JP2006089317A - Glass preform, method for producing the same, and optical waveguide material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply suitable processings in making a glass preform used to be drawn into an optical waveguide material usable in fiber amplifiers and fiber lasers to avoid problems such as quality deterioration in such optical waveguide material, which leads to power loss of input light from a source and output decrease. <P>SOLUTION: The entire constituent elements of a glass preform 5, i.e., an outer glass pipe 1, a plurality of glass capillaries 3 which form a clad, and at least one glass rod 2 or glass capillary 3 which forms a core doped with a dopant are fused with each other with accompanied thermal deformation, and the periphery 5x is ground or polished. Desirably, the grinding or the polishing is performed by using the glass rod 2 or glass capillary 3 which forms the core as a reference. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a glass preform, a method for manufacturing the same, and an optical waveguide material, and more particularly to a technique for improving the shape and properties of the outer periphery of the glass preform and the optical waveguide material obtained therefrom.

  As is well known, an optical waveguide material such as a photonic crystal fiber, a holey fiber, or a photonic bandgap fiber is composed of a core portion disposed on an axis and a cladding portion surrounding the core portion, and has a fiber shape or It has a rod shape (see, for example, Patent Document 1 below). In this case, the core portion of the optical waveguide material is formed as a non-voided state or a state having holes, whereas the cladding portion is formed of the main medium and a plurality of holes. The plurality of holes in the cladding portion are arranged in parallel with the optical waveguide direction, and are arranged periodically or randomly in a cross section orthogonal to the axis. This type of optical waveguide material has attracted attention as an important material in future optical communication systems because it has excellent light propagation characteristics.

  In particular, an optical waveguide material in which a core material is doped with a dopant material such as erbium can enhance the optical amplification function or the nonlinear optical effect, so that it is proposed to be used for a fiber amplifier or a fiber laser or is put to practical use. (For example, see Patent Document 1 and Patent Document 2 below).

  On the other hand, as a method of manufacturing this type of optical waveguide material, a method of drawing a bundle of a plurality of glass capillaries is the mainstream. More specifically, according to this manufacturing method, a plurality of cylindrical glass capillaries are formed. When bundling and drawing, a plurality of glass capillaries are deformed by heating at the time of drawing, thereby reducing gaps generated between the glass capillaries. However, with this manufacturing method, it is difficult to reliably eliminate gaps between the glass capillaries. If these voids remain even after drawing, the performance of the optical waveguide material as a product is remarkably deteriorated or does not function at all, which is an important problem.

  In this case, the optical waveguide material in which the core portion is doped with the dopant material is not intended. However, according to Patent Document 3 below, the optical waveguide is used to deal with the problem that the gap remains. As a pre-stage of drawing the material, a glass rod to form the core and a plurality of glass capillaries to form the cladding are arranged in the glass outer tube, and the inside of the glass outer tube is maintained in a reduced pressure state. And a method for manufacturing a glass preform in which all are fused and integrated with each other by heating. According to such a manufacturing method, it is possible to prevent a gap from being generated between all of the glass rod and each glass capillary.

JP 2002-506533 A JP 2002-55239 A JP 2004-43286 A

  By the way, the manufacturing method disclosed in Patent Document 3 described above is a pre-stage of drawing an optical waveguide material in which the core material is not doped with a dopant material. A glass preform is produced by fusing rods and glass capillaries to each other. A glass preform that is the base material of an optical waveguide material doped with a dopant material in the core is the same as this. Whether or not it can be appropriately produced by the manufacturing method is still unclear. That is, when the dopant material is doped in the glass rod that should form the core part in the glass preform, the fused state between the glass rod and each glass capillary is the case where the dopant material is not doped in the glass rod It is understood that they are different from each other, and it is considered that there is a case where a good fusion state cannot be obtained. Due to such matters, a glass rod doped with a dopant material is used as a glass preform in which a glass outer tube, a glass rod, and glass capillaries are all fused together. Can be inferred to be difficult to produce.

  On the other hand, even if a glass preform having a fused state similar to that described above is obtained by the above manufacturing method using a glass rod doped with a dopant material, the fundamental as shown below. It will cause problems.

