Fusion machine

Abstract

Optical fibers 3 have end faces 5 that are cut not perpendicularly but obliquely relative to the axial direction of the optical fibers 3, so that the distance between the end faces 5 facing each other varies in the circumferential direction of the optical fibers 3. First, a circumferential position (part A) having the shortest distance between the tip parts of the optical fibers 3 is specified. Next, a control unit continuously applies a voltage between a set predetermined set of electrodes 7a and 7b for a predetermined time (first discharge step). In this state, the optical fibers 3 are moved in the direction in which the optical fibers abut against each other. In this state, the control unit applies a voltage between the adjacent electrodes 7a, 7b, and 7c, and sequentially changes the combination of the electrodes at predetermined time intervals (second discharge step).

Description

Fusion splicer

[0001] The present invention relates to a fusion splicer that can efficiently fusion splice optical fibers even when the cut surfaces are not perpendicular to each other.

[0002] A fusion splicer is used to connect optical fibers together. The fusion splicer places optical fibers held in a pair of holders, butts them together, between electrodes, and fuses the tips of the optical fibers together using an arc, thereby connecting the optical fibers together.

[0003] A fusion splicer typically used to fuse optical fibers together has a pair of electrodes. The optical fibers are placed face-to-face between the electrodes, and an arc is generated between the electrodes to fuse the optical fibers together.

[0004] In such cases, a method has been proposed for uniformly heating an optical fiber, in which three electrodes are evenly arranged around the circumference of the optical fiber and an arc is generated between each electrode, thereby forming a substantially uniform heating zone (e.g., Patent Documents 1 and 2).

[0005] JP 2010-518449 A International Publication WO2012 / 099883

[0006] Before fusion splicing, optical fibers are cut with a specified cutting machine, and when splicing the optical fibers, the end faces of the optical fibers are placed opposite each other. However, when cutting the optical fibers, the cut may not be perpendicular to the axial direction of the optical fiber. In other words, the end face of the optical fiber may not be perpendicular to the axial direction.

[0007] 6A is a diagram showing a state in which optical fibers 101 whose end faces 103 have been cut obliquely relative to the axial direction are arranged opposite each other. For example, in the example shown, the portions of the end faces 103 that protrude most toward the tip end are arranged opposite each other. When fusion splicing, first, either one of the left or right optical fibers 101 is advanced (arrow T in the figure) so that the tips of the optical fibers are butted together.

[0008] 6B is a diagram showing a state in which a voltage is applied between the electrodes 105 from this state. As shown in the figure, when an arc 109 is generated between the electrodes 105, a part of the tip portion of the optical fiber 101 becomes a fused portion 107. At this time, the fused portion 107 is formed in a predetermined range including the butted portion.

[0009] In this state, the optical fibers 101 are further advanced so as to butt against each other (arrow T in the figure) to perform fusion, and as shown in Figure 6C, the fused portions 107 in adjacent areas are integrated from the initial stage, but on the opposite side, the optical fibers 101 are farther apart, so a gap is formed between the fused portions 107. When a gap is formed in this way, the fused portions 107 are drawn into the gap by surface tension (arrow U in the figure).

[0010] When the molten portion 107 flows in one direction, the positional accuracy of the core of the optical fiber 101 deteriorates, which causes an increase in the splice loss between the optical fibers 101.

[0011] 7A shows the same arrangement as in Fig. 6A, but in this case, if the shortest distance between the optical fibers 101 is V1 and the longest distance is V2, the difference between V1 and V2 is the largest in the illustrated state. As described above, when the difference in the distance between the optical fibers 101 in the circumferential direction of the optical fibers 101 becomes large, the above-mentioned problems are likely to occur.

[0012] Therefore, in a fusion splicer capable of rotational alignment, there is a method of rotating the optical fiber 101 (indicated by the arrow W in the figure) to reduce the difference in distance in the circumferential direction of the optical fiber 101, as shown in Figure 7B. Figure 7C is a diagram showing a state in which the most protruding portion of one optical fiber 101 and the most protruding portion of the other optical fiber 101 are arranged on opposite sides. In this way, the difference between the distances V3 and V4 between the optical fibers 101 is reduced, making it possible to prevent the above-mentioned problem from occurring.

