Apparatus and method of producing porous glass preform

Abstract

(Problem) To provide an apparatus for manufacturing a porous glass substrate capable of suppressing pulses associated with fluctuations in the flow rate of vaporized gas, and a method for manufacturing such a material. (Solution) A manufacturing apparatus for a porous glass substrate comprises a plurality of deposition devices that produce a porous glass substrate by generating raw material fine particles in an acid-hydrogen flame from a vaporized raw material compound and attaching the generated raw material fine particles onto a rotating starting member. The manufacturing apparatus comprises at least one storage container for storing liquid raw materials by type, at least one steam generating device for vaporizing the raw materials in the storage container, and at least one air passage for supplying the raw materials vaporized by the steam generating device to a plurality of deposition devices. The air passage comprises a common air passage shared to supply the vaporized raw materials to a plurality of deposition devices, and a plurality of individual air passages branched from the common air passage to supply the vaporized raw materials toward individual deposition devices. And, each of the multiple individual passages is equipped with a flow controller that controls the flow rate of the vaporized raw material compound, a steam valve that controls the on / off flow of the vaporized raw material compound, and a valve that is positioned upstream of the flow controller and can adjust the flow area.

Description

Technology Field

[0001] The present invention relates to a method and apparatus for manufacturing a porous glass substrate, and in particular, to an apparatus and method for manufacturing characterized by suppressing the pulverization of the porous glass substrate caused by pressure fluctuations of a vaporized gas. Background Technology

[0002] Various methods have been proposed to manufacture optical fiber preforms. Among them, the well-known VAD method is a method for manufacturing a porous glass preform consisting of a core layer and a clad layer by mounting a starting member on a shaft that rotates and rises, lowering it into a reaction chamber, and attaching and depositing glass fine particles generated by a core deposition burner and a clad deposition burner installed in the reaction chamber at a predetermined angle with respect to the axial direction of the starting member to the leading edge of the starting member.

[0003] The porous glass substrate manufactured in this manner is dehydrated and sintered in a furnace equipped with a sealable core tube, an electric furnace that heats part or approximately the entirety thereof, a gas introduction port for introducing any gas into the core tube, and a gas discharge port for discharging gas from the core tube. Dehydration is carried out by heating the porous glass substrate to about 1,100°C in a dehydration gas composed, for example, of chlorine, oxygen, argon, and helium. Vitrification is carried out by heating the porous glass substrate to about 1,500°C in a helium atmosphere, for example. At this time, for example, during dehydration and vitrification, the porous glass substrate is lowered from top to bottom and passed through a heating zone by the electric furnace to perform dehydration and vitrification.

[0004] However, in a structure where raw material gas is supplied from a single steam generator to multiple VAD devices, pressure fluctuations may occur within the vaporized gas flow path due to the overlap of the timing of the start and end of manufacturing in multiple manufacturing devices or liquid supply into the steam generator, causing the vaporized gas flow rate to fluctuate and resulting in a problem where pulverization occurs in the porous glass base material. The problem to be solved

[0005] The present invention is made in consideration of the above situation and aims to provide an apparatus for manufacturing a porous glass matrix and a method for manufacturing a porous glass matrix capable of suppressing pulses accompanying fluctuations in the flow rate of vaporized gas. means of solving the problem

[0006] To solve the above problem, the manufacturing apparatus for a porous glass substrate related to the present invention comprises a plurality of deposition devices that produce a porous glass substrate by generating raw material fine particles in an acid-hydrogen flame from a vaporized raw material compound and attaching the generated raw material fine particles onto a rotating starting member. The manufacturing apparatus comprises at least one storage container for storing liquid raw materials by type, at least one steam generating device for vaporizing the raw materials in the storage container, and at least one air passage for supplying the raw materials vaporized by the steam generating device to a plurality of deposition devices. The air passage comprises a common air passage shared to supply the vaporized raw materials to a plurality of deposition devices, and a plurality of individual air passages branched from the common air passage to supply the vaporized raw materials toward individual deposition devices. In addition, each of the multiple individual passages is equipped with a flow controller for controlling the flow rate of the vaporized raw material compound, a steam valve for controlling the on / off flow of the vaporized raw material compound, and a valve positioned upstream of the flow controller and capable of adjusting the flow area.

[0007] In the present invention, it is preferable to additionally provide a control unit that adjusts the opening of a valve provided in an individual air passage so that the pressure downstream of the valve in the individual air passage is 60 to 95 percent of the pressure of the raw material compound vaporized in the steam generating mechanism.

