KR20230141081A - Large-Diameter Optical Fiber having Large Mode Area and Fabrication Method Thereof - Google Patents

Abstract

A disclosed embodiment provides optical fiber and a method for manufacturing the same, in which segmented cladding fiber with a large mode area and resistance to mechanical bending can be easily manufactured at low cost. The method for manufacturing optical fiber comprises the steps of: manufacturing a plurality of rods; stacking, among the plurality of rods, a plurality of first rods having a first refractive index and a plurality of second rods having a second refractive index lower than the first refractive index according to the cross-sectional structure of the optical fiber in which a first refractive index region and a second refractive index region are separated, to manufacture a preliminary prefoam; obtaining the final prefoam by inserting the preliminary prefoam into a prefoam tube; and obtaining optical fiber by heating and drawing the final prefoam.

Description

Large-Diameter Optical Fiber having Large Mode Area and Fabrication Method Thereof}

The disclosed embodiments relate to optical fibers and methods and devices for manufacturing the same, and to large-diameter optical fibers with a wide mode and methods for manufacturing the same.

Fiber lasers have advantages such as high energy efficiency, excellent optical quality and conversion efficiency, and small size, and have received much attention as a coherent light source over the past decades. However, there are limitations in that beam quality is deteriorated and output is limited due to nonlinear optical effects that occur when using a high-output laser as an optical fiber laser.

One of the efficient ways to suppress optical nonlinearity in high-power fiber lasers is to apply wide mode area optical fibers. An optical fiber has a wide mode area, so a large effective area can be obtained when the core diameter is enlarged. However, in order to satisfy a single mode, the refractive index of the core must be low and evenly distributed over the core area. And in this case, the optical fiber becomes sensitive to mechanical bending, causing problems in the optical fiber manufacturing process.

Therefore, in order to improve the performance of optical fiber lasers and amplifiers, it is necessary to efficiently design and manufacture optical fibers with a wide mode area. Recently, various wide mode area optical fibers such as PCF (Photonic Crystal Fiber), LCF (Leakage Channel Fiber), holey fiber, and step-index fiber have been studied to ensure high beam quality in high-power fiber lasers and amplifiers. However, such optical fibers have limitations in that they are difficult to mass-produce even in state-of-the-art facilities.

Therefore, the design and manufacturing process is not complicated and fibers that are resistant to mechanical bending are needed.

Korean Patent Publication No. 10-2017-0054035 (published on May 17, 2017)

The disclosed embodiments provide a high-quality large-diameter optical fiber that is strong against mechanical bending and has a wide mode, and a method of manufacturing the same.

The disclosed embodiments provide a method for manufacturing an optical fiber that can easily and at low cost manufacture a segmented cladding fiber having cladding in which low-refractive-index segments and high-refractive-index segments are alternately arranged in an azimuth direction.

An optical fiber manufacturing method according to an embodiment includes manufacturing a plurality of rods; Among the plurality of rods, a plurality of first rods having a first refractive index and a plurality of second rods having a second refractive index lower than the first refractive index are formed according to the cross-sectional structure of the optical fiber in which the first refractive index region and the second refractive index region are divided. Stacking to produce a preliminary preform; Obtaining a final preform by inserting the preliminary preform into a preform tube; and obtaining an optical fiber by heating and drawing the final preform.

In the step of manufacturing the preliminary preform, the plurality of first rods and the second rods may be combined by heating them to a recrystallization temperature or higher while arranging them according to the cross-sectional structure of the optical fiber.

The optical fiber has a structure in which a core having a first refractive index located at the center in a cross-section, a plurality of first segments having a first refractive index, and a plurality of second segments having a second refractive index are alternately arranged in an azimuthal direction around the core. It can be implemented as a segment cladding fiber (hereinafter referred to as SCF) with a cladding of

In the step of manufacturing the plurality of rods, the plurality of rods may be manufactured so that the plurality of rods have the same diameter and length.

The step of manufacturing the preliminary preform includes stacking the plurality of first rods according to the size and shape of the core, and stacking the plurality of first rods and the plurality of second rods into the first segment and the second segment. The preliminary preform can be obtained by stacking according to size and shape.

