The present invention relates to a method for manufacturing a photonic band gap fiber preform, a method for manufacturing a photonic band gap fiber, a photonic band gap fiber preform, and a photonic band gap fiber that can be easily manufactured and can increase the wavelength range of light whose waves are guidable.
As one of optical fibers, a photonic band gap fiber is known. The photonic band gap fiber has a structure in which a core region is surrounded by a band gap region in a cladding, and is expected as an optical fiber that can realize low loss characteristics and low nonlinear optical characteristics. The photonic band gap fiber includes a hollow core photonic band gap fiber having a core region formed of holes and a band gap region that a large number of holes are periodically disposed around the hollow core region, and includes a solid core photonic band gap fiber having a solid core region filled with a glass body and a band gap region that high refractive index glass bodies are periodically disposed around the solid core region. In these photonic band gap fibers, the hollow core photonic band gap fiber is expected as an optical fiber that can realize super low nonlinear optical characteristics and super low loss characteristics in a wavelength range of 2 μm.
In Non Patent Literature 1 below, an example of a hollow core photonic band gap fiber like this is described. In this photonic band gap fiber, a band gap region is in a honeycomb shape formed with a large number of holes, and the holes are formed in which the holes are individually surrounded by columnar glass bodies disposed on the apexes of a hexagon and a plate glass body disposed so as to join adjacent columnar glass bodies to each other. Therefore, the shapes in the cross sections of the holes are nearly in a hexagonal shape. However, strictly speaking, the shape is a shape that the apexes of a hexagon are protruded in an arc shape into the hexagon. The photonic band gap fiber as decried above is generally manufactured using a stack-and-draw method. In the manufacture processes, the photonic band gap fiber is manufactured through processes in which a band gap capillary forming a part of a band gap region is disposed in a triangular lattice shape, and a band gap rod forming the other part of the band gap region is disposed in regions surrounded by three band gap capillaries. In other words, in the state in which the band gap capillaries and the band gap rods are disposed, the band gap capillaries are individually surrounded by six band gap rods. These band gap rods are the columnar glass bodies described above, and the band gap capillaries are the plate glass bodies described above. According to Non Patent Literature 1 described below, this photonic band gap fiber has the characteristics that the wavelength range of light whose waves are guidable can be increased as compared with a photonic band gap fiber that holes are surrounded by plate glass bodies and the hole shape is in a regular hexagonal shape.
Moreover, Non Patent Literature 2 mentioned below describes another example of a hollow core photonic band gap fiber. In this photonic band gap fiber, a large number of holes are formed in a band gap region, and the holes are formed in which the holes are individually surrounded by columnar glass bodies disposed on the apexes of a triangle and plate glass bodies disposed so as to join adjacent columnar glass bodies to each other. Therefore, although the holes are in a nearly triangular shape, strictly speaking, the holes are in a shape in which the apexes of a triangle are protruded in an arc shape into the triangle. Non Patent Literature 2 mentioned below describes a calculation result that this photonic band gap fiber can more increase the wavelength range of light whose waves are guidable than the photonic band gap fiber of Non Patent Literature 1 described above does.
In the photonic band gap fiber described in Non Patent Literature 2 mentioned above, the band gap region is formed of the columnar glass bodies disposed in a triangular lattice shape and the plate glass bodies joining the columnar glass bodies. However, it is very difficult to form a band gap region in this shape. In the case where a photonic band gap fiber is manufactured using at least a stack-and-draw method, it is not enabled to stably dispose band gap capillaries and band gap rods how the band gap capillaries and the band gap rods are disposed. Therefore, it is unknown whether this photonic band gap fiber can be actually manufactured.
On the other hand, in the photonic band gap fiber described in Patent Literature 1 above, in the case where the photonic band gap fiber is manufactured using a stack-and-draw method, the band gap capillaries and the band gap rods can be stably disposed, and the photonic band gap fiber can be actually manufactured. However, it is demanded to increase the wavelength range of light whose waves are guidable more than this photonic band gap fiber does.
