Patent Publication Number: US-2009224019-A1

Title: Optical fiber cutting method,  device used in same method, and connector assembly method including same method

Description:
TECHNICAL FIELD 
     The present invention relates to a method of cutting an optical fiber together with its coating, a device used in the method, and a connector assembly method including the cutting method. 
     BACKGROUND ART 
     A method of cutting an optical fiber together with its coating is disclosed in Japanese Patent Application Publication No. 2005-345530. In this method, a front clamper and a rear clamper of optical fiber supporting means respectively support the front and rear of a cutting position of an optical fiber, and tension applying means urges the front and rear clampers in directions away from each other to apply tension to the clamped optical fiber. Then, a rotating blade cuts a coating and a glass fiber in this state. By cutting the optical fiber under the applied tension, the glass fiber can be cut such that the end face of the glass fiber is perpendicular and flat with respect to the optical axis. Further, because the coating and the glass fiber are cut at the same time, the number of man-hours can be reduced. 
     Incidentally, when glass fibers having end faces that are perpendicular with respect to their optical axes are interconnected, part of the optical signal is reflected and returns in the incident direction when the optical signal passes through the connecting faces. When two-way communication is performed by a single optical fiber, reflected light resulting from transmitted light in one direction interferes with transmitted light in the opposite direction, and a disadvantage particularly arises. Thus, the reflection direction of the reflected light has been shifted by causing the connecting faces to slant and interconnecting the connecting faces to prevent adverse affects on the transmitted light. 
     However, causing the connecting faces of the optical fibers to slant has heretofore been performed by working such as polishing. For that reason, when optical fibers are to be delivered to homes, cutting the optical fibers, working the end faces such that they slant with respect to their optical axes, and then interconnecting the optical fibers in the field is not only cumbersome and requiring time but also technically difficult. 
     Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2005-345530 
     DISCLOSURE OF THE INVENTION 
     Problem that the Invention is to Solve 
     It is an object of the present invention to provide a method of cutting an optical fiber easily in the field such that its end face after being cut slants with respect to its optical axis, a cutting device used in the method, and a connector assembly method including the cutting method. 
     Means for Solving the Problem 
     In order to achieve this object, there is provided a method of cutting an optical fiber having a glass fiber and a coating that covers the glass fiber. In this method, a twist is imparted to a portion of the optical fiber including a cutting position, a notch is formed in the coating and the glass fiber at the cutting position, and an external force is applied to the optical fiber whereby the optical fiber is cut at the cutting position. 
     The twist may be imparted to the portion of the optical fiber including the cutting position by fixing the optical fiber at one side of the cutting position and rotating the optical fiber at the other side. Further, in a state where one side face of the optical fiber is supported and side pressure is applied thereto at the cutting position, the notch may be formed in the coating and the glass fiber from the other side face. 
