Patent Publication Number: US-9885833-B2

Title: Optical fiber scribing tool

Description:
PRIORITY CLAIM 
     This application claims the priority of U.S. Provisional Patent Application No. 61/702,644 filed on Sep. 18, 2012, which is fully incorporated by reference as if fully set forth herein. All publications noted below are fully incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to optical fibers, in particular to a tool that facilitates cleaving of optical fibers to shorten their length and produce a flat end on the fiber. 
     Description of Related Art 
     There are many advantages to transmitting light energy via optical fiber waveguides and the use thereof is diverse. Single or multiple fiber waveguides may be used simply for transmitting visible light to a remote location. Complex communication systems may transmit multiple specific optical signals. These devices often require the coupling of fibers in end-to-end relationship with the coupling representing a source of light loss. The cleaved end should be smooth and defect-free. If the ends of the fiber are uneven, excessive light loss can result due to reflection and refraction of light at the cleaved end surface (e.g., a splice or juncture region). For the vast majority of fiber optic applications, it is important to cleave the fiber such that the end of the fiber is completely flat in preparation for coupling. When placing optical fibers in end-to-end relationship, to minimize light loss, it is desirable to have the end faces of the fibers be smooth and lie in a plane perpendicular, or at a specific angle, to the axis of the fibers. In short, the cleaved fiber end face needs to be a single plane that is mirror quality to optimize coupling between fibers in demountable connectors, permanent splices and photonic devices. 
     The relatively widespread and ever increasing utilization of optical fibers in communication systems, data processing and other signal transmission systems has created a demand for satisfactory and efficient means of inter-joining terminals. Currently most demountable fiber connectors are factory installed. For field installation of optical fibers, it is particularly desirable to develop a process that can be simply and reliably deployed to properly cleave the optical fibers so as to minimize light loss when the fibers are subsequently coupled. 
     An optical fiber can be cleaved to produce a flat end face by propagating crack growth in controlled fashion. In summary, optical fiber cleaving requires two principle steps: (a) scribing an annular groove around the circumference of the fiber, which serves as an initial shallow groove at the surface, and (b) applying a suitable tensile stress to cause a crack to grow and propagate across the optical fiber, beginning at the circumference and growing radially towards the center. 
     U.S. Patent Application Publication No. US2012/0000956 A1 (which had been commonly assigned to the assignee of the present invention, and fully incorporated by reference herein) discloses a process that can be simply and reliably deployed to properly cleave optical fibers to obtain smooth ends, so as to minimize light loss when the fibers are subsequently coupled. In accordance with the disclosure, axial tension is applied to an optical fiber that had been scored at the intended cleave location, wherein the axial tension is applied in a time-varying manner to maintain the stress intensity factor for crack on the fiber within an acceptable level to produce a stable crack growth from the circumference to towards the center at a reasonable rate to cleave the fiber. Careful control of the applied tension force with time acts to control the velocity of the propagating crack by maintaining substantially constant stress intensity factor. In one embodiment, the applied axial tension force is reduced with time and/or crack growth. As a result, the strain energy in the fiber material is released by formation of a single plane with an optical quality surface without requiring polishing. A substantially flat optical surface of enhanced optical quality is formed at the cleaved end of the optical fiber. 
     To facilitate the optical fiber cleaving process such as the process disclosed in U.S. Patent Application Publication No. US2012/0000956 A1, there is a need to develop an effective, convenient and reliable scribing tool to form an initial shallow circumferential groove at the surface, which could facilitate operations in field environment as well. 
     SUMMARY OF THE INVENTION 
     The present invention provides convenient and reliable scribing tools that can effectively form an initial shallow groove at the circumferential surface of an optical fiber to facilitate cleaving operations in a factory and facilitate operations in field environment as well. The design features of the inventive scribing tool can be configured in the form of a portable, hand tool, which can be deployed for easy handling in the field. 
     In accordance with one aspect of the present invention, the scribing tool comprises a body or housing within which the optical fiber is supported for rotation with respect to the body, about an axis of the body (e.g., a central axis). The optical fiber is constrained by supports from movements along its axis. An actuator moves a scribing bit made of a hard material (e.g., diamond, sapphire or tungsten carbide) substantially orthogonal relative to the axis of the optical fiber. By rotating the optical fiber while biasing the scribing bit against the surface of the optical fiber, a shallow groove is scribed at the circumferential surface of the optical fiber. In one embodiment, the groove extends around the entire circumference of the optical fiber. In another embodiment, the groove may extend partially around the circumference of the optical fiber. 