  That is, as in the glass preform disclosed in Patent Document 3 above, when the inside of the glass outer tube is depressurized and heated to have a configuration in which no gap is generated between all of the glass rod and each glass capillary. In other words, the outer shape of the glass capillary is deformed to fill the gap, and the outer peripheral surface of the glass preform is contracted and deformed unevenly in the radial direction. Therefore, in such a method, not only the outer peripheral surface of the glass preform is not a perfect circle but also the outer peripheral surface 50x of the glass preform 50 has a wavy shape as shown in FIG. A reference is made to the enlarged part shown by A1, and the outer diameter precision deteriorates.

  Then, if such a glass preform is drawn as it is, the circularity of the outer peripheral surface of the optical waveguide material is deviated and the radial dimension of the outer peripheral surface is uniform, for example, becomes an ellipse. In addition, the smoothness of the outer peripheral surface is hindered and the accuracy of the outer diameter deteriorates, making it difficult to produce a highly accurate optical waveguide material that can be used appropriately for fiber amplifiers, fiber lasers, and the like. In addition, when this type of optical waveguide material is fitted to a connection component on the basis of the outer diameter and connected to another component, etc., the fitting between the connection component and the optical waveguide material may be rattled or smoothly fitted. Therefore, if this is used for a fiber amplifier or fiber laser, the loss of input optical power from the source will be caused. May cause a problem that the output is reduced accordingly.

  The above problems are not only when drawing glass preforms with reduced pressure and heating to the glass outer tube, but also when drawing only a bundle of glass capillaries. However, the gap between the glass capillaries may be caused in the same manner, for example.

  In the present invention, the glass preform produced in the pre-stage of drawing of the optical waveguide material is used for the optical waveguide material after drawing, particularly the outer diameter accuracy of the optical waveguide material that can be used for fiber amplifiers and fiber lasers. It was made by paying attention to adverse effects, and by applying appropriate processing during the production of glass preforms, problems such as the deterioration of the quality of the optical waveguide material and the loss of input optical power from the source and the reduction of the output have occurred in advance. It is a technical problem to prevent it.

  The present invention created in order to solve the above technical problem is used for drawing an optical waveguide material having a clad part and a core part, and a plurality of pieces forming a clad part in an inner hole of a glass outer tube. The glass capillary is filled with at least one glass rod or glass capillary forming the core portion, and the glass capillary holes are periodically arranged in a cross section perpendicular to the axis. In the reforming, at least one glass rod or glass capillary forming the core portion is doped with a dopant material, and the glass outer tube, the plurality of glass capillaries, and the at least one glass rod or Glass capillaries are all fused together with deformation, and the outer periphery is ground or polished It is an feature.

  In this case, as the “glass rod”, a solid and non-porous one is used, and as the “glass capillary”, a hollow one having a hole is used. Therefore, when the glass rod is used to form the core portion, a photonic crystal fiber, holey fiber, or the like in which the core portion is non-porous is manufactured as an optical waveguide material. When a glass capillary is formed, a photonic bandgap fiber or the like having a hole in the core is produced as an optical waveguide material. In addition, the above-mentioned “glass capillary forming the cladding part” means a glass capillary forming a part corresponding to the cladding part in the glass preform, and the above “glass rod or glass capillary forming the core part” Means a glass rod or a glass capillary forming a portion corresponding to the core portion in the glass preform. Furthermore, the above-mentioned "all are mutually fused" means that between a plurality of glass capillaries forming a clad part and at least one glass rod or glass capillary forming a core part thereof, This means that the glass outer tube and the glass outer tube are in contact with each other by softening, and only when all these components are fused together. In addition, the case where all of the constituent elements are fused on a part of the surface (or part of the surface or the entire surface) is also included.

  According to such a configuration, each component composed of a glass rod or glass capillary forming a core portion doped with a dopant material, a glass outer tube, and a plurality of glass capillaries forming a cladding portion, It was realized that glass preforms that were all fused together with deformation were obtained in the previous stage of drawing, and light amplification or nonlinear optical effect was enhanced by simple drawing as described later. An optical waveguide material can be obtained and can be effectively used for a fiber amplifier or a fiber laser. In this case, if a rare earth element such as neodymium, erbium, or ytterbium is used as the dopant material, it is possible to enjoy the advantage that functions such as laser oscillation are imparted to the optical waveguide material. Further, if the diameter of the core portion of the optical waveguide material is increased to about 10 to 100 μm, there is an advantage that a high power laser can be oscillated. Further, if the clad portion of the optical waveguide material has a structure that allows endless single-mode waveguide, that is, the distance between the holes in which the holes of each glass capillary are made thin by drawing is Λ, When the hole diameter is d, a clad structure satisfying d / Λ ≦ 0.43 can enjoy the advantage that the oscillated laser becomes single-mode light without disturbance.