     In another aspect of the invention, there is provided a device that cuts an optical fiber having a glass fiber and a coating that covers the glass fiber. The device includes optical fiber holding means that fixes the optical fiber on one side of a cutting position of the optical fiber, optical fiber rotating means that fixes the optical fiber, such that the optical fiber may freely rotate, on the other side of the cutting position of the optical fiber, and a blade that forms a notch in the coating and the glass fiber. The cutting device may also include connector holding means that releasably holds a connector that will attach to a front end of the optical fiber, and a connector may be held in the connector holding means. 
     In yet another aspect of the invention, there is provided a connector assembly method comprising the following steps (1) to (6): (1) inserting an optical fiber having a glass fiber and a coating that covers the glass fiber into a connector, and pulling out a front end portion of the optical fiber from a connector; (2) fixing the optical fiber in optical fiber holding means of the connector and fixing the front end portion of the optical fiber in optical fiber rotating means; (3) rotating the optical fiber rotating means to impart a twist to a portion of the optical fiber including a cutting position; (4) forming a notch in the coating and the glass fiber at the cutting position; (5) applying an external force to the optical fiber and cutting the optical fiber at the cutting position; and (6) temporarily releasing the optical fiber holding means, pulling back the optical fiber until its cut face is positioned in a predetermined position inside the connector, and then again fixing the optical fiber in the optical fiber holding means. 
     ADVANTAGES OF THE INVENTION 
     According to the present invention, an optical fiber having a glass fiber and a coating that covers the glass fiber is cut in a state where it is twisted, so the optical fiber can be cut easily in the field such that its end face after being cut slants with respect to its optical axis. Further, the number of man-hours can be reduced because cutting the optical fiber together with its coating makes a step of removing the coating unnecessary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In  FIG. 1 , region (A) to region (C) are schematic diagrams showing steps in an embodiment of an optical fiber cutting method pertaining to the present invention. 
         FIG. 2  includes a front diagram and both side end face diagrams showing a state where an optical fiber has been placed in a cutting device in the embodiment of the optical fiber cutting method pertaining to the present invention. 
         FIG. 3  is a cross-sectional diagram showing the optical fiber being cut by a blade in the embodiment of the optical fiber cutting method pertaining to the present invention. 
         FIG. 4  is a graph showing the relationship between the rotational angle of optical fiber rotating means and an angle that an end face of the optical fiber after being cut forms with respect to its optical axis in the embodiment of the optical fiber cutting method pertaining to the present invention. 
         FIG. 5  is a schematic diagram showing an embodiment of an optical fiber cutting device pertaining to the present invention, with region (A) being a plan diagram and region (B) being a cross-sectional diagram at position B-B in region (A). 
       In  FIG. 6 , region (A) includes a front diagram and a side diagram showing a first embodiment of the blade and region (B) is a front diagram showing a second embodiment of the blade. 
       In  FIG. 7 , region (A) to region (D) are schematic diagrams showing steps in an embodiment of a connector assembly method pertaining to the present invention. 
         FIG. 8  is a cross-sectional diagram showing an example of connector interconnection using connectors manufactured by the connector assembly method pertaining to the present invention. 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS 
       
