Fusion splicer for optical fiber and method for fusion-splicing optical fiber

Abstract

To provide a fusion splicer for optical fiber capable of improving the quality of fusion splicing and a method for fusion-splicing an optical fiber.SOLUTION: A fusion splicer for optical fiber includes an image acquisition part, a condition setting part, and a fusion splicing part. The image acquisition part acquires an image including end surfaces of first and second optical fibers in a state that the end surfaces of the first and second optical fibers to be connected are disposed opposite. The condition setting part grasps states of the respective end surfaces based on the image and sets a connection condition in accordance with the states of the respective end surfaces. The fusion splicing part fusion-splices the first and second optical fibers each other by discharge between a pair of electrode bars according to the connection condition set by the condition setting part. The connection condition includes at least one of a position of each end surface before discharge starts, a gap between the respective end surfaces before discharge starts, a preparatory discharge time, a real discharge time, a push-in amount after the respective end surfaces come into contact with each other, and an amount of return after the respective end surfaces are pushed in.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical fiber fusion splicer and a method for fusion splicing optical fibers. This application claims priority to Japanese Patent Application No. 2020-022287, filed February 13, 2020, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] Patent Document 1 discloses technology related to an optical fiber fusion splicer. The fusion splicer described in this document is a device for fusion splicing two optical fibers together. This device includes an imaging means, an information extraction means, a storage means, a selection means, a discharge means, and a control means. The imaging means obtains a transmitted light image of the ends of the two optical fibers using transmitted light. The information extraction means extracts end face information of each of the two optical fibers using the brightness distribution of the transmitted light image. The storage means stores a plurality of splicing conditions in advance. The selection means selects a splicing condition corresponding to the end face information from the plurality of splicing conditions. The discharge means generates an arc discharge that is irradiated onto the splicing end faces of the two optical fibers. The control means controls the amount of discharge energy of the arc discharge in accordance with the splicing condition selected by the selection means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-31439 Summary of the Invention

[0004] An optical fiber fusion splicer according to one embodiment of the present disclosure includes an image acquisition unit, a condition setting unit, and a fusion splicing unit. The image acquisition unit acquires images including the end faces of the first and second optical fibers to be spliced, with the end faces of the first and second optical fibers arranged opposite each other. The condition setting unit determines the state of each end face based on the images and sets splicing conditions according to the state of each end face. The fusion splicing unit fusion-splices the first and second optical fibers to each other by discharging between a pair of electrode rods in accordance with the splicing conditions set by the condition setting unit. The splicing conditions include at least one of the positions of the end faces before the start of discharge, the distance between the end faces before the start of discharge, a pre-discharge time, a main discharge time, the amount of push-in after the end faces contact each other, and the amount of pull-back after the end faces are pushed together.

[0005] A method for fusion splicing optical fibers according to one embodiment of the present disclosure includes an image acquiring step, a condition setting step, and a fusion splicing step. The image acquiring step acquires an image including the end faces of the first and second optical fibers to be spliced, with the end faces of the first and second optical fibers positioned opposite each other. The condition setting step determines the state of each end face based on the image and sets splicing conditions according to the state of each end face. The fusion splicing step fusion splices the first and second optical fibers to each other by discharge between a pair of electrode rods in accordance with the splicing conditions set in the condition setting step. The splicing conditions include at least one of the positions of the end faces before the start of discharge, the distance between the end faces before the start of discharge, a pre-discharge time, a main discharge time, the amount of push-in after the end faces contact each other, and the amount of pull-back after the end faces are pushed together. [Brief explanation of the drawings]

[0006] [Figure 1] Fig. 1 is a perspective view showing the appearance of an optical fiber fusion splicer according to one embodiment, with the windshield cover closed. [Figure 2] Fig. 2 is a perspective view showing the appearance of an optical fiber fusion splicer according to one embodiment, with the windshield cover open to reveal the internal structure of the fusion splicer. [Figure 3] FIG. 3 is a functional block diagram showing the configuration of an internal system provided in the fusion splicer. [Figure 4] FIG. 4 is a block diagram showing an example of the hardware configuration of the fusion control unit. [Figure 5] FIG. 5 is a diagram illustrating the operation of the fusion splicer of one embodiment. [Figure 6] FIG. 6 is a diagram illustrating the operation of the fusion splicer of one embodiment. [Figure 7] FIG. 7 is a diagram illustrating the operation of the fusion splicer of one embodiment. [Figure 8] FIG. 8 is a view of the end face of the optical fiber as viewed from the optical axis direction. [Figure 9] FIG. 9 is a diagram schematically showing an image obtained by a camera capturing an image from a certain direction. [Figure 10] FIG. 10 is a view of the end face of the optical fiber as viewed from the optical axis direction. [Figure 11] FIG. 11 is a diagram schematically showing an image obtained by a camera capturing an image from a certain direction. [Figure 12] FIG. 12 is a view of the end face of the optical fiber as viewed from the optical axis direction. [Figure 13] FIG. 13 is a diagram schematically showing an image obtained by a camera capturing an image from another direction. [Figure 14] FIG. 14 is a diagram schematically showing the positions of the end faces before the start of discharge. [Figure 15] FIG. 15 is a flowchart illustrating a fusion splicing method according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] When fusion splicing optical fibers, splicing conditions such as discharge power and the position of the tip of the optical fiber are set. These splicing conditions affect the quality of the fusion splice and the increase in transmission loss (splicing loss) at the fused portion. The optimal splicing conditions change depending on the condition of the end face of the optical fiber.

