Abstract:
A method and apparatus for mechanically splicing a pair of optic fibers or optic cables, the mechanical splice comprising: a ferrule having an axial capillary bore, the capillary bore configured to enclose the optic fibers at both ends of the ferrule; and cured epoxy disposed to secure together the ends of the optic fibers and to secure the optic fibers to an inside surface of the capillary bore, the ferrule optionally enclosed in a metal tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a divisional of patent application Ser. No. 12/004,880 entitled “Method and apparatus for mechanically splicing optic fibers,” filed 24 Dec. 2007 now U.S. Pat. No. 7,918,612, which in turn claims the benefit of Provisional Patent Application No. 60/924,692 entitled “Compact and curable work station for fiber splice,” filed 29 May 2007, both of which are incorporated by reference herein in their entirety for all purposes. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. N68335-05-C-0308 awarded by the U.S. Department of the Navy. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to optic fiber splicing and, in particular, to a method and apparatus for mechanically splicing optic fibers. 
     2. Description of the Background Art 
     Fusion splicing of optic fiber has been utilized in connecting optic fibers for a wide variety of optic devices, and has also been used for the installation of fiber spans for telecommunications networks. In most such application, the fusion splicing process is preferred over other methods to achieve minimum insertion loss and long term reliability. However, for some applications a mechanical splicing process may present a low-cost and convenient alternative that can accommodate many types of optic fibers. In particular, the mechanical splicing alternative is often the preferred choice for applications in which the work environment presents a fire or explosive hazardous, such as in an aircraft, around oil stations, and in mines. In such hazardous applications, the use of a high-voltage fusion splicing device is typically prohibited for safety reasons. 
     Optic fiber mechanical splicing devices are known in the prior art. Conventional mechanical splicers are typically based on a V-groove seating configuration and, accordingly, are typically used only for temporary fiberoptic connections because of associated unproven long term reliability concerns. With respect to these reliability concerns, two primary long-term failure mechanisms have been identified in optic fiber components: material deterioration caused by prolonged humidity exposure and joint fatigue caused by extended thermal cycling induced stress as well as relative movement between subcomponents. These two failure mechanisms need to be addressed in the industry if the fundamental design objectives are to realize a twenty-five year component operation life and high reliability fiberoptic components. 
     The process of optic fiber splicing typically includes several manual steps and involves extensive fiber handling among multiple pieces of processing equipment. The fiber splicing preparation may include: fiber stripping, fiber tip cleaning, fiber cleaving, fiber aligning, fiber securing and fiber splice packaging. Each of these process steps requires manual loading, unloading, and other manual process steps. The manipulation and handling of the fibers throughout these process steps compromises fiber strength and may lead to failure during subsequent use. 
     What is needed is a method and apparatus using an integral precision fiber alignment feature to easily and quickly produce a permanent mechanical splice for optic fibers. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, device for mechanically splicing a first optic fiber to a second optic fiber comprises: a ferrule having an axial capillary bore, the capillary bore configured to enclose the first optic fiber at a first end of the ferrule and to enclose the second optic fiber at a second end of the ferrule; and cured epoxy disposed to secure an end of the first optic fiber to an end of the second optic fiber, the cured epoxy further disposed to secure the first optic fiber and the second optic fiber to an inside surface of the capillary bore. 
     In another aspect of the present invention, an apparatus for splicing a first optic fiber to a second optic fiber comprises: a first clamp secured to the first optic fiber; a second clamp secured to the second optic fiber, the first and second clamps for retaining an end of the first optic fiber against an end of the second optic fiber; and an ultraviolet light source disposed to irradiate epoxy disposed between the end of the first optic fiber and the end of the second optic fiber. 
     In another aspect of the present invention, a method for splicing optic fibers comprises the steps of: providing epoxy in a capillary bore of a ferrule; placing an end of a first optic fiber against an end of a second optic fiber in the epoxy inside the capillary bore; and curing the epoxy. 
