Optical fiber fusion splicer and optical fiber fusion splicing method

Abstract

To provide an optical fiber fusion splicer which allows for fusion splicing optical fibers under fusion conditions in accordance with a fiber pitch.SOLUTION: An optical fiber fusion splicer 10 of the present invention comprises a replaceable groove forming unit 13, an illumination unit 16, a lens 17, a camera 18, a pair of discharge electrodes 15, a high voltage generation circuit 24, a movable stage 11, an image processing unit 21, and a fusion condition processing unit 22.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an optical fiber fusion splicer and a method for fusion splicing optical fibers. [Background technology]

[0002] Patent Documents 1 and 2 disclose an optical fiber fusion splicer that uses electrical discharge heating to fusion-splice the ends of a plurality of single-core optical fibers (multi-core optical fibers) constituting one fiber group with the ends of a plurality of single-core optical fibers (multi-core optical fibers) constituting another fiber group so that the ends of a pair of opposing single-core optical fibers are connected to each other. For this optical fiber fusion splicer, a method is disclosed in which the fusion conditions (for example, the magnitude of voltage or current) are changed depending on the number of single-core optical fibers. Patent Document 3 also discloses an optical fiber fusion splicing method in which the fusion conditions are changed depending on the diameter of the single-core optical fibers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-287139 [Patent Document 2] Japanese Patent Application Publication No. 5-119226 [Patent Document 3] Patent No. 4429540 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the multi-core optical fibers that have been widely used up until now, there are only a few types of multi-core optical fibers, and there are also only a few types of distances between the centers of adjacent single-core optical fibers (hereinafter referred to as fiber pitch). In recent years, multi-core optical fibers with various specifications have come into use, and the number of fiber pitches has also increased. For example, multi-core optical fibers with multiple different fiber pitches are now in use, rather than all having the same fiber pitch.

[0005] However, the optical fiber fusion splicers and fusion splicing methods of Patent Documents 1 to 3 have the problem that, because the fusion conditions are set based only on the number and diameter of the single optical fibers, it may not be possible to fusion-splice a pair of multi-core optical fibers under appropriate fusion conditions. If the fusion conditions are not appropriate, the splicing loss in the fusion-spliced ​​multi-core optical fibers will be large.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an optical fiber fusion splicer and an optical fiber fusion splicing method that are capable of fusion splicing optical fibers under fusion conditions that correspond to the fiber pitch. [Means for solving the problem]

[0007] An optical fiber fusion splicer according to a first aspect of the present invention includes a replaceable groove forming unit having a plurality of first positioning grooves for equally spacedly arranging a plurality of first single-core optical fibers, each having a plurality of first glass portions, that constitute a first multi-core optical fiber, and a plurality of second positioning grooves for equally spacedly arranging a plurality of second single-core optical fibers, each having a plurality of second glass portions, an illumination unit for irradiating light onto the plurality of first single-core optical fibers and the plurality of second single-core optical fibers that are arranged in the groove forming unit, a lens for focusing the light that passes through the plurality of first glass portions, peripheral areas of the plurality of first glass portions, the plurality of second glass portions, and peripheral areas of the plurality of second glass portions, a camera for capturing an image formed by the lens, and a lens for focusing the light that passes through the groove forming unit. the plurality of first single-core optical fibers arranged in the knit and the plurality of second glass portions of the plurality of second single-core optical fibers by electric discharge; a high-voltage generating circuit that generates an electric discharge between the pair of discharge electrodes; a movable stage that moves the plurality of first single-core optical fibers in the longitudinal direction of the first multi-core optical fiber and moves the plurality of second single-core optical fibers in the longitudinal direction of the second multi-core optical fiber; an image processing unit that determines at least one of the fiber pitches of the plurality of first single-core optical fibers and the plurality of second single-core optical fibers based on an image captured by the camera; and a fusion condition processing unit that selects or calculates the fusion conditions corresponding to the determined fiber pitches.

[0008] In the optical fiber fusion splicer, the fusion condition processing unit sets the fusion conditions corresponding to the fiber pitch determined by the image processing unit, thereby enabling the first single-core optical fibers constituting the first multi-core optical fiber to be fusion-spliced ​​one-to-one with the second single-core optical fibers constituting the second multi-core optical fiber under the fusion conditions according to the fiber pitch.

[0009] In the optical fiber fusion splicer according to the first aspect of the present invention, the image processing unit may determine the number of the plurality of first single-core optical fibers and the number of the plurality of second single-core optical fibers based on the image, and the fusion condition processing unit may set the fusion conditions by selection or calculation corresponding to the fiber pitch of the plurality of first single-core optical fibers, the fiber pitch of the plurality of second single-core optical fibers, the number of the plurality of first single-core optical fibers, and the number of the plurality of second single-core optical fibers.

[0010] In the optical fiber fusion splicer according to the first aspect of the present invention, the image processing unit determines the diameter of at least one of the plurality of first single-core optical fibers or the diameter of at least one of the plurality of second single-core optical fibers based on the image, and the fusion condition processing unit may set the fusion conditions corresponding to the fiber pitch of the plurality of first single-core optical fibers and the diameters of the plurality of first single-core optical fibers by selection or calculation, or may set the fusion conditions corresponding to the fiber pitch of the plurality of second single-core optical fibers and the diameters of the plurality of second single-core optical fibers by selection or calculation.

[0011] In the optical fiber fusion splicer according to the first aspect of the present invention, the image processing unit may determine the diameter of at least one of the plurality of first single-core optical fibers and the diameter of at least one of the plurality of second single-core optical fibers based on the image, and the fusion condition processing unit may set the fusion conditions by selection or calculation corresponding to the fiber pitch of the plurality of first single-core optical fibers, the fiber pitch of the plurality of second single-core optical fibers, the diameters of the plurality of first single-core optical fibers, and the diameters of the plurality of second single-core optical fibers.

[0012] A second aspect of the present invention provides an optical fiber fusion splicing method for fusion-splicing a first multi-core optical fiber and a second multi-core optical fiber using an optical fiber fusion splicer. The optical fiber fusion splicer includes: an exchangeable groove forming unit having a plurality of first positioning grooves for equally spacedly arranging a plurality of first single-core optical fibers, each of which constitutes the first multi-core optical fiber and has a plurality of first glass portions; and a plurality of second positioning grooves for equally spacedly arranging a plurality of second single-core optical fibers, each of which constitutes the second multi-core optical fiber and has a plurality of second glass portions; an illumination unit for irradiating light onto the plurality of first single-core optical fibers and the plurality of second single-core optical fibers arranged in the groove forming unit; a lens for focusing the light that passes through the plurality of first glass portions, peripheral areas of the plurality of first glass portions, the plurality of second glass portions, and peripheral areas of the plurality of second glass portions; and a camera for capturing an image formed by the lens. The groove forming unit is equipped with a pair of discharge electrodes that heat and melt the multiple first glass portions of the multiple first single-core optical fibers and the multiple second glass portions of the multiple second single-core optical fibers by discharge, a high-voltage generating circuit that generates a discharge between the pair of discharge electrodes, and a movable stage that moves the multiple first single-core optical fibers in the longitudinal direction of the first multi-core optical fiber and moves the multiple second single-core optical fibers in the longitudinal direction of the second multi-core optical fiber, and the fusion splicing method determines the fiber pitch of the multiple first single-core optical fibers and the fiber pitch of the multiple second single-core optical fibers based on an image captured by the camera, and sets fusion conditions corresponding to the determined fiber pitches by selection or calculation.

[0013] In the above-described optical fiber fusion splicing method, fusion conditions corresponding to the fiber pitch determined based on the image captured by the camera are set, thereby making it possible to fusion-splice the first single-core optical fibers constituting the first multi-core optical fiber and the second single-core optical fibers constituting the second multi-core optical fiber in a one-to-one correspondence under the fusion conditions according to the fiber pitch.

[0014] In the optical fiber fusion splicing method according to the second aspect of the present invention, the fusion conditions may be set before the first multi-core optical fiber and the second multi-core optical fiber are fusion spliced ​​together.

[0015] In the optical fiber fusion splicing method according to the second aspect of the present invention, the number of the plurality of first single-core optical fibers and the number of the plurality of second single-core optical fibers may be determined based on the image, and the fusion conditions corresponding to the fiber pitch of the plurality of first single-core optical fibers, the fiber pitch of the plurality of second single-core optical fibers, the number of the plurality of first single-core optical fibers, and the number of the plurality of second single-core optical fibers may be set by selection or calculation.

[0016] In the optical fiber fusion splicing method according to the second aspect of the present invention, the diameter of at least one of the plurality of first single-core optical fibers or the diameter of at least one of the plurality of second single-core optical fibers is determined based on the image, and the fusion conditions corresponding to the fiber pitch of the plurality of first single-core optical fibers and the diameters of the plurality of first single-core optical fibers are set by selection or calculation, or the fusion conditions corresponding to the fiber pitch of the plurality of second single-core optical fibers and the diameters of the plurality of second single-core optical fibers are set by selection or calculation.