  In particular, according to the above configuration, the outer peripheral surface of the glass preform is in the radial direction due to the fact that each component such as the glass outer tube and the glass capillary are all fused together with deformation. Even if the outer diameter of the glass preform is unevenly deformed and the outer peripheral surface is not a perfect circle or has a wavy shape, the outer diameter accuracy of the glass preform is reduced. Since grinding or polishing is performed, it is possible to prevent problems such as a decrease in the quality of the optical waveguide material, and hence a loss of input optical power from the source and a decrease in output. That is, only by performing fusion accompanied by deformation, radial shrinkage deformation, roundness deviation, and wavy shape, etc. that occurred on the outer peripheral surface of this glass preform are ground or polished. Thus, it is possible to obtain a perfect circular outer peripheral surface which is corrected and smooth and has no variation. An optical waveguide material obtained by drawing a glass preform having an excellent outer diameter accuracy as described above is also necessarily a smooth and perfectly round outer peripheral surface (substantially similar to a glass preform). Outer peripheral surface). Therefore, when this optical waveguide material is fitted to a connection component on the basis of the outer diameter and connected to other components, the fitting between the connection component and the optical waveguide material is less likely to occur, and the fitting is performed smoothly. It is possible to reduce the connection loss or waveguide loss, and when this optical waveguide material is used for fiber amplifiers and fiber lasers, the loss of input optical power from the source can be suppressed and the output is reduced. Such problems are less likely to occur. Further, by grinding or polishing the outer peripheral portion of the glass preform, the surface roughness (for example, the ten-point average roughness Rz) of the outer peripheral surface is made smaller than that of the unground or unpolished surface to obtain a mirror surface. Therefore, the generation of cracks on the outer peripheral surface due to heating during drawing can be suppressed, and the generation of foreign matters such as devitrified materials on the outer peripheral surface can be reduced.

  In this case, when the glass capillary and the glass rod are made of multicomponent glass, preferably borosilicate glass or soda lime glass, glass preform molding or optical waveguide material drawing molding can be performed at low temperature. Deterioration due to heat of the equipment is reduced, or manufacture with simple molding equipment is possible, and the cost required for molding can be reduced. In addition, since the Danner method and the downdraw method, which are general manufacturing methods, can be adopted, various forms of glass preforms can be easily or inexpensively manufactured, and thus various forms can be obtained. The glass preform can be easily obtained, so the periodic arrangement of the holes can be easily controlled at low temperature, thereby controlling the nonlinear optical effect and dispersion characteristics of the optical waveguide material. Can be easily performed.

  In the above configuration, it is preferable that the glass outer tube, the plurality of glass capillaries, and the at least one glass rod or glass capillary do not have any gaps therebetween.

  In this way, in the glass preform, only the vacancies of the constituent parts that were glass capillaries are periodically arranged, and there are no voids in other parts. As a matter of course, in the optical waveguide material, only the portion of the glass capillary component that was a hole is periodically arranged as a narrow hole, and other voids (interstitial sites) are present. No longer. Therefore, improvement in performance such as light propagation characteristics in the optical waveguide material can be expected, and an optical waveguide material capable of exhibiting excellent functions can be provided. Moreover, if there are no gaps between the glass capillaries at the glass preform stage, an optical waveguide material having no interstitial site can be obtained even if the heating temperature during drawing is kept low. Therefore, it is possible to facilitate drawing molding or simplify molding equipment.

  Said structure WHEREIN: It is preferable that the said outer peripheral part is ground or grind | polished on the basis of the glass rod or glass capillary which forms a core part.