In the step of manufacturing the preliminary preform, a first rod having the largest diameter among the plurality of rods implemented with different diameters is placed at the center as a core rod, and the plurality of first rods and the first rod are around the core rod. 2 The cladding is implemented by arranging rods according to diameter, but rods having a small diameter can be arranged adjacent to the core.

The step of manufacturing the plurality of rods includes inserting silica powder for implementing the second rod or a mix powder mixed with silica powder and impurities for implementing the first rod into the rod tube, and the silica powder or mix powder is The plurality of rods can be obtained by heating and drawing the inserted rod tube.

In the step of manufacturing the plurality of rods, the rods can be obtained by drawing the rod tube into which silica powder or mix powder is inserted while heating it to a temperature above the recrystallization temperature.

In the step of manufacturing the plurality of rods, the rods may be dried by primary and secondary heating at a temperature below the recrystallization temperature, and then heated and drawn at a temperature above the recrystallization temperature.

In the step of manufacturing the plurality of rods, helium may be injected into the rod tube and secondary heating may be performed after the primary heating to prevent bubbles from being generated within the rod.

In the step of manufacturing the plurality of rods, the silica powder or the mixed powder may be heated to remove moisture and then inserted into the rod tube.

In the step of manufacturing the plurality of rods, the mixed powder can be obtained by mixing the alumina powder, which is the impurity, with the silica powder.

In the step of manufacturing the plurality of rods, the silica powder or mixed powder may be inserted into a silica tube having a second refractive index.

The step of manufacturing the plurality of rods includes inserting the silica powder into a silica tube having a second refractive index when manufacturing the first rod, and inserting the silica powder into a silica tube having a refractive index greater than or equal to the first refractive index when manufacturing the second rod. Mix powder can be inserted into.

An optical fiber according to an embodiment is an optical fiber including a core and a cladding formed around the core divided into at least one first segment and at least one second segment having different refractive indices, wherein the core and the at least a plurality of first rods arranged in a stack along each of one first segment and having a first refractive index; and a preform including a plurality of second rods stacked and disposed along each of the at least one second segment and having a second refractive index lower than the first refractive index.

Therefore, the optical fiber and its manufacturing method according to the embodiment obtain a plurality of rods by filling a glass tube with silica powder alone or a mixed powder of silica powder and doping powder and hot drawing, and stacking the obtained plurality of rods to form a preform. By manufacturing optical fibers by hot drawing them again after fabrication, segment cladding fibers that have a wide mode and are resistant to mechanical bending can be easily manufactured at low cost.

Figure 1 is a diagram for explaining segment cladding fibers.
Figure 2 shows an optical fiber manufacturing method according to one embodiment.
Figure 3 shows a detailed process of the rod manufacturing step in Figure 2.
Figure 4 shows an example of powder used in optical fiber.
Figure 5 shows an example of a rod manufactured in the rod manufacturing step of Figure 2.
Figure 6 shows an example of a preliminary preform manufactured in the preform manufacturing step of Figure 2.
Figure 7 shows the preform inserted in the preform tube insertion step of Figure 2.
Figure 8 shows a cross section of the preform inserted into the tube of Figure 7.
Figure 9 shows a cross section of an optical fiber manufactured according to an example.
Figure 10 shows the electric field distribution in a single mode of the SCF of Figure 9.
11 and 12 show optical fibers manufactured according to another embodiment.

Hereinafter, specific embodiments of one embodiment will be described with reference to the drawings. The detailed description below is provided to provide a comprehensive understanding of the methods, devices and/or systems described herein. However, this is only an example and the present invention is not limited thereto.

In describing one embodiment, if it is determined that a detailed description of the known technology related to the present invention may unnecessarily obscure the gist of an embodiment, the detailed description will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification. The terminology used in the detailed description is intended to describe only one embodiment and should in no way be limiting. Unless explicitly stated otherwise, singular forms include plural meanings. In this description, expressions such as "comprising" or "having" are intended to indicate any features, numbers, steps, operations, elements, part or combination thereof, and one or more other than those described. It should not be construed to exclude the existence or possibility of other characteristics, numbers, steps, operations, elements, or parts or combinations thereof. In addition, "... part", "... period", " described in the specification. Terms such as “module” and “block” refer to a unit that processes at least one function or operation, which may be implemented as hardware, software, or a combination of hardware and software.

