JPS6186441A - Method and apparatus of porous base material for single polarization optical fiber - Google Patents

Abstract

PURPOSE:To obtain the titled base material having no unevenness in a crosssectional shape in case of manufacturing the base material by a gas phase axial accumulation method by using plural torchs for synthesizing the fine particles for cladding and feeding intermittently a dopant to one piece of torch selected therefrom in the specified interval. CONSTITUTION:The porous base material 29 for a core is formed by synthesizing the fine glass particles for the core with a torch 24 for synthesizing the glass particles for the core and sticking them on a tip of a starting material 22 which is moved in the axial direction while rotating. Furthermore the fine glass particles for cladding are stuck and accumulated around the base material 29 for the core with plural torchs 25, 26, 27 for synthesizing the fine glass particles for cladding and the porous base material 32 having the core part and the cladding part is formed. In this case, the raw material for a dopant changing the refractive index of glass is fed to one piece of torch 26 selected among the torchs in addition to the raw material for cladding and the feed of raw material for the dopant is intermittently performed in the specified interval while the starting material 22 is made with one revolution and thereby the titled base material is obtained.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a method and apparatus for manufacturing a porous preform for a single polarization optical fiber.

[Prior Art] One of the methods for manufacturing optical fiber preforms is vapor phase shafting. By using this method, the cross-sectional structure of the core part and cladding part is perfectly circular, making it applicable to the cladding part! g
A method of manufacturing a single-layer, single-polarized optical fiber has been proposed. For example, in Japanese Patent Application No. 56-5'8784,
As shown in FIG. 9 and FIG.
The porous base material 1 having a core and cladding is formed on the starting material 11 by the vapor phase shafting method, and after semi-sintering, the porous base material 1 is pulled up while rotating. A plurality of glass fine particle synthesis torches (hereinafter simply referred to as torches) 2 and 3 and 4 and 5 placed on the surface perpendicular to the core center axis of the base material 1 as they were pulled upward were charged with frit gas 5IC14, BBr3,G
eC14, TiCfL4 and flame forming gas H,,0
2, thereby providing porous glass for application? In Figure 0, a method is proposed in which a method is proposed in which the base material is jacketed by depositing and 8 and then sintering the entire base material into transparent glass.
8 is an exhaust part, and lO is a reaction vessel.

However, in this method, the plurality of torches 2 and 3 and 4 and 5 for forming the stress applying layers 7 and 8 are arranged so as to surround the porous base material 1 as shown in FIG. However, the exhaust section 8 cannot completely exhaust the excess fine particles that are not attached as the stress applying layers 7 and 8.

As a result, the stress imparting layer? and 8 cannot be formed stably and with good reproducibility.

In general, the exhaust method for gas-phase shafts according to the law is to install an exhaust pipe for one torch on an extension of the central axis of the torch.In other installation methods,
Not only will this cause some inconvenience, but there is also a risk of damage to the porous base material.

Furthermore, the cross-sectional shape of the porous base material manufactured by the method shown in FIGS. 8 and 8 is not circular as shown in FIG. , when jacketing a jacket tube 12 with a circular cross section and turning it into a fiber, air bubbles are trapped in a large portion of the space 13 between the base material and the jacket tube 12; As a result, the stress applying layers 7 and 8 are deformed, and furthermore, the outer diameter of the optical fiber is deformed.

Japanese Patent Application No. 55-811375 also proposes a method for manufacturing a porous preform for a single polarized optical fiber using the vapor phase shafting method. This method is basically the same as the method described above, except that the stress-applying layer is formed without semi-sintering the porous base material, whereas in the above method, the porous base material is not rotated after semi-sintering. The difference is that the stress-applying layer is formed while rotating the porous base material, and that glass-forming raw materials containing dopants are intermittently supplied when forming the stress-applying layer. .

However, like the above-mentioned method, this method also has the drawbacks of various problems associated with exhaust gas and problems caused by the uneven cross-sectional shape of the manufactured porous base material.