  In this way, the glass preform and thus the core portion of the optical waveguide material can be surely positioned at the center in the radial direction, so that excellent concentricity can be secured, and the above-mentioned outer diameter accuracy and roundness can be ensured. When the optical waveguide material is connected to other parts on the basis of the outer diameter, it is possible to suppress the misalignment of both at the connection surface and to minimize the connection loss or waveguide loss. Can be reduced. In addition, when this optical waveguide material is used for fiber amplifiers and fiber lasers, it is possible to more accurately avoid problems such as loss of input optical power from the source and reduction in output. Become

  In this case, at least one end of the glass capillary may be sealed, and at least one end may be opened.

  That is, when the glass preform is drawn, even if the tip (lower end) of the glass capillary is open before drawing, the tip of the glass capillary is sealed at the time of drawing. Therefore, when at least one end of the glass capillary is sealed as in the above one example, if the sealed side is the rear end (upper end) and the other side is the leading end, Since the gas is trapped in the glass capillary holes and cannot escape, the size of the holes and the cross-sectional shape of the holes are not easily affected by atmospheric pressure. Inconveniences such as crushing will not occur. On the other hand, when at least one end of the glass capillary is open as in the other example above, if the open side is the rear end and the other side is the front end, the rear end By changing the pressure in the pores of the glass capillary through the open portion (pressurization or depressurization), the pore diameter can be adjusted to a desired size.

  The method according to the present invention, which was created to solve the above technical problem, is used for drawing an optical waveguide material having a cladding portion and a core portion, and the cladding portion is formed in the inner hole of the glass outer tube. A plurality of glass capillaries to be filled with at least one glass rod or glass capillary forming a core portion, and glass capillary vacancies are periodically arranged in a cross section perpendicular to the axis. In the manufacturing method of a glass preform to be formed, at least one glass rod or glass capillary forming the core portion is made of a dopant material doped, and the glass outer tube and the plurality of glasses All of the capillary and the at least one glass rod or glass capillary are mutually deformed by heating. A fusion step of wearing and is characterized in that it comprises a polishing step of grinding or polishing the outer circumferential portion after the execution of said fusing step.

  According to such a method, since the glass rod or glass capillary doped with the dopant material is used to form the core portion, the optical amplification effect or the nonlinear optical effect is enhanced, and it is suitable for the fiber amplifier and the fiber laser. Thus, a glass preform that is a base material for the optical waveguide material that can be used for the above-mentioned process is obtained as a glass molded body integrated by fusion at the stage prior to drawing. Then, the outer peripheral surface of the glass preform is caused by the fact that each component composed of the glass outer tube and the plurality of glass capillaries is fused together with deformation by executing the fusion process. Even if the outer diameter accuracy deteriorates due to non-uniform shrinkage deformation in the radial direction and the outer peripheral surface is not a perfect circle or becomes a wavy shape, By grinding or polishing the outer peripheral portion, these deficient shapes are corrected, and it becomes possible to obtain a perfect circular outer peripheral surface that is smooth and free from variations. Therefore, an optical waveguide material obtained by drawing a glass preform having such an excellent outer diameter accuracy is also necessarily a smooth and round outer peripheral surface (substantially similar to a glass preform). Of the outer peripheral surface) and can be suitably used for fiber amplifiers and fiber lasers. And about the structure corresponding to these, the effect similar to the matter already stated can be enjoyed.

  In the above method, in the fusing step, the glass outer tube, the plurality of glass capillaries, and the at least one glass rod or glass capillary are all made to have no gap. It is preferable.

  In this way, by performing the fusion process, only the vacancies of the constituent parts that were glass capillaries are periodically arranged in the glass preform, and there are no voids in other parts. . And about the structure corresponding to this, the effect similar to the matter already stated can be enjoyed.

  In this case, in the fusing step, a plurality of glass capillaries forming a cladding portion and at least one glass rod or glass capillary forming a core portion are arranged in a glass outer tube having a sealed bottom portion. It is preferable to heat the glass outer tube while maintaining the inside of the glass outer tube in a reduced pressure state. In this way, even if the cross-sectional shape perpendicular to the axis (cross-sectional shape perpendicular to the axis) of the outer peripheral surface of the glass capillary or glass rod is circular, the glass capillary and the glass rod are mutually connected, and each glass capillary is When the glass capillaries are fused together with deformation, there is no gap between the glass capillaries and the glass rods and between the glass capillaries. At the same time, the glass capillaries are aligned before fusing. These glass capillaries are automatically arranged in the most stable and intimate state even if they are not arranged at the same position, and a glass preform having a periodic arrangement structure with a high regularity in the cross section perpendicular to the axis can be easily obtained. Become.

