JP2012137615A - Optical fiber manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing an optical fiber having a pore extending along a longitudinal direction and further having a desired characteristics with excellent yields.SOLUTION: An optical fiber manufacturing method according to the present invention comprises: a core member exterior cutting process forming a groove extending on an outer periphery of a core member in a longitudinal direction (1); a fixing process inserting the core member into a pipe member so as to fix the core member and the pipe member to each other at one point or a plurality of points including a first end side of the core member after the core member exterior cutting process (2); an optical fiber drawing process holding the core member and the pipe member such that the first end side thereof is turned upward and executing the optical fiber drawing process of the core member and the pipe member from a second end side thereof while pressuring a space between the core member and the pipe member so as to manufacture an optical fiber after the fixing process (3). It is preferable that a glass block having a diameter larger than an inner diameter of the pipe member is fixed to the first end side of the core member so as to insert the core member into the pipe member and fix the core member and the pipe member to each other through the glass block during the fixing process.

Description

  The present invention relates to a method of manufacturing an optical fiber having holes extending in the longitudinal direction.

  An optical fiber having a hole extending in the longitudinal direction can have various characteristics that a solid optical fiber cannot have. As a method for producing such an optical fiber, a core material cutting method and a base material drilling method are known. In the core material cutting method, a groove extending in the longitudinal direction is formed on the outer periphery of the core material, the core material is inserted into a pipe material, the two are heated and integrated, and then drawn. An optical fiber having holes extending in the longitudinal direction is manufactured (see Patent Documents 1 and 2). In the base material drilling method, a hole extending in the longitudinal direction is formed in the base material, and an optical fiber in which the hole extends in the longitudinal direction is manufactured by drawing the base material.

JP 2002-321935 A JP 2003-342031 A

  In the core material cutting method, voids do not remain in the base material when collapse is performed at a high temperature. Therefore, it is necessary to perform collapse at a low temperature in order to leave holes. When collapsing is performed at a low temperature, the interface between the core material and the pipe material cannot be sufficiently heated, and distortion tends to remain in this portion, thereby increasing the risk of cracking the base material. Further, since the core material is deformed by heating during the collapse, the size of the holes in the longitudinal direction in the base material is not stable. Therefore, the core material cutting method cannot manufacture an optical fiber having desired characteristics with a high yield.

  In the base material drilling method, a long drilling tool is required to form a long hole in the base material. The longer the base material is, the less rigid the tool is, so it is difficult to make a hole straight in the base material. Therefore, the base material drilling method also cannot produce an optical fiber having desired characteristics with a high yield.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method capable of producing an optical fiber having desired characteristics with holes extending in the longitudinal direction with high yield. To do.

  An optical fiber manufacturing method of the present invention is a method of manufacturing an optical fiber in which holes extend in the longitudinal direction, and (1) core material external cutting that forms a groove extending in the longitudinal direction on the outer periphery of the core material. And (2) a fixing step of inserting the core material into the pipe material after the core material cutting step, and fixing the core material and the pipe material to each other at one or a plurality of locations including the first end side of the core material; (3) After the fixing process, hold the core material and the pipe material so that the first end side is on the upper side, and press the space between the core material and the pipe material while the core material and the pipe material are on the second end side. And a drawing step of drawing an optical fiber by drawing from the wire.

  In the optical fiber manufacturing method of the present invention, in the fixing step, a glass block having a diameter larger than the inner diameter of the pipe material is fixed to the first end of the core material, the core material is inserted into the pipe material, and the glass block is inserted. It is preferable to fix the core material and the pipe material to each other. Alternatively, in the fixing step, it is also preferable that the core material and the pipe material are fixed to each other by heating and integrating the core material and the pipe material on the first end side.

  In the optical fiber manufacturing method of the present invention, the viscosity of the core material may be lower than the viscosity of the pipe material, or the viscosity of the core material may be higher than the viscosity of the pipe material. If the viscosity of the core material is lower than the viscosity of the pipe material, the roughness of the inner surface of the fiber hole can be reduced even with the same drawing tension during the drawing process. If the viscosity of the core material is higher than the viscosity of the pipe material, the change in the hole diameter due to the application of the internal pressure during the drawing process is reduced, and the merit that the controllability of the hole diameter is improved can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the void | hole extends in a longitudinal direction and the optical fiber which has a desired characteristic can be manufactured with a sufficient yield.

