Abstract:
A strain relief connector for a fiber optic cable has an optical fiber enclosed within a cover having an outer diameter. A relatively long sleeve surrounds the cover and has an inner surface at an inner diameter, the inner diameter being substantially larger than the outer diameter of the cover. Portions of the sleeve and the fiber optic cable are compressed by a die, forming compressed portions having widths substantially larger than their heights and causing the inner surface of the sleeve to frictionally engage the outer surface of the cover layer and the inner surface of the cover to fictionally engage the outer surface of the optical fiber enclosed therein. The length of the sleeve and the configuration of the compressed portion allow a relatively high area of frictional resistance between the buffer layer and the sleeve.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a non-adhesive strain relief connector for a fiber optic cable. More particularly, the present invention relates a fiber optic cable that is disposed with in a metal sleeve, with the cable and sleeve being simultaneously compressed forming a long flat crimp connector having a width that is substantially greater than its height. The combination of the length and the width results in a large frictional surface between the sleeve and the fiber optic cable providing a strong, reliable connection. 
     BACKGROUND OF THE INVENTION 
     Strain relief connectors for fiber optic cables are common in the connector industry. Conventional strain relief connectors have a sleeve surrounding a light transmitting optical fiber or a plurality of light transmitting optical fibers. The optical fibers are generally surrounded or covered and protected by a jacket or buffer material formed from a plastic. The sleeve and the fiber optic cable are then crimped using a crimping tool into a hexagonal or round shape. 
     Conventional crimping methods do not allow adequate lateral flow of the jacket material, in other words, the jacket material does not substantially flow in a direction perpendicular to the longitudinal axis of the crimp sleeve. A lack of lateral flow forces the buffer material to flow along the longitudinal axis of the crimp sleeve, producing longitudinal flow. Longitudinal flow places tension on the optical fiber, possibly causing damage to or failure of the optical fiber, or changing its optical characteristics. 
     In addition, conventional crimping methods have a crimp length that is short relative to the diameter of the jacket material. Generally, the length of the crimp is less than four times the buffer material diameter. This short length results in a small area of frictional contact between the inner surface of the crimp sleeve and the outer surface of the buffer material and may make failure of the connector more likely under tensile or thermal stress. 
     Examples of prior art fiber optic cable crimp connectors are disclosed in the following U.S. Pat. No.: 3,655,275 to Seagraves; U.S. Pat. No. 4,738,504 to Jones; U.S. Pat. No. 5,140,662 to Kumar; U.S. Pat. No. 5,317,664 to Grabiec et al.; U.S. Pat. No. 5,418,874 to Carlisle et al.; U.S. Pat. No. 5,455,880 to Reid et al. 
     Thus, a continuing need exists for strain relief fiber optic connectors. 
     SUMMARY 
     Accordingly an object of the present invention is to provide a strain relief connector for a fiber optic cable that has a relatively large frictional area between the inner surface of the crimp sleeve and the cover layer of the fiber optic cable for a strong reliable crimp connector. 
     Another object of the present invention is to provide a strain relief connector for a fiber optic cable that has a crimped configuration that allows for substantial lateral flow of the cover layer, putting substantially no longitudinal pressure or strain on the optical fiber. 
     Still another object of the present invention is to provide a strain relief connector for a fiber optic cable that has a crimp sleeve with a length that is long relative to the diameter of the cover layer, providing a large area of frictional engagement between the cover layer and crimp sleeve and the cover layer and optical fiber. 
     The foregoing objects are basically attained by providing-a strain relief connector, comprising a securing member, a fiber optic cable having an optical fiber with an outer surface enclosed within a cover having an inner surface and a first outer diameter, and a sleeve surrounding the fiber optic cable and coupled to the securing member. The sleeve has a first inner diameter. The first inner diameter is substantially larger than the first outer diameter. A die compressed crimp portion of the sleeve and a compressed portion of the fiber optic cable, have widths substantially larger than heights thereof. The inner surface of the cover frictionally engages the outer surface of the optical fiber disposed therein. 
     Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings which form a part of this disclosure: 
     FIG. 1 is a side elevational view in section of a strain relief connector according to a first embodiment of the present invention. 