     In another aspect of the present invention, the actuator is an electro-mechanical actuator, which may be a piezoelectric actuator (e.g., made of a piezoceramic (PZT) material), a micro-machine or a nano-machine, etc. These actuators can provide nanoscale displacements that ensure that the annular groove is cut in a ductile mode that does not cause cracking within the fiber. 
     In one embodiment, the actuator moves the optical fiber towards the scribing bit (i.e., the axis of the optical fiber moves laterally relative to the scribing tool body, or the fiber moves in a direction orthogonal to the fiber&#39;s rotation axis). In another embodiment, the actuator moves the scribing bit towards the optical fiber, with the axis of the optical fiber retained by the supports from lateral movements relative to the scribing tool body. 
     In one embodiment, the scribing tool has a single scribing bit, in which case the optical fiber is required to be rotated 360 degrees in order to form a complete circumferential groove on the surface of the optical fiber. In another embodiment, the scribing tool has multiple (N) scribing bits that can be applied against the optical fiber simultaneously, in which case the optical fiber need only be rotated by 360/N degrees to form a complete circumferential groove on the surface of the optical fiber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and advantages of the invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings. In the following drawings, like reference numerals designate like or similar parts throughout the drawings. 
         FIG. 1  is a schematic axial sectional view of a scribing tool for optical fibers, in accordance with one embodiment of the present invention. 
         FIG. 2  is a schematic axial sectional view of a scribing tool for optical fibers, in accordance with another embodiment of the present invention. 
         FIG. 3  is an end perspective view of a scribing tool, in accordance with a further embodiment of the present invention. 
         FIG. 4  is another end perspective view of the scribing tool in  FIG. 3 . 
         FIG. 5  is a front view of the scribing tool in  FIG. 3 . 
         FIG. 6  is a sectional view taken along line  6 - 6  in  FIG. 5 . 
         FIG. 7  is an end perspective of a scribing tool in accordance with a further embodiment of the present invention. 
         FIG. 8  is another end perspective view of the scribing tool in  FIG. 7 . 
         FIG. 9  is a sectional view taken along line  9 - 9  in  FIG. 8 . 
         FIG. 10  is a sectional view taken along line  10 - 10  in  FIG. 8 . 
         FIG. 11  is a sectional view taken along line  11 - 11  in  FIG. 10 . 
         FIG. 12  is a partial sectional view of a scribing tool in accordance with an alternate embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention is described below in reference to various embodiments with reference to the figures. While this invention is described in terms of the best mode for achieving this invention&#39;s objectives, it will be appreciated by those skilled in the art that variations may be accomplished in view of these teachings without deviating from the spirit or scope of the invention. 
     The inventive scribing tool is discussed in reference to a cleaving process that involves first scoring or scribing a groove into the optical fiber on its outside diameter either fully around the circumference of the fiber or in selective regions around the circumference, and then applying tension in the fiber longitudinal axis to separate two longitudinal sections of the fiber. The fiber may or may not be initially held under an axial tension when it is being scored. The score is produced mechanically by a scribing tool (also referred by some as a scoring tool). A carefully controlled scoring process provides only an initial surface groove having a desired groove depth without sub-surface damage (i.e., no cracks below the bottom surface of the scored groove); the initial groove defines the location where crack propagation across the fiber will be initiated with sufficient axial tension. Specifically, scoring of the groove produces an initial surface groove having depth of a few tens of nanometers (typically no more than 100 nanometers), whereby the scoring tool cuts the material of the fiber in a ductile mode instead of a brittle mode, thereby avoiding sub-surface cracks below the bottom of the scored grooves. Shallow depths of the cut (below few tens of nanometers) during the scoring process can be achieved by precision feeding of the scribing tool or pressing the tool against the fiber with a slight force. 
     In accordance with the present invention, a scribing tool is provided to effectively score the optical fiber to prepare the optical fiber for proper crack growth, with the above considerations and objectives in mind. The present invention provides a convenient and reliable scribing tool that can effectively form an initial shallow groove at the circumferential surface of an optical fiber to facilitate cleaving operations in a factory and could facilitate operations in field environment as well. The design features of the inventive scribing tool can be configured in the form of a portable, handheld tool, which can be deployed for easy handling in the field. 