[0008] [Effects of this disclosure] According to the present disclosure, it is possible to provide an optical fiber fusion splicer and a method for fusion splicing optical fibers that can improve the quality of fusion splicing.

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be described. An optical fiber fusion splicer according to one embodiment includes an image acquisition unit, a condition setting unit, and a fusion splicing unit. The image acquisition unit acquires images including the end faces of the first and second optical fibers to be spliced, with the end faces of the first and second optical fibers positioned opposite each other. The condition setting unit determines the state of each end face based on the images and sets splicing conditions according to the state of each end face. The fusion splicing unit fusion-splices the first and second optical fibers to each other by discharging between a pair of electrode rods in accordance with the splicing conditions set by the condition setting unit. The splicing conditions include at least one of the positions of the end faces before the start of discharge, the distance between the end faces before the start of discharge, the pre-discharge time, the main discharge time, the amount of push-in after the end faces contact each other, and the amount of pull-back after the end faces have been pushed together. Here, the term "image including the end faces" is not limited to an image directly capturing the end faces, but also includes an image captured from the side of a portion of the optical fiber including the end face, in which the end faces are not directly visible in the image.

[0010] According to one embodiment, a method for fusion splicing optical fibers includes an image acquiring step, a condition setting step, and a fusion splicing step. The image acquiring step acquires an image including the end faces of the first and second optical fibers to be spliced, with the end faces of the first and second optical fibers positioned opposite each other. The condition setting step determines the state of each end face based on the image and sets splicing conditions according to the state of each end face. The fusion splicing step fusion splices the first and second optical fibers to each other by discharging between a pair of electrode rods in accordance with the splicing conditions set in the condition setting step. The splicing conditions include at least one of the positions of the end faces before the start of discharge, the distance between the end faces before the start of discharge, a pre-discharge time, a main discharge time, the amount of push-in after the end faces contact each other, and the amount of pull-back after the end faces are pushed together. Here, the "image including the end faces" is not limited to an image directly capturing the end faces, but also includes an image captured from the side of a portion of the optical fiber including the end face, in which the end faces are not directly visible in the image.

[0011] In these fusion splicers and fusion splicing methods, the splicing conditions set according to the state of each end face include at least one of the following: the position of each end face before the start of discharge, the distance between the end faces before the start of discharge, the pre-discharge time, the main discharge time, the amount of push-in after the end faces contact each other, and the amount of pull-back after the end faces are pushed together. In this case, more suitable splicing conditions can be set according to the state of the optical fiber end faces, compared to controlling only the amount of discharge energy (discharge power), as in the device described in Patent Document 1, for example. This makes it possible to further improve the quality of the fusion splice and reduce splice loss.

[0012] In the optical fiber fusion splicer and the method for fusion splicing optical fibers, the splicing conditions may include at least three of the position, the interval, the pre-discharge time, the main discharge time, the push-in amount, and the pull-back amount, thereby further improving the quality of the fusion splice and further reducing splice loss.

[0013] In the above-described optical fiber fusion splicer and method for fusion splicing optical fibers, the positions may be the positions of the end faces relative to a line connecting the central axes of the pair of electrode rods at the start of preliminary discharge. The preliminary discharge time may be the time from the start of arc discharge to the start of relative movement of the first and second optical fibers to bring the end faces into contact. The main discharge time may be the time from the end faces coming into contact to the end of stopping application of voltage to the pair of electrode rods. The push-in amount may be the distance traveled when the first and second optical fibers are further moved relative to each other in the same direction during discharge after the end faces have come into contact. The pull-back amount may be the distance traveled when the first and second optical fibers are further pushed in after the end faces have come into contact and then moved relative to each other in a direction that moves the end faces away from each other during fusion splicing.

[0014] In the optical fiber fusion splicer and the method for fusion splicing optical fibers described above, the state of each end face may include the position and depth of a depression in each end face, the position and height of a protrusion at the edge of each end face, and the direction and angle of inclination of each end face.

