JP3863025B2 - Manufacturing method of double clad fiber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method of manufacturing a double-clad fiber having a core extending in the fiber central axis direction, a first cladding covering the periphery of the core, and a second cladding covering the periphery of the first cladding.
[0002]
[Prior art]
  Conventionally, a double clad fiber is known as an optical fiber used for a fiber laser or a fiber amplifier. This double clad fiber is made of, for example, quartz (SiO 2) doped with a rare earth element which is an excitation photoactive material.₂) Core made of SiO and covering the core₂The first clad is made of, and the second clad made of, for example, an ultraviolet curable resin covering the periphery of the first clad. In the double-clad fiber, while the signal light is propagated in the core, the excitation light for exciting the signal light is propagated in the core and the first cladding, so that the excitation light crosses the core every time the excitation light crosses the core. The rare earth element is activated, and as a result, the signal light is amplified.
[0003]
  By the way, when the interface shape between the first clad and the second clad in the cross section of the fiber is formed concentrically with the core, a component that circulates around the core, that is, a so-called skew component is generated in the excitation light. To do. Since the light of this skew component hardly passes through the core, it does not activate the rare earth element of the core. For this reason, when the skew component increases, there is a problem that the signal light propagating in the core cannot be greatly amplified.
[0004]
  Therefore, the interface shape of the first and second claddings may be formed in various shapes other than a circular shape, for example, a polygonal shape such as a quadrangle, or an asymmetric shape with respect to the central axis of the core. Proposed. By doing so, since the generation of skew light is suppressed, the probability that the excitation light crosses the core is increased, thereby improving the above problem.
[0005]
[Problems to be solved by the invention]
  By the way, as a method for manufacturing a double clad fiber in which the interface shape between the first and second clads as described above is formed in a shape other than a circular shape, for example, as shown in FIG. The base material 26 is a core and a first clad of a double clad fiber), and the outer peripheral surface of the base material 26 is melt-deformed or polished by the flame of the burner 8 to obtain a desired crossing. A method for forming a surface shape has been proposed.
[0006]
  However, in the method using such a burner flame, water is generated during the treatment, and this water penetrates into the inside from the outer peripheral surface of the base material 26. For this reason, OH groups remain in the first clad of the completed double-clad fiber, which increases the absorption loss of pumping light, which leads to a decrease in pumping efficiency.
[0007]
  In order to suppress the generation of skew light in a double clad fiber, it is effective to make the interface shape of the first and second clads asymmetric with respect to the core central axis as described above. When such an asymmetric interface shape is used, there is a disadvantage that it becomes difficult to connect the double clad fiber and a normal optical fiber made of a core and a clad. That is, when the double-clad fiber and a normal optical fiber are fusion spliced, the connection end of each fiber is melted. At this time, the interface shape of the first and second clads is asymmetric with respect to the core central axis. If present, the surface tension of the melted first clad portion is unevenly distributed in the circumferential direction with respect to the core. As a result, the core is pulled and moved in the radial direction, and it becomes difficult to match the core axes of the double clad fiber and the normal optical fiber. As a result, connection loss may increase.
[0008]
  Therefore, in order to reduce the connection loss, it is preferable that the interface shape of the first and second claddings is symmetric with respect to the fiber center axis. However, in the method of forming the interface shape by a burner flame, It is difficult to form a symmetrical shape with respect to the central axis.
[0009]
  The present invention has been made in view of such circumstances, and an object thereof is to make it possible to easily manufacture a double-clad fiber with enhanced pumping efficiency by preventing the generation of skew light. It is in.
[0010]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides a fiber preform by disposing a rod-like material on the outer peripheral surface of a base material constituting a core and a first clad of a double clad fiber. The interface shape of the first and second clads of the clad fiber is different from the circular shape.
[0011]
  Specifically, the first invention is a method of manufacturing a double-clad fiber having a core extending in the fiber central axis direction, a first cladding covering the periphery of the core, and a second cladding covering the periphery of the first cladding. Is targeted.