     In accordance with one aspect of the present invention, the scribing tool comprises a body or housing within which the optical fiber is supported for rotation with respect to the body, about an axis (e.g., a central axis) of the body. The optical fiber is constrained by supports from movements along its axis. An actuator moves a scribing bit made of a hard material (e.g., diamond, sapphire or tungsten carbide) substantially orthogonal relative to the axis of the optical fiber. By rotating the optical fiber while biasing the scribing bit against the surface of the optical fiber, a shallow groove is scribed at the circumferential surface of the optical fiber. In one embodiment, the groove extends around the entire circumference of the optical fiber. In another embodiment, the groove may extend partially around the circumference of the optical fiber. 
       FIG. 1  schematically illustrates the centerline cross-section of a scribing tool in accordance with one embodiment of the present invention. In this embodiment, the scribing tool  10  comprises a body  12  that is generally cylindrical (e.g., having a circular, square, restangular or hexagonal cross-section, or cross-section of other geometries. A bore supporting the optical fiber  20  is defined in the body  12 , e.g., by ferrules supported in the body  12 . The body  12  defines a cavity including a scribing region, in which an actuator supports the optical fiber  20  for movement relative to a scribing bit  24  that is supported by an arm  25  cantilevered from the side wall  15  of the body  12 . The scribing bit  24  may be made of diamond, sapphire, tungsten carbide or other hard materials that is suitable to cut the silica or glass material of the optical fiber. 
     In another aspect of the present invention, the actuator is an electro-mechanical actuator that converts electrical signals into a mechanical displacement. In the illustrated embodiment, the actuator is a piezoelectric actuator (e.g., made of a piezoceramic material, such as PZT (lead zirconate titanate)) in the form of a cylindrical piezoelectric tube  22 , which is cantilevered at one end to the end wall  13  of the cylindrical body  12 . The other end of the piezoelectric tube  22  is not supported and is free to move with respect to the cylindrical wall  15  of the body  12 . The other end of the cylindrical wall  15  is open (i.e., not plugged or covered by an endcap). 
     As shown in  FIG. 1 , a bore supporting the optical fiber is defined in the body  12  by two cylindrical ferrules  14  and  16  that support the optical fiber  20 . (As referenced throughout herein, the optical fiber  20  refers to a bare fiber with cladding exposed without protective buffer and jacket layers, having, e.g., a 125 μm diameter.) The ferrules may be made of zirconia, metal or other materials, which has a smooth bore sized to allow the optical fiber  20  to freely rotate therein without damage to the optical fiber. Specifically, the ferrule  16  is fixedly supported at the end wall  13  of the body  12 . The ferrule  14  is fixedly supported by an endcap  23  at the free end of the piezoelectric tube  22 . This ferrule  14  is provided with an opening  18  (e.g., by machining) to allow the scribing bit  24  to access the perimeter of the optical fiber  20 . The optical fiber is constrained by supports from movements along its axis. This can be achieved by axial locking collars  27  provided at the external ends of the ferrules  14  and  16 , which are fixed to the optical fiber  20  to restrict axial movement with respect to the ferrules but does not hinder rotational movements of the optical fiber  20  within the ferrules. 
     It is known that piezoceramic actuators utilize the piezoelectric effect to convert electrical signals to a mechanical displacement. In particular, a piezoceramic PZT material expands in the direction of the electrical field when voltage is applied to it. For the piezoelectric tube  22 , a voltage is applied to one side (the lower side shown in  FIG. 1 ) of the cylindrical piezoelectric tube  22  by a servo controller  26 , which controls the expansion of that side of the piezoelectric tube  22 . Given differential axial displacement of different portions (i.e., upper and lower portions) of the piezoelectric tube  22 , this causes the piezoelectric tube  22  to bend upwards by an extent depending on the controlling voltage from the controller  26 . As the piezoelectric tube  22  bends towards the scribing bit  24 , the perimeter of the optical fiber  20  comes into contact with the scribing bit  24 . It can be seen that the ferrule  14  also acts an anvil to support the optical fiber against the pressure of the scribing bit  24 . The force of the scribing bit  24  imparted on the optical fiber  20  for scoring the optical fiber would depend on the extent of bending of the piezoelectric tube  22 . The desired force appropriate to score a groove of a desired depth may be determined and the appropriate voltage applied to the piezoelectric tube  22  to produce bending of the piezoelectric tube  22  to achieve the desired force. The scribing tool  10  can be calibrated using an optical fiber prior to placing the scribing tool  10  into operation. 