[Object of the Invention] Therefore, in order to solve the above-mentioned drawbacks, the object of the present invention is to ensure the evacuation and to prevent unevenness from occurring in the cross-sectional shape of the resulting porous base material, thereby producing a single-polarized optical fiber. An object of the present invention is to provide a method for manufacturing a base material for use in a plastic container.

Another object of the present invention is to provide a manufacturing apparatus capable of manufacturing a preform for a single polarized optical fiber by performing exhaust reliably and preventing irregularities in the cross-sectional shape of the obtained porous preform. There is a particular thing.

[Structure of the Invention] In order to achieve the above object, the manufacturing method of the present invention synthesizes core glass particles using a core glass particle synthesis torch, and converts the core glass particles into a starting material that moves in the axial direction while rotating. A porous base material for the core is grown in the axial direction of the starting material by adhering and depositing on the tip of the starting material, and glass fine particles for the cladding are synthesized using at least two or more glass fine particle synthesis torches for the cladding. In a method for producing a porous preform for a single mode optical fiber, the porous preform for a single mode optical fiber is formed by adhering and depositing around the porous preform to form a porous preform having a core portion and a ground portion. In addition to the glass raw material for cladding, a dopant raw material that changes the refractive index of quartz glass is supplied, and the dopant raw material is supplied intermittently at regular intervals during one rotation of the starting material. do.

The manufacturing apparatus of the present invention includes a reaction vessel equipped with an exhaust port, a starting material that can be moved up and down while rotating inside the reaction vessel, a drive device that rotates and drives the starting material up and down, and a It has a plurality of glass particle synthesis torches and a plurality of raw material supply systems that supply glass raw materials and flame-forming gas to the glass particle synthesis torches. In an apparatus for producing a porous preform for optical fibers, the glass particle synthesis torch includes at least a glass particle synthesis torch for the core and a glass particle synthesis torch for the cladding, and at least one of the glass particle synthesis torches for the cladding a supply system for supplying raw materials for glass and a supply system for supplying raw materials for dopant, and a device for detecting rotation of the starting materials,
The present invention is characterized in that the dopant raw material supply system is controlled by the detection device in relation to the rotation of the starting material, thereby controlling the supply of the dopant raw material.

In a second embodiment of the manufacturing apparatus of the present invention, a reaction container equipped with an exhaust port, a starting material that can be moved up and down while rotating within one reaction container, and a drive device that rotates and drives the starting material up and down,
It has a plurality of glass particle synthesis torches oriented in the axis through which the starting materials pass, and a plurality of raw material supply systems that supply glass raw materials and flame forming gas to the glass particle synthesis torches.
In an apparatus for manufacturing a porous optical fiber preform in which a porous preform for an optical fiber is deposited on a starting material in a reaction vessel, the glass particle synthesis torch includes at least a glass particle synthesis torch for the core and a glass particle synthesis torch for the cladding. at least one glass particle synthesis torch for cladding,
One is provided with a supply system for supplying glass raw materials for cladding and a supply system for supplying raw materials for dopant, and at least one exhaust port is provided so as to include an extension line of each central axis of the glass fine particle synthesis torch for cladding, and The present invention is characterized in that it includes a device for detecting the rotation of the starting material, and controls the dopant material supply system in relation to the rotation of the starting material by means of detection loading, thereby controlling the supply of the dopant material.

A plurality of torches for forming the core, cladding, and stress-applying layer are arranged in parallel to the central axis of the porous base material, and excess glass particles from all the torches are removed so as to include the extension line of each central axis of the cladding torch. At least one exhaust pipe is provided to exhaust the air.

Using such a manufacturing apparatus, only the dopant raw material is supplied among the glass forming raw material and the dopant raw material to the torch for forming the stress imparting layer.

A porous preform for a single-polarized optical fiber can be manufactured by intermittently supplying it a predetermined number of times during one rotation of the porous preform to be manufactured.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows the configuration of an embodiment of the manufacturing apparatus of the present invention, where 21 is a reaction vessel, 22 is a starting material, and 23 is a starting material 22 that is rotated and pulled upward in its axial direction. A core forming torch 24. The clad forming torch 25, the stress applying section, the clad forming torch 2B, and the clad forming torch 27 are connected to the reaction vessel 2.
1 from the bottom side, and are arranged side by side in this order so as to face the central axis of the starting material 22, that is, the pulling direction.

