JP2005070461A - Polarization maintaining photonic crystal fiber, its fiber end treatment method, computer program for controlling optical fiber fusion splicing system and recording medium capable of reading the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization maintaining PCF which permits easy visual recognition of the main axis direction of polarization by the side elevation view of a fiber, its fiber end treatment method, a computer program for controlling an optical fiber fusion splicing system and a recording medium capable of reading the program. <P>SOLUTION: The cross section of the fiber is provided with pores for markers in the main axis direction of the polarization or the direction perpendicular thereto. At least portions of a plurality of the pores disposed at a clad are sealed at the fiber end. As a result, the visual recognition of the pores for the markers by the side elevation view of the fiber is made possible. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polarization-maintaining photonic crystal fiber (hereinafter referred to as “polarization-maintaining PCF”), a fiber end processing method thereof, a computer program for controlling an optical fiber fusion splicing device, and a readable program thereof. The present invention relates to a recording medium.

  The polarization maintaining fiber keeps the polarization main axis direction of the transmitted light constant. Therefore, when connecting polarization-maintaining fibers, if the polarization main axis directions are not matched, there is a risk of causing crosstalk between polarizations. Further, a fiber terminal component such as a connector may be attached to the fiber end. The fiber terminal part is provided with a key groove indicating the polarization main axis direction of the transmitted light, and the fiber terminal part is attached to the apparatus with the key groove aligned with the key at the input end of the apparatus. However, when attaching the fiber terminal component to the optical fiber, the polarization main axis direction of the light transmitted through the optical fiber may be misaligned with the key groove of the fiber terminal component. It is not measured or monitored correctly. Therefore, it is desirable to know the direction of the polarization main axis of light transmitted before connection or attachment, whether the polarization maintaining fibers are connected to each other or the fiber terminal component is attached to the optical fiber. An optical fiber fusion splicing device is often used when connecting the fibers. In the optical fiber fusion splicing device, the side surface of the fiber is connected so that the side surface of the fiber is seen through to prevent core displacement. It is desirable that the polarization main axis direction can be visually recognized.

  A polarization-maintaining PCF, which is an example of a polarization-maintaining fiber, is a photonic in the fiber radial direction by a core and a plurality of pores formed so as to cover the core and extend along the core. And a clad having a crystal structure. And, for example, by making one of the three pairs of pores adjacent to the core and sandwiching the core into large pores, the light transmission region becomes elliptical, and the transmitted light The polarization plane is maintained. Therefore, the polarization main axis direction can be visually recognized by observing the distribution of pores in the cladding.

  However, since the polarization maintaining PCF has a plurality of pores in the longitudinal direction of the fiber, it is difficult to know the distribution state of the pores from the side view of the fiber. Therefore, when a pair of marker portions are provided in the polarization main axis direction or a direction perpendicular thereto so as to extend in the longitudinal direction of the fiber, and the marker portions are filled with a material having a refractive index different from that of the core and clad, the polarization main axis in a side view is obtained. The direction can be visually recognized. However, since the refractive index is different from that of the core and the clad, the marker portion must be provided at a position away from the core in the fiber radial direction so as not to affect the transmitted light. Therefore, it is difficult to design, and costs and time are spent in manufacturing. There is also a risk that the mechanical strength will deteriorate.

  The present invention has been made in view of such points, and an object of the present invention is to provide a polarization-maintaining PCF capable of easily visually recognizing the polarization main axis direction when viewed from the side of the fiber at the fiber end, and its fiber end treatment. It is an object to provide a computer program for controlling a method and an optical fiber fusion splicing device and a readable recording medium of the program.

  The invention of claim 1 includes: a core; and a clad having a photonic crystal structure formed in a fiber radial direction by a plurality of pores provided so as to cover the core and extending along the core. A polarization-maintaining photonic crystal fiber having at least a pair of marker pores extending along a fiber length direction arranged in a polarization main axis direction or a direction perpendicular thereto, at a fiber end In addition, at least a part of the plurality of pores is sealed, and the marker pores are visible in a side view of the fiber in an arbitrary direction.

  According to the above configuration, when the fiber side surface of the fiber end portion is viewed through with a microscope or the like, the marker pore can be visually recognized. Since a pair of marker pores are provided, when the fiber is rotated with the center of the fiber as the rotation axis, two marker pores are usually observed. Only books will be observed. Furthermore, since the marker pores are provided in the polarization main axis direction, the polarization main axis direction is known from the number of marker pores observed. Therefore, the polarization main axis direction can be easily visually recognized from the side surface of the fiber.

  According to a second aspect of the present invention, in the first aspect, of the pores adjacent to the core, only a pair of pores provided so as to sandwich the core is formed to have a larger pore diameter than the other pores. Polarization can be maintained, and the pair of pores constitute the pair of marker pores.

  According to the above configuration, the optical fiber has a polarization maintaining function by providing the marker pores.

  The invention of claim 3 is characterized in that, in claim 1, the ratio (d1 / d2) of the pore diameter (d1) of the marker pore to the pore diameter (d2) of the other pore is larger than 1.3. To do.

