JP2007272070A - Leakage optical fiber and method for manufacturing leakage optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage optical fiber that can reduce energy loss by efficiently leaking light, and also to provide a method for manufacturing the fiber. <P>SOLUTION: The leakage optical fiber 1 comprises a core 2, a clad 3, a light leaking section 4, and a clad protective layer 5. The core 2 is disposed in the center portion of the leakage optical fiber 1, and the clad 3 is circumscribed on the core 2. The light leaking section 4 is disposed in contact with the core 2 and in a part along the circumference direction of the core 2. Plurality of light leaking sections 4 are intermittently disposed along the longitudinal direction. The clad protective layer 5 is circumscribed on the clad 3. The clad protective layer 5 comprises a vinyl material or the like, and the clad protective layer 5 is not formed in a direction where the light leaking section 4 exists, in the circumference direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical fiber and a method for manufacturing the optical fiber, and more particularly to a leaky optical fiber that can extract light by leaking light and a method for manufacturing the leaky optical fiber.

  As a conventional leaky optical fiber, a second core for leaking light between the core and the clad provided on the outer periphery of the core is provided along the entire outer periphery of the core in a cross section orthogonal to the longitudinal direction of the optical fiber. Is known. The second core is provided over the entire length of the leaking optical fiber. In general, the refractive index of the cladding is lower in the optical fiber than in the core. The refractive index of the second core is higher than the refractive index of the cladding, and is provided so as to increase in a parabolic shape toward the outer side in the radial direction. Since the second core, which is a light leakage portion, is provided in the entire circumferential direction and the entire longitudinal direction of the leakage optical fiber, the light leaking from the leakage optical fiber extends over all directions of the entire section where the leakage optical fiber is provided. (For example, refer to Patent Document 1).

A leaky optical fiber in which a light leak portion is provided only in a part in the circumferential direction is also known (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 2001-133552 Japanese Patent Publication No.8-7284

  However, the conventional leaky optical fiber has a large amount of leaking light, and when used for communication, enormous energy loss occurs. In order to compensate for the energy loss, it is necessary to continue sending an excessively strong optical signal to the leaky optical fiber.

  Then, an object of this invention is to provide the leaking optical fiber which can reduce an energy loss by leaking light efficiently, and its manufacturing method.

  To achieve the above object, a core, a cladding having a lower refractive index than that of the core and circumscribed to the core, and formed in contact with the core, the refractive index being lower than the refractive index of the core and the cladding There is provided a leaky optical fiber including a plurality of light leaking portions which are higher than the refractive index and intermittently provided in the longitudinal direction of the core.

  Here, it is preferable that the light leakage portion is formed only in a part in the circumferential direction. Of the two adjacent light leaking portions, the light leaking portion on the downstream side in the light propagation direction preferably has a higher refractive index than the light leaking portion on the upstream side. Of the two adjacent light leaking portions, the size of the light leaking portion on the downstream side in the light propagation direction is preferably larger than that on the upstream side. Moreover, it is preferable that a mark is provided at a predetermined position in the circumferential direction of the outer peripheral surface of the clad.

  The present invention also provides a step of preparing a core rod as a core material of the core and a plurality of clad rods as a base material of a clad having a central axis formed with holes having substantially the same diameter as the core rod, and the clad rod A step of forming a cladding rod doped with an impurity for changing the base material into a light leakage portion in a part of the longitudinal direction of the innermost surface layer of the inner diameter of the hole, and a cladding rod doped with a plurality of the impurities. Leakage comprising a process of creating an assembly rod by inserting into a hole in the rod, a process of melting the assembly rod and creating an integrated rod, and a process of stretching the integrated rod in a molten state An optical fiber manufacturing method is provided.

  Here, in the step of preparing the cladding rod doped with the impurity, it is preferable that the cladding rod is doped with the impurity only in a part of the innermost surface layer of the inner diameter of the hole.

  In the step of stretching the integrated rod, it is preferable to form a mark at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding rod by passing the integrated rod through a mold.

  The present invention also provides a step of preparing a core rod as a core material of a core and a cladding rod as a base material of a clad having a central axis formed with a hole having the same diameter as the core rod, A step of creating an assembly rod by inserting the core rod as a base material of the core into the hole, a step of creating an integrated rod by melting the assembly rod, and a step of stretching the integrated rod A method for producing a leaky optical fiber comprising the steps of: intermittently doping impurities in the longitudinal direction of the integrated rod in the step of stretching the rod.

  Further, in the step of stretching the integrated rod, it is preferable to dope impurities only in a part of the circumferential direction of the integrated rod.

