KR101055312B1 - Photonic bandgap optical fiber and manufacturing method thereof - Google Patents

Abstract

The photonic bandgap optical fiber may include a core portion extending in one direction and one or more first tubes surrounding the core portion. The cross section of the core part in a direction perpendicular to the one direction is positioned on a plane formed by the first axis and the second axis, and the length of the first axis direction may be smaller than the length of the second axis direction. A method of manufacturing a photonic bandgap optical fiber includes arranging one or more first tubes to form a core portion surrounded by one or more first tubes, forming a base material from the one or more first tubes, and applying heat and pressure to the base material. It can be configured to withdraw the optical fiber. At this time, the temperature of one side of the base material may be smaller than the temperature of the other side.

Polarization retention, photonic band gap, base material, core, ellipse

Description

Photonic bandgap fiber and method for manufacturing the same

Embodiments of the present invention relate to a photonic bandgap optical fiber and a method for manufacturing the same, and more particularly, to a photonic bandgap optical fiber having a predetermined shape in a cross section of a core portion perpendicular to the longitudinal direction of the optical fiber and a method for manufacturing the same. It is about.

The photonic crystal optical fiber may include air holes that are periodically arranged and are constantly drilled in the longitudinal direction, which is the same direction as the direction in which light is guided in a general optical fiber.

Photonic bandgap optical fiber and waveguide mode photonic crystal optical fiber have been actively studied in the field of photonic crystal optical fiber. Both optical fibers may be manufactured by periodically stacking silica rods having air holes, and forming a preform shaped like a single silica cylinder, and then melting and drawing the optical fiber. The main difference between the two optical fibers is that the photonic bandgap optical fiber consists of air holes, whereas the waveguide mode photonic crystal optical fiber is filled with silica.

A photonic bandgap fiber can be created if the center region is made using a silica rod with air holes in the process of making the preform. In order to obtain a relatively high birefringence, a plurality of silica rods having different sizes of air holes may be used. On the other hand, in the case of using silica rods without air holes, a waveguide type photonic crystal optical fiber can be made. Multiple layers of silica rods without air holes can be fabricated to increase the size of the center core area.

Although there are no significant differences in terms of manufacturing two types of photonic crystal optical fibers, there are big differences in the operation characteristics, analysis methods, and applications of each optical fiber. Photonic bandgap optical fibers can guide light through the air layer, so there is little optical loss due to the waveguide medium. In addition, since the optical fiber itself may be made of pure silica alone, the optical fiber itself may have relatively stable operation characteristics against environmental changes (eg, temperature changes) than mixed optical fibers. Due to these characteristics, photonic bandgap fibers can be used mainly for the transmission of light from high-power lasers, or for devices requiring relatively high stability such as medical equipment. In addition, in the case of air, since the dispersion characteristics are uniform according to the wavelength, it is possible to apply to the ultra short pulse laser.

Recently, as the polarization maintaining optical fiber is widely used in the optical fiber system or the optical sensor market, the research on the polarization maintaining photonic bandgap optical fiber which has a relatively large birefringence and is insensitive to the temperature change is active. Conventionally, although capillary tubes are used to make polarization-maintaining photonic crystal structures, the manufacturing method is not known and there may be a problem in that the stacked photonic crystal structures are easily damaged during fiber extraction. have. It can be manufactured using a method of drilling a silica rod using a diamond drill, but can be time consuming, dangerous and inefficient.

According to one embodiment of the present invention for solving the above-described problems of the prior art, the cross section of the core of the photonic bandgap optical fiber may have a predetermined shape such as an ellipse shape while drawing out the optical fiber. It is possible to provide a photonic bandgap optical fiber which can be adjusted and maintain polarization, and a method of manufacturing the same.

Photonic bandgap optical fiber according to an embodiment of the present invention, the core portion extending in one direction; And one or more first tubes surrounding the core portion. A cross section of the core part in a direction perpendicular to the one direction may be located on a plane formed by a first axis and a second axis, and a length in the first axis direction may be smaller than a length in the second axis direction.

According to one or more exemplary embodiments, a method of manufacturing a photonic bandgap optical fiber includes: arranging one or more first tubes to form a core part surrounded by the one or more first tubes; Forming a base material from the at least one first tube; And drawing out the optical fiber by applying heat and pressure to the base material. In the step of drawing out the optical fiber, the temperature of one side of the base material may be less than the temperature of the other side of the base material.

According to the embodiments of the present invention, a bandgap optical fiber having a photonic crystal structure can be efficiently manufactured in a relatively short time. In addition, there is no factor causing light loss and no additional cost. Furthermore, photonic bandgap optical fibers of various structures can be easily manufactured.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, the present invention is not limited by the following examples.