  In the above configuration, the marker pores can be easily viewed from the side of the fiber. According to a fourth aspect of the present invention, there is provided a core, and a clad having a photonic crystal structure formed in a fiber radial direction by a plurality of pores provided so as to cover the core and extending along the core. A polarization-maintaining photonic crystal fiber end treatment method in which at least a pair of marker pores extending along a fiber length direction arranged in a polarization main axis direction or a direction perpendicular thereto is formed. Then, at the fiber end portion, at least a part of the plurality of pores is sealed so that the marker pore can be visually recognized in a fiber side view in an arbitrary direction.

  According to the above method, when the fiber side surface of the fiber end portion is observed through with a microscope or the like, the marker pores can be visually recognized. Since a pair of marker pores are provided, when the fiber is rotated with the center of the fiber as the rotation axis, two marker pores are usually observed. Only books will be observed. Furthermore, since the marker pores are provided in the polarization main axis direction, the polarization main axis direction is known from the number of marker pores observed. Therefore, when this fiber end processing is applied to the polarization maintaining PCF, the polarization main axis direction can be easily visually recognized from the side view of the fiber.

  The invention of claim 5 is characterized in that, in claim 4, at least a part of the plurality of pores is sealed.

  This is one embodiment of the fiber end treatment method of the present invention.

  According to a sixth aspect of the present invention, in the fifth aspect, the inside of the pair of marker pores is pressurized during the heat treatment of the fiber end.

  According to the above method, only the marker pores can be reliably recognized.

  A seventh aspect of the invention is characterized in that in the fourth aspect, at least a part of the plurality of pores is filled with a sealing material having the same refractive index as that of the cladding, thereby sealing them.

  This is another embodiment of the fiber end treatment method of the present invention.

  The invention of claim 8 is a computer program for controlling an optical fiber fusion splicing device provided with first and second fiber holding portions and a fiber heating portion provided therebetween with a computer. In the computer, the end of the polarization-maintaining photonic crystal fiber in which the pore extending in the fiber length direction held in the first fiber holding portion is formed and the polarization held in the second fiber holding portion A procedure for positioning the first and second fiber holders so that the fiber ends of the holding optical fiber are spaced apart, and a fiber end of the polarization maintaining photonic crystal fiber held by the first fiber holder A procedure for positioning the first fiber holding unit and the fiber heating unit so that the fiber heating unit can heat the fiber heating unit; Heating the fiber end so that a part of the pore of the fiber end of the polarization maintaining photonic crystal fiber held by the first fiber holding part is sealed, and the first fiber holding The polarization main axis direction in the fiber cross section of the polarization maintaining photonic crystal fiber held in the section matches the polarization main axis direction in the fiber cross section of the polarization maintaining optical fiber held in the second fiber holding section. Thus, the procedure for positioning the first and / or second fiber holder, the polarization-maintaining photonic crystal fiber held by the first fiber holder, and the polarization-maintaining light held by the second fiber holder The first and second fiber holders and the fiber so that the fiber is butted and the butted part can be heated by the fiber heating unit. A procedure for positioning the heating unit, and a butt portion between the polarization maintaining photonic crystal fiber held in the first fiber heating unit and the polarization maintaining optical fiber held in the second fiber holding unit by the fiber heating unit And a procedure for heating.

  According to the above computer program, the polarization maintaining PCF having at least a pair of marker pores in the polarization main axis direction or a direction perpendicular thereto is used, and the marker pores are made larger in diameter than other pores. When pressure is applied to the marker pores, only the marker pores remain due to fiber end heating. When the fiber side surface is observed through a microscope or the like while rotating the fiber around the center of rotation of the fiber, two marker pores are usually observed, but when the two just overlap, only one is observed. It will not be done. Therefore, the polarization main axis direction of the polarization-maintaining PCF is known from the number of marker pores observed. The computer program can be executed when a program recorded on a computer-readable recording medium such as a flexible disk or a CD-ROM is installed in the computer or downloaded to the computer online.

According to the present invention, the polarization maintaining P that allows the polarization main axis direction to be easily visually recognized by side view of the fiber
A computer program for controlling a CF, a fiber end processing method thereof, an optical fiber fusion splicing device, and a recording medium capable of reading the program can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
As Embodiment 1 of the present invention, a structure of a polarization maintaining PCF 10, a manufacturing method, a fiber end processing method, and a computer program of the present invention will be described.

  First, the structure of the polarization maintaining PCF 10 will be described.

  FIG. 1 shows a fiber cross section of a polarization maintaining PCF 10 according to Embodiment 1 of the present invention. The polarization maintaining PCF 10 is made of quartz glass, and includes a solid core 11 that forms the center of the fiber, and a clad 12 that is provided so as to cover the core 11. The core 11 is provided with a high refractive index portion 11a having a circular shape in the fiber cross section over the entire length of the fiber. The clad 12 includes a pair of marker pores 13 a provided so as to sandwich the core 11 and in the short axis direction of the core 11, and a plurality of pores 13 b extending along the core 11 so as to surround the core 11. A photonic crystal structure is formed. The marker pores 13a are a pair of three pairs of pores facing each other across the core 11, and have a larger diameter than the other pores 13b, so that the light transmission region of the core 11 is elliptical. It has become. Therefore, by providing the marker pore 13a, the polarization maintaining PCF 10 displays the polarization main axis direction and becomes a polarization maintaining fiber.

  Next, a method for manufacturing the polarization maintaining PCF 10 will be briefly described.