Figure 1 is a diagram for explaining segment cladding fibers.

Figure 1 shows an example of a segment cladding fiber (SCF). Like a general optical fiber, the SCF includes a core 14 located at the center and having a high refractive index (n ₁ ) and a cladding 13 surrounding the core 14. However, as shown in FIG. 1, the cladding 13 surrounding the core 14 in the SCF includes a first segment 11 having a high refractive index (n ₁ ) and a low refractive index like the core 14 in the azimuthal direction. It has a structure in which second segments 12 having (low index) (n ₂ ) are alternately and repeatedly arranged. That is, the segment cladding fiber is implemented in a radial structure in which a plurality of first segments 11 and second segments 12 radiate outwards around the core 14.

Here, as an example of SCF, eight first segments 11 and eight second segments 12 are alternately and repeatedly arranged, but together with the first and second segments 11 and 12 that are repeatedly arranged, The number can be set in various ways, such as 4, 6, or 8. In addition, as an example of SCF, the angular ranges (2θ 1 and 2θ 2 ) of the first segment 11 and the second segment 12 are shown to be the same, but the angle ranges (2θ ₁ and 2θ ₂ ) of the first segment 11 and the second segment 12 are shown as the same. The angle ranges 2θ ₁ and 2θ ₂ may be set differently.

SCF with this structure is known to have the advantage of being able to simultaneously meet wide mode area and single mode requirements. SCF does not require arrangement of air holes like holely fiber, so it can provide longitudinal uniformity, which is important in optical fibers with a long structure in the longitudinal direction. Additionally, the refractive index contrast of existing optical fibers can be used, and the chromatic dispersion and polarization properties of SCF can be easily adjusted within the limits of the actual fiber manufacturing process. Moreover, since SCF is a leaky optical fiber in which all higher-order modes can be effectively eliminated by the cladding structure, single-mode operation is possible over an extended wavelength range while maintaining a large mode area to effectively cope with optical nonlinearity problems. These advantages of SCF can be applied to high-power fiber lasers, optical fiber amplifiers, high-density wavelength division multiplexing optical communication systems, and mid-infrared sensing. Additionally, because SCF is a fully solid fiber, it is potentially less sensitive to geometrically induced birefringence and scattering losses at the core-cladding interface.

However, as shown in FIG. 1, SCF has a complex cross-sectional structure and has a problem in that it is not easy to manufacture. Due to these manufacturing limitations, SCF is not actively distributed despite its many advantages. Therefore, there is a need for a manufacturing technique that can easily manufacture SCF with a complex cross-sectional structure.

Figure 2 shows a method of manufacturing an optical fiber according to an embodiment, Figure 3 shows a detailed process of the rod manufacturing step of Figure 2, and Figure 4 shows an example of powder used in an optical fiber. And Figure 5 shows an example of a rod manufactured in the rod manufacturing step of Figure 2.

First, referring to FIG. 2, the optical fiber manufacturing method according to this embodiment first manufactures a plurality of rods 51 (21). Here, as shown in FIG. 5, the plurality of rods may have a predetermined diameter (eg, 1 mm) and length (eg, 300 mm). Additionally, the plurality of rods 51 may be manufactured by dividing them into a first rod having a high refractive index and a second rod having a low refractive index. At this time, the first rod with a high refractive index may be used as an element constituting the core 14 of the SCF or the first segment 11 with a high refractive index, and the second rod with a low refractive index may be used as a second rod with a low refractive index of the SCF. It can be used as an element constituting the segment 12.

Referring to FIG. 3, specifically, in the step 21 of manufacturing a rod, the raw material to be manufactured into the rod 51 is first pulverized to prepare powder (31). High purity silica (SiO ₂ ) is basically used as a material for manufacturing optical fibers. However, high-purity silica (SiO ₂ ) is a material with a low refractive index in optical fibers and can be used to implement the second segment 12, but cannot implement the first segment 11, which must have a high refractive index. Accordingly, in order to implement the first segment 11 with a high refractive index, it must be doped by adding impurities. There are various known impurities added to achieve high refractive index, but here, as an example, it is assumed that alumina (Al ₂ O ₃ ) is used. Therefore, in the embodiment, as shown in Figures 4 (a) and (b), powder is prepared by pulverizing high-purity silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), respectively.