The blowing direction of the core torch 24 is inclined with respect to the central axis of the starting material 22, but the blowing directions of the torches 25 to 27 are approximately perpendicular to the central axis of the starting material 22.

An exhaust pipe 28 having an inner diameter that includes an extension of the central axis of each of these cladding torches 25 to 27 is disposed on the opposite side of the torches 25 to 27 with the starting material 22 in between. In addition,
Regarding exhaust, the exhaust of glass particles from the cladding torches 25 to 27 is the most important issue, so the exhaust pipe 28 as described above is provided.However, regarding the exhaust of glass particles from the core forming torch 24, Torch the exhaust pipe 24
On the extension of the central axis of l! Even if you do not place the starting material 2
They only need to be placed on opposite sides of the exhaust pipe 28, and sufficient exhaust can be achieved using the exhaust pipe 28 of this embodiment.

Here, a glass raw material for cladding is supplied to torches 25 and 27, and in addition to the glass raw material for cladding, torch 26 is supplied with 5i02 (quartz glass) for forming a stressed rod part.
It also supplies a dopant material that changes the refractive index of the material.

When the starting material 22 is gradually pulled up while being rotated by the driving device 23, the core forming glass particles blown out from the core forming torch 24 are attached to the starting material 22, and then the cladding forming torch 24 is attached to the starting material 22. The glass particles for forming a cladding blown out from the stress applying section 25 are attached, and the glass particles for forming a cladding and the dopant for forming a stress applying section blown out from the stress applying section and the torch 26 for forming the cladding are further attached, and the cladding is Glass particles for forming a cladding blown out from the forming torch 27 adhere to the glass particles.

As described above, the starting material 22 includes the core porous base material 28,
Cladding layer 30. A cladding layer 31 and a cladding layer 32 including stress applying portions are formed.

FIG. 2 schematically shows the cross section AA' in FIG. 1, and 33 is a stress applying layer formed in the cladding layer 31.

FIG. 3 shows the stress applying layer 3 in the apparatus shown in FIG.
An example of the configuration of the raw material system and the electrical system connected to the torch 28 to form the torch 34 and 35 is shown.
are glass and dopant raw material filling containers, respectively. In this example, one frit filling container 34 is shown as being provided, but in reality, other B
Br3, GeCl4゜TiC! ;A similar supply system is provided for gases such as L4. 36 and 37 are pipes for transporting the glass raw material and dopant raw material from these containers 34 and 35; 38 is a solenoid valve for intermittently supplying the dopant raw material from the pipe 37 to the torch 27;
9 is a pipe for discharging Dopan I and the raw material from the solenoid valve 38; 40 is a pipe for discharging the solenoid valve 38 in synchronization with the rotation of the starting material 22;
A tachometer 41 is a signal output device for operating the solenoid valve 38 based on the opening/closing signal.

First, the frit gas 5i is applied to the torch 24 shown in FIG.
Ci. A dopant material for increasing the refractive index and a flame forming gas H2,02 are supplied to synthesize glass fine particles, which are deposited on the tip of the rotating starting material 22 to form a porous base material 29 for the core. do. Here, as a dopant raw material to increase the refractive index, Ge0 pattern 4 + A pattern Cl!
3, POCJI 3.5bC13, GaCfL 3, etc. can be used. The porous base material 29 was pulled up in sequence according to the deposition rate of the glass particles, and then 5iCu was applied to the torch 25. and H2+02 gas are supplied to deposit 5i02 glass fine particles to be synthesized on the surface of the porous base material 28, thereby forming a cladding layer 30.

Furthermore, a cladding layer 31 including a stress-applying portion is formed on the surface of the cladding layer 30 using the torch 2B. At this time, the SiO material 4 is continuously supplied, but the dopant material forming the stress-applying portion is intermittently supplied. supply to. Dopant raw materials forming the stress applying portion include BBr3,
A single substance such as PCg 3 , P2O compound, or F compound, or a mixture with Ge0 compound 4 can be used.

