Patent Application
20250162926
The present disclosure relates to an optical fiber preform production method. The present application claims priority to Japanese Patent Application No. 2022-031021 filed on Mar. 1, 2022, the content of which is incorporated herein by reference in its entirety.
Patent Literature 1 discloses an optical fiber preform production method that includes a step of inserting a core material into a hole part provided in a cladding material, a step of inserting blocks into glass pipes connected to opposing ends of the cladding material to dispose and fix the core material between the blocks, and a step of integrating the core material and the cladding material by heating.
[Patent Literature 1] Japanese Unexamined Patent Publication No. 2011-168464
An optical fiber preform production method according to an aspect of the present disclosure is performed using a cladding material having a first end and a second end and being provided with a first hole, a first glass block having a first end and a second end and being provided with a second hole, and a first glass pipe including a first portion connected to the first end of the glass block, the method including: connecting the first portion of the first glass pipe to the first end of the cladding material; after the connecting, introducing a gas into the first hole through the first glass pipe and the second hole, and gas phase processing an inner surface of the first hole; after the gas phase processing, inserting a core material from the second end of the cladding material into the first hole until a tip end of the core material abuts against the first glass block; and after the inserting, integrating the cladding material and the core material by heating.
In the optical fiber preform production method above, there is a clearance between a block and a glass pipe, so that rotating a cladding material about an axial direction during the production causes the block made of glass to rotate inside the glass pipe. Glass chips are generated by the block being worn or chipped inside the glass pipe. The glass chips may be carried by a process gas and enter the interface between a core material and the cladding material to be a cause of reduction in the quality of the optical fiber.
It is an object of the present disclosure to provide an optical fiber preform production method that is capable of suppressing reduction in the quality of an optical fiber.
The present disclosure is capable of providing an optical fiber preform production method that is capable of suppressing reduction in the quality of an optical fiber.
Embodiments of the present disclosure will first be listed and described. An optical fiber preform production method according to an aspect of the present disclosure is performed using a cladding material having a first end and a second end and being provided with a first hole, a first glass block having a first end and a second end and being provided with a second hole, and a first glass pipe including a first portion connected to the first end of the glass block, the method including: connecting the first portion of the first glass pipe to the first end of the cladding material; after the connecting, introducing a gas into the first hole through the first glass pipe and the second hole, and gas phase processing an inner surface of the first hole; after the gas phase processing, inserting a core material from the second end of the cladding material into the first hole until a tip end of the core material abuts against the first glass block; and after the inserting, integrating the cladding material and the core material by heating.
In the optical fiber preform production method above, the glass block is integrated to the first glass pipe, so that the first glass pipe and the glass block are in contact with each other, and the generation of glass chips is suppressed. This prevents glass chips from being carried by the gas and entering the first hole during the gas phase process. As a result, glass chips are prevented from entering the interface between the cladding material and the core material and reducing the quality of the optical fiber.
The first glass pipe may further include a second portion connected to the second end of the first glass block. In this case, the flow of gas is facilitated in the gas phase process since the first glass block and the cladding material are not directly connected together.
The cladding material may be provided with a plurality of the first holes. In this case, the effect of facilitating the flow of gas in the gas phase process is pronounced.
The core material may include a main body part to be inserted into the first hole, and a dummy part connected to the main body part, and to be inserted into the first portion of the first glass pipe. In this case, the dummy part is an ineffective part that does not become a Core portion, so that, for example, using waste material for the dummy part enables efficient use of materials.
In the connecting, the first glass pipe may be connected such that at least a portion of the first hole does not overlap the second hole when viewed in an axial direction of the cladding material. In this case, a configuration in which the core material abuts against the first glass block can be achieved.
A hole size of the first hole may be greater than a hole size of the second hole. In this case, the configuration in which the core material abuts against the first glass block can be easily achieved.
The optical fiber preform production method above may further include: before the gas phase processing, connecting a second glass pipe to a second end of the cladding material; and after the inserting and before the integrating, inserting a second glass block inside the second glass pipe, and fixing the second glass block to a position abutting against a rear end of the core material. In this case, both ends of the core material can be fixed, so that positional misalignment of the core material is suppressed.
The fixing may be performed using a tubular glass jig disposed inside the second glass pipe and provided with a third hole, and a glass rod inserted through the third hole. In this case, the glass jig can suppress vibration of the glass rod inside the second glass pipe.
Specific examples of the optical fiber preform production method of the present disclosure will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. Same reference signs are given to the same elements in the description of the drawings, and redundant description will be omitted.
