Fusion splicer and optical fiber connection method

Abstract

Three electrodes (7a, 7b, 7c) are disposed on the outer periphery of the hollow fiber (21) at substantially equal intervals (approximately 120 DEG) in the circumferential direction at a welding part where the front end parts of the optical fibers are butted and welded. When viewed from the axial direction of the hollow-core optical fiber (21), the center of the triangle at the tip of the connection electrodes (7a, 7b, 7c) substantially coincides with the center of the cross-section of the hollow-core optical fiber (21). The control unit is capable of applying a voltage between the electrodes of a predetermined combination for a predetermined time, and sequentially changing the combination of the electrodes for each time.

Description

TECHNICAL FIELD

[0001] The present application relates to a fusion splicer or the like, which can efficiently fuse even an optical fiber having a special cross-sectional shape such as a hollow core fiber or a photonic band gap fiber. BACKGROUND

[0002] A fusion splicer is used when connecting optical fibers to each other. The fusion splicer butts the optical fibers held by a pair of holders against each other and arranges them between electrodes, and fuses the leading ends of the optical fibers to each other by an electric arc, thereby connecting the optical fibers to each other.

[0003] In a fusion splicer for fusing general optical fibers to each other, a pair of electrodes is arranged, and the optical fibers are butted against each other and arranged between the pair of electrodes, an electric arc is generated between the electrodes, thereby enabling the optical fibers to be fused to each other. In contrast, in a large-diameter optical fiber, a multi-core optical fiber, or the like, for example, the optical fibers are sometimes not uniformly heated by the electric arc.

[0004] As a method of uniformly heating the optical fibers even in such a case, a method is proposed in which three electrodes are arranged equidistantly around the optical fibers, and an electric arc is generated between each of the electrodes, thereby forming a substantially equidistant heating region (for example, Patent Literature 1, Patent Literature 2).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2010-518449

[0008] Patent Literature 2: International Publication No. WO2012 / 099883 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In Patent Literatures 1 and 2, a three-phase high-frequency voltage is applied between the three electrodes, thereby generating an electric arc between each of the electrodes, and the optical fibers are arranged in a space surrounded by the electric arcs. The electric arcs generated between each of the electrodes vary depending on the phase difference of the voltage applied to each of the electrodes. That is, the combination of the electrodes in which the electric arc is generated varies.

[0011] However, according to Patent Literatures 1 and 2, since the voltage applied to the electrodes is a high-frequency voltage of, for example, 22 kHz, the generation time of the electric arc between each of the electrodes is approximately 15 μs or so, and the electric arc between the electrodes moves in a very short time. Therefore, at first glance, the electric arc is always generated between all of the electrodes, and according to Patent Literatures 1 and 2, the content is disclosed that a uniform heating region can be formed in a space surrounded by the three electrodes.

[0012] Thus, according to Patent Literatures 1 and 2, even if the diameter of the optical fiber arranged inside is thick, by arranging the optical fiber in the uniform heating region, the entire optical fiber can be heated and fused substantially uniformly.

[0013] On the other hand, in recent years, special optical fibers such as hollow core optical fibers and photonic band gap optical fibers have been developed. For example, a hollow core optical fiber is used to enclose light in an air tube, and has a fine internal structure in order to form the air tube. Thus, in a hollow core optical fiber, the outer peripheral portion has a thick wall of glass in order to ensure strength, and inside, thin glass partitions are formed in order to form a fine air layer.

[0014] If such an optical fiber is fused by a conventional method, the fine internal structure melts and disappears, becoming a factor of light leakage. However, if the heating temperature is excessively lowered, the outer peripheral portion does not melt sufficiently, the fusion strength decreases, and becomes a factor of the connection portion breaking.

[0015] Further, if fusion is performed using three electrodes as in the methods of Patent Literatures 1 and 2, even if the outer peripheral portion of the optical fiber is located on a straight line between the electrodes, as described above, a substantially uniform heating region is formed, and thus excessive fusion of the central portion cannot be prevented. Rather, compared to the case where fusion is performed using only one pair of electrodes, since the uniform heating region is enlarged, it is possible that the fusion of the central portion of the optical fiber surrounded by the three arcs continues to progress, and the fine air layer is destroyed.