  In the first manufacturing method, first, one quartz glass rod doped with germanium and a plurality of quartz capillaries are prepared. At this time, for two of the plurality of quartz capillaries, those having a hole diameter larger than the others are selected. In addition, the shape of the portion doped with germanium is circular in the cross section of the rod.

  Next, a base material is manufactured by bundling a quartz glass rod and a quartz capillary in a close-packed state. At this time, the quartz glass rod is disposed at the center position of the base material, and six quartz capillaries contacting the quartz glass rod are disposed near the center of the base material. And two of the six are large-diameter quartz capillaries, and the large-diameter quartz capillary sandwiches the quartz glass rod, and the short axis of the portion doped with germanium in the rod cross section of the quartz glass rod In the direction.

  Finally, the base material is drawn by heating and stretching. At this time, the polarization maintaining PCF 10 is formed such that the quartz rod and the quartz capillary and the quartz capillaries are fused and reduced in diameter, and the quartz core rod is formed to correspond to the core and the quartz capillary corresponds to the cladding. Manufactured.

  In the second manufacturing method, first, a solid quartz glass rod doped with germanium at the center of the rod is prepared. The portion doped with germanium is circular in the rod cross section.

  Next, using a drill, a plurality of holes are made in the rod cross section and penetrated in the longitudinal direction of the rod. At this time, first, six substantially circular holes are formed at equal intervals so as to surround the portion doped with germanium, and only the pair of holes in the minor axis direction of the portion has a larger hole diameter than the other holes. Like that. And 12 holes are opened at equal intervals on the outside. In this way, a plurality of holes are formed around the portion doped with germanium.

  Finally, the base material is drawn by heating and stretching. At this time, the polarization maintaining PCF 10 is manufactured in which the quartz core rod is formed in the core and the holes formed by using the drill correspond to the cladding, respectively.

  Next, a computer program for controlling the optical fiber fusion splicing device 20 will be described.

  2 shows a flowchart of the computer program of the present invention, FIG. 3 shows an optical fiber fusion splicing device 20, and FIG. 4 shows fiber side surfaces of the first and second polarization maintaining PCFs 10a and 10b in the computer program of the present invention. FIG. 4 is a perspective view of the fiber side surfaces of the first and second polarization maintaining PCFs 10a and 10b. In order to avoid complication of the drawing, the marker pores 13a provided inside the fiber and Other pores 13b are also indicated by solid lines.

  First, the first and second polarization maintaining PCFs 10a and 10b and the optical fiber fusion splicer 20 controlled by a computer in which the computer program of the present invention is installed are prepared. At this time, the first and second polarization maintaining PCFs 10a and 10b have the same structure as the polarization maintaining PCF 10 of the first embodiment. The fiber ends are exposed from glass. In addition, the computer program of the present invention is installed on the control computer of the optical fiber fusion splicing device 20 via a recording medium such as a flexible disk or a CD-ROM, or downloaded online.

  Here, the optical fiber fusion splicing device 20 will be described. As shown in FIG. 3, the optical fiber fusion splicing device 20 includes first and second fiber holding portions 21 and 22 and a fiber heating portion 23 provided therebetween. The first and second fiber holding portions 21 and 22 include first and second V-grooves 21a and 22a, first and second sheath V-grooves 21b and 22b, and first and second sheath clamps 21c and 22c, respectively. The fiber heating unit 23 includes a lens 23 a and a discharge electrode rod 23 b, which are controlled by a control computer of the optical fiber fusion splicer 20. The fiber heating unit 23 heats the end surfaces of the optical fibers held by the first and second fiber holding units 21 and 22 and simultaneously displays the fiber side surfaces of these fiber end surfaces on the display device. Therefore, the lens 23a is seen through the fiber side surface, and a CCD camera (not shown) connected to the lens 23a observes the fiber side surface seen through the lens 23a and is connected to the CCD camera (display device). (Not shown) displays the fiber side surface on the screen after image processing.

  Next, the first and second polarization maintaining PCFs 10 a and 10 b are attached to the optical fiber fusion splicing device 20. At this time, as shown in FIG. 3, the first polarization maintaining PCF 10a is provided in the first V-groove 21a and is sandwiched between the first sheath V-groove 21b and the first sheath clamp 21c. Further, the second polarization maintaining PCF 10b is provided in the second V groove 22a, and is sandwiched between the second sheath V groove 22b and the second sheath clamp 22c. Then, the start button of the optical fiber fusion splicing device 20 is pushed. Then, the computer program is started and executed in the order of step S1, step S2, and step S3.

  In step S1, the first and second sheath V grooves 21b and 22b and the first and second sheath clamps 21c and 22c are moved to the standby position. As a result, as shown in FIG. 4A, the fiber end face of the first polarization maintaining PCF 10a and the fiber end face of the second polarization maintaining PCF 10b are positioned with a space therebetween.

  In step S2, the first sheath V-groove 21b and the first sheath clamp 21c are moved to the discharge electrode rod 23b. Thus, the fiber end portion of the first polarization maintaining PCF 10a sandwiched between the first sheath V-groove 21b and the first sheath clamp 21c is positioned below the discharge electrode rod 23b.