     The control of PZT tubes is well known in the art, and will not be elaborated herein. It is noted that instead of applying voltage to only one side of the cylindrical piezoelectric tube  22  (i.e., the lower side as shown in  FIG. 1 ), voltage (e.g., differential voltage) may be applied to the upper side and/or other sides or sections of the tube  12  to cause differential axial displacements of the sections, so as to result in net bending of the piezoelectric tube  22  towards the scribing bit  24 . Further, the piezoelectric tube  22  may be controlled for bending action along more than one axis, to produce bending actions to move the ferrule  14  in/out of the sheet, up/down, and left/right, as desired. 
     With the scribing bit  24  pressed against the optical fiber  20 , the optical fiber  20  would be manually or automatically rotated (e.g., by rotating the locking collars  27  manually or using an actuator not shown) within the ferrules, so that the scribing bit  24  could scribe an annular or circumferential groove around the perimeter of the optical fiber  20 . After completing scoring the groove, the scribing bit  24  may be retracted from the optical fiber by removing control voltage or applying a reverse voltage to the piezoelectric tube  22 . 
     In the embodiment of  FIG. 1 , the optical fiber  20  is generally coaxially supported within the actuator (e.g., piezoelectric tube  22 ). The actuator moves the optical fiber  20  towards the scribing bit  24  (i.e., the axis of the optical fiber  20  moves laterally relative to the wall  15  of the body  12 ) by relying on bending action of the piezoelectric tube  22 . The piezoelectric tube  22  provides support, guide and bearing for movement of the optical fiber  20 , without the need for a second set of bearing and/or support. By relying on differential axial displacements of different sections of the piezoelectric tube  22  caused by piezoelectric effect to obtain a net bending action, a small variation of the force of the scribing bit  24  on the optical fiber  20  can be achieved with the differential axial displacements. The bending action of the piezoelectric tube  22  thus provides a gentle pressure by the scribing bit  24  on the optical fiber  20 . The displacement of the ferrule  14  can be regulated with nanometer resolution providing extremely fine control of the depth of cut by the scribing bit  24 . This is important for machining the groove in a ductile mode, which typically requires depths of cut that are less than 100 nm. 
       FIG. 2  schematically illustrates a scribing tool in accordance with another embodiment of the present invention. This embodiment of the scribing tool  10 ′ shares similarity with the embodiment shown in  FIG. 1 , with the exception of the structures noted below. In this embodiment, the body  12 ′ of the scribing tool  10 ′ comprises a cylindrical wall  15 ′ and endcaps  13 ′ and  19  fully enclosing the cavity defined in the body  12 ′, thus fully enclosing piezo actuator tube  22  and scribing region. Three ferrules  14 ,  16  and  17  are shown supporting the optical fiber  20 . The ferrule  16  is fixedly supported by the endcaps  13 ′ plugged (e.g., by a threaded coupling) at one end of the cylindrical body  12 ′. The additional ferrule  17  is fixedly supported by the endcap  19  plugged (e.g, by a threaded coupling) at the other end of the cylindrical body  12 ′. Instead of supporting the scribing bit  24  by a cantilevered arm, the scribing bit  24  is supported by structure  25 ′ extending from the cylindrical body  12 ′ by a variable attachment (e.g., a threaded attachment). The threaded attachment provides adjustments to set the initial or nominal location the scribing bit  24  close to the optical fiber  20  prior to initiating scribing operation by bending the piezoelectric tube  22 . This allows for periodic adjustments or replacement of the scribing bit  24  to accommodate wear of the scribing bit. The displacement of the piezoelectric tube  22  is controlled by servo controller  26 ′ as in the case of the embodiment in  FIG. 1 . In this embodiment, a displacement sensor  32  is provided which measures the displacement at the end of the piezoelectric tube  22  as a feedback signal to the controller  26 ′. This would provide for continuous adjustment under prescribed control of the depth of cut in the optical fiber  20 . Furthermore, the displacement of the piezoelectric tube  22  may be synchronized with the rotation of the optical fiber  20 . The embodiment of  FIG. 1  may be modified to provide similar displacement sensor and associated controller. 