     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                 10 
                 Cutting Device 
                 11 
                 Optical Fiber 
               
               
                 11a 
                 Glass Fiber 
                 11b 
                 Coating 
               
               
                 12 
                 Cutting Position 
                 13 
                 Blade 
               
               
                 21 
                 Optical Fiber Holding 
                 22 
                 Optical Fiber Rotating 
               
               
                   
                 Means 
                   
                 Means 
               
               
                 23 
                 Side Pressure Member 
                 24 
                 Connector Holding Means 
               
               
                 30 
                 Connector 
               
               
                   
               
            
           
         
       
     
     BEST MODES FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will be described below with reference to the drawings. The drawings are for explanatory purposes and are not be intended to limit the scope of the invention. In the drawings, the same reference numerals represent the same parts in order to avoid redundancy of description. The proportions of dimensions in the drawings are not necessarily accurate. 
     To begin, an embodiment of an optical fiber cutting method pertaining to the present invention will be described. In  FIG. 1 , region (A) to region (C) are schematic diagrams showing steps in the embodiment of the cutting method. First, a relative twist is imparted to both sides of an optical fiber  11  on either side of a cutting position  12  (region (A)). Next, a notch  12   a  is formed in a coating lib and a glass fiber  11   a  in this twisted state (region (B)). Then, an external force F is applied to the optical fiber  11  and the optical fiber  11  is cut at the cutting position  12  (region (C)). Though, in region (C), an external force F that is perpendicular to the axis of the optical fiber  12  is applied and the optical fiber is cut, an external force that pulls the optical fiber  12  towards both sides may also be applied to cut the optical fiber. 
       FIG. 2  includes a front diagram and both side end face diagrams showing a state where the optical fiber has been placed in a cutting device. One side (right side) of the optical fiber  11  with respect to the cutting position  12  is fixed by optical fiber holding means  21  and the other side (left side) is rotated by optical fiber rotating means  22 , whereby the optical fiber  11  can be twisted at the cutting position. At this time, the twist amount of the optical fiber can be adjusted by the rotational amount of the rotating means  22  and the slant angle of the cut face can be easily adjusted. 
       FIG. 3  is a cross-sectional diagram showing the optical fiber being cut by a blade. When the blade cuts into the coating  11   b  and nicks the glass fiber  11   a , it is preferable to apply a force with a side pressure member  23  to one side face (upper face) of the optical fiber  11  at the cutting position  12  and to notch the other side face (lower face) with a blade  13 . Thus, the optical fiber  11  can be prevented from escaping when the blade cuts into the optical fiber, and the notch or the like can be reliably formed. 
       FIG. 4  is a graph showing the relationship between the rotational angle of the optical fiber rotating means and an angle that the end face of the optical fiber after being cut forms with respect to its optical axis, wherein the horizontal axis represents the rotational angle and the vertical axis represents the angle that the end face forms with respect to its optical axis. It is noted that an optical fiber where the outer diameter of the glass fiber  11   a  is 80 μm and where the outer diameter of the optical fiber  11  is 125 μm is used as the optical fiber  11 . By setting the rotational angle of the optical fiber  11  to 100° to 200°, for example, an optical fiber including an end face that slants 5° to 8° with respect to its optical axis is obtained. 
     According to the embodiment of the optical fiber cutting method of the present invention, the optical fiber  11  is twisted on both sides of the cutting position  12  and cut, so the optical fiber can be cut easily in the field such that its end face after being cut slants with respect to its optical axis. Further, a step of removing the coating  11   b  becomes unnecessary because the optical fiber  11  is cut together with its coating  11   b , and the optical fiber can be efficiently cut in a short amount of time even in the field. It is noted that in the case of cables and cords where the optical fiber  11  is covered by a sheath, the aforementioned cutting is performed after getting rid of the sheath and removing the optical fiber  11  covered with the coating  11   b.    
     Next, an embodiment of an optical fiber connecting device pertaining to the present invention will be described.  FIG. 5  is a schematic diagram showing the embodiment of the optical fiber cutting device pertaining to the present invention, with region (A) being a plan diagram and region (B) being a cross-sectional diagram at position B-B in region (A). An optical fiber cutting device  10  cuts the optical fiber  11  having the glass fiber  11   a  and the coating  11   b  that covers the glass fiber  11   a . The cutting device  10  includes, on a base  20 , the optical fiber holding means  21  on one side of the cutting position  12  (right side in  FIG. 5 ) and the optical fiber rotating means  22  on the other side (left side in  FIG. 5 ). Additionally, the cutting device  10  includes the blade  13  and notch amount adjusting means. 