Therefore, it is an object of the present invention to provide a method for manufacturing a photonic band gap fiber preform, a method for manufacturing a photonic band gap fiber, and a photonic band gap fiber preform that can realize a photonic band gap fiber that can be easily manufactured and can increase the wavelength range of light whose waves are guidable, and a photonic band gap fiber.
In order to achieve the object, a method for manufacturing a photonic band gap fiber preform according to the present invention is a method for manufacturing a photonic band gap fiber preform including: a preparation process in which a core capillary, a plurality of band gap capillaries, a plurality of band gap rods, and a cladding capillary are prepared; a disposition process in which the core capillary and the band gap capillaries are disposed in a hole of the cladding capillary in a manner that the plurality of the band gap capillaries is disposed in a triangular lattice shape to surround the core capillary and the band gap rods are disposed in a region surrounded by three of the band gap capillaries in a manner that the band gap capillaries are surrounded by three of the band gap rods at regular spacings; and an integration process in which a space in the hole of the cladding capillary is collapsed to integrate the cladding capillary, the plurality of the band gap capillaries, the plurality of the band gap rods, and the core capillary with one another. A photonic band gap fiber preform according to the present invention is manufactured through the processes.
Moreover, an aspect of a method for manufacturing a photonic band gap fiber according to the present invention is a method for manufacturing a photonic band gap fiber including a drawing process for drawing a photonic band gap fiber preform manufactured through the method for manufacturing a photonic band gap fiber preform. An aspect of a photonic band gap fiber according to the present invention is manufactured through the drawing process.
Alternatively, another aspect of a method for manufacturing a photonic band gap fiber according to the present invention is a method for manufacturing a photonic band gap fiber including: a preparation process in which a core capillary, a plurality of band gap capillaries, a plurality of band gap rods, and a cladding capillary are prepared; a disposition process in which the core capillary and the band gap capillaries are disposed in a hole of the cladding capillary in a manner that the plurality of the band gap capillaries is disposed in a triangular lattice shape to surround the core capillary and the band gap rods are disposed in a region surrounded by three of the band gap capillaries in a manner that the band gap capillaries are surrounded by three of the band gap rods at regular spacings; and a drawing process in which drawing is performed while collapsing a space in the hole of the cladding capillary and integrating the cladding capillary, the plurality of the band gap capillaries, the plurality of the band gap rods, and the core capillary with one another. Another aspect of a photonic band gap fiber according to the present invention is manufactured through these processes.
The present inventors dedicatedly investigated the configuration of a photonic band gap fiber that can increase the wavelength range of light whose waves are guidable more than the photonic band gap fiber described in Non Patent Literature 1 does and can be easily manufactured. Consequently, the present inventors were enabled to obtain such a result that when a columnar glass body is disposed on alternate three apexes of a hexagon surrounding a hole, a plate glass body is disposed on a line connecting the columnar glass body to the other three alternate apexes of the hexagon and thus the columnar glass bodies are disposed in a triangular lattice shape, unlike the photonic band gap fiber described in Non Patent Literature 1 in which a columnar glass body is disposed on the apexes of a hexagon surrounding a hole in a band gap region, the wavelength range of light whose waves are guidable can be increased more than the photonic band gap fiber described in Non Patent Literature 1 does. Moreover, such a conclusion was reached that with this configuration, a photonic band gap fiber can be stably manufactured using a stack-and-draw method. More specifically, in the manufacture processes of a photonic band gap fiber using a stack-and-draw method, a plurality of band gap capillaries for forming a band gap region is disposed in a triangular lattice shape, and a band gap rod is disposed in a region surrounded by three band gap capillaries. At this time, the band gap rod is disposed only one of the regions adjacent to each other, so that the band gap capillary is supported and surrounded by three band gap rods at regular spacings, and the band gap rod is supported and surrounded by three band gap capillaries at regular spacings. In this manner, the band gap capillaries and the band gap rods are supported on one another, and are stabilized. Therefore, the photonic band gap fiber can be stably manufactured using a stack-and-draw method.
Therefore, according to the photonic band gap fiber preform manufactured by the method for manufacturing a photonic band gap fiber preform as described above and the photonic band gap fiber using the same, it is possible to realize a photonic band gap fiber that can be easily manufactured and can increase the wavelength range of light whose waves are guidable, and a photonic band gap fiber manufactured by drawing the photonic band gap fiber obtained not through a preform can be a similar photonic band gap fiber as well.