[0017] In the optical fiber fusion splicing method according to the second aspect of the present invention, the diameter of at least one of the plurality of first single-core optical fibers and the diameter of at least one of the plurality of second single-core optical fibers may be determined based on the image, and the fusion conditions corresponding to the fiber pitch of the plurality of first single-core optical fibers, the fiber pitch of the plurality of second single-core optical fibers, the diameters of the plurality of first single-core optical fibers, and the diameters of the plurality of second single-core optical fibers may be set by selection or calculation. [Effects of the Invention]

[0018] According to the present invention, a plurality of first single-core optical fibers constituting a first multi-core optical fiber and a plurality of second single-core optical fibers constituting a second multi-core optical fiber can be fusion-spliced ​​in a one-to-one correspondence under fusion conditions according to the fiber pitch. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing an optical fiber fusion splicer according to a first embodiment as viewed from the front-rear direction, and is a schematic cross-sectional view showing the optical fiber fusion splicer. [Figure 2A] 1 is a diagram showing an optical fiber fusion splicer according to a first embodiment as viewed from the left and right direction, and is a schematic cross-sectional view showing the optical fiber fusion splicer. FIG. [Figure 2B] 2B is a diagram showing a main part of the optical fiber fusion splicer according to the first embodiment, and is a schematic cross-sectional view showing an enlarged view of the part indicated by the symbol E in FIG. 2A. FIG. [Figure 3] 2B is a plan view showing the groove forming unit, as viewed from above, which is provided in the optical fiber fusion splicer shown in FIGS. 1 and 2A. FIG. [Figure 4] 4 is a diagram showing a state in which a pair of discharge electrodes and a pair of glass portions of multi-core optical fibers are arranged in the groove forming unit shown in FIG. 3. FIG. [Figure 5] FIG. 2 is a block diagram illustrating the function of the optical fiber fusion splicer according to the first embodiment. [Figure 6] 6 is a diagram showing an example of an image captured by a camera provided in the optical fiber fusion splicer shown in FIGS. 2A and 5. FIG. [Figure 7] 7 is a graph showing the distribution of luminance on a line segment L1 of the image shown in FIG. 6. [Figure 8] FIG. 2 is a diagram showing an example of a table showing the relationship between fiber pitch and discharge intensity in the optical fiber fusion splicer according to the first embodiment. [Figure 9] 10 is a diagram showing a first example of the relationship between the positions of multiple single-core optical fibers and the distribution of temperature regions caused by discharges generated between a pair of discharge electrodes when the fiber pitch is large. FIG. [Figure 10]A figure showing a second example of the relationship between the positions of multiple single-core optical fibers and the distribution of temperature areas caused by discharges generated between a pair of discharge electrodes when the fiber pitch is smaller than in the first example. [Figure 11] FIG. 10 is a block diagram illustrating the functions of an optical fiber fusion splicer according to a second embodiment. [Figure 12] FIG. 10 is a diagram showing an example of a table showing the relationship between fiber pitch and fusion conditions in the optical fiber fusion splicer according to the second embodiment. [Figure 13] FIG. 10 is a diagram showing an example of a table showing the relationship between fiber pitch, the number of single-core optical fibers, and discharge intensity in an optical fiber fusion splicer according to another embodiment. [Figure 14] FIG. 10 is a diagram showing an example of a table showing the relationship between fiber pitch, diameter of a single optical fiber, and discharge intensity in an optical fiber fusion splicer according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] First Embodiment An optical fiber fusion splicer according to a first embodiment of the present invention will now be described with reference to FIGS. 1, 2A, and 2B, the optical fiber fusion splicer 10 of the first embodiment is configured to fusion-splice two multi-core optical fibers (a first multi-core optical fiber and a second multi-core optical fiber). Specifically, the optical fiber fusion splicer 10 fusion-splices one first single-core optical fiber among a plurality of first single-core optical fibers constituting the first multi-core optical fiber to one second single-core optical fiber among a plurality of second single-core optical fibers constituting the second multi-core optical fiber. Thus, the optical fiber fusion splicer 10 is configured to fusion-splice the plurality of first single-core optical fibers constituting the first multi-core optical fiber to the plurality of second single-core optical fibers constituting the second multi-core optical fiber.

[0021] Here, "one first single-core optical fiber and one second single-core optical fiber are fusion-spliced ​​in correspondence" means that before fusion-splicing, one first single-core optical fiber and one second single-core optical fiber face each other, and in this state, one first single-core optical fiber and one second single-core optical fiber are fusion-spliced. Furthermore, the plurality of first single-core optical fibers are first multi-core optical fibers and can be referred to as a first fiber group, and the plurality of second single-core optical fibers are second multi-core optical fibers and can be referred to as a second fiber group. In the following description, "fusion-splicing a plurality of first single-core optical fibers and a plurality of second single-core optical fibers so that one first single-core optical fiber and one second single-core optical fiber are fusion-spliced ​​correspondingly" may be simply referred to as "fusion-splicing a plurality of first single-core optical fibers and a plurality of second single-core optical fibers."

[0022] In this specification, the optical fiber F1 corresponds to the first single-core optical fiber of the present invention, and the optical fiber F1 may be referred to as the “first single-core optical fiber F1.” A plurality of single-core optical fibers F1 constitute a first multi-core optical fiber MF1. The optical fiber F2 corresponds to the second single-core optical fiber of the present invention, and may be referred to as the “second single-core optical fiber F2.” A plurality of single-core optical fibers F2 constitute a second multi-core optical fiber MF2. Each of the optical fibers F1 and F2 includes a glass portion G and a coating portion C that coats the glass portion G. That is, the first single-core optical fiber F1 includes a first glass portion G1 and a first coating portion C1 that coats the first glass portion G1, and the second single-core optical fiber F2 includes a second glass portion G2 and a second coating portion C2 that coats the second glass portion G2.

[0023] In this embodiment, the first multi-core optical fiber MF1 is made up of eight optical fibers F1 (first fiber F1, second fiber F1, . . . , to eighth fiber F1). Similarly, the second multi-core optical fiber MF2 is composed of eight optical fibers F2 (first fiber F2, second fiber F2, . . . , to eighth fiber F2). In this embodiment, eight optical fibers F1 and eight optical fibers F2 are fusion spliced ​​in one-to-one correspondence. In the embodiment described below, the number of single optical fibers constituting each of the first multi-core optical fiber MF1 and the second multi-core optical fiber MF2 will be described as eight.

[0024] In the present invention, the number of single-core optical fibers is not limited to eight. The number of single-core optical fibers may be less than eight or more than eight. In other words, the number N of single-core optical fibers may be, for example, an integer equal to or greater than 2. In other words, each of the first multi-core optical fiber MF1 and the second multi-core optical fiber MF2 is made up of a plurality of single-core optical fibers, from the first single-core optical fiber to the Nth single-core optical fiber.

[0025] The optical fiber fusion splicer 10 can fusion-splice a plurality of single-core optical fibers F1, F2 that make up the multi-core optical fibers MF1, MF2 all at once. The single-core optical fibers F1 may be connected in a line to form a multi-core optical fiber, or the single-core optical fibers F1 may not be connected. The same applies to the single-core optical fibers F2.

[0026] The optical fiber fusion splicer 10 includes a pair of movable stages 11 (first movable stage 11L, second movable stage 11R), a pair of fiber holders 12 (first fiber holder 12L, second fiber holder 12R), a groove forming unit 13, a pair of fiber clamps 14 (first fiber clamp 14L, second fiber clamp 14R), and a pair of discharge electrodes 15 (first discharge electrode 15A, second discharge electrode 15B). The direction in which the pair of movable stages 11 (11L, 11R) are aligned (X direction) and the direction in which the pair of discharge electrodes 15 (15A, 15B) are aligned (Y direction) are perpendicular to each other.

[0027] In this specification, the direction in which the pair of movable stages 11 (11L, 11R) are aligned is represented by the X axis and may be referred to as the left-right direction X. The direction in which the pair of discharge electrodes 15 (15A, 15B) are aligned is represented by the Y axis and may be referred to as the front-back direction Y. Furthermore, the direction perpendicular to both the left-right direction X and the front-back direction Y is represented by the Z axis and may be referred to as the up-down direction Z. The left-right direction X is also the direction in which the optical fibers F1 and F2 extend, and the front-rear direction Y is also the direction in which the multiple single-core optical fibers F1 and F2 are arranged side by side.

[0028] The pair of movable stages 11 (11L, 11R) are arranged with a gap in the left-right direction X. Each movable stage 11 is driven by a driving source (not shown) such as an actuator, and is thereby movable in the left-right direction X on a base (not shown). The pair of movable stages 11 (11L, 11R) can move toward or away from each other in the left-right direction X.

[0029] Each of the pair of fiber holders 12 (12L, 12R) is configured to sandwich and hold optical fibers F1, F2 including coatings C (C1, C2). The fiber holders 12 (12L, 12R) can hold multi-core optical fibers MF1, MF2. That is, the first fiber holder 12L located on the left side in FIG. 1 can hold the multi-core optical fiber MF1. The second fiber holder 12R located on the right side in FIG. 1 can hold the multi-core optical fiber MF2. The pair of fiber holders 12 (12L, 12R) are detachably fixed to each of the pair of movable stages 11 (11L, 11R). When the fiber holders 12 (12L, 12R) holding the optical fibers F1, F2 are fixed to the movable stages 11 (11L, 11R), the longitudinal directions of the optical fibers F1, F2 are oriented in the left-right direction X. In this state, the movable stage 11 (11L, 11R) can move the optical fibers F1, F2 in the longitudinal direction of the optical fibers F1, F2. The above-described fiber holders 12 (12L, 12R) may be, for example, non-detachable from the movable stage 11 (11L, 11R).