[0012]
  A columnar base material constituting the core and the first cladding in the double-clad fiber, and at least one bowl-shaped material that is in contact with the outer peripheral surface of the base material and disposed along the longitudinal direction of the base material; A step of producing a fiber base material by heating, a step of drawing and drawing the produced fiber base material into a fiber shape, and coating a resin around the drawn fiber, whereby the double clad fiber Forming a second cladding inThe rod-shaped material is a barIs.
[0013]
  In this way, the optical fiber preform is arranged along the longitudinal direction of the base material in a state of being in contact with the outer peripheral surface of the base material constituting the core and the first cladding of the double clad fiber. At least one bowl-shaped material(Bar material)When this fiber preform is heated and stretched and drawn into a fiber shape, the cross section of the drawn fiber melts and integrates with the outer peripheral surface of the base material, so that a circular shape is formed. And have a different shape.
[0014]
  Then, by coating resin around the fiber, a double clad fiber is manufactured in which the interface shape of the first and second clads is different from the circular shape.
[0015]
  As described above, water can be generated when the interface shape of the first and second claddings is formed by the burner flame in the production of the double clad fiber, whereas in the present invention, the above-mentioned without using the burner flame. Since the interface shape is formed, the water is not generated. As a result, the interface shape of the first and second claddings is formed in a shape different from the circular shape, so that the skew component of the excitation light propagating in the first cladding is suppressed, the excitation efficiency is improved, and the double Since water is not generated during the production of the clad fiber, the absorption loss of the excitation light is reduced, and the excitation efficiency is further improved.
[0016]
  The second invention is directed to a method for producing a double-clad fiber, and at least one hook-like material is provided in the longitudinal direction of the substrate on the outer peripheral surface of a columnar substrate serving as a core and a first cladding in the double-clad fiber. The fiber base material is manufactured by arranging the two together and the fiber base material is manufactured, and the fiber base material manufactured is heated and stretched to be drawn into a fiber shape. Forming a second clad in the double clad fiber by coating the periphery with a resin.The rod-shaped material is a barIs.
[0017]
  A third invention is directed to a method for producing a double clad fiber, and includes a columnar base material constituting the core and the first clad in the double clad fiber, an abutting surface of the base material, and a length of the base material. A step of producing a fiber preform with at least one cage-like material disposed along the direction, and heating and stretching the produced fiber preform, thereby integrating the base material and the cage-like material. A step of drawing into a fiber shape, and a step of forming a second cladding in the double-clad fiber by coating a resin around the drawn fiberThe rod-shaped material is a barIs.
[0018]
  That is, in the second aspect of the invention, the fiber base material has a bowl-shaped material on the outer peripheral surface of the base material.(Bar material)In the third invention, the fiber base material is drawn when the fiber base material is drawn.(Bar material)Are integrated. In any method, a double clad fiber with improved pumping efficiency can be easily manufactured.
[0019]
  A fourth invention is directed to a method for producing a double clad fiber, and at least one hook-like material is provided in the longitudinal direction of the base material on the outer peripheral surface of a columnar base material to be a core and a first clad in the double clad fiber. The fiber base material is manufactured by arranging the two together and the fiber base material is manufactured, and the fiber base material manufactured is heated and stretched to be drawn into a fiber shape. Forming a second clad in the double clad fiber by coating a resin around it, and forming the fiber preform using the saddle-like material as a hollow tube, After the tube material is integrated, the hollow portion of the tube material is opened radially outward of the fiber preform by removing the vicinity of the outer peripheral edge of the fiber preform. It is an.
[0020]
  That is, by removing the vicinity of the outer peripheral edge of the fiber base material in which the base material and the tube material are integrated, the hollow portion of the pipe material is opened outward in the radial direction of the fiber base material, and the outer peripheral surface of the fiber base material is The hollow portion of the tube material has a shape different from the circular shape. In addition, what is necessary is just to grind | polish, for example using a grinder, in order to remove the outer periphery vicinity of a fiber preform | base_material.