     FIG. 2 is an enlarged side elevational view of the fiber optic cable extending through the crimp sleeve illustrated in FIG. 1, a portion of the fiber optic cable and the crimp sleeve being compressed. 
     FIG. 3 is an end elevational view in section of the cable and sleeve taken along line  3 — 3  of FIG.  2 . 
     FIG. 4 is a side elevational view of a die and the fiber. optic cable extending through the crimp sleeve, illustrated in FIG. 2, prior to compression by the die. 
     FIG. 5 is an end elevational view in section of the cable, sleeve and die taken along line  5 — 5  of FIG.  4 . 
     FIG. 6 is an enlarged end elevational view in section of the fiber optic cable disposed within the crimp sleeve of FIG.  5 . 
     FIGS. 7 a-d  are side elevational views in section of a strain relief connector according to a second embodiment of the present invention having a fiber feed bushing inserted into the crimp sleeve. 
     FIG. 8 is a side elevational view in section of a strain relief connector according to a third embodiment of the present invention, having an alignment ferrule inserted into the connector body. 
     FIG. 9 is a side elevational view in section of a strain relief connector according to a fourth embodiment of the present invention having an alignment ferrule inside a crimp sleeve to align separate fiber optic cables. 
     FIG. 10 is an end elevational view in section of a strain relief connector according to a fifth embodiment of the present invention having a V-groove element to align separate fiber optic cables. 
     FIG. 11 is an end elevational view in section of a strain relief connector according to a sixth embodiment of the present invention having a plurality of fiber optic cables extending through a crimp sleeve prior to compression. 
     FIG. 12 is an end elevational view in section of the strain relief connector of FIG. 11 after being compressed by a die. 
     FIG. 13 is an end elevational view in section of a strain relief connector according to a seventh embodiment of the present invention having a plurality of fiber optic cables extending in separate or connected crimp sleeves. 
     FIG. 14 is an end elevational view in section of a strain relief connector according to an eighth embodiment of the present invention having a fiber optic cable with a coating material and a buffer layer extending through a crimp sleeve, before being compressed. 
     FIG. 15 is an end elevational view in section of the strain relief connector of FIG. 14 after being compressed by a die. 
     FIG. 16 is an end elevational view in section of the strain relief connector of FIG. 14, wherein less force was used to compress the crimp sleeve then used in the connector of FIG.  15 . 
     FIG. 17 is an end elevational view in section of the strain relief connector of FIG. 14, but with plurality of fiber optic cables extending through a crimp sleeve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIGS. 1-3, a strain relief connector  10  according to a first embodiment of the present invention has a securing member or mechanism  12  surrounding a deformable connector body  14 . Spring  16  is inserted between the securing member  12  and the connector body  14 . The connector body  14  surrounds a portion of an alignment ferrule  18  and is coupled to a crimp ring  20 . A deformable crimp tube or sleeve  22  is disposed within the connector body and the deformable crimp tube  22  is coupled to a fiber optic cable  24  having a cover  26  surrounding an optical fiber  28 . 
     The securing member  12  is preferably a tubular or round metal threaded or bayonet type nut known in the pertinent art, such as an FC or ST type connector or any other suitable connector. The securing member does not necessarily have to be tubular, round, or metal and may be any type of securing device that can be connected to the deformable connector body  14  receiving deformable crimp tube  22 . 
     Preferably, the securing member  12  has cylindrical inner and outer surfaces  30  and  32 , respectively, the inner surface  30  defining a through passageway  34 . Additionally, adjacent the inner surface  30  the securing member has a cylindrical shoulder or stop  36  defining a hole  38 . Cylindrical shoulder  36  extends around the entire circumference of inner surface  30  and defines a reduced diameter for a portion of through passageway  34 . 