Here, in order to supply the dopant raw material intermittently, as shown in FIG.
A solenoid valve 38 having a three-way valve structure is provided at 7 to open and close the solenoid valve 38.
The structure is such that when the torch 26 is open, the dopant raw material is supplied to the torch 26, and when the torch is closed, the dopant raw material is exhausted from the exhaust pipe 38.

In order to operate the solenoid valve 38, the rotation speed is detected by a tachometer 40 connected to the rotation and vertical drive device 23,
The output signal of the rotation speed is inputted to the output signal device 41 which operates the solenoid valve 38, and the output signal is set to be output an arbitrary number of times during one rotation of the porous base material.

For example, as shown in FIG. 4, the solenoid valve 38 is closed during 1200 rotations, and then opened during 60° rotation, and the output signal device 41 is configured to perform this operation continuously. By outputting a signal from , a cladding layer 31 having a pair of stress applying portions 33 disposed opposite to each other with respect to the center of the core porous base material 28 as shown in FIG. 5 is formed. Can be done. The numbers shown in Fig. 5 are rotation angles, and between 0° and 120°, the solenoid valve 38
Since the valve is closed, only 5i02 is deposited during this time, and since the solenoid valve is open for 3 days between 120° and 180°, 5iC12 and the dopant raw material are deposited. This dopant raw material is in the form of glass fine particles at the time it is deposited on the surface of the ground layer 30. Then 180°
Since the solenoid valve 38 is closed between ~300°, only 5102 is deposited, and between 3000° and 360°, the solenoid valve 38 is closed.
Since 5102 is open, this indicates that 5102 and the dopant material are deposited.

In the conventionally proposed method, as shown in FIG. In contrast to the unevenness of the cross-sectional shape after formation of the cladding layer and 8, in the present invention, the stress-applying portion can be formed in the cladding layer having a circular cross-sectional shape. Therefore, each step after manufacturing the transparent base material and converting it into an optical fiber can be processed in the same way as the conventionally developed base material for optical fibers having a circular core and a circular cladding. Problems such as deformation of the optical fiber cross section can be solved.

In the present invention, the second cladding layer 32 is formed by further depositing only 5i02 on the surface of the cladding layer 31 having the stress applying portion 33 using the torch 27. By this step, jacket processing is required in the conventional method, whereas jacket processing can be omitted in the present invention.

In this case, it is also possible to further provide a torch above the torch 27 in order to form the second cladding layer 32 having a sufficient thickness. In this case, it is preferable to further dispose another exhaust pipe above the exhaust pipe 28 to more fully exhaust the cladding glass particles.

Furthermore, regarding the exhaust of excess glass particles, which was a problem in the conventional method, in the present invention, as shown in FIGS. Since the device is configured such that exhaust pipes 28 are provided in front of each torch 25 to 27, which are arranged in parallel in the vertical direction, with the starting material 22 in between, it is possible to completely exhaust excess glass particles. It is possible to solve the problems of conventional methods, such as cracking of the porous base material.

Incidentally, the surplus glass particles for the core can be exhausted through the exhaust pipe 28 mentioned above, but for even more sufficient exhaustion, as shown in FIG. It is also possible to arrange an exhaust pipe 42.

In order to increase the cross-sectional area of the stress applying portion 33 formed in the present invention, the opening time of the solenoid valve 38 may be increased, or the raw material system shown in FIG. The stress applying portion 33 can be formed by the and torch 27 . In the former method, for example, the cross-sectional area of the stress applying section 33 can be increased by opening and closing the solenoid valve 38 every time the solenoid valve 38 rotates 90 degrees.
If the closing angle of 8 is less than 30', the donipant may be doped throughout the cladding layer 31 due to dopant diffusion, which is undesirable. The latter method is preferable.

The present invention will be explained in detail below using specific examples.

Example 1 In the apparatus shown in Fig. 1, the exhaust pressure on the exhaust pipe for 2 days was set to 8
mmH2O and 5i (414 to 70c) to the torch 24.
c/min. fabricated at a deposition rate. Note that the rotation speed of the starting material 22 is er
It was set as pm.