[0021]
  In the double clad fiber in which this fiber preform is drawn in a fiber shape and resin-coated on the fiber preform, the interface shape between the first clad and the second clad is formed in a shape different from the circular shape. In this way, it is possible to manufacture a double clad fiber by forming an interface shape without using a burner flame.
[0022]
  A fifth invention is directed to a method for producing a double clad fiber, and includes a columnar base material constituting the core and the first clad in the double clad fiber, an abutting surface of the base material, and a length of the base material. A step of producing a fiber preform with at least one hook-like material arranged along a direction, a step of drawing the fiber preform by heating and stretching the produced fiber preform, and the drawn fiber A step of forming a second clad in the double clad fiber by coating a resin around the core, and using the bowl-shaped material as a hollow tube material, and melting and integrating the base material and the tube material In addition, the hollow portion of the tube material is crushed.
[0023]
  By crushing the hollow portion of the tube material, the same effects as the first to third inventions can be obtained.
[0024]
  Here, it is preferable to arrange the plurality of bowl-shaped materials on the outer peripheral surface of the base material so as to be symmetric with respect to the central axis of the base material.
[0025]
  By doing so, the interface shape of the first and second clads in the double clad fiber is formed symmetrically with respect to the fiber center axis. As a result, when the double clad fiber is fusion spliced, the surface tension of the melted first clad portion is uniformly distributed in the circumferential direction with respect to the core, so that the core does not move. And a normal optical fiber can be easily fused.
[0026]
  Further, the interface shape of the first and second claddings can be made symmetric with respect to the fiber central axis simply by arranging the saddle-like material so as to be symmetric with respect to the central axis of the substrate. Therefore, the interface shape can be formed very easily as compared with the case where the interface shape is formed by the burner flame.
[0027]
  The plurality of bowl-shaped materials may be densely arranged on the outer peripheral surface of the substrate.
[0028]
  By carrying out like this, arrangement | positioning of a bowl-shaped material with respect to a base material can be performed easily. In addition, when the bowl-shaped material is densely arranged on the outer peripheral surface of the base material, the size of the bowl-shaped material (diameter is set so that the bowl-shaped material is arranged symmetrically with respect to the central axis of the base material. ) And the size (diameter) of the base material in advance, the saddle-shaped material is automatically placed in the center of the base material only by densely arranging the saddle-shaped material on the outer peripheral surface of the base material. Since it is arranged symmetrically with respect to the axis, the formation of the interface shape becomes extremely easy.
[0029]
  The bar may have a circular cross section or a semicircular cross section.Since such a bar having a circular cross section, a bar having a semicircular cross section, and a pipe are each a general-purpose material, the manufacturing cost of the double clad fiber can be reduced.
[0030]
【The invention's effect】
  As described above, according to the method for producing a double-clad fiber in the present invention, the base material andBar or pipeBy forming the fiber preform from the above, the interface shape of the first and second clads of the double clad fiber is formed without using a burner flame, so that no water is generated during the production of the double clad fiber. Further, since the interface shape of the first and second claddings is formed in a shape different from the circular shape, the skew component of the excitation light propagating in the first cladding is suppressed, and the absorption loss of the excitation light is reduced. In combination, the excitation efficiency can be further improved.
[0031]
  In particular, the interface shape of the first and second clads in the double clad fiber is symmetrical with respect to the fiber central axis only by arranging the saddle-like material so as to be symmetric with respect to the central axis of the substrate. Therefore, a double clad fiber with reduced connection loss can be easily manufactured.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0033]
  <First Embodiment>
  FIG. 1 shows a cross section of a double clad fiber 1 according to the first embodiment, which includes a core 11 through which signal light propagates and pumping light that covers the periphery of the core 11 and excites the signal light. A first clad 12 that propagates and a second clad 13 that covers the periphery of the first clad 12 are provided.
