JP2005242086A - Multicore fiber and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multicore fiber having satisfactory roundness and alignment accuracy of core. <P>SOLUTION: The end part of a plurality of fine core preforms which are bound into a bundle is inserted into a first quartz tube, the quartz tube is heated and fused, the fine core preforms are elongated and cut and, thereby, the fine core preforms of which both ends are fused are obtained. Subsequently, a plurality of the fine core preforms of which both ends are fused are inserted into a second quartz tube, the second quartz tube is successively heated from one end side toward the other end side, is fused, thereby, the second quartz tube and a plurality of the fine core preforms are fused integrally, the multicore preform is produced and the multicore fiber is produced through fusion/spinning. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multicore fiber having a plurality of cores in one optical fiber and a method for manufacturing the same.

  A multi-core fiber in which a plurality of cores are provided in one optical fiber is used for an application in which a plurality of optical signals are transmitted through one optical fiber. Recently, multi-core fibers are also used for sensors.

  As a conventional multi-core fiber manufacturing method, a core rod (co-apply foam) having a core and a clad added with a rare earth element is inserted into a quartz tube, and these are heated and melted to be fused and fused together. A method of making a reform and drawing it is known (for example, Patent Document 1).

Further, in a method of manufacturing a multi-core fiber preform in which a plurality of single-core glass rods are gathered and assembled in a quartz tube, and then a composite member composed of the glass rod and the quartz tube is collapsed and integrated, There is known a manufacturing method of a multi-core fiber preform that collapses after filling a gap with a small-diameter glass rod (for example, Patent Document 2).
Japanese Patent Laid-Open No. 9-5543 JP 59-217632 A Japanese Patent Laid-Open No. 55-21087

  When using a multi-core fiber as a sensor, the roundness of the core and the accuracy of the relative position between the cores are required. However, according to the conventional multi-core fiber manufacturing method, it is extremely difficult to satisfy these requirements. It was difficult.

  The present invention has been made in view of these points, and an object of the present invention is to provide a multicore fiber with high accuracy of the roundness of the core and the relative position interval thereof, and a method for manufacturing the same. .

  According to the present invention, (a) a co-appli foam is heated and stretched and cut into a predetermined length to produce a plurality of small-diameter co-appli foams, and (b) the plurality of small-diameter co-appli foams are bundled. (C) One end portion of the bundled small diameter co-appli foams is inserted into the first quartz tube, and (d) the first portion of the portion where the plurality of small diameter co-preforms is inserted. (1) Steps (c) and (d) are carried out by fusing the one end of the small-sized co-appli foam by heating and melting the quartz tube of 1 and drawing and cutting the small-sized co-appli foam. Repeat for the other ends of the bundled small diameter co-appli foams, and (f) insert the plural small co-appli foams fused at both ends into the second quartz tube, (g ) Sequentially heating the second quartz tube from one end to the other (H) the multi-core foam is manufactured by fusing together the second quartz tube and the plurality of small-diameter core foams by fusing together with the plurality of small core diameter foams. There is provided a method for producing a multi-core fiber, comprising the steps of melting and spinning a preform.

  Preferably, prior to step (f), (i) a plurality of dummy fibers are bundled at substantially equal intervals around the plurality of small diameter co-appliforms fused at both ends; One end of the bundled plurality of dummy fibers and the narrow diameter preform is inserted into a third quartz tube, and (k) the third quartz tube at the portion where the plurality of dummy fibers are inserted (1) the step (1), wherein the dummy fiber is fused to the one end portion of the small diameter co-prime foam by heating and melting, and the dummy fiber is stretched and cut together with the plurality of small diameter co-prime foams. Each step further includes repeating steps j) and (k) for the other end portion of the small-diameter co-prime foam around which the plurality of dummy fibers are bundled.

  According to still another aspect of the present invention, a cylindrical glass matrix, a plurality of cores fused and embedded at substantially the same interval in the center of the cylindrical glass matrix, and substantially the same around the plurality of cores There is provided a multi-core fiber comprising a plurality of dummy fibers arranged at equal intervals on the circumference and fused and embedded in the cylindrical glass matrix.

  Preferably, the plurality of cores include a first core disposed at the center of the cylindrical glass matrix, and a plurality of second cores disposed at substantially the same circumference and at the same interval around the first core. Is included.

  According to the manufacturing method of the multi-core fiber of the present invention, since both ends are fused, a plurality of small diameter co-appli foams are inserted into a quartz tube and heated to be fused and integrated. In addition, a multi-core fiber with good core alignment accuracy can be provided.

