JP3607642B2 - Optical fiber fusion splicer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber fusion splicer for connecting two optical fibers by butting the end faces of two optical fibers to be connected to each other and heating the butted portion by arc discharge to fuse them together. More particularly, the present invention relates to an optical fiber fusion splicer suitable for a case where the optical fiber on one side is a dispersion compensating optical fiber.
[0002]
[Prior art]
In the optical fiber fusion splicing method, when the end faces of two optical fibers to be connected are butted together, the butted portion is heated by arc discharge to melt the ends of both optical fibers. The two optical fibers are pushed into each other, the end faces are fused, and the two optical fibers are connected to each other. An optical fiber fusion splicer is an apparatus for performing this connection method, and generates a discharge beam between two discharge electrodes, and when the optical fiber is placed in the discharge beam, the optical fiber Discharge heating means for heating the optical fiber, and optical fiber holding means for holding both optical fibers so that both ends of the two optical fibers to be connected are positioned in the discharge beam.
[0003]
Usually, in such an optical fiber fusion splicing method and fusion splicer, both ends of the two optical fibers are evenly distributed so that the center of the discharge beam is located at the butt portion of both optical fibers. I try to heat it.
[0004]
[Problems to be solved by the invention]
However, when two optical fibers to be connected are heated equally as in the conventional case, if one of them is a dispersion compensating optical fiber or the like, the connection cannot be made with low connection loss, or the mechanical connection itself is excellent. There are problems such as being unable to do so.
[0005]
In other words, in the optical fiber doped with erbium or the like in the core, the diffusion rate of the dopant is fast. Therefore, when both optical fibers are heated evenly when the optical fiber is fused and connected, the diffusion rate of the dopant is increased. However, the mode field diameter of the fast optical fiber is larger than that of the other optical fiber, and the connection loss increases. In addition, since an optical fiber having a thin cladding diameter originally has a small heat capacity, when the optical fiber having a small cladding diameter and a normal optical fiber are fusion-bonded to each other, if both are heated evenly, the optical fiber having a small heat capacity is The ends are melted and the mechanical connection itself becomes difficult.
[0006]
In view of the above, according to the present invention, an optical fiber that is vulnerable to heat, such as an optical fiber whose refractive index profile is likely to be broken by heating due to a high diffusion rate of the dopant or an optical fiber having a thin cladding diameter, is the optical fiber on one side. In such a case, an object of the present invention is to provide an optical fiber fusion splicer improved so that it can be fusion spliced well with low connection loss.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the optical fiber fusion splicer according to the present invention, two discharge electrodes that generate arc discharge and two optical fibers that should be connected to each other are heat-sensitive optical fibers. A pair of V-groove blocks each holding an optical fiber, a moving block that moves the optical fiber, an imaging device that images the butted portion of the two optical fibers, and a video signal from the imaging device is transmitted. Image processing apparatus for performing image processing, and known information about the shape of the discharge beam, and holding information of the moving block based on the discharge beam shape information and information obtained by the image processing apparatus. By controlling the movement, the tip of the two optical fibers to be connected on the non-heat-sensitive side penetrates into the other side deeper than the center of the discharge beam, and the optical fiber on the heat-sensitive side. When the ends of the optical fibers are abutted with each other in a state shifted from the discharge beam in the length direction of the optical fiber so that the tip of the optical fiber enters the end of the discharge beam shallowly, and both optical fiber tips are melted by heating of the discharge beam And a control device that moves only the optical fiber on one side, which is deeper into the discharge beam, toward the optical fiber that is weak against heat on the other side, and pushes it in.
[0008]
In this optical fiber fusion splicer, the control device controls the movement of the moving block based on the known discharge beam shape information held therein and the information obtained by the image processing device, so that one of them is heated. The tip of the two optical fibers to be connected, which are weak optical fibers, enter the other side deeper than the discharge beam center, and the tip of the optical fiber on the side sensitive to heat is the end of the discharge beam. The end surfaces of the optical fibers are abutted with each other in a state shifted from the discharge beam in the length direction of the optical fiber so as to enter into the shallower portion of the optical fiber. Only the optical fiber on one side is moved and pushed in the direction of the optical fiber that is weak against heat on the other side. Therefore, the tip of the optical fiber on the heat-sensitive side is heated not only in the heating and melting process but also in the heating and pushing process, that is, in the entire heating process, because it only enters the end of the discharge beam shallowly. Is limited to its tip, and since it is the end of the discharge beam, the heating intensity is also weak. Therefore, the end of the heat-sensitive optical fiber is not heated more than necessary for fusion-bonding in the entire heating process. Therefore, it is possible to achieve a good fusion splicing with little connection loss between the optical fiber that is weak against heat and the optical fiber that is not so. Also, the connection time does not increase.
