Abstract:
Provides a method and a terminus processing tool whereby terminus processing for the purpose of connection to another optical fiber may be carried out simply. The terminus processing method entails cutting an optical fiber  20  composed of a glass fiber  21  and a coating  24 ; and with the optical fiber  20  positioned relative to a terminus processing tool that is disposed contacting the coating at the end surface of the optical fiber  20  and that has a protruded-into space for accommodating inward protrusion of the glass fiber  21 , and with the cut end surface of the glass fiber  21  facing the protruded-into space, pushing the optical fiber  20  to thereby strip the coating  24  from the glass fiber  21.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method for stripping a coating from the terminus of an optical fiber composed of a glass fiber and a coating, and to a terminus processing tool used in the method. 
       BACKGROUND ART 
       [0002]    When connecting an optical fiber composed of a glass fiber and a coating to another optical fiber, it is known to strip a prescribed length of the coating of the terminus in order to expose the glass fiber. The operation of stripping the coating is carried out using a mechanical stripper, for example (see Japanese Unexamined Patent Application 60-79306). 
         [0003]      FIG. 7  is a perspective view showing a conventional stripper  100 . The stripper  100  is composed of an upper member  101  and a lower member  102  that are pivoted at one edge. Clamps  105 ,  106  are respectively disposed within core guide portions  103 ,  104  which are provided to the upper member  101  and the lower member  102 . A pair of core guide claws  107 ,  107  are disposed on the lower member  102 , and slots (not shown in the drawing) that mate with the core guide claws  107  are provided in the upper member  101 . Blades  108 ,  109  situated in opposition to one another are disposed on the upper member  101  and the lower member  102 . 
         [0004]    When the stopper  100  is used to strip the coating from an optical fiber, the optical fiber is guided by the core guide claws  107  and positioned at the location of the clamps  105 ,  106 . In this state, the upper member  101  and the lower member  102  are urged into relative proximity with one another, whereby the blades  108 ,  109  slice into the coating that is to be stripped from the optical fiber, producing a cut. The coating is then stripped by moving the stripper  100  relative to the optical fiber. 
         [0005]    According to this method, the coating is stripped by pressing the blades  108 ,  109  against the coating of the optical fiber, followed by relative motion of the stripper  100  towards the end of the optical fiber. For this reason, coating residue may be left adhering to the end of the optical fiber. Because cutting cannot be carried out in consistent fashion with coating residue adhering to the end of the optical fiber, it was necessary to either cut off the end or clean it with alcohol or the like, resulting in a complicated procedure.
   Patent Citation 1: Japanese Unexamined Patent Application 60-79306   
 