[0016] The present application was made in view of such a problem, and aims to provide a fusion splicer or the like that can efficiently fuse even special optical fibers such as hollow core optical fibers and photonic band gap optical fibers.

[0017] Solution to the Problem

[0018] In order to achieve the above object, a first application is a fusion splicer that connects optical fibers to each other, characterized by comprising: three or more electrodes arranged at a fusion portion at which the leading end portions of the optical fibers are butted to be fused; and a control portion that controls the voltage applied to each of the electrodes, the control portion being capable of discharging between the electrodes of a predetermined combination for a predetermined time, and being capable of sequentially changing the combination of the electrodes that discharge for each time.

[0019] It is preferable that the control portion be capable of setting a discharge stop period in which discharging is stopped between all of the electrodes for a predetermined time, during a period from after discharging between the electrodes of a predetermined combination to before discharging between the electrodes of a next combination.

[0020] Four or more of the electrodes are arranged at predetermined intervals, and the control portion can sequentially apply voltage to a combination of all of the electrodes that are adjacent in the circumferential direction.

[0021] The control section can also apply voltage to a plurality of combinations of the electrodes simultaneously, and can discharge between two or more pairs of the electrodes simultaneously.

[0022] According to the first invention, when fusion splicing is performed using three or more electrodes, an arc is generated only at a predetermined time in a predetermined combination of the electrodes, and the combination of the electrodes is changed sequentially, so that the straight line connecting the electrodes can be heated preferentially. Therefore, the outer peripheral portion of the optical fiber can be heated selectively, and heating of the central portion of the optical fiber can be suppressed.

[0023] In addition, a predetermined time discharge stop period is set during the period from when voltage is applied to the electrodes of the predetermined combination to generate an arc until voltage is applied to the electrodes of the next combination to generate an arc, so that the central portion of the optical fiber can be prevented from being heated excessively.

[0024] In addition, four or more electrodes are used, and voltage is applied sequentially to combinations of all electrodes adjacent in the circumferential direction, so that an arc can be generated at a finer angle in the outer peripheral portion of the optical fiber compared to the case where three electrodes are used.

[0025] In addition, voltage is applied to a plurality of combinations of the electrodes simultaneously, and discharge is performed between two or more pairs of the electrodes simultaneously, so that the time for generating an arc around the entire optical fiber can be shortened.

[0026] The second invention is a method for connecting optical fibers, characterized by connecting optical fibers to each other using a fusion splicer that includes three or more electrodes disposed at a fusion splicing portion at which the leading end portions of the optical fibers are butted to be fused, and a control section that controls voltage applied to each of the electrodes, the control section being capable of discharging between the electrodes of a predetermined combination at a predetermined time, and sequentially changing the combination of the electrodes that discharge at each time to connect the optical fibers to each other.

[0027] The optical fibers can be hollow core optical fibers, or optical fibers formed of a core and a cladding portion around the core and having at least one hollow hole in the cladding portion, and the outer peripheral portions of the optical fibers are discharged to fuse the outer peripheral portions of the optical fibers to each other, and the inside of the optical fibers is not fused.

[0028] The optical fibers can be optical fibers formed of a core and a cladding portion around the core and having a plurality of cores, and the outer peripheral portions of the optical fibers are discharged to fuse the outer peripheral portions of the optical fibers at a temperature higher than the inside of the optical fibers.

[0029] According to the second application, when fusion is performed using three or more electrodes, an arc is generated only at a predetermined time in a predetermined combination of electrodes, and the combination of electrodes is sequentially changed, whereby the straight line connecting the electrodes to each other can be preferentially heated. Therefore, the outer peripheral portion of the optical fiber can be selectively heated, and heating of the central portion of the optical fiber can be suppressed.

[0030] Further, in the case of a hollow core optical fiber, a photonic band gap optical fiber, or the like having a hollow portion in the cladding portion, the outer peripheral portion is surely fused, whereby the connection strength is ensured, and the thin partition wall of the inner peripheral portion of the optical fiber is not fused or the amount of fusion is reduced, whereby the optical fibers can be fused to each other while maintaining the air layer.