  In the above method, after the fusion process is performed, a cutting process is performed in which at least one end is cut in a direction orthogonal to the axis, and then the polishing is performed on the basis of the glass rod or the glass capillary that forms the core part. It is preferable to execute the process.

  In this way, by performing the cutting process, the constituent parts of the core part and the cladding part are exposed to the cut surface, so that the position of the glass rod part serving as the core part or the hole of the glass capillary can be clearly obtained. Thus, the center position when the outer peripheral portion is ground can be strictly specified. In addition, if the polishing process is performed on the outer peripheral portion with reference to the component portion of the core portion in such a state, the core portion of the glass preform and thus the optical waveguide material can be surely positioned at the radial center. It becomes. And about the structure corresponding to this, the effect similar to the matter already stated can be enjoyed.

  In the above method, it is preferable that the outer peripheral portion is ground or polished into a perfect circle in the polishing step.

  In this way, the roundness of the optical waveguide material obtained by drawing the glass preform is improved as much as possible. When this optical waveguide material is connected to other parts on the basis of the outer diameter, the connection loss is reduced. Or it becomes possible to reduce waveguide loss more reliably.

  In the above method, it is preferable to seal one or both ends of the glass capillary after the polishing step.

  In this way, the pores of the glass capillary can be made to have an appropriate diameter when the glass preform is drawn. And about the structure corresponding to this, the effect similar to the matter already stated can be enjoyed.

  In this case, it is preferable that the optical waveguide material is produced by drawing a glass preform having the above-described configuration, and holes are periodically arranged in a cross section orthogonal to the axis.

  According to such an optical waveguide material, it is possible to enjoy various advantages such as improvement in roundness and outer diameter accuracy as described above, and it is possible to perform good connection with other components. When used in a fiber amplifier or a fiber laser, it is possible to effectively reduce the input optical power loss from the source and the output drop.

  The optical waveguide material is preferably produced by drawing a glass preform obtained by the above-described manufacturing method, and holes are preferably periodically arranged in a cross section perpendicular to the axis.

  Even with such an optical waveguide material, it is possible to enjoy various advantages such as improved roundness and outer diameter accuracy as described above, and it is possible to perform a good connection with other components, etc. When used in a fiber amplifier or a fiber laser, it is possible to effectively reduce the input optical power loss from the source and the output drop.

  As described above, according to the present invention, each component including the glass rod or glass capillary forming the core portion doped with the dopant material, the glass outer tube, and the plurality of glass capillaries forming the cladding portion. However, it is possible to obtain a glass preform that is fused together with deformation in the previous stage of drawing, so that light amplification with enhanced optical amplification or nonlinear optical effect can be achieved by simple drawing. A wave material can be obtained and can be suitably used for a fiber amplifier or a fiber laser. In addition, all the above-described components are fused together with deformation, and the outer peripheral surface of the glass preform shrinks and deforms unevenly in the radial direction, and the outer peripheral surface is not a perfect circle or wavy. Even if conditions that cause deterioration of the outer diameter accuracy are obtained due to the shape, etc., the outer periphery of this glass preform is ground or polished, so the shape and properties of this outer periphery are incomplete. Is appropriately corrected, and it becomes possible to obtain a perfect outer peripheral surface that is smooth and has no variation. In addition, an optical waveguide material obtained by drawing the glass preform has a perfectly circular outer peripheral surface that is inevitably smooth and does not vary. When connecting to other parts by fitting with connection parts, it becomes difficult for rattling to occur between the connection parts and the optical waveguide material, and the fitting can be smoothly performed, resulting in connection loss or waveguide. Loss and the like can be reduced, and when this optical waveguide material is used for a fiber amplifier or a fiber laser, problems such as loss of input optical power from the source and a decrease in output are less likely to occur. Furthermore, by grinding or polishing the outer peripheral portion of the glass preform, the outer peripheral surface can be made into a mirror surface, so that it is possible to suppress the occurrence of cracks on the outer peripheral surface due to heating during wire drawing and to reduce the loss on the outer peripheral surface. Occurrence of foreign matters such as transparent materials is reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 3 are schematic views showing a process of manufacturing a glass preform according to an embodiment of the present invention. FIG. 4 shows a process of drawing an optical waveguide material by drawing the glass preform. FIG.