  In step S3, heat is supplied to the discharge electrode rod 23b. Thereby, the fiber end portion of the first polarization maintaining PCF 10a is heated and melted. At this time, at the fiber end of the first polarization maintaining PCF 10a, the clad 12 is melted by heating, and the marker pores 13a and the other pores 13b are sealed (hereinafter referred to as “sealing portion”). This heat is conducted to some extent in the longitudinal direction of the fiber, and in that region, the clad 12 is slightly melted and seals the other pores 13b (hereinafter referred to as “marker pore remaining portion”). In a region sufficiently away from the end face of the fiber, this heat is not conducted at all, so the clad 12 is not melted (hereinafter referred to as “pore remaining portion”). Therefore, as shown in FIG. 4B, the first polarization maintaining PCF 10a includes a sealing portion 17, a marker pore remaining portion 18, and a pore remaining portion 19 in order from the fiber end in the fiber longitudinal direction. The marker pores 13a are formed longer than the other pores 13b in the longitudinal direction of the fiber.

  In step S4, the first sheath V-groove 21b and the first sheath clamp 21c are moved to the standby position. As described above, the fiber end portion of the first polarization maintaining PCF 10a is processed in steps S2 to S4.

  In Steps S5 to S7, the same commands as those issued to the first sheath V groove 21b, the first sheath clamp 21c and the discharge electrode rod 23b in Steps S2 to S4 are sent to the second sheath V groove 22b and the second sheath. The scram 22c and the discharge electrode rod 23b are lowered. Then, as shown in FIG. 4C, the sealing portion 17, the marker pore remaining portion 18, and the pore remaining portion 19 are also formed in the second polarization maintaining PCF 10b, and as a result, in the fiber longitudinal direction. In contrast, the marker pores 13a are formed longer than the other pores 13b. Further, as shown in FIG. 4 (c), in the marker pore remaining portion 18, only one marker pore 13a is observed in the first polarization maintaining PCF 10a, whereas the second polarization polarization In the holding PCF 10b, two marker pores 13a are observed. This suggests that the two marker pores 13a overlap in the first polarization maintaining PCF 10a.

  In step S8, the first and second V grooves 21a and 22a are moved. As a result, the x-axis direction and the y-axis direction of the first and second polarization maintaining PCFs 10a and 10b coincide with each other. Here, the x-axis direction and the y-axis direction are respectively the x-axis direction and the y-axis direction shown in FIG.

  In step S9, the first and second sheath V grooves 21b and 22b and the first and second sheath clamps 21c and 22c are rotated. At this time, as shown in FIG. 6 (d), first and second marker pores 13a are observed so as to overlap each other, that is, one marker pore 13a is observed. The sheath clamps 21c and 22c are positioned. Therefore, the polarization main axis directions of the first polarization maintaining PCF 10a and the second polarization maintaining PCF 10b coincide.

  In step S10, the first and second sheath V grooves 21b and 22b and the first and second sheath clamps 21c and 22c are moved to the discharge electrode rod 23b. As a result, the fiber end of the first polarization maintaining PCF 10a and the fiber end of the second polarization maintaining PCF 10b are positioned below the discharge electrode rod 23b.

  In step S11, heat is supplied to the discharge electrode rod 23b. Thereby, the fiber ends of the first and second polarization maintaining PCFs 10a and 10b are heated and melted and connected. Then, the computer program of the present invention ends.

  Finally, a fiber end processing method will be described.

  The first fiber end processing method is to heat the fiber end applied during execution of the computer program of the present invention.

  In the second fiber end processing method, pressure is applied to the marker pores 13a of the polarization maintaining PCF 10 and then heated. At this time, since a pressure difference is generated between the marker pore 13a and the other pore 13b, when heated in this state, only the other pore 13b is sealed as shown in FIG. Thereby, the marker pore remaining part 18 is formed, and the marker pore 13a is formed longer than the other pores 13b in the longitudinal direction of the fiber. Therefore, the same effect as that obtained when the first fiber end processing method is applied can be obtained.

  In the third fiber end processing method, first, two films that are substantially the same as or slightly larger than the size of the marker pore 13a in the fiber cross section are prepared. Next, the film is pasted so as to cover the marker pores 13 a on the fiber end face of the polarization maintaining PCF 10. Subsequently, the fiber end face of the polarization maintaining PCF 10 is filled with a filler having substantially the same refractive index as that of the cladding 12. By doing in this way, the same effect as the effect acquired by the 1st and 2nd fiber end treatment methods can be acquired.

  As described above, the polarization maintaining PCF 10 can visually recognize the polarization main axis direction from the side surface of the fiber by performing the first to third fiber end processing methods. The side surface of the polarization-maintaining PCF before the fiber end processing method is provided with a plurality of pores as shown in FIG. 4A, and a marker portion having a refractive index different from that of the core and the cladding is provided. Even in this case, since the plurality of pores 13b block the field of view, it is difficult to visually recognize the polarization main axis direction from the side surface of the fiber. However, when the first to third fiber end processing methods are applied, the marker pore remaining portion 18 is formed in the vicinity of the fiber end, and the marker fine portion is not interrupted by the plurality of other pores 13b from the side of the fiber. Only the hole 13a is visible. Further, since a pair of marker pores 13a are provided so as to sandwich the core 11 and in the direction of the polarization main axis, as shown in FIG. However, when the two just overlap, only one is observed, and the polarization main axis direction is known from the number of marker pores 13a observed. Therefore, it is easy to visually recognize the polarization main axis direction as viewed from the side of the fiber.