And when the powder obtained by grinding high-purity silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) is prepared, the silica powder and alumina powder are mixed at a specified ratio to create a first rod with a high refractive index (32). At this time, the mixing ratio of silica powder and alumina powder can be adjusted in various ways depending on the required refractive index of the first rod.

At this time, since the second rod having a low refractive index can be manufactured only from silica (SiO ₂ ), when manufacturing the second rod, the powder mixing process can be omitted.

When silica powder or a mixing powder of silica powder and alumina powder is prepared, the powder is heated to remove moisture from the powder (33). At this time, the powder may be heated, for example, in an oven at 150°C for 1 hour to remove moisture. In some cases, a grinding or milling process may be added so that the powder from which moisture has been removed becomes smaller and more uniformly sized particles.

Then, the powder from which moisture has been removed is inserted into the silica tube and filled (34). This is to apply the PIT (Powder-in-tube: PIT) technique, which inserts material into a tube and manufactures it into the required shape. At this time, when a first rod with a high refractive index is to be manufactured, mixing powder is inserted into the silica tube, and when a second rod with a low refractive index is to be manufactured, the silica powder is inserted into the silica tube.

Here, for example, the silica tube may have an inner diameter of 17 mm and an outer diameter of 21 mm, and the length can be variously adjusted depending on the amount of powder to be inserted. And since silica tubes are used to manufacture rods, they are hereinafter referred to as rod tubes.

Afterwards, the powder inserted into the load tube is first dried (35). During primary drying, the rod tube into which the powder is inserted can be dried by heating it to a specified temperature (for example, 1100°C). After primary drying, helium gas is injected and heated to a specified temperature (e.g., 1700°C) to secondary dry the powder inserted into the rod tube (36). Here, the first and second drying temperatures (1100°C, 1700°C) must be lower than the recrystallization temperature of the powder and rod tube. That is, the powder and rod tube must not melt. In addition, helium gas is injected between the first drying and the second drying to ensure that the excess air remaining inside the rod tube is completely discharged and to prevent air bubbles from being generated in the manufactured rod 51.

When secondary drying is performed and moisture and air are removed from the rod tube, the melted powder and rod tube are stretched by drawing while heating to a temperature above the recrystallization temperature of the rod tube and powder (for example, 2050°C). Obtain a rod with a specified diameter (here 1 mm) (37). That is, according to the PIT technique, the entire rod tube into which the powder is inserted is drawn using a hot-drawing technique to obtain the rod. Since the drying and drawing process requires high temperature, it can be performed in a furnace, but is not limited to this.

Since the rod tube is made of silica (SiO ₂ ) material, which is basically the same material as the powder inserted inside, and the silica (SiO ₂ ) material itself is used as a material for optical fiber, in the embodiment, it is inserted inside the rod tube and melted. Rather than drawing only the powder, the rod is obtained by drawing the entire rod tube into which the powder is inserted.

However, since the lengths of the rods obtained by drawing may be different from each other, the obtained rods are cut in units of designated lengths (300 mm) (38).

In this embodiment, each of the plurality of rods 51 inserts silica powder or a mixing powder mixed with silica powder and alumina powder as a doping material into the rod tube, heats and draws it to a temperature above the recrystallization temperature, and cuts it into a specified size. It can be obtained by doing this.

Among the plurality of rods obtained here, the first rod manufactured by filling the inside of the rod tube with a mixing powder of silica powder and alumina powder is different in the materials of the rod tube and the powder in the tube. However, in the case of the second rod manufactured by filling the inside of the rod tube with only silica powder, as the same material is melted and manufactured at a temperature above the recrystallization temperature, the rod tube and the powder filled inside are substantially fused and the boundary disappears.