Moreover, in the method for manufacturing a photonic band gap fiber preform, the photonic band gap fiber preform manufactured through the method, the method for manufacturing a photonic band gap fiber, and the photonic band gap fiber manufactured through the method, the plurality of the band gap capillaries is preferably closely packed and disposed.
A plurality of the band gap capillaries is closely packed and disposed, so that a band gap capillary is surrounded by six band gap capillaries, and the adjacent band gap capillaries are supported on each other. Therefore, in the manufacture processes of the photonic band gap fiber preform and the photonic band gap fiber, the band gap capillaries and the band gap rods can be further stabilized.
Furthermore, in the method for manufacturing a photonic band gap fiber preform, the photonic band gap fiber preform manufactured through the method, the method for manufacturing a photonic band gap fiber, and the photonic band gap fiber manufactured through the method, a radius of the band gap rod is preferably greater than a wall thickness of the band gap capillary.
In addition, still another aspect of a photonic band gap fiber according to the present invention is a photonic band gap fiber including: a hollow core region; and a band gap region in a honeycomb shape surrounding the core region and having a plurality of holes formed in a glass body. In the photonic band gap fiber, the hole of the band gap region is surrounded by a columnar glass body disposed on three alternate apexes of a hexagon and a plate glass body disposed to join the columnar glass body to other three apexes of the hexagon; and the columnar glass body is disposed in a triangular lattice shape.
A photonic band gap fiber like this can be easily manufactured as described above, and can increase the wavelength range of light whose waves are guidable more than the photonic band gap fiber mentioned in Non Patent Literature 1 does as described above.
As described above, according to the present invention, there are provided a method for manufacturing a photonic band gap fiber preform, a method for manufacturing a photonic band gap fiber, and a photonic band gap fiber preform that can realize a photonic band gap fiber that can be easily manufactured and can increase the wavelength range of light whose waves are guidable, and a photonic band gap fiber.
In the following, a method for manufacturing a photonic band gap fiber preform, a method for manufacturing a photonic band gap fiber, a photonic band gap fiber preform, and a photonic band gap fiber according to the present invention will be described in detail with reference to the drawings. It is noted that for easy understanding, the scales in the drawings are sometimes different from the scales described in the following description.
A hole is formed in the center of the photonic band gap fiber 1, and the hole is the core region 10.
Moreover, the cladding 20 is formed of a glass body 22. A large number of holes 21 are formed in the region surrounding the core region 10 of the cladding 20. The region in which a large number of the holes 21 are formed is a band gap region 27. No hole is formed in the region surrounding the band gap region 27, and the region is a jacket region 28.
Moreover, three plate glass bodies 26 are radially connected to the columnar glass bodies 25 individually. The columnar glass bodies 25 are disposed in a triangular lattice shape, and the periphery of the plate glass body 26 connected to the columnar glass body 25 is joined to the periphery of the plate glass body 26 connected to the other columnar glass body 25. Therefore, a single plate glass body separates two holes 21 adjacent to each other, and a single columnar glass body 25 separates three holes 21 adjacent to one another. Thus, a large number of the holes 21 whose cross sectional shape is in a nearly hexagon are formed in such a manner that the hole 21 is surrounded by six holes through the columnar glass bodies 25 and the plate glass bodies 26, and the band gap region 27 is in a honeycomb shape.
The first buffer layer 31 that covers the cladding 20 and the second buffer layer 32 that covers the first buffer layer 31 are formed of resins different from each other, for example.
In this photonic band gap fiber 1, the wavelength of light propagated through the core region 10 is determined by the pitch and the like between the holes 21 in the band gap region 27. In accordance with the photonic band gap fiber 1 according to the embodiment, the wavelength range of light propagated through the core region 10 can be increased as compared with the case where the columnar glass body 25 is not disposed and the holes are formed of only the plate glass bodies 26.
In the following, the wavelength range of light propagated through the core region of the photonic band gap fiber will be described.