     The additional features and advantage of the disclosed invention is set forth in the detailed description which follows, and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described, together with the claims and appended drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatical illustration of two optic fibers secured within a ferrule to form a mechanical splice shown in partial cross section, in accordance with the present invention; 
         FIG. 2  is a cross-sectional diagrammatical illustration of the mechanical splice of  FIG. 1  showing a square capillary bore with four micro channels in the ferrule; 
         FIG. 3  is a cross-sectional diagrammatical illustration of an alternative embodiment of the mechanical splice of  FIG. 1  showing a triangular capillary bore with three micro channels in the ferrule; 
         FIG. 4  is a simplified diagram of one embodiment of a workstation having an ultraviolet light module suitable for fabricating the mechanical splice of  FIG. 2 , in accordance with the present invention; 
         FIG. 5  is a diagrammatical illustration of the ultraviolet light module of  FIG. 4  showing a cylindrical lens used to direct ultraviolet light; 
         FIG. 6  is a side view of a portion of an alternative embodiment of a UV module for the workstation of  FIG. 4 ; 
         FIG. 7  is a diagrammatical illustration of the ultraviolet light module of  FIG. 6  showing a reflector used to direct ultraviolet light; 
         FIG. 8  is a cross-sectional diagrammatical illustration of an alternative embodiment of the mechanical splice of  FIG. 1  showing an oval capillary bore with two micro channels in the ferrule; 
         FIG. 9  is a cross-sectional diagrammatical illustration of an alternative embodiment of the mechanical splice of  FIG. 1  showing an elongated capillary bore with one micro channel in the ferrule; 
         FIG. 10  is a cross-sectional diagrammatical illustration of an alternative embodiment of the mechanical splice of  FIG. 1  showing a ferrule with an offset section; 
         FIG. 11  is a cross-sectional diagrammatical illustration of the mechanical splice of  FIG. 10  showing a triangular capillary bore having relaxed fabrication tolerances; 
         FIG. 12  is a cross-sectional diagrammatical illustration of an alternative embodiment of the mechanical splice of  FIG. 10  showing a square capillary having relaxed fabrication tolerances; 
         FIG. 13  is an alternative embodiment of the mechanical splice of  FIG. 1  showing a metal tube enclosing the ferrule; and 
         FIG. 14  is a flow diagram explaining a process for fabricating the mechanical splices of  FIGS. 1 and 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
     The present invention is a method and apparatus for efficiently producing a permanent, high reliability mechanism splice for optic fiber applications. The disclosed mechanical splice design has been shown to successfully pass standard industry environmental tests, including vibration and thermal shock, to qualify for permanent installation application. Moreover, the disclosed design uses a glass seal technology to permanently encapsulate components in a ferrule. For more demanding environmental conditions, or for application to fiber cable designs, a metal tube may be positioned and crimped to enclose the ferrule to withstand tensile forces in the optic fiber cable. 
     This feature provides high reliability even when humidity is a concern, for example, as exemplified by having successfully passed high pressure autoclave humidity testing of 120° C. and 100% relative humidity for a one week cycle. In addition, the disclosed mechanical splice design uses glass material with a coefficient of thermal expansion matched to the optic fibers to mitigate or eliminate the progressive damage caused by thermal cycling, and to provide temperature stability performance. 
     The disclosed ferrule design provides passive precision self-alignment for an inserted optic fiber core and guided fiber insertion. The ferrule comprises a material substantially transparent to ultraviolet radiation to allow for an integrated ultraviolet epoxy curing capability. One design feature of the disclosed fiber guide ferrule allows for the insertion of polyimide-coated fiber directly without the need to first strip the hard resin buffer material layer. This approach is versatile and applies to a wide variety of the fibers found in military aviation including both multi-mode and single-mode fibers. The ferrule includes a non-circular capillary bore forming one or more axial micro channels when the optic fibers are inserted. The micro channels allow an outflow of excess epoxy and air bubbles when two optic fibers are inserted into the epoxy contained in the ferrule. By using refractive index matching of the epoxy and ferrule, and by applying an axial load to minimize the space between the ends of the two optic fibers, an extremely low optic loss can be achieved between the fibers, to as little as 0.05 dB or less. 
     There is shown in  FIGS. 1 and 2  an exemplary embodiment of a mechanical splice  20 , in accordance with the present invention. The mechanical splice  20  functions to connect a first optic fiber  11  to a second optic fiber  13  by providing a permanent splice with a low fiber insertion loss. The mechanical splice  20  comprises a ferrule  21  with a capillary bore  23  axially extending between a first ferrule end  25  and a second ferrule end  27 . As best seen in  FIG. 2 , the capillary bore  23  may have a non-circular cross-section in the general shape of a four-sided polygon, such as a trapezoid or square. The capillary bore  23  is configured to allow insertion of the first optic fiber  11  and the second optic fiber  13  into the ferrule  21 , as shown. 