The plurality of Core portions 2 extend along the central axis of the optical fiber preform 1. The plurality of Core portions 2 are disposed at positions that are rotationally symmetric with respect to the central axis in a cross-section orthogonal to the central axis. The plurality of Core portions 2 have the same circular cross-sectional shape. Each Core portion 2 has a diameter of, for example, from 6 μm to 12 μm. The Cladding portion 3 surrounds the plurality of Core portions 2. The Cladding portion 3 has a diameter of, for example, from 124 μm to 126μm.
A refractive index of the Core portion 2 is higher than a refractive index of the Cladding portion 3. The Core portion 2 and the Cladding portion 3 are made of a silica-based glass material. The Core portion 2 and the Cladding portion 3 include silica glass as the main component, and include a dopant for adjusting the refractive index.
The step S10 includes a step S11 of drilling the holes 14 in the first glass block 13, a step S12 of connecting the first glass block 13 and the first portion 11 together, and a step S13 of connecting the first glass block 13 and the second portion 12 together. In the step S10, the first glass pipe 10 to which the first glass block 13 is integrated is prepared by the step S11 to the step S13 being performed in that order. However, the step S12 may be performed after the step S13, or simultaneously with the step S13.
In the step S11, one or a plurality of the holes 14 are formed in the cylindrical first glass block 13, for example, by a drill. In the step S12, a glass pipe to be the first portion 11 is melted and connected to the first end 13a of the first glass block 13. In the step S13, a glass pipe to be the second portion 12 is melted and connected to the second end 13b of the first glass block 13.
The first portion 11 of the first glass pipe 10 is melted and connected to the first end 30a so as to surround a plurality of holes 31 when viewed in an axial direction of the cladding material 30. The first portion 11 is connected to the first end 30a to be coaxial with the cladding material 30. The first portion 11 is coaxial with the first glass block 13 and the second portion 12, so that the cladding material 30 is coaxial with the entire first glass pipe 10 as well as with the first glass block 13.
In the step S20, the first glass pipe 10 is connected such that at least a portion of each of the holes 31 does not overlap the holes 14 when viewed in the axial direction of the cladding material 30. If the entirety of each of the holes 31 is disposed inside the holes 14 when viewed in the axial direction of the cladding material 30, the core material 40 may enter the holes 14 in the steps described further below. Hence, the first glass pipe 10 is connected such that the entirety of each of the holes 31 is not disposed inside the holes 14. In this embodiment, the entirety of each of the holes 31 does not overlap the holes 14 when viewed in the axial direction of the cladding material 30. That is, the holes 14 and the holes 31 do not overlap each other, but are separated.
In the step S30, the second glass pipe 20 is melted and connected to a second end 30b of the cladding material 30. The second glass pipe 20 is a glass pipe having a circular cross-sectional shape as illustrated in
The step S40 includes a step S41 of performing an etching process, a step S42 of inserting the core material 40, a step S43 of fixing a second glass block 50 (see
In the step S41, a gas is introduced into the holes 31 of the cladding material 30 through the first glass pipe 10 and the holes 14 of the first glass block 13 to etch (gas phase processing) inner surfaces of the holes 31. The etching process is performed, for example, while rotating the cladding material 30 about the axial direction and heating an outer peripheral surface of the cladding material 30 by an external heat source. The etching process removes impurities on the inner surfaces of the holes 31, and smooths the inner surfaces of the holes 31.
The gas introduced into the holes 31 is, for example, an etching gas such as SF6. The gas is supplied from the second portion 12 of the first glass pipe 10, flows through the second portion 12, the holes 14 of the first glass block 13, and the first portion 11 in order, and is introduced into the holes 31 of the cladding material 30. After flowing through the holes 31, the gas is discharged via the second glass pipe 20. The first glass pipe 10 side is an upstream side of the gas, and the second glass pipe 20 side is a downstream side of the gas with respect to the holes 31.
A joint (not shown) for connecting the second portion 12 to a supply system of the gas is attached to an end part of the second portion 12. A joint 63 (see
The dummy part 42 includes the tip end 40a, and is connected to the first portion 43 of the main body part 41. The main body part 41 and the dummy part 42 are melted and connected to be coaxial with each other. A length L1 of the dummy part 42 in the axial direction is set according to a length L2 of the first portion 11 of the first glass pipe 10 in the axial direction. The length L1 is set, for example, to be equal to the length L2. When the step S42 is completed, the first portion 43 is disposed inside the hole 31. The second portion 44 of the main body part 41 is disposed inside the second glass pipe 20. The dummy part 42 is disposed inside the first portion 11. The main body part 41 is required to have the same composition as the Core portion 2 since it includes the effective part, but the dummy part 42 may have a different composition from the Core portion 2 since it is formed only of the ineffective part.
