JP4382724B2 - Optical fiber fusion splicing method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for fusion splicing between optical fibers or a fusion splicing between an optical waveguide and an optical fiber. The present invention is premised on a glass-based optical fiber and an optical waveguide.

  In fusion splicing between optical fibers or fusion splicing between an optical waveguide and an optical fiber, the quality of the connection characteristics depends on the amount of compression of the connecting portion in addition to the alignment of the optical axis to be connected. If the connection portion is fused in a state where the amount of compression is small, the outer diameter of the optical fiber becomes thin, and if the amount of compression is too large, the outer diameter of the optical fiber becomes thick. In any case, since the optical connection loss increases, it is necessary to control the compression amount with good timing at the moment when a minute compression amount of about 10 μm is fused. In the conventional fusion splicing apparatus, the amount of compression is controlled by a precise stage mechanism, which makes the apparatus large. In addition, when there is a margin in the length of the optical fiber, it is possible to connect the optical fiber to the fusion splicer. However, if there is no margin in the length of the optical fiber, When it is necessary to connect with the shortest possible length, it is impossible to connect pigtail optical fibers of a plurality of optical modules in a narrow space such as on an optical board.

European Patent Application Publication No. 1174740 Okumura Atsushi “Materials Mechanics” (enlarged version) Standard Mechanical Engineering Course 6 Corona P.104-107, P.300-301 M. Kobayashi et al., “Injection-molded single-mode multiple optical fiber connector using buckling force of bare fiber”, IEEE. J. Selected Topics in Quantum Electronics, Vol.5, No.5, pp.1271-1277, 1999.

  In order to solve the problems of the prior art as described above, the present invention has achieved the simplification of the setting of the compression amount of the connecting portion in the fusion splicing of the optical fiber, thereby realizing the downsizing of the apparatus and the simplification of the operation. An object is to provide a fusion splicing method and a fusion splicing device.

In order to achieve the above object, the fusion splicing method of the present invention is a process of aligning optical fibers or optical waveguides and optical fibers, and abutting optical fibers or optical waveguides and optical fibers. And in order to obtain a desired pressing force and compression amount at the abutted portion, a portion for gripping the optical fiber to maintain the buckled state of the optical fiber, and a aligning portion where the abutted portion is located Keeping the distance constant, push the optical fiber on one side to the opposite optical fiber or optical waveguide side so that the optical fiber is pushed toward the opposite optical fiber or optical waveguide. A step of holding the optical fiber in a buckled state, a step of fusing the butted portion by heating, and releasing the member that holds the optical fiber after fusing, thereby bending the optical fiber. Characterized by a step of the state.

In order to achieve the above object, the fusion splicing device of the present invention aligns optical fibers or optical waveguides and optical fibers, and aligns optical fibers or optical waveguides and optical fibers. A core member, and a portion for gripping the optical fiber in order to maintain a buckled state of the optical fiber in order to obtain a desired pressing force and compression amount at the abutted portion by mounting or integrating the aligning member ; The optical fiber on one side is opposed so as to press toward the optical fiber or optical waveguide facing each other while keeping the distance from the alignment part of the alignment member where the butted portion is located constant. The optical fiber is held in a buckled state outside the aligning member by being pushed into the optical fiber or optical waveguide, and after fusion, the optical fiber is released and the optical fiber is not bent. A holding member, characterized by comprising a heating means for fusing by heating the butted portion.

  With the above configuration, according to the present invention, the optical fibers are matched with each other, or the optical fiber and the optical waveguide are abutted, and one of the optical fibers is held buckled outside the alignment portion. Because the part is fused, the pressing force can be adjusted by determining the deflection length of the optical fiber, and the optimum pressing force can be obtained according to the fusion method (discharge, laser melting, etc.) Since a precise stage mechanism and control mechanism are unnecessary, the apparatus is simple and small.