Next, apply 5jC1tl to torch 25 at 150cc/min.
H2 at 4.5 sentences/min, 02 at 8fL1 min, Ar at 1.2
．． The cladding layer 30 was formed on the surface of the porous core material 28 by supplying it at a rate of Il/min.

When the porous base material on which the cladding layer 30 is formed has grown to the front of the torch 26, the torch 28 is coated with 200% SiC.
cc/min, H2 at 8 m/min, O2 at 7 m/min, and Ar at a rate of 1.217 min, while BBr3 was supplied as a raw material for forming the stress applying part using a torch as shown in Fig. 3. 26. At this time, the solenoid valve 38 shown in FIG. 3 is closed while the porous base material rotates 120' as shown in FIG. 5. Open between 60° from 20° to 180°, closed between 180' and 300°, 30°
The opening was kept open from 0° to 360°, and this operation was repeated until the porous base material preparation was completed.

After forming the cladding layer 31 including the stress applying portion 33 with the torch 26, 200% of 5iCfL4 is applied to the torch 27.
A cladding layer 32 was formed on the surface of the cladding layer 31 by supplying ccZ, H2 at a rate of 8 sentences/min, 02 at a rate of 101/min, and Ar at a rate of 1.17 minutes.

The porous base material produced in this way was heated in an electric furnace.
It was dehydrated and made into transparent vitrification at a temperature of 500°C.

FIG. 7 shows the cross-sectional shape of the base material after transparent vitrification. 7th
As is clear from the figure, l pairs of stress applying layers 33 are formed around the core 28 in the circular cladding layer 43 made of 5i02.

On the other hand, in the base material manufactured by the conventional method shown in Fig. 10, although a stress-applying layer is formed, its cross-sectional shape is uneven, which causes the base material manufactured by the conventional method to become a fiber. This caused bubbles to form during the process.

In addition, in FIG. 10, two pairs of stress applying layers 7 and 8 with different components are provided, but even one pair as shown in FIG. 5 is sufficient for the role of stress applying layers. .

However, in the present invention, it is of course possible to provide two or more pairs of stress applying layers by appropriately determining the opening and closing of the electromagnetic valve 38.

When the base material with the cross-sectional shape shown in Fig. 7 was made into a fiber without jacketing and its loss characteristics were measured, it was found to be 0.3
dB/km (wavelength: 1.55 p, m), and Kukostalk was -35 dB/km (wavelength: 1.55 g, m), which was a good result.

[Effect] As explained above, in the present invention, a porous base material manufacturing apparatus is manufactured by arranging a plurality of torches for forming a core, a cladding, and a stress imparting layer in parallel with respect to the central axis of the porous base material. Using such a device, only the dopant raw material of the glass forming raw material and dopant raw material supplied to the cladding torch for forming the stress imparting layer is intermittently supplied a predetermined number of times during one revolution of the porous base material. Furthermore, if necessary, at least one exhaust pipe is provided on the extension line of each central axis of the torches for forming the cladding and the stress imparting layer to exhaust excess fine particles from all of these torches. It is also possible to produce a porous matrix for use in single polarization optical fibers. Therefore, according to the invention:
A porous base material containing at least one pair of stress-applying layers in a circular cladding part can be manufactured in a continuous process with the step of forming the porous base material for the core, which solves the problems of conventional methods. It is possible to improve residual air bubbles, deformation of the stress-applying layer, fiber outer diameter, etc. caused by the uneven cross-sectional shape of the porous base material.