[0013] However, not all fusion splicers are equipped with a built-in rotation device, and the angles of the end faces 103 of the optical fibers 101 arranged opposite each other do not always match perfectly. For this reason, it is difficult to completely eliminate the difference in distance between the optical fibers 101 in the circumferential direction.

[0014] Furthermore, even if the end faces 103 are parallel to each other and the distance can be made constant, the center position between the end faces 103 varies depending on the location, so when the opposing parts of the optical fiber 101 are placed between the electrodes, the straight line connecting the tips of the electrodes and the midpoint of the end face 103 of the optical fiber 101 may be misaligned, making it difficult to achieve uniform melting.

[0015] Furthermore, even if a rotation device is built in, depending on the type of optical fiber, it may not be possible to rotate the optical fiber to an angle that minimizes the relative angle between the cut surfaces of the left and right fibers. For example, when fusion splicing polarization-maintaining fibers, multicore fibers, hollow-core fibers, etc., aligning the rotation plane takes priority over reducing the cut angle in order to achieve low connection loss. For this reason, it is difficult to completely eliminate the distance difference in the circumferential direction of the optical fiber 101.

[0016] In particular, hollow-core fibers must be fused without destroying their delicate internal structures, so it is almost impossible to melt the cut end faces. Figure 8A is a diagram showing two hollow-core optical fibers 101 arranged opposite each other. As mentioned above, when fusion splicing, the tips of the optical fibers 101 are first butted together, as shown in Figure 8B.

[0017] 8C, an arc 109 is generated between the electrodes 105. However, since only a small portion of the end face needs to be melted, there is a risk that the fiber may bend at the splice point when the fibers are butted together and pushed in. Such bending can lead to increased optical loss.

[0018] The present invention has been made in view of such problems, and aims to provide a fusion splicer that can efficiently fusion splice optical fibers even when the cut surfaces are not perpendicular to each other.

[0019] In order to achieve the above-mentioned object, the present invention provides a fusion splicer for connecting optical fibers, which comprises three or more electrodes arranged at a fusion section where the tips of the optical fibers are butted together and fused, and a control unit that controls the voltage applied to each of the electrodes, and which is characterized in that the control unit is capable of performing a first discharge process in which a voltage is applied continuously between a predetermined pair of the electrodes for a predetermined period of time, and a second discharge process in which a voltage is applied between adjacent electrodes and the electrode combination is sequentially changed every predetermined period of time.

[0020] It is desirable that the device has an imaging unit capable of imaging the tip ends of a pair of optical fibers that are arranged opposite each other and are to be fusion spliced, and that the control unit identifies, from the image of the tip ends of the optical fibers that has been imaged, the circumferential position at which the distance between the edges of the end faces of the optical fibers that are arranged opposite each other is closest, and in the first discharge step, applies a voltage between the pair of electrodes that sandwich that position.

[0021] The optical fiber rotating unit may have an optical fiber rotating unit capable of rotating at least one of a pair of optical fibers to be fusion spliced, which are arranged opposite each other, around the central axis of the optical fiber as the rotation axis, and the control unit may identify, from an image of the tip of the optical fiber that has been captured, the circumferential position at which the distance between the edges of the end faces of the optical fibers arranged opposite each other is closest, and use the optical fiber rotating unit to position this position approximately in the center of a pair of adjacent electrodes, and in the first discharge process, apply a voltage between the pair of electrodes that sandwich this position.

[0022] The control unit may be capable of determining, from the captured image of the tip of the optical fiber, the difference between the distance between the optical fibers at the closest point between the edges of the end faces of the optical fibers arranged opposite each other and the distance between the optical fibers at the farthest point between the edges of the end faces of the optical fibers, and setting the time of the first discharge process based on the determined difference in distance.