[0009]
Therefore, when trying to connect a normal optical fiber and an optical fiber whose refractive index distribution is likely to be destroyed by heating such as a dispersion compensating optical fiber, the latter optical fiber is inserted into the discharge beam end shallowly. By heating in a state where the optical fiber is heated, it is possible to prevent the profile of the refractive index distribution in the optical fiber from being broken, so that fusion splicing can be performed with low connection loss. Also, when connecting an ordinary optical fiber and an optical fiber having a small cladding diameter and a small heat capacity, the optical fiber having a small cladding diameter is heated in a state where the tip of the optical fiber enters the discharge beam end portion shallowly. As a result, it is possible to prevent the inconvenience that the optical fiber is completely melted and cannot be fusion-bonded in a mechanical sense, and the fusion-splicing can be performed satisfactorily.
[0010]
According to this optical fiber fusion splicer, an image pickup device that picks up an image of a butt portion of two optical fibers, an image processing device that performs image processing by sending a video signal from the image pickup device, and an image processing device A control device to which the obtained information is sent, and by controlling the moving block by this control device, the optical fiber is butted against the discharge beam, or the optical fiber on the deeper side is pushed in. The operation control is automatically performed. These image pickup device, image processing device, control device, V-groove block and moving block for moving the optical fiber are provided in a normal optical fiber fusion splicer, and only a part of the control device is reworked. It is feasible. Therefore, there is no cost.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view conceptually showing an embodiment of an optical fiber fusion splicing method according to the present invention. First, as shown in FIG. 1A, a heating and melting step of the optical fiber butting portion is performed. At this time, the two optical fibers 10 and 20 to be connected are butted in a state where the sheaths (protective films) 13 and 23 are peeled off at their tips, but the butted portion (center) position B is The optical fibers 10 and 20 are shifted in the length direction from the center A of the discharge beam 43 to be formed between the discharge electrodes (rods) 41 and 42.
[0012]
Of the two optical fibers 10 and 20 to be connected, the optical fiber 10 (the left side of the figure) is an optical fiber whose refractive index profile is likely to be destroyed by heating due to a high diffusion rate of the dopant or light with a thin cladding diameter. It is assumed that the optical fiber is weak against heat, such as a fiber. It is assumed that the other optical fiber 20 is not an optical fiber with particularly low heat but a normal optical fiber such as a normal single mode optical fiber. In this case, the tip of the optical fiber 20 enters the discharge beam 43 deeper than the center A of the discharge beam 43 to be generated, and the tip of the optical fiber 10 enters the end of the discharge beam 43 shallowly. Both optical fibers 10 and 20 are abutted so as to be.
[0013]
After the two optical fibers 10 and 20 to be connected in this manner are butted together, a discharge beam 43 is formed between the discharge electrodes 41 and 42, and the butted portion is heated. The ends of the optical fibers 10 and 20 at the butt portion are melted by the heating by the discharge beam 43, but the optical fiber 10 that is weak against heat only enters the end of the discharge beam 43 shallowly. It is limited to the tip, and since it is the end of the discharge beam 43, the heating intensity is also weak. On the other hand, since the tip of the other optical fiber 20 has penetrated deeply into the discharge beam 43, it is sufficiently heated.
[0014]
When the tips of both optical fibers 10 and 20 are melted in this way, a heating and pushing process is started, and only the optical fiber 20 is moved to the other optical fiber 10 side as indicated by the arrow in FIG. Since the other optical fiber 10 is fixed, as shown in FIG. 2B, the end face of the optical fiber 20 collides with the end face of the optical fiber 10 and is pushed in. At this time, both end faces are melted. Therefore, the end faces are bonded and joined.
[0015]
Also in this heating and pushing step, since the optical fiber 10 is fixed in a state of entering the end of the discharge beam 43 shallowly, the optical fiber 10 is only heated by the weak heating power at the end of the discharge beam 43.
[0016]
Therefore, the heat-sensitive optical fiber 10 is not heated more than necessary for the fusion-splicing process in the heating and pressing process as well as the heating and pressing process, that is, in all the heating processes. Therefore, even when the optical fiber 10 is an optical fiber having a high diffusion rate of the dopant, the diffusion of the dopant can be prevented and the profile of the refractive index distribution can be maintained, so that the fusion splicing can be performed with a low connection loss. . Further, in the case of an optical fiber having a thin clad diameter and a small heat capacity, since the heating amount can be reduced, there is no inconvenience that the fusion connection itself in the mechanical sense cannot be performed because it is completely melted. Also, the connection time does not increase.