[0030] The groove forming unit 13 is disposed on a base (not shown) and is located between the pair of movable stages 11 (11L, 11R) in the left-right direction X. As shown in FIGS. 1 to 3, the groove forming unit 13 is formed with a through-hole 131 penetrating in the up-down direction Z. The groove forming unit 13 has a positioning groove 132. Specifically, in FIG. 3, the groove forming unit 13 has a first positioning groove 132L located on the left side and a second positioning groove 132R located on the right side. The positioning grooves 132 (132L, 132R) are formed in areas on both sides of the through-hole 131 in the left-right direction X on the upper surface of the groove forming unit 13. The positioning grooves 132 (132L, 132R) extend along the left-right direction X. In FIG. 2B, the positioning groove 132 has a V-shaped cross-section (V-groove), but it may also have a U-shaped groove or a trapezoidal groove, for example. As shown in FIGS. 1, 2A, 2B, and 4, the positioning grooves 132 (132L, 132R) accommodate the glass portions G exposed at the tips of the optical fibers F1 and F2 extending from the fiber holders 12 (12L and 12R). Specifically, in FIG. 4, the first positioning groove 132L located on the left accommodates the first glass portion G1 exposed at the tip of the optical fiber F1. Similarly, the second positioning groove 132R located on the right accommodates the second glass portion G2 exposed at the tip of the optical fiber F2. This allows the positioning grooves 132 to position (align) the glass portions G1 and G2 of the optical fibers F1 and F2. In FIG. 1, the groove forming unit 13 is shown in a cross-sectional view perpendicular to the front-rear direction Y, passing through the bottom of the positioning groove 132 (see FIG. 2B). Therefore, although the glass portion G (G1, G2) is spaced apart from the positioning groove 132 in FIG. 1, in reality, the glass portion G contacts the inner surface of the positioning groove 132 as shown in FIG. 2B.

[0031] As shown in FIG. 3, the multiple positioning grooves 132 (132L, 132R) are aligned in the front-rear direction Y on both sides of the through hole 131. The multiple positioning grooves 132 (132L, 132R) aligned in the front-rear direction Y are aligned at equal intervals. This allows the glass portions G1 of the multiple single-core optical fibers F1 to be positioned in the multiple positioning grooves 132L, respectively, and the glass portions G2 of the multiple single-core optical fibers F2 to be positioned in the multiple positioning grooves 132R, respectively, as shown in FIG. This allows the glass portions G1, G2 of the multiple single-core optical fibers F1, F2 to be aligned at equal intervals.

[0032] The groove forming unit 13 is detachable from a base (not shown). That is, the groove forming unit 13 is replaceable. This allows the optical fiber fusion splicer 10 to use a groove forming unit selected from multiple types of groove forming units 13 prepared in advance. The multiple types of groove forming units 13 include groove forming units with different distances (pitches) between the centers of adjacent positioning grooves 132 in the front-rear direction Y, groove forming units with different numbers of positioning grooves 132 arranged in the front-rear direction Y, and groove forming units with different widths of the positioning grooves 132 in the front-rear direction Y. By replacing the groove forming unit 13, it is possible to change the fiber pitch of the multiple single-core optical fibers F1, F2 that the optical fiber fusion splicer 10 can handle, the number of optical fibers F1, F2, and the diameters of the optical fibers F1, F2. The "fiber pitch of the optical fibers F1, F2" refers to the distance between the centers of adjacent first single-core optical fibers F1 or the distance between the centers of adjacent second single-core optical fibers F2. In other words, "the fiber pitch of the optical fibers F1, F2" means "the fiber pitch of the plurality of first single-core optical fibers and the fiber pitch of the plurality of second single-core optical fibers."

[0033] Groove forming unit 13, which positions the glass portions G (first glass portion G1, second glass portion G2) of a pair of optical fibers F1, F2 so that they face each other, may be formed, for example, as two groove forming members (first groove forming member, second groove forming member) separated in the left-right direction X. In this case, it is sufficient that each of the first groove forming member and the second groove forming member has positioning grooves 132L, 132R.

[0034] The pair of fiber clamps 14 (14L, 14R) are positioned above the groove forming unit 13 and are configured to open and close relative to the top surface of the groove forming unit 13. The pair of fiber clamps 14 (14L, 14R) open and close relative to regions on both sides of the through-hole 131 in the left-right direction X on the top surface of the groove forming unit 13. By closing the fiber clamps 14 relative to the top surface of the groove forming unit 13, the glass portions G1, G2 of the optical fibers F1, F2 are held between the groove forming unit 13 and the fiber clamps 14 (14L, 14R), preventing the glass portions G (G1, G2) from slipping out upward from the positioning grooves 132 (132L, 132R). Note that the closing force of the fiber clamps 14 is set so that the glass portions G1, G2 of the optical fibers F1, F2 can be moved in the longitudinal direction (left-right direction X) of the positioning grooves 132 (132L, 132R) even when the fiber clamps 14 are closed relative to the top surface of the groove forming unit 13. The closing force of the fiber clamp 14 is determined by, for example, a spring or magnet that biases the fiber clamp 14 toward the groove forming unit 13, or the weight of the fiber clamp 14 itself.

[0035] As shown in FIGS. 2A, 2B, and 4, the pair of discharge electrodes 15 (15A, 15B) are arranged side by side with a gap in the front-rear direction Y. The pair of discharge electrodes 15 (15A, 15B) are positioned so as to sandwich an area between a first positioning groove 132L and a second positioning groove 132R that face each other in the left-right direction X in the groove forming unit 13, and so as to sandwich the positioning groove 132 from the front-rear direction Y. The pair of discharge electrodes 15 are also positioned on both sides of the through hole 131 in the front-rear direction Y. The pair of discharge electrodes 15 (15A, 15B) may be positioned with respect to the groove forming unit 13, for example, by being placed in electrode grooves 133 (133A, 133B) formed in the upper surface of the groove forming unit 13, as shown in FIGS. 3 and 4. When a pair of optical fibers F1, F2 facing each other in the left-right direction X are arranged in the groove forming unit 13, the ends of the glass portions G1, G2 of the optical fibers F1, F2 (the ends that overlap the through holes 131 as shown in Figure 4) are heated and melted by the discharge generated between the pair of discharge electrodes 15 described above.

[0036] The positional relationship between the discharge electrodes 15 (15A, 15B) and the multi-core optical fibers MF1 and MF2 will be specifically described. The discharge electrode 15A has an electrode tip 15AE (first electrode tip). The discharge electrode 15B has an electrode tip 15BE (second electrode tip). In the front-rear direction Y, the electrode tip 15AE faces the electrode tip 15BE.

[0037] 4, symbol W1 refers to the distance between the center portions (glass portions G1) of two optical fibers F1 located on the outer sides of the first multi-core optical fiber MF1 in the front-rear direction Y. Specifically, symbol W1 corresponds to the distance between the position of the center portion of the optical fiber F1 (glass portion G1 of the first optical fiber F1) closest to electrode tip 15AE among the eight optical fibers F1 that make up the first multi-core optical fiber MF1 and are aligned in the front-rear direction Y, and the position of the center portion of the optical fiber F1 (glass portion G1 of the eighth optical fiber F1) closest to electrode tip 15BE. The center position of this distance W1 is indicated by symbol CL1.

[0038] Symbol W2 refers to the distance between the center portions (glass portions G2) of the two optical fibers F2 located on the outer sides of the second multi-core optical fiber MF2 in the front-rear direction Y. Specifically, symbol W2 corresponds to the distance between the position of the center portion of the optical fiber F2 (glass portion G2 of the first optical fiber F2) closest to electrode tip 15AE among the eight optical fibers F2 that make up the second multi-core optical fiber MF2 and are aligned in the front-rear direction Y, and the position of the center portion of the optical fiber F2 (glass portion G2 of the eighth optical fiber F2) closest to electrode tip 15BE. The center position of this distance W2 is indicated by symbol CL2.

[0039] 4, eight optical fibers F1 constituting the first multi-core optical fiber MF1 and eight optical fibers F2 constituting the second multi-core optical fiber MF2 are arranged in a region SR sandwiched between electrode tip 15AE and electrode tip 15BE. Specifically, in the central region between electrode tip 15AE and electrode tip 15BE, that is, in the center of region SR, the eight optical fibers F1 and the eight optical fibers F2 are arranged in a one-to-one correspondence.

[0040] In other words, in the front-rear direction Y, the center position CL1 of the distance W1 of the first multi-core optical fiber MF1 and the center position CL2 of the distance W2 of the second multi-core optical fiber MF2 coincide at the midpoint P. The midpoint P is located approximately in the center of the imaginary line connecting the electrode tip 15AE and the electrode tip 15BE. Here, the phrase "located approximately in the center" means that the midpoint P may be slightly shifted from the center position of the imaginary line connecting the electrode tip 15AE and the electrode tip 15BE, as long as the effect of optimizing the amount of heat received by the multiple single-core optical fibers F1 and F2 due to discharge can be obtained.