[0023] According to the present invention, by using three or more electrodes and applying a voltage continuously for a predetermined time between a predetermined pair of electrodes in a first discharge process, it is possible to selectively melt the portions where the end faces are close to each other. Furthermore, after the melted portions in the first discharge process are butted together, a second discharge process is performed in which the electrode combination is changed sequentially every predetermined time to fuse the optical fibers together. Therefore, before the second discharge starts (when the melted portions in the adjacent portions come into contact with each other), melting near the core is suppressed, and movement near the core can be suppressed.

[0024] Furthermore, during the second discharge process, the distance between the optical fibers at their furthest points can be reduced, thereby suppressing the formation of the gaps described above or shortening the time during which the gaps are formed, thereby suppressing the movement of the cores.

[0025] Furthermore, by identifying the location where the optical fibers are closest to each other in the imaging unit and performing the first discharge process on that location, the worker does not need to perform tasks such as measuring the distance between the end faces of the optical fibers or setting up electrodes to perform the first discharge process.

[0026] Furthermore, when the first discharge step is performed, by placing the closest part of the optical fiber at approximately the center of the electrode, it is possible to melt the closest part preferentially and efficiently.

[0027] Furthermore, by adjusting the discharge time of the first discharge step based on the difference between the shortest distance and the longest distance between the optical fibers, the second discharge step can be performed at an appropriate timing.

[0028] According to the present invention, it is possible to provide a fusion splicer that can efficiently fusion splice optical fibers even when the cut surfaces are not perpendicular to each other.

[0029] 1 is a diagram showing the configuration of a fusion splicer 1. FIG. 1 is a conceptual side view showing the process of fusing optical fibers 3 together. FIG. 2 is a conceptual side view showing the process of fusing optical fibers 3 together. FIG. 3 is a conceptual side view showing the process of fusing optical fibers 3 together. FIG. 4 is a conceptual side view showing the process of fusing optical fibers 3 together. FIG. 5 is a conceptual front view showing the process of fusing optical fibers 3 together. FIG. 6 is a conceptual front view showing the process of fusing optical fibers 3 together. FIG. 7 is a diagram showing the configuration of a fusion splicer 1a. FIG. 8 is a diagram showing the process of rotating optical fibers 3. FIG. 9 is a diagram showing the process of rotating optical fibers 3. FIG. 10 is a conceptual view showing a conventional process of fusing optical fibers 101 together. FIG. 11 is a conceptual view showing a conventional process of fusing optical fibers 101 together. FIG. 12 is a conceptual view showing a conventional process of fusing optical fibers 101 together. FIG. 13 is a conceptual view showing a conventional process of rotating one of optical fibers 101 when fusing optical fibers 101 together. 1 is a conceptual diagram showing a process of fusing together conventional optical fibers 101. 2 is a conceptual diagram showing a process of fusing together conventional optical fibers 101. 3 is a conceptual diagram showing a process of fusing together conventional optical fibers 101.

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing the configuration of a fusion splicer 1. The fusion splicer 1 connects a pair of optical fibers by fusion. In the following description, components that are not necessary for explaining the invention will be omitted.

[0031] The fusion splicer 1 includes a first imaging unit 11 and a second imaging unit 12 capable of capturing images of the tips of the optical fibers, a proximity portion identifying unit 13 that identifies proximity portions of the optical fibers from the images captured by the first imaging unit 11 and the second imaging unit 12, and a control unit 10 that performs various controls of the fusion splicer 1. As will be described in detail later, the fusion splicer 1 has at least three electrodes arranged in a fusion portion where the tips of the optical fibers are butted together and fused. The control unit 10 can, for example, control the voltage applied to each electrode to cause discharge between predetermined electrodes.

[0032] The first and second image capturing units 11 and 12 can capture images of the vicinity of the tips of a pair of optical fibers to be fusion spliced, which are arranged opposite each other, from different directions, for example, from the sides of the optical fibers. Therefore, the first and second image capturing units 11 and 12 can grasp the XY position of the tips of the optical fibers and perform alignment.