[0017]
Next, an embodiment of an optical fiber fusion splicer that performs the above-mentioned heat melting step and heat pushing step to perform fusion splicing of optical fibers will be described with reference to FIG. FIG. 2 is a schematic diagram conceptually showing an optical fiber fusion splicer according to an embodiment of the present invention. In FIG. 2, V-groove blocks 52 and 52 constitute a part of holding means for holding two optical fibers 10 and 20 to be connected. Positioning is performed by being accommodated in the 52 V-groove. The V-groove blocks 52 and 52 are mounted on the moving blocks 51 and 51. Here, the axial direction (horizontal direction) of the optical fibers 10 and 20 is the Z axis, the horizontal direction perpendicular to the axes of the optical fibers 10 and 20 is the X axis, and the vertical direction perpendicular to the axes of the optical fibers 10 and 20 is the Y axis. It is said. The moving blocks 51 and 51 are mounted on the base 56 and are driven by the motors 54 and 54 and moved in the X, Y, and Z directions on the base 56.
[0018]
Here, the discharge electrodes (rods) 41 and 42 are arranged to face each other in the X direction, and are fixed by an appropriate mechanism omitted in the drawing. A high voltage is supplied to the discharge electrodes 41 and 42 from the discharge power supply device 34, and an arc discharge is generated between the discharge electrodes 41 and 42. The butted portions of the optical fibers 10 and 20 are heated by the heat of the arc discharge so that the fusion splicing is performed.
[0019]
The TV camera (imaging device) 31 is arranged so as to capture an image of the butt portion of both optical fibers 10 and 20. The video signal output from the TV camera 31 is sent to the image processing device 32 for image processing. Information obtained by the image processing is sent to the control device 33, and the motor 54 and the like are controlled, and the discharge power supply device 34 is controlled.
[0020]
FIG. 3 shows a more specific configuration. As shown in FIG. 3, the V-groove blocks 52, 52 are mounted on the moving blocks 51, 51. In addition to these, sheath clamps 53, 53 are mounted on the moving blocks 51, 51. The sheath clamps 53 and 53 are for clamping and fixing the sheaths (protective films) of the optical fibers 10 and 20. The moving blocks 51, 51 are arranged in the axial direction (Z-axis direction) of the optical fibers 10, 20 as indicated by arrows by a motion transmission mechanism such as a micrometer 55, 55 that converts the rotation of the motors 54, 54 into linear motion. Moved toward or away from each other. The moving blocks 51 and 51 are also moved along the X axis and the Y axis, but the description of the mechanism is omitted here (not shown in the figure).
[0021]
When the two optical fibers 10 and 20 are to be connected, first, the optical fibers 10 and 20 that have been peeled off from the sheaths at the ends and set in the state of the core are set in the V-groove blocks 52 and 52, and the sheath clamp The portions of the sheaths 13 and 23 are fixed with 53 and 53. Since the TV camera 31 obtains images of both ends of the optical fibers 10 and 20, the image signal is processed by the image processing device 32 so that the axes of the optical fibers 10 and 20 coincide with each other. Then, the motor 54 and the like are controlled via the control device 33 to adjust the positions of the moving blocks 51 and 51 in the X and Y directions.
[0022]
Next, the motors 54 and 54 are driven so that the moving blocks 51 and 51 move in the Z direction while confirming the tip positions of the two optical fibers 10 and 20 by processing in the image processing device 32, and FIG. As shown by (2), both optical fibers 10 and 20 are abutted so that the position B of the abutting portion (the center thereof) is shifted from the center A of the discharge beam 43 to be formed between the discharge electrodes 41 and 42. At this time, the discharge beam 43 has not yet been formed between the discharge electrodes 41 and 42, but since the shape of the discharge beam 43 formed therein is known in advance, the information is given to the control device 33 (or the image processing device). 32), the tip of the optical fiber 20 enters the discharge beam 43 deeper than the center A of the discharge beam 43 to be generated, and the tip of the optical fiber 10 enters the end of the discharge beam 43 shallowly. Both optical fibers 10 and 20 can be abutted so as to be in a state of being present.
[0023]
The position adjustment in the X and Y directions and the butting position adjustment in the Z direction can be automatically performed by the image processing device 32 and the control device 33. When these position adjustments are completed, the control power supply 34 is controlled by the control device 33, high voltage supply from the discharge power supply device 34 is started, and the discharge beam 43 is interposed between the discharge electrodes 41 and 42. Is formed, and the butted portions of the optical fibers 10 and 20 are heated by the heat.
[0024]
When melting of the tips of the optical fibers 10 and 20 at the butting portion is confirmed by the TV camera 31 and the image processing device 32, or when a preset heating time has elapsed and the melting of both ends can be estimated, Only the motor 54 on the optical fiber 20 side is driven by the control device 33 and only the optical fiber 20 is moved in the Z direction toward the optical fiber 10, and the end face of the optical fiber 20 is pushed into the end face of the optical fiber 10. Is done. In this way, fusion splicing of both end surfaces is performed.