     The specified size of the capillary bore  23  is large enough to allow the first optic fiber  11  and the second optic fiber  13  to be inserted into and guided through the opposite ferrule ends  25  and  27  without breakage or binding. The size of the capillary bore  23  is further small enough to provide for close retention of the optic fibers  11  and  13  inside the capillary bore  23  and thus provide for precise relative alignment of the respective fiber cores when an end face  15  of the first optic fiber  11  makes contact with an end face  17  of the second optic fiber  13 . In the example provided, the capillary bore  23  is shaped such that the optic fibers  11  and  13  contact the perimeter of the capillary bore  23  at up to four circumferential regions and are thus restrained from misalignment. The ferrule  21  may include lead-in funnel-like or concave conical openings  19  at the ferrule ends  25  and  27 , to provide improved fiber guidance when the optic fibers  11  and  13  are being inserted into the ferrule  21 . 
     The above configuration of the capillary bore  23  further provides micro channels  31 ,  33 ,  35 , and  37  as internal volumes for retaining an epoxy  41 . As explained in greater detail below, the micro channels  31 ,  33 ,  35 , and  37  also function as conduits to allow or enable excess epoxy  41  to flow out of the ferrule  21  as the optic fibers  11  and  13  are being inserted into the ferrule  21 . A thin layer  43  of the epoxy  41  is retained between the end face  15  of the first optic fiber  11  and the end face  17  of the second optic fiber  13  after the optic fibers  11  and  13  have been inserted into the ferrule  21 . The thin layer  43  of the epoxy  41  thus functions to mechanically secure the end face  15  of the optic fiber  11  to the end face  17  of the optic fiber  13 . The epoxy  41  remaining in the micro channels  31 ,  33 ,  35 , and  37  function to secure the outer surface of the first optic fiber  11  and the outer surface of the second optic fiber  13  to the ferrule  21 . 
     In an exemplary embodiment, the index of refraction of the epoxy  41  is substantially the same as, or closely matched to, the index of refraction of the cores of the optic fibers  11  and  13  to assure minimal insertion loss of signal at the interface between the end face  15  and the end face  17 . The insertion loss may be further minimized by maintaining a close tolerance on the size of the capillary bore  23  so as to provide precise alignment of the respective fiber optic cores. Preferably, the thermal coefficient of expansion of the epoxy  41  is closely matched to the thermal coefficients of expansion of the optic fibers  11  and  13 , and the thermal coefficient of expansion of the material used for the ferrule  21  is also closely matched to the thermal coefficient of expansion of the optic fibers  11  and  13 . This thermal coefficient matching serves to minimize thermal stresses in the mechanical splice  20  produced when the ambient temperature varies. 
     In an alternative exemplary embodiment, shown in the cross-sectional diagram of  FIG. 3 , a ferrule  51  comprises a capillary bore  53  having a non-circular cross sectional shape of a three-sided polygon, or triangle. It should be understood that the shape of the capillary bore  53  need not be an equilateral triangle, and that the vertices of the triangular capillary may be rounded, as shown, in accordance with fabrication preference. The size of the capillary bore  53  is preferably specified such that the first optic fiber  11  and the second optic fiber  13  can make contact with each other inside the ferrule  51  with precise relative alignment of the respective fiber cores, as discussed above for the ferrule  21 . That is, the optic fibers  11  and  13  contact the perimeter of the capillary bore  53  at three circumferential regions to insure the proper relative alignment. 
     The capillary bore  53  is further configured to provide micro channels  55 ,  57 , and  59  as internal volumes for retaining the epoxy  41 , where the specific sizes, shapes, and relative positions of the micro channels  55 ,  57 , and  59  depend upon the ferrule design and fabrication processes. The micro channels  55 ,  57 , and  59  similarly serve as conduits to allow or enable excess epoxy  41  to flow out of the ferrule  51  as the optic fibers  11  and  13  are being inserted into the ferrule  51 . The epoxy  41  splices the first optic fiber  11  to the second optic fiber  13  in the ferrule  51 . 