  More specifically, in the present invention, the center of the optical fiber connection portion and the buckling member only need to be provided around the optical fiber connection portion. Can be set easily. As a result, according to the present invention, the apparatus can be easily reduced in size, and the connection work can be realized by shortening the extra length of the optical fiber in a narrow space such as on the optical board. Here, buckling refers to a phenomenon in which a beam such as an optical fiber bends in the lateral direction due to an axial load exceeding the limit, and if there is no plastic deformation, there is a spring effect. The pressing force of the connecting portion is determined by the length of bending of the optical fiber, and the compression amount of the connecting portion is determined by the amount of lateral deflection. In addition, since the amount of deflection becomes larger than the amount of minute compression, conversely, the amount of minute compression can be controlled only by roughly adjusting the amount of deflection. In the present invention, since the alignment member is used, the optical axis is not displaced even if the optical fiber is buckled in advance, so that it is not necessary to measure and compress the timing unlike the conventional fusion splicer. The degree of melting of the optical fiber is determined by the discharge intensity, the laser intensity, and the heating time, and the optimal pressing force is determined for this. This can also be easily set by determining the deflection length of the optical fiber. Therefore, according to the present invention, a precise stage mechanism and control mechanism are unnecessary, and only the alignment member and the holding member for holding buckling are required around the optical fiber connection portion, resulting in a simple and compact device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
The configuration of an optical fiber fusion splicing device according to an embodiment of the present invention is shown in the longitudinal sectional view of FIG. The microholes 12 arranged on the same axis penetrate the columns 13, 14, 15 of the connection jig 11 for aligning and holding the optical fiber 10 substantially horizontally. The microhole 12 is set to a size slightly thicker than the outer shape of the optical fiber 10 from which the coating is stripped for connection. Further, it is preferable that the microhole 12 has its corners chamfered or tapered to facilitate insertion of the optical fiber.

  Clamps (fasteners) 16 for fastening the optical fiber 10 to be taken in and out are attached to the pillars 13 and 15 at both ends. As the clamp 16, a known one using a screw, a spring or the like can be used.

  A space of about 2 mm is formed between the leftmost support column 13 and the intermediate support column 14, and the laser beam 33 (or arc discharge for heating) of the carbon dioxide laser 31 is opposed to the optical fiber 10 facing the space. The contact portion (butting portion) is irradiated and the contact portion is fusion-connected. Actually, the contact position of the optical fiber 10 is monitored by a microscope, but is omitted in this figure for the sake of simplicity. Although the mirror (reflecting mirror) 32 is disposed between the laser beams 33 of the carbon dioxide laser 31, the mirror 32 may be omitted depending on the arrangement of the carbon dioxide laser 31. In order to narrow down the beam shape, a beam expander (beam expander) and an objective lens are actually arranged on the optical axis of the carbon dioxide gas laser 31, but are omitted in the drawing for the sake of simplifying the drawing.

  A space for buckling the optical fiber 10 is provided between the middle support column 14 and the rightmost support column 15, and the length of the beam (the length between the micro holes 12) 22 is set to 20 mm, for example.

  Next, an optical fiber fusion splicing method according to an embodiment of the present invention will be described.

  First, two optical fibers 10 having ends cut by a fiber cutter are respectively inserted into the microholes 12 of the connection jig 11 from both directions, and the optical fibers 10 are opposed to each other. Subsequently, the right optical fiber 10 is fixed by the clamp 16 of the right end support column 15.

  Next, the left optical fiber 10 is pushed in, the right optical fiber 10 is deflected in the space between the middle support column 14 and the right end support column 15, and the opposing contact point of the optical fiber 10 is adjusted to the marking position. More specifically, the position where the arc discharge or the laser beam 33 is applied is marked on a microscope monitor (not shown) in advance, and the opposing contact point of the optical fibers 10 and 10 is determined by a predetermined compression amount 21 depending on the marking position. Adjust to the outside of 10 μm. Subsequently, the left optical fiber 10 is fixed by the clamp 16 of the left column 13. At this time, for example, a butt pressing of about 9 gf (gram weight) and a deflection 23 of about 280 μm are generated.

  On the contrary, the compression amount can be set by making use of this deflection amount. In this case, it is the same as described above until the optical fibers 10 having ends cut by the fiber cutter are inserted into the microholes 12 of the connection jig 11 and brought into contact with each other. As shown in FIG. 2, a piece 24 of a size that generates a deflection 23 of about 280 μm is prepared in advance, and this piece 24 is sandwiched between the center positions of the deflections 23. Next, the optical fiber 10 is moved so that the opposing contact point is aligned with the marking position. The optical fiber is fixed with clamps 16 on both sides. Next, by removing the piece 20, a butt pressing of about 9 gf and a compression amount of about 10 μm can be realized.

In this configuration, the pressing force at the time of fusion splicing is the buckling force P _b of the optical fiber 10. This buckling force P _b is calculated from Non-Patent Document 1 by the following equation.

