JPH0114181B2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Objectives of the Invention] The present invention relates to an apparatus for manufacturing an optical fiber base material, and in particular, the present invention relates to a manufacturing device for an optical fiber base material, in which a glass film is formed on the outer periphery of a target rod using high-frequency plasma as a heat source. It is related to the device.

The MCVD method and VAD method are the main methods currently used for manufacturing optical fiber base materials. The reaction heat source used for these is an oxyhydrogen burner flame.
When high-frequency plasma is used as a heat source, the general method is to form a core rod by depositing glass on the tip of a target that is pulled down at a constant speed while rotating, or to deposit glass uniformly on the outer peripheral surface of the target rod that serves as the core material. There are methods such as forming a glass film that becomes the cladding material, but with the latter method,
If you move the high-frequency plasma generator, the plasma flame will lack stability, and the jet tip of the plasma flame will become unstable due to the surrounding atmosphere, causing the temperature of the target rod to fluctuate in the longitudinal direction, making it difficult to maintain uniformity. It is difficult to form a glass film having a certain refractive index, and it is not easy to purify the glass film after forming it in this way. In particular, mixing of moisture contained in the air during the formation of the glass film deteriorates the performance of the optical fiber manufactured from the base material.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber preform manufacturing apparatus that can solve the above-mentioned difficulties and produce optical fibers with excellent performance.

[Summary of the Invention] The present invention provides a target rod made of a core material that penetrates a reaction chamber and is mounted on a glass lathe so that it can rotate and move laterally, and a high-frequency In an apparatus for manufacturing an optical fiber base material that forms a glass film of a cladding material while reacting raw material gas using plasma as a heat source, a gas sealing means for introducing an inert gas into a through hole of the target rod of the reaction chamber; The apparatus is characterized in that it includes a means for detecting the pressure in the reaction chamber with a pressure sensor and interlocking with an exhaust valve, and exhausts the gas in the reaction chamber through a buffer tank and a heat exchanger.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. The figure is a configuration diagram of an apparatus for manufacturing an optical fiber base material of the present invention, in which 1 is a high-frequency plasma generator, 2 is a raw material gas introduction tube for a glass film 7 that will be a cladding material, and 3
are gas seal caps at both ends of the reaction chamber 4, 5 is a glass lathe, 6 is a target rod serving as a core material, 8 is a limit switch, 9 is a bed, 10 is a
is a buffer tank, 11 is an exhaust pipe, 12 is a heat exchanger, 13 is a scrubber, 14 is an exhaust fan, 15
is an exhaust valve, and 16 is a pressure sensor.

To manufacture an optical fiber base material using this apparatus, first, argon gas is passed through the high-frequency plasma generator 1 to generate a plasma flame, and then the argon plasma flame is switched to an oxygen plasma flame. Then, a raw material mixed gas of silicon tetrachloride (SiCl ₄ 2000 mg/min) and halogenated carbon (CF ₂ Cl ₂ 500 c.c./min) is introduced from the raw material gas inlet pipe 2 under the plasma flame using oxygen as a carrier gas. The glass film 7 is deposited on the outer peripheral surface of the target rod 6 (quartz glass). At this time, the temperature of the target rod 6 is 1450°C, and the target rod 6 is attached to the glass lathe 5 and rotates.At the same time, the glass lathe 5 moves the glass head 9 from side to side in the longitudinal direction of the target rod 6. A film 7 is formed. In this case, high-purity nitrogen gas continues to be fed into the through hole of the target rod 6 of the gas seal cap 3, and its gas curtain action prevents outside air containing moisture from entering the reaction chamber 4. There is. The reaction chamber 4 is made of quartz glass because of its high temperature, and the internal pressure is monitored by a pressure sensor 16 and automatically adjusted by an exhaust valve 15.
While maintaining the pressure at 3 mmAg, unreacted gas and exhaust gas are passed through the exhaust pipe 11, buffer tank 10, cooling heat exchanger 12, and scrubber 13 to the exhaust fan 14.
and exhaust through valve 15.

In this way, moisture-containing outside air is prevented from entering the reaction chamber 4, and the inside of the reaction chamber 4 is used for the interlocking operation of the pressure sensor 16 and the exhaust valve, as well as for the buffer tank 10 and heat exchanger 12. Due to the buffering effect, fluctuations in the atmosphere within the reaction chamber 4 are alleviated, and a stable plasma flame can be connected.

Therefore, the temperature of the target rod 6 is stabilized, a homogeneous glass film 7 is formed in a uniform layer, and a homogeneous optical fiber base material containing no impurities can be manufactured.

〔Effect of the invention〕

As explained above, according to the optical fiber base material manufacturing apparatus of the present invention, it is possible to uniformly form a glass film that is a homogeneous cladding material containing no impurities around the outer periphery of a target rod that is a core material. ,
By using this optical fiber base material, it is possible to produce an industrial effect that it becomes easy to manufacture optical fibers with excellent performance.

[Brief explanation of drawings]

The figure is a configuration diagram of an optical fiber preform manufacturing apparatus according to an embodiment of the present invention. 1: High frequency plasma generator, 2: Raw material gas introduction pipe, 4: Reaction chamber, 5: Glass lathe,
6: target rod, 7: glass membrane, 10: buffer tank, 12: heat exchanger.

Claims (1)

[Claims] 1. A target rod made of a core material that penetrates the reaction chamber and is attached to a glass lathe so that it can be rotated and moved laterally, and the material gas is reacted using high-frequency plasma as a heat source on the outer periphery of the part where the target rod is located inside the reaction chamber. In an apparatus for manufacturing an optical fiber base material in which a glass film of a cladding material is formed while a glass film is formed as a cladding material, a gas sealing means for supplying an inert gas into a through hole of the target rod of the reaction chamber, and a pressure inside the reaction chamber are controlled. What is claimed is: 1. An optical fiber base material manufacturing apparatus, comprising: a means for interlocking with an exhaust valve while detecting with a sensor, and exhausting gas in a reaction chamber through a buffer tank and a heat exchanger.