When a plurality of first rods having a high refractive index and a plurality of second rods having a low refractive index are obtained according to the method of FIG. 3, the plurality of first rods and the plurality of second rods are arranged according to the cross-sectional structure of the pre-designed SCF. A preliminary preform (65) is manufactured (22).

In the preform manufacturing step, a plurality of first rods and a plurality of second rods are first stacked according to the cross-sectional structure of the SCF, and the stacked first and second rods are heated and combined to produce a preliminary preform (23). At this time, the shape and structure of the core 64 of the preliminary preform 65 and the segment of the cladding according to the cross-sectional structure of the SCF can be determined in advance using a finite element method (FEM), etc., depending on the characteristics of the required optical fiber. , the first and second rods may be stacked according to the determined shape and structure of the segments of the core 64 and cladding. That is, according to the cross-sectional structure of the optical fiber divided into a high refractive index region and a low refractive index region, a plurality of first rods with a high refractive index and a plurality of second rods with a low refractive index are stacked and heated to obtain a preliminary preform.

At this time, the preliminary preform production can be performed on a glass work lathe, and the bonding between rods can be performed by fully or partially heating to a temperature above the recrystallization temperature (for example, 2200°C) using an oxygen propane burner or the like.

The preliminary preform may be manufactured by sequentially combining the individual rods by heating each of the plurality of first rods and the plurality of second rods each time they are stacked, but the plurality of first rods and the plurality of second rods are stacked. It can also be manufactured by heating and combining them all at once.

Figure 6 shows an example of a preliminary preform manufactured in the preform manufacturing step of Figure 2.

In this embodiment, a plurality of rods 51 are first manufactured and the preliminary preform 65 is manufactured by simply stacking and heating the manufactured plurality of rods 51, so that the preliminary preform 65 can be easily formed in a very free form. It can be configured. This means that even if the cross-section of the optical fiber has any structure, the required cross-sectional structure can be realized by stacking a plurality of rods 51 according to the cross-sectional structure. Therefore, as shown in FIG. 6, the preliminary preform 65 for SCF with a complex cross-sectional structure can be manufactured very easily. That is, not only the shape and size of the core 64, but also the shape, number, and size of the first and second segments constituting the cladding can be freely adjusted, and components other than the first and second segments can be added to the cladding. . For example, a low refractive index element or a high refractive index element may be added between the core 64 and the first and second segments.

Here, as an example, a plurality of first rods 61 of high refractive index are stacked in a hexagonal shape to form the core 64, and the first segment of the cladding has a plurality of first rods 61 identical to the core 64. It is implemented by stacking in a shape that radiates from each corner of the hexagonal core 64, and the second segment has a shape in which a plurality of second rods 62 of low refractive index radiate from each corner of the hexagonal core 64. It was assumed that a preliminary preform for the SCF was produced by being stacked and implemented. However, the shape and structure of the core 64 and the cladding segments in the preliminary preform 65 for SCF can be adjusted in various ways depending on the design. Although the shape and structure of the core 64 and the cladding segments are modified in various ways, according to the embodiment, only the arrangement structure in which the plurality of first and second rods 61 and 62 are stacked is modified to easily form a preliminary preform. (65) can be produced.

As shown in FIG. 6, when the preliminary preform 65 for SCF is manufactured, the preliminary preform 65 is inserted into the silica tube 66 to obtain the final preform (24).

Figure 7 shows a preliminary preform inserted in the preform tube insertion step of Figure 2, and Figure 8 shows a cross section of the preliminary preform inserted into the tube of Figure 7.

The silica tube 66 is a tube made of the same material as the rod tube used in rod manufacturing, but as shown in FIGS. 7 and 8, it may have an inner diameter corresponding to the diameter of the manufactured preliminary preform 65. there is. Referring to FIG. 8, 17 rods are arranged in the maximum diameter direction in the preliminary preform 65, and since each rod has a diameter of 1 mm, the inner diameter of the silica tube 66 is 17 mm or more (here, 19 mm as an example). The outer diameter may be 25mm. At this time, the diameter of the core 64 in the preliminary preform 65 is 5 mm.