[0031] Further, in the case of a multi-core optical fiber having a plurality of cores, the cores near the outer peripheral portion which are more easily affected by the core shift are sufficiently heated, whereby diffusion of the core dopant can be promoted. Therefore, the mode field diameter of the cores on the outer peripheral portion side can be enlarged, and the effect of the core shift can be suppressed.

[0032] Effects of Invention

[0033] According to the present application, a fusion splicer or the like can be provided, which can efficiently perform fusion even in the case of a special optical fiber such as a hollow core optical fiber or a photonic band gap optical fiber. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a perspective view showing a fusion splicer 1.

[0035] Figure 2A is a cross-sectional view of a hollow core optical fiber.

[0036] Figure 2B is a cross-sectional view of a photonic band gap optical fiber.

[0037] Figure 3A is a view showing a procedure at the time of fusion.

[0038] Figure 3B is a view showing a procedure at the time of fusion.

[0039] Figure 3C is a view showing a procedure at the time of fusion.

[0040] Figure 4A is a view showing a circuit at the time of fusion of Figure 3A .

[0041] Figure 4B is a view showing a circuit at the time of fusion of Figure 3B .

[0042] Figure 4C is a view showing a circuit at the time of fusion of Figure 3C .

[0043] Figure 5A is a conceptual diagram showing a discharge timing. Figures 3A-3C

[0044] Figure 5B is a conceptual diagram showing another discharge timing.

[0045] Figure 5C is a conceptual diagram showing another discharge timing.

[0046] Figure 6A is a conceptual diagram showing a discharge timing in a case where four electrodes are used.

[0047] Figure 6B is a conceptual diagram showing a discharge timing in a case where four electrodes are used.

[0048] Figure 6C is a conceptual diagram showing a discharge timing in a case where four electrodes are used.

[0049] Figure 7 is a sectional view of a multi-core optical fiber 31. DETAILED DESCRIPTION

[0050] Hereinafter, an embodiment of the present application will be described with reference to the drawings. Figure 1 is a perspective view showing a fusion splicer 1. The fusion splicer 1 is used for connecting a pair of optical fibers by fusion. Further, in the following drawings, illustration is omitted for structures which are not required in the explanation.

[0051] As shown in Figure 1 , the fusion splicer 1 has a lid portion 3 which can open and close the main body. In addition, the main body is provided with a holder placement portion 11 which places a holder which holds an optical fiber, an optical fiber holding portion 5 which holds the front end of the optical fiber to be positioned, an operation portion 15 which performs various settings of the fusion splicer 1, the following centering operation and fusion operation, and the like, and a display portion 17 or the like which displays various information and images. Further, the display portion 17 can be provided as a touch panel, thereby integrating the operation portion 15 and the display portion 17.

[0052] The optical fiber is held in a V groove of the optical fiber holding portion 5. In addition, three electrodes 7 are arranged in a direction which is substantially perpendicular to the facing direction of the pair of optical fibers. Further, the arrangement of the electrodes 7 will be described in detail later.

[0053] The lid portion 3 can open and close the main body. A clamping member 13 is provided on the back surface of the lid portion 3, and the front end of the clamping member 13 is positioned at a portion corresponding to the position of the optical fiber on the optical fiber holding portion 5 when the lid portion 3 is closed. That is, by the clamping member 13 provided on the back surface of the lid portion 3, a pair of optical fibers can be held in opposition in the optical fiber holding portion 5.

[0054] ​The optical fiber is held using a pair of holders, and the holders are placed on the holder placement portion 11. In this state, the lid portion 3 is closed, and an arc is generated between the electrodes 7 in a state in which the front ends of the optical fibers are butted against each other, so that the front end portions of the optical fibers can be fused and joined. Further, the fusion splicer 1 is effective for the connection of special optical fibers such as hollow core optical fibers and photonic band gap optical fibers.

[0055] Figure 2A is a schematic view of a cross section of a hollow core optical fiber 21. In the hollow core optical fiber 21, the glass thickness of an outer peripheral portion 21a is thick, and an air layer divided by a thin wall portion 21b is formed inside the outer peripheral portion 21a. That is, the hollow core optical fiber 21 is composed of the thick wall outer peripheral portion 21a and the thin wall portion 21b inside.