As illustrated in
As illustrated in
In the step S43, for example, the second glass block 50 is first inserted inside the second glass pipe 20, and is pushed into the position abutting against the rear end 40b of the core material 40. The glass jig 60 and the glass rod 62 are then inserted inside the second glass pipe 20. The glass jig 60 is inserted to a substantially central position of the second glass pipe 20 in the axial direction. The glass rod 62 is inserted through the hole 61 in advance, and is then inserted inside the second glass pipe 20 together with the glass jig 60 with the glass jig 60 mounted thereto. The glass rod 62 is disposed such that a tip end 62a thereof abuts against the second glass block 50. That is, the second glass block 50 is pressed by the glass rod 62 with the glass jig 60 mounted thereto.
Finally, the joint 63 is attached to the end part of the second glass pipe 20. The joint 63 is made, for example, of a heat-resistant resin such as Teflon (registered trade mark), and covers the end part of the second glass pipe 20. The joint 63 abuts against a rear end 62b of the glass rod 62, and suppresses the movement of the glass rod 62 in the axial direction. This also suppresses the movement of the second glass block 50 in the axial direction. That is, the second glass block 50 is fixed to the position abutting against the rear end 40b of the core material 40. Consequently, the core material 40 is fixed between the first glass block 13 and the second glass block 50. It is required that the lengths of the core materials 40 are equal to one another to securely fix all the core materials 40.
In the step S44, a gas is introduced into the holes 31 of the cladding material 30 through the first glass pipe 10 and the holes 14 of the first glass block 13 to bake (gas phase processing) the inner surfaces of the holes 31. Similarly to the etching process, the baking process is performed, for example, while rotating the cladding material 30 about the axial direction and heating the outer peripheral surface of the cladding material 30 by an external heat source. The baking process is performed with the second portion 12 of the first glass pipe 10 and the second glass pipe 20 being rotatably held by the holding part of the glass lathe (not shown).
The baking process removes impurities on the inner surfaces of the holes 31, and smooths the inner surfaces of the holes 31. The gas introduced into the holes 31 is, for example, a cleaning gas (i.e., baking gas) such as chlorine or oxygen. The gas is supplied from the second portion 12 of the first glass pipe 10, flows through the second portion 12, the holes 14 of the first glass block 13, and the first portion 11 in order, and is introduced into the holes 31 of the cladding material 30. After flowing through the holes 31, the gas is discharged via the second glass pipe 20.
The tearing part 70 also functions as a sealing part for sealing one ends of the holes 31. The heating and integrating process is performed while drawing a vacuum inside the holes 31 from the first glass pipe 10 side. It is thus necessary to seal the holes 31 on the second glass pipe 20 side as a preprocess for the heating and integrating process. A glass rod 71 is then melted and connected to the tearing part 70 as illustrated in
In the step S50, the cladding material 30 and the core materials 40 are integrated by heating while drawing a vacuum inside the holes 31 from the first glass pipe 10 side. Similarly to the etching process and the baking process, the heating and integrating process is performed, for example, while rotating the cladding material 30 about the axial direction and heating the outer peripheral surface of the cladding material 30 by an external heat source. The heating and integrating process is performed with the second portion 12 of the first glass pipe 10 and the glass rod 71 being rotatably held by the holding part of the glass lathe (not shown). Since the positions of the core materials 40 in the axial direction are fixed, the core materials 40 can be heated and integrated with the cladding material 30 simultaneously while being prevented from stretching and thinning by the heating.
As described above, in the method for producing the optical fiber preform 1 according to the embodiment, the first glass block 13 is integrated to the first glass pipe 10, so that the first glass pipe 10 and the first glass block 13 are in contact with each other, and the generation of glass chips is suppressed. This prevents glass chips from being carried by the gas and entering the holes 31 in the etching process of the step S41 and the baking process of the step S44. As a result, glass chips are prevented from entering the interface between the cladding material 30 and the core materials 40 and reducing the quality of the optical fiber.
The second glass block 50 is not integrated to the second glass pipe 20. This is because the first glass pipe 10 side is the upstream side of the gas, and the second glass pipe 20 side is the downstream side of the gas with respect to the holes 31. Even if the second glass pipe 20 and the second glass block 50 come into contact with each other and glass chips are generated, the glass chips will be carried to the downstream side of the gas. Consequently, the glass chips will be prevented from entering the holes 31.
The first glass pipe 10 includes the first portion 11 that is connected to the first end 30a of the cladding material 30. The first portion 11 is disposed between the first glass block 13 and the cladding material 30, so that the first glass block 13 and the cladding material 30 are not directly connected together. This facilitates the flow of gas during the etching process of the step S41 and the baking process of the step S44. The smooth flow of gas enables the inner surfaces of the holes 31 to be evenly etched.