[0008] In the present invention, the raw material compound is preferably a silicon compound and / or a dope compound. The dope compound is preferably a germanium compound.

[0009] In addition, the method for manufacturing a porous glass matrix related to the present invention is characterized by adjusting the opening of a valve in any of the above-mentioned manufacturing devices such that the pressure downstream of the valve is 60 to 95 percent of the pressure of the raw material compound vaporized in the steam generating device. Brief explanation of the drawing

[0010] Figure 1 is an overall diagram of the manufacturing apparatus. Specific details for implementing the invention

[0011] The porous glass matrix of silica glass according to the present invention is manufactured, for example, by the manufacturing apparatus (1) shown in Fig. 1.

[0012] The manufacturing apparatus (1) is equipped with two VAD devices (31A, 31B). The VAD devices (31A, 31B) are a type of deposition apparatus that produces a porous glass base material by generating raw material fine particles from a vaporized raw material compound in an acid-hydrogen flame and attaching the generated raw material fine particles onto a rotating starting member. The raw material compound in the manufacturing apparatus (1) includes a silicon compound and a doping compound (doping agent). The doping compound is preferably, for example, a germanium compound. The manufacturing apparatus (1) is equipped with storage containers (2, 12) that store the above-mentioned liquid raw material compounds by type. The storage container (2) stores SiCl4 as a silicon compound. The storage container (12) stores GeCl4 as a doping agent.

[0013] Additionally, the manufacturing device (1) is equipped with a steam generating mechanism (3, 13) that vaporizes a raw material compound in a storage container. The steam generating mechanism (3) is installed in correspondence with the storage container (2). It vaporizes SiCl4 stored in the storage container (2) and supplies it to two VAD devices (31A, 31B). The steam generating mechanism (13) is installed in correspondence with the storage container (12) and vaporizes GeCl4 stored in the storage container (12) and supplies it to two VAD devices (31A, 31B).

[0014] In addition, although the present embodiment describes a configuration in which two VAD devices (31A, 31B) are connected as an example, more VAD devices may be connected. Also, two sets of the reservoir and steam generating mechanism are installed, one for the silicon compound and one for the dope agent, but either one set may be used, or three or more sets may be formed.

[0015] The manufacturing apparatus (1) is equipped with a passage that supplies a raw material compound vaporized in a steam generating apparatus (3, 13) to a VAD apparatus (31A, 31B). In this embodiment, the manufacturing apparatus (100) is equipped with a passage (4, 104A, 104B) for a silicon compound (SiCl4) and a passage (14, 114A, 114B) for a dope compound (GeCl4). A pressure indicator controller is installed in the passage to measure the pressure of the gas at the installation location. Hereinafter, the pressure indicator controller is referred to as a PIC (Puressure Indicating Controller).

[0016] The air passage is provided with a common air passage (4, 14) that is shared to supply vaporized raw material compounds to multiple VAD devices, and individual air passages (104A, 104B, 114A, 114B) that branch off from the common air passage and supply vaporized raw material compounds toward individual VAD devices (10A, 10B). Each individual air passage (104A, 104B, 114A, 114B) is equipped with a flow controller (mass flow controller; 103A, 103B, 113A, 113B) for controlling the flow rate of the vaporized raw material compound, a steam valve (102A, 102B, 112A, 112B) for controlling the on / off flow of the vaporized raw material compound, a valve (101A, 101B, 111A, 111B) positioned upstream of the flow controller and capable of adjusting the flow area, and a PIC (105A, 105B, 115A, 115B) for measuring the pressure downstream of the valve.

[0017] The SiCl4 gas vaporized in the steam generator (3) is supplied to the VAD device (31A, 31B). A PIC (105A, 105B) is installed in the common air passage (4) that supplies the SiCl4 gas to measure the pressure of the SiCl4 gas vaporized in the steam generator (3). Individual air passages (104A, 104B) branch off from the common air passage (14) toward the VAD device (31A, 31B). The SiCl4 gas toward the VAD device (31A) passes through the individual air passage (104A), then passes through the valve (101A), PIC105A, steam valve (102A), and flow controller (mass flow controller; 103A) to be supplied to the core forming burner (32A). Likewise, SiCl4 gas directed toward the VAD device (31B) passes through individual passages (104B), valves (101B), PIC (105B), steam valves (102B), and flow controllers (103B) and is supplied to the core forming burner (32B). It is preferable to connect a passage for introducing inert gas between the steam valves (102A, 102B) and the flow controllers (103A, 103B), and to turn on / off (open / close) the steam valves (106A, 106B) installed in the passages for introducing inert gas and the steam valves (102A, 102B) so that when one side is opened, the other side is blocked, thereby introducing vaporized gas into the flow controllers (103A, 103B) during manufacturing and inert gas when manufacturing is stopped.