  In the step of stretching the integrated rod, it is preferable to form a mark at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding rod by passing the integrated rod through a mold.

  According to the leaky optical fiber of claim 1, the light is formed in contact with the core, the refractive index is lower than the refractive index of the core and higher than the refractive index of the clad, and a plurality of light intermittently provided in the longitudinal direction of the core. Since the leakage portion is provided, the location of leakage from the leakage optical fiber can be limited with respect to the longitudinal direction of the leakage optical fiber. For this reason, useless leakage of light can be reduced. Therefore, it is possible to propagate an optical signal over a long distance. Moreover, since the scattering by the leaked light can be reduced, the communication quality can be improved.

  According to the leaking optical fiber of the second aspect, since the leaking portion is formed only in a part in the circumferential direction, the light leaking from the leaking optical fiber can be limited in the circumferential direction. Thereby, useless leakage of light can be further reduced, and an optical signal can be propagated over a longer distance. In addition, communication quality can be further improved.

  According to the leaking optical fiber according to claim 3, since the refractive index of the light leakage part on the downstream side in the light propagation direction is higher than that of the light leakage part on the upstream side, the amount of light leaking can be made constant, Stable optical communication can be achieved.

  According to the leaking optical fiber of the fourth aspect, since the size of the light leaking portion on the downstream side in the light propagation direction is larger than that on the upstream side, the amount of leaking light can be made constant. Stable optical communication can be achieved.

  According to the leaking optical fiber of the fifth aspect, since the mark is provided at a predetermined position in the circumferential direction of the outer peripheral surface of the clad, the position where the light leaking portion of the leaking optical fiber is provided in the circumferential direction is specified. be able to. Therefore, the light leakage portion can be arranged in a desired direction when the leakage optical fiber is laid.

  According to the leaking optical fiber manufacturing method of claim 6, since a cladding rod doped with an impurity that changes the base material into a light leaking portion is formed in a part of the inner diameter outermost layer of the hole, A leaking optical fiber in which the leaking part is limited to the longitudinal direction can be provided.

  According to the method for manufacturing a leaky optical fiber according to claim 7, since each of the cladding rods is doped with impurities only in a part in the circumferential direction of the innermost surface layer of the hole, the light leaking portion is easily limited to the circumferential direction. Can be provided.

  According to the leak optical fiber manufacturing method of claim 8, in the step of stretching the integrated rod, a mark is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding rod by passing the integrated rod through a mold. Therefore, the mark can be provided on the entire longitudinal direction of the leaky optical fiber with a simple configuration.

  According to the method for manufacturing a leaky optical fiber according to claim 9, in the step of stretching the integrated rod, since the impurities are intermittently doped in the longitudinal direction of the integrated rod, the light leaking portion can be easily set in the longitudinal direction. It can be provided intermittently.

  According to the leaking optical fiber manufacturing method of the tenth aspect, since impurities are doped only in a part of the integrated rod in the circumferential direction, the light leaking portion can be easily limited to the circumferential direction.

  According to the leaking optical fiber manufacturing method of claim 11, in the step of stretching the integrated rod, a mark is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding rod by passing the integrated rod through a mold. Therefore, the mark can be provided on the entire longitudinal direction of the leaky optical fiber with a simple configuration.

  A leaky optical fiber and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a perspective view showing the structure of the leaky optical fiber 1. FIG. 2 is a cross-sectional view of a surface obtained by cutting the leaky optical fiber 1 in a direction perpendicular to the longitudinal direction.

  As shown in FIGS. 1 and 2, the leaky optical fiber 1 includes a core 2, a clad 3, a light leaking portion 4, and a clad protective layer 5. In FIG. 1, the clad protective layer 5 is omitted. The core 2 is provided at the center of the leaky optical fiber 1. The clad 3 circumscribes the core 2. In contact with the core 2, a light leakage portion 4 is provided in a part of the core 2 in the circumferential direction. As shown in FIG. 1, a plurality of light leakage portions 4 are provided intermittently along the longitudinal direction. The clad protective layer 5 (FIG. 2) circumscribes the clad 3. The clad protective layer 5 is made of a vinyl material or the like. In the circumferential direction, the cladding protective layer 5 is not formed in the direction in which the light leakage portion 4 exists.