  In addition, according to the first fiber end processing method, if the marker pore 13a has a larger diameter than the other pores 13b, the marker end can be reduced with respect to the fiber longitudinal direction simply by heating the fiber end. The hole 13a is formed long. Therefore, the polarization main axis direction can be known without spending time and cost. In addition, according to the second and third fiber end processing methods, even if the marker pore 13a and the other pore 13b have the same size, the marker pore 13a is elongated in the fiber longitudinal direction. Can be formed.

  In addition, according to the computer program of the present invention, the first fiber end processing method is performed before the optical fibers are brought into contact with each other. Therefore, the polarization main axis direction can be visually recognized, and the risk of incurring cross-polarization crosstalk is very low when the polarization maintaining PCFs 10 are connected to each other.

<< Embodiment 2 of the Invention >>
As Embodiment 2 of the present invention, the polarization maintaining PCF 30 and side tunnel type optical fiber or panda type optical fiber using the structure and manufacturing method of the polarization maintaining PCF 30 and the optical fiber fusion splicer 20 described in Embodiment 1 above. (Hereinafter referred to as “another polarization maintaining fiber”) will be described.

  First, the structure of the polarization maintaining PCF 30 will be described.

  FIG. 6 shows a fiber cross section of the polarization maintaining PCF 30 according to the second embodiment of the present invention. The polarization maintaining PCF 30 is made of quartz glass, and includes a solid core 31 that forms the center of the fiber, and a clad 32 that is provided so as to cover the core 31. The core 31 is provided with a high refractive index portion 31a having a circular shape in the fiber cross section over the entire length of the fiber. The clad 32 includes a pair of marker pores 33 a provided in the short axis direction of the core 31 and far away from the core 31 in the radial direction of the fiber, and a plurality of marker pores 33 a extending along the core 31 so as to surround the core 31. A photonic crystal structure is formed with the other pores 33b. In the cross section of the fiber, a solid portion corresponding to two of the other pores 33 b is formed at the center of the fiber, which forms the core 31. Thereby, the polarization maintaining PCF 30 has a polarization maintaining function. As described above, the polarization maintaining PCF 30 differs from the polarization maintaining PCF 10 of the first embodiment in the position where the marker pores 33a are disposed and the arrangement method of the other pores 33b.

  Next, a method for manufacturing the polarization maintaining PCF 30 will be briefly described. Since the structure is slightly different from the polarization maintaining PCF 10 of the first embodiment, the difference will be described below.

  The first manufacturing method differs in the method of disposing the quartz capillary when creating the base material. That is, eight quartz capillaries are placed in contact with the quartz glass rod at equal intervals. On the outside, 14 quartz capillaries are arranged at equal intervals. In this way, the quartz capillary is arranged around the quartz glass rod so that two opposite sides are longer than the other four sides, and the difference between them is the same as the length of the four sides. Established. The large-diameter quartz capillaries are arranged in a pair at locations away from the quartz glass rod in the radial direction of the base material, and are provided in the short direction of germanium provided on the quartz glass rod.

  In the second manufacturing method, the arrangement of a plurality of holes opened using a drill is different. Eight substantially circular holes are formed at equal intervals around the portion doped with germanium. And 14 holes are opened at equal intervals on the outside. In this way, holes are formed so that a hexagonal shape is formed in which the two opposite sides are longer than the other four sides and the difference between them is the same as the length of the four sides. The large-diameter hole is opened in a portion away from the portion doped with germanium in the radial direction of the rod and in the minor axis direction of the portion doped with germanium.

  Finally, the case where the polarization maintaining PCF 30, another polarization maintaining fiber, and the optical fiber fusion splicing device 20 described in the first embodiment are prepared and the two optical fibers are connected will be described.

  The other polarization maintaining fiber includes a core and a clad provided so as to cover the core in the fiber cross section. The clad is provided with a portion having a lower refractive index than the clad so as to be adjacent to the core (hereinafter referred to as a “low refractive index portion”) or a stress applying portion, so that stress birefringence occurs in the core, As a result, the polarization plane of the transmitted light is maintained. The pair of low refractive index portions or stress applying portions is provided in the fiber longitudinal direction. For this reason, when the fiber side surface of another polarization maintaining fiber is seen through, two low refractive index portions or stress applying portions are observed in the clad, so that the polarization maintaining PCF has the first to third aspects. The same effect as when the fiber end processing method is applied can be obtained. That is, since the polarization main axis direction is known by a pair of low refractive index portions or stress applying portions, it is not necessary to apply the first to third fiber end processing methods of the first embodiment to other polarization maintaining fibers. . Therefore, when another polarization maintaining fiber and the polarization maintaining PCF 30 are connected using the optical fiber fusion splicing device 20, step S2-4 or step S5-7 in the flowchart of the computer program of the present invention shown in FIG. Are omitted, and for the other steps, the program is executed as described in the first embodiment. Then, the same effect as the effect described in the first embodiment can be obtained.

<< Embodiment 3 of the Invention >>
As Embodiment 3 of the present invention, a structure, a manufacturing method, a fiber end processing method, and a computer program of the present invention of the polarization maintaining PCF 40 will be described.