[0025]
As described above, since the adjustment of the butting position and the pushing of only the one-side optical fiber can be performed only by the mechanism that holds the optical fibers 10 and 20, the configuration is simplified. As for shifting the abutting position with respect to the center of the discharge beam 43, it is conceivable to move the positions of the discharge electrodes 41 and 42, but a structure and a motor for moving the discharge electrodes 41 and 42 are separately required. Is complicated. If only the optical fibers 10 and 20 are moved as described above, it is possible to cope with the optical fiber holding device provided in the normal optical fiber fusion splicer. That's it. Therefore, it can be easily applied to an existing optical fiber fusion splicer and does not cost. Also, the connection time does not increase.
[0026]
Here, the relationship between the position B of the butted portion (center) of the optical fibers 10 and 20 with respect to the center position A of the discharge beam 43 and the connection loss after fusion splicing were actually examined. A dispersion compensating optical fiber that is very weak against heating is used as the optical fiber 10, and a normal single mode optical fiber is used as the optical fiber 20. The resulting data is as shown in FIG. In FIG. 4, the position of the abutting portion on the horizontal axis is (B−A), “0” represents a state where the position B and the position A coincide with each other, and plus indicates that B is on the right side of A. , Minus is when B is on the left side of A, and the number represents the distance of (B−A) in μm.
[0027]
It can be understood from the data of FIG. 4 that the connection loss is better when the butt portion of the optical fibers 10 and 20 is shifted to the left side than the center of the discharge beam 43. However, although not shown in FIG. 4, if the butted portion and the center of the discharge beam are too far apart, the heat applied to the optical fiber 10 side becomes too small, so that a good fusion splice cannot be made. The amount of the connection loss is minimized when the distance is shifted. The actual connection is made with the shape of the discharge beam 43 actually formed, particularly the Z-direction heating distribution on the axes of the optical fibers 10 and 20. It depends on factors such as the type of optical fiber 10 and how much it is weak against heat. The optimum value can be obtained by experiments or the like, but in general, it is desirable to separate at least about 10 μm.
[0028]
Since the above configuration relates to an example for convenience of description, it is needless to say that the specific configuration can take various configurations other than the above. For example, in the above description, the TV camera 31, the image processing device 32, and the control device 33 are all controlled automatically. However, manual control is also possible. Other modifications can be made without departing from the spirit of the present invention.
[0029]
【The invention's effect】
As described above, according to the fusion splicer of the optical fiber of the present invention, one of the two optical fibers to be connected is weak against heating because the dopant diffusion rate is fast or the cladding diameter is small. In some cases, good fusion splicing with low connection loss can be performed, and the connection time is not extended. The optical fiber fusion splicer does not require a special mechanism, and can be easily applied to an existing fusion splicer, so that it can be realized at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic view conceptually showing an embodiment of an optical fiber fusion splicing method according to the present invention.
FIG. 2 is a schematic view conceptually showing an embodiment of an optical fiber fusion splicer according to the present invention.
FIG. 3 is a side view showing a specific example of an optical fiber holding mechanism.
FIG. 4 is a graph showing the relationship between the amount of misalignment of the optical fiber butting portion with respect to the discharge beam center and the connection loss.
[Explanation of symbols]
10, 20 Optical fiber 31 TV camera 32 Image processing device 33 Control device 34 Discharge power supply device 41, 42 Discharge electrode 43 Discharge beam 51 Moving block 52 V groove block 53 Sheath clamp 54 Motor 55 Micrometer 56 Base

Claims (1)

Two discharge electrodes for generating arc discharge, one pair of V-groove blocks each holding two optical fibers to be connected, one of which is a heat-sensitive optical fiber, and the above optical fiber is moved A moving block, an imaging device that images the butted portion of the two optical fibers, an image processing device that performs image processing by sending a video signal from the imaging device, and a known shape of the discharge beam The information is held, and the movement of the moving block is controlled based on the discharge beam shape information and the information obtained by the image processing apparatus, so that the heat-sensitive side of the two optical fibers to be connected The length of the optical fiber relative to the discharge beam is such that the tip of the non-flank enters the other side deeper than the center of the discharge beam and the tip of the heat-sensitive optical fiber enters the end of the discharge beam shallowly. When the ends of the optical fibers are abutted with each other in the state of being displaced in the direction, and the tips of the optical fibers are melted by the heating of the discharge beams, only the optical fiber on one side deeper into the discharge beam is changed to the other side. An optical fiber fusion splicer comprising: a control device that moves and pushes in the direction of an optical fiber that is weak against heat.

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