     An exemplary embodiment of a mechanical splicing apparatus  60 , or curing station, for producing the mechanical splice  20  is shown in the diagram of  FIG. 4 . The apparatus  60  comprises a first detachable clamp  61  removably mounted to a guide  39  on a base  65 , and a second detachable clamp  63  slidably mounted to a guide  49  on the base  65 . An ultraviolet light module  70  is mounted to the base  65  between the first detachable clamp  61  and the second detachable clamp  63 . An elastic component, such as a spring  69 , is connected to the ultraviolet light module  70  and to the second detachable clamp  63  as shown in the diagram. The ultraviolet light module  70  is configured to retain and irradiate a ferrule in position for insertion of the optic fibers  11  and  13 . In an exemplary embodiment, the emplaced ferrule may be the ferrule  21 , as shown, the ferrule  51  described above, or either ferrule  111  or ferrule  121  described below. 
     The first detachable clamp  61  may be used to secure and position the first optic fiber  11 , and the second detachable clamp  63  may be used to secure and position the second optic fiber  13 , as shown in the diagram. Stripping, cleaning, and cleaving processes may be performed on the optic fibers  11  and  13 , if desired, while secured in the respective clamps  61  and  63  before attachment to the base  65 . Both the first detachable clamp  61  and the second detachable clamp  63  can be moved along the base such that the first optic fiber  11  and the second optic fiber  13  can be positioned for insertion into the emplaced ferrule  21  while being held in the respective detachable clamps  61  and  63 . 
     When the first detachable clamp  61  is fixed to the guide  39  on the base  65  and the second detachable clamp  63  is allowed to slide along the guide  49 , the spring  69  functions to provide a precisely controlled, predetermined force for urging the second detachable clamp  63  toward the fixed first detachable clamp  61 , an action which causes the end  17  of the second optic fiber  13  to be controllably and precisely forced against the end  15  of the first optic fiber  11  inside the ferrule  21 . 
     The ultraviolet light module  70  comprises an ultraviolet light source, such as one or more UV lasers (not shown) or UV LEDs  71  (as shown). Some of the ultraviolet light from the UV LEDs  71  may be directly focused onto the epoxy  41  in the ferrule by passing the light through a converging cylindrical lens  73 , as shown in greater detail in the diagram of  FIG. 5 . Other ultraviolet light from the UV LEDs  71  may be scattered from a reflector  75  to additionally irradiate other areas of the epoxy  41  upon reflection. The UV LEDs  71  may be disposed proximate a UV-transparent window  77  to allow for positioning of the ferrule  21  proximate the ultraviolet light sources  71 . 
     The ultraviolet light sources in the ultraviolet light module  70  are powered by a power source, such as a rechargeable cell or battery  45  (shown in  FIG. 6 ). Control electronics  47  (shown in  FIG. 6 ) may be provided to control the exposure time and intensity of the UV LEDs  71  or UV diodes (if used). In an exemplary embodiment, a switch (not shown) is provided to allow an operator to apply a pre-set amount of power to the UV LEDs  71  or to the UV laser diodes. The operating intensity of the ultraviolet radiation may also be pre-set in the control electronics  47 . It can be appreciated that, by providing UV LEDs as a source of ultraviolet light and a battery as a source of power, the mechanical splicing apparatus  60  may be configured as a compact, portable mechanical splicing device suitable for field applications. 
       FIGS. 6 and 7  illustrate an alternate exemplary embodiment of an ultraviolet light module  80  that can be attached to the base  65  in place of the ultraviolet light module  70 . A ferrule, such as the ferrule  21 , may be secured in the ultraviolet light module  80  by mounting in a V-shaped ferrule clamp  89 . Ultraviolet light, provided by the UV LEDs  71 , may be reflected from a primary reflector, such as a cylindrical mirror  81 , on to the epoxy  41  in the ferrule  21 . The cylindrical mirror  81  may be rotatable about a pivot  85  to allow for emplacement and removal of the ferrule  21  from the ultraviolet light module  80 . Stray ultraviolet light may be reflected to the epoxy by a secondary reflector  83  disposed proximate the ferrule  21 , as best seen in the diagrammatical representation of  FIG. 7 . The ultraviolet LEDs  71  may be positioned against a UV-transparent glass plate  87  for alignment purposes. Operation of the ultraviolet LEDs  71  may be controlled and powered by the control electronics  47  and the battery  45 , as described above. 