  First, the structure of the polarization maintaining PCF 40 will be described.

  FIG. 7 shows a fiber cross section of the polarization maintaining PCF 40 according to the third embodiment of the present invention. The polarization maintaining PCF 40 is made of quartz glass, and includes a solid core 41 that forms the center of the fiber, and a clad 42 that is provided so as to cover the core 41. The core 41 is provided with a high refractive index portion 41a having a circular shape in the fiber cross section over the entire length of the fiber. The clad 42 includes a pair of marker pores 43 a provided in the long axis direction of the core 41 and far from the core 41 in the radial direction of the fiber, and a plurality of marker pores 43 a extending along the core 41 so as to surround the core 41. A photonic crystal structure is formed with the other pores 43b. And in the fiber cross section, the solid part for two other pores 43b is formed in the fiber center, and it forms the core 41. Thereby, the polarization maintaining PCF 40 has a polarization maintaining function. As described above, the polarization maintaining PCF 40 differs from the polarization maintaining PCF 30 of the second embodiment only in the positions where the marker pores 43a are disposed.

  Next, a method for manufacturing the polarization maintaining PCF 40 will be briefly described. Since the structure is slightly different from the polarization maintaining PCF 30 of the second embodiment, the difference will be described below.

  In the first manufacturing method, a large-diameter quartz capillary is provided in the major axis direction of germanium when a base material is formed.

  In the second manufacturing method, when the drill is used, the large-diameter hole is opened in the major axis direction of the portion doped with germanium.

  Finally, a case where a fiber terminal component such as a connector is attached to the polarization maintaining PCF 30 will be described.

  The fiber terminal part is provided with a keyway indicating the polarization main axis direction of the optical fiber. Before the polarization maintaining PCF 40 and the connector are brought into contact with each other, the polarization maintaining PCF 40 is connected to the first to third of the first embodiment. Apply one of the fiber end treatment methods. Then, as described in the first embodiment, the marker pore remaining portion 18 is formed in the polarization-maintaining PCF 40, and the polarization main axis direction can be visually recognized in a fiber side view. Therefore, the effect that the key groove and the polarization main axis direction can be aligned is obtained, and as a result, when the connector is attached to the input end of the apparatus, the measurement or monitoring can be performed correctly. It is done.

<< Embodiment 4 of the Invention >>
As a fourth embodiment of the present invention, the structure and manufacturing method of the polarization maintaining PCF 50 will be described.

  First, the structure of the polarization maintaining PCF 50 will be described.

  FIG. 8 shows a fiber cross section of a polarization maintaining PCF 50 according to Embodiment 4 of the present invention. The polarization maintaining PCF 50 is made of quartz glass, and includes a solid core 51 that forms the center of the fiber, and a clad 52 that is provided so as to cover the core 51. The core 51 is provided with a high refractive index portion 51a having a circular shape in the fiber cross section over the entire length of the fiber. The clad 52 includes two pairs of marker pores 53 a provided so as to sandwich the core 51 and in the short axis direction of the core 51, and a plurality of other pores 53 b extending along the core 51. A crystal structure is formed. And in the fiber cross section, the solid part for two other pores 53b is formed in the fiber center, and it forms the core. Thereby, the polarization maintaining PCF 50 has a polarization maintaining function. As described above, the size of the marker pore 53a and the number of marker pores are different from those of the second and third embodiments. That is, the marker pores 53a and the other pores 53b have the same size.

  Next, a method for manufacturing the polarization maintaining PCF 50 will be briefly described. Since the structure is slightly different from the polarization-maintaining PCFs 30 and 40 of the second and third embodiments, the differences will be described below.

  In the first manufacturing method, the diameters of the quartz capillary holes to be prepared are the same.

  In the second manufacturing method, the sizes of the holes opened using the drill are the same.

  When the polarization maintaining PCF 50 is subjected to the second and third fiber end processing methods of the first embodiment, the same effect as the first embodiment can be obtained. That is, if the polarization maintaining PCF or another polarization maintaining fiber is connected after the treatment, the risk of crosstalk between polarizations is reduced. In addition, when attaching the fiber terminal component, the key groove of the fiber terminal component and the polarization main axis direction can be matched so that measurement or monitoring can be performed correctly using the apparatus. In addition, when the fiber side surface after the fiber end treatment is seen through, only one marker pore is observed when the marker pore remaining portion is completely overlapped, but from this case, the polarization main axis direction is 90 °. When the polarization maintaining PCF 50 is rotated so as to be displaced, four pairs are observed because two pairs are provided.

<< Other Embodiments >>
The polarization maintaining PCFs 10, 30, 40, and 50 of the first to fourth embodiments are only examples in the present invention. For example, the marker pore is a pore provided in the polarization main axis direction in the polarization maintaining PCF 50 of the fourth embodiment, but the pore provided in a direction perpendicular to the polarization main axis direction. As described above, the second and third fiber end processing methods of the first embodiment may be applied.

  In the computer program for controlling the optical fiber fusion splicing apparatus 20 according to the first to fourth embodiments, steps S2 to 4 are executed after steps S2 to 4 are completed. However, they may be executed simultaneously after step S1 is completed. In this program, the first and second optical fiber holding units 21 and 22 are moved and the fiber heating unit 23 is fixed. However, the fiber heating unit 23 is moved and the first and second optical fiber holding units 21 and 22 are fixed. 22 may be fixed.