     While the above discussed embodiments illustrate scribing tools having a single scribing bit, it is well within the scope and spirit of the present invention to provide additional scribing bits that can be sequentially or simultaneously applied to the rotating optical fiber. For example, in the embodiment of  FIG. 2 , it may be further modified to provide two or more scribing bits (not shown) that are circumferentially distributed (e.g., axially symmetrically or evenly distributed by equal radial angular spacing) with respect to the optical fiber axis. The piezoelectric tube  22  is controlled to displace radially away from the fiber axis in a manner to press the scribing bits against the optical fiber, with each scribing bit scoring a circumferential segment around the optical fiber. The depth of cut for the scribing tools is controlled by the piezoelectric tube  22 . The displacement sensor  32  detects the position and displacement of the optical fiber. Instead of having to rotate the optical fiber by 360 degrees in order to form a complete circumferential groove on the surface of the optical fiber using a single scribing bit as in the case of  FIGS. 1 and 2 , by using N number of scribing bits in the present embodiment, the optical fiber need only be rotated by 360/N degrees to form a complete circumferential groove on the surface of the optical fiber. This is very advantageous when the opposite end of the optical fiber may be wound on a coil or attached to another device. 
       FIGS. 3 to 6  schematically illustrate a scribing tool in accordance with further embodiment of the present invention. This embodiment represents a product implementation including additional modifications to the embodiments of  FIGS. 1 and 2  discussed above, and more particularly  FIG. 1 . Otherwise, the structure and operation that implements displacement of the optical fiber in this embodiment is quite similar to the earlier embodiments. 
     In this embodiment, the scribing tool  110  comprises a body or housing  112  having a generally cylindrical wall  115 , with a flat surface  142  at one side, and openings  140  provided in the curved sections of the wall  115 . The openings  140  provide ventilation for heat built up at the interior of the body  112 , and access to the interior of the body  112  (e.g., passage of electrical wiring). The body  112  defines a cavity, in which an actuator supports the optical fiber  20  for movement relative to a scribing bit  124  that is supported by an arm  125  cantilevered from the wall  115  of the body  112 . Unlike the embodiment of  FIG. 1 , the arm  125  is fixed in position, by locking set screw  146 , with respect to the base plate  144  that is fastened to the end of the body wall  115 . This allows flexibility for adjustments to set the initial or nominal location of the scribing bit  124  with respect to the optical fiber  20  prior to a scribing operation. This also allows for easy replacement of the scribing bit  124  and/or its support arm  125 . 
     The actuator is a piezoelectric actuator in the form of a cylindrical piezoelectric tube  122 , which may be similar to the tube  12  in  FIG. 1 . The tube  122  is cantilevered at one end to the end wall  113  attached to one end of a cylindrical wall  115  by bolts  150 . The other end of the tube  122  is not supported and is free to move with respect to the cylindrical wall  115  of the body  112 . The other end of the cylindrical wall  115  is open (i.e., not plugged or covered by an endcap). 
     As better shown in  FIG. 6 , two cylindrical ferrules  114  and  116  supports the optical fiber  20 . Specifically, the ferrule  116  is fixedly supported at the end wall  113  of the body  112 . The ferrule  114  is fixedly supported by an endcap  123  at the free end of the tube  122 . This ferrule  114  is provided with an opening  118  (e.g., by machining) to allow the scribing bit  124  (e.g., a diamond bit) to access the perimeter of the optical fiber  20 . The optical fiber is constrained by supports from movements along its axis. This is achieved by axial locking collars  127 A and  127 B providing at the external ends of the ferrules  114  and  116 , which clamp the optical fiber  20  to restrict axial movement with respect to the ferrules but do not hinder rotational movements of the optical fiber  20  within the ferrules. In this embodiment, the locking collar  127 B at one end is biased by a compression spring  130 , which applies a slight tension to the optical fiber  20 , pulling the optical fiber  20  to keep the collar  127 A against the endcap  123 . Under bias of the spring  130 , the collar  127 B is slightly spaced apart from the stub  148  that extends from the end wall  113 , and is free to rotate within the coil spring  130 . 