[0041] As shown in FIG. 2A, the optical fiber fusion splicer 10 further includes an illumination unit 16, a lens 17, and a camera 18. The illumination unit 16 irradiates light onto the glass portions G1 and G2 of the optical fibers F1 and F2 arranged in the groove forming unit 13. The illumination unit 16 is arranged above the groove forming unit 13. The light from the illumination unit 16 irradiates the glass portions G1 and G2 of the optical fibers F1 and F2 (see FIG. 4) that are positioned so as to overlap with the through hole 131 of the groove forming unit 13 in the vertical direction Z, and passes through the through hole 131. The lens 17 collects the light from the illumination unit 16 that passes through the glass portions G1 and G2 of the optical fibers F1 and F2 and the area around the glass portions G1 and G2. The camera 18 captures the image formed by the lens 17 and takes an image. The optical fiber fusion splicer 10 may include only one optical system consisting of an illumination unit 16, a lens 17, and a camera 18, as illustrated in FIG. 2A , or may include, for example, two optical systems. When the optical fiber fusion splicer 10 includes two optical systems, for example, the two illumination units 16 may irradiate light toward the glass portions G1 and G2 of the optical fibers F1 and F2 from two different directions. Images including the glass portions G1 and G2 of the optical fibers F1 and F2 may be captured along two axes (two directions) from the directions (positions) at which the two lenses 17 and two cameras 18 are disposed. In this case, images including the glass portions G1 and G2 of the optical fibers F1 and F2 can be acquired more accurately.

[0042] 5, the optical fiber fusion splicer 10 further includes an image processing unit 21, a fusion condition processing unit 22, a storage unit 23, and a high-voltage generating circuit 24. The image processing unit 21 and the fusion condition processing unit 22 may form, for example, a condition setting device 30, which will be described later. The image processing unit 21 determines at least one of the fiber pitches of the plurality of first single-core optical fibers F1 and the fiber pitches of the plurality of second single-core optical fibers F2 based on the image captured by the camera 18. The fusion condition processing unit 22 selects or calculates and sets the fusion conditions corresponding to the fiber pitch obtained by the image processing unit 21 .

[0043] Each of the image processing unit 21 and the fusion condition processing unit 22 is a computer having, for example, circuits such as electric circuits and electronic circuits, a storage device, a CPU (Central Processing Unit), etc. The computer performs an acquisition process to acquire an image captured by the camera 18. Furthermore, the computer performs processes such as arithmetic processing, calculation processing, determination processing, selection processing, and setting processing based on the image (image information) obtained by the acquisition process. The computer may be operated, for example, based on a computer program for executing such processes. The computer program may be stored, for example, in the image processing unit 21, the fusion condition processing unit 22, and the storage unit 23. The storage unit 23 is connected to the fusion condition processing unit 22. The storage unit 23 may constitute a part of the computer described above.

[0044] (Method of calculating fiber pitch by image processing unit 21) The method of calculating the fiber pitch by the image processing unit 21 will be specifically described with reference to FIGS. In order to find the fiber pitch, the image processing unit 21 acquires an image showing a plurality of (two in the illustrated example) first single-core optical fibers F1 and a plurality of second single-core optical fibers F2 lined up in the front-to-rear direction Y, as exemplified in Fig. 6. The image shown in Fig. 6 shows the glass portions G1, G2 of the two pairs of optical fibers F1, F2 before fusion splicing, and a pair of discharge electrodes 15. The glass portions G1 of the plurality (two) optical fibers F1 are lined up at intervals in the front-to-rear direction Y, and the glass portions G2 of the plurality (two) optical fibers F2 are lined up at intervals in the front-to-rear direction Y. In the image shown in Fig. 6, the brightness level of each pixel is represented by a grayscale, with higher brightness being whiter and lower brightness being blacker. In the image shown in Fig. 6, the brightness is high in the center of the glass portion G in the front-to-back direction Y (radial direction of the glass portion G), and low in brightness at both end portions of the glass portion G in the front-to-back direction Y. This is because the cross section of the glass portion G perpendicular to the longitudinal direction (left-to-right direction X) of the optical fibers F1 and F2 is circular, and when light from the illumination unit 16 passes through the glass portion G in the radial direction of the glass portion G, the light is concentrated at the center of the glass portion G.

[0045] Next, the image processing unit 21 derives the luminance distribution in the direction in which the glass portions G2 of the plurality of second single-core optical fibers F2 are arranged (front-rear direction Y) at the position of the line segment L1 shown in FIG. 6 from the acquired image. The line segment L1 is a line extending in the front-rear direction Y. The position of the line segment L1 in the left-right direction X may be set at a position where the glass portions G1, G2 of the optical fibers F1, F2 are present in the left-right direction X. In other words, the line segment L1 may not be set at a position (gap) between a pair of optical fibers F1, F2 arranged in the left-right direction X. As shown in FIG. 6, when the position of the line segment L1 is set so as to straddle a plurality (two) of second single-core optical fibers F2, the fiber pitch of the second single-core optical fibers F2 can be calculated. When the position of the line segment L1 is set so as to straddle a plurality (two) of first single-core optical fibers F1, the fiber pitch of the first single-core optical fiber F1 can be calculated. The image processing unit 21 may obtain only one of the fiber pitches of the plurality of first single-core optical fibers F1 and the fiber pitches of the plurality of second single-core optical fibers F2, or may obtain both the fiber pitches of the plurality of first single-core optical fibers F1 and the fiber pitches of the plurality of second single-core optical fibers F2.

[0046] Fig. 7 shows the distribution of luminance along the line segment L1 shown in Fig. 6. In Fig. 7, the vertical axis indicates position in the front-to-rear direction Y (the radial direction of the optical fibers F1 and F2), and the horizontal axis indicates luminance. Furthermore, luminance value B0 is the luminance value of light from the illumination unit 16 that reaches the camera 18 without passing through the glass portion G. Luminance value B1 is the luminance value of light from the illumination unit 16 that passes through the glass portion G, which has a circular cross section, and is thereby focused at the center of the glass portion G in the front-to-rear direction Y, and is higher than luminance value B0. Based on the derived brightness distribution, the image processing unit 21 identifies two positions Y1, Y2 in the front-rear direction Y that correspond to the brightness value B1, and calculates the distance D1 between the two positions Y1, Y2. The image processing unit 21 determines this distance D1 as the fiber pitch. The determined fiber pitch is output from the image processing unit 21 to the fusion condition processing unit 22. That is, the fiber pitch is determined based on, for example, the distance D1 between first single-core optical fibers F1 that are adjacent to each other in the front-rear direction Y, or the distance D1 between second single-core optical fibers F2 that are adjacent to each other in the front-rear direction Y.

[0047] (Modification of the fiber pitch calculation method) The method for calculating the fiber pitch is not limited to the above-described embodiment. Next, a modified example of the method for calculating the fiber pitch will be described. In this variant, the following conditions are necessary: Multiple single-core optical fibers F1 are arranged at equal intervals in the forward and backward direction Y. A plurality of single-core optical fibers F2 are arranged at equal intervals in the forward and backward direction Y. The diameters K1 of the multiple single-core optical fibers F1 are the same. The diameters K2 of the multiple single-core optical fibers F2 are the same. Under this condition, the fiber pitch may be determined, for example, based on the distance W1 between two optical fibers F1 (the first optical fiber F1 and the eighth optical fiber F1) located at both ends of the first multi-core optical fiber MF1 in the forward / backward direction Y, among the multiple single-core optical fibers F1 that constitute the first multi-core optical fiber MF1, and the number N1 of the multiple single-core optical fibers F1.

[0048] This modification will be specifically described with reference to FIGS. 4, 6 and 7. FIG. As in the above-described embodiment, first, the image shown in Fig. 6 is obtained. In this image, the image processing unit 21 sets the position of the line segment L1 so that it intersects with multiple single-core optical fibers F1. The image processing unit 21 detects the number of positions indicated with high brightness on the line segment L1 that intersects with multiple single-core optical fibers F1. In the example shown in Fig. 7, it is detected that the number of single-core fibers is two (Y1, Y2), but in the case of the first multi-core optical fiber MF1 shown in Fig. 4, the image processing unit 21 detects that the number N1 of single-core optical fibers is eight.

[0049] Furthermore, the image processing unit 21 detects the positions of two single-core optical fibers (the first optical fiber F1 and the eighth optical fiber F1) located at both ends of the first multi-core optical fiber MF1 in the front-rear direction Y, among the eight optical fibers F1. Based on this detection result, the image processing unit 21 calculates the distance W1 shown in FIG.

[0050] Furthermore, the image processing unit 21 calculates the fiber pitch of the optical fiber F1 based on the diameter K1, the distance W1, and the number N1, which are the information about the plurality of single-core optical fibers F1 obtained as described above.

[0051] The fiber pitch of the optical fiber F2 may be calculated using a similar method. Specifically, the image processing unit 21 sets the position of the line segment L1 so that it intersects with multiple single-core optical fibers F2, and detects the number of positions on the line segment L1 that are indicated with high brightness. In the case of the second multi-core optical fiber MF2 shown in FIG. 4, the image processing unit 21 detects that the number N2 of single-core optical fibers is eight. Of the eight optical fibers F2, the image processing unit 21 detects the positions of two single-core optical fibers (the first optical fiber F2 and the eighth optical fiber F2) that are located at both ends of the second multi-core optical fiber MF2 in the forward / backward direction Y. Based on this detection result, the image processing unit 21 determines the distance W2 shown in FIG. 4. Furthermore, the image processing unit 21 calculates the fiber pitch of the optical fiber F2 based on the diameter K2, the distance W2, and the number N2, which are information about the multiple single-core optical fibers F2 obtained as described above.