It is known that the normalized band W is changed depending on a ratio d/Λ of a diameter d of the holes to an inter-center pitch Λ between the holes adjacent to each other through the plate glass body. Generally, the normalized band W is increased as the ratio d/Λ is increased. When the ratio d/Λ takes one, the glass body separating the holes from each other is gone, and it is not enabled to maintain the physical shape as a photonic band gap fiber. In the case where the range of the ratio d/Λ is in a range of 0.95 to 0.97, both inclusive, in a typical photonic band gap fiber, the normalized band W ranges from 10% to 20%, both inclusive. Meanwhile, the transmission band width BW takes a wavelength range of 150 to 200 nm, both inclusive, in the case where a communication wavelength range of a 1,550 nm band is covered. Therefore, an increase in the transmission band width BW can increase the wavelength range of light usable for communications as well as it is expected that this increase expands the applications of optical fibers for femto second pulse delivery and optical fibers for measurement.
The normalized band W will be described as the band gap region of the photonic band gap fiber according to the present invention is compared with band gap regions different from the present invention.
Moreover, in the simulation of the photonic band gap fiber according to the embodiment, the hexagon HEX illustrated in
As illustrated in
Here, a table below is the relationship among the ratio d/Λ, the normalized band W, the normalized columnar glass body radius r/Λ, and the transmission band width BW of the photonic band gap fiber 1 according to the present invention. It is noted that r defines the radius of the columnar glass body. The normalized columnar glass body radius r/Λ expresses a value that the radius of the columnar glass body is divided by the inter-center pitch A of the holes. The normalized frequency expresses a value at a wavelength of 1,550 nm. As shown in the table below, in accordance with the photonic band gap fiber 1 according to the present invention, it is possible to realize the transmission band width BW exceeding 400 nm even in the case where the ratio d/Λ is 0.95, and it is possible to realize the transmission band width BW exceeding 850 nm when the ratio d/Λ can be increased to 0.99.
Next, a method for manufacturing the photonic band gap fiber 1 will be described.
<Preparation Process P1>
First, a core capillary, a plurality of band gap capillaries, a plurality of band gap rods, and a cladding capillary are prepared.
The core capillary is formed of a glass body, and in a cylindrical shape. Moreover, a plurality of the band gap capillaries is formed of a glass body, and in a cylindrical shape having the same wall thickness. The band gap capillaries are prepared in the same number as the number of the holes 21 of the photonic band gap fiber 1 in
<Disposition Process P2>
Next, the core capillary, a plurality of the band gap capillaries, and a plurality of the band gap rods are disposed in the through hole of the cladding capillary.
As illustrated in
In this state, the band gap capillaries 26c are individually supported on three band gap rods 25r, and the motion is limited. The band gap rods 25r are individually supported on three band gap capillaries 26c, and the motion is limited. More specifically, in the embodiment, since the band gap capillaries 26c are closely packed and disposed as described above, the adjacent band gap capillaries 26c are supported on each other, and the motion of the band gap capillaries 26c is further limited. Since the motion of the band gap capillaries 26c and the motion of the band gap rods 25c are limited in this manner, the motion of the core capillary is also limited. As a result, the core capillary 10c, the band gap capillaries 26c, and the band gap rods 25c are stabilized.
It is noted that although not illustrated in the drawing specifically, it may be fine that another glass rod is disposed in a space other than a space between the band gap capillaries 26c, such as a space between the cladding capillary 28c and the band gap capillary 26c and a space between the core capillary 10c and the band gap capillary 26c.
<Integration Process P3>
Next, the space in the inside of the through hole 28h of the cladding capillary 28c is collapsed, and the cladding capillary 28c, a plurality of the band gap capillaries 26c, a plurality of the band gap rods 25r, and the core capillary 10c are integrated with one another. In the process, in order not to collapse the holes of the band gap capillaries 26c and the hole of the core capillary 10c, a predetermined pressure is applied to the holes of the band gap capillaries 26c and the hole of the core capillary 10c, and spaces other than the holes are vacuumed. The entire cladding capillary 28c is then heated, and the space in the inside of the through hole 28h is collapsed.