[0015] [Details of the embodiments of the present disclosure] Specific examples of the optical fiber fusion splicer and method of fusion splicing optical fibers according to the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, identical elements in the drawings will be given the same reference numerals, and duplicate explanations will be omitted.

[0016] 1 and 2 are perspective views showing the exterior of an optical fiber fusion splicer (hereinafter simply referred to as a fusion splicer) 10 according to this embodiment. FIG. 1 shows the exterior with the windshield cover closed. FIG. 2 shows the exterior with the windshield cover open, revealing the internal structure of the fusion splicer 10. The fusion splicer 10 is a device for fusion-splicing optical fibers together by electric discharge. As shown in FIGS. 1 and 2, the fusion splicer 10 includes a box-shaped housing 2. An upper portion of the housing 2 is provided with a fusion splicing unit 3 for fusing the optical fibers together, and a heater 4. The heater 4 heats and shrinks a fiber reinforcement sleeve that is placed over the fused portion of the optical fiber. The fusion splicer 10 also includes a monitor 5, a windshield cover 6, a power switch 7, and a splicing start switch 8. The monitor 5 displays various information, including, for example, the status of the fusion splicing of the optical fibers captured by a camera located inside the housing 2. The windshield cover 6 prevents wind from entering the fusion splicing unit 3. The power switch 7 is a push button for turning on / off the power of the fusion splicer 10 in response to a user's operation. The splicing start switch 8 is a push button for starting the operation of fusing optical fibers together in response to a user's operation.

[0017] As shown in Figure 2, the fusion splicing unit 3 has a pair of fiber positioning units 3a, a pair of electrode rods 3b, and a holder mounting unit on which a pair of optical fiber holders 3c can be mounted. Each optical fiber to be fusion spliced is held and fixed in an optical fiber holder 3c, and the optical fiber holders 3c are mounted and fixed on the holder mounting units. The fiber positioning unit 3a is disposed between the pair of optical fiber holders 3c and positions the tip end of the optical fiber held in each of the optical fiber holders 3c. The electrode rod 3b is disposed between the pair of fiber positioning units 3a and softens the tip end of each optical fiber by arc discharge.

[0018] Fig. 3 is a functional block diagram showing the configuration of an internal system provided in fusion splicer 10. As shown in Fig. 3, fusion splicer 10 includes, in addition to the above-described fusion splicing unit 3, a fusion control unit 12, a camera 9, and a monitor 5. Camera 9 is an example of an image acquisition unit in this embodiment. Camera 9 is disposed inside housing 2. With the end faces of two optical fibers to be spliced positioned opposite each other, camera 9 acquires an image including each end face and generates image data.

[0019] Fig. 4 is a block diagram showing an example of the hardware configuration of the fusion control unit 12. As shown in Fig. 4, the fusion control unit 12 may be configured as a computer including a CPU 12a, a RAM 12b, and a ROM 12c. The fusion control unit 12 reads and executes a program pre-stored in the ROM 12c, and reads and writes data from and to the RAM 12b and ROM 12c under the control of the CPU 12a. This allows the fusion control unit 12 to realize each function of the fusion control unit 12. The operating status of the fusion control unit 12 is always displayed on the monitor 5 while the fusion splicer 10 is in operation. The fusion control unit 12 is electrically connected to the connection start switch 8. The fusion control unit 12 receives an electrical signal from the connection start switch 8.

[0020] As shown in FIG. 3 , the fusion control unit 12 includes a basic control unit 13 and a condition setting unit 14. The basic control unit 13 controls the operation of the fusion splicing unit 3. In response to the user's operation of the splicing start switch 8, the basic control unit 13 controls the contact operation of the optical fiber tips and the arc discharge in the fusion splicing unit 3. The contact operation of the optical fiber tips includes the positioning of the optical fibers by the fiber positioning unit 3a, i.e., the control of the tip position of each optical fiber. The control of the arc discharge includes the control of the discharge power, discharge start timing, and discharge end timing. Various splicing conditions, such as the optical fiber tip position and discharge power, are stored in, for example, the ROM 12c. The splicing conditions are set by the condition setting unit 14. The condition setting unit 14 determines the state of each end face of the two optical fibers based on images captured by the camera 9 and sets the splicing conditions according to the state of each end face. When setting the splicing conditions, multiple splicing conditions may be prepared in advance, and one of these splicing conditions may be selected according to the state of each end face. Alternatively, connection conditions may be set by calculation from a predetermined approximate formula using specific values determined according to the state of each end face. Or, both may be combined. That is, while setting connection conditions that serve as pre-prepared references, the amount of change from the reference connection conditions may be calculated and set from a predetermined approximate formula using specific values determined according to the state of each end face.