As shown in FIG. 7, the silica tube 66 may have an open end at which the preliminary preform 65 is inserted, while the other end may be closed. Hereinafter, in order to distinguish between the rod tube used in rod manufacturing and the silica tube 66 into which the preliminary preform 65 is inserted, the silica tube 66 into which the preliminary preform 65 is inserted is referred to as a preform tube. Here, the preform tube 66 into which the preliminary preform 65 is inserted is called the final preform.

When the preliminary preform 65 is inserted into the preform tube 66 and the final preform is obtained, the SCF is manufactured (25). In the step of manufacturing the SCF, the final preform, in which the manufactured preliminary preform 65 is inserted into the preform tube 66, is heated to a temperature (2200° C.) above the recrystallization temperature (26). And, similar to the process of obtaining the rod 51, the final heated preform is drawn to obtain the SCF (27). At this time, the preliminary preform 65 is pulled out together with the preform tube 66.

Figure 9 shows a cross section of an optical fiber manufactured according to an example.

When the heated preliminary preform 65 and the preform tube 66 are drawn together to obtain an SCF, the cross section of the SCF is stacked, as shown in FIG. 9, and consists of a plurality of first rods and While the arrangement structure of the plurality of second rods remains almost the same, the overall diameter becomes very small.

In FIG. 9, (a) is a diagram to explain that the arrangement structure of the plurality of first and second rods stacked on the cross section of the SCF is maintained. However, as described above, not only the preform tube 96 and the second rod 92, but also the rod tube forming the outer peripheral surface of the first rod 91 is composed of only silica. Therefore, when the final preform is heated above the recrystallization temperature, the outer peripheral surfaces of the preform tube 96, the second rod 92, and the first rod 91 are melted and fused, and the actual SCF is as shown in (b) of Figure 9. It can be obtained through structure.

The diameter of the drawn SCF can be determined in various ways, and is assumed to be 138 ㎛ as an example. Since the final preform with a diameter of 25 mm is drawn to obtain an SCF with a diameter of 138 μm, the SCF can be obtained with a length of hundreds of meters or more. At this time, the diameter of the core is approximately 20㎛.

Figure 10 shows the electric field distribution in a single mode of the SCF of Figure 9.

In Figure 10, (a) and (b) show the mode intensity, that is, the electric field distribution, in a single mode for light with a wavelength (λ) of 1 ㎛ and 1.55 ㎛, respectively, and (c) shows the X-axis direction and diagonal Shows the results of a graph showing the mode intensity in each direction. In (c), the mode intensity in the direction of the first segment having a high refractive index is expressed as a solid line, and the mode intensity in the direction of the second segment having a low refractive index is expressed as a dotted line. As shown in Figures 10 (a) and (b), it can be seen that in the SCF manufactured in this example, the mode intensity is hardly diffused to the cladding by the first segment with a high refractive index, but is concentrated in the core. You can. And looking at the mode intensity distribution in (c), light is captured by the first segment with a high refractive index rather than the second segment with a low refractive index. Therefore, the SCF implemented according to the embodiment may operate in a single mode. According to experiments, it was confirmed that the SCF of the example can operate in a single mode in the wavelength range of 1㎛ to 1.7㎛. And at a wavelength of 1.55㎛, the confinement loss of LP11 and LP01 modes was found to be 16.8dB/m and 0.49dB/m. Therefore, in a 1.23m long SCF, LP11 can be attenuated with an extinction ratio of 20dB. Additionally, ^the effective mode area of SCF was confirmed to be 150㎛ ² , 231 ㎛ 2 , and 260 ㎛ ² when the wavelength (λ) was 1 ㎛, 1.55 ㎛, and 1.7 ㎛, respectively. That is, even though the core has a high refractive index, it can have a large effective mode area.

11 and 12 show optical fibers manufactured according to another embodiment.

In the above, it was explained that in order to manufacture the preliminary preform 65 of the SCF, a plurality of rods 51 all having the same diameter are stacked. In this way, when the plurality of rods 51 all have the same diameter, the plurality of rods 51 need only be stacked by dividing them into the high refractive index rod 61 and the low refractive index rod 62. However, as shown in Figure 9, each rod in the SCF can be viewed as configuring a cell shape, and when the relative diameter of the rod 61 is large compared to the overall diameter of the preliminary preform 65, the cell size is relatively large. Because of their size, the segment shape cannot be precisely controlled. Additionally, the divided core is implemented with a plurality of high refractive index rods (61). This causes a small amount of single mode loss, which may appear differently depending on the direction of the effective mode area.