     The holding means  21  is disposed such that it may freely open and close upward and downward, for example, and when the holding means  21  closes, it can fix the optical fiber  11  placed along the upper face of the base  20 . The rotating means  22  is a circular cylinder-shaped member  22   a  that may freely rotate and can halt in an arbitrary rotational position, for example, and the optical fiber  11  is capable of being passed through the center of the circular cylinder-shaped member  22   a  and fixed to the circular cylinder-shaped member  22   a . One end of the optical fiber  11  is fixed by the holding means  21  and the other end is rotated by the circular cylinder-shaped member  22   a  of the rotating means  22 , whereby the optical fiber  11  can be twisted at an arbitrary twist angle. 
     It is preferable to dispose a hinge portion  20   a  in the base  20  in the vicinity of the cutting position  12  to enable the base  20  to be folded. Thus, by folding the base  20 , an external force can be caused to act on the notch  12   a  in the optical fiber  11 . 
     The blade  13  is slid by driving means such as a spring in a direction substantially perpendicular to the longitudinal direction of the optical fiber  11  and along a recessed portion  20   b  disposed in a portion of the base  20  corresponding to the cutting position  12 , and the blade  13  forms a notch in the coating  11   b  and the glass fiber  11   a . The notch amount adjusting means adjusts the notch amount resulting from the blade  13 . 
     Region (A) of  FIG. 6  includes a front diagram and a side diagram showing a first embodiment of the blade. The blade  13  of the first embodiment includes a blade  13 A and a support face  23   a . The blade  13 A is slanted, with its front end (lower side in region (A) of  FIG. 5 ) being low and its rear end having a height that reaches the lower portion of the glass fiber  11   a  of the optical fiber  11 . The slanted support face  23   a  as the notch amount adjusting means is integrally disposed adjacent to the blade  13 A, and the blade  13 A protrudes a notch amount d from the support face  23   a . When the blade  13 A is slid to form the notch  12   a  in the optical fiber  11 , the support face  23   a  makes contact with the bottom surface of the optical fiber  11 , so a notch having a depth corresponding to the protruding amount d is formed in the optical fiber  11 . 
     Region (B) of  FIG. 6  is a front diagram showing a second embodiment of the blade. The blade  13  of the second embodiment includes a circular rotating blade  13 B, and the blade  13 B is slid while being rotated to form a notch in the optical fiber  11 . In the second embodiment, the notch amount adjusting means is a side pressure member  23   b  that is disposed on the optical fiber  11  and applies side pressure from above to the optical fiber  11 . The position of the side pressure member  23   b  is adjusted such that the upper end of the blade  13 B slides in a state where it reaches the lower portion of the glass fiber  11   a . The side pressure member  23   b  restricts upward movement of the optical fiber  11  and the rotating blade  13 B is caused to slide, so that a notch of the predetermined amount d can be formed in the optical fiber  11 . 
     Further, as shown in region (A) and region (B) of  FIG. 5 , connector holding means  24  is disposed in the upper face of the base  20 . The connector holding means  24  is a groove that is formed on the base  20  and holds a connector, and part of a connector  30  that attaches to the front end of the optical fiber  11  fits into the groove so that the connector holding means  24  can releasably hold the connector  30 . 
     When cutting of the optical fiber  11  is performed using the optical fiber cutting device  10 , one side of the cutting position in the longitudinal direction of the optical fiber  11  is fixed to the base  20  by the holding means  21 , and the other side is fixed to the rotating means  22 . At this time, it is preferable to apply predetermined tension to the optical fiber  11 . Then, the rotating means  22  is rotated to twist the optical fiber  11   a  predetermined angle, the notch  12   a  is formed in the coating  11   b  and the glass fiber  11   a  by the blade  13   a , and an external force is applied to the position of the notch  12  to cause the optical fiber  11  to break. 
     According to the cutting device  10 , the optical fiber  11  can be twisted at the cutting position  12 , and the notch can be formed by the blade  13  in the coating  11   b  and the glass fiber  11   a  of the optical fiber  11  in the twisted state. At this time, the notch amount is adjusted by the notch amount adjusting means, so that a notch can be reliably formed with the predetermined notch amount. Further, by cutting the optical fiber  11  in a state where the connector  30  is attached to the connector holding means  24  and the optical fiber  11  has been passed through the connector  30 , the optical fiber  11  can be connected to the connector  30  easily and rapidly. 