     An alternative exemplary embodiment of a ferrule  91 , shown in  FIG. 8 , may comprise a capillary bore  93  having an oval or elliptical shape. The size of the capillary bore  93  is specified such that each of the first optic fiber  11  and the second optic fiber  13  can make contact at two circumferential regions, as shown, to provide for precise relative alignment of the respective fiber cores, as discussed above. In the configuration shown, a first micro channel  95  and a second micro channel  97  are provided for outflow of excess epoxy  41 . 
     In yet another exemplary embodiment, shown in  FIG. 9 , a ferrule  101  may comprise a capillary bore  103  having an elongated non-circular shape. The capillary bore  103  provides a single micro channel  105  for excess epoxy  41 . It should be understood that the inside configuration of the greater portion of the capillary bore  103  closely approximates the geometry of the outside surfaces of the optic fibers  11  and  13 . The gap shown between the optic fiber  11  and the capillary bore  103  has accordingly been exaggerated to more clearly illustrate this feature. 
       FIG. 10  shows a cross-sectional view of an alternative exemplary embodiment of a ferrule  111  (and a ferrule  121 ) having an offset section  113  for providing precise fiber optic alignment with capillary bores that have reduced fabrication tolerances. The offset section  113  has an offset length “L” displaced at an offset distance  119 , where the offset length L and the offset distance  119  may be determined as a function of optic fiber parameters and epoxy material properties. In an exemplary embodiment, the offset distance  119  may be in the range of 20-30 μm. 
       FIG. 11  is a cross sectional view of the offset section  113  of the ferrule  111  showing the optic fiber  13  emplaced in a triangular capillary bore  115  having relaxed fabrication tolerances. Accordingly, the optic fiber  13  is forced against a micro channel  117  by virtue of the geometry of the offset section  113 . In this configuration, the optic fiber  13  contacts an inside vertex of the triangular bore  115  at two circumferential regions, in the direction of the offset section  113 . It can be appreciated that the space between the optic fiber  13  and the inside surface of the triangular capillary bore  115  contains the epoxy  41 . Likewise,  FIG. 12  shows a cross sectional view of an offset ferrule  121  having a square capillary bore  123  with reduced fabrication tolerances. In this configuration, the optic fiber is urged in the direction of the offset to form a micro channel  125 , and contacts the inside surface of the square capillary bore  123  at two circumferential regions. It can be appreciated that the region between the optic fiber  13  and the inside surface of the square capillary bore  123 , which has been exaggerated for clarity of illustration, contains the epoxy  41 . 
       FIG. 13  shown an exemplary embodiment of a mechanical splice  140  for joining jacketed optic fiber cable, such as a first optic cable  131  and a second optic cable  141 . The mechanical splice  140  comprises a protective metal tube  150  as an environmental enclosure for the ferrule, here shown as the ferrule  21 , although it should be understood that any of the ferrule  51 , the ferrule  111 , and the ferrule  121 , or any other suitable ferrule, can be used as well. The mechanical splice  140  further functions to withstand a tensile force that may be applied to either or both the first optic cable  131  and the second optic cable  141  during laying, pulling, or other installation procedures, for example. 
     As typically configured in the present state of the art, the first optic cable  131  may comprise an optic fiber  133 , a resin buffer layer  135 , a flexible fibrous polymer  137 , such as Kevlar®, and an outer jacket layer  139 , such as a plastic. The second optic cable  141  may similarly comprise an optic fiber  143 , a resin buffer layer  145 , a flexible fibrous polymer  147 , and an outer jacket layer  149 . The resin buffer layer  135  and the resin buffer layer  145  are removed from the portions of the optic fiber  133  and the optic fiber  143 , respectively, to allow for insertion into the ferrule  21 , or another ferrule that may be used. The epoxy  41  secures the outer surface of the optic fiber  133  and the outer surface of the optic fiber  143  to the ferrule  21 , and the thin layer  43  of the epoxy  41  is retained between the optic fiber  133  and the optic fiber  143 , as described above for the mechanical splice  20 . 