[0052] It should be noted that the numbers N1 and N2 of single-core optical fibers do not have to be determined by automatic detection by the image processing unit 21. For example, the numbers N1 and N2 of single-core optical fibers may be directly input to the optical fiber fusion splicer 10 by an operator operating the optical fiber fusion splicer 10.

[0053] (Method of Setting Fusion Conditions by Fusion Condition Processing Unit 22) The fusion condition processing unit 22 sets fusion conditions corresponding to the determined fiber pitch. The fusion conditions are set before fusion splicing a pair of optical fibers F1, F2 facing each other in the left-right direction X. Specifically, the fusion condition processing unit 22 selects fusion conditions corresponding to the fiber pitch from information (condition data) representing the relationship between the fiber pitch and the fusion conditions. This information is stored in advance in the storage unit 23. In the first embodiment, the information representing the relationship between the fiber pitch and the fusion conditions is a table TB1 that associates the fiber pitch with the fusion conditions, as shown in FIG. 8. In this table TB1, different set values ​​of discharge intensity are associated with each fiber pitch.

[0054] In table TB1 shown in Fig. 8, the value of a current (discharge current value) flowing between the pair of discharge electrodes 15 is adopted as the fusion condition. The current value is one type of parameter for adjusting the discharge intensity. Note that in table TB1 shown in Fig. 8, for example, instead of the current value, a voltage value applied between the pair of discharge electrodes 15, a power value supplied to the pair of discharge electrodes 15, or the like may be adopted as another parameter for adjusting the discharge intensity.

[0055] Table TB1 shown in Fig. 8 can be created based on the results of preliminary experiments to determine the optimal discharge intensity settings for multiple types of fiber pitches that are expected to be actually used. Although Fig. 8 shows three types of fiber pitches as examples, the types of fiber pitches of the present invention are not limited to three. The fusion condition processing unit 22 sets the fusion conditions by reading from table TB1 the set value of discharge intensity (current value in FIG. 8) that corresponds to the fiber pitch determined by the image processing unit 21. For example, if the fiber pitch determined by the image processing unit 21 is "165 μm," the fusion condition processing unit 22 reads out the set value of discharge intensity "24.0 mA" from table TB1. The fusion condition processing unit 22 outputs the set fusion conditions (set value of discharge intensity) to the high-voltage generating circuit 24.

[0056] In the above-described embodiment, the fusion condition processing unit 22 selects and sets appropriate fusion conditions by referring to table TB1, but the fusion condition processing unit 22 may set optimal fusion conditions by determining the fusion conditions through calculation. For example, a calculation formula using environmental factors such as temperature, air pressure, and humidity as parameters in addition to the fiber pitch may be determined in advance through experiments, and the optimal fusion conditions may be calculated and set using the calculation formula when actually performing fusion splicing.

[0057] The high voltage generating circuit 24 shown in FIG. 5 generates a discharge between the pair of discharge electrodes 15 in accordance with the set value of the discharge intensity output from the fusion condition processing unit 22 .

[0058] Next, an example of an optical fiber fusion splicing method (optical fiber fusion splicing method) for fusion-splicing a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2 using the optical fiber fusion splicer 10 will be described.

[0059] When fusion-splicing a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2 using the optical fiber fusion splicer 10, first, as shown in FIGS. 1 and 2, a first fiber holder 12L holding the plurality of single-core optical fibers F1 is fixed on a first movable stage 11L. Similarly, a second fiber holder 12R holding the plurality of single-core optical fibers F2 is fixed on a second movable stage 11R. Furthermore, a plurality of glass portions G1 exposed from the coating portion C1 at the tip ends of the plurality of single-core optical fibers F1 extending from the fiber holder 12L are placed in a plurality of positioning grooves 132L of the groove forming unit 13 (see FIG. 4). A plurality of glass portions G2 exposed from the coating portion C2 at the tip ends of the plurality of single-core optical fibers F2 extending from the fiber holder 12R are placed in a plurality of positioning grooves 132R of the groove forming unit 13 (see FIG. 4). Next, the pair of fiber clamps 14 (14L, 14R) are closed to hold the glass parts G1, G2 of the multiple single-core optical fibers F1 and the multiple single-core optical fibers F2 in the groove forming unit 13 so that the glass part G1 of one of the multiple single-core optical fibers F1 and the glass part G2 of one of the multiple single-core optical fibers F2 face each other to form a pair.

[0060] Thereafter, the pair of movable stages 11 (11L, 11R) are moved in the left-right direction X so that the tip portions of the glass portions G1, G2 of the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 overlap with the through holes 131 of the groove forming unit 13 in the up-down direction Z. This adjusts the positions of the tip portions of the glass portions G1, G2 of the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 in the left-right direction. Furthermore, by moving the pair of movable stages 11 (11L, 11R) in the left-right direction X, the gap between the opposing tip portions of the glass portions G1, G2 of the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 is adjusted. The adjustment of the positions of the tip portions of the glass portions G1, G2 in the left-right direction X may be performed with reference to an image captured by the camera 18 (for example, an image as shown in FIG. 6 ).

[0061] Thereafter, the image processing unit 21 determines the fiber pitches of the plurality of single-core optical fibers F1, F2 based on the image acquired from the camera 18. The image processing unit 21 only needs to determine at least one of the fiber pitches of the plurality of first single-core optical fibers F1 and the fiber pitches of the plurality of second single-core optical fibers F2. The image processing unit 21 outputs the determined fiber pitches to the fusion condition processing unit 22. Then, the fusion condition processing unit 22 reads out the set value of the discharge intensity as the fusion condition corresponding to the determined fiber pitch from the table TB1 stored in the storage unit 23, and outputs it to the high voltage generating circuit 24.

[0062] Finally, based on the set value of the discharge intensity output from the fusion condition processing unit 22, the multiple single-core optical fibers F1 and the multiple single-core optical fibers F2 are fusion-spliced ​​so that a pair of one first single-core optical fiber and one second single-core optical fiber are fusion-spliced. At this time, the pair of movable stages 11 (11L, 11R) are moved toward each other to butt the multiple first glass portions G and the multiple second glass portions G so that one first glass portion G1 corresponds to one second glass portion G2. In this state, the high-voltage generating circuit 24 generates a discharge between the pair of discharge electrodes 15 according to the set value of the discharge intensity output from the fusion condition processing unit 22, thereby heating and melting the multiple glass portions G1 and G2. As a result, the multiple first glass portions G1 and the multiple second glass portions G2 are integrated and fusion-spliced. In addition, during fusion splicing, for example, a discharge may be generated between a pair of discharge electrodes 15 before the multiple first glass parts G1 and the multiple second glass parts G2 are butted together, and after a predetermined time has passed, the multiple first glass parts G1 and the multiple second glass parts G2 are butted together.

[0063] As described above, according to the optical fiber fusion splicer 10 of the first embodiment and the optical fiber fusion splicing method using the optical fiber fusion splicer 10, the discharge intensity setting value (fusion conditions) corresponding to the fiber pitch is set based on the image acquired from the camera 18. This makes it possible to fusion-splice the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 under optimal fusion conditions according to the fiber pitch of the plurality of single-core optical fibers F1 and the fiber pitch of the plurality of single-core optical fibers F2. This point will be described with reference to FIGS. 9 and 10.

[0064] 9 and 10 show a schematic diagram of the distribution of temperature regions due to the discharge (air discharge) that occurs between a pair of discharge electrodes 15. FIG. The temperature regions shown in Figures 9 and 10 include a high temperature region TH, a medium temperature region TM, and a low temperature region TL as relative temperature classifications in the region where discharge is occurring. The high temperature region TH is located at and around the tip of each discharge electrode 15, and is the region with the highest temperature in the region where discharge is occurring. The medium temperature region TM is located outside the high temperature region TH, and is a region with a lower temperature than the high temperature region TH. The low temperature region TL is located even further outside the medium temperature region TM, and is a region with a lower temperature than the medium temperature region TM. Since the fusion conditions such as discharge intensity are the same in both FIGS. 9 and 10, the temperature distribution is also the same in both FIGS.

[0065] 9 and 10 differ from each other in terms of the fiber pitch of the multiple single-core optical fibers F1, F2. The example shown in FIG. 9 has a large fiber pitch, while the example shown in FIG. 10 has a small fiber pitch. In the example shown in FIG. 9, the large fiber pitch causes all of the optical fibers F1, F2 to be located generally in the medium-temperature region TM. In contrast, the example shown in FIG. 10 has a small fiber pitch, causing some of the optical fibers F1, F2 to be located in the low-temperature region TL. Therefore, in the example shown in FIG. 10, the amount of heat received by the multiple single-core optical fibers F1, F2 due to the discharge is smaller than in the example shown in FIG. 9. Therefore, assuming that the amount of heat received by the multiple single-core optical fibers F1, F2 due to the discharge in the example shown in FIG. 9 is optimal for fusion splicing, the amount of heat received by the multiple single-core optical fibers F1, F2 due to the discharge is insufficient in the example shown in FIG. 10. Furthermore, although not shown, if the fiber pitch were larger than in the example shown in FIG. 9, the amount of heat received by the multiple single-core optical fibers F1, F2 due to the discharge would be excessive. If the amount of heat received by the optical fibers F1 and F2 is not appropriate, the splice loss of the optical fibers F1 and F2 after fusion splicing will be large.