  By bundling a plurality of dummy fibers at substantially equal intervals around a plurality of small diameter co-prime foams fused at both ends, inserting them into a quartz tube and heat-sealing them, Since it acts as a protective member, the roundness of the core and the core alignment accuracy can be further improved.

Referring to FIG. 1, there is shown a schematic configuration of a preform manufacturing apparatus that can be used for carrying out a method for manufacturing a core member (co-appli foam). Reference numeral 2 is a lathe for glass production that rotatably supports the quartz reaction tube 4, and 6 is a burner for reciprocating the longitudinal direction of the quartz reaction tube 4 on the lathe 2 to heat the quartz reaction tube 4 from the outside. , 8 is a temperature control device that controls the combustion state of the burner 6 by adjusting the flow rate of O ₂ and H ₂ supplied to the burner 6.

A gas supply pipe 12 is connected to the connector 10 connected to the end of the quartz reaction tube 4, and a raw material gas such as SiCl ₄ or O ₂ is supplied into the quartz reaction tube 4 through the gas supply pipe 12. Is sent to.

14 is a SiCl ₄ supply device, 16 is a GeCl ₄ supply device, 18 is a POCl ₃ supply device, and the supply amount is controlled by the flow rate of a carrier gas such as O ₂ fed through the mass flow meter 20. Reference numeral 22 denotes a gas cylinder containing SF ₆ , and SF ₆ gas is introduced into the gas supply pipe 12 by opening the valve 24.

  The connecting portion between the gas supply pipe 12 and the quartz reaction tube 4 via the connector 10 is sealed by a normal method, thereby ensuring a closed system inside the quartz reaction tube 4. It is like that.

First, SiCl ₄ , POCl ₃ , and SF ₆ gas are sent to the quartz reaction tube 4, and PF—SiO ₂ -based clad glass is deposited in the quartz reaction tube 4.

Next, when the quartz reaction tube 4 is heated by the burner 6 from the outside while rotating the quartz reaction tube 4 into which the raw material gas containing SiCl ₄ and GeCl ₄ and the carrier gas are being fed, The core oxide glass fine powder is deposited, and the fine powder is immediately vitrified by heating with the burner 6.

By reciprocating the burner 6 a plurality of times, a core layer having a predetermined refractive index and a predetermined thickness made of SiO ₂ doped with GeO ₂ is uniformly formed on the inner wall of the quartz reaction tube 4.

  After depositing the core layer on the inner wall of the quartz reaction tube 4 in this way, heating by the burner 6 and reciprocation thereof are performed, and after passing through the intermediate collapse of the quartz reaction tube 4, heating to a higher temperature until the hollow part disappears. When completely collapsed, a co-appli form 28 as shown in FIG. 2 can be obtained.

With reference to FIG. 2, the manufacturing method of a small diameter co-appli foam is demonstrated roughly. The co-appli foam 28 has a Ge-doped core 30 and a clad 32 doped with P and F. Here, the reason why SiO ₂ is doped with P and F is to soften the clad 32.

  The co-appli foam 28 is heated and stretched to produce a thin co-appli foam 34 having an outer diameter of about 1.7 mm, and this is cut into a predetermined length with pliers or the like.

  Next, as shown in FIG. 3, one small diameter co-appli foam 34 is arranged at the center, and bundled so that the six small diameter co-appli foams 34 surround the tape 38 as shown in FIG. The co-appli foam bundle 36 is obtained by temporarily fixing with.

  As shown in FIG. 4, while the co-appli foam bundle 36 is held by the glass lathe chuck 40, the co-appli foam bundle 36 is moved in the X direction, and the co-form foam bundle 36 is inserted into the dummy quartz tube 42 held by the glass lathe chuck 44. The end of the application form bundle 36 is inserted. At this time, a dummy quartz tube 42 is selected in which the inner diameter of the dummy quartz tube 42 is slightly larger than the outer diameter of the co-appli foam bundle 36.

  Next, as shown in FIG. 5, the overlapping portion of the co-appli foam bundle 36 and the dummy quartz tube 42 is heated and melted by the oxyhydrogen burner 46 while rotating the dummy quartz tube 42.

  Next, when the co-appli foam bundle 36 is pulled in the direction of arrow Y in FIG. 6 while continuing the heating by the burner 46, one end portion 36a of the co-appli foam bundle 36 is stretched in a taper shape and fixed by fusion. Similarly, one end portion 42a of the dummy quartz tube 42 is also tapered.

  When the same heat-stretching and fusion treatment is performed on the other end portion of the co-appli foam bundle 36, a co-appli foam bundle 36 as shown in FIG. 7 in which both ends 36a and 36b are fused and fixed is obtained.