1 is a perspective view illustrating a photonic bandgap optical fiber according to an embodiment, and FIG. 2 is a cross-sectional view of the photonic bandgap optical fiber shown in FIG. 1.

1 and 2, the photonic bandgap optical fiber may include a core portion 1 and one or more first tubes 2. The core part 1 may be an empty space formed by one or more first tubes 2. For example, the core part 1 may comprise air, or the core part 1 may be a vacuum. The core portion 1 may also consist of a relatively thin capillary tube (not shown). The capillary tube may comprise silicon oxide.

The core part 1 may be located in the center of the optical fiber. Alternatively, the core part 1 may be located on one side of the optical fiber while being surrounded by one or more first tubes 2. The core part 1 may extend in one direction. For example, the core portion 1 may extend in the z-axis direction in FIG. 1. However, the extending direction of the core part 1 may not be a linear direction, and the core part 1 may be formed to bend as needed.

The cross section 100 of the core part 1 in a direction perpendicular to the longitudinal direction of the core part 1 may have a predetermined shape. The cross section 100 of the core part 1 may be located on a plane formed by the first axis and the second axis perpendicular to the longitudinal direction of the core part 1. The first axis and the second axis may be perpendicular to each other. For example, in FIG. 1, the cross section 100 of the core part 1 may be located on a plane formed by the x-axis and the y-axis. The cross section 100 of the core part 1 may have a length in the first axial direction smaller than a length in the second axial direction. For example, the cross section 100 of the core part 1 may have an elliptic shape having a long axis of y-axis and a short axis of x-axis. However, the cross section 100 of the core portion 1 may be polygonal, closed surface, or other suitable shape.

One or more first tubes 2 may be arranged in a shape surrounding the core portion 1. The region in which the at least one first tube 2 is located may correspond to a clad region in the photonic bandgap optical fiber. The first tube 2 may be provided in a suitable number such that it can surround the core portion 1 tightly. Each of the one or more first tubes 2 may be empty. One or more first tubes 2 may be arranged in such a way that the space between each first tube 2 is minimized. If the space between each first tube 2 cannot be completely removed, a suitable filler (not shown) may be inserted into the space between each first tube 2. For example, the filler may be a silicon rod.

One or more of the first tubes 2 may form a photonic crystal structure. For example, the outer boundary line 200 of the entirety of the one or more first tubes 2 may have a hexagonal shape. However, the outer boundary line 200 may be of other polygons, closed curves, or other suitable shapes. Each of the one or more first tubes 2 may comprise quartz, silicon oxide or other suitable material. In order to maintain the stacking structure of the at least one first tube 2, the at least one first tube 2 may be surrounded by a fixing material (not shown). The fixing material will be described later in detail with reference to FIG. 3B.

In one embodiment, the second tube 3 may be formed to surround one or more first tubes 2. That is, one or more first tubes 2 may be located in the second tube 3. The second tube 3 may be fused to the one or more first tubes 2 such that no gap is formed between the one or more first tubes 2 and the second tube 2. The second tube 3 may comprise silicon oxide, or other suitable material.

In addition, a third tube 4 may be formed to surround the second tube 3. That is, the second tube 3 may be located in the third tube 4. Like the second tube 3, the third tube 4 may be fused to the second tube 3 so that a gap is not formed between the second tube 3 and the third tube 4. . The third tube 4 may comprise silicon oxide, or other suitable material.

In the photonic bandgap optical fiber according to the exemplary embodiment described above, when the core is an ellipse like a general optical fiber, the core portion of the optical fiber has an asymmetric refractive index distribution. For this reason, the birefringence (the refractive index difference between the y-axis and the x-axis) due to the difference in the optical paths of the long axis (e.g., y-axis) and the short axis (e.g., x-axis) is generated.

When the optical fiber having birefringence is incident on one axis of the long axis or the short axis, the polarized light does not couple to the other axis not incident by the refractive index difference between the two axes. In addition, as the birefringence is larger, the polarization maintaining function is further improved, and polarization can be maintained even with a change (for example, pressure or bending) applied from the outside of the optical fiber.

3A to 3F are diagrams illustrating each step of a method of manufacturing a photonic bandgap optical fiber according to an embodiment.

Referring to FIG. 3A, one or more first tubes 2 may be arranged to form a core portion 1 surrounded by one or more first tubes 2. Each first tube 2 may be empty. Each first tube 2 may be a capillary tube drawn using an optical fiber drawer. Each first tube 2 may comprise quartz, silicon oxide, or other suitable material. The outer boundary line 200 of the whole of the at least one first tube 2 may have a hexagonal shape. However, the outer boundary line 200 may be of other polygons, closed curves, or other suitable shapes.