  FIG. 3 is a graph showing the refractive index distribution of the leaky optical fiber 1 along the one-dot chain line shown in FIG. The X axis corresponds to the one-dot chain line in FIG. 2, and the Y axis represents the refractive index of the leaky optical fiber 1. Points A ′ and B ′ are points corresponding to points A and B on the outer circumferential surface of the clad in FIG. The refractive index profile is asymmetric with respect to the axis Y. As shown in the refractive index shape 2 a of the core 2, the refractive index of the core 2 decreases in a parabolic shape from the center O toward the outer side in the radial direction. Further, as indicated by the refractive index shape 3a of the cladding 3, the refractive index of the cladding 3 takes a constant value. This value is lower than the refractive index of the core 2. The refractive index 4a of the light leakage part 4 is lower than the refractive index of the core 2, higher than the refractive index of the cladding 3, and higher in the positive direction of the X axis.

  A method for manufacturing the leaky optical fiber 1 will be described with reference to the flowchart of FIG. In S10, a core rod 12 serving as a base material of the core 2 shown in FIG. 5 and a plurality of clad rods 13 serving as a base material of the clad 3 shown in FIG. 6 are prepared. The core rod 12 has a substantially cylindrical shape. The clad rod 13 has a substantially cylindrical shape, and a hole 13 a having the same diameter as that of the core rod 12 is formed at the center.

  In S20, as shown in FIG. 7, the light leakage base material 14 is doped as an impurity in a part in the longitudinal direction and the circumferential direction of the innermost surface layer of the hole of the cladding rod 13 as an impurity. Examples of the doping method at this time include a CVD (Chemical Vapor Diposition) method and an impurity diffusion method. The light leakage base material 14 forms the light leakage portion 4 (FIGS. 1 and 2).

  Next, in S30, as shown in FIG. 8, the fiber preform 10 is manufactured by inserting the core rod 12 into the holes 13a of the plurality of cladding rods 13 doped with the light leakage preform 14 respectively. The fiber preform 10 at this stage is called an assembly rod.

  The fiber stretcher 8 used in S40 and S50 will be described with reference to FIG. The fiber stretching device 8 includes an inert gas atmosphere furnace 50, a diameter measuring device 61, a clad protective layer coating device 71, a pulling pulley 81, a winding bobbin 82, a plurality of pulleys 83, and a control unit 91. A fiber preform container 51 and a heater 52 are provided in an inert gas atmosphere furnace 50. The control unit 91 is electrically connected to the diameter measuring device 61 and the pulling pulley 81. The diameter measuring device 61 is a device that measures the diameter of the fiber preform 10. The clad protective layer coating apparatus 71 is an apparatus for coating the clad protective layer 5 on the outer periphery of the fiber preform that has passed through the diameter measuring instrument. The take-up bobbin 82 is for taking up the leaky optical fiber 1 manufactured by stretching the fiber preform 10.

  In S <b> 40, the fiber preform 10 is placed in the fiber preform container 51, and the fiber preform 10 is melted by the heater 52. In the melted fiber preform 10, the core rod 12, the clad rod 13, and the light leakage preform 14 are integrated. This is called a rod in which the fiber preform at this stage is integrated. The molten fiber base material 10 is wound on a winding bobbin 82 via a diameter measuring device 61, a clad protective layer coating device 71, and a pulling pulley 81.

  In S50, a process of stretching the fiber preform 10 is performed. The fiber preform 10 winds the pull pulley 81 half a turn. Then, the fiber preform 10 is stretched by pulling the fiber preform 10 with the pull pulley 81. The diameter measuring device 61 sends the measured length of the diameter of the fiber preform 10 to the control unit 91. The controller 91 determines the position of the pull pulley 81 according to the length of the diameter of the fiber preform 10 and adjusts the position of the pull pulley 81. By adjusting the position of the pull pulley 81, the tension applied to the fiber preform 10 is adjusted. Thereby, the length of the diameter of the leaky optical fiber 1 to be manufactured can be set within a desired value range. Finally, the fiber preform 10 is wound around the winding bobbin 82, and the leaky optical fiber 1 is manufactured.

  The leaky optical fiber 1 (FIGS. 1 and 2) according to the above-described embodiment is provided with the light leaking part 4 intermittently in the longitudinal direction in part in the circumferential direction. According to such a configuration, first, the light propagating along the longitudinal direction of the leaky optical fiber 1 travels inside the core 2 while being reflected at the boundary portion between the core 2 and the clad 3. Of the light traveling in the longitudinal direction, part of the light incident on the light leaking part 4 leaks out of the leaking optical fiber 1 from the light leaking part 4. Therefore, the location where light leaks from the leaky optical fiber 1 can be made intermittent in the longitudinal direction within a specific range in the circumferential direction of the leaky optical fiber 1. Therefore, useless leakage of light can be reduced, and an optical signal can be propagated over a long distance. In addition, since scattering due to extra leaked light can be reduced, communication quality can be improved.