Accordingly, in Figures 11 and 12, a plurality of high refractive index rods and a plurality of low refractive index rods having different diameters are obtained, and a plurality of high refractive index rods and a plurality of low refractive index rods having different diameters are stacked. It represents SCF.

In the SCF of FIGS. 11 and 12, the core rods 114 and 124 having the largest diameter are first placed in the center, and a plurality of high refractive index rods 111 and 121 are formed in a pattern radiating outward from the core rods 114 and 124. ) and stack a plurality of low refractive index rods 112 and 122. At this time, the plurality of high refractive index rods 111, 121 and the plurality of low refractive index rods 112, 122 are arranged so that the closer they are to the core rods 114, 124, the smaller the diameter is, and the more spaced apart the rods are, the larger the diameter. , the range of each segment is accurately maintained, and the same number of rods are arranged even if the distance from the core rods 114 and 124 is different, thereby maintaining consistency.

An SCF manufactured by stacking rods with this arrangement structure is more insensitive to mechanical bending than the SCF of FIG. 9, has lower single mode loss in a bent state, and can have a large effective mode area in all directions.

In addition, in the SCF of FIGS. 9 and 11, both the high refractive index rods 61 and 111 and the low refractive index rods 62 and 112 were manufactured by inserting powder into the rod tube according to the PIT technique. However, as described above, the rod tube is a tube made of the same silica material as the powder for manufacturing the low refractive index rods 62 and 112. Therefore, in the SCF of FIGS. 9 and 11, the stacked high refractive index rods 61 and 111 are implemented with a structure in which a low refractive index material is interposed. Accordingly, in the SCF of FIG. 12, a high refractive index rod 121 is manufactured by inserting a mixed powder of silica and alumina into a rod tube having a high refractive index. At this time, the high refractive index rod tube may have a higher refractive index than the mixed powder. In this way, when manufacturing a rod with a high refractive index using a rod tube with a high refractive index, light is more easily captured by the first segment with a high refractive index, so that it can have a large effective mode area and be robust against mechanical bending.

In the above, for convenience of explanation, the first rod and the second rod were described as having a high refractive index and a low refractive index, respectively. However, this is to express the relative difference in refractive index. The high refractive index is called the first refractive index, and the low refractive index is called the first refractive index. It can be said to be a lower second refractive index.

In Figures 2 and 3, each process is described as being sequentially executed, but this is only an illustrative explanation, and those skilled in the art can perform the procedures described in Figures 2 and 3 without departing from the essential characteristics of the embodiments of the present invention. It can be modified and modified in various ways by executing by changing the order, executing one or more processes in parallel, or adding other processes.

The optical fiber manufacturing method shown in FIG. 2 may be performed in a computing environment including a computing device, and may include a computing device implemented including at least one processor and a computer-readable storage medium.

Although the present invention has been described in detail through representative embodiments above, those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the attached claims.

11: first segment 12: second segment
13: Cladding 14, 64: Core
51: Rod 61: High refractive index rod
62: low refractive index rod 65: preliminary preform
66: preform tube 114, 124: core rod
126: High refractive index rod tube

Claims (20)