In the step S20, it is only required that the first portion 11 and the cladding material 30 are connected together, so that the melting and connecting is facilitated compared to a case in which the first glass block 13 and the cladding material 30 are directly connected together.
In the production method disclosed in Patent Literature 1, the glass block is fixed by heating and reducing the diameter of a portion of the glass pipe, so that it is necessary to cut off the heated and diameter-reduced portion each time to reuse the glass pipe. This tends to increase the consumption of glass pipes. Furthermore, the glass block cannot be reused in a case in which the glass pipe is heated and the diameter is reduced at a position where the glass block is disposed. However, in the present embodiment, the first glass block 13 can be fixed without reducing the diameter of the first glass pipe 10. Consequently, cutting off only the end part of the first portion 11 connected to the cladding material 30 after the heating and integrating process of the step S50 enables the remainder of first glass pipe 10 and the first glass block 13 to be reused.
The core material 40 has the dummy part 42. The dummy part 42 is an ineffective part that does not become the Core portion 2, so that using waste material for the dummy part 42 enables efficient use of materials.
In the step S20, the cladding material 30 and the first glass pipe 10 are connected together such that at least a portion of the hole 31 does not overlap the hole 14 when viewed in the axial direction of the cladding material 30. This prevents the core material 40 from entering the hole 14, and makes it possible to achieve the configuration in which the core material 40 abuts against the first glass block 13.
The hole size of the hole 31 is greater than the hole size of the hole 14, so that at least a portion of the hole 31 does not overlap the hole 14 when viewed in the axial direction of the cladding material 30. The outer diameter of the core material 40 is only slightly smaller than the hole size of the hole 31, which further prevents the core material 40 from entering the hole 14, and makes it possible to easily achieve the configuration in which the core material 40 abuts against the first glass block 13. The hole size of the hole 14 is smaller than the outer diameter of the core material 40, which reliably prevents the core material 40 from entering the hole 14. This eliminates the need to adjust the connection angle (angle about the axial direction) between the cladding material 30 and the first glass pipe 10 in the step S20.
The tip end 40a of the core material 40 is fixed by the first glass block 13, and the rear end 40b of the core material 40 is fixed by the second glass block 50 in the step S43. Both ends of the core material 40 can thus be fixed, so that positional misalignment of the core material 40 in the axial direction is suppressed. The fixing of the core material 40 is also maintained during the tearing in the step S45.
The second glass block 50 is fixed to the position abutting against the rear end 40b of the core material 40 by the glass rod 62. Unlike the production method disclosed in Patent Literature 1, in the present embodiment, the second glass block 50 can be fixed without heating and reducing the diameter of the second glass pipe 20. Consequently, cutting off just the end part of the second glass block 50 after the tearing in the step 45 enables the remainder of the second glass pipe 20 and the second glass block 50 to be reused.
The step S43 is performed using not only the glass rod 62 that presses the second glass block 50, but also the glass jig 60 through which the glass rod 62 is inserted. The glass jig 60 suppresses the movement of the glass rod 62 in a direction orthogonal to the axial direction. In particular, the cladding material 30 is rotated about the axial direction during the baking process of the step S44 and the heating and integrating process of the step S50, so that the glass rod 62 tends to vibrate inside the second glass pipe 20. The glass jig 60 suppresses the vibration of the glass rod 62 inside the second glass pipe 20. This suppresses damages to the second glass pipe 20 by the vibrating glass rod 62.
Although the embodiments have been described, the present disclosure is not necessarily limited to the embodiments and variations described above, and various modifications are possible without departing from the gist thereof.
Although the optical fiber preform 1 produced by the production method according to the embodiment above is a multicore optical fiber preform, it may be a single core optical fiber preform. In this case, one hole 31 is provided in the cladding material 30.
The entirety of the core material 40 may be formed of the main body part 41 without the core material 40 including the dummy part 42.
The hole size of the holes 31 may be equal to or smaller than the hole size of the holes 14. In this case, the connection angle between the cladding material 30 and the first glass pipe 10 is adjusted in the step S20 such that at least a portion of each of the holes 31 does not overlap the holes 14 when viewed in the axial direction of the cladding material 30.
The embodiments and variations above may be combined as appropriate.
As is understood from the description of the embodiments and variations above, the present specification includes the disclosure of the aspects shown below.
An optical fiber preform production method including:
An optical fiber preform production method including:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-031021 | Mar 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/048383 | 12/27/2022 | WO |