  FIG. 1 exemplifies a state in which a first stage process for producing a glass preform is being performed. As shown in FIG. 1 (a), a glass preform is prepared by first, one cylindrical glass rod 2 and a plurality (96) in the inner hole of the glass outer tube 1 whose bottom is sealed. The cylindrical glass capillaries 3) are inserted in a random arrangement state. At this time, as shown in FIG. 1B, the inner hole of the glass outer tube 1 is substantially filled with the glass rod 2 and the glass capillary 3, and a plurality of glass rods 2 are provided. It is inserted so that it may be located in the approximate center part of this glass capillary 3. The glass rod 2 is doped with 1.2% by mass of neodymium as a dopant material. The dopant material is not limited to neodymium, and may be erbium, ytterbium, or the like, and the doped amount is not limited to 1.2% by mass, but 2% by mass. The following is sufficient.

  In this case, the glass outer tube 1, glass rod 2, and glass capillary 3 are all made of soda lime glass (or alkali borosilicate glass), and the glass outer tube 1 has an outer diameter of 24 mm and an inner diameter of 11. The glass capillary 3 has an outer diameter of 1.0 mm and an inner diameter of 200 μm, and the glass rod 2 has an outer diameter of 3.0 mm. At this point, the glass capillary 3 is preferably sealed at both ends.

  Next, as shown in FIG. 2 (a), as a fusion process, the inside of the glass outer tube 1 filled with the glass rod 2 and the glass capillary 3 is decompressed to −750 mmHg using a vacuum pump outside the figure, Further, while maintaining the vacuum pressure, the glass outer tube 1 is sequentially heated from the bottom toward the opening end to 710 ° C. by the heating device 4 to cause shrinkage deformation in the radial direction. In this case, due to the contraction deformation accompanying the initial heating of the glass outer tube 1, the plurality of glass capillaries 3 are regularly aligned as shown in FIG. Further, when the glass outer tube 1 is further heated from such a state, the glass capillary 3 and the glass rod 2 are mutually fused and the glass capillaries 3 are mutually fused with deformation. The glass outer tube 1 and each glass capillary 3 are also fused. Further, as this fusion proceeds, there is no gap between all of the glass outer tube 1, each glass capillary 3, and the glass rod 2, and a portion corresponding to a hole in each glass capillary 3 in the cross section perpendicular to the axis. A prototype of a glass preform having a periodic arrangement structure with high regularity is obtained.

  From such a stage, after the glass preform prototype is slowly cooled to room temperature and returned to normal pressure, both ends of the prototype are cut in the direction perpendicular to the axis in the cutting process, and then correspond to the core portion of the optical waveguide material. A polishing step is performed using an outer peripheral grinding machine while rotating the glass preform around a portion to be performed (portion corresponding to the glass rod 2), and the outer peripheral portion is ground or polished, as shown in FIG. Such a glass preform 5 is obtained.

  This glass preform 5 has a non-porous portion 2a corresponding to the core portion (portion corresponding to the glass rod 2) at an exact position on the central axis of the cylindrical body 5a made of glass, A plurality of holes 6 (holes 6 corresponding to the holes of each glass capillary 3) are periodically arranged with high regularity in the portion 3a corresponding to the cladding part.

  And the outer peripheral surface 5x of this glass preform 5 is made into a smooth surface free of undulation or the like and excellent in roundness and concentricity by grinding or polishing as shown in the region indicated by symbol A. It is considered as a circumferential surface. More specifically, the glass preform 5 has a difference between the maximum diameter and the minimum diameter of the outer peripheral surface 5x of 2 to 8 μm, and in this embodiment, 5 μm. On the other hand, when the outer peripheral surface of the glass preform 5 is not ground or polished, the outer peripheral surface has a wavy shape and the difference between the maximum diameter and the minimum diameter is about 60 μm. .