[0021] The fusion splicer 10 of this embodiment having the above configuration operates as follows. First, as shown in FIG. 5, a user holds the optical fiber F1 (first optical fiber) and the optical fiber F2 (second optical fiber) to be spliced in the optical fiber holder 3c, respectively. Then, the optical fiber holder 3c is placed on the holder placement portion. At this time, the end face F1a of the optical fiber F1 and the end face F2a of the optical fiber F2 are positioned opposite each other. Next, the user instructs the fusion splicer 10 to start fusion splicing. This instruction is issued via the splicing start switch 8. In response to this instruction, as shown in FIG. 6, the basic control unit 13 positions the optical fibers F1 and F2 based on the positions of the end faces F1a and F2a set as the splicing conditions. Thereafter, as shown in FIG. 7, the basic control unit 13 starts an arc discharge between the pair of electrode rods 3b.

[0022] Immediately after the arc discharge begins, the end faces F1a and F2a are separated from each other. At this time, the arc discharge corresponds to a preliminary discharge for softening the end faces F1a and F2a before fusing them. When the arc discharge begins, the basic control unit 13 controls the position of the fiber positioning unit 3a to bring the end faces F1a and F2a closer to each other and bring them into contact with each other. Then, by continuing the arc discharge (main discharge), the end faces F1a and F2a further soften and are fused to each other.

[0023] Here, an example of the state of each end face F1a, F2a of two optical fibers F1, F2, which is used as a reference for setting connection conditions, will be described. FIG. 8 is a view of the end face F2a of one optical fiber F2 as viewed from the front (optical axis direction). Arrows MSX and MSY in the figure indicate the observation directions of the camera 9. That is, in this example, at least two cameras 9 are installed, and the two cameras 9 capture images of each end face F1a, F2a from directions MSX and MSY that are perpendicular to each other. The directions MSX and MSY intersect with the optical axis directions of the optical fibers F1, F2, and in one example, are perpendicular to them. A light source 11 for illuminating the optical fibers F1, F2 is arranged at a position opposite the camera 9 across the optical fibers F1, F2.

[0024] Now, suppose that a chip (dent) A occurs on the end face F2a at the position shown in Figure 8. Then, as shown in Figure 9, the chip A on the end face F2a clearly appears in the image PY obtained by the camera 9 capturing images from the direction MSY. The location and size (depth) of the chip A on the end face F2a can be analyzed based on two images obtained by the two cameras 9 capturing images from the directions MSX and MSY, respectively. As shown in Figure 9, in these images, the positions and shapes of the optical fibers F1 and F2 can be confirmed by the outline of at least one of the core CR and the cladding CL. In the images, the core CR appears bright due to illumination light from the light source 11, and the cladding CL appears dark due to refraction of the illumination light from the light source 11.

[0025] Fig. 10 is a view of the end face F2a of one optical fiber F2 as seen from the front (optical axis direction). Suppose that a lip B has formed on the edge of the end face F2a at the position shown in Fig. 10. Then, as shown in Fig. 11, the lip B protruding from the edge of the end face F2a clearly appears in the image PY obtained by the camera 9 capturing images from the direction MSY. The position and size (height) of the lip B on the end face F2a can be analyzed based on two images obtained by the two cameras 9 capturing images from the directions MSX and MSY, respectively.

[0026] FIG. 12 is a view of the end face F2a of one optical fiber F2 as seen from the front (optical axis direction), with the inclination of the end face F2a in the optical axis direction represented by shades of color. That is, the darker the color, the farther the area is from the opposing end face F1a, and the lighter the area, the closer the area is to the opposing end face F1a. Suppose that an inclination occurs in the direction shown in FIG. 12 in the end face F2a. Then, as shown in FIG. 13, the inclination of the end face F2a clearly appears in the image PX obtained by the camera 9 capturing an image from the direction MSX. The direction and magnitude (angle) of the inclination of the end face F2a can be analyzed based on two images obtained by the two cameras 9 capturing images from the directions MSX and MSY, respectively.

[0027] Next, the splicing conditions set according to the state of each end face F1a, F2a of the optical fibers F1, F2 will be described in detail. In this embodiment, the splicing conditions set according to the state of each end face F1a, F2a include at least one, and more preferably three or more, of the following: (1) the position of each end face F1a, F2a before the start of discharge, (2) the distance between each end face F1a, F2a before the start of discharge, (3) the pre-discharge time, (4) the main discharge time, (5) the amount of push-in after the end faces F1a, F2a come into contact with each other, and (6) the amount of pull-back after the end faces F1a, F2a have been pushed together.