[0056] Figure 2B is a schematic view of a cross section of a photonic band gap optical fiber 22. The photonic band gap optical fiber 22, although the cross sectional shape is different from that of the hollow core optical fiber 21, also divides a space with a thin wall portion 22b inside an outer peripheral portion 22a (glass solid portion). Further, if an optical fiber is formed of a core and a cladding portion outside the core and has at least one hole in the cladding portion, even if it is not the photonic band gap optical fiber 22 as shown in the drawing, it can be applied to the present embodiment.

[0057] If it is intended to fuse the hollow core optical fiber 21 and the photonic band gap optical fiber 22 in the same manner as the usual optical fibers, it is necessary to fuse and join the outer peripheral portions 21a, 22a completely. In this case, if the outer peripheral portions 21a, 22a are fused, the thin wall portions 21b, 22b disappear, and become a factor of light leakage. On the other hand, if the heating temperature is lowered so as not to fuse the thin wall portions 21b, 22b inside, the outer peripheral portions 21a, 22a are not sufficiently fused, the fusion strength decreases, and becomes a factor of breakage of the connection portion.

[0058] Next, a method of connecting optical fibers to each other using the fusion splicer 1 of the present embodiment will be described. Figures 3A-3C is a view showing the positional relationship of the electrodes and the hollow core optical fiber 21, and is a view of a state in which an arc 23 is generated between the electrodes, Figures 4A-4C is a conceptual view of each circuit in Figures 3A-3C

[0059] As shown in Figures 3A-3C , in a fusion portion in which the front end portions of the optical fibers are butted against each other to be fused, three electrodes 7a, 7b, 7c (in addition, there is a case in which all of the electrodes 7a, 7b, 7c are collectively referred to as the electrodes 7) are arranged at substantially equal intervals (about 120°) in the circumferential direction at the outer periphery of the hollow core optical fiber 21. Further, in the following description, as the optical fibers to be fused, the hollow core optical fiber 21 is described, but the same applies to the photonic band gap optical fiber 22 and the like.

[0060] ​The center of the triangle connecting the front ends of the electrodes 7a, 7b, 7c substantially coincides with the center of the cross section of the hollow core optical fiber 21 when viewed in the axial direction of the hollow core optical fiber 21. In addition, each electrode is arranged in such a manner that a straight line connecting each of the electrodes 7a, 7b, 7c (a straight line connecting the front ends of each of the electrodes 7a, 7b, 7c) is positioned at the outer peripheral portion 21a of the hollow core optical fiber 21. That is, the straight line connecting each of the electrodes 7a, 7b, 7c and the center of the cross section of the hollow core optical fiber 21 are offset from each other.

[0061] As shown in Figures 4A-4C , each of the electrodes 7a, 7b, 7c is connected to a power source 29 which is a high-frequency high-voltage power source via a switch 27, and the switch 27 is controlled by a control section 25. That is, the control section 25 can control the voltage applied to each electrode by switching the switch 27.

[0062] For example, Figure 3A is a view showing a state in which an arc 23 is formed between the electrodes 7a, 7b, and in this case, the control section 25 can connect the power source 29 to the electrodes 7a, 7b by switching the switch 27. Thus, a voltage can be applied between the electrodes 7a, 7b, and the arc 23 can be generated.

[0063] Similarly, Figure 3B is a view showing a state in which an arc 23 is formed between the electrodes 7a, 7c, Figure 4B is a view showing a circuit diagram at this time. In this case, the control section 25 can switch the switch 27 to connect the power source 29 to the electrodes 7a, 7c, and thus a voltage can be applied between the electrodes 7a, 7c, and the arc 23 can be generated.

[0064] Similarly, Figure 3C is a view showing a state in which an arc 23 is formed between the electrodes 7b, 7c, Figure 4C is a view showing a circuit diagram at this time. In this case, the control section 25 can switch the switch 27 to connect the power source 29 to the electrodes 7b, 7c, and thus a voltage can be applied between the electrodes 7b, 7c, and the arc 23 can be generated.

[0065] In Figures 3A-3C , the portion where the arc 23 overlaps the hollow core optical fiber 21 becomes high temperature, and the temperature sharply decreases if it is away from this portion. Thus, in Figures 3A-3C , a portion of the outer peripheral portion 21a of the hollow core optical fiber 21 in the circumferential direction is locally heated, and heating of other portions is suppressed.