[0018] The GeCl4 gas vaporized from the steam generator (13) is supplied to the VAD device (31A, 31B) as a second component. A PIC (115A, 115B) is installed in the common air passage (14) that supplies the GeCl4 gas to the steam generator (13) to measure the pressure of the GeCl4 gas vaporized from the steam generator (13). Individual air passages (114A, 114B) branch off from the common air passage (14) toward the VAD device (31A, 31B). The GeCl4 gas toward the VAD device (31A) passes through the individual air passage (114A), passes through the valve (111A), PIC (115A), steam valve (112A), and flow controller (113A), and is supplied to the core forming burner (32A). Likewise, GeCl4 gas directed toward the VAD device (31B) is supplied to the core forming burner (32B) via the valve (111B), PIC (115B), steam valve (112B), and flow controller (113B). It is preferable to connect a passage for introducing inert gas between the steam valves (112A, 112B) and the flow controllers (113, 113B), and to turn on / off the steam valves (116A, 116B) installed in the passage for introducing inert gas and the steam valves (112A, 112B) so that when one side is opened, the other side is blocked, thereby introducing vaporized gas into the flow controllers (113A, 113B) during manufacturing and inert gas when manufacturing is stopped.

[0019] In addition, as a third component, C-Ar, N2, Air, etc. are supplied to the VAD device (31A, 31B) via valves (20A, 20B) and flow controllers (21A, 21B). SiCl4 gas and GeCl4 gas become silica fine particles and GeO2 fine particles through flame hydrolysis in an acid-hydrogen flame in the clad-forming burners (33A, 33B, 34A, 34B) in addition to the core-forming burners (32A, 32B), and are deposited on the rotating starting member.

[0020] Pressure fluctuations in the vaporized gas (SiCl4 gas and GeCl4 gas) supplied to the VAD device may occur due to the overlap of liquid supply to the steam generating mechanism, the start or stop timing of manufacturing in other VAD devices, etc.

[0021] The manufacturing apparatus (1) is equipped with a valve (101A, 101B, 111A, 111B) upstream of a flow controller (103A, 103B, 113A, 113B) in the supply path of the vaporized gas, and intentionally causes a pressure loss by adjusting the opening of this valve when a pressure fluctuation occurs. This reduces the influence of pressure fluctuations upstream of the valve on downstream of the valve and suppresses the pulverization of the porous glass base material caused by fluctuations in the flow rate of the vaporized gas. Types of valves to be used include gate valves, check valves, butterfly valves, globe valves, ball valves, etc.

[0022] Specifically, it is effective to adjust the pressure downstream of the valve to 60 to 95 percent of the pressure of the vaporized gas (vaporized silicon compound and / or vaporized dope compound) in the steam generating mechanism (3, 13).

[0023] If the pressure downstream of the valve is set to 60% or less of the pressure of the vaporized gas in the steam generating mechanism, the pressure difference between the upstream and downstream of the flow controller becomes small, and there is a possibility that the set flow rate will not flow.

[0024] On the other hand, if the pressure downstream of the valve is set to 95% or more of the pressure of the vaporized gas in the steam generating mechanism, the effect of suppressing pressure fluctuations caused by pressure drop is small.

[0025] It is preferable that the opening degree of each valve be automatically adjusted so that the pressure downstream of the valve in the individual air passage is 60 to 95 percent of the pressure of the raw material compound vaporized in the steam generating device, based on the pressure detected by the PIC installed immediately downstream of the valve (e.g., PIC105A for valve (101A)) and the PIC placed in the common air passage (e.g., PIC (5) for SiCl4 gas). In order to realize such automatic adjustment, it is preferable that the manufacturing device (1) be equipped with a control unit (40). By configuring it in this way, precise control becomes possible. In addition, FIG. 1 illustrates a configuration in which a control unit (40) automatically adjusts the opening of a valve (101A) in an individual passage (104A) of SiCl4 gas toward a VAD device (31A), but it is preferable to perform automatic adjustment by the control unit (40) in the same way for other valves (101B, 111A, 111B).

[0026] According to this method, the occurrence of pulverization in porous glass substrates can be suppressed at low cost without making large-scale facility investments.