Here, E is the elastic coefficient of the optical fiber 10 (7.6 GPa = 7.8 × 10 ³ kg / mm ² ), I is the second moment of section, d is the diameter of the optical fiber 10 (0.125 mm), and L is The length of the beam is 22. When L = 20 mm, P _b = 0.09N = 9 gf.

  Further, the relationship between the compression amount ΔL and the deflection amount δ is expressed by the following equation from Non-Patent Document 2.

Here, Elliptic is a complete elliptic integral of the second kind. When L = 20 mm and ΔL = 10 μm, δ = 280 μm. (By the way, when ΔL = 8 μm, δ = 250 μm (one optical fiber 250 μm core).)
Here, L = 20 mm and δ = 280 μm are set, but optimum values may be adopted in accordance with the optical fiber or the optical waveguide to be fusion-spliced.

  By heating the butt portion of the optical fiber 10 with an arc discharge or a laser beam, a good fusion splicing with an insertion loss of 0.1 dB or less could be realized. After the fusion, both clamps 16 are released so that the fiber 10 is not bent.

  The advantage of arc discharge is that, as shown in FIG. 3, two discharge electrodes 34 may be placed opposite to each other, so that the entire apparatus becomes small. However, since there is a limit to the distance between the electrodes, the number of cores is limited when a plurality of optical fibers are connected together.

  As the laser, a carbon dioxide laser has a wavelength of about 10 μm and absorbs glass well, which is optimal for heating. An advantage of the laser is that fusion splicing is possible only by irradiation from above. Therefore, by combining with a compression amount adjusting mechanism using buckling as in the present invention, even with a plurality of optical fibers, the connection surfaces are individually pressed, so irradiation is performed one by one and fusion is performed. There is no limit to the number of hearts. On the other hand, in the compression control by the stage as in the above-described prior art, since a plurality of fibers are moved together, it is necessary to melt the entire core at once, and thus the number of cores is limited. When a multi-core optical fiber is fused on the board using a laser, a method of irradiating the multi-core optical fiber sequentially by driving a mirror 32 and driving the mirror 32, and a board without shaking the laser light There is a method of moving the optical fiber itself and sequentially irradiating a multi-core optical fiber with laser light. The method of moving the board and irradiating each optical fiber of the multi-core optical fiber array can simplify the apparatus configuration and facilitate maintenance because it does not require a component for driving the laser system.

  When fusing with a laser, the laser beam may be shaken at a high speed over a plurality of cores and melted at once, or if one core at a time, it will be affected by the adjacent deflection state, but it will gradually melt. This may be repeated.

(Modification of the first embodiment)
Various forms can be applied to the alignment structure and the buckling holding structure that can be used in the optical fiber fusion splicing device of the present invention.

  As shown in FIGS. 4A, 4B, and 5, if the microhole 12 is a microhole array, multi-fiber optical fibers can be fused together as described above.

  As shown in FIG. 6, the support pillars 13, 14, and 15 may be divided at the center of the microhole 12 to sandwich the optical fiber 10.

  Further, as shown in FIG. 7, a V groove 121 may be used instead of the microhole 12. In this case, the V groove 121 may be formed only on one of the split molds, and a flat plate may be mounted on the V groove 121.

  As shown in FIG. 8, in the aligning member by the V groove 121, the flat plates 131 and 141 are mounted on only a part of the V groove 121 to form a microhole, and the portion of the V groove 121 on which the flat plates 131 and 141 are not mounted is formed. You may make it utilize as a guide (guide groove | channel) of an optical fiber. With this structure, it is possible to more easily insert the optical fiber into the microhole.

  As shown in FIGS. 9A and 9B, the coating 101 of the optical fiber 10 may be left up to the bent portion. In this state, the coating removal length is reduced, and the possibility of disconnection of the optical fiber is reduced.

  Further, as shown in FIGS. 10A and 10B, the tape fiber 102 can be bent.

  The optical fiber 10 has a fused portion in the space between the columns 13 and 14. After the fusion part is fused by heating with a laser or the like, a thermosetting resin is injected between the columns 13 and 14, and the resin is cured by irradiating a carbon dioxide laser, thereby protecting the fusion splicing part. It is also possible. The laser beam used when the thermosetting resin is cured has a lower intensity than that when the fused portion is irradiated. Alternatively, a UV (ultraviolet) curable resin can be injected to cure the resin with UV light. By filling the space between the columns 13 and 14 of FIGS. 5, 6, 7 and 8 with resin or the like, the components shown in FIGS. It can be a protective part.