  Further, in the manufacturing method of the leaky optical fiber 1 described above, the light leaking base material 14 is doped as an impurity in a part of the outermost inner diameter layer of the hole of the cladding rod 13 in the longitudinal direction and the circumferential direction. For this reason, the light leakage part 4 can be easily formed intermittently in the longitudinal direction and limited to a specific range in the circumferential direction.

  A leaky optical fiber and a manufacturing method thereof according to the second embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a perspective view showing the structure of the leaky optical fiber 101. FIG. 11 is a cross-sectional view of a surface obtained by cutting the leaky optical fiber 101 in a direction orthogonal to the longitudinal direction.

  As shown in FIGS. 10 and 11, the leaky optical fiber 101 includes a core 102, a clad 103, a light leaking portion 104, and a clad protective layer 105. The core 102 is provided at the center of the leaky optical fiber 1. In FIG. 10, the clad protective layer 105 is omitted. The clad 103 circumscribes the core 102. The core 102 has a substantially circular cross section, but has a shape in which a part of the outer periphery is intermittently cut out by the light leakage portion 104 in the longitudinal direction. The light leakage portion 104 is in contact with a part of the core 102 that is notched in the circumferential direction, and is provided up to the position of the outermost peripheral surface of the clad 103 in the radial direction. That is, the light leaking part 104 according to the present embodiment is formed so as to pass a part of the core 102 from the outer peripheral surface of the leaking optical fiber 101. Moreover, the light leakage part 104 is provided in a part of the circumferential direction. Furthermore, as shown in FIG. 10, a plurality of light leakage portions 104 are provided intermittently along the longitudinal direction.

  12 is a graph showing the refractive index distribution of the leaky optical fiber 101 along the alternate long and short dash line shown in FIG. The X axis corresponds to the alternate long and short dash line in FIG. 11, and the Y axis represents the refractive index. Points C ′ and D ′ correspond to points C on the outer peripheral surface of the light leakage portion 104 and points D on the outer peripheral surface of the clad 103 shown in FIG. The refractive index profile is asymmetric with respect to the axis Y. The refractive index shape 102a of the core decreases in a parabolic shape from the center O toward the outer side in the radial direction. The refractive index shape 103a of the clad 103 exists only in the negative direction of the X axis. As shown in the refractive index shape 103 a, the refractive index of the cladding 103 is lower than the refractive index of the core 102 and takes a constant value. As shown in the refractive index shape 104a of the light leaking portion, the refractive index of the light leaking portion 104 increases to the point C ′ toward the positive direction of the X axis.

  A method for manufacturing the leaky optical fiber 101 will be described with reference to the flowchart of FIG. In S110, a core rod 112 serving as a base material of the core 102 shown in FIG. 14 and a clad rod 113 serving as a base material of the clad 103 shown in FIG. 15 are prepared. The core rod 112 has a substantially cylindrical shape. The clad rod 113 has a substantially cylindrical shape, and a hole 113a having the same diameter as that of the core rod 112 is formed in the central axis. The longitudinal lengths of the core rod 112 and the clad rod 113 are substantially equal. That is, in the present embodiment, unlike the first embodiment, one relatively long clad rod 113 is used. In S120, as shown in FIG. 16, the fiber preform 110 is manufactured by inserting the core rod 112 into the hole 113a of the cladding rod 113. The fiber preform 110 at this stage is called an assembly rod.

  The fiber stretcher 108 used in S130 to S140 will be described with reference to FIG. In the fiber stretching device 108 of FIG. 17, the same devices as those of the fiber stretching device 8 (FIG. 9) described in the first embodiment are denoted by the same reference numerals and description thereof is omitted. The fiber stretcher 108 includes an inert gas atmosphere furnace 150. The inert gas atmosphere furnace 150 is provided with a fiber preform container 151, a first heater 152, a light leakage member applying device 153, and a second heater 154.

  In S <b> 130, the fiber preform 110 is melted by the first heater 152. Thereby, the core rod 112 and the clad rod 113 are united. The fiber preform 110 at this stage is called an integrated rod.

  In S <b> 140, the fiber preform 110 is stretched by the pull pulley 81. At this time, the light leakage member applying device 153 sprays impurities at a constant interval from one direction of the melted fiber preform 110 (outside in the radial direction). The portion where the impurities are sprayed corresponds to the light leakage portion 104 (FIGS. 10 and 11) of the leakage optical fiber 101. Therefore, the light leakage portion 104 can be formed intermittently in the longitudinal direction and limited to a specific range in the circumferential direction. Here, the impurity is a gas containing germanium oxide, fluorine, or the like, a solid, a liquid, or a mixture thereof, and the refractive index of the cladding rod 113 can be increased by spraying on the cladding rod 113. The fiber preform 110 sprayed with impurities is heated again by the second heater 154 and sent to the diameter measuring device 61. Similar to the manufacturing method of the first embodiment, the fiber preform 110 passes through the diameter measuring device 61, the clad protective layer coating device 71, the plurality of pulleys 83, and the pulling pulley 81, and finally is wound on the winding bobbin 82. The leaky optical fiber 101 is manufactured.

