Patent Publication Number: US-6909828-B2

Title: Fiberoptic furcation device with crimp

Description:
RELATED APPLICATION 
   The present application is a continuation application of application Ser. No. 10/613,757, filed Jul. 2, 2003, the disclosure of which is incorporated by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to devices and methods for breaking out, or furcating, optical fibers from within a fiberoptic cable into a larger cable, such as a protective upjacket. 
   BACKGROUND OF THE INVENTION 
   Fiberoptic cables often contain one or more individual optical fibers within a jacket. It is desirable to remove the jacket to expose the individual optical fibers, such as for connectorization in order to connect each fiber to telecommunications equipment. Breaking out or furcating of bare optical fibers from within one fiberoptic cable into a larger cable, the upjacket, is known. Typically, the bare optical fibers are inserted into the upjacket before connectorization to provide protection of the optical fiber, including during connectorization. Typically, the upjacket includes an aramid yarn strength member, or other strength member to transfer any loads to the optical connector terminated onto the upjacket, or to the jacket of the fiberoptic cable containing the optical fibers, instead of to the optical fiber. 
   There is a need for improved devices and methods for breaking out or furcating optical fibers. 
   SUMMARY OF THE INVENTION 
   A cable furcation device and method are provided for upjacketing of optical fibers extending from a fiberoptic cable. The cable furcation device includes a housing for receiving the fiberoptic cable on one end. An opposite end receives each upjacket. A crimp is provided for crimping the strength members of the upjackets to the furcation housing. Preferably, the housing includes a projecting tube for receiving inside the tube each individual optical fiber, and a protective buffer tubing of the upjacket. The projecting tube also receives the outer tube of the upjacket. 
   A cable furcation device comprises a body having a front end and an opposite rear end, the body defining a longitudinal axis therebetween. The front end includes a first tube having a first outer diameter, and a first inner diameter. The front end includes a crimp surface having a second outer diameter larger than the first outer diameter, with the crimp surface located between the first tube and the rear end. The rear end has a third outer diameter larger than the second outer diameter and an inner bore has first and second inner bore portions with first and second bore diameters respectively, with the second inner bore diameter being smaller than the first inner bore diameter, the second inner bore portion located between the first bore portion and the front end. The inner bore extends from the rear end and terminates at an end wall. The body defines a first passage from the first tube to the inner bore. The first inner diameter of the first tube and the first and second inner bore diameters are sized for receiving an optical fiber. The first inner bore diameter is further sized for receiving a jacket of a cable surrounding the optical fiber. The crimp surface is sized for receiving a crimp ring to crimp a strength member of an upjacket. The first outer diameter of the first tube is sized to be received inside a tubular member of the upjacket. The first inner diameter of the first tube and the first and second inner bore diameters are sized for receiving an inner tubular member of the upjacket around optical fiber. 
   Preferably, the cable furcation device includes a second tube, having the same first outer and inner diameters as the first tube, with the first and second tubes extending parallel to one another. 
   A cable breakout assembly is provided comprising a cable furcation device which joins a cable to an upjacket. A strength member is crimped to the device. The device is joined to the cable and the upjacket through a heat shrunk tubing. 
   A method of breaking out optical fibers comprising the steps of: positioning a furcation device over the optical fibers extending from within a jacket of a cable; positioning each optical fiber in a protective inner tube of an individual upjacket; passing the protective inner tube of each of the upjackets into an interior of the furcation device; inserting an end of an outer protective tube of each of the upjackets over a tube of the furcation device; crimping a strength member of each of the upjackets to the furcation device; inserting an end of the jacket of the cable into the furcation device; and heat shrinking a tubing around the furcation device, an exposed portion of the jacket of the cable adjacent to the furcation device, and an exposed portion of the upjacket adjacent to the furcation device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a cable furcation device in accordance with one embodiment of the present invention; 
       FIG. 2  is a further perspective view of the cable furcation device of  FIG. 1 ; 
       FIG. 3  is a first side view of the cable furcation device of  FIG. 1 ; 
       FIG. 4  is a further side view of the cable furcation device of  FIG. 1 ; 
       FIG. 5  is a cross-sectional side view of the cable furcation device taken along lines  5 — 5  of  FIG. 4 ; 
       FIG. 6  is an end view of the cable furcation device of  FIG. 1 ; 
       FIG. 7  is a cross-sectional side view of the cable furcation device as in  FIG. 5 , and showing a cable including two optical fibers, and two upjackets connected to the device, wherein portions of the cable, the upjackets and a heat shrunk tube are shown schematically or have been removed for clarity; 
       FIG. 8  shows the cable furcation device of  FIG. 1  during an initial stage of assembly for the cable break out, showing the upjackets connected to the device, prior to crimping of the strength members; 
       FIG. 9  shows a further step in the assembly, showing crimping of the strength members; 
       FIG. 10  shows a further step in the assembly, showing the strength members crimped to the device; 
       FIG. 11  shows a further step in the assembly, showing the cable prior to insertion of the jacket into the device; 
       FIG. 12  shows a further step in the assembly, showing the jacket of the cable inserted into the device; 
       FIG. 13  shows a further step in the assembly, showing the heat shrinkable tube positioned over the device and the exposed ends of the cable and the upjackets; 
       FIG. 14  shows a further step in the assembly, showing the heat shrunk tube over the cable furcation device and the cable and the upjackets; 
       FIG. 15  shows a prior art break out during assembly including two upjackets positioned relative to two optical fibers of a cable; 
       FIG. 16  shows the assembly of  FIG. 15  with a protective metallic sleeve over the ends of the cable and the upjackets, and showing the strength member exposed prior to the heat shrinkable tube being placed over the protective metal tube and the ends of the cable and upjackets, and the strength member. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIGS. 1-7 , a cable furcation device or connector  10  is provided for breaking out or furcating individual optical fibers  12 ,  14  from a first cable  16 . Cable  16  may also be known as a drop cable. Cable  16  may include an outer jacket  18 , and an innerjacket  20 . A strength member, such as a wire (not shown) may also be provided with cable  16 . 