The core part 1 may correspond to an empty space between the one or more first tubes 2. The core part 1 may include air, and the core part 1 may be a vacuum in the core part 1. Alternatively, the core portion 1 may be made of a relatively thin capillary tube (not shown). The capillary tube may comprise silicon oxide.

4 is a perspective view showing a preform for arranging one or more first tubes 2 as shown in FIG. 3A. Referring to FIG. 4, the first tube 2 ′ of some of the one or more first tubes 2 may be cut in the middle. In this case, the space between the cut first tube 2 ′ may correspond to the core part 1. Alternatively, a silicon rod having a relatively short length may be positioned instead of each cut first tube 2 '. One or more such preforms may be positioned adjacent to each other, and a portion corresponding to the core portion 1 may be drawn out. As a result, one or more first tubes 2 arranged as shown in FIG. 3A can be obtained.

Referring to FIG. 3B, after arranging the one or more first tubes 2 to form the core part 1, the fixing member 6 may be formed to surround the one or more first tubes 2. The fixture 6 may allow the one or more first tubes 2 to maintain the photonic crystal structure. For example, the fixing member 6 may maintain the outer boundary of the entirety of the one or more first tubes 2 in a predetermined shape, for example, a hexagonal shape. The fixing member 6 may be made of a material having a relatively high melting point such that it is not deformed even when the fiber is drawn out. For example, the fixing member 6 may be a metal line made of nichrome (Ni-Cr), iron (Fe), or another suitable metal or alloy. The fixing material may consist of an optical fiber or capillary tube.

Referring to FIG. 3C, one or more first tubes 2 may be disposed in the second tube 3. The second tube 3 may comprise silicon oxide. The structure consisting of the core part 1, the at least one first tube 2 and the second tube 3 may function as a preform for forming the optical fiber. In the present specification, the structure made as described above will be referred to as the first base material 11.

Referring to FIG. 3D, the second base material 12 may be extracted from the first base material described above. For example, the second base material 12 may be formed by applying heat and pressure to the first base material. The second base material 12 may be drawn out using an optical fiber drawing machine. The diameter of the drawn second base material 12 may be determined according to the use and function of the optical fiber.

In the drawn second base material 12, the second tube 3 may be fused to one or more first tubes 2. Thus, the second tube 3 may have a shape similar to the outer boundary of the one or more first tubes 2. Since the second tube 3 is fused to the one or more first tubes 2, the photonic crystal structure of the first tube 2 can be maintained even when a force is applied to the second base material 12 from the outside.

Referring to FIG. 3E, the second base material 12 may be disposed in the third tube 4. The third tube 4 may be made of silicon oxide.

Referring to FIG. 3F, the optical fiber 13 may be drawn out from the second base material 12 and the third tube 4. For example, the optical fiber 13 may be formed by applying heat and pressure to the second base material 12 and the third tube 4. In the drawn optical fiber 13, the third tube 4 may be fused to the second tube 3. Thus, the third tube 4 may have a shape similar to the second tube 3.

Meanwhile, in the process of drawing out the optical fiber 13, heat may be asymmetrically applied to the second base material 12. For example, the temperature of one side of the second base material 12 may be higher than the temperature of the other side of the second base material 12. That is, the second base material 12 may have an asymmetric temperature profile. As a result, in the drawn optical fiber, the cross section 100 of the core part 1 may have a length in a first axis (eg, x-axis) direction smaller than a length in a second axis (eg, y-axis) direction. For example, the cross section 100 of the core portion 1 may be elliptical in shape. The extraction process of the optical fiber will be described later in detail with reference to FIG. 5.

5A is a schematic diagram illustrating a drawing process of an optical fiber. Referring to FIG. 5A, the second base material 12 and the third tube 4s may be disposed in the furnaces 31 and 32. While the second base material 12 and the third tube 4 pass through the furnaces 31 and 32, heat may be applied to the second base material 12 and the third tube 4.

Heat may be asymmetrically applied to the second base material 12. For example, the first distance D1 from the second base material 12 to the first furnace 31 may be greater than the second distance D2 from the second base material 12 to the second furnace 32. have. Therefore, the temperature of the surface adjacent to the second furnace 32 in the second base material 12 may be relatively higher than the temperature of the surface adjacent to the first furnace 31. As a result, the cross section of the core portion of the second base material 12 may have a shape such as the ellipse described above.

In addition, the shape of the core of the second base material 12 may be adjusted by adjusting the negative pressure applied between the second base material 12 and the third tube 4. For example, an aspect ratio of the second base material 12 may be adjusted according to the magnitude of the negative pressure applied between the second base material 12 and the third tube 4.