[0066] Figure 5Ais a conceptual diagram showing the timing of discharging. In the diagram, A-B, B-C, C-A show each combination of the electrodes of the electrodes 7a, 7b, 7c, and the horizontal axis shows time. Also, in the diagram, the shaded portion (X portion) shows a state in which a voltage is being applied between the electrodes and discharging is occurring (a state in which an arc 23 is being generated). The control section 25 can apply a voltage between the electrodes of a predetermined combination of electrodes at a predetermined time, and sequentially change the combination of electrodes for each time.

[0067] Furthermore, at first glance, Figure 5A The example shown is the same as in Patent Documents 1 and 2, but as described above, in Patent Documents 1 and 2, the position of the arc between the electrodes changes according to the phase difference formed by the high-frequency circuit, and thus the discharging time (the width of the X portion in the diagram) is several μs to several tens of μs. Thus, in Patent Documents 1 and 2, a substantially uniform heating region is formed.

[0068] On the other hand, in the present embodiment, discharging is maintained only between the electrodes thereof for a time set in the control section 25. For example, the control section 25 maintains discharging between the same electrodes for a time of about 0.1 to 1 second (for example, an amount of several thousand to several ten-thousand cycles of the high-frequency voltage), and switches the switch 27 to change the electrodes of discharging, and repeats these actions to perform fusion. That is, in the present embodiment, instead, only a portion of the circumference of the outer peripheral portion 21a of the hollow core optical fiber 21 is locally heated, and heating of the other outer peripheral portions 21a and the central portion is suppressed.

[0069] Thus, by daring to perform non-uniform heating, and always not performing heating of the central portion of the hollow core optical fiber 21, it is possible to suppress fusion of the thin-walled portion 21b inside, and to actually perform fusion only of the outer peripheral portion 21a to perform fusion.

[0070] Furthermore, in the above-described embodiment, the control section 25 switches the switch 27 on the circuit to control the voltage applied to each electrode, but is not limited thereto. For example, the control section 25 can be controlled to generate a phase difference in the sine wave voltage applied to each electrode, and to perform discharging only between predetermined electrodes. For example, a sine wave voltage with a phase difference of 180° can be applied between the electrodes of the discharging target, and a sine wave voltage with a phase difference of 90° can be applied to the other electrodes, and voltage control of the discharging electrodes can be performed only between the electrodes of the discharging target due to the phase difference exceeding the dielectric breakdown voltage of air. Thus, in the present application, control of the phase of the voltage of each electrode (the phase difference between each electrode) is also included in "control of the voltage". Thus, in the present application, if the control section 25 can control the voltage (including the phase difference) at a predetermined time, and perform discharging between each of the electrodes of a predetermined combination of electrodes, and sequentially change the combination of electrodes in which discharging is performed for each time, the control method is not particularly limited.

[0071] As described above, according to this embodiment, when the optical fibers to be connected are hollow-core fibers 21 and photonic bandgap fibers 22, localized heating of the peripheral portions 21a and 22a of the hollow-core fibers 21 and photonic bandgap fibers 22 can suppress melting of the thin-walled portions 21b and 22b at the center. In particular, since the entire circumference is not uniformly heated, the peripheral portions 21a and 22a on the unheated side are also cooled, thereby suppressing heat input to the center.

[0072] In this way, discharge is performed on a portion of the outer periphery of the hollow core fiber 21 and the photonic bandgap fiber 22, and the outer peripheries 21a and 22a are fused to each other, while the interiors of the hollow core fiber 21 and the photonic bandgap fiber 22 are not fused, so that the thin-walled portions 21b and 22b can be fused without melting.

[0073] In addition, the voltage control between each electrode by the control unit 25 is not limited to the above example. Figure 5B As shown, the control unit 25 may also set a discharge pause period (Y in the figure) between the application of voltage and discharge between a predetermined combination of electrodes and the application of voltage and discharge between the next combination of electrodes. This discharge pause period means that at a predetermined time, the application of voltage to all electrodes is stopped, or a phase difference is set so that discharge does not occur between all electrodes, thereby stopping discharge between all electrodes. Specifically, during the discharge pause period, no voltage is applied to any electrode, or the voltage between the electrodes is set below the dielectric breakdown voltage based on the phase difference between the voltages of all electrodes, thereby preventing discharge. This discharge pause period can particularly suppress temperature increases in the center of the optical fiber.