  The leaky optical fiber 101 (FIGS. 10 and 11) according to the second embodiment described above includes the light leaking portion 104 intermittently in part in the circumferential direction and in the longitudinal direction. According to such a configuration, light propagating through the leaky optical fiber 101 travels in the core 102 while being reflected by the boundary portion between the core 102 and the clad 103 along the longitudinal direction of the leaky optical fiber 101. Of this light, part of the light incident on the light leaking part 104 leaks out of the leaking optical fiber 101 from the light leaking part 104. That is, the location where light leaks from the leaky optical fiber 101 can be made intermittent in the longitudinal direction within a specific range in the circumferential direction of the leaky optical fiber 101. Therefore, useless leakage of light can be reduced, and an optical signal can be propagated over a long distance. In addition, since scattering due to extra leaked light can be reduced, communication quality can be improved.

  Further, in the method of manufacturing the leaky optical fiber 101 according to the second embodiment, impurities are sprayed from the fiber preform 110 in one direction (outside in the radial direction) at regular intervals. For this reason, it is possible to easily form the light leakage portion 104 by intermittently limiting in the longitudinal direction and limiting to a specific range in the circumferential direction.

  A leaky optical fiber 201 according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 18 is a perspective view showing the configuration of the leaky optical fiber 201. The leaky optical fiber 201 includes a core 202, a clad 203, a light leak portion 204, and a clad protective layer (not shown). The core 202 is provided at the center of the leaky optical fiber 201. The clad 203 circumscribes the core 202. In contact with the core 202, a light leakage portion 204 is provided in a part of the core 202 in the circumferential direction. A clad protective layer (not shown) is made of a vinyl material or the like and is formed on the outer periphery of the clad 203. In the circumferential direction, no cladding protective layer is formed in the direction in which the light leakage portion 204 exists. In the leakage optical fiber 201, a plurality of light leakage portions 204 are provided along the longitudinal direction, for example, as light leakage portions 204A, 204B, and 204C. Regarding the light propagation direction, the light leakage portion 204A is the upstream side, and the light leakage portion 204C is the downstream side.

  FIG. 19 is a diagram illustrating the positions of the light leaking portions 204A, 204B, and 204C on the horizontal axis and the refractive index n of the light leaking portion on the vertical axis. Among the plurality of light leakage portions 204, the refractive index of the downstream light leakage portion 204 is configured to be higher than the refractive index of the upstream light leakage portion 204. For example, the refractive index of the light leakage part 204B is higher than the refractive index of the light leakage part 204A.

  In general, in a leaky optical fiber, light leaks from a light leaking portion, so that the amount of light propagating decreases toward the downstream side in the light propagation direction. Therefore, if the refractive index of the light leaking portion is constant, the amount of light leaking from the light leaking portion decreases as it goes downstream. In the above-described leaky optical fiber 201, by increasing the refractive index of the light leaking part 204 at a predetermined rate as it goes downstream in the light propagation direction, each light leaking part 204, for example, from the light leaking parts 204A, 204B, 204C. The amount of light leaking can be made constant. Thereby, stable optical communication can be achieved.

  A leaky optical fiber 301 according to a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 20 is a perspective view showing the configuration of the leaky optical fiber 301. Note that, in the fourth embodiment, the same members as those of the leaky optical fiber 201 of the third embodiment shown in FIG. In the leaky optical fiber 301, a plurality of light leaking portions 304 are provided along the longitudinal direction, such as light leaking portions 304A, 304B, and 304C. The circumferential length of the light leaking part 304 is d. Regarding the light propagation direction, the light leakage portion 304A is the upstream side, and the light leakage portion 304C is the downstream side.

  FIG. 12 is a diagram illustrating the positions of the light leaking portions 304A, 304B, and 304C on the horizontal axis and the circumferential length d of the light leaking portion 304 on the vertical axis. The circumferential length d of the downstream light leakage portion 304 among the plurality of light leakage portions 304 is configured to be larger than the circumferential length d of the upstream light leakage portion 304. For example, the circumferential length d of the light leakage portion 304B is larger than the circumferential length d of the light leakage portion 304A.