[0033] The adjacent portion specifying unit 13 specifies the portion (adjacent portion) where the distance between optical fibers is shortest in the circumferential direction (360° direction) of the optical fiber 3, based on the images captured by the first imaging unit 11 and the second imaging unit 12. Information about the specified adjacent portion is sent to the control unit 10, and control described below is performed.

[0034] Next, a method for fusion splicing optical fibers using the fusion splicer 1 will be described. Fig. 2A is a schematic side view showing a state in which the end faces 5 of a pair of optical fibers 3 are arranged facing each other, and Fig. 3A is a conceptual view seen from the axial direction of one of the optical fibers 3. As shown in Fig. 2A, the end faces 5 are cut obliquely rather than perpendicularly with respect to the axial direction of the optical fibers 3, and the distance between the opposing end faces 5 in the circumferential direction of the optical fibers 3 is different. Here, the circumferential position where the distance between the edge portions of the tips of the optical fibers 3 is closest is designated as part A (Figs. 2A and 3A).

[0035] 3A, in this embodiment, three electrodes 7a, 7b, and 7c are arranged evenly in the circumferential direction of the optical fiber 3. The optical fiber 3 is arranged approximately at the center of a triangle connecting the tips of the electrodes 7a, 7b, and 7c. In other words, the center position of the optical fiber 3 is shifted from the line connecting the tips of a predetermined pair of adjacent electrodes.

[0036] First, the control unit 10 uses the first imaging unit 11 and the second imaging unit 12 to capture images of the tip ends of the optical fibers 3 arranged opposite to each other, and then, from the captured images of the tip ends of the optical fibers 3, the adjacent portion specifying unit 13 identifies the circumferential position (portion A) at which the distance between the edges of the end faces of the optical fibers 3 arranged opposite to each other is closest. In other words, the control unit 10 identifies the portion that will first come into contact when the optical fibers 3 are butted together. Next, the control unit 10 sets a pair of electrodes that will sandwich portion A. In the example shown in FIG. 3A , portion A is located between electrodes 7 a and 7 b, so the control unit 10 sets electrodes 7 a and 7 b as the electrodes that will first discharge.

[0037] The distance between the optical fibers 3 in part A before discharge is, for example, about 50 μm. Therefore, after identifying part A, the control unit 10 may move the optical fibers 3 in the axial direction to adjust the distance between the optical fibers 3 in this region.

[0038] 2B and 3B, the control unit 10 applies a voltage continuously between a predetermined set of electrodes 7a and 7b for a predetermined time (first discharge step). That is, in the first discharge step, a voltage is applied only between the pair of electrodes 7a and 7b that sandwich the portion A.

[0039] When a voltage is applied between the electrodes 7a and 7b, an arc 9 is generated between the electrodes 7a and 7b, and the arc turns a part of the tip of the optical fiber 3 into a molten portion 8. As described above, since the center of the optical fiber 3 is offset from the line connecting the tips of a pair of adjacent electrodes, the molten portion 8 is formed only in a part of the circumferential direction of the optical fiber 3, including portion A.

[0040] In this state, as shown in Fig. 2C, the optical fibers 3 are moved in a direction in which they are butted together (in the direction of arrow B in the figure). When the optical fibers 3 are butted together, the fused portions 8 of the optical fibers 3 are integrated and butted together. That is, in the state of Fig. 2A, the distance between the optical fibers 3 can be shortened to a distance at which they cannot be brought closer together due to interference between the end faces 5. Furthermore, in this state, only a portion of the optical fiber 3 is melted, and therefore the center portion of the optical fiber 3, including the core, is not completely melted.

[0041] The amount of pushing after the first discharge step is set to be slightly larger than the gap before discharge. For example, if the gap between the optical fibers 3 at part A before discharge is 50 μm, the amount of pushing is set to be approximately 60 to 70 μm.

[0042] 2D and 3C, the control unit 10 applies a voltage between adjacent electrodes 7a, 7b, and 7c, sequentially changing the electrode combination at predetermined intervals (second discharge step). That is, in the second discharge step, arcs 9 are sequentially generated between the three electrodes 7a, 7b, and 7c in an extremely short time (shorter than the time it took for discharge to occur between the electrodes 7a and 7b in the first discharge step), thereby forming a substantially uniform heating zone in the area surrounded by the tips of the electrodes 7a, 7b, and 7c. As a result, the entire tips of the optical fibers 3 are melted, and the entire optical fibers 3 are fusion-spliced ​​by butting together.