  As described above, when the end portion of the co-appli foam bundle 36 is inserted into the dummy quartz tube 42 and heated and stretched by the burner 46, the end portions 36a and 36b of the co-appli foam bundle 36 can be fused and fixed in a tapered shape. However, FIG. 8 shows a comparative example in which heating is performed without using a dummy quartz tube.

  As shown in FIG. 8A, when the end portion of the co-appli foam bundle 36 is heated and fused by the oxyhydrogen burner 46, the end portion of the co-appli foam bundle 36 is shown in FIG. 8B. 36a 'is scattered and it is difficult to fix by fusion.

  In the preferred embodiment of the present invention, a plurality of (12 in this embodiment) dummy fibers 48 are further provided on the co-appli foam bundle 36 shown in FIG. Bundle. Here, the term “dummy fiber” used in the specification and claims refers to a clad-only glass rod having no core.

  After temporarily fixing a composite fiber bundle 50 in which a plurality of small diameter co-appli foams 34 and a plurality of dummy fibers 48 are bundled with a tape, the heating and stretching and fusion step shown in FIGS. Execute.

  When this heat-stretching and fusion step is executed for both ends of the composite fiber bundle 50, a composite fiber bundle 50 having both ends 50a and 50b fused and fixed as shown in FIG. 10 is obtained.

  As shown in FIG. 9, the dummy fibers 48 are bundled around the small-diameter co-appli foam 34 to prevent uneven deformation of the small-diameter co-prime foam in the drawing and fusing step, which will be described later. The purpose is to protect the application form, whereby a multi-core fiber with high core roundness and alignment accuracy can be manufactured.

  As shown in FIG. 10, the composite fiber bundle 50 is inserted into the quartz tube 52, and the composite fiber bundle 50 is supported in the quartz tube 52 by a pair of protrusions 53 (only one is shown). The protrusion 53 is formed by partially melting the quartz tube 52 with the oxyhydrogen burner 46. For the quartz tube 52, a quartz tube whose inner diameter is slightly larger than the outer diameter of the composite fiber bundle 50 is selected.

  The quartz tube 52 is heated by the oxyhydrogen burner 46 while rotating the quartz tube 52. While moving the burner 46 in the arrow X direction from one end side to the other end side of the quartz tube 52, the quartz tube 52 and the composite fiber bundle 50 are melted and integrated so that no bubbles remain.

  Next, a quartz tube is put on the melted and integrated in this way, and it is heated and melted by a burner and integrated again. This covering pipe extending step is repeated a plurality of times, and finally a multi-co-appli foam having a desired outer diameter is manufactured.

  FIG. 12 (A) is an enlarged cross-sectional photograph of a multi-copier foam manufactured by the method of the present invention, and FIG. 12 (B) is an enlarged cross-sectional photograph when the co-appli foam bundle is integrated without fixing both ends.

  Reference numeral 35 denotes a core portion. In the multico-appli foam manufactured by the method of the present invention shown in FIG. 12A, the spacing error between the seven cores 35 is ± 2% or less, and the cross section of each core 35 is true. It has a shape close to a circle.

  On the other hand, in the multi-co-appli foam manufactured by the conventional method shown in FIG. 12B, the cross-sectional shape of the core 35 is clearly deformed, and the error of the core interval is about ± 10%, which is a considerable error. It has become.

  FIG. 13 is a schematic diagram of a drawing apparatus for drawing the multi-coappli foam 54 to the multi-core fiber. The multi-co-appli foam 54 is supported by the preform feeding unit 56 and gradually fed downward, and the lower end portion of the multi-co-appli foam 54 is heated and melted by the heating furnace 58.

  The multi-co-appli foam 54 is drawn to the multi-core fiber 60 at the lower end of the heating furnace 58, and the wire diameter of the multi-core fiber 60 is measured in a non-contact manner by the wire diameter measuring unit 62. The multi-core fiber 60 is coated with an ultraviolet (UV) curable epoxy resin by a coating device 64, and the coating is cured by an ultraviolet lamp 66.

  The multi-core fiber 60 coated with the UV curable epoxy resin is wound around a winding drum 70 via a capstan roller 68 that rotates at a controlled speed. The rotational speed of the capstan roller 68 is feedback-controlled by the wire diameter control unit 72 so that the wire diameter of the multi-core fiber 60 measured by the wire diameter measuring unit 62 is kept constant.