In addition to heat, pressure may be applied to the second base material 12 and the third tube 4. The base 45 may be applied to the second base material 12. The gas 45 may comprise, for example, helium (He), argon (Ar), or other suitable material. Positive pressure may be applied to the core part and the first tube included in the second base material 12 by the gas 45 applied to the second base material 12. By applying a positive pressure to the second base material 12, the holes of the first tubes can be expanded. Thus, it is possible to form an optical fiber having a relatively large d / Λ (hole size / pitch).

Meanwhile, a negative pressure may be applied between the second base material 12 and the third tube 4 using the pump 40. By applying negative pressure between the second base material 12 and the third tube 4, the defect between the second base material 12 and the third tube 4 can be eliminated. In addition, the cross-sectional shape of the core part of the second base material 12 may be adjusted according to the magnitude of the negative pressure applied between the second base material 12 and the third tube 4. Furthermore, the third tube 4 can be fused to the second base material 12.

5B is a schematic diagram showing another drawing process of the optical fiber. Referring to FIG. 5B, the upper surface 120 of the second base material 12 may be melted to apply a positive pressure to the second base material 12. The magnitude of the pressure applied to the upper surface 120 of the second base material 12 may be determined based on the withdrawal speed of the optical fiber, the temperature of the furnaces 31 and 32, or other related factors.

In the embodiment illustrated in FIG. 5B, the functions and roles of the pump 40 and the furnaces 31 and 32 are the same as those described above with reference to FIG. 5A, and thus detailed descriptions thereof will be omitted.

Using the photonic bandgap optical fiber manufacturing method according to an embodiment of the present invention described above, it is possible to effectively produce a bandgap optical fiber of the photonic crystal structure in a relatively short time. In addition, there is no factor causing light loss and no additional cost. Furthermore, photonic bandgap optical fibers of various structures can be easily manufactured.

6A through 6C are photographs of photonic bandgap optical fibers according to embodiments of the present invention. As shown, the cross-sectional shape of the core portion of each optical fiber may be an elliptic shape. In this case, as the temperature profile of the base material is changed in the fiber drawing process, each core part illustrated in FIGS. 6A to 6C may have a different elliptic ratio.

Although the present invention described above has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a perspective view illustrating a photonic bandgap optical fiber according to an embodiment.

FIG. 2 is a cross-sectional view of the photonic bandgap optical fiber shown in FIG. 1.

3A to 3F are diagrams illustrating each step of a method of manufacturing a photonic bandgap optical fiber according to an embodiment.

4 is a perspective view showing a preform that can be used to make a photonic bandgap optical fiber.

5A and 5B are views illustrating a part of a method of manufacturing a photonic bandgap optical fiber according to an embodiment.

6A to 6C are photographs of photonic bandgap optical fibers in which the cross-sectional shape of the core portion is changed.

Claims (16)

delete delete delete delete delete delete delete Placing at least one first tube to form a core portion surrounded by the at least one first tube and comprising a vacuum or air; Placing the at least one first tube into a second tube to form a first base material; Drawing a second base material by applying heat and pressure to the first base material; Placing the second base material in a third tube; And Including drawing an optical fiber by applying heat and pressure to the second base material and the third tube, The drawing the optical fiber may include drawing the optical fiber to have an elliptic core by applying a negative pressure between the second base material and the third tube. In the step of drawing out the optical fiber, the temperature of one side of the second base material is less than the temperature of the other side of the second base material manufacturing method of the photonic bandgap optical fiber. delete The method of claim 8, Before forming the first base material, Forming a fixing material surrounding the at least one first tube, wherein the fixing material comprises nichrome (Ni-Cr) or iron (Fe) method of manufacturing a photonic bandgap optical fiber. The method of claim 8, Extracting the optical fiber, And expanding a hole of the first tube by injecting a gas into the second base material to apply pressure to the second base material. The method of claim 11, The gas is a method of producing a photonic bandgap optical fiber, characterized in that containing helium or argon. The method of claim 8, Extracting the optical fiber, And melting the upper surface of the second base material. The method of claim 8, Extracting the optical fiber, And arranging the second base material in the furnace to apply heat. 15. The method of claim 14, A first distance from said one side of said second base material to an adjacent portion of said furnace is greater than a second distance from said other side of said second base material to an adjacent portion of said furnace. Method of manufacturing optical fiber. The method of claim 8, The extracting of the optical fiber may further include adjusting an ellipticity of the core by adjusting a magnitude of a negative pressure applied between the second base material and the third tube. Method of manufacturing optical fiber.

Images