[0074] In addition, in the above embodiment, discharge is performed only at one location between a pair of electrodes, but the present invention is not limited thereto. Figure 5C As shown, the control unit 25 can also apply voltages simultaneously to multiple combinations of electrodes, and can also simultaneously discharge between two or more pairs of electrodes. For example, discharge can be performed at two locations between the three electrodes 7a, 7b, and 7c. In other words, discharge between at least some of all adjacent electrodes can be stopped. In this case, the combination of electrodes that discharge can be changed over time, and a discharge pause period can be provided between the discharge periods between the electrodes.

[0075] Furthermore, in the above-mentioned embodiment, an example using three electrodes has been described, but the present invention is not limited thereto. For example, four or more electrodes may be used. Figure 6Ais a view showing an example in which four electrodes are used. A-B ~ D-A show combinations of electrodes adjacent to each other in a circumferential direction when the four electrodes ABCD are arranged in the circumferential direction. In the case of using four electrodes, the electrodes are arranged at intervals of 90° around the optical fiber. In this way, even in the case of arranging four or more electrodes at predetermined intervals, the control section 25 can obtain the same effect by sequentially applying voltage to combinations of all electrodes adjacent to each other in the circumferential direction.

[0076] In this case, as shown in Figure 6B , a discharge stop period Y in which no voltage is applied to the electrodes can be provided between the periods X in which voltage is applied between the respective electrodes. In this case, as shown in Figure 6C , voltage can be applied between the electrodes of a plurality of combinations at the same time. In addition, in the example shown in Figure 6C , the electrodes between which discharge occurs at the same time are located opposite each other, but discharge can occur between adjacent electrodes at the same time.

[0077] In the above examples, as the optical fiber to be connected, examples suitable for the hollow core optical fiber 21 and the photonic bandgap optical fiber 22 are described, but the present application is not limited to these. Figure 7 is a cross-sectional view of a multi-core optical fiber 31. The multi-core optical fiber 31 is formed of a plurality of cores 33 and a cladding 35 covering the cores 33. In the example shown in the drawing, other cores 33 are arranged at equal intervals around the central core 33.

[0078] The multi-core optical fiber 31 is different from the hollow core optical fiber 21 and the photonic bandgap optical fiber 22 described above in that connection between the cores 33 cannot be performed without fusion of the central portion. On the other hand, in the case of centering the multi-core optical fibers 31 to each other, the central core 33 is not affected by the rotation centering, but since the cores 33 on the outer periphery are affected by the shift due to the rotation centering, the transmission loss is more likely to become large than the central core 33.

[0079] Therefore, by using the fusion splicer 1 for fusion splicing of the multi-core optical fiber 31, fusion to the center of the multi-core optical fiber 31 is performed, and thus the effect can be reduced. In order to fuse to the center of the multi-core optical fiber 31, for example, there are a method in which the size of a polygon formed by the tips of the electrodes 7 is made smaller, and a method in which the straight line connecting the tips of the electrodes is made closer to the center of the multi-core optical fiber 31 than in the case of the hollow core optical fiber 21 and the like, and a method in which the discharge time between the electrodes is made longer.

[0080] In this case, since the discharge is mainly performed on the outer peripheral portion of the multi-core optical fiber 31, the temperature distribution at the time of fusion of the outer peripheral portion of the multi-core optical fiber 31 is made higher than the temperature of the inside of the multi-core optical fiber 31, and fusion is performed. Therefore, the diffusion of the core dopant of the core 33 on the outer peripheral side can be promoted. As a result, the mode field diameter of the core 33 of the outer peripheral portion can be enlarged compared to the core 33 of the center, and the influence of the core shift of the core 33 on the outer peripheral side can be suppressed. Furthermore, if the optical fiber is formed of the core 33 and the cladding 35 on the outer periphery of the core 33 and has a plurality of cores 33, even if it is not the multi-core optical fiber 31 as shown in the drawing, it can be applied to the present embodiment.