  In the first embodiment, after the first to third fiber end processing, the connection between the polarization maintaining PCFs 10 is performed. In the second embodiment, the connection between the polarization maintaining PCF 30 and another polarization maintaining fiber is performed. In the third embodiment, the attachment of the polarization maintaining PCF 40 and the connector has been described, but this combination is not limited at all.

  Specific examples will be described.

<< Embodiment 1 of the Invention >>
One polarization maintaining PCF showing the same structure as that of the first embodiment and the same optical fiber fusion splicing device as those of the first embodiment were prepared. Table 1 shows the fiber diameter (μm), d1 (μm), d2 (μm), Λ (μm), and d1 / d2 of the polarization maintaining PCF used in the first embodiment. As shown in FIG. 9, d1, d2 and Λ are the pore diameter of the marker pore, the pore diameter of other pores, and the distance between the centers of adjacent pores, respectively.

  The fiber end of the polarization maintaining PCF having the structural parameters shown in Table 1 is heated for a certain time using an optical fiber fusion splicer, and the length of the marker pore in the longitudinal direction of the fiber at the remaining portion of the marker pore The discharge intensity dependency of L (hereinafter referred to as “the length of the marker pore”) was examined. Here, the discharge intensity means a physical quantity that depends on the current value flowing through the discharge electrode rod of the optical fiber fusion splicing device, and means that the larger the discharge intensity value, the larger the amount of current flowing. The temperature rises. However, there is no quantitative relationship between the discharge intensity value and the heating temperature. The discharge time shown in Table 2 is the time for discharging the discharge electrode rod, and can be regarded as the time for heating the fiber end.

  Table 2 shows the measurement results of L when the discharge time is 2000 (milliseconds) and the discharge intensity is varied in the range of 10-25.

  From Table 2, it can be seen that L decreases as the discharge intensity value increases. That is, if the discharge time is constant, it can be seen that the heating temperature and L are inversely proportional.

<< Embodiment 2 of the Invention >>
A polarization-maintaining PCF having a d1 / d2 value smaller than the polarization-maintaining PCF used in Example 1 and the same optical fiber fusion splicing device as Example 1 were prepared. Table 3 shows the fiber diameter (μm), d1 (μm), d2 (μm), Λ (μm), and d1 / d2 of the polarization maintaining PCF used in the second embodiment. The definitions of d1, d2, Λ, and d1 / d2 are the same as in the first embodiment.

  Using an optical fiber fusion splicer, the end of a polarization-maintaining PCF having the structural parameters shown in Table 3 is heated for 2000 (milliseconds) at a discharge intensity of 20, and the length L of the marker pore is measured. did. Table 4 shows the measurement results.

  From Table 4 and Table 2, it can be seen that when the discharge time and the discharge intensity are the same, the value of L depends on the value of d1 / d2, and as the value of d1 / d2 decreases, L decreases.

<< Embodiment 3 of the Invention >>
A polarization-maintaining PCF having a larger d1 / d2 value than the polarization-maintaining PCF used in Example 1 and the same optical fiber fusion splicing device as Example 1 were prepared. Table 5 shows the fiber diameter (μm), d1 (μm), d2 (μm), Λ (μm), and d1 / d2 of the polarization maintaining PCF used in the third embodiment. The definitions of d1, d2, Λ, and d1 / d2 are the same as in the first embodiment.

  Using an optical fiber fusion splicer, the fiber end portion of the polarization maintaining PCF having the structural parameters shown in Table 5 was heated for 2000 (milliseconds) at a discharge intensity of 20 as in Example 2 to provide a marker pore. The length L of was measured. Table 6 shows the measurement results.

  From Table 6 and Table 2, it can be seen that when the discharge time and discharge intensity are the same, the value of L depends on the value of d1 / d2, and as the value of d1 / d2 increases, L increases.

  The polarization-maintaining PCF used in Examples 1 to 3 may be the same polarization-maintaining PCF as in the first embodiment or the same polarization-maintaining PCF as in the second and third embodiments. . In the cross section of the fiber, marker pores are provided in the direction of the polarization main axis or in a direction perpendicular to that direction, and the marker pores only have to have a larger diameter than other pores.

<Action>
Table 7 shows the measurement results when heating was performed for 2000 (milliseconds) at a discharge intensity of 20 among the results of Examples 1 to 3 above.

  From the measurement results of Table 7 and Example 1, the length L of the marker pore is so long as to be visually recognized as 15 (μm) or more. Therefore, this polarization maintaining PCF is viewed from the side of the fiber when the fiber end is heated. Thus, the polarization main axis direction can be easily recognized. Further, it can be seen that the length L becomes longer as the discharge intensity is smaller and the value of d1 / d2 is larger. Further, from Table 7, it can be seen that if d1 / d2 of the polarization maintaining PCF is larger than 1.33, it can be visually recognized from the side view of the fiber.