     Next, an embodiment of a connector assembly method pertaining to the present invention will be described. In  FIG. 7 , region (A) to region (D) are schematic diagrams showing steps in the embodiment of the connector assembly method pertaining to the present invention. In the present embodiment, a connector  30  is held in the connector holding means  24  of the optical fiber cutting device  10  in order to attach the connector  30  to an optical cable  14 . 
     First, the sheath of the optical cable  14  is removed at the front end portion, and the optical fiber  11  covered with the coating  11   b  is taken out. Then, the optical fiber  11  is passed through the optical fiber holding means  21  and the optical fiber rotating means  22 , the optical fiber is fixed to the base  20  by the holding means  21 , and the optical fiber is fixed to the rotating means  22  (region (A)). Next, the circular cylinder-shaped member  22   a  of the rotating means  22  is rotated at a predetermined angle to twist the optical fiber  11  at the cutting position  12  (region (B)). The blade  13  is driven in a state where the optical fiber  11  has been twisted, the coating  11   b  of the optical fiber  11  is cut by the blade  13 , and the notch  12   a  is formed in part of the glass fiber  11   a  (region (C)). At this time, a notch of a constant amount is obtained by adjusting the height of the blade  13 . Then, the base  20  is folded about the hinge  20   a  to apply an external force (here, folding force) to the optical fiber  11  and cause the optical fiber  11  to break (region (D)). Thereafter, the optical fiber  11  is pulled back such that the cut face of the optical fiber  11  is positioned in a predetermined position in the connector  30 , and the optical cable  14  is fixed to the connector  30 . 
     According to the embodiment of the connector assembly method of the present invention, the optical fiber  11  covered with the coating  11   b  is fixed to the connector  30 , so that time and effort to remove the coating  11   b  becomes unnecessary and the glass fiber  11   a  can be prevented from sustaining damage during in the field work. Further, the optical fiber  11  that has been cut such that its front end face slants with respect to its optical axis is fixed to the connector, so that when the optical fibers  11  are to be interconnected via the connector  30 , reflected light at the connecting faces can be prevented from returning and adversely affecting communication and the like. It is noted that in the case of cables and cords where the optical fiber is covered with a sheath, a predetermined length of the sheath is removed to take out the covered optical fiber, and the connector is attached. At that time, the optical fiber can be fixed together with the sheath. 
       FIG. 8  is a cross-sectional diagram showing an example of connector interconnection using connectors manufactured by the connector assembly method pertaining to the present invention. The connector interconnection shown in  FIG. 8  is achieved by interconnecting a connector  30 A attached to a first optical cable  14 A and a connector  30 B attached to a second optical cable  14 B, so that the optical cables  14 A and  14 B become interconnected. The connectors  30 A and  30 B are male and female connectors assembled by the connector assembly method of the present invention. 
     Connecting end faces of optical fibers  11 A and  11 B pulled out from the optical cables  14 A and  14 B contact each other at a contact face  15 . Before the connectors  30 A and  30 B are interconnected, the optical fiber  11 A protrudes a predetermined amount from the front end of the connector  30 A and the optical fiber  11 B protrudes a predetermined amount from the front end of the connector  30 B. When the connectors  30 A and  30 B from which the optical fibers  11 A and  11 B protrude are interconnected as shown in  FIG. 8 , slanted end faces D of the optical fibers  11 A and  11 B contact and collide with each other so that the optical fibers  11 A and  11 B are caused to move toward the rear sides of the connectors  30 A and  30 B. The optical fibers  11 A and  11 B that have been caused to move bend in bend-accommodating spaces  11   c  inside the connectors  30 A and  30 B. 
     At this time, the connecting end faces of the optical fibers  11 A and  11 B push against each other and are reliably interconnected because of a force resulting from the bent optical fibers  11 A and  11 B trying to extend. Both of the connecting end faces slant a predetermined angle with respect to a plane orthogonal to the optical axis and surface-contact each other in a slanted state, so reflected light at the connecting faces becomes reflected in a direction different from the optical axis direction, and connection characteristics can be improved. 
     It is noted that the optical fiber cutting method and the optical fiber cutting device of the present invention are not limited to the aforementioned embodiments and may be appropriately altered and improved. 
     This application is based on a Japanese patent application (Japanese Patent Application No. 2006-108101) filed on Apr. 10, 2006, and the disclosure thereof are incorporated by reference herein. 
     INDUSTRIAL APPLICABILITY 
     The optical fiber cutting method, the device used in the same method, and the connector assembly method including the same method are effective as a method of cutting an optical fiber in the field and diagonally working its end face.