  By drawing the multi-copier form 54 having a good cross-sectional shape and alignment accuracy of the core portion 35 as shown in FIG. 12A by such a drawing device, the cores 76 and 78 as shown in the cross-sectional view of FIG. A multi-core fiber 60 having high roundness and good alignment accuracy can be manufactured.

  In FIG. 14, reference numeral 74 denotes a glass matrix formed by melting a quartz tube. A core 76 is embedded in the center of the glass matrix 74, and six cores 78 are embedded on substantially the same circumference. Yes. Furthermore, twelve dummy fibers 80 are embedded on the outer periphery of the core 78 on substantially the same circumference.

  In the above-described embodiment, the dummy fiber 48 is arranged on the outer periphery of the small diameter co-appli foam 34 as shown in FIG. If dummy fibers are arranged on the outermost periphery, a multi-core fiber having a larger number of cores can be manufactured using the advantages of the manufacturing method of the present invention.

It is a schematic block diagram of a co-appli form manufacturing apparatus. It is a figure explaining the manufacturing method of a thin diameter co-appli foam. It is a figure which shows the several small diameter co-appli form bundled. It is a figure which shows a mode that the end of the bundled small diameter co-appli foam is inserted into a dummy quartz tube. It is a figure which shows the step which heat-melts an overlap part. It is a figure which shows the step which extends | stretches and cuts one end part and carries out fusion fixing. It is a figure which shows the thin diameter co-appli foam bundle | flux by which both ends were fusion-fixed. It is a figure which shows the prior art example heated as it is, without inserting in a dummy quartz tube. It is a figure which shows the state which bundled the dummy fiber around the thin diameter co-appli foam, and was set as the composite fiber bundle. It is a figure which shows the step which inserts a composite fiber bundle into a quartz tube, heat-fuses, and integrates. It is the 11-11 line sectional view of FIG. It is an expanded cross-sectional photograph of the multico-appli foam manufactured by the method of the present invention and the conventional method. It is a figure which shows schematic structure of a drawing apparatus. It is a figure which shows the cross section of the multi-core fiber of this invention embodiment.

Explanation of symbols

28 Co-appli foam 34 Small-diameter co-appli foam 36 Co-appli foam bundle 42 Dummy quartz tube 46 Oxyhydrogen burner 48 Dummy fiber 50 Composite fiber bundle 52 Quartz tube 60 Multi-core fiber 74 Glass matrix 76, 78 Core 80 Dummy fiber

Claims (4)

(A) A co-appli foam is heated and stretched and cut into a predetermined length to produce a plurality of small-diameter co-appli foams,
(B) Bundle the plurality of small diameter co-appli foams;
(C) Insert one end of the bundled small diameter co-appli foam into the first quartz tube,
(D) Heat-melting the first quartz tube at a portion where the plurality of small-diameter co-appli foams are inserted, and extending and cutting the fine-coil foams, thereby Fusing one end,
(E) Steps (c) and (d) are repeated for the other ends of the bundled small diameter co-appli foams,
(F) inserting the plurality of small diameter co-appli foams fused at both ends into the second quartz tube;
(G) sequentially heating the second quartz tube from one end side to the other end side thereof and melting the second quartz tube together with the plurality of small-diameter co-appli foams; Multi-co-appli foam is produced by fusing and integrating small-diameter co-appli foam,
(H) melting and spinning the multi-co-appli foam;
A method of manufacturing a multi-core fiber, comprising each step. Before step (f)
(I) Bundling a plurality of dummy fibers at substantially equal intervals around the plurality of small diameter co-appli foams fused at both ends;
(J) Inserting one end of the bundled dummy fibers and the small diameter co-appli foam into the third quartz tube,
(K) Heat-melting the third quartz tube at a portion where the plurality of dummy fibers are inserted, and drawing and cutting the dummy fibers together with the plurality of small diameter co-preforms Is fused to the one end of the small diameter co-appli foam,
(L) The steps (j) and (k) are repeated for the other end portion of the small diameter co-apply foam in which the plurality of dummy fibers are bundled around the periphery.
The method of manufacturing a multi-core fiber according to claim 1, further comprising each step. A cylindrical glass matrix;
A plurality of cores fused and embedded at substantially the same interval in the center of the cylindrical glass matrix;
A plurality of dummy fibers arranged around the plurality of cores at substantially the same circumference and at the same interval, and fused and embedded in the cylindrical glass matrix;
A multi-core fiber characterized by comprising:   The plurality of cores include a first core disposed at the center of the cylindrical glass matrix and a plurality of second cores disposed at substantially the same circumference and at the same interval around the first core. The multi-core fiber according to claim 3, wherein

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