Moreover, in the present invention, since it can be made into a fiber without performing jacket processing afterwards, there are advantages such as reduced loss and excellent manufacturing economy.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the configuration of an embodiment of the manufacturing apparatus of the present invention, Fig. 2 is a cross-sectional view taken along line A-A', and Fig. 3 is a line showing an example of the configuration of the raw material supply system and electrical system. Figure 4 is an explanatory diagram of the manufacturing method of the present invention; Figure 5 is a sectional view showing a porous base material formed by the present invention; Figure 6 is a schematic diagram showing another embodiment of the manufacturing apparatus of the present invention. , Fig. 7 is a cross-sectional view showing the cross-sectional structure of an optical fiber obtained by fiberizing the porous preform manufactured according to the present invention, and Fig. 8 is a conventional apparatus for manufacturing a single mode optical fiber having polarization characteristics. A schematic diagram of , and Figure 9 is a sectional view thereof. FIG. 10 is a sectional view showing the porous base material obtained thereby. 1... Semi-sintered porous base material, 2.3, 4.5... Glass particle synthesis torch for applying stress, S... Rotation 88. 7.8... Stress imparting layer, 3... Exhaust section, 10... Reaction container, 11... Starting material, 12... Jacket tube, 13... Space, 21... Reaction container . 22... Starting material, 23... Rotation and vertical drive device, 24... Core forming torch, 25.2? ... Torch for forming cladding, 26... Torch for stress applying part and cladding, 28... Exhaust pipe, 29... Porous base material for core, 30... Clad layer, 31... 32... Cladding layer, 33... Stress imparting layer, 34, 35... Glass raw material filling container. 3t (, 37... Piping for raw material transportation, 38... Solenoid valve, 38... Piping for exhausting dopant raw material, 40... Tachometer, 41... Output signal device, 42... Exhaust pipe , 43...Clad layer formed by torches 25-27.

Claims (1)

[Scope of Claims] 1) Glass fine particles for a core are synthesized using a torch for synthesizing glass fine particles for a core, and the glass fine particles for a core are deposited on the tip of a starting material that moves in the axial direction while rotating. A porous base material for the core is grown in the axial direction, glass fine particles for the cladding are synthesized using at least two glass fine particle synthesis torches for the cladding, and the glass fine particles for the cladding are grown around the porous base material for the core. In the method for manufacturing a porous preform for a single mode optical fiber, which forms a porous preform having a core portion and a cladding portion by adhering and depositing, a porous preform for the cladding is attached to at least one of the glass fine particle synthesis torches for the cladding. In addition to the glass raw material, a dopant raw material that changes the refractive index of quartz glass is supplied, and the dopant raw material is supplied intermittently at regular intervals during one rotation of the starting material. A method for manufacturing a porous base material for wave optical fiber. 2) A reaction vessel equipped with an exhaust port, a starting material that can be moved up and down while rotating within the reaction vessel, a drive device that rotates and drives the starting material up and down, and a starting material that is oriented along an axis through which the starting material passes. a plurality of glass particle synthesis torches, and a plurality of raw material supply systems that supply glass raw materials and flame forming gas to the glass particle synthesis torches; In the apparatus for manufacturing a porous preform for optical fibers, the glass particle synthesis torch includes at least a core glass particle synthesis torch and a cladding glass particle synthesis torch, and at least One is equipped with a supply system for the glass raw material for cladding and a supply system for supplying the dopant raw material, and a device for detecting the rotation of the starting material. 1. An apparatus for producing a porous preform for a single polarized optical fiber, characterized in that supply of a dopant raw material is controlled by controlling rotation. 3) a reaction vessel equipped with an exhaust port, a starting material that can move up and down while rotating within the reaction vessel, a drive device that rotates and drives the starting material up and down, and a starting material that is oriented along an axis through which the starting material passes. a plurality of glass particle synthesis torches, and a plurality of raw material supply systems that supply glass raw materials and flame forming gas to the glass particle synthesis torches; In the apparatus for manufacturing a porous preform for optical fibers, the glass particle synthesis torch includes at least a core glass particle synthesis torch and a cladding glass particle synthesis torch, and at least One is provided with a supply system for a glass raw material for cladding and a supply system for supplying a dopant raw material, and at least one exhaust port is arranged so as to include an extension line of each central axis of the glass fine particle synthesis torch for cladding, and a device for detecting rotation of the starting material, and controlling the dopant raw material supply system in relation to the rotation of the starting material by the detection device,
A manufacturing device for a porous preform for a single polarization optical fiber, characterized in that the supply of a dopant raw material is controlled.