It is a fiber cross-sectional view of polarization maintaining PCF10 in the first embodiment. It is a flowchart figure of the computer program which controls the optical fiber fusion splicing apparatus. It is a block diagram of the optical fiber fusion splicing device. It is a side view of 1st and 2nd polarization-maintaining PCF10a, 10b in a connection process. It is a side view of polarization maintaining PCF10 when the second and third fiber end processing methods in Embodiment 1 are performed. It is a fiber cross-sectional view of the polarization-maintaining PCF 30 in the second embodiment. It is a fiber cross-sectional view of polarization maintaining PCF40 in the third embodiment. It is a fiber cross-sectional view of the polarization maintaining PCF 50 in the fourth embodiment. It is explanatory drawing of the parameter of the structure of the polarization-maintaining PCF in the present Examples 1-3.

Explanation of symbols

10, 30, 40, 50 Polarization-maintaining PCF
10a First polarization maintaining PCF
10b Second polarization maintaining PCF
11, 31, 41, 51 Core 11a, 31a, 41a, 51a High refractive index portion 12, 32, 42, 52 Clad 13a, 33a, 43a, 53a Marker pores 13b, 33b, 43b, 53b Other pores 17 Pore sealing portion 18 Marker pore remaining portion 19 Pore remaining portion 20 Optical fiber fusion splicing device 21 First fiber holding portion 21a First V groove 21b First sheath V groove 21c First sheath clamp 22 Second fiber holding Part 22a second V groove 22b second sheath V groove 22c second sheath clamp 23 fiber heating part 23a lens 23b discharge electrode rod

Claims (9)

A core, and a clad having a photonic crystal structure formed in a fiber radial direction by a plurality of pores formed so as to cover the core and extending along the core. A polarization-maintaining photonic crystal fiber having at least a pair of marker pores extending along a fiber length direction arranged in a direction perpendicular thereto,
A polarization maintaining photonic characterized in that at least a part of the plurality of pores is sealed at the end of the fiber so that the marker pores are visible in a side view of the fiber in an arbitrary direction. Crystal fiber. In the polarization maintaining photonic crystal fiber according to claim 1,
Of the pores adjacent to the core, only a pair of pores provided so as to sandwich the core is capable of maintaining polarization by being formed with a larger pore diameter than the other pores,
The polarization maintaining photonic crystal fiber, wherein the pair of pores constitute the pair of marker pores. In the polarization maintaining photonic crystal fiber according to claim 1,
A polarization maintaining photonic crystal fiber, wherein a ratio (d1 / d2) of a pore diameter (d1) of the marker pore to a pore diameter (d2) of the other pore is larger than 1.3. A core, and a clad having a photonic crystal structure formed in a fiber radial direction by a plurality of pores formed so as to cover the core and extending along the core. A fiber end processing method for a polarization maintaining photonic crystal fiber in which at least a pair of marker pores extending along a fiber length direction arranged in a direction perpendicular thereto is formed. Fiber end treatment of a polarization maintaining photonic crystal fiber, wherein at least some of the plurality of pores are sealed so that the marker pores are visible in a side view of the fiber in the direction of Method. A fiber end processing method for a polarization maintaining photonic crystal fiber according to claim 4,
A fiber end processing method of a polarization maintaining photonic crystal fiber, wherein at least a part of the plurality of pores is sealed by heat treatment of the fiber end. A fiber end processing method for a polarization maintaining photonic crystal fiber according to claim 5,
A method of processing a fiber end portion of a polarization maintaining photonic crystal fiber, wherein the inside of the pair of marker pores is pressurized during the heat treatment of the fiber end portion. A fiber end processing method for a polarization maintaining photonic crystal fiber according to claim 4,
Filling at least part of the plurality of pores with a sealing material having the same refractive index as that of the clad to seal the ends of the polarization-maintaining photonic crystal fiber . A computer program for controlling with a computer an optical fiber fusion splicer comprising a first and second fiber holding unit, and a fiber heating unit provided therebetween,
On the computer,
A fiber end portion of a polarization maintaining photonic crystal fiber formed with a pore extending in the fiber length direction held by the first fiber holding portion and a polarization maintaining optical fiber held by the second fiber holding portion. Positioning the first and second fiber holders such that the fiber ends are spaced apart;
A procedure for positioning the first fiber holding unit and the fiber heating unit such that the fiber end of the polarization maintaining photonic crystal fiber held by the first fiber holding unit can be heated by the fiber heating unit;
A step of heating the fiber end so that a part of the pore of the fiber end of the polarization maintaining photonic crystal fiber held by the first fiber holding unit is sealed by the fiber heating unit;
The polarization main axis direction in the fiber cross section of the polarization maintaining photonic crystal fiber held by the first fiber holding section and the polarization main axis in the fiber cross section of the polarization holding optical fiber held by the second fiber holding section Positioning the first and / or second fiber holders so that the directions coincide;
The polarization-maintaining photonic crystal fiber held by the first fiber holding unit and the polarization-maintaining optical fiber held by the second fiber holding unit are abutted and the abutted part can be heated by the fiber heating unit. A procedure for positioning the first and second fiber holding units and the fiber heating unit so that
Heating the butted portion of the polarization maintaining photonic crystal fiber held in the first fiber heating unit and the polarization maintaining optical fiber held in the second fiber holding unit by the fiber heating unit;
A computer program characterized by executing the program. A computer-readable recording medium on which the computer program according to claim 8 is recorded.

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