[0034]
  The core 11 is made of SiO.₂A single-mode core or a substantially single-mode core made of fiber and arranged so as to extend in the direction of the fiber center axis at the approximate center of the fiber. The core 11 is doped with Ge so as to have a refractive index higher than that of the first cladding 12, and the signal light propagating in the core 11 is amplified by the excitation light propagating through the first cladding 12. As described above, rare earth elements (such as Er, Yb, and Nd) are doped.
[0035]
  The first cladding 12 covers the periphery of the core 11 and extends in the fiber central axis direction. The first cladding 12 is pure SiO₂It is formed by.
[0036]
  The second clad 13 extends in the fiber central axis direction while covering the outer periphery of the first clad 12, and the second clad 13 is more than the second layer 12 b of the first clad 12. For example, it is formed of an acrylic ultraviolet curable resin doped with fluorine (F) that lowers the refractive index so that the refractive index is lowered. The second cladding 13 is not limited to the ultraviolet curable resin, and may be formed of a low refractive index material such as other resins.
[0037]
  And the interface of the 1st clad 12 and the 2nd clad 13 in the cross section of the above-mentioned double clad fiber 1 is formed in the shape of a wave, and, thereby, the cross section shape of the interface has a substantially flower shape. The interface shape is formed so as to be symmetric with respect to the fiber center axis.
[0038]
  By doing so, the skew component of the excitation light propagating in the first cladding 12 can be suppressed as compared with the case where the interface shape of the first and second claddings 12 and 13 is formed in a circular shape. That is, the excitation light propagating in the first cladding 12 is prevented from circulating around the core, and the probability that the excitation light crosses the core 11 is increased. For this reason, the excitation efficiency of the double clad fiber 1 can be increased.
[0039]
  In the double clad fiber 1, the diameter of the substantially intermediate position of the irregularities at the corrugated interface (see the alternate long and short dash line in the figure) is set to be approximately the same as the diameter (φ125 μm) of a normal optical fiber made of core and clad. ing. As a result, the cross-sectional area of the double clad fiber 1 including the core 11 and the first clad 12 is set to be substantially the same as the cross-sectional area of a normal optical fiber. By doing so, the fusion-splicing between the double clad fiber 1 and a normal optical fiber is facilitated.
[0040]
  That is, when fusion-connecting a pair of fibers, both ends are heated and melted. At this time, if the cross-sectional areas of the two are the same, their heat capacities are the same. be able to. Therefore, by setting the cross-sectional area of the double-clad fiber 1 including the core 11 and the first clad 12 to be substantially the same as the cross-sectional area of the normal optical fiber, When fusion splicing is performed, the connection loss can be reduced.
[0041]
  In addition, when the interface between the first cladding 12 and the second cladding 13 is formed so as to be symmetric with respect to the fiber center, the end of the double-clad fiber 1 is melted for fusion splicing. Further, the surface tension uniformly distributed in the circumferential direction acts on the core 11, thereby preventing the core 11 from moving. Thus, the double clad fiber 1 and the normal optical fiber can be fusion-bonded to each other in a state in which the axis deviation of the core 11 is suppressed, and the connection loss can be reduced.
[0042]
  Next, a method for manufacturing the double clad fiber 1 will be described with reference to FIG. The figure shows a procedure for manufacturing the double clad fiber 1. First, a base material 26 that is a part of the core 11 and the first clad 12 in the double clad fiber 1 is prepared. The base material 26 includes a core portion 21 located at the center thereof and a first clad portion 22 that covers the core portion 21. The core portion 21 is a portion that is converted into a fiber to become the core 11, and is a SiO layer doped with a relatively high concentration of Ge and rare earth elements.₂Form with. The first clad portion 22 is a portion that becomes a part of the first clad 12 as a fiber, and this portion is made of pure SiO 2.₂Form with. Such a base material 26 may be produced by, for example, a CVD method (Chemical Vapor Deposition method), an OVD method (Outside Vapor Deposition method), a VAD method (Vapor-phase Axial Deposition method), or a rod-in tube method.