  In the above-described leaky optical fiber 301 according to the fourth embodiment, each light leak portion 304 is increased by increasing the circumferential length d of the light leak portion 304 at a predetermined rate as it goes downstream in the light propagation direction. For example, the amount of light leaking from the light leaking portions 304A, 304B, and 304C can be made constant. Thereby, stable optical communication can be achieved.

  A leaky optical fiber 401 and a manufacturing method thereof according to a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 22 is a perspective view showing the structure of the leaky optical fiber 401. FIG. 23 is a cross-sectional view of a surface cut in a direction orthogonal to the longitudinal direction of the leaky optical fiber 401. The leaky optical fiber 401 includes a core 402, a clad 403, a light leaking portion 404, and a clad protective layer 405. The notch mark 403a is provided by cutting a part of the outer periphery of the clad 403 into a substantially triangular shape. In the cross section, the notch mark 403 a is located on the opposite side to the light leakage portion 404 with respect to the core 402. Further, a protective layer notch mark 405a is provided in the clad protective layer 405 so as to cover the notch mark 403a. As shown in FIG. 23, the notch mark 403a is continuously formed in the longitudinal direction. Similarly, the protective layer cutout mark 405a is continuously provided in the longitudinal direction (the clad protective layer 405 is omitted in FIG. 22).

  A method for manufacturing the leaky optical fiber 401 will be described. In the method for manufacturing the leaky optical fiber 401, first, steps similar to steps S10 to S30 of the method for manufacturing the leaky optical fiber 1 shown in FIG. 4 are performed. Next, in this embodiment, a fiber stretcher 408 shown in FIG. 24 is used. In the fiber stretching device 408 of FIG. 24, the same members and devices as those of the fiber stretching device 8 of the first embodiment shown in FIG. The fiber stretching device 408 includes a diameter measuring device 61, a mark forming device 62, a clad protective layer coating device 71, and a protective layer mark device 72. The mark forming device 62 is a device for forming the notch mark 403 a in the fiber preform 10. The mark forming device 62 includes a notch die 430 shown in FIG. The notch mold 430 has a substantially donut shape in cross section. A triangular protrusion 431 is provided on a part of the inner circumference. The radius of the inner circle is substantially the same as the desired radius of the leaky optical fiber 401. The protective layer mark device 72 is a device for forming a protective layer notch mark 405 a in the fiber preform 10 coated with the cladding protective layer 405.

  In S <b> 40, the fiber preform 10 is melted using the fiber stretcher 408. In S50, a step of stretching the fiber preform 10 is performed. The fiber preform 10 winds the pull pulley 81 half a turn. Then, the fiber preform 10 is stretched by pulling the fiber preform 10 with the pull pulley 81. After passing through the diameter measuring device 61, the fiber preform 10 is sent to the mark forming device 62 to form a notch mark 403a. In the mark forming apparatus 62, the fiber preform is passed through the notch mold 430 shown in FIG.

  Similarly, also in the protective layer mark device 72, a protective layer notch mark 405a is formed in the clad protective layer 405. Finally, the fiber preform 10 is wound around the winding bobbin 82, and the leaky optical fiber 401 is manufactured. In this manner, the notch mark 403a is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the fiber preform 10, and the protective layer notch mark 405a is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding protective layer. Can do.

  In the cross section, the notch mark 403 a and the protective layer notch mark 405 a are located on the opposite side of the light leakage portion 404 with respect to the core 402. Thus, by confirming the notch mark 403a and the protective layer notch mark 405a, the position where the light leaking portion 404 of the leaking optical fiber 401 is formed can be specified in the circumferential direction. Therefore, when the leaking optical fiber 401 is laid, the light leaking portion 404 can be arranged in a desired direction.

  In the manufacturing method of the leaky optical fiber 401 according to the fifth embodiment, the notch mark 403a is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding rod 403 by passing the fiber preform through the notch die 430. Forming. For this reason, the notch mark 403a can be provided in the whole longitudinal direction of a leaky optical fiber with a simple structure.

  The marks formed on the clad 403 and the clad protective layer 405 are not limited to notch marks. The leaky optical fiber 501 of the sixth embodiment is provided with a flat mark 503a and a protective layer flat mark 505a as shown in FIGS. 26 and 27 instead of the notch mark 403a.