[0043] In the second discharge step, the position of the arc between the electrodes can be changed by using a phase difference formed by a high-frequency circuit, as in Patent Documents 1 and 2. For example, the discharge time between each electrode is several microseconds to several tens of microseconds. This allows a substantially uniform heating zone to be formed between the electrodes.

[0044] On the other hand, in the first discharge step, discharge is maintained between the electrodes for a time period preset in the control unit 10. For example, the control unit 10 maintains discharge between the same electrodes for a time period of about 0.1 to 1 second (e.g., several thousand to several tens of thousands of cycles of the high-frequency voltage). Therefore, the first discharge step and the second discharge step are different steps.

[0045] As described above, according to the present embodiment, when the second discharge step is performed, the distance between the end faces of the optical fibers 3 is short, thereby narrowing the gap between the optical fibers 3. Therefore, the time from when the central portions of the optical fibers 3, including the cores, melt to when the optical fibers are butted together and fused together as a whole, is also short. As a result, compared to the conventional method, it is possible to suppress the flow of the optical fibers near the central portions of the optical fibers 3, including the cores, toward the gap.

[0046] Furthermore, as mentioned above, especially when connecting hollow-core fibers, the adjacent portions are partially melted beforehand and then butted together, which prevents bending of the connection portion when the optical fibers are pushed together.

[0047] Next, a second embodiment will be described. Fig. 4 is a diagram showing the configuration of a fusion splicer 1a. In the following description, components that exhibit the same effects as those in the first embodiment will be assigned the same reference numerals as those in Figs. 1 to 3C, and duplicated descriptions will be omitted.

[0048] The fusion splicer 1a has a configuration substantially similar to that of the fusion splicer 1, but differs in that it includes an optical fiber rotator 14. The optical fiber rotator 14 can rotate a holder that holds the optical fibers 3 around the central axis of the optical fibers 3 as the rotation axis. In other words, the optical fiber rotator 14 can rotate the optical fibers 3 to be fused, which are arranged opposite each other, in the circumferential direction.

[0049] Fig. 5A is a conceptual diagram showing a state as viewed from the axial direction of the optical fiber 3. As described above, part A in the figure is the part where the distance between the end faces 5 of the opposing optical fibers 3 is the shortest. In the example shown in Fig. 5A, part A is located in a part sandwiched between electrodes 7a and 7b, but is positioned at a position shifted from the center position of the electrodes 7a and 7b.

[0050] 5B, the control unit 10 identifies the circumferential position of portion A from the captured image of the tip end of the optical fiber 3, and operates the optical fiber rotator 14 to rotate the optical fiber 3 so that portion A is located approximately in the center of the pair of adjacent electrodes 7 a, 7 b (in the direction of arrow C in the figure). That is, the control unit 10 identifies the circumferential position A at which the distance between the tip ends of the optical fiber 3 is closest from the captured image of the tip end of the optical fiber 3, and can use the optical fiber rotator 14 to locate portion A approximately in the center of the pair of adjacent electrodes 7 a, 7 b.

[0051] In this manner, with portion A positioned approximately in the center of the electrodes 7a, 7b, the fusion splicing of the optical fiber 3 is performed in the same manner as in the first embodiment. By doing so, portion A is positioned approximately in the center of the electrodes 7a, 7b where it can be melted most efficiently, and therefore the vicinity of portion A can be melted efficiently.

[0052] According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment. Furthermore, since the portion A, where the distance between the end faces of the optical fibers 3 is the shortest, is disposed approximately in the center of the adjacent electrodes, it is possible to melt the portion A efficiently.