It is a figure which shows the flow of the optical fiber manufacturing method of a 1st comparative example. It is a figure which shows the shape of the core material 10 before an external cutting. It is a figure which shows the shape of the core material 10 after an external cutting. FIG. 3 is a diagram showing a cross-sectional shape of a pipe material 20. It is a figure which shows the cross-sectional shape of the preform | base_material 1 after heat-integrating the core material 10 and the pipe material 20 in the optical fiber manufacturing method of a 1st comparative example. It is a figure which shows the flow of the optical fiber manufacturing method of a 2nd comparative example. It is a figure which shows the cross-sectional shape of preform | base_material 2A before drilling in the optical fiber manufacturing method of a 2nd comparative example. It is a figure which shows the cross-sectional shape of the preform | base_material 2 after the drilling in the optical fiber manufacturing method of a 2nd comparative example. It is a figure which shows the flow of the optical fiber manufacturing method of a 3rd comparative example. It is a figure which shows the cross-sectional shape of the preform | base_material 3 in the optical fiber manufacturing method of a 3rd comparative example. It is a figure which shows the flow of the optical fiber manufacturing method of 1st Embodiment. It is a figure explaining the fixing process of the optical fiber manufacturing method of 1st Embodiment. It is a figure explaining the fixing process of the optical fiber manufacturing method of 1st Embodiment. It is a figure explaining the drawing process of the optical fiber manufacturing method of 1st Embodiment. It is a figure which shows the flow of the optical fiber manufacturing method of 2nd Embodiment. It is a figure explaining the fixing process of the optical fiber manufacturing method of 2nd Embodiment. It is a figure explaining the drawing process of the optical fiber manufacturing method of 2nd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the optical fiber manufacturing method of the comparative example will be described first, and then the optical fiber manufacturing method of the present embodiment will be described.

  First, the optical fiber manufacturing method of the first comparative example will be described. FIG. 1 is a diagram illustrating a flow of the optical fiber manufacturing method of the first comparative example. The optical fiber manufacturing method of the first comparative example is a method of manufacturing an optical fiber in which holes extend in the longitudinal direction based on the core material cutting method.

  In the optical fiber manufacturing method of the first comparative example, first, a core material 10 made of quartz glass is prepared. As shown in FIG. 2, the core material 10 before external cutting includes a first core portion 11 to be an optical fiber core and a second core portion 12 surrounding the first core portion 11. FIG. 2A shows a cross-section of the core material 10 before cutting, and FIG. 2B shows the outer shape of the core material 10 before cutting.

  A groove 30 extending in the longitudinal direction is formed on the outer periphery of the core material 10. FIG. 3A shows a cross section of the core material 10 after the external cutting, and FIG. 3B shows an outer shape of the core material 10 after the external cutting. The depth of the groove 30 is set so as not to reach the first core portion 11.

  In addition, a pipe member 20 made of quartz glass is prepared. The inner diameter of the pipe material 20 is slightly larger than the outer diameter of the core material 10. FIG. 4 is a diagram illustrating a cross-sectional shape of the pipe material 20.

  Then, the core material 10 after the external cutting is inserted into the pipe material 20, and both are integrated by heating and collapsed to produce the base material 1. FIG. 5 is a diagram showing a cross-sectional shape of the base material 1. The groove 30 extending in the longitudinal direction in the core material 10 after the external cutting becomes a hole 31 extending in the longitudinal direction in the base material 1. By drawing the base material 1, an optical fiber having holes extending in the longitudinal direction is manufactured.

  The optical fiber manufacturing method (core material cutting method) of the first comparative example has an advantage that it is easy to increase the length. However, the optical fiber manufacturing method of the first comparative example needs to be collapsed at a low temperature in order to leave holes. When collapsing is performed at a low temperature, the interface between the core material and the pipe material cannot be sufficiently heated, and distortion tends to remain in this portion, thereby increasing the risk of cracking the base material. Further, since the core material is deformed by heating during the collapse, the size of the holes in the longitudinal direction in the base material is not stable. Therefore, the optical fiber manufacturing method of the first comparative example cannot manufacture an optical fiber having desired characteristics with a high yield.

  Next, an optical fiber manufacturing method of the second comparative example will be described. FIG. 6 is a diagram illustrating a flow of the optical fiber manufacturing method of the second comparative example. The optical fiber manufacturing method of the second comparative example is a method for manufacturing an optical fiber in which holes extend in the longitudinal direction based on a preform drilling method.

  In the optical fiber manufacturing method of the second comparative example, first, a core material 10 made of quartz glass (FIG. 2) and a pipe material 20 made of quartz glass (FIG. 4) are prepared. Then, the core material 10 is inserted into the pipe material 20, and both are heated and integrated to be collapsed to produce the base material 2A. FIG. 7 is a diagram showing a cross-sectional shape of the base material 2A. Further, a hole 32 extending in the longitudinal direction is formed in the base material 2A, and the base material 2 is manufactured. FIG. 8 is a diagram showing a cross-sectional shape of the base material 2. By drawing the base material 2, an optical fiber having holes extending in the longitudinal direction is manufactured.