  FIG. 26 is a perspective view showing the structure of the leaky optical fiber 51. FIG. 27 is a cross-sectional view taken along a plane cut in a direction perpendicular to the longitudinal direction of the leaky optical fiber 501. The leaky optical fiber 501 includes a core 502, a clad 503, a light leaking part 504, and a clad protective layer 505. In the cross section, the flat mark 503 a is located on the opposite side of the light leakage portion 504 with respect to the core 502. Further, a protective layer flat mark 505a is provided on the clad protective layer 505 so as to cover the flat mark 503a. The flat mark 503a has a shape obtained by cutting the outer circumference circle of the clad 503 with a straight line connecting two points on the outer circumference circle. Similarly, the protective layer flat mark 505a has a shape obtained by cutting the outer circumferential circle of the cladding protective layer 505 with a straight line connecting two points on the outer circumferential circle. As shown in FIG. 26, the flat mark 503a is continuously provided in the longitudinal direction. Similarly, the protective layer flat mark 505a is continuously provided in the longitudinal direction (the clad protective layer 505 is omitted in FIG. 26).

  Further, in the manufacturing method of the leaky optical fiber 501, in the manufacturing method of the leaking optical fiber 401 of the fifth embodiment, a flat die 530 shown in FIG. 28 may be used instead of using the notch die 430. The flat mold 530 has a flat portion 531.

  The leaky optical fiber and the leaky optical fiber manufacturing method according to the present invention are not limited to the above-described embodiments, and various modifications and improvements can be made within the scope described in the claims. For example, in the fourth embodiment, instead of increasing the circumferential length d of the light leakage portion by a predetermined ratio, the length of the light leakage portion along the longitudinal direction of the leakage optical fiber is increased by a predetermined ratio. You may make it enlarge. Even with such a configuration, the amount of light leaking out can be made constant. Furthermore, the amount of light leaking out may be made constant by changing the refractive index and the size thereof at a predetermined ratio at the same time.

  The notch mark of the fifth embodiment and the flat mark of the sixth embodiment are formed on the opposite side of the light leakage portion by about 180 ° with respect to the circumferential direction. However, the position of each mark may be anywhere as long as it is a predetermined position in the circumferential direction of the leaky optical fiber.

  In each of the above-described embodiments, the clad protective layer is not necessarily provided.

It is a perspective view which shows the structure of the leaking optical fiber by the 1st Embodiment of this invention. It is sectional drawing by the surface which cut | disconnected the leakage optical fiber by 1st Embodiment in the direction orthogonal to a longitudinal direction. It is a graph which shows the refractive index distribution of the leaking optical fiber along the dashed-dotted line shown in FIG. It is a flowchart figure which shows the manufacturing method of the leaking optical fiber by 1st Embodiment. It is a perspective view of the core rod used for the manufacturing method of the leaking optical fiber by a 1st embodiment. It is a perspective view of the clad rod used for the manufacturing method of the leaky optical fiber by a 1st embodiment. It is a perspective view of a clad rod doped with a light leakage base material according to the first embodiment. It is a perspective view of the fiber preform | base_material used for the manufacturing method of the leaking optical fiber by 1st Embodiment. It is the schematic of the fiber extending | stretching apparatus used for the manufacturing method of the leaking optical fiber by 1st Embodiment. It is a perspective view which shows the structure of the leaking optical fiber by 2nd Embodiment. It is sectional drawing which cut | disconnected the leakage optical fiber by 2nd Embodiment in the direction orthogonal to a longitudinal direction. It is a graph which shows the refractive index distribution of the leaking optical fiber along the dashed-dotted line shown in FIG. It is a flowchart figure which shows the manufacturing method of the leaking optical fiber by 2nd Embodiment. It is a perspective view of the core rod used for the manufacturing method of the leaking optical fiber by a 2nd embodiment. It is a perspective view of the clad rod used for the manufacturing method of the leaky optical fiber by a 2nd embodiment. It is a perspective view of the fiber preform | base_material used for the manufacturing method of the leaking optical fiber by 2nd Embodiment. It is the schematic of the fiber extending | stretching apparatus used for the manufacturing method of the leaking optical fiber by 2nd Embodiment. It is a perspective view which shows the structure of the leaking optical fiber by 3rd Embodiment. It is a graph which shows the relationship between each light leakage part and refractive index of the leakage optical fiber by 3rd Embodiment. It is a perspective view which shows the structure of the leaking optical fiber by 4th Embodiment. It is a graph which shows the relationship between the length of the circumferential direction of each light leak part and leak part of the leaking optical fiber by 4th Embodiment. It is a perspective view which shows the structure of the leaking optical fiber by 5th Embodiment. It is sectional drawing which cut | disconnected the leakage optical fiber by 5th Embodiment in the direction orthogonal to a longitudinal direction. It is the schematic of the fiber extending | stretching apparatus used for the manufacturing method of the leaking optical fiber of 5th Embodiment. It is sectional drawing of the notch type for forming the notch mark used for the manufacturing method of the leakage optical fiber of 5th Embodiment. It is a perspective view which shows the structure of the leaking optical fiber of 6th Embodiment. It is sectional drawing which cut | disconnected the leakage optical fiber of 6th Embodiment in the direction orthogonal to a longitudinal direction. It is sectional drawing of the flat type for forming the flat mark used for the manufacturing method of the leaky optical fiber of the 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Leakage optical fiber, 2 ... Core, 2a ... Refractive index shape,
3 ... cladding, 3a ... refractive index shape, 4 ... light leakage part,
4a ... refractive index shape, 5 ... clad protective layer,
8 ... Fiber stretching device, 10 ... Fiber preform, 12 ... Core rod,
13 ... clad rod, 14 ... light leakage base material,
101 ... Leakage optical fiber, 102 ... Core, 102 ... Cladding,
102a ... refractive index shape, 103 ... clad,
103a ... refractive index shape, 104 ... light leakage part,
104a ... refractive index shape, 108 ... fiber stretching device,
110: Fiber base material, 112: Core rod,
113 ... clad rod, 201 ... leaking optical fiber,
202 ... Core, 203 ... Cladding, 204 ... Light leakage part,
205 ... cladding protective layer, 301 ... leaking optical fiber,
304 ... light leakage part, 305 ... clad protective layer,
401 ... Leakage optical fiber, 402 ... Core, 403 ... Cladding,
403 ... clad rod, 403a ... notch mark,
404 ... light leakage part, 405 ... clad protective layer,
405a ... protective layer notch mark,
408 ... Fiber stretching device, 430 ... Notch type,
501 ... Leakage optical fiber, 502 ... Core, 503 ... Cladding,
503a: flat mark, 504: light leakage part,
505 ... Clad protective layer, 505a ... Protective layer flat mark 530 ... Flat type.