[0028] (1) Positions of the end faces F1a and F2a before discharge begins The positions of the end faces F1a, F2a before the start of discharge refer to the positions X1, X2 of the end faces F1a, F2a relative to the line E (discharge central axis) connecting the central axes of the pair of electrode rods 3b at the start of preliminary discharge, as shown in Fig. 14. The distance between the discharge center and the end faces F1a, F2a changes depending on the end face positions X1, X2, thereby increasing or decreasing the amount of heat (melting amount). In addition, the time required for the end faces F1a, F2a to move until they come into contact changes depending on the end face positions X1, X2.

[0029] If the depth of the chip A shown in FIG. 9 is greater than or equal to a predetermined value (e.g., 10 μm), the end face F1a or F2a having the chip A is moved closer to the discharge central axis E, for example, compared with a predetermined end face reference position, i.e., the optimal values of the end face positions X1 and X2, which are determined in advance assuming that the end faces F1a and F2a are normal. In other words, the end face position X1 or X2 relative to the discharge central axis E is reduced. In this case, the end face position X1 or X2 is set to, for example, approximately 70% of the end face reference position. This reduces connection loss. In this case, the condition setting unit 14 calculates the end face positions X1 and X2 relative to the discharge central axis E using a predetermined formula based on the depth of the chip A obtained from the image. In addition, when either the lip B shown in FIG. 11 or the inclined end face F2a shown in FIG. 13 is present, for example, the median of the difference between the maximum value Xa and the minimum value Xb of the end face position X1 or X2 of the lip B or the inclined end face F1a or F2a is matched with a predetermined end face reference position. This reduces connection loss. In this case, the condition setting unit 14 calculates the end face position X1 or X2 using a predetermined formula based on the maximum value Xa and minimum value Xb obtained from the image.

[0030] (2) Distance between the end faces F1a and F2a before discharge begins The distance between the end faces F1a and F2a before discharge begins refers to the distance D between the end faces F1a and F2a in the state shown in FIG. 6, i.e., at the start of preliminary discharge. The time required for the end faces F1a and F2a to move until they come into contact varies depending on this distance D. When the depth of the chip A shown in FIG. 9 is equal to or greater than a predetermined value (e.g., 10 μm), connection loss can be reduced by, for example, making the distance D smaller than a predetermined reference distance between the end faces. The reference distance between the end faces is an optimal value for the distance D that is predetermined assuming that there are no abnormalities in the end faces F1a and F2a. The distance D is, for example, approximately 70% of the reference distance between the end faces. In this case, the condition setting unit 14 calculates the distance D using a predetermined formula based on the depth of the chip A obtained from the image. When either the lip B shown in FIG. 11 or the inclination of the end face F2a shown in FIG. 13 is present, for example, the median of the difference between the maximum distance Da and the minimum distance Db between the end faces F1a and F2a is made to coincide with a predetermined end face distance reference value. This reduces the connection loss. In this case, the condition setting unit 14 calculates the distance D using a predetermined formula based on the difference between the maximum distance Da and the minimum distance Db obtained from the image.

[0031] (3) Pre-discharge time The pre-discharge time refers to the time from when arc discharge begins in the state shown in FIG. 6 until the relative movement of the optical fibers F1 and F2 begins to bring the end faces F1a and F2a into contact with each other. When the depth of the chip A shown in FIG. 9 is equal to or greater than a predetermined value (e.g., 10 μm), the chip A can be made smaller (shallower) when the end faces F1a and F2a contact each other by extending the pre-discharge time beyond a predetermined reference time, thereby reducing splice loss. The reference time is the optimal length of the pre-discharge time, determined in advance assuming that there are no abnormalities in the end faces F1a and F2a. The pre-discharge time is, for example, 1.3 to 2 times the reference time. In this case, the condition setting unit 14 calculates the pre-discharge time using a predetermined formula based on the depth of the chip A obtained from the image. When either the lip B shown in FIG. 11 or the inclination of the end face F2a shown in FIG. 13 is present, the pre-discharge time is also extended beyond the predetermined reference time. This reduces the lip B or the inclination when the end faces F1a and F2a contact each other, thereby reducing splice loss. At this time, the pre-discharge time is set to, for example, 1.3 to 2 times the reference time. In this case, the condition setting unit 14 calculates the pre-discharge time using a predetermined formula based on the protrusion amount or inclination angle of the lip B obtained from the image.