  The optical fiber manufacturing method (base material drilling method) of the second comparative example requires a long drilling tool in order to form long holes in the base material. The longer the base material is, the less rigid the tool is, so it is difficult to make a hole straight in the base material. Therefore, the optical fiber manufacturing method of the second comparative example cannot manufacture an optical fiber having desired characteristics with a high yield.

  Next, an optical fiber manufacturing method of the third comparative example will be described. FIG. 9 is a diagram illustrating a flow of the optical fiber manufacturing method of the third comparative example. The optical fiber manufacturing method of the third comparative example is a method of manufacturing an optical fiber in which holes extend in the longitudinal direction based on rod-in drawing.

  The optical fiber manufacturing method of the third comparative example is similar to the optical fiber manufacturing method of the first comparative example, but the core material 10 and the pipe material 20 are not heated and integrated before drawing. As shown in FIG. 10, the base material 3 at the time of drawing is only the core material 10 inserted into the pipe material 20.

  In the optical fiber manufacturing method (rod-in drawing) of the third comparative example, the risk of the base material 3 breaking is extremely low. However, in the optical fiber manufacturing method of the third comparative example, the core material 10 melts down in the pipe material 20 or the core material 10 is pushed out of the pipe material 20 during drawing. There is a demerit that it is easy to do.

  The optical fiber manufacturing method of the first embodiment or the second embodiment described below can solve the problems of the optical fiber manufacturing methods of the first to third comparative examples.

  Next, an optical fiber manufacturing method according to the first embodiment will be described. FIG. 11 is a diagram illustrating a flow of the optical fiber manufacturing method according to the first embodiment. The optical fiber manufacturing method of the first embodiment includes a core material cutting process, a fixing process, and a drawing process. In the core material cutting process, a groove 30 extending in the longitudinal direction is formed on the outer periphery of the core material 10 as in the first comparative example and the third comparative example (FIGS. 2 and 3).

  In the fixing process subsequent to the core material cutting process, the core material 10 is inserted into the pipe material 20, and the core material 10 and the pipe material 20 are fixed to each other on the first end side of the core material 10. Specifically, the fixing process is as follows. FIG. 12 and FIG. 13 are diagrams for explaining a fixing process of the optical fiber manufacturing method of the first embodiment.

  As shown in FIGS. 12A and 12B, a glass block 40 having a diameter larger than the inner diameter of the pipe material 20 is fixed to the first end of the core material 10. Further, as shown in FIG. 13A, the dummy pipe 50 is connected to the first end of the pipe 20 so as to be coaxial, and the dummy rod 60 is coaxially connected to the second end of the pipe 20. Connected. As shown in FIGS. 13B and 13C, the core material 10 is inserted into the pipe material 20 through the dummy pipe 50. At this time, the glass block 40 contacts the first end of the pipe 20. 13D, a part of the dummy pipe 50 is reduced in diameter, and the core material 10 and the pipe material 20 are connected to the first end side via the glass block 50 by the reduced diameter portion 51. Are fixed to each other. Thereby, the base material 4 is produced.

  In the drawing process following the fixing process, as shown in FIG. 14, the base material 4 including the core material 10 and the pipe material 20 is held so that the first end side is up, and the core material 10 and the pipe material 20 While the space between is pressed, the core material 10 and the pipe material 20 are drawn from the second end side. Thereby, the optical fiber 9 in which holes extend in the longitudinal direction is manufactured.

  In the optical fiber manufacturing method of the first embodiment, during the drawing process, the base material 4 is held so that the first ends where the core material 10 and the pipe material 20 are fixed to each other are on the top, and the core material 10 Is fixed to the pipe member 20 at the first end, which is the upper end, and supported by the dummy rod at the lower end. Therefore, in the drawing process, problems such as the core material 10 being melted by its own weight or the core material 10 being pushed out of the pipe 20 can be avoided. Further, in the optical fiber manufacturing method of the first embodiment, the problem of the base material cracking and the non-uniformity of the hole size in the longitudinal direction, which the optical fiber manufacturing method (core material cutting method) of the first comparative example has, are solved. Is done. Therefore, the optical fiber manufacturing method according to the first embodiment can manufacture an optical fiber having desired characteristics with holes extending in the longitudinal direction with high yield.

  In particular, if the viscosity of the core material 10 is made smaller than that of the pipe material 20, the roughness of the inner surface of the fiber hole can be reduced even with the same drawing tension, leading to a reduction in transmission loss. Conversely, if the viscosity of the core material 10 is made larger than that of the pipe material 20, the change in the hole diameter due to the application of the internal pressure is reduced, and the merit that the controllability of the hole diameter is improved can be obtained.