Claims (11)

The core,
A cladding having a lower refractive index than the core and circumscribing the core;
A light leakage portion formed in contact with the core, having a refractive index lower than that of the core and higher than that of the cladding, and a plurality of light leakage portions intermittently provided in the longitudinal direction of the core. Leaky optical fiber.   The leaking optical fiber according to claim 1, wherein the light leakage portion is formed only in a part of the circumferential direction.   The leaked light according to claim 1 or 2, wherein, of the two adjacent light leaking portions, the light leaking portion on the downstream side in the light propagation direction has a higher refractive index than the light leaking portion on the upstream side. fiber.   4. The leakage according to claim 1, wherein, of the two adjacent light leakage portions, the light leakage portion on the downstream side in the light propagation direction is larger in size than the light leakage portion on the upstream side. Optical fiber.   5. The leaky optical fiber according to claim 1, wherein a mark is provided at a predetermined position in the circumferential direction of the outer peripheral surface of the clad. Preparing a core rod to be a core material of the core and a plurality of cladding rods to be a base material of the cladding in which holes having substantially the same diameter as the core rod are formed on the central axis;
For each of the cladding rods, a step of creating a cladding rod doped with an impurity that changes the base material into a light leakage portion in a part of the longitudinal direction of the innermost surface layer of the pores;
A step of creating an assembly rod by inserting the core rod into holes of a plurality of clad rods doped with the impurities;
Melting the assembly rod and creating an integrated rod;
A leaky optical fiber manufacturing method comprising a step of drawing an integrated rod in a molten state.   7. The leakage light according to claim 6, wherein in the step of producing the cladding rod doped with impurities, each of the cladding rods is doped with impurities only in a part in the circumferential direction of the innermost surface layer of the pores. Fiber manufacturing method.   The mark is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the clad rod by passing the integrated rod through a mold in the step of stretching the integrated rod. Leaky optical fiber manufacturing method. Preparing a core rod as a base material of the core, and a clad rod as a base material of a clad in which a hole having substantially the same diameter as the core rod is formed in the central axis;
Creating an assembly rod by inserting the core rod into the hole of the cladding rod; and
Melting the assembly rod and creating an integrated rod;
A method for producing a leaky optical fiber comprising a step of stretching the integrated rod,
A method for producing a leaky optical fiber, wherein in the step of stretching the integrated rod, impurities are intermittently doped in the longitudinal direction of the integrated rod.   10. The method of manufacturing a leaky optical fiber according to claim 9, wherein in the step of stretching the integrated rod, impurities are doped only in a part of the integrated rod in the circumferential direction.   11. The mark according to claim 9, wherein, in the step of stretching the integrated rod, a mark is formed at a predetermined position in the circumferential direction of the outer peripheral surface of the cladding rod by passing the integrated rod through a mold. Leaky optical fiber manufacturing method.

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