     An internal sleeve  151  is inserted between the resin buffer layer  135  and the fibrous polymer  137 , and another internal sleeve  151  is inserted between the resin buffer layer  145  and the flexible fibrous polymer  147 . An outer sleeve  153  is positioned over the fibrous polymer  137  the first optic cable  131  such that a conical opening  157  in the outer sleeve  153  encloses a flared end  155  of the internal sleeve  151 . A portion of the fibrous polymer  137  is thus retained between the flared end of the internal sleeve  151  and the conical opening of the outer sleeve  153 . Similarly, another outer sleeve  153  is positioned over the fibrous polymer  147  in the second optic cable  141  such that the conical opening  157  in the other outer sleeve  153  encloses the flared end  155  of the other internal sleeve  151  to retain a portion of the fibrous polymer  147 . 
     A crimp  159  is formed in one end of the metal tube  150  at the outer sleeve  153 , and another crimp  159  is formed in another end of the metal tube  150  at the other outer sleeve  153 , to secure the metal tube  150  to the first optic cable  131  and to the second optic cable  141 . It can be appreciated by one skilled in the relevant art that a tensile force applied to the first optic cable  131  is thus conveyed through the fibrous polymer  137  and through the metal tube  150  to the fibrous polymer  147 , and thus transferred to the second optic cable  141  without stressing either the first optic fiber  133  or the second optic fiber  143 . This configuration ensures that the first optic fiber  133  remains spliced to the second optic fiber  143  after laying, pulling, or other installation procedures have been performed on the first optic cable  131  and the second optic cable  141 . 
     The disclosed method of mechanical optic fiber splicing, using the mechanical splices  20  and  140  as examples, can be explained with additional reference to a flow diagram  160  in  FIG. 14 . A ferrule (i.e., the ferrule  21 , the ferrule  51 , the ferrule  111 , the ferrule  121 , or another suitably-configured ferrule) is obtained and the optic fibers are prepared by trimming and stripping as required, at step  161 . If the splice to be made is an optic fiber cable mechanical splice, or is a fiber splice that may be subjected to harsh environments, at decision box  163 , internal sleeves  151  and outer sleeves  153  are emplaced as described above to retain the fibrous polymer material, and the metal tube  150  may be placed over one of the optic fibers, in step  165 . If, at decision box  163 , the splice to be made is for loose-tube construction optic fibers, the metal tube may not be required and operation proceeds directly to decision box  167 . 
     If the ferrule has been preloaded with epoxy, at decision box  167 , the optic fibers are inserted into the ferrule, at step  171 . Preferably, the preloaded ferrule has been stored by sealing in a light blocking and moisture blocking packaging to prevent premature curing of the epoxy. If the ferrule has not been preloaded with epoxy, at decision box  167 , a predetermined quantity of epoxy may be injected into the ferrule, at step  169 , and then the optic fibers may be inserted at opposite ends of the ferrule, as in step  171 . 
     A predetermined compressive axial force is applied to the optic fibers after insertion to minimize the thickness of the layer of epoxy in the region between the fiber ends, at step  173 . Preferably, the magnitude of the force is restrained to prevent possible damage to the optic fibers. This compressive force may be applied and maintained by the spring  69 , shown in  FIG. 4 . The epoxy  41  in the ferrule is cured, at step  175 , by irradiation with a predetermined intensity of ultraviolet light for a predetermined time. 
     If the mechanical splice is to be used in loose-tube construction, rather than in a jacketed fiber cable application, at decision block  177 , the mechanical splice is complete, at step  179 . If, on the other hand, the mechanical splice is to used with jacketed optic fiber cable, the metal tube  150  is positioned to enclose the ferrule and the ends of the metal tube  150  are crimped onto the outer sleeves  153 , in step  181 , each internal sleeve  151  and outer sleeve  153  retaining therebetween a flexible fibrous polymer portion of the corresponding optic fiber cable. 
     It is to be understood that the description herein is exemplary of the invention only and is intended to provide an overview for the understanding of the nature and character of the invention as it is defined by the claims. The accompanying drawings are included to provide a further understanding of various features and embodiments of the method and apparatus of the invention which, together with their description serve to explain the principles and operation of the invention. Thus, while the invention has been described with reference to particular embodiments, it will be understood that the present invention is by no means limited to the particular constructions and methods herein disclosed and/or shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.