  Next, an optical fiber manufacturing method according to the second embodiment will be described. FIG. 15 is a diagram illustrating a flow of the optical fiber manufacturing method according to the second embodiment. The optical fiber manufacturing method of the second embodiment includes a core material cutting process, a fixing process, and a drawing process. In the core material cutting process, a groove 30 extending in the longitudinal direction is formed on the outer periphery of the core material 10 as in the first comparative example and the third comparative example (FIGS. 2 and 3).

  In a fixing process subsequent to the core material cutting process, the core material 10 is inserted into the pipe material 20, and the core material 10 and the pipe material 20 are fixed to each other at least on the first end side of the core material 10. Specifically, the fixing process is as follows. FIG. 16 is a diagram illustrating a fixing process of the optical fiber manufacturing method according to the second embodiment.

  As shown in FIG. 16A, the dummy pipe 50 is connected to the first end of the pipe 20 so as to be coaxial, and the dummy rod 60 is connected to the second end of the pipe 20 so as to be coaxial. The As shown in FIG. 16B, the core material 10 is inserted into the pipe material 20 through the dummy pipe 50. Then, as shown in FIG. 16C, the core material 10 and the pipe material 20 are heated and integrated by heating by the heating source 71 on the first end side and fixed to each other. At this time, as long as the groove 30 is not completely crushed in the fixed portion, the deformation of the groove 30 (hole 31) is not a problem. Further, the core material 10 and the pipe material 20 may be heated and integrated by heating by the heating source 72 on the second end side and fixed to each other. (Further, when the size of the core material 10 is large, the core material 10 and the pipe material 20 may be heated and integrated by heating by the heating source 72 even at one or a plurality of locations in the intermediate portion.) Thereby, the base material 5 is produced.

  In the drawing process following the fixing process, as shown in FIG. 17, the base material 5 including the core material 10 and the pipe material 20 is held so that the first end side is up, and the core material 10 and the pipe material 20 While the space between is pressed, the core material 10 and the pipe material 20 are drawn from the second end side. Thereby, the optical fiber 9 in which holes extend in the longitudinal direction is manufactured.

  In the optical fiber manufacturing method of the second embodiment, during the drawing process, the base material 5 is held so that the first end where the core material 10 and the pipe material 20 are fixed to each other is on the upper side, and the core material 10 Is fixed to the pipe member 20 at the first end, which is the upper end, and supported by the dummy rod at the lower end. (Or, the lower end is fixed to the pipe material 20). Therefore, in the drawing process, problems such as the core material 10 being melted by its own weight or the core material 10 being pushed out of the pipe 20 can be avoided. Further, in the optical fiber manufacturing method of the second embodiment, the problem of the base material cracking and the non-uniformity of the pore size in the longitudinal direction which the optical fiber manufacturing method (core material cutting method) of the first comparative example has been solved. Is done. Therefore, the optical fiber manufacturing method of the second embodiment can manufacture an optical fiber having desired characteristics with holes extending in the longitudinal direction with a high yield.

  Also in the second embodiment, if the viscosity of the core material 10 is made smaller than that of the pipe material 20, the roughness of the inner surface of the fiber hole can be reduced even with the same linear tensile force, leading to a reduction in transmission loss. Conversely, if the viscosity of the core material 10 is made larger than that of the pipe material 20, the change in the hole diameter due to the application of the internal pressure is reduced, and the merit that the controllability of the hole diameter is improved can be obtained.

DESCRIPTION OF SYMBOLS 1-5 ... Base material, 9 ... Optical fiber, 10 ... Core material, 20 ... Pipe material, 30 ... Groove, 31, 32 ... Hole, 40 ... Glass block, 50 ... Dummy pipe, 60 ... Dummy rod.

Claims (5)

A method of manufacturing an optical fiber having holes extending in a longitudinal direction,
A core material cutting process for forming a groove extending in the longitudinal direction on the outer periphery of the core material;
After the core material cutting operation, the core material is inserted into the pipe material, and a fixing step of fixing the core material and the pipe material to each other at one or a plurality of locations including the first end side of the core material;
After the fixing step, the core material and the pipe material are held so that the first end side is up, and the space between the core material and the pipe material is pressed while the core material and the pipe material are A drawing process for producing an optical fiber by drawing from the second end side;
An optical fiber manufacturing method comprising:   In the fixing step, a glass block having a diameter larger than the inner diameter of the pipe material is fixed to the first end of the core material, the core material is inserted into the pipe material, and the core is inserted through the glass block. The optical fiber manufacturing method according to claim 1, wherein the material and the pipe material are fixed to each other.   2. The optical fiber according to claim 1, wherein in the fixing step, the core material and the pipe material are heated and integrated on the first end side to fix the core material and the pipe material to each other. Production method.   The optical fiber manufacturing method according to claim 1, wherein the viscosity of the core material is lower than the viscosity of the pipe material. The optical fiber manufacturing method according to claim 1, wherein the viscosity of the core material is higher than the viscosity of the pipe material.

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