     Deformable connector body  14  is preferably a metal tubular body having first and second ends  40  and  42 , respectively. As seen in FIG. 1, adjacent first open end  40  is cylindrical outer surface  44 . Outer surface  44  extends substantially the length of connector body  14 . Extending substantially perpendicular to and away from surface  44  is cylindrical removable washer or stop  46 . Stop  46  extends substantially around the circumference of outer surface  44  and fits into groove  47 . Outer surface  44  terminates at outwardly extending, rearwardly axial facing surface  48  of extension  50 . Extension  50  terminates at second open end  42 , forming an enlarged radial portion of connector body  14 . 
     Cylindrical inner surface  52  of connector body  14  defines through passageway  54  and is adjacent frustoconical surface  56 . Frustoconical surface  56  tapers toward cylindrical surface  58 , which is adjacent forwardly facing axial surface  60 . Surfaces  56 ,  58  and  60  form a cylindrical shoulder or stop  62 , which forms a reduced radius for a portion of through passageway  54 . Adjacent surface  60  is cylindrical surface  64  that has substantially the same diameter as inner surface  52  and terminates at second end  42 . 
     Spring  16  is preferably a helical plastic or metal spring having first and second ends  13  and  15 , respectively. Spring  16  is not necessarily helical and may be any suitable shape or material that would be capable of biasing either the body  14  or the securing member  12 , relative to the other. 
     As shown in FIG. 1, alignment ferrule  18  is preferably a ceramic cylindrical tube having outer surface  66  and through passageway  68 . Alignment ferrule  18  does not necessarily have to be ceramic and may be any suitable material and shape that would allow it to be coupled to the connector body  14  or the securing member  12 . Preferably, ferrule  18  has a first open end  70  and a second open end  72 . Inner frustoconical surface  74  extends from first end  70 , tapering inward toward the center of ferrule  18 . Cylindrical surface  76  is adjacent surface  74  and extends to second end  72 . 
     Crimp ring  20  is a preferably a metal cylindrical tube having through passageway  78  and first and second ends  80  and  82 , respectively. However, ring  20  does not necessarily have to be metal and may be any suitable material and shape that would allow it to be coupled to the connector body  14 . Cylindrical outer surface  84  extends from first open end  80  to one end of outwardly extending, rearwardly axially facing surface  85  and cylindrical surface  86  extends from the other end of surface  85  to second open end  82 . Cylindrical inner surface  88  extends from first end  80  to frustoconical surface  90 , which extends radially outwardly from surface  88  to cylindrical surface  92 , surface  92  terminating at second end  82 . Ring  20  facilitates coupling the connector body  14  to the sleeve  22 . 
     As seen in FIGS. 4-6, crimp sleeve  22  is preferably a relatively long deformable metal sleeve. The length of sleeve  22  is preferably at least five times the diameter of fiber optic cable  24  extending therethrough and is more preferably seven times the diameter of the cable  24 . Crimp sleeve  22  has cylindrical inner and outer surfaces  94  and  96 , respectively and initial inner and outer diameters,  98  and  100 , respectively. The outer surface  96  is preferably a smooth substantially uniform surface extending from first open end  102  to second open end  104 . Inner surface  94  may be either smooth or roughened to increase the coefficient of static friction thereon. As seen in FIGS. 1 and 2, a fiber optic cable  24  extends through the sleeve  22 . 
     As seen in FIG. 6, the fiber optic cable preferably includes of a glass optical fiber  28  having a 125 micron (0.125 mm) outer diameter  106  surrounded by cover  26 . However, the optical fiber may be any suitable diameter and any suitable material for propagating light, such as plastic or the like. The cover  26  is preferably a polymer tube formed from a thermoplastic elastomer material, such as HYTREL 6356. HYTREL forms a family of copolyester elastomers. Typical reactants from which the elastomers are derived are terephthalic acid, polytetramethylene glycol, and 1,4-butanediol. This type of elastomer is highly resilient with a good resistance to flex fatigue at low and high temperatures, and is resistant to oils and chemicals. However, the cover may be any suitable material that may be compressed while simultaneously protecting the optical fiber it surrounds. The cover  26  has a 900 micron initial outer diameter  108 , which is substantially smaller than the inner diameter  98  of sleeve  22 . Cover  26  surrounds optical fiber  28  and initial inner diameter  110  of cover  26  is substantially larger than the outer diameter of the optical fiber  28 . 