     A voltage is applied to one side (the lower side shown in  FIG. 1 ) of the cylindrical tube  122  by a servo controller  26 , which controls the expansion of that side of the tube  122 . Given differential axial displacement of different portions (i.e., upper and lower portions) of the tube  122 , this causes the tube  122  to bend upwards by an extent depending on the controlling voltage from the controller  126 , as was in the case of  FIG. 1 . The scribing tool is used to score a groove around the perimeter of the optical fiber  20  in a similar manner as in the case of  FIG. 2 , which will not be repeated here. It is noted that the user rotates the optical fiber  20  by turning the collars  127 A and  127 B (manually or using an actuator not shown). The flat surface  142  provides a convenient reference surface against which the body  112  is prevented from rotating when the collars  127 A and  127 B are rotated. For example, the flat surface  142  is placed on a support surface, such as a work table or an external bracket (not shown), when the collars  127 A and  127 B are turned. 
     In a further embodiment, instead of moving the optical fiber towards the scribing bit, the actuator moves the scribing bit towards the optical fiber, with the axis of the optical fiber retained by the supports from lateral movements relative to the scribing tool body. 
       FIGS. 7-11  illustrate a scribing tool in accordance with such further embodiment.  FIGS. 7 and 8  are perspective external views of a scribing tool  210 . In this embodiment, there are three scribing bits (i.e., N=3) applied to the optical fiber  20 .  FIG. 9  is a sectional view taken along line  9 - 9  in  FIG. 8 ;  FIG. 10  is a sectional view taken along line  10 - 10  in  FIG. 8 ; and  FIG. 11  is a sectional view taken along line  11 - 11  in  FIG. 10 . 
     The scribing tool  210  has a generally cylindrical body  212  and a collar  250  attached to one end of the body. The body  212  has a generally solid interior, with a small fiber scribing region  260  defined within the body, and a bore along its axis supporting the optical fiber  20  through the scribing region  260 . The body  212  having the bore  211  essentially functions as a ferrule supporting the length of the optical fiber through the scribing region  260 . The optical fiber  20  is constrained by supports from movements along its axis. This can be achieved by axial locking collars  227  (schematically represented by dotted lines) provided at the external ends of the body  212 , which may have similar structure as the collars  27  or  127  in the previous embodiments. The collars  227  are fixed to (e.g., clamped onto) the optical fiber  20  to restrict axial movement with respect to the ferrules but does not hinder rotational movements of the optical fiber  20  within the ferrules. The fiber may be rotated by turning the collars  227 . 
     The scribing region has three channels  270  opened to the sides of the cylindrical body  212 , which allow access by scribing bits  224  supported at the tip of arms  225 . There is sufficient clearance provided between each arm and the walls of the channel  270  to allow free movement of the arm. The channels  270  extend radially from scribing region, at equal angular spacing, receiving the arms  225 . 
     In this embodiment, there are as many flexible supports  251  as the number of scribing bits  224 , which are attached to the exterior of the cylindrical body  212 . The flexible supports are distributed at equal radial angular spacing about the circumference of the body  212 . In the illustrated embodiment, each flexible support  251  comprises two cantilevered flexible thin plates  252 , which are separated by and clamped onto a block  253 . The flexible support  251  is attached to the body  212  by fasteners  254 . At the end of the flexible support  251  towards the channel  270 , a U-shaped yoke  256  is attached between the plates  252 . The yoke  256  has a cutout  271  (which defines the opening in the U-shaped yoke), which receives the arm  225 . The arm  225  is secured to the yoke by a set screw  257 , which allows flexibility for adjustment and fixing the initial (or nominal) position of the scribing bit  224  with respect to the optical fiber  20 , prior to activating the actuator to implement scribing operation. In the illustrated embodiment, all the flexible supports  251  are identical. 
     The collar  250  has a cylindrical base  263  and fingers  262  extending therefrom. There are as many fingers  262  as there are scribing bits  224 /arms  225 . The cylindrical base  263  is inserted over the cylindrical body  212 , exposing section  264  of the body  212 . However, the base  263  and/or the body  212  may be sized so that there is the portion  264  is not exposed by the base  263 . Each finger  262  extends over the end of a channel  270 /arm  225  (i.e., the finger  262  is position along the axis of the channel  270 /arm  225 ). 
     In the illustrated embodiment, the actuator to displace the scribing bit  224  relative to the optical fiber  20  is supported between the finger  262  and the end of the arm  225 . Specifically in this embodiment, the actuator at each finger  262  is in the form of a piezo element  280 , which is configured with electrical inputs not specifically shown in the figures, but schematically shown in  FIG. 10  by dotted line  277  leading to a controller  226 . The piezo element  280  is configured to expand/contract in reference to the supporting finger  262 , to displace the arm at least in the direction of the axis of the arm  225 , to press against or retract from the optical fiber  20 . The scribing bits  224  are actuated by the piezo elements  280  to move in a direction radially with respect to the optical fiber  20  or its rotation axis. 