       DISCLOSURE OF THE INVENTION 
     Technical Problems 
       [0007]    It is an object of the present invention to provide a method whereby terminus processing for the purpose of connection to another optical fiber may be carried out straightforwardly, as well as a terminus processing tool for use in the method. 
       Means Used to Solve the Above-Mentioned Problems 
       [0008]    The method of processing a terminus of an optical fiber according to the present invention includes: (1) cutting an optical fiber composed of a glass fiber and a coating; and (2) pushing the optical fiber against a terminus processing tool and thereby removing the coating from the glass fiber, the terminus processing tool being adapted to contact the coating at an end surface of the optical fiber, and having a space into which the glass fiber is inserting; and the coating being removed in a state wherein the cut end of the optical fiber is inserted-into the space. 
         [0009]    Optionally, the space to which the glass fiber is inserting is a hole with diameter larger than an outside diameter of the glass fiber and smaller than an outside diameter of the coating. In this case, it is preferable for the inside distal end portion of the hole to be chamfered. Where the coating is composed of two or more layers, it is preferable for the inside distal end diameter of the hole to be smaller than the outside diameter of the coating of the innermost layer of the coating of two or more layers. Additionally, it is preferable for the inside diameter of the hole to be progressively smaller in a direction in which the optical fiber is inserted. 
         [0010]    In preferred practice, an initial flaw is formed, between the cutting step and the stripping step, in the outside peripheral portion of the coating. In this case, optionally, a plurality of initial flaws are formed in the circumferential direction on an outside peripheral face of the coating. 
         [0011]    Optionally, the space is a concave portion with diameter larger than the outside diameter of the glass fiber and smaller than the outside diameter of the coating. 
         [0012]    The terminus processing tool according to the present invention is adapted to contact a coating at an end surface of an optical fiber composed of a glass fiber and the coating, and having a space into which the glass fiber is inserting. 
       Advantageous Effect of the Invention 
       [0013]    According to the present invention, it is possible to prevent coating residue from adhering to the end surface of a glass fiber when the coating is stripped by blades traveling towards the end of the optical fiber as practiced in the prior art, thereby obviating the need for a cleaning procedure in a step subsequent to stripping the coating. Consequently, terminus processing for the purpose of connection to another optical fiber may be carried out straightforwardly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a cross sectional view showing part of an optical fiber terminus processing tool according to a first embodiment of the invention, together with the optical fiber being processed. 
           [0015]    In  FIG. 2 , area (A) and area (B) are respectively enlarged fragmentary views showing the distal end portion of a hole in the terminus processing tool of the first embodiment. 
           [0016]    In  FIG. 3 , area (A) is a cross sectional view of an optical fiber provided with initial flaws in the coating, and area (B) is a front view thereof. 
           [0017]      FIG. 4  is a drawing illustrating terminus processing of an optical fiber provided with initial flaws in the coating, wherein area (A) is a cross sectional view of the optical fiber prior to processing, and area (B) is a cross sectional view of the optical fiber subsequent to processing. 
           [0018]      FIG. 5  is a cross sectional view showing a modification of the terminus processing tool of the first embodiment. 
           [0019]      FIG. 6  is cross sectional view showing part of an optical fiber terminus processing tool according to a second embodiment of the invention, together with the optical fiber being processed, wherein area (A) shows the state prior to processing, and area (B) shows the state subsequent to processing. 
           [0020]      FIG. 7  is a perspective view showing a conventional optical fiber coating stripping device (stripper). 
       
    
    
       [0021]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                 KEY TO SYMBOLS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10: 
                 terminus processing 
                   
                   
                 11: 
                 circular gap 
               
               
                   
                 tool, 
                   
                   
                   
                 (space), 
               
               
                 12: 
                 chamfering, 
                 15: 
                 concave 
                 20: 
                 optical fiber, 
               
               
                   
                   
                   
                 portion 
               
               
                   
                   
                   
                 (space), 
               
               
                 20a: 
                 end surface, 
                 21: 
                 glass fiber, 
                 22: 
                 first coating 
               
               
                   
                   
                   
                   
                   
                 layer, 
               
               
                 24: 
                 coating, 
                 24a: 
                 end surface 
                 25, 26: 
                 initial flaws, 
               
               
                   
                   
                   
                 of coating, 
               
               
                 D1: 
                 circular gap 
               
               
                   
                 diameter, 
               
               
                 d1: 
                 outside diameter of 
               
               
                   
                 optical fiber 
               
               
                   
                 (outside diameter 
               
               
                   
                 of coating), 
               
               
                 d2: 
                 outside diameter of 
               
               
                   
                 first coating layer, 
               
               
                 d3: 
                 outside diameter of 
               
               
                   