[0032] (4) Main discharge time The main discharge time refers to the time from when the end faces F1a and F2a come into contact with each other until the arc discharge is terminated. In other words, the main discharge time is the time from when the end faces F1a and F2a come into contact with each other until the application of voltage to the pair of electrode rods 3b is stopped. The preliminary discharge and the main discharge are performed consecutively. If a chip A shown in FIG. 9 exists on the end face F1a or F2a, axial misalignment progresses from the chip A as a starting point during fusion splicing. Therefore, for example, by shortening the main discharge time below a predetermined reference time, the amount of axial misalignment can be reduced and splice loss can be reduced. The reference time is the optimal length of the main discharge time, determined in advance assuming that there are no abnormalities in the end faces F1a and F2a. The main discharge time is, for example, 30% to 70% of the reference time. In this case, the condition setting unit 14 calculates the main discharge time using a predetermined formula based on the depth of the chip A obtained from the image. Even when either the lip B shown in FIG. 11 or the inclination of the end face F2a shown in FIG. 13 is present, axial misalignment progresses during fusion splicing, starting from the point farthest from the end face of the other end, in other words, the outer edge that is furthest back on the end face. Therefore, for example, by shortening the main discharge time below a predetermined reference time, the amount of axial misalignment can be reduced, thereby reducing splice loss. The main discharge time is set, for example, to between 30% and 70% of the reference time. In this case, the condition setting unit 14 calculates the main discharge time using a predetermined formula based on the protrusion amount or inclination angle of the lip B obtained from the image.

[0033] (5) Amount of push-in after the end faces F1a and F2a come into contact with each other The push-in depth after the end faces F1a, F2a come into contact with each other refers to the distance the optical fibers F1, F2 are moved relative to each other from the state shown in FIG. 6 until the end faces F1a, F2a come into contact with each other, and then the optical fibers F1, F2 are further moved relative to each other in the same direction during discharge. If a chip A shown in FIG. 9 exists on the end face F1a or F2a, axial misalignment will progress from the chip A as a starting point during fusion splicing. Therefore, for example, by increasing the push-in depth beyond a predetermined reference push-in depth, the progression of axial misalignment during fusion splicing can be suppressed and splice loss can be reduced. The reference push-in depth is an optimal value of the push-in depth that is predetermined assuming that the end faces F1a, F2a are free of abnormalities. The push-in depth is, for example, 150% or more of the reference push-in depth. In this case, the condition setting unit 14 calculates the push-in depth using a predetermined formula based on the depth of the chip A obtained from the image. When either the lip B shown in FIG. 11 or the inclination of the end face F2a shown in FIG. 13 is present, the distance D varies within the end face. Therefore, for example, by making the pushing amount larger than the reference pushing amount, the effect of the in-plane variation in the distance D can be suppressed and the connection loss can be reduced. In this case, the pushing amount is set to, for example, 120% or more of the reference pushing amount. In this case, the condition setting unit 14 calculates the pushing amount using a predetermined formula based on the protrusion amount or the angle of inclination of the lip B obtained from the image. The calculated pushing amount also includes a case where the pushing amount is zero, i.e., no pushing is performed.

[0034] (6) Amount of retraction after pushing the end faces F1a and F2a together The pullback amount after pushing the end faces F1a, F2a together refers to the distance the optical fibers F1, F2 are moved relative to each other in the opposite direction, i.e., in the direction in which the end faces F1a, F2a move away from each other, after the end faces F1a, F2a are brought into contact with each other and then further pushed in during fusion splicing. If a chip A shown in FIG. 9 exists on the end face F1a or F2a, the above-mentioned pushback amount may be non-uniform within a cross section perpendicular to the central axis of the optical fibers F1, F2. Such non-uniformity may cause deformation of the core and increase splice loss. Therefore, splice loss can be reduced by, for example, pulling back more than 20% of the pushback amount. In this case, the condition setting unit 14 calculates the pullback amount using a predetermined formula based on the depth of the chip A obtained from the image. The presence of either the lip B shown in FIG. 11 or the inclination of the end face F2a shown in FIG. 13 may also result in non-uniformity within the end face. If the core becomes uneven, deformation of the core may increase connection loss. Therefore, for example, connection loss can be reduced by pulling back at least 20% of the push-in amount. In this case, the condition setting unit 14 calculates the pull-back amount using a predetermined formula based on the protrusion amount or tilt angle of lip B obtained from the image. The calculated pull-back amount also includes cases where the pull-back amount is zero, i.e., no pull-back is performed.