     Scribing operation is undertaken by appropriately controlling the displacements of the piezo elements for the arms  225 /scribing bits  224 . The optical fiber  20  is rotated by turning the collars  227  that are clamped to the fiber at the ends of the bore. 
     While it is not shown in the figures, a suitable cover may be provided to protect some of the structures external of the body  212  (e.g., the flexible supports  251 ) for easy handling of the scribing tool at the field. 
     In one embodiment, the optical fiber  20  is generally coaxially supported within the ring of actuators (e.g., piezo elements  280 ) located about the axis of the optical fiber  20 . The rotational axis of the optical fiber  20  is substantially aligned with the center (e.g., center of gravity, center of mass, centroid, geometric center) of the overall body  212  of the scribing tool  210 . As referred herein, substantially aligned means alignment of the spin axis and one of the centers is within 0-25%, or 0-15%, or 0-10%, or 0-5% of the characteristic diameter of the body  212 . This facilitates rotation of the body  212  with respect to the optical fiber  20  (e.g., holding the fiber  20  stationary and rotating the body  212 ), as the scribing would be better balanced to avoid wobbling of the body as it is being rotated about the fiber (which could lead to unintended breakage of the fiber). Further, the body  212  of the scribing tool  210  can be configured with structural features that are substantially axial symmetric, so that a more balanced weight distribution to facilitate turning of the body. This makes handling of the scribing tool  210 , if it is implemented as a hand tool, much easier in the field. The same design consideration and structural configurations implementing the above discussed alignment requirement can apply to the earlier embodiments discussed above in reference to  FIGS. 1-6 , as an alternate embodiment. 
     In the multi-scribing bit embodiment of the inventive scribing tool disclosed above, the scribing tool has multiple (N) scribing bits that can be applied against the optical fiber simultaneously, in which case the optical fiber need only be rotated by 360/N degrees to form a complete circumferential groove on the surface of the optical fiber. This reduces the relative angle through which the fiber and tool must be rotated. This is very beneficial for field termination, where a long cable may not easily be rotated multiple times or even 360 degrees. 
     It can be appreciated that each flexible support  251  having the yoke  256  provides a floating structure to facilitate adjustments to set initial alignment and to maintain set alignment of the arm  225  in a direction parallel to the fiber axis and its orthogonal direction within the channel  270 , as well as to support the arm to set the nominal position of the arm  225  that supports the scribing bit  224 . In essence, the flexible support  251  provides a flexible or spring bearing for the supported arm  225 . Without the flexible support  251 , the lateral and vertical alignments of the arm  225  would rely entirely on the support of the piezo element  280 , which might challenge the structural integrity of the assembly, since the arm  225  would be cantilevered from the fingers via the piezo element  280 . As the piezo element  280  displaces the arm towards the optical fiber  20 , the extension of the piezo element  280  acts against the backing support of the finger  262  and the bias of the flexible support  251 . Upon retracting the piezo element, the spring support  251  also facilitates retracting the arm  225  away from the optical fiber  20 . 
     Scribing is achieved by axial locking collars  127 A and  127 B providing at the external ends of the ferrules  114  and  116 , which clamp the optical fiber  20  to restrict axial movement with respect to the ferrules but do not hinder rotational movements of the optical fiber  20  within the ferrules. 
       FIG. 12  is the same partial sectional view taken along the same section in comparison to  FIG. 11  (with the portion  264  of the body  212  not shown), which illustrates an alternate embodiment in which the collar  250  in the prior embodiment can be omitted. In this embodiment, instead of providing a piezo element at the end of the arm  225 , the yoke  256 ′ is made of a piezo material. Accordingly, the yoke  256 ′ provides support for alignment, as well as actuation of the arm  225  for scribing the optical fiber  20 . All other structures are similar to the previous embodiment. 
     In a further embodiment not illustrated, there may be more or less spring plates in the flexible support than as shown. For example, there may be a single spring plate  252  in the support, which may be cantilevered either on top or below the block  253 , or intermediate between two blocks (not shown). 
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     While the invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit, scope, and teaching of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited in scope only as specified in the appended claims.