[0053] In this embodiment, the adjacent portion specifying unit 13 specifies portion A in the initial installation state, and then both optical fibers 3 are rotated, but this is not limited to this. For example, at least one of the optical fibers 3 may be rotated. Alternatively, the first imaging unit 11 and the second imaging unit may specify the shape (slope) of the end face 5 of each of the optical fibers 3 arranged opposite each other, and the optical fibers 3 may be rotated to specify portion A so that the positions of the end faces that protrude most toward the tip end face each other.

[0054] In the above-described embodiment, the control unit 10 identifies the area A based on the images captured by the first imaging unit 11 and the second imaging unit 12. However, the user may identify the area A from the images and manually set the electrodes to be subjected to the first discharging step. That is, the first discharging step may be automatically set by the control unit 10 or manually set by the user.

[0055] In addition, the control unit 10 may determine, from the captured image of the tip of the optical fiber 3, the difference between the distance between the optical fibers 3 at the closest point between the edges of the end faces of the optical fibers 3 arranged opposite each other and the distance between the optical fibers 3 at the farthest point between the edges of the end faces of the optical fibers 3, and set the time of the first discharge process, etc. based on the determined difference in distance.

[0056] For example, depending on the difference between the distance at portion A and the maximum distance (e.g., on the opposite side of portion A by 180°), the first discharge step time may be shortened when the difference in distance is small, and may be lengthened when the difference in distance is large. Also, depending on the difference between the distance at portion A and the maximum distance (e.g., on the opposite side of portion A by 180°), the pushing amount of the optical fiber 3 may be reduced when the difference in distance is small, and may be increased when the difference in distance is large.

[0057] The number of electrodes may be three or more, for example, four. Even in this case, in the first discharge step, discharge is performed between a pair of adjacent electrodes for a predetermined time, and then, in the second discharge step, the discharge electrodes are sequentially changed.

[0058] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical scope of the present invention is not limited to the above-described embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention.

[0059] DESCRIPTION OF SYMBOLS 1, 1a... Fusion splicer 3... Optical fiber 5... End face 7a, 7b, 7c... Electrode 8... Melted portion 9... Arc 10... Control unit 11... First imaging unit 12... Second imaging unit 13... Proximal portion identification unit 14... Optical fiber rotation unit 101... Optical fiber 103... End face 105... Electrode 107... Melted portion 109... Arc

Claims

1. A fusion splicer for connecting optical fibers, comprising: three or more electrodes arranged in a fusion section where the tips of the optical fibers are butted together and fused; and a control unit that controls the voltage applied to each of the electrodes, wherein the control unit is capable of performing a first discharge process in which a voltage is applied continuously between a predetermined pair of the electrodes for a predetermined period of time; and a second discharge process in which a voltage is applied between adjacent electrodes and the electrode combination is changed sequentially every predetermined period of time.

2. A fusion splicer according to claim 1, characterized in that it has an imaging unit capable of imaging the tip ends of a pair of optical fibers that are arranged opposite each other and are to be fusion spliced, and the control unit identifies, from the image of the tip ends of the optical fibers that has been captured, the circumferential position at which the distance between the edges of the end faces of the optical fibers that are arranged opposite each other is closest, and in the first discharge process, applies a voltage between the pair of electrodes that sandwich that position.

3. A fusion splicer according to claim 2, further comprising an optical fiber rotation unit capable of rotating at least one of a pair of optical fibers to be fusion spliced, arranged opposite to each other, around the central axis of the optical fiber as the rotation axis, wherein the control unit identifies, from an image of the tip end of the optical fiber that has been captured, the circumferential position at which the distance between the edges of the end faces of the optical fibers arranged opposite to each other is closest, and uses the optical fiber rotation unit to position this position approximately in the center of a pair of adjacent electrodes, and in the first discharge process, applies a voltage between the pair of electrodes that sandwich this position.

4. The fusion splicer according to claim 2, characterized in that the control unit is capable of identifying, from the captured image of the tip end of the optical fiber, the difference between the distance between the optical fibers at the closest point between the edges of the end faces of the optical fibers and the distance between the optical fibers at the farthest point between the edges of the end faces of the optical fibers, and setting the time for the first discharge process based on the identified difference in distance.

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