  When the optical waveguide and the optical fiber are fusion-connected, as shown in FIG. 11, the optical waveguide 50 is mounted on the support column 13 except for the left optical fiber 10. In that case, the position of the alignment member such as the microhole 12 is aligned with the optical axis of the optical waveguide 50 in advance. In this state, for example, the optical fiber is passed through the aligning member, light is transmitted, the optical waveguide and the aligning member are fixed with an adhesive or the like at a position where the power is maximized, and then the optical fiber is pulled out. Can be realized.

(Other embodiments)
In the above, the preferred embodiment of the present invention has been described by way of example. However, the embodiment of the present invention is not limited to the above-described example, and the constituent members thereof are within the scope of the claims. Various modifications such as replacement, change, addition, increase / decrease in number, change in shape design, etc. are all included in the embodiments of the present invention.

It is a longitudinal section showing a schematic structure of an optical fiber fusion splicing device in one embodiment of the present invention. It is a longitudinal cross-sectional view which shows the piece which sets the amount of compression using the amount of deflection. It is a top view which shows the structure at the time of employ | adopting arc discharge as a heating source. It is a figure which shows the structure of the connection jig | tool for making a microhole into an array and carrying out multi-core lump fusion, (A) is a top view, (B) is a longitudinal cross-sectional view. It is a perspective view which shows the connection jig | tool for making a microhole into an array and carrying out multi-core lump fusion. It is a disassembled perspective view which shows the structure made into the mechanism which inserts a microhole and pinches | interposes an optical fiber. It is a disassembled perspective view which shows the structure using a V-groove instead of a microhole. It is a perspective view which shows the alignment jig | tool which makes a V groove a guide to a microhole. It is a figure which shows the state which left the coating | cover of the optical fiber to the bending part, (A) is a top view, (B) is a longitudinal cross-sectional view. It is a figure which shows the state bent with the tape fiber, (A) is a top view, (B) is a longitudinal cross-sectional view. It is a longitudinal cross-sectional view which shows the structural example of the fusion splicing of an optical waveguide and an optical fiber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical fiber 11 Connection jig 12 Micro hole 13-15 Support | pillar 16 Clamp 21 Compression amount 22 Beam length 22 Deflection 24 Frame 31 Carbon dioxide laser 32 Mirror 33 Laser beam 34 Arc discharge electrode 50 Optical waveguide 101 Optical fiber coating 102 Tape fiber 121 V groove 131, 141 Flat plate

Claims (6)

Aligning optical fibers or optical waveguides and optical fibers, and matching optical fibers or optical waveguides and optical fibers;
In order to obtain a desired pressing force and compression amount at the abutted portion, a distance between a position where the optical fiber is gripped in order to maintain a buckled state of the optical fiber and an alignment portion where the abutted portion is located is set. The optical fiber is seated on the outside of the alignment part by pushing the optical fiber on one side into the opposing optical fiber or optical waveguide side so that it is pressed toward the opposing optical fiber or optical waveguide while keeping it constant. Holding in a bent state; and
Fusing the butted portion by heating;
And a step of releasing the member that holds the optical fiber after being fused so that the optical fiber is not bent.   The fusion splicing method according to claim 1, wherein the step of fusing is a step of fusing the butted portion by heating by discharge.   2. The fusion splicing method according to claim 1, wherein the step of fusing is a step of fusing the butted portion by heating with a laser. An alignment member that aligns optical fibers, or optical waveguides and optical fibers, and abuts optical fibers or optical waveguides and optical fibers;
In order to obtain a desired pressing force and compression amount at the abutted portion by mounting or integrating the aligning member, a position where the optical fiber is gripped in order to maintain a buckled state of the optical fiber, and the abutted portion The optical fiber on one side is opposed to the optical fiber or optical waveguide so that the optical fiber or optical waveguide is pressed against the optical fiber or optical waveguide while keeping the distance from the alignment portion of the alignment member where the portion is located constant. Holding the optical fiber in a buckled state outside the aligning portion by pushing into the waveguide side, and after fusing, holding the optical fiber and releasing the optical fiber so that there is no deflection,
A fusion splicing device comprising heating means for fusing the butted portion by heating.   The fusion splicing device according to claim 4, wherein the heating means is a discharge heating device for fusing the butted portion by heating by discharge.   5. The fusion splicing device according to claim 4, wherein the heating means is a laser heating device for fusing the butted portion by heating with a laser.

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