[0027] [Example 1]

[0028] The pressure in PIC (5) was set to 0.06 MPa, and SiCl4 was flowed by adjusting the opening of the valves (101A, 101B) so that the pressure in the individual PICs (105A, 105B) was 50, 70, 80, or 98% of the pressure in PIC (5). The flow controllers (103A, 103B) were adjusted for SiCl4 in the range 0 to 1200 cc / min. With other conditions kept the same, a porous glass substrate was manufactured, and the flow rate fluctuation in the flow controllers when pressure fluctuations occurred and the presence or absence of pulses in the porous substrate were checked. The results are shown in Table 1.

[0029]

[0030] When the pressure ratio was 70% and 80%, even if there was a pressure fluctuation upstream of the valve, there was no fluctuation in flow rate downstream of the valve (very small), and no pulse occurred.

[0031] On the other hand, when the pressure ratio was 50%, the SiCl4 flow rate did not reach the set flow rate, so the target optical properties could not be obtained.

[0032] In addition, when the pressure ratio was 98%, the SiCl4 flow rate of the flow controller fluctuated, causing pulverization in the porous glass substrate.

[0033] [Example 2]

[0034] The pressure at PIC (15) was set to 0.06 MPa, and GeCl4 was flowed by adjusting the opening of the valves (111A, 111B) so that the pressure at PIC (115A, 115B) in the individual air passages was 50, 70, 80, or 98% of the pressure at PIC (15). The flow controllers (113A, 113B) were adjusted for GeCl4 in the range 0 to 50 cc / min. With other conditions kept the same, a porous glass substrate was manufactured, and the flow rate fluctuation in the flow controllers when pressure fluctuations occurred and the presence or absence of pulses in the porous substrate were checked. The results are shown in Table 2.

[0035]

[0036] When the pressure ratio was 70% or 80%, even if there was a pressure fluctuation upstream of the valve, there was no fluctuation in flow rate downstream of the valve and no pulse occurred.

[0037] On the other hand, when the pressure ratio was 50%, the GeCl4 flow rate did not reach the set flow rate, so the target optical properties could not be obtained.

[0038] In addition, when the pressure ratio was 98%, the flow rate of GeCl4 in the flow controller fluctuated, causing pulverization in the porous glass substrate.

[0039] As described above, according to the manufacturing apparatus and manufacturing method of the present invention, pulse accompanying fluctuations in the flow rate of vaporized gas can be suppressed. Explanation of the symbols

[0040] 1 manufacturing device 2, 12 storage containers 3, 13 Steam generating apparatus 4, 14 common ventilation 101A, 101B, 111A, 111B, 20A, 20B valves 102A, 102B, 106A, 106B, 112A, 112B, 116A, 116B steam valve 103A, 103B, 113A, 113B, 21A, 21B flow controllers 5, 15, 105A, 105B, 115A, 115B PIC 31A, 31B VAD device 32A, 32B core forming burner 33A, 33B, 34A, 34B Clad forming burner 40 control unit

Claims

Claim 1 An apparatus for manufacturing a porous glass substrate comprising a plurality of deposition devices for producing a porous glass substrate by generating raw material fine particles in an acid-hydrogen flame from a vaporized raw material compound and attaching the generated raw material fine particles onto a rotating starting member, the apparatus comprises at least one storage container for storing the liquid raw material compound by type, at least one steam generating device for vaporizing the raw material compound in the storage container, and at least one air passage for supplying the raw material compound vaporized by the steam generating device to the plurality of deposition devices, wherein the air passage comprises a common air passage shared for supplying the vaporized raw material compound to the plurality of deposition devices, and a plurality of individual air passages branched from the common air passage to supply the vaporized raw material compound toward individual deposition devices, and each of the plurality of individual air passages comprises a flow controller for controlling the flow rate of the vaporized raw material compound, a steam valve for controlling the on / off flow of the vaporized raw material compound, and a device disposed upstream of the flow controller and capable of adjusting the flow area. A manufacturing apparatus comprising a valve, wherein the manufacturing apparatus further comprises a control unit for adjusting the opening degree of the valve provided in the individual air passage so that the pressure downstream of the valve in the individual air passage is 60 to 95 percent of the pressure of the raw material compound vaporized in the steam generating apparatus. Claim 2 A manufacturing apparatus according to claim 1, characterized in that the raw material compound is a silicon compound and / or a dope compound. Claim 3 A manufacturing apparatus characterized in that, in claim 2, the compound for the dope is a germanium compound. Claim 4 A method for manufacturing a porous glass matrix, characterized in that, in a manufacturing apparatus described in any one of claims 1 to 3, the opening of the valve is adjusted so that the pressure downstream of the valve is 60 to 95 percent of the pressure of the raw material compound vaporized in the steam generating apparatus. Claim 5 delete

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