                 glass fiber 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The embodiments of the present invention are described below with reference to the drawings. The drawings are intended for illustrative purposes, and are not limiting of the invention. In the drawings, in order to avoid redundant description, like symbols indicate like components. Dimensional proportions in the drawings are not necessarily accurate. 
         [0023]      FIG. 1  is a cross sectional view showing part of an optical fiber terminus processing tool  10  according to a first embodiment of the invention, together with an optical fiber  20  being processed. In the terminus processing method using the terminus processing tool  10 , first, the optical fiber  20 , which is composed of a glass fiber  21  and a coating  24 , is cut with the coating  24  still attached. Next, the end surface  24   a  of the coating  24  at the cut end surface  20   a  of the optical fiber  20  is pressed against the terminus processing tool  10 . By so doing, the coating  24  is peeled and stripped from the glass fiber  21 . 
         [0024]    In the optical fiber  20 , the outside diameter d 3  of the glass fiber  21  is, e.g., 125 μm; and the outside diameter d 1  of the coating  24  is, e.g., 25 μm. The glass fiber  21  is a glass fiber having a core and one or more cladding layers, and it is also possible to employ glass fibers of any refractive index distribution, such as single mode fibers or multi-mode fibers. 
         [0025]    The coating  24  has a first coating layer  22  having an outside diameter d 2  and being in contact with the glass fiber  21 , and a second coating layer  23  serving as a sheath covering the exterior of first coating layer  22 ; however, the coating  24  is not limited to this arrangement, and configurations having a single layer or more than two layers are also possible. A tinted layer may be provided as the outermost layer. The resin constituting the coating  24  is a UV curing type resin such as urethane acrylate, and using additives is imparted with properties such as appropriate elasticity. For example, the first coating layer  22  which contacts the glass fiber  21  has lower elasticity (i.e., softness) than the second coating layer  23 . 
         [0026]    The terminus processing tool  10  is adapted to contact the end surface  24   a  of the coating  24 , and has a gap  11  which serves as a space for accommodating inward protrusion of the glass fiber  21  when the optical fiber  20  is pressed against the terminus processing tool  10 . By forming an outer wall  14  of round tubular shape at the end of the terminus processing tool  10 , it is possible to support the optical fiber  20  during insertion, thereby minimizing the likelihood of buckling when the optical fiber  20  is inserted into the gap  11 , to afford insertion of the optical fiber  20  into the gap  11  in an easy and reliable manner. 
         [0027]    It is possible, for example, for the gap  11  to be a circular gap, a square gap, or a regular polygon shaped gap, or a gap having serrated contours at its perimeter; here, a circular gap is described as a preferred example. With a circular gap, forces tend to act uniformly in the circumferential direction of the optical fiber  20 . It is good for stripping of the coating. The inside diameter D 1  of the gap  11  is larger than the outside diameter d 3  of the glass fiber  21 , and smaller than the outside diameter d 1  of the coating  24  (i.e., the outside diameter of the optical fiber  20 ). When the end surface  20   a  of the optical fiber  20  is pressed against the perimeter of the gap  11  of the terminus processing tool  10 , the distal end portion  11   a  of the gap  11  contacts the end surface  24   a  of the coating  24 , but does not contact the glass fiber  21 . 
         [0028]    Preferably, the inside diameter of the distal end portion  11   a  of the gap  11  is smaller than the outside diameter d 2  of the first coating layer  22  that makes up the coating  24 , and greater than the outside diameter d 3  of the glass fiber  21 . By so doing, when the optical fiber  20  is pressed against the terminus processing tool  10 , force can act directly on the first coating layer  22 , and the coating  24  can be completely stripped from the glass fiber  21 . Further, the taper angle of the taper portion  11   a  (the angle to the center axis of the gap  11 ) θ 1  is preferably from 30° to 90°. The coating  24  can be easily peeled towards the outside thereby. 
         [0029]    In  FIG. 2 , area (A) and area (B) are enlarged fragmentary views showing the distal end portion of a gap in the terminus processing tool  10 . In preferred practice, the inside distal end portion  11   a  of the gap  11  is chamfered. For example, a chamfer having an arcuate curving face (rounded chamfer  12   a ) as shown in area (A) may be provided. Alternatively, a chamfer having a linear flat face (45° chamfer  12   b ) as shown in area (B) may be provided. This makes it easy to insert the optical fiber  20  into the gap  11  of the terminus processing tool  10 . The inside diameter D 2  of the large-diameter end  13  of the chamfer  12  at the distal end of the gap  11  is smaller than the outside diameter d 2  of the first coating layer  22  that makes up the coating  24 , and greater than the outside diameter d 3  of the glass fiber  21 . 