[0066] In contrast, in the first embodiment, the set value of the discharge intensity is changed according to the fiber pitch, so the distribution of the temperature region caused by the discharge generated between the pair of discharge electrodes 15 can be changed according to the fiber pitch. As a result, even if the fiber pitch changes, the amount of heat received by the multiple single-core optical fibers F1, F2 due to the discharge can be optimized. In other words, it is possible to fusion-splice the multiple single-core optical fibers F1 and the multiple single-core optical fibers F2 under optimal fusion conditions according to the fiber pitch of the multiple single-core optical fibers F1, F2. As a result, the connection loss of the optical fibers F1, F2 after fusion splicing can be kept small.

[0067] Furthermore, according to the first embodiment, even if the fiber pitches of the plurality of single-core optical fibers F1, F2 to be fusion spliced ​​change, the loss of work time for fusion splicing can be kept small. Specifically, in an optical fiber fusion splicer that does not have the function of setting the optimum discharge intensity according to the fiber pitch, it is necessary to calibrate the discharge intensity so that the amount of heat received by the single-core optical fibers F1 and F2 due to the discharge is appropriate every time the fiber pitch changes, which results in unnecessarily long fusion splicing times. In contrast, in the first embodiment, the optimum discharge intensity is set according to the fiber pitch, which eliminates the need for additional work to calibrate the discharge intensity in order to set the optimum fusion conditions every time the fiber pitch changes, thereby minimizing lost work time.

[0068] Furthermore, according to the first embodiment, the image processing unit 21 automatically determines the fiber pitches of the plurality of single-core optical fibers F1, F2, and the fusion condition processing unit 22 automatically sets the fusion conditions according to the fiber pitch. As a result, the optimum fusion conditions according to the fiber pitch are automatically set simply by attaching the plurality of single-core optical fibers F1, F2 to the optical fiber fusion splicer 10. This eliminates the need for the operator operating the optical fiber fusion splicer 10 to manually set the fusion conditions, and prevents setting errors by the operator.

[0069] Furthermore, in the optical fiber fusion splicing method of the first embodiment, the fusion conditions are set before fusion splicing a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2 together (before the optical fibers F1, F2 come into contact with each other and fuse together). This makes it possible to fusion splice a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2 together in a short time. Furthermore, it is possible to splice a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2 together with high quality. This point will be explained below.

[0070] For example, when fusion splicing a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2, if discharge is initiated without taking into account the fiber pitch before the optical fibers F1 and F2 come into contact with each other and fuse, the amount of heat received by the discharge on the optical fibers F1 and F2 will be inappropriate, resulting in excessive or insufficient melting of the ends of the optical fibers F1 and F2 just before fusion splicing, resulting in poor splicing quality.

[0071] In contrast, if the fusion conditions are set in advance before the multiple single-core optical fibers F1 and the multiple single-core optical fibers F2 are fusion-spliced, the amount of heat received by the discharge before the optical fibers F1 and F2 come into contact with each other and fuse will be appropriate. This ensures that the melted state of the ends of the optical fibers F1 and F2 just before fusion is appropriate. Therefore, the multiple single-core optical fibers F1 and the multiple single-core optical fibers F2 can be spliced ​​with high quality.

[0072] In the optical fiber fusion splicer 10 of the first embodiment, the information representing the relationship between the fiber pitch and the fusion conditions stored in the storage unit 23 may be, for example, an approximate formula representing the relationship between the fiber pitch and the discharge intensity (current value, voltage, power value, etc.). In this case, the fusion condition processing unit 22 can set the fusion conditions by using the approximate formula to determine the set value of the discharge intensity as an input parameter, with the fiber pitch determined by the image processing unit 21. When the set value of the discharge intensity is determined using the approximate formula, the fusion conditions can be set with higher accuracy than when the set value of the discharge intensity is determined using a table. In other words, the optical fibers F1 and F2 can be fusion spliced ​​under more appropriate fusion conditions.

[0073] Second Embodiment Next, an optical fiber fusion splicer according to a second embodiment of the present invention will be described mainly with reference to Figures 11 and 12. In the following description, components common to those already described will be assigned the same reference numerals, and duplicated description will be omitted.

[0074] The optical fiber fusion splicer 10A of the second embodiment shown in FIG. 11 further includes a stage driving circuit 25 in addition to the same configuration as that of the first embodiment (movable stages 11L, 11R, fiber holders 12L, 12R, groove forming unit 13, fiber clamps 14L, 14R, discharge electrodes 15A, 15B, lighting unit 16, lens 17, camera 18, image processing unit 21, fusion condition processing unit 22, memory unit 23, and high-voltage generating circuit 24). The stage driving circuit 25 is a circuit that drives the movable stages 11L and 11R and controls the movement of the movable stages 11L and 11R based on the fusion conditions output from the fusion condition processing unit 22.

[0075] In the optical fiber fusion splicer 10A of the second embodiment, similarly to the first embodiment, information representing the relationship between fiber pitch and fusion conditions is stored in the storage unit 23. In the second embodiment, the information representing the relationship between fiber pitch and fusion conditions is table TB2 that associates fiber pitch with fusion conditions, as shown in Fig. 12. In this table TB2, different fusion conditions are associated with each fiber pitch.

[0076] In table TB2 shown in FIG. 12 , the fusion conditions include multiple elements (elements involved in fusion splicing), such as discharge intensity, discharge time, pre-discharge time, and cleave angle tolerance. The discharge intensity is the current value, voltage value, power value, etc., described in the first embodiment. The discharge time is the time required for discharge between the pair of discharge electrodes 15 when fusion splicing the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2. The pre-discharge time is the time required from the start of discharge for fusion splicing the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 to the time when the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 are butted against each other. The cleave angle tolerance is the tolerance range for the cleave angle at the end faces of the glass portions G1 and G2 of the optical fibers F1 and F2 that are butted against each other during fusion splicing. If the cleave angles at the end faces of the glass portions G1 and G2 are outside the tolerance range, poor connection of the optical fibers F1 and F2 is likely to occur, and therefore fusion splicing is not recommended. The fusion conditions may include, for example, a set value of the fiber gap, which is a set value of the distance (gap) between the plurality of single-core optical fibers F1 and the plurality of single-core optical fibers F2 immediately before the start of fusion splicing (discharge).

[0077] Furthermore, the fusion conditions in table TB2 shown in Fig. 12 may include factors that are not involved in the fusion splicing of the optical fibers F1, F2. The "factors that are not involved in the fusion splicing" included in the fusion conditions may be, for example, the fiber pitch or the types of the optical fibers F1, F2 corresponding to the fiber pitch, or the allowable value of the splicing loss after the optical fibers F1, F2 are fusion spliced, or the allowable value of the axial misalignment of the fusion-spliced ​​single-core optical fibers F1, F2.

[0078] Similar to table TB1 in the first embodiment, table TB2 shown in FIG. 12 can be created based on the results of preliminary experiments or the like to investigate the optimal fusion conditions (especially the "factors involved in fusion splicing") for multiple types of fiber pitches that are expected to be actually used.

[0079] The fusion condition processing unit 22 sets the fusion conditions by reading out the fusion conditions corresponding to the fiber pitch determined by the image processing unit 21 from table TB2 shown in Fig. 12. For example, if the fiber pitch determined by the image processing unit 21 is "fiber pitch A," the fusion condition processing unit 22 reads out "fusion condition 1" from table TB2 shown in Fig. 12. The elements of the fusion conditions read out by the fusion condition processing unit 22 from table TB2 shown in Fig. 12 may be all of the elements included in the fusion conditions, or only some of the multiple elements included in the fusion conditions.

[0080] The fusion condition processing unit 22 may set optimal fusion conditions by calculating the fusion conditions. For example, a calculation formula using environmental factors such as temperature, air pressure, and humidity as parameters in addition to the fiber pitch may be determined in advance by experiment, and the optimal fusion conditions may be calculated and set using the calculation formula when actually performing fusion splicing.

[0081] The fusion condition processing unit 22 outputs the read elements of the fusion conditions to the high voltage generating circuit 24 and the stage driving circuit 25 as appropriate. Specifically, among the elements of the fusion conditions, the discharge intensity and the discharge time are output to the high-voltage generation circuit 24. The high-voltage generation circuit 24 generates a discharge between the pair of discharge electrodes 15 in accordance with the discharge intensity and the discharge time output from the fusion condition processing unit 22. Among the elements of the fusion conditions, the set values ​​of the pre-discharge time and the fiber gap are output to the stage driving circuit 25. The stage driving circuit 25 moves the movable stages 11L and 11R in accordance with the set values ​​of the pre-discharge time and the fiber gap output from the fusion condition processing unit 22.