  Furthermore, the glass preform 5 according to this embodiment is drawn in a drawing while being pulled by a roller 7 as shown in FIG. 4 while being put in an electric furnace. An unprocessed optical waveguide material 8 having a diameter of 4.4 μm, a distance between each hole of 11.5 μm, and a core part diameter of 37 μm is obtained. The shape of the optical waveguide material 8 in a cross section perpendicular to the axis is substantially similar to the shape shown in FIG. 3, and the eccentricity between the core portion and the outer circle is 0.5 to 1.5 μm, and in this embodiment, 1 μm. ing. On the other hand, the amount of eccentricity between the core portion and the outer peripheral circle of the optical waveguide material obtained by drawing the glass preform whose outer peripheral surface is not ground or polished in the same manner is about 4.3 μm.

FIG. 1 (a) is a schematic perspective view showing a state in which an initial step for producing a glass preform according to an embodiment of the present invention is being performed, and FIG. 1 (b) is in the middle of producing the glass preform. It is a schematic plan view which shows the state of. FIG. 2 (a) is a schematic perspective view showing a state in which a fusing process is performed when producing a glass preform according to an embodiment of the present invention, and FIG. 2 (b) is a production of the glass preform. It is a schematic plan view which shows the state in the middle. It is a schematic plan view which shows the end surface of the finished product of the glass preform which concerns on embodiment of this invention. It is a schematic perspective view which shows the state which is drawing drawing of the optical waveguide material using the glass preform which concerns on embodiment of this invention. It is a schematic plan view which shows the end surface of the conventional glass preform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass outer tube 2 Glass rod 3 Glass capillary 5 Glass preform 5x The outer peripheral surface (outer peripheral part) of a glass preform
8 Optical waveguide materials

Claims (12)

A plurality of glass capillaries for forming a cladding portion in an inner hole of a glass outer tube, and at least one glass rod for forming a core portion, which are used for drawing an optical waveguide material having a cladding portion and a core portion. Alternatively, in a glass preform that is filled with a glass capillary and has a shape in which the holes of the glass capillary are periodically arranged in a cross section orthogonal to the axis,
At least one glass rod or glass capillary forming the core portion is doped with a dopant material, the glass outer tube, the plurality of glass capillaries, and the at least one glass rod or glass capillary However, the glass preform is characterized in that all are fused together with deformation, and the outer periphery thereof is ground or polished.   2. The glass outer tube, the plurality of glass capillaries, and the at least one glass rod or glass capillary do not have any gaps therebetween. Glass preform.   The glass preform according to claim 1 or 2, wherein the outer peripheral portion is ground or polished with reference to a glass rod or a glass capillary forming the core portion.   The glass preform according to claim 1, wherein at least one end of the glass capillary is sealed.   The glass preform according to claim 1, wherein at least one end of the glass capillary is open. A plurality of glass capillaries for forming a cladding portion in an inner hole of a glass outer tube, and at least one glass rod for forming a core portion, which are used for drawing an optical waveguide material having a cladding portion and a core portion. Alternatively, in the method for producing a glass preform, which is filled with a glass capillary and has a form in which holes of the glass capillary are periodically arranged in a cross section orthogonal to the axis,
As the at least one glass rod or glass capillary forming the core portion, one doped with a dopant material is used, and the glass outer tube, the plurality of glass capillaries, and the at least one glass A fusion step of fusing all the rods or glass capillaries together with deformation by heating, and a polishing step of grinding or polishing the outer periphery after the fusion step is performed, A method for manufacturing a glass preform.   In the fusing step, the glass outer tube, the plurality of glass capillaries, and the at least one glass rod or glass capillary are all free from voids. The manufacturing method of the glass preform of Claim 6.   After performing the fusion process, perform a cutting process of cutting at least one end in a direction orthogonal to the axis, and then perform the polishing process with reference to a glass rod or a glass capillary that forms the core. The method for producing a glass preform according to claim 6 or 7, wherein:   The glass preform according to any one of claims 6 to 8, wherein in the polishing step, the outer peripheral portion is ground or polished into a perfect circle.   The glass preform manufacturing method according to claim 6, wherein one end or the other end of the glass capillary is sealed after the polishing step.   An optical waveguide material produced by drawing the glass preform according to any one of claims 1 to 5, wherein holes are periodically arranged in a cross section perpendicular to the axis.   A glass preform obtained by the manufacturing method according to any one of claims 6 to 10 is produced by drawing, and holes are periodically arranged in a cross section perpendicular to the axis. Optical waveguide material.