manufacturing a plurality of rods;
Among the plurality of rods, a plurality of first rods having a first refractive index and a plurality of second rods having a second refractive index lower than the first refractive index are formed according to the cross-sectional structure of the optical fiber in which the first refractive index region and the second refractive index region are divided. Stacking to produce a preliminary preform;
Obtaining a final preform by inserting the preliminary preform into a preform tube; and
A method of manufacturing an optical fiber comprising the step of heating and drawing the final preform to obtain an optical fiber. The method of claim 1, wherein the step of manufacturing the preliminary preform is
A method of manufacturing an optical fiber in which the plurality of first rods and the second rods are arranged according to the cross-sectional structure of the optical fiber and heated to a recrystallization temperature or higher to combine them. The method of claim 2, wherein the optical fiber
A cladding structure in which a core of a first refractive index located at the center in the cross-section and a plurality of first segments with a first refractive index and a plurality of second segments with a second refractive index are alternately arranged in an azimuthal direction around the core. A method of manufacturing an optical fiber implemented as a segmented cladding fiber (hereinafter referred to as SCF). The method of claim 3, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber wherein the plurality of rods are manufactured to have the same diameter and length. The method of claim 4, wherein the step of manufacturing the preliminary preform is
The plurality of first rods are stacked according to the size and shape of the core, and the plurality of first rods and the plurality of second rods are stacked according to the size and shape of the first segment and the second segment. Method for manufacturing optical fibers obtaining a preliminary preform. The method of claim 3, wherein the step of manufacturing the preliminary preform is
Among the plurality of rods implemented with different diameters, a first rod having the largest diameter is disposed at the center as a core rod, and the plurality of first rods and second rods are arranged according to diameter around the core rod. A method of manufacturing an optical fiber that implements the cladding and disposes a rod having a small diameter adjacent to the core. The method of claim 1, wherein manufacturing the plurality of rods comprises
Silica powder for implementing the second rod or a mix powder mixed with silica powder for implementing the first rod and impurities is inserted into the rod tube, and the rod tube into which the silica powder or mix powder is inserted is heated and drawn. A method of manufacturing an optical fiber obtaining the plurality of rods. The method of claim 7, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber in which a rod is obtained by drawing a rod tube into which silica powder or mixed powder is inserted while heating it to a temperature above the recrystallization temperature. The method of claim 8, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber that involves primary and secondary heating and drying at a temperature below the recrystallization temperature, followed by heating and drawing at a temperature above the recrystallization temperature. The method of claim 9, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber by injecting helium into the rod tube and performing secondary heating after the primary heating to prevent bubbles from being generated within the rod. The method of claim 7, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber in which the silica powder or the mixed powder is heated to remove moisture and then inserted into the rod tube. The method of claim 7, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber in which the mixed powder is obtained by mixing the alumina powder, which is the impurity, with the silica powder. The method of claim 7, wherein manufacturing the plurality of rods comprises
A method of manufacturing an optical fiber by inserting the silica powder or mixed powder into a silica tube having a second refractive index. The method of claim 7, wherein manufacturing the plurality of rods comprises
When manufacturing the first rod, the silica powder is inserted into a silica tube having a second refractive index, and when manufacturing the second rod, the mix powder is inserted into a tube made of a material with a refractive index greater than or equal to the first refractive index. method. An optical fiber comprising a core and a cladding formed around the core divided into at least one first segment and at least one second segment having different refractive indices,
a plurality of first rods arranged in a stack along each of the core and the at least one first segment and having a first refractive index; and
An optical fiber having a structure in which a preform is stretched and includes a plurality of second rods stacked along each of the at least one second segment and having a second refractive index lower than the first refractive index. The method of claim 15, wherein the preform is
An optical fiber further comprising a preform tube into which the stacked plurality of first rods and the plurality of second rods are inserted. The method of claim 16, wherein the optical fiber
An optical fiber that is realized by heating and drawing the preform to a temperature above the recrystallization temperature and having a structure according to the cross section of the preform and being stretched to a length. The method of claim 15, wherein the optical fiber
Implemented as a segmented cladding fiber (hereinafter referred to as SCF) having a structure in which the core having a first refractive index is located at the center in the cross-section and the plurality of first segments and the plurality of second segments are alternately arranged in an azimuthal direction around the core. optical fiber. The method of claim 18, wherein the preform is
a core area where at least one first rod is disposed according to the size and shape of the core;
a plurality of first segment areas where a plurality of first rods are stacked according to the size and shape of each of the plurality of first segments; and
An optical fiber comprising a plurality of second segment areas where a plurality of second rods are stacked according to the size and shape of each of the plurality of second segments. The method of claim 19, wherein the plurality of first rods are obtained by inserting silica powder and heating and drawing a mixed powder of silica powder and impurities in a rod tube, and the plurality of second rods are obtained by inserting silica powder into a rod tube and heating and drawing. Optical fiber obtained by inserting powder, heating and drawing.