[0082] When the fusion conditions read by the fusion condition processing unit 22 include a cut angle tolerance, the image processing unit 21 may previously determine the cut angles of the end faces of the glass parts G1, G2 of the optical fibers F1, F2 based on the images acquired from the camera 18. This allows the fusion condition processing unit 22 to determine whether the determined cut angles are within the range of the cut angle tolerance. If the fusion condition processing unit 22 determines that the determined cut angle is within the cut angle tolerance range, the fusion condition processing unit 22 outputs a signal to start or continue the fusion splicing of the optical fibers F1 and F2, or a signal to notify the operator operating the optical fiber fusion splicer 10A of information permitting the fusion splicing of the optical fibers F1 and F2. On the other hand, if the fusion condition processing unit 22 determines that the determined cut angle is not within the cut angle tolerance range, the fusion condition processing unit 22 outputs a signal to stop the fusion splicing of the optical fibers F1 and F2, or a signal to notify the operator of information that the fusion splicing of the optical fibers F1 and F2 should be stopped.

[0083] The elements of the fusion conditions read by the fusion condition processing unit 22 (especially the "elements not involved in fusion splicing") may be output to a display unit (not shown) that displays information such as images. In this case, various information about the optical fibers F1 and F2 to be fusion spliced ​​(e.g., the types of optical fibers F1 and F2, the allowable splice loss, the allowable axial misalignment, etc.) is displayed on the display unit, allowing the operator operating the optical fiber fusion splicer 10A to easily check the information. This enables the fusion splicing of the optical fibers F1 and F2 to be performed efficiently.

[0084] The method of fusion splicing optical fibers using the optical fiber fusion splicer 10A of the second embodiment is generally similar to that of the first embodiment. However, in the fusion splicing method of the second embodiment, the fusion condition processing unit 22 reads out the fusion conditions corresponding to the determined fiber pitch from the table TB2 stored in the memory unit 23, and then outputs various elements of the read out fusion conditions to the high voltage generating circuit 24, the stage driving circuit 25, the display unit, etc. as appropriate.

[0085] For example, if the fusion conditions output from the fusion condition processing unit 22 include discharge intensity and discharge time, the high voltage generation circuit 24 generates a discharge between the pair of discharge electrodes 15 at a predetermined discharge intensity for a predetermined time in accordance with the discharge intensity and discharge time. If the fusion conditions output from the fusion condition processing unit 22 include a pre-discharge time, the stage driving circuit 25 moves the movable stages 11L, 11R at a predetermined timing according to the pre-discharge time to butt the glass parts G1 of the multiple single-core optical fibers F1 against the glass parts G2 of the multiple single-core optical fibers F2.

[0086] If the fusion conditions output from the fusion condition processing unit 22 include a cut angle tolerance, the fusion condition processing unit 22 compares the cut angle of the end faces of the glass parts G1 and G2 determined in the image processing unit 21 with the cut angle tolerance, and determines whether to start or stop the fusion splicing work of the optical fibers F1 and F2. If the fusion conditions output from the fusion condition processing unit 22 include a fiber gap setting value, the stage driving circuit 25 moves the movable stages 11L, 11R according to the fiber gap setting value before the start of discharge to adjust the spacing between the glass parts G1 of the multiple single-core optical fibers F1 and the glass parts G2 of the multiple single-core optical fibers F2.

[0087] According to the optical fiber fusion splicer 10A of the second embodiment and the method for fusion splicing optical fibers using the optical fiber fusion splicer 10A, the same effects as those of the first embodiment can be achieved. Furthermore, according to the second embodiment, the fusion conditions corresponding to the fiber pitch include multiple factors such as discharge intensity, discharge time, pre-discharge time, and cleave angle tolerance. This makes it possible to fusion-splice a plurality of single-core optical fibers F1 and a plurality of single-core optical fibers F2 under more appropriate fusion conditions. This makes it possible to further reduce the splice loss of the optical fibers F1 and F2 after fusion splicing.

[0088] Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0089] In the optical fiber fusion splicer and fusion splicing method of the present invention, the image processing unit 21 may determine the number of optical fibers F1, F2 (glass portions G1, G2) arranged in the front-rear direction Y based on the image, in addition to calculating the fiber pitch. Furthermore, the fusion condition processing unit 22 may set fusion conditions corresponding to the calculated fiber pitch and the determined number of optical fibers F1, F2. Specifically, the fusion condition processing unit 22 may derive the fusion conditions based on information indicating the relationship between the fiber pitch, the number of optical fibers F1, F2, and the fusion conditions.

[0090] The information representing the relationship between the fiber pitch, the number of optical fibers F1, F2, and the fusion conditions may be, for example, table TB3 shown in FIG. 13. Table TB3 shown in FIG. 13 may be stored in the storage unit 23, similar to tables TB1 and TB2 shown in FIGS. 8 and 12. Table TB3 shown in FIG. 13 corresponds to fusion conditions that take into account both the fiber pitch and the number of optical fibers F1, F2. That is, individual fusion conditions are defined according to combinations of the number of optical fibers F1, F2 and multiple types of fiber pitch. However, when the number of optical fibers F1, F2 is one, there is no fiber pitch, and therefore only one corresponding fusion condition is available. Table TB3 shown in FIG. 13 uses the same current value (discharge intensity) as in the first embodiment as the fusion condition, but the fusion conditions shown in table TB3 are not limited to the current value. For example, fusion conditions including multiple elements may be used, as in the second embodiment.

[0091] When the fusion conditions are set taking into consideration both the fiber pitch and the number of optical fibers F1 and F2, as illustrated in Figure 13, even if not only the fiber pitch but also the number of optical fibers F1 and F2 changes, multiple single-core optical fibers F1 and multiple single-core optical fibers F2 can be fusion-spliced ​​under optimal fusion conditions.

[0092] In the optical fiber fusion splicer and fusion splicing method of the present invention, the image processing unit 21 may determine the diameters of the optical fibers F1 and F2 (glass portions G1 and G2) based on the images, in addition to calculating the fiber pitch. The fusion condition processing unit 22 may set fusion conditions corresponding to the determined fiber pitch and diameters of the optical fibers F1 and F2. Specifically, the fusion condition processing unit 22 may derive the fusion conditions based on information indicating the relationship between the fiber pitch and diameters of the optical fibers F1 and F2 and the fusion conditions.

[0093] That is, the image processing unit 21 determines the diameter of at least one of the plurality of single-core optical fibers F1 and the diameter of at least one of the plurality of single-core optical fibers F2 based on the image. In other words, the image processing unit 21 determines the diameters of both the optical fibers F1 and F2. The fusion condition processing unit 22 selects or calculates and sets fusion conditions corresponding to the fiber pitch of the plurality of single-core optical fibers F1, the fiber pitch of the plurality of single-core optical fibers F2, the diameters of the plurality of single-core optical fibers F1, and the diameters of the plurality of single-core optical fibers F2.

[0094] Furthermore, as a first modification, the image processing unit 21 may determine the diameter of at least one of the plurality of single-core optical fibers F1 based on the image. In this case, the fusion condition processing unit 22 selects or calculates the fusion conditions corresponding to the fiber pitches of the plurality of single-core optical fibers F1 and the diameters of the plurality of single-core optical fibers F1.

[0095] As a second modification, the image processing unit 21 may determine the diameter of at least one of the plurality of single-core optical fibers F2 based on the image. In this case, the fusion condition processing unit 22 selects or calculates the fusion conditions corresponding to the fiber pitches of the plurality of single-core optical fibers F2 and the diameters of the plurality of single-core optical fibers F2.

[0096] The information representing the relationship between the fiber pitch and the diameters of the optical fibers F1 and F2 and the fusion conditions may be, for example, table TB4 shown in FIG. 14. Table TB4 of FIG. 14 may be stored in the storage unit 23. Table TB4 shown in FIG. 14 corresponds to fusion conditions that take into account both the fiber pitch and the diameters of the optical fibers F1 and F2. That is, individual fusion conditions are defined according to combinations of each diameter of the optical fibers F1 and F2 and multiple types of fiber pitch. Table TB4 shown in FIG. 14 uses the same current value as in the first embodiment as the fusion condition, but the fusion condition of the present invention is not limited to the current value. For example, fusion conditions including multiple elements as in the second embodiment may be used.

[0097] When the fusion conditions are set taking into consideration both the fiber pitch and the diameters of the optical fibers F1 and F2, as illustrated in Figure 14, multiple single-core optical fibers F1 and multiple single-core optical fibers F2 can be fusion-spliced ​​under optimal fusion conditions even if not only the fiber pitch but also the diameters of the optical fibers F1 and F2 change.

[0098] In the optical fiber fusion splicer and fusion splicing method of the present invention, the fusion conditions may be set taking into consideration three factors, for example, the fiber pitch, the number of optical fibers F1 and F2, and the diameters of the optical fibers F1 and F2.

[0099] In the optical fiber fusion splicing method of the present invention, the configuration for determining the fiber pitch and the diameter of the optical fibers F1 and F2 based on an image, or for determining the number of optical fibers F1 and F2, and the configuration for setting the fusion conditions corresponding to the determined fiber pitch and diameter and the determined number, are not limited to the image processing unit 21 or the fusion condition processing unit 22, and may be selected arbitrarily.