[0035] Furthermore, the connection conditions set according to the state of each of the end faces F1a and F2a may include the following (7) preliminary discharge power. (7) Pre-discharge power The pre-discharge power refers to the arc discharge power during the period from when arc discharge begins in the state shown in FIG. 6 until the relative movement of the optical fibers F1 and F2 begins to bring the end faces F1a and F2a into contact with each other. When the depth of the chip A shown in FIG. 9 is equal to or greater than a predetermined value (e.g., 10 μm), the pre-discharge power is increased, for example, above a predetermined reference value of the pre-discharge power. This increases the degree of softening of the end faces F1a and F2a, thereby making the chip A smaller (shallower) when they come into contact with each other and reducing splice loss. The reference value of the pre-discharge power is an optimal value of the pre-discharge power that is predetermined assuming that there are no abnormalities in the end faces F1a and F2a. In this case, the condition setting unit 14 calculates the pre-discharge power using a predetermined formula based on the depth of the chip A obtained from the image. When either the lip B shown in FIG. 11 or the inclination of the end face F2a shown in FIG. 13 is present, for example, the pre-discharge power is increased above the reference value. This reduces the lip B or the inclination when the end faces F1a and F2a come into contact with each other, thereby reducing connection loss. At this time, the pre-discharge power is set to, for example, 1.3 to 2 times the reference value. In this case, the condition setting unit 14 calculates the pre-discharge power using a predetermined formula based on the protrusion amount or inclination angle of the lip B obtained from the image.

[0036] As described above, in the operation of the fusion splicer 10 according to this embodiment, the condition of each end face F1a, F2a of the two optical fibers F1, F2 is analyzed and understood based on the respective observation images. Then, splicing conditions are set according to the condition of each end face F1a, F2a. That is, if the analysis of the condition of each end face F1a, F2a reveals that there is no abnormality in either end face F1a or F2a, predetermined reference splicing conditions are set. If the analysis of the condition of each end face F1a, F2a reveals that there is an abnormality in either or both of the end faces F1a, F2a, splicing conditions different from the predetermined reference splicing conditions are set according to the condition of the end face(s) with the abnormality.

[0037] 15 is a flowchart showing a fusion splicing method according to this embodiment. This fusion splicing method can be suitably implemented using the fusion splicer 10 described above. First, in image acquisition step S1, an image including each of the end faces F1a, F2a of the optical fibers F1, F2 to be spliced is acquired by camera 9 in a state in which the end faces F1a, F2a are arranged opposite each other (see FIG. 6). Next, in condition setting step S2, the condition of each of the end faces F1a, F2a, such as the presence and size of at least one of a chip A, a lip B, and an end face inclination, is determined based on the acquired image, and splicing conditions are then set according to the condition of each of the end faces F1a, F2a. As described above, the splicing conditions set according to the state of the end faces F1a, F2a include at least one, and more preferably three or more, of the following: (1) the position of each end face F1a, F2a before the start of discharge, (2) the distance between each end face F1a, F2a before the start of discharge, (3) pre-discharge time, (4) main discharge time, (5) the amount of push-in after the end faces F1a, F2a contact each other, and (6) the amount of pull-back after the end faces F1a, F2a are pushed together. The splicing conditions may further include the above-mentioned (7) pre-discharge power. Next, in fusion splicing step S3, the end faces F1a, F2a are fusion spliced to each other by arc discharge between the pair of electrode rods 3b in accordance with the splicing conditions set in step S2.

[0038] As described above, in the fusion splicing method according to this embodiment, the condition of each end face F1a, F2a of two optical fibers F1, F2 is analyzed and understood based on the respective observation images. Then, splicing conditions are set according to the condition of each end face F1a, F2a. That is, if the analysis of the condition of each end face F1a, F2a shows that there is no abnormality in either end face F1a or F2a, predetermined reference splicing conditions are set. If the analysis of the condition of each end face F1a, F2a shows that there is an abnormality in either or both of the end faces F1a, F2a, splicing conditions different from the predetermined reference splicing conditions are set according to the condition of the end face(s) with the abnormality.

[0039] The effects obtained by the fusion splicer 10 and fusion splicing method according to the present embodiment described above will now be described. In the fusion splicer 10 and fusion splicing method according to the present embodiment, the splicing conditions set according to the state of the end faces F1a, F2a include at least one of (1) the positions of the end faces F1a, F2a before the start of discharge, (2) the distance between the end faces F1a, F2a before the start of discharge, (3) the pre-discharge time, (4) the main discharge time, (5) the amount of push-in after the end faces F1a, F2a contact each other, and (6) the amount of pull-back after the end faces F1a, F2a are pushed together. In this case, compared to controlling only the amount of discharge energy (discharge power) as in the device described in Patent Document 1, for example, more suitable splicing conditions can be set according to the state of the end faces F1a, F2a of the optical fibers F1, F2. This further improves the quality of the fusion splice and reduces splice loss.

[0040] The splicing conditions set according to the state of each of the end faces F1a, F2a may include at least three of the above (1) to (6), which can further improve the quality of the fusion splice and further reduce splice loss.