     As seen in FIGS. 2 and 3, sleeve  22  and cable  24  are compressed along a portion thereof. The deformed width of the crimp sleeve is substantially greater than the original un-crimped outside diameter. The deformed height of the crimp sleeve is substantially less than the original un-crimped outside diameter. As seen specifically in FIG. 3, the internal portion of the present invention produces substantial vertical compression of cover  26  of optical fiber cable  24 , the cover substantially filling the entire inner volume of the compressed crimp portion of sleeve. This vertical compression produces unique cross sectional geometries of the crimp sleeve  22  and cover  26 , each having a width in the horizontal plane substantially greater than the height in the vertical plane. 
     Additionally, the volume of the deformed portion of the cover  26  is actually reduced from its original volume due to compression. The long length of the deformed portion of sleeve  22  is such that it constrains the flow of cover material in the axial direction due to friction with the internal surface of the crimp sleeve. Substantially all of the cover extends in a direction substantially perpendicular to the axial direction or a longitudinal axis of the optical fiber and the length of the sleeve, limiting tensile stress in the optical fiber in a longitudinal direction. This constraint of axial flow, in addition to the reduction in cover volume, produces increased local compression of cover material surrounding the glass fiber, as seen in FIG.  3 . The lateral flow of cover  26  also limits the effect of axial cover elongation from inducing excessive tensile stress into the optical fiber  28  in the longitudinal direction. The combination of reduced volume and constrained flow of cover  26  results in an increase in the local density of the cover  26 . The increase in local density results in an increase in the local elastic modulus of the material in contact with the optical fiber  28 , which contributes to an increase in pressure applied to the surface of the optical fiber. This increase in applied pressure, over a relatively long length of area on the optical fiber, increases the friction force required to move the optical fiber in the axial direction relative to the deformed crimp sleeve. The increased friction force and subsequent resistance to axial movement of the optical fiber contributes to improved performance in tensile cable retention. 
     Additionally, the crimp may form a laterally central-portion (not shown) extending upwardly and downwardly from of sleeve  22  and cover  26  and, aligned vertically with the optical fiber, which are not compressed to the same extent as the remaining portions thereof. These central portions help maintain the centrality of the optical fiber  28  within the crimp sleeve  22  during the crimping process, and provide a slightly thicker region of cover  26  along both sides of the optical fiber in the vertical plane. These thicker, localized cover regions prevent the inner surface  96  of crimp sleeve  22  from contacting the glass fiber. This configuration adds an element of safety to the crimp technique described herein. It should be noted that any contact of metal to the optical fiber is undesirable, and could lead to fracture failure of the optical fiber. 
     To crimp sleeve  22  to cable  24 , cable  24  is extended or inserted through sleeve  22 . As seen in FIG. 4, sleeve  22  and cable  24  are then inserted into a long flat crimp die  114  having upper and lower jaws  116  and  118 , respectively. As seen in FIG. 5, jaws  116  and  118  have a width that is substantially greater than the height thereof, permitting uninhibited lateral flow of sleeve  22  and cover  26 . By applying the proper amount of pressure or designing the die  114  to be fully closed at the proper crimp height, the configuration of the die compressed crimp portion of the sleeve and the compressed portion of the fiber optic cable shown in FIG. 3 may be obtained. 
     Assembly 
     A portion of cover  26  is stripped away from the fiber optic cable  24 , leaving an exposed portion  29  of optical fiber  28 , as seen in FIGS. 2 and 4. As described above, cable  24  is inserted into sleeve  22  and crimped. Sleeve  22  and cable  24  are then inserted into connector body  14 , as seen in FIG.  1 . Securing member  12 , connector body  14 , and spring  16  are a preassembled conventional item that is known to one skilled in the art. Optical fiber  28  enters ferrule  18  and extending therethrough and sleeve  22  abuts stop  62 . The exposed portion  29  of optical fiber  28  extends outward from alignment ferrule  18  after crimping to allow for cleaving and polishing flush to the end face. First end  40  of connector body  14  is then inserted into second open end  82  of ring  20  and coupled thereto by a conventional hex type crimp applied to surface  86 . The hex crimp also coupling connector body  14  to sleeve  22 , and further protecting sleeve  22  and fiber optic cable  24 . However, it is possible to leave out one or a plurality of the above mentioned parts. For example, it is possible to couple the securing member  12  directly to the sleeve  22  using crimping or any other suitable methods, to connect the ferrule  18  directly to the sleeve  22  and/or to leave out the ring  20 . In addition, it is possible to insert the fiber optic cable  26  directly into the connector body  14  and to crimp the connector body, as described below. 