[0100] Some of the functions of the optical fiber fusion splicer of the present invention may be realized by, for example, a condition setting device. The condition setting device includes an acquisition unit that acquires an image including a plurality of single-core optical fibers F1, F2, a calculation unit that calculates the fiber pitch based on the image, and a processing unit that obtains fusion conditions according to the calculation results. The acquisition unit and the calculation unit may be realized by, for example, the image processing unit 21 shown in FIGS. 5 and 11. The processing unit may be realized by, for example, the fusion condition processing unit 22 shown in FIGS. 5 and 11. As exemplified in FIGS. 5 and 11, a condition setting device 30 may be configured to include the functions of the image processing unit 21 and the fusion condition processing unit 22. The condition setting device 30 is, for example, a computer equipped with electric circuits and electronic circuits. [Explanation of symbols]

[0101] 10, 10A... optical fiber fusion splicer, 11, 11L, 11R... movable stage, 13... groove forming unit, 15, 15A, 15B... discharge electrode, 15AE, 15BE... electrode tip, 16... lighting unit, 17... lens, 18... camera, 21... image processing unit, 22... fusion condition processing unit, 24... high voltage generating circuit, 30... condition setting device, F1, F2... optical fiber (single-core optical fiber), G1, G2... glass unit, MF1... first multi-core optical fiber, MF2... second multi-core optical fiber

Claims

1. An optical fiber fusion splicer, comprising: a replaceable groove forming unit having a plurality of first positioning grooves for arranging a plurality of first single-core optical fibers, each having a plurality of first glass portions, at equal intervals, which constitute a first multi-core optical fiber, and a plurality of second positioning grooves for arranging a plurality of second single-core optical fibers, each having a plurality of second glass portions, at equal intervals, which constitute a second multi-core optical fiber; an illumination unit that irradiates light onto the plurality of first single-core optical fibers and the plurality of second single-core optical fibers disposed in the groove forming unit; a lens that condenses the light that passes through the plurality of first glass portions, peripheral regions of the plurality of first glass portions, the plurality of second glass portions, and peripheral regions of the plurality of second glass portions; a camera that captures the image formed by the lens; a pair of discharge electrodes that heat and melt the first glass portions of the first single-core optical fibers and the second glass portions of the second single-core optical fibers arranged in the groove forming unit by discharge; a high voltage generating circuit that generates a discharge between the pair of discharge electrodes; a movable stage that moves the plurality of first single-core optical fibers in the longitudinal direction of the first multi-core optical fiber and moves the plurality of second single-core optical fibers in the longitudinal direction of the second multi-core optical fiber; Based on the image captured by the camera, a distance between two of the first single-core optical fibers located at both ends of the first multi-core optical fiber in the front-rear direction in which the plurality of first single-core optical fibers are arranged, and a fiber pitch of the plurality of first single-core optical fibers based on the number of the plurality of first single-core optical fibers; an image processing unit that calculates at least one of a distance between two of the second single-core optical fibers located at both ends of the second multi-core optical fiber in a front-rear direction in which the plurality of second single-core optical fibers are arranged, and a fiber pitch of the plurality of second single-core optical fibers based on the number of the plurality of second single-core optical fibers; a fusion condition processing unit that selects or calculates a fusion condition corresponding to at least one of the obtained fiber pitches of the plurality of first single-core optical fibers and the obtained fiber pitches of the plurality of second single-core optical fibers; Equipped with the fiber pitch of the plurality of first single-core optical fibers is found by dividing the distance between two of the first single-core optical fibers located at both ends of the first multi-core optical fiber by the number of the plurality of first single-core optical fibers minus 1; An optical fiber fusion splicer in which the fiber pitch of the plurality of second single-core optical fibers is determined by dividing the distance between the two second single-core optical fibers located at both ends of the second multi-core optical fiber by the number of the plurality of second single-core optical fibers minus 1.

2. the image processing unit determines the number of the plurality of first single-core optical fibers and the number of the plurality of second single-core optical fibers based on the image; the fusion condition processing unit selects or calculates and sets the fusion conditions corresponding to the obtained fiber pitches of the plurality of first single-core optical fibers, the obtained fiber pitches of the plurality of second single-core optical fibers, the number of the plurality of first single-core optical fibers, and the number of the plurality of second single-core optical fibers; 2. The optical fiber fusion splicer according to claim 1.

3. the image processing unit determines a diameter of at least one of the plurality of first single-core optical fibers or a diameter of at least one of the plurality of second single-core optical fibers based on the image; the fusion condition processing unit selects or calculates to set the fusion conditions corresponding to the obtained fiber pitches of the plurality of first single-core optical fibers and diameters of the plurality of first single-core optical fibers, or selects or calculates to set the fusion conditions corresponding to the obtained fiber pitches of the plurality of second single-core optical fibers and diameters of the plurality of second single-core optical fibers; 2. The optical fiber fusion splicer according to claim 1.

4. the image processing unit determines a diameter of at least one of the plurality of first single-core optical fibers and a diameter of at least one of the plurality of second single-core optical fibers based on the image; the fusion condition processing unit selects or calculates and sets the fusion conditions corresponding to the obtained fiber pitches of the plurality of first single-core optical fibers, the obtained fiber pitches of the plurality of second single-core optical fibers, the diameters of the plurality of first single-core optical fibers, and the diameters of the plurality of second single-core optical fibers; 2. The optical fiber fusion splicer according to claim 1.

5. An optical fiber fusion splicing method for fusion-splicing a first multi-core optical fiber and a second multi-core optical fiber using an optical fiber fusion splicer, comprising: The optical fiber fusion splicer includes: a replaceable groove forming unit having a plurality of first positioning grooves for arranging a plurality of first single-core optical fibers, each having a plurality of first glass portions, at equal intervals, which constitute the first multi-core optical fiber, and a plurality of second positioning grooves for arranging a plurality of second single-core optical fibers, each having a plurality of second glass portions, at equal intervals, which constitute the second multi-core optical fiber; an illumination unit that irradiates light onto the plurality of first single-core optical fibers and the plurality of second single-core optical fibers disposed in the groove forming unit; a lens that condenses the light that passes through the plurality of first glass portions, peripheral regions of the plurality of first glass portions, the plurality of second glass portions, and peripheral regions of the plurality of second glass portions; a camera that captures the image formed by the lens; a pair of discharge electrodes that heat and melt the first glass portions of the first single-core optical fibers and the second glass portions of the second single-core optical fibers arranged in the groove forming unit by discharge; a high voltage generating circuit that generates a discharge between the pair of discharge electrodes; a movable stage that moves the plurality of first single-core optical fibers in the longitudinal direction of the first multi-core optical fiber and moves the plurality of second single-core optical fibers in the longitudinal direction of the second multi-core optical fiber; Equipped with The fusion splicing method includes: Based on the image captured by the camera, a distance between two of the first single-core optical fibers located at both ends of the first multi-core optical fiber in the front-rear direction in which the plurality of first single-core optical fibers are arranged, and a fiber pitch of the plurality of first single-core optical fibers based on the number of the plurality of first single-core optical fibers; In the front-rear direction in which the plurality of second single-core optical fibers are arranged, a distance between two of the second single-core optical fibers located at both ends of the second multi-core optical fiber and a fiber pitch of the plurality of second single-core optical fibers based on the number of the plurality of second single-core optical fibers are obtained; setting, by selection or calculation, a fusion condition corresponding to at least one of the obtained fiber pitches of the plurality of first single-core optical fibers and the obtained fiber pitches of the plurality of second single-core optical fibers; the fiber pitch of the plurality of first single-core optical fibers is found by dividing the distance between two of the first single-core optical fibers located at both ends of the first multi-core optical fiber by the number of the plurality of first single-core optical fibers minus 1; The fiber pitch of the plurality of second single-core optical fibers is obtained by dividing the distance between the two second single-core optical fibers located at both ends of the second multi-core optical fiber by the number of the plurality of second single-core optical fibers minus 1. A method for fusion splicing optical fibers.

6. setting the fusion conditions before fusion-splicing the first multi-core optical fiber and the second multi-core optical fiber; 6. The method for fusion splicing optical fibers according to claim 5.

7. determining the number of the plurality of first single-core optical fibers and the number of the plurality of second single-core optical fibers based on the image; setting, by selection or calculation, the fusion conditions corresponding to the determined fiber pitches of the plurality of first single-core optical fibers, the determined fiber pitches of the plurality of second single-core optical fibers, the number of the plurality of first single-core optical fibers, and the number of the plurality of second single-core optical fibers; 7. The method for fusion splicing optical fibers according to claim 5 or 6.

8. determining a diameter of at least one of the plurality of first single-core optical fibers or a diameter of at least one of the plurality of second single-core optical fibers based on the image; setting, by selection or calculation, the fusion conditions corresponding to the obtained fiber pitches of the plurality of first single-core optical fibers and the diameters of the plurality of first single-core optical fibers, or setting, by selection or calculation, the fusion conditions corresponding to the obtained fiber pitches of the plurality of second single-core optical fibers and the diameters of the plurality of second single-core optical fibers; 7. The method for fusion splicing optical fibers according to claim 5 or 6.

9. determining a diameter of at least one of the plurality of first single-core optical fibers and a diameter of at least one of the plurality of second single-core optical fibers based on the image; setting the fusion conditions by selection or calculation corresponding to the obtained fiber pitches of the plurality of first single-core optical fibers, the obtained fiber pitches of the plurality of second single-core optical fibers, the diameters of the plurality of first single-core optical fibers, and the diameters of the plurality of second single-core optical fibers; 7. The method for fusion splicing optical fibers according to claim 5 or 6.

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