[0041] The optical fiber fusion splicer and method for fusion splicing optical fibers according to the present disclosure are not limited to the above-described embodiments and may be modified in various ways. For example, in the above embodiments, three conditions—chipped, ripped, and tilted—were used as examples of the end face conditions of the optical fibers. However, various other conditions may be included as criteria for determining the splicing conditions. The splicing conditions set according to the condition of each end face F1a, F2a may include other conditions in addition to at least one of (1) to (6) above. Examples of other conditions include the relative axial misalignment between the optical fibers F1, F2 and the time interval between discharges during intermittent discharges. The discharge power may be included in the splicing conditions, or may be constant regardless of the end face conditions of the optical fibers. The splicing conditions set according to the condition of each end face F1a, F2a of the optical fibers F1, F2 include not only reference splicing conditions but also settings for variations from the reference splicing conditions depending on the condition of each end face F1a, F2a. [Explanation of symbols]

[0042] 2. Housing 3...Fusion splice 3a...Fiber positioning part 3b...electrode rod 3c...Optical fiber holder 4...heater 5...Monitor 6...Windshield cover 7...Power switch 8...Connection start switch 9...Camera 10...Fusion splicer 12...Fusion control section 12a...CPU 12b...RAM 12c…ROM 13...Basic control unit 14...Condition setting section A…chipped B…Lip CL...Clad CR...Core D...Spacing Da…Maximum interval Db…Minimum interval F1...first optical fiber F1a...end face F2: Second optical fiber F2a...end face MSX,MSY…direction PX, PY...Image

Claims

1. an image acquisition unit that acquires an image including each end face of the first and second optical fibers to be connected in a state in which the end faces of the first and second optical fibers are arranged opposite each other; a condition setting unit that grasps the state of each of the end faces based on the image and sets connection conditions according to the state of each of the end faces, the connection conditions including at least one of the position of each of the end faces before the start of discharge, the distance between each of the end faces before the start of discharge, a pre-discharge time, a main discharge time, a push-in amount after the end faces come into contact with each other, and a pull-back amount after the end faces have been pushed together; a fusion splicing unit that fusion-splices the first and second optical fibers together by discharging between a pair of electrode rods in accordance with the splicing conditions set by the condition setting unit; An optical fiber fusion splicer comprising:

2. 2. The optical fiber fusion splicer according to claim 1, wherein the splicing conditions include at least three of the position, the interval, the pre-discharge time, the main discharge time, the push-in amount, and the pull-back amount.

3. the connection condition includes the position, 3. The optical fiber fusion splicer according to claim 1, wherein the positions are positions of the end faces relative to a line connecting central axes of the pair of electrode rods at the start of preliminary discharge.

4. the connection conditions include the preliminary discharge time, 4. The optical fiber fusion splicer according to claim 1, wherein the preliminary discharge time is a time from when an arc discharge starts to when relative movement of the first and second optical fibers starts so as to bring the end faces into contact with each other.

5. the connection conditions include the main discharge time, 5. The optical fiber fusion splicer according to claim 1, wherein the main discharge time is a time from when the end faces come into contact with each other to when application of voltage to the pair of electrode rods is stopped.

6. the connection condition includes the pushing amount, 6. The optical fiber fusion splicer according to claim 1, wherein the pushing amount is a distance that the first and second optical fibers are further moved relative to each other in the same direction during discharge after the end faces of the first and second optical fibers come into contact with each other.

7. the connection condition includes the pullback amount, 7. The optical fiber fusion splicer according to claim 1, wherein the pullback amount is a distance that the first and second optical fibers are moved relatively in a direction that moves the end faces away from each other during fusion splicing after the end faces have come into contact with each other and then the end faces are further pushed in.

8. 8. The optical fiber fusion splicer according to claim 1, wherein the state of each end face includes a position and a depth of a depression formed on each end face.

9. 9. The optical fiber fusion splicer according to claim 1, wherein the state of each end face includes a position and height of a protrusion at the edge of each end face.

10. 10. The optical fiber fusion splicer according to claim 1, wherein the state of each end face includes a direction and angle of inclination of each end face.

11. acquiring an image including the end faces of the first and second optical fibers to be connected, in a state in which the end faces of the first and second optical fibers are arranged opposite each other; a step of grasping the state of each of the end faces based on the image and setting connection conditions according to the state of each of the end faces, the connection conditions including at least one of the position of each of the end faces before the start of discharge, the distance between the end faces before the start of discharge, a pre-discharge time, a main discharge time, a push-in amount after the end faces come into contact with each other, and a pull-back amount after the end faces have been pushed together; fusion-splicing the first and second optical fibers to each other by discharging between a pair of electrode rods in accordance with the splicing conditions set in the step of setting the splicing conditions; 1. A method for fusion splicing optical fibers, comprising:

12. 12. The method for fusion splicing optical fibers according to claim 11, wherein the splicing conditions include at least three of the position, the interval, the pre-discharge time, the main discharge time, the push-in amount, and the pull-back amount.

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