     Embodiment of FIGS. 7 a-d    
     As seen in FIGS. 7 a-d , metal sleeve  122  is substantially similar to sleeve  22 , however, sleeve  122  may have a fiber feed bushing  120  and elastomer tube or cover  121  inserted therein. Sleeve  122  also has cylindrical extensions  126  and  128  extending substantially perpendicular and outwardly from surface  130 . Extensions  126  and  128  facilitate insertion and reception into connector body  14 . In addition, sleeve  122  has a surface  132  defining a large through passageway  134 . Surface  132  extends to frustoconical surface  136 , which tapers inwardly and is adjacent cylindrical surface  138 , which defines a small through passageway  139 . 
     The bushing  120  has cylindrical inner and outer surfaces  154  and  156 , respectively, inner surface  154  defining a through passageway  139 . Outer surface  156  begins at first open end  160  extends to frustoconical surface  158 , which terminates at second open end  162 . Inner surface  154  extends from first end  160  to frustoconical surface  164 , which is adjacent conical surface  166  defining through passageway  168 . 
     The elastomer tube  121  is similar to cover  26  and surrounds a portion of an optical fiber or glass fiber  140 , and has an inner and outer surface  146  and  148 , inner surface  146  defining a through passageway  150 . However, the cover  121  is a separate protective section and the fiber optic cable  142  has another cover or buffer portion  144  protecting the majority of the un-crimped or exposed portion of cable  142 , a portion of which is stripped away allowing the optical fiber  140  to extend through passageway  150 . 
     The elastomer tube  121  and feed bushing  120  are secured within the crimp tube by adhesive, interference fit, or staking or slight deformation of the crimp tube to permit a suitable interference fit. The buffer portion  144  of the optical fiber cable  142  is received within the through passage way  139  of the feed bushing  120 , frustoconical surface  158  abutting frustoconical surface  136  of sleeve  122  when inserted therein. The exposed optical fiber  140  is received within the through passageway  168  of feed bushing  120  and throughout elastomer tube  121 . Through passageway  168  of the feed bushing  120  is preferably larger than the optical fiber and slightly less than the internal diameter of elastomer tube  121 . The optical fiber also extends outward from elastomer tube  121 , to be received by the alignment ferrule of a typical connector or splice, similar to FIG.  1 . Preferably, the long flat crimp is applied, as described above, over the crimp tube portion only through which elastomer tube  121  is received. However, the feed bushing  120  disposed within the crimp sleeve  122  may also be crimped. 
     Embodiment of FIG. 8 
     As seen in FIG. 8, metal connector body  214  has a plastic or metal alignment ferrule  218 , inserted therein, as described above. Ferrule  218  is substantially similar to ferrule  18  and the description of ferrule  18  is applicable to ferrule  218 . In the present embodiment, body  214  has an inner cylindrical surface  224  adjacent first open end  226  defining a through passageway  228  therethrough. Surface  224  is adjacent axially facing outwardly extending surface  230  that extends to cylindrical surface  232 , which terminates at second open end  234 . Surface  232  defining a through passageway  236  that is larger in diameter than through passageway  228 . 
     Ferrule  218  may be inserted though second end  234  and one end of ferrule  218  abutting surface  230 . In this configuration, the crimp, using a long flat crimp die similar to die  114  shown in FIGS. 4 and 5, is performed directly onto the connector body  214 . Disposed within the connector body prior to crimping may be an fiber optic cable  238  either with the buffered layer or optical fiber surrounded by a thermoplastic elastomer tube  240 , as described above. The elastomer tube  240  configuration may have a fiber feed bushing as described above, to aid the insertion of optical fiber  242  into the elastomer tube  240 . 