In this collapsing, the hole 10h of the core capillary 10c is turned into a hollow core region 10p of a photonic band gap fiber preform 1P corresponding to the core region 10 of the photonic band gap fiber 1. Moreover, the core capillary 10c forms the region on the innermost side of a cladding 20p of the photonic band gap fiber preform 1P corresponding to the region on the innermost side of the cladding 20 of the photonic band gap fiber 1. Furthermore, a part of the band gap capillary 26c is turned into a plate glass body 26p of the photonic band gap fiber preform 1P corresponding to the plate glass body 26 of the photonic band gap fiber 1, and the other part is turned into a part of the outer circumferential side of a columnar glass body 25p of the photonic band gap fiber preform 1P corresponding to a part of the outer circumferential side of the columnar glass body 25 of the photonic band gap fiber 1. In addition, the band gap rod 25r is turned into a part of the center side of the columnar glass body 25p of the photonic band gap fiber preform 1P corresponding to a part of the center side of the columnar glass body 25 of the photonic band gap fiber 1. In other words, the columnar glass body 25p of the photonic band gap fiber preform 1P corresponding to the columnar glass body 25 of the photonic band gap fiber 1 is configured of a part of the band gap rod 25r and a part of the band gap capillary 26c. The space in the inside of the through hole 28h of the cladding capillary 28c is then collapsed, a plurality of the band gap capillaries 26c disposed in a triangular lattice shape is deformed, holes 21h of the band gap capillaries 26c have a shape in which three alternate apexes of the apexes of a hexagon are protruded in an arc shape into the inner side of the hexagon, and the holes 21h are turned into holes 21p of the photonic band gap fiber preform 1P corresponding to the holes 21 of the photonic band gap fiber 1. Thus, a band gap region 27p of the photonic band gap fiber preform 1P is formed, which corresponds to the band gap region 27 of the photonic band gap fiber 1. Moreover, the cladding capillary 28c is turned into a jacket region 28p of the photonic band gap fiber preform 1P corresponding to the jacket region 28 of the photonic band gap fiber 1.
In this manner, as illustrated in
<Drawing Process P4>
First, as a preparation step for performing the drawing process P4, the photonic band gap fiber preform 1P manufactured through the preparation process P1 to the integration process P3 is disposed on a pulling furnace 110. Heat is then produced from a heating unit 111 of the pulling furnace 110 to heat the photonic band gap fiber preform 1P while applying a predetermined pressure to the hollow core region 10p and the holes 21p of the photonic band gap fiber preform 1P. In this heating, the lower end of the photonic band gap fiber preform 1P is heated at a temperature of 2,000° C., for example, and in a molten state. Glass is then melted from the photonic band gap fiber preform 1P, and glass is drawn. The drawn glass in the molten state is solidified soon after coming out of the pulling furnace 110, the hollow core region 10p of the photonic band gap fiber preform 1P is turned into the core region 10 of the photonic band gap fiber, the band gap region 27p of the photonic band gap fiber preform 1P is turned into the band gap region 27 of the photonic band gap fiber 1, and the jacket region 28p of the photonic band gap fiber preform 1P is turned into the jacket region 28 of the photonic band gap fiber 1. In this manner, a photonic band gap fiber is formed in the state in which the photonic band gap fiber is not covered with the first buffer layer 31 and the second buffer layer 32. After that, this photonic band gap fiber is passed through a cooling device 120, and is cooled to an appropriate temperature. When the photonic band gap fiber is entered to the cooling device 120, the temperature of the photonic band gap fiber is about a temperature of 1,800° C., for example, and when the photonic band gap fiber comes out of the cooling device 120, the temperature of the photonic band gap fiber is reached at temperatures from 40 to 50° C., for example.
Subsequently, the photonic band gap fiber is passed through a coating device 131 containing an ultraviolet curable resin to be the first buffer layer 31, and covered with this ultraviolet curable resin. The photonic band gap fiber is further passed through an ultraviolet application device 132, ultraviolet rays are applied to cure the ultraviolet curable resin, and the first buffer layer 31 is formed. Subsequently, the photonic band gap fiber covered with the first buffer layer 31 is passed through a coating device 133 containing an ultraviolet curable resin to be the second buffer layer 32, and covered with this ultraviolet curable resin. The photonic band gap fiber is further passed through an ultraviolet application device 134, ultraviolet rays are applied to cure the ultraviolet curable resin, the second buffer layer 32 is formed, and the photonic band gap fiber 1 illustrated in
The direction of the photonic band gap fiber 1 is then changed by a turn pulley 141, and the photonic band gap fiber 1 is wound on a reel 142.
