) metal plate. In the optical fiber preform manufacturing apparatus thus configured, a silica-based glass rod serving as a core when later formed into an optical fiber is used as the target member 1, and both ends thereof are gripped by a chuck of a glass lathe. By doing
Rotate. The burner 3 for generating fine glass particles includes H _{2 as} a fuel gas, O ₂ as an auxiliary gas, and SiCl as a glass material.
₄ and Ar as an inert gas are supplied, and glass fine particles are generated in the flame 4 by a flame hydrolysis reaction. The burner 3 is traversed in the axial direction of the target member 1. Burner 3 while generating glass particles from burner 3
Is traversed once to form one glass fine particle deposition layer 2 around the target member 1. This traverse is repeated a plurality of times in the reciprocating direction to form a plurality of layers of the glass fine particle deposition layer 2. When the columnar glass fine particle deposition layer 2 having a predetermined thickness is formed, this deposition step is completed. During this deposition process, the heat generated by the flame 4 of the burner 3 causes the upper surface of the chamber 5 to become the highest temperature. In this embodiment, however, the heat shield plate 6 is suspended from the upper inner surface. Heat transfer is interrupted. As a result, the temperature of the upper surface of the chamber 5, which is the highest temperature, actually rises only up to about 150 ° C. during the deposition of the glass particles, and no damage due to thermal deformation or plastic thermal deformation was observed. The heat shield plate 6 itself has undergone considerable heat and has been thermally deformed, but is loosely fixed and has a degree of freedom with respect to the thermal deformation. And no plastic deformation was observed when the temperature was returned to room temperature after the deposition of the fine glass particles was completed. In the above embodiment, the exhaust chamber 5 is long enough to cover the entire glass fine particle deposition layer 2.
It is shorter in the axial direction of the target member 1 and has a burner 3
Of course, the present invention can be similarly applied to an exhaust chamber of a type that traverses together with the burner 3 integrally with the burner 3.

【The invention's effect】

According to the optical fiber preform manufacturing apparatus of the present invention, the chamber is not deformed by the heat during the deposition of the fine glass particles, and as a result, the flow of the fine glass particles is always stabilized.
Uniform deposition of glass particles can be stably performed.

[Brief description of the drawings]

1 and 2 schematically show an apparatus for manufacturing an optical fiber preform according to an embodiment of the present invention. FIG. 1 is a plan view seen from above, and FIG. 3 and 4 schematically show a conventional optical fiber preform manufacturing apparatus, and FIG. 3 is a plan view seen from above, and FIG.
The figure is a sectional view taken along line IV in FIG. DESCRIPTION OF SYMBOLS 1 ... Target member, 2 ... Glass fine particle deposition layer, 3 ... Burner for glass fine particle generation, 4 ... Flame, 5 ... Exhaust chamber, 6 ... Heat shield plate.

Continuation of front page (72) Inventor Masahiro Horikoshi 1440 Mutsuzaki, Sakura-shi, Chiba Pref. Sakura Plant of Fujikura Electric Wire & Cable Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C03B 37/00-37/16

Claims (1)

(57) [Claims] 1. A holding device for holding a target rod so as to rotate, a glass fine particle generator traversing the target rod in the axial direction, and a glass fine particle flow generated from the glass fine particle generator. An apparatus for manufacturing an optical fiber preform having a rectifying chamber,
An apparatus for manufacturing an optical fiber preform, wherein a heat shield plate is loosely fixed in the chamber so as not to cause deformation of the chamber even if the heat shield is thermally deformed.