     Embodiment of FIG. 9 and 10 
     As seen in FIG. 9, the crimp method described above may be used to splice two axially aligned separate fiber optic cables together. A metal crimp sleeve  322  has inner and outer surfaces  324  and  326 , surface  324  defining a uniform through passageway  328 . A metal or plastic fiber alignment ferrule  330 , similar to the alignment ferrules described above, however, having a inner frustocontical surfaces  332  and  334  on each open end  336  and  338 , respectively, is positioned substantially equidistant from first and second ends  337  and  339  of sleeve  322 , as shown in FIG.  9 . Frustoconical surfaces  332  and  334  facilitate entering of optical fibers or exposed optical fibers  340  and  342  into each respective end of ferrule  318 . Optical fibers  340  and  342  extend from respective fiber optic cables in a manner described above. The two optical fibers join together in physical contact or abut one another within the alignment ferrule at a point  343 . The alignment ferrule may have optical refractive index matching gel to enhance optical transmission therethrough. 
     Disposed within each end of the deformable crimp tube  322  are thermoplastic elastomer tubes  344  and  346 . The elastomer tubes are substantially similar to the elastomer tubes described above, and surround exposed optical fibers  340  and  342 , onto which the long flat crimp is applied, in a similar manner as described above. The covers  352  and  354  of the fiber cables are not necessarily crimped in this embodiment. To aid the insertion of the fibers  340  and  342  through the elastomer tubes  344  and  346 , fiber feed bushings  348  and  350  may be used by securing into the ends of the deformable crimp tube  322 , as described above. Fiber feed bushings  348  and  350  are substantially similar to the feed bushings described above. 
     It is also possible to center the two optical fibers along a vertical axis, using a V-groove  353  in a non-deformable cylindrical member  356 , as shown in FIG.  10 . Cylinder member  356  is disposed within sleeve  322  similarly to ferrule  330 , shown in FIG.  9  and functions in a substantially similar manner as ferrule  330 , optic fibers contacting one another along a length of groove  353 . Only one optical fiber  362  is shown, as it is understood that member  356  may splice two or more fiber optic cables together as described above. Preferably, cylindrical member  356  is formed from glass, although it can also be plastic or metal, and has an outer diameter  358  that is substantially smaller then the inner diameter  360  of the elastomer tube  354 . Applied in the vertical plane, the flat crimp dies deform the crimp tube, thereby compressing the elastomer  354  over the adjoined optical fibers, forcing them into the V-groove  352 . This force on the fibers in the groove produces a frictional force that resists axial movement or slippage of the fibers apart from each other. It is understood that the deformable crimp tube, elastomer, and V-groove element may be of circular or noncircular shape, or any shape permitting the use of a long flat crimp. The two exposed glass fibers join together in physical contact within the V-groove, where refractive index matching gel may be applied to enhance optical transmission therethrough. 
     Embodiment of FIGS. 11-13 
     As seen in FIG. 11, sleeve  422 , is initially oval in shape, in all other aspects, material and length, of sleeve  422  is substantially similar to sleeve  22 . Extending through sleeve  422  are fiber optic cables  424  and  426 , Cables  424  and  426  are substantially similar to cable  24 , described above. It is understood that this configuration may apply to one, two, or more optical fibers disposed within either a single round or oval, or multiple round  423  and  425 , as shown in FIG. 13, or oval tubes, either adjacent to one another or with spacing between. 
     FIG. 12 shows the crimped condition of the duplex fiber configuration, shown in FIG.  11 . The internal diameter of the elastomer tube collapses in a manner to surround the optical fiber. The pressure of the elastomer surrounding the optical fiber is such that the retention strength of the fiber within the crimp will exceed prior art strain relief connectors. The crimping and assembly methods are substantially similar to those described above. 