[0081] Further, the control section 25 can adjust the interval between the electrodes, for example, in accordance with the type of the connected optical fiber, in addition to the control of the switch 27 and the voltage control of the power supply 29. In addition, the discharge time and the discharge stop time described above can be changed for each type of optical fiber.

[0082] In addition, the control section 25 can determine that the fusion is completed at the stage where the discharge of a predetermined time or a predetermined number of times is completed, or can determine the completion of the fusion based on predetermined information of the optical fiber. For example, the image of the fused portion, the leakage of the incident light can be detected, and the fusion can be completed when a predetermined condition is satisfied.

[0083] In addition, during the discharge, the optical fiber can be rotated with the center axis of the optical fiber as the rotation axis, or can be swung in a predetermined range of rotation angle with respect to the fixed direction of the arrangement of the electrodes.

[0084] The embodiments of the present application have been described above with reference to the accompanying drawings, but the technical scope of the present application is not limited to the above-described embodiments. It is clear that a variety of changes and modifications can be conceived by those skilled in the art within the scope of the technical idea recited in the claims, and they also belong to the technical scope of the present application.

[0085] Explanation of Reference Numerals:

[0086] 1: fusion splicer

[0087] 3: cover portion

[0088] 5: optical fiber holding portion

[0089] 7, 7a, 7b, 7c, 7d: electrode

[0090] 11: holder placement portion

[0091] 13: clamping member

[0092] 15: operation portion

[0093] 17: display portion

[0094] 21: Hollow core fiber

[0095] 21a: Outer peripheral portion

[0096] 21b: Thin-walled portion

[0097] 22: Photonic band gap fiber

[0098] 22a: Outer peripheral portion

[0099] 22b: Thin-walled portion

[0100] 23: Electric arc

[0101] 25: Control section

[0102] 27: Switch

[0103] 29: Power supply

[0104] 31: Multi-core fiber

[0105] 33: Core

[0106] 35: Cladding

Claims

1. A fusion splicer for connecting optical fibers, characterized in that: have: Three or more electrodes are arranged at a fusion splice where the distal ends of the optical fibers are butted and fused; and a control unit that controls the voltage applied to each of the electrodes, The control unit can cause discharge between a predetermined combination of the electrodes at a preset time, and can sequentially change the combination of the electrodes for discharge at each time.

2. The welding machine according to claim 1, characterized in that: The control unit may set a discharge stop period in which discharge is stopped between all the electrodes at a predetermined time after discharge is performed between the electrodes of a predetermined combination until discharge is performed between the electrodes of a next combination.

3. The welding machine according to claim 1, characterized in that: The four or more electrodes are arranged at predetermined intervals, and the control unit sequentially applies voltage to all combinations of the electrodes adjacent to each other in the circumferential direction.

4. The welding machine according to claim 1, characterized in that The control unit can simultaneously apply voltage to a plurality of combinations of the electrodes and simultaneously generate discharges between two or more pairs of the electrodes.

5. A method for connecting optical fibers, characterized in that: Use a fusion splicer to connect optical fibers to each other. The welding machine has: Three or more electrodes are arranged at a fusion splice where the distal ends of the optical fibers are butted and fused; and a control unit that controls the voltage applied to each of the electrodes, The control unit can cause discharge to occur between a predetermined combination of the electrodes at a preset time, and can sequentially change the combination of the electrodes for discharge at each time to connect the optical fibers.

6. The optical fiber connection method according to claim 5, characterized in that: The optical fiber is a hollow-core optical fiber, or an optical fiber formed by a core and a cladding portion around the core and having at least one empty hole in the cladding portion. Discharge is performed on the peripheral portion of the optical fiber to fuse the peripheral portions of the optical fiber to each other, and no fusion is performed inside the optical fiber.

7. The optical fiber connection method according to claim 5, characterized in that: The optical fiber is an optical fiber formed by a core and a cladding portion around the core and having multiple cores. Discharge is performed on the periphery of the optical fiber so that the temperature distribution of the periphery of the optical fiber during welding becomes higher than the temperature inside the optical fiber for welding.

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