In the method for manufacturing the photonic band gap fiber preform 1P and the method for manufacturing the photonic band gap fiber 1 according to the embodiment, a photonic band gap fiber can be stably manufactured using a stack-and-draw method. More specifically, in the manufacture processes, a plurality of the band gap capillaries 26c disposed to form the band gap region 27p of the photonic band gap fiber preform 1P is supported as the band gap capillaries 26c are surrounded by three band gap rods 25r, and the band gap rod 25r is supported as the band gap rod 25r is surrounded by three band gap capillaries 26c. In this manner, the band gap capillaries 26c and the band gap rods 25r are supported on each other and stabilized. Therefore, the photonic band gap fiber can be stably manufactured using a stack-and-draw method. Thus, according to the manufacturing method as described above, it is possible to easily manufacture the photonic band gap fiber 1 that can increase the wavelength range of light whose waves are guidable.
Next, another method for manufacturing the photonic band gap fiber 1 will be described.
First, similarly to the method for manufacturing the photonic band gap fiber 1 described above, the preparation process P1 and the disposition process P2 are performed. Subsequently, as illustrated in
In this example, in a preparation step for performing the drawing process, jigs are mounted on the inside of the through hole 28h and the cladding capillary 28c so as not to displace the core capillary 10c, a plurality of the band gap capillaries 26c, and a plurality of the band gap rods 25r. The core capillary 10c, a plurality of the band gap capillaries 26c, and a plurality of the band gap rods 25r in the inside of the through hole 28h and the cladding capillary 28c mounted with the jigs are then disposed on the pulling furnace 110 illustrated in
In this processing, the hole of the core capillary 10c is turned into the core region 10 of the photonic band gap fiber, the core capillary 10c is turned into the region on the innermost side of the cladding 20 of the photonic band gap fiber, a part of the band gap capillary 26c is turned into the plate glass body 26 of the photonic band gap fiber, the other part is turned into a part of the outer circumferential side of the columnar glass body 25 of the photonic band gap fiber, the band gap rod 25r is turned into a part of the center side of the columnar glass body of the photonic band gap fiber, and the cladding capillary 18c is turned into the jacket region 28 of the photonic band gap fiber.
After that, the photonic band gap fiber is covered with the first buffer layer 31 and the second buffer layer 32 similarly to the first example, and the photonic band gap fiber 1 is wound on the reel 142 similarly to the first example.
Also according to the method for manufacturing the photonic band gap fiber 1 in this example, the disposition process is performed similarly to the first example, so that it is possible to easily manufacture the photonic band gap fiber 1 that can increase the wavelength range of light whose waves are guidable.
As described above, the present invention is described as the embodiment is taken as an example. However, the present invention is not limited to the embodiment.
For example, in the disposition process P2 of the method for manufacturing the photonic band gap fiber 1 according to the embodiment, the band gap capillaries 26 are closely packed and disposed. However, the present invention is not limited to this configuration. It may be fine that the band gap capillaries 26 are disposed in a triangular lattice shape in the state in which a space is provided between the band gap capillaries 26 adjacent to each other. In this case, the band gap rod 25r can be thickened, and a thick columnar glass body 25 can be formed as compared with the case where the band gap capillary 26 are closely packed and disposed.
As described above, according to the present invention, there are provided a method for manufacturing a photonic band gap fiber preform, a method for manufacturing a photonic band gap fiber, and a photonic band gap fiber preform that can realize a photonic band gap fiber that can be easily manufactured and can increase the wavelength range of light whose waves are guidable, and a photonic band gap fiber, and the use in technical fields such as optical communications is expected.
Number | Date | Country | Kind |
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2013-036428 | Feb 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2014/054557 | 2/25/2014 | WO | 00 |