     Embodiment of FIG. 14-17 
     Crimp sleeve  522  is substantially similar to sleeve  22  described above. However, as shown in FIG. 14, the fiber optic cable  524  has an optical fiber  526  of a 125 micron (0.125 mm) diameter  528 . Surrounding the optical fiber is preferably an acrylate polymer coating  530  that has of a 250 micron (0.250 mm) outside diameter  532 . However, the coating may be any suitable polymer. Surrounding the polymer coating  530  is a buffer material or layer  534  of a 900 micron (900 mm) outer diameter  536 . Preferably the buffer layer is polyvinyl chloride (PVC), but may be any other suitable material. Similar the cover  26  above, outer diameter  536  of buffer layer  534  is substantially smaller than inner diameter  538  of sleeve  522 . 
     The crimping method is substantially similar to the above described crimping method and results in the deformed width substantially greater than the deformed height. As seen in FIG. 15, the internal portion of the present embodiment produces substantial vertical compression of the buffer layer and coating of the optical fiber cable. This vertical compression imparted by the flat crimp die profile produces unique cross sectional geometries of the crimp sleeve  522 , buffer layer  534 , and coating material  530 . The unique pattern of coating material displacement is such that the coating material flows in a divergent pattern relative to the glass optical fiber, the coating material substantially filling the entire inner volume of the compressed crimp portion of sleeve. The divergent pattern of the coating material  530  is such that two circular-segmented lobes  540  and  542  of bilateral symmetry are formed adjacent to the optical fiber in the horizontal plane, as seen in FIG.  15 . The formation of the divergent, circular-segmented lobes  540  and  542  of coating material  530  permits the compressed buffer layer  534  to contact the optical fiber  526  along two separated arcute areas on opposite sides of the glass fiber. This change in material contact can only be accomplished by the flat crimp technique. The amount of divergence of the coating material in the horizontal direction is dependent on the rigidity of the buffer layer. Buffer materials of relatively high rigidity produce less horizontal divergence of the coating material. 
     According to calculations, the volume within the internal deformed portion of the buffer layer and coating material is actually reduced. For example, the percent reduction in aggregate volume of the buffer layer and coating material can be as much as 8%. The long length (as defined herein) of the deformed portion of this preferred embodiment is such that it constrains the flow of buffer material in the axial direction due to friction against the internal surface of the crimp sleeve. A drilled finish on the internal diameter of the undeformed crimp sleeve enhances this friction effect. This constraint of axial flow, in addition to the aggregate reduction in buffer layer and coating material volumes, produces increased local compression of buffer layer and coating material surrounding the glass fiber in FIG.  15 . Similar to the cover  26 , described above, the combination of reduced volume and constrained flow of buffer layer and coating material results in an increase in the local density of the aggregate buffer layer and coating material and an increased friction force. The increased friction force and subsequent resistance to axial movement of the optical fiber contributes to improved performance in tensile cable retention tests. 
     Additionally similar to that described above, a portion of the internal radius of the crimp sleeve and a portion of the buffer layer in the crimped portion may remain slightly undeformed. These portions of the internal radius and buffer layer helps maintain the centrality of the optical fiber and prevent the deformed metal crimp sleeve internal surface from contacting the glass fiber. 
     FIG. 16 illustrates a further embodiment of fiber optic cable  624  and a sleeve  622 . The cable  624  has an optical fiber  626  surrounded by a coating material  630 , which is surrounded by a buffer layer  628  after crimping. In this embodiment, the deformed height is somewhat greater than as shown in FIG. 15, the displacement of the coating material  630  is less severe, due to the height of the crimp die, the amount of pressure exerted or the strength of the buffer layer. This deformation results in the coating material remaining in contact around the entire diameter of the glass optical fiber. The sleeve  622  and the methods of assembly and crimping are substantially similar to those above. 
     As seen in FIG. 17, a plurality fiber optic cables  724  and  726  extend through sleeve  722 . The buffer layers  728  and  729  of each fiber optic cable  732  and  734  flows in a manner which completely fills the oval shaped internal area of the crimp sleeve after crimping. The coating material  730  and  731  of each optical fiber  736  and  738  may deform into a pattern similar to that shown in FIG. 16, or in FIG. 15 The materials and method of crimping are similar to those described above. 
     While specific embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.