   When breaking out the individual optical fibers  12 ,  14 , ends of outer jacket  18  and inner jacket  20  are removed exposing a length of optical fibers  12 ,  14 . Outer jacket  18  is terminated at terminal end  22  and inner jacket  20  is terminated at terminal end  24 . Typically, optical fibers  12 ,  14  are connectorized at an opposite end, such as with any of well known connectors, such as SC, FC, ST, or other connectors as desired. An SC connector  100  is shown in FIG.  7 . Connector  100  mates with an appropriate adapter to connect the optical fiber  12 ,  14  to a further cable or to equipment. 
   Typically, optical fibers  12 ,  14  are quite fragile, and susceptible to damage unless otherwise protected in the regions outside of outer and inner jackets  18 ,  20 . An upjacket  30  is provided to protect the individual fibers  12 ,  14  extending past terminal ends  22 ,  24 . Typically, one upjacket  30  is provided for each optical fiber  12 ,  14 . In the illustrated embodiment of device  10 , two optical fibers  12 ,  14  are shown. Other embodiments include a single optical fiber, or more than two optical fibers such as 4, 6, 8, 12 or any other number of fibers as desired. 
   Upjacket  30  includes an inner tube, or buffer tube,  32  for receiving one of the optical fibers  12 ,  14 . Positioned around inner tube  32  is a strength member  34 , such as strands of aramid fiber. Such strength member  34  protects the optical fibers  12 ,  14  from damage, such as during tensile loading. Positioned around inner tube  32  and strength member  34  is an outer tube  36 . Device  10  is used to allow breaking out of optical fibers  12 ,  14  from cable  16  into the individual upjackets  30 . During use, the strength member  34  is crimped or otherwise mechanically joined to device  10 , and an outer heat shrunk tubing or other mechanical attachment surrounds device  10 , and the exposed ends of upjackets  30 , and cable  16  to join the elements together. Loads are transferred between connector  100  and cable  16 , though strength members  34  and device  10 , instead of through the optical fibers  12 ,  14 . 
   Device  10  includes a housing or body  40  having a front end  42  and an opposite rear end  44 . Body  40  defines a longitudinal axis  46  extending between front and rear ends  42 ,  44 . In one preferred embodiment, body  40  is made from metal. 
   Rear end  44  defines an inner bore  48  for receiving cable  16 . Inner bore  48  includes a first inner bore portion or passage  50  having a first inner bore diameter  52  and a second inner bore portion or passage  54  having a second inner bore diameter  56  smaller than first inner bore diameter  52 . Inner bore  48  terminates at end wall  60 . Inner bore  48  further communicates with first passage  62  and second passage  64 . First and second passages  62 ,  64  communicate with first and second tubes  66 ,  68 . 
   Front end  42  connects to the upjackets  30 . In particular, each of first and second tubes  66 ,  68  includes a first tube outer diameter  70  and a first tube inner diameter  72 . First tube inner diameter  72  is sized to receive inner tube  32  of upjacket  30 . Inner tube  32  further receives one of optical fibers  12 ,  14  within inner tube  32 . Tubes  66 ,  68  are offset from axis  46 . Other spacings are possible, but a symmetrical spacing is preferred. As different numbers of tubes are provided, the spacings will vary in order to accommodate different numbers of optical fibers used with device  10 . 
   Strength member  34  of upjacket  30  is positioned adjacent to a crimp surface  76  of body  40  positioned between first and second tubes  66 ,  68  and rear end  44 . Crimp surface  76  defines a second outer diameter  78 . A crimp ring  80  cooperates with crimp surface  76  to crimp to strength member  34 . A plurality of barbs  82  on crimp surface  76  further enhance the crimping of strength member  34  to crimp surface  76 . 
   Outer tube  36  of upjacket  30  is positioned around first tube outer diameter  70  of the respective first and second tubes  66 ,  68 . If desired, a further crimp can be included to crimp outer tube  36  to the respective first and second tubes  66 ,  68 . 
   Body  40  further includes a third outer diameter  86  which is larger than second outer diameter  78 . In the preferred embodiment, second outer diameter  78  is larger than first tube outer diameter  70 . 
   In the preferred embodiment, body  40  includes cut outs  90 ,  