         [0030]    In  FIG. 3 , area (A) is a cross sectional view of an optical fiber  20  provided with initial flaws in the coating, and area (B) is a front view thereof. In preferred practice, the outside peripheral portion at the distal end of the coating  24  is provided with initial flaws  25 . The initial flaws  25  may be formed in the coating  24  beforehand, or formed during the terminus processing step. Preferably, the initial flaws  25  are disposed at multiple equidistant locations (four are shown in  FIG. 3 ) on the outside peripheral face of the coating  24  and are provided with prescribed length which is shorter than the terminus processing length in the axial direction (about 0.5 to 1 mm, for example). The initial flaws  25  may be given a “V” shaped cross section, for example, or may be provided by simple cuts. This facilitates outward peeling of the coating  24 , whereby the coating  24  may be easily stripped. 
         [0031]      FIG. 4  is a drawing illustrating terminus processing of the optical fiber  20  provided with initial flaws in the coating, wherein area (A) is a cross sectional view of the optical fiber prior to processing. An initial flaw  26  that is continuous in the circumferential direction of the optical fiber  20  may be disposed at a location a prescribed distance from the end surface  20   a  of the optical fiber  20 , for example, one equal to the terminus processing length. Optionally, the initial flaw  26  is a cut that slices inward towards the end of the optical fiber  20 .  FIG. 4  area (B) is a cross sectional view of the optical fiber subsequent to processing. When the optical fiber  20  is pressed against the gap  11  of the terminus processing tool  10 , the coating  24   b  at the end is pressed in the rightward direction in the drawing and spreads outwardly along the initial flaw  26 , whereby the coating  24   b  can be easily stripped. Moreover, by setting the location of the initial flaw  26  to one equal to the terminus processing length from the end surface  20   a , the desired length of the coating  24  can be stripped. 
         [0032]      FIG. 5  is a cross sectional view showing a modification of the terminus processing tool of the first embodiment. The gap  11  is provided with a tapered portion  11   b  of progressively smaller inside diameter towards the inside from the distal end surface of the terminus processing tool  10 . The inside diameter of the tapered portion  11   b  at the distal end portion  11   a  is smaller than the outside diameter d 1  of the optical fiber  20  and larger than the outside diameter d 3  of the glass fiber  21  of the optical fiber  20 . Also, it is preferable for the inside diameter at the distal end portion  11   a  to be smaller than d 2 , so that the distal end portion  11   a  contacts the first coating layer  22 . The taper angle of the tapered portion  11   b  (the angle to the center axis of the gap  11 ) θ 2  is preferably from 0° to 30°. 
         [0033]    When the optical fiber  20  is pressed against the terminus processing tool  10 , the end surface  24   a  of the coating  24  contacts the distal end portion  11   a , the coating  24  peels away from the glass fiber  21 , and the tip of the glass fiber  21  pushes into the gap  11 . Because the optical fiber  20  is inserted along the tapered portion  11   b , positioning of the distal end of the optical fiber  20  can be carried out with high accuracy. 
         [0034]    According to the optical fiber terminus processing method and terminus processing tool  10  described above, it is possible to prevent coating residue from adhering to the end surface of the glass fiber  21  when the coating  24  is stripped by blades traveling towards the end of the optical fiber  20  as practiced in the prior art, thereby obviating the need for a cleaning procedure in a step subsequent to stripping the coating  24 . Consequently, terminus processing for the purpose of connection to another optical fiber may be carried out straightforwardly. The material of the terminus processing tool  10  is preferably a ceramic such as zirconia, or a resin material such as an epoxy resin or polyphenylene sulfide resin. 
         [0035]      FIG. 6  is a cross sectional view showing part of an optical fiber terminus processing tool  10 B according to a second embodiment of the invention, together with the optical fiber being processed, wherein area (A) shows the state prior to processing. The terminus processing tool  10 B has a concave portion  15  of inside diameter larger than the outside diameter d 3  of the glass fiber  21  of the optical fiber  20 , and smaller than the outside diameter d 1  of the optical fiber  20 .  FIG. 6  area (B) shows the state subsequent to processing. When the end surface of the optical fiber  20  is pressed against the concave portion  15  of the terminus processing tool  10 B, the distal end of the coating  24  peels away outwardly, and the tip of the glass fiber  21  protrudes from the coating  24  and is enclosed within the concave portion  15 . 
         [0036]    The present application claims priority on the basis of a Japanese Patent Application (Japanese Unexamined Patent Application 2007-137171) applied for on 23 May 2007, the content of which is incorporated herein by reference. 
       INDUSTRIAL APPLICABILITY 
       [0037]    The invention is useful as a terminus processing method and a processing tool prior to securing an optical fiber to an optical connector.