[0043]
  Next, a large number of rods 24 having a circular cross section are prepared (12 in the example), and the rods 24 are in contact with the outer peripheral surface of the substrate 26. It arrange | positions along a longitudinal direction (refer P11 of the figure). At this time, the rods 24 are densely arranged on the outer peripheral surface of the substrate 26. Here, when the rods 24 are densely arranged on the outer peripheral surface of the substrate 26, the rods 24 are arranged so that the rods 24 are arranged symmetrically with respect to the central axis of the substrate 26. And the diameter of the base material 26 is set, respectively.
[0044]
  Further, each bar 24 may be joined (integrated) to the base material 26 over the entire longitudinal direction, or only both ends of the bar 24 may be attached to the base material 26. You may make it join. Further, the bar 24 may be simply fixed to the base material 26 in a state of being in contact with each other (in this case, when the fiber preform 2 described later is drawn, the bar 24 and the base material 26 Are integrated). In this way, the fiber preform 2 is produced by the base material 26 and the bar material 24.
[0045]
  Next, the fiber preform 2 thus manufactured is heated and stretched and drawn into a fiber shape (see P12 in the figure). By doing so, the rod 24 and the base material 26 are melted and integrated to form the core 11 and the first clad 12 which covers the periphery of the core 11 and whose cross-sectional shape is formed in a substantially flower shape. The fiber 1a is produced.
[0046]
  Then, for example, an ultraviolet curable resin liquid containing F is applied to the periphery of the fiber 1a and is cured by irradiating with ultraviolet rays to form the second clad 13 (see P13 in the figure). . Note that this step may be appropriately changed according to the material constituting the second cladding 13.
[0047]
  In this way, the double clad fiber 1 having the core 11 and the first and second clads 12 and 13 is manufactured, and the double clad fiber 1 in which the interface shape of the first and second clads 12 and 13 is formed in a waveform is manufactured. can do. Thus, in this manufacturing method, instead of forming the cross-sectional shape of the base material 26 by melting or polishing using a burner flame, the bar material 24 is disposed on the outer peripheral surface of the base material 26, thereby Since the cross-sectional shape of the (fiber preform 2) is formed, the double clad fiber 1 can be produced without generating water when a burner flame is used, where water is generated. For this reason, the absorption loss of the excitation light of the manufactured double clad fiber 1 can be reduced.
[0048]
  Moreover, in order to form the interface shape of the 1st clad and the 2nd clad | crud 12 and 13 in the double clad fiber 1 only by arrange | positioning the bar 24 in the outer peripheral surface of the base material 26, when using a burner flame The interface shape can be easily formed, and the interface shape can be easily formed so as to be symmetric with respect to the fiber central axis.
[0049]
  (First modification)
  In the first modification, as shown in FIG. 3A, the fiber base material 3 is configured by disposing the rods 24 one by one without densely arranging them on the outer peripheral surface of the base material 26. To do. Then, the fiber preform 3 is heated and stretched to be drawn into a fiber shape, and a resin is coated around the drawn fiber to produce a double clad fiber 4 (see FIG. 4B).
[0050]
  In the double-clad fiber 4 thus produced, the interface shape between the first clad 12 and the second clad 13 in the cross section is formed in a shape different from the circular shape, so that the skew component of the excitation light is suppressed, Excitation efficiency can be increased.
[0051]
  For example, when the interface between the first and second claddings 12 and 13 is corrugated as in the above-described embodiment, the interface shape may be too complex and the excitation light may be reflected twice at the corrugated interface. . This may increase the loss of excitation light. For this reason, it is conceivable that the interface shape of the first and second claddings 12 and 13 is the same as that of the first modification because the loss of excitation light is reduced.
[0052]
  The double clad fiber 4 is also formed so that the interface shape of the first and second clads 12 and 13 is symmetric with respect to the fiber center axis. The incoming connection can be easily performed.
[0053]
  Moreover, since this double clad fiber 4 can also be manufactured by the base material 26 and the rod material 24 arrange | positioned on the outer peripheral surface of this base material 26, the double clad fiber 4 which reduced the absorption loss of excitation light It can be.
[0054]
  (Second modification)
  As shown in FIG. 4, the second modified example is an example in which the fiber preform 5 is manufactured using a rod 25 having a semicircular cross-sectional shape.
[0055]
  That is, a large number of rods 25 having a semicircular cross section are prepared (12 in the illustrated example), and the rods 25 are in contact with the outer peripheral surface of the substrate 26. It arrange | positions along a longitudinal direction and the fiber preform | base_material 5 is produced. At this time, the rods 25 are densely arranged on the outer peripheral surface of the substrate 26. In the illustrated example, the diameter of the bar 25 is set to be substantially the same as the diameter of the bar 24 having a circular cross section, and the diameter of the base 26 is made larger than that of the first embodiment. However, the diameter of the rod 25 having a semicircular cross section and the diameter of the base material 26 are not limited to this, and the cross-sectional areas of the core 11 and the first cladding 12 are usually the same in the manufactured double-clad fiber 1. What is necessary is just to set suitably so that it may become substantially the same as the cross-sectional area of this optical fiber.
[0056]
  Then, if this fiber preform 5 is heated and stretched and is coated with resin, a double clad fiber 1 in which the interface between the first and second clads 12 and 13 is formed in a waveform as shown in FIG. 1 is manufactured. can do.
[0057]
  The cross-sectional shape of the rods 24 and 25 used for the production of the fiber preforms 2, 3, and 5 is not limited to a circular shape or a semicircular shape, but may be a polygonal shape such as a triangle or a quadrangle. Various shapes are possible. However, the rods 24 and 25 having a circular cross-section or semicircular shape are general-purpose materials and are easy to handle, and using them has the advantage that the manufacturing cost of the double-clad fiber 1 can be reduced.
[0058]
  Second Embodiment
  FIG. 5 shows a cross-section of a double-clad fiber 6 manufactured by the method for manufacturing a double-clad fiber according to the second embodiment. This second embodiment differs from the first embodiment in that a bowl-shaped material is used. The double-clad fiber 6 is manufactured using the hollow tube material 27 as follows.
[0059]
  The double clad fiber 6 is also formed so that the interface between the first clad 12 and the second clad 13 in the cross section is corrugated, and the interface shape is symmetric with respect to the fiber center axis. Has been.
[0060]
  Further, in the double clad fiber 1, the diameter of the substantially intermediate position of the irregularities at the corrugated interface (see the dashed line in the figure) is set to be approximately the same as the diameter of a normal optical fiber. As a result, the cross-sectional area of the double clad fiber 1 including the core 11 and the first clad 12 is set to be substantially the same as the cross-sectional area of a normal optical fiber.
[0061]
  In addition, the same code | symbol is attached | subjected about the same member as the said 1st Embodiment, and the detailed description is abbreviate | omitted.
[0062]
  Next, a method for manufacturing the double clad fiber 6 will be described with reference to FIG. First, a large number of cylindrical pipe members 27 (12 in the illustrated example) are prepared and arranged so as to be dense on the outer peripheral surface of the base material 26 (see P21 in the figure).
[0063]
  Next, the base material 26 and the tube material 27 are melted and integrated to produce the fiber preform 7. At this time, by hollowing out the space surrounded by the outer peripheral surface of the base material 26 and the pair of adjacent pipe materials 27, the hollow portions are formed in the circumferential direction in the vicinity of the outer peripheral surface. The fiber preform 7 arranged side by side is manufactured (see P22 in the figure).
[0064]
  Then, the vicinity of the outer peripheral edge of the fiber preform 7 is polished and removed by a grinder (for example, polished to a position indicated by a one-dot chain line in the figure), so that each hollow portion in the fiber preform 7 is radial. It is opened outward (see P23 in the figure).
[0065]
  In this way, the polished fiber preform 7 is heated and stretched to be drawn into a fiber shape, and the drawn fiber is coated with a resin to form the second clad 13 to manufacture the double clad fiber 6 (same as above). (See P24 in the figure).
[0066]
  Thus, even if the tube material 27 is used instead of the rods 24 and 25, the double clad fiber 6 in which the interface between the first and second claddings 12 and 13 is formed in a waveform can be manufactured.
[0067]
  Moreover, since such a pipe material 27 is a general-purpose material, the double clad fiber 6 can be manufactured at low cost.
[0068]
  However, compared with the manufacturing method according to the first embodiment, since the polishing step P23 is required, there is a disadvantage that the number of steps increases.
[0069]
  For example, when the base material 26 and the tube material 27 are melted and integrated, if the hollow portion of the tube material 27 is crushed, the polishing step P23 can be omitted. For example, if the base material 26 and the tube material 27 are heated and integrated in a state where the hollow portion of the tube material 27 is decompressed, the hollow portion of the tube material 27 can be crushed.
[0070]
  Although illustration is omitted, the polishing step P23 can be omitted even if, for example, a tube material 27 is preliminarily divided into half and disposed on the outer periphery of the base material 26 to produce a fiber preform. .
[0071]
  <Other embodiments>
  In addition, this invention is not limited to the said embodiment, Other various embodiment is included. That is, in the above embodiment, when the fiber preforms 2, 3, 5, and 7 are manufactured, the rods 24 and 25 or the tube material 27 are arranged so as to be symmetric with respect to the central axis of the base material 26. However, it is not always necessary to arrange these 24, 25 and 27 so as to be symmetrical. However, it is preferable that the interface shapes of the first and second claddings 12 and 13 in the double-clad fibers 1, 4 and 6 are symmetric so that fusion splicing can be easily performed.
[0072]
  In the above embodiment, a relatively large number of the bars 24 and 25 or the pipes 27 are arranged on the base material 26, respectively. However, for example, a relatively small number of the bars 24, 25 such as one or two Double clad fibers 1, 4, and 6 may be manufactured by arranging the tube material 27 with respect to the base material 26. Even in such a case, the skew component of the excitation light may cause the reflection position at the interface between the first and second claddings 12 and 13 to be displaced so as to circulate around the core 11. Even if the interface shape of the claddings 12 and 13 is not necessarily formed by a large number of irregularities, the skew component can be suppressed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a double clad fiber manufactured by a manufacturing method according to a first embodiment.
FIG. 2 is an explanatory diagram showing a procedure for manufacturing the double clad fiber according to the first embodiment.
FIG. 3A is a cross-sectional view showing a base material of a double clad fiber according to a first modification. (B) is a cross-sectional view showing a double clad fiber manufactured using the base material.
FIG. 4 is a transverse sectional view showing a base material of a double clad fiber according to a second modification.
FIG. 5 is a cross-sectional view of a double clad fiber manufactured by the manufacturing method according to the second embodiment.
FIG. 6 is an explanatory diagram showing a manufacturing procedure of a double clad fiber according to a second embodiment.
FIG. 7 is a perspective view showing a production state of a base material using a burner.
[Explanation of symbols]
1,4,6 double clad fiber
11 core
12 First cladding
13 Second cladding
2, 3, 5, 7 Fiber preform
24,25 Bar material
26 Base material
27 Tube material (saddle-like material)

Claims (9)

A method for producing a double-clad fiber having a core extending in the fiber central axis direction, a first clad covering the periphery of the core, and a second clad covering the periphery of the first clad,
A fiber comprising: a columnar base material constituting the core and the first cladding in the double clad fiber; and at least one bowl-shaped material that is in contact with the outer peripheral surface of the base material and is disposed along the longitudinal direction of the base material Producing a base material;
A process of drawing into a fiber shape by heating and stretching the produced fiber preform,
Forming a second cladding in the double-clad fiber by coating a resin around the drawn fiber ,
The method for producing a double clad fiber, wherein the saddle-shaped material is a rod material . A method for producing a double-clad fiber having a core extending in the fiber central axis direction, a first clad covering the periphery of the core, and a second clad covering the periphery of the first clad,
By disposing at least one hook-like material along the longitudinal direction of the base material that is the core and the first base material of the columnar base material in the double clad fiber and integrating them, the fiber mother Producing a material;
A process of drawing into a fiber shape by heating and stretching the produced fiber preform,
Forming a second cladding in the double-clad fiber by coating a resin around the drawn fiber ,
The method for producing a double clad fiber, wherein the saddle-shaped material is a rod material . A method for producing a double-clad fiber having a core extending in the fiber central axis direction, a first clad covering the periphery of the core, and a second clad covering the periphery of the first clad,
A fiber comprising: a columnar base material constituting the core and the first cladding in the double clad fiber; and at least one bowl-shaped material that is in contact with the outer peripheral surface of the base material and is disposed along the longitudinal direction of the base material Producing a base material;
A process of drawing into a fiber shape while integrating the base material and the bowl-shaped material by heating and stretching the produced fiber preform,
Forming a second cladding in the double-clad fiber by coating a resin around the drawn fiber ,
The method for producing a double clad fiber, wherein the saddle-shaped material is a rod material . A method for producing a double-clad fiber having a core extending in the fiber central axis direction, a first clad covering the periphery of the core, and a second clad covering the periphery of the first clad,
By disposing at least one hook-like material along the longitudinal direction of the base material that is the core and the first base material of the columnar base material in the double clad fiber and integrating them, the fiber mother Producing a material;
A process of drawing into a fiber shape by heating and stretching the produced fiber preform,
Forming a second cladding in the double-clad fiber by coating a resin around the drawn fiber,
The bowl-shaped material is a hollow tube material,
The step of producing the fiber preform includes, after integrating the base material and the pipe material, removing the vicinity of the outer peripheral edge of the fiber preform, thereby removing the hollow portion of the pipe material from the radial direction of the fiber preform. A method for producing a double-clad fiber, characterized by comprising a step of opening in a direction. A method for producing a double-clad fiber having a core extending in the fiber central axis direction, a first cladding covering the periphery of the core, and a second cladding covering the periphery of the first cladding,
A fiber comprising: a columnar base material constituting the core and the first cladding in the double clad fiber; and at least one bowl-shaped material that is in contact with the outer peripheral surface of the base material and is disposed along the longitudinal direction of the base material Producing a base material;
A process of drawing into a fiber shape by heating and stretching the produced fiber preform,
Forming a second clad in the double clad fiber by coating a resin around the drawn fiber,
The bowl-shaped material is a hollow tube material,
When melting and integrating the base material and the tube material, the hollow portion of the tube material is crushed.
A method for producing a double-clad fiber. In any one of Claims 1-5 ,
A method for producing a double clad fiber, wherein a plurality of bowl-shaped members are arranged on the outer peripheral surface of a base material so as to be symmetrical with respect to the central axis of the base material. In any one of Claims 1-6 ,
A method for producing a double-clad fiber, wherein a plurality of bowl-shaped materials are densely arranged on an outer peripheral surface of a substrate. In any one of Claims 1-3,
A method for producing a double-clad fiber, wherein the bar has a circular cross section. In any one of Claims 1-3,
A method for producing a double-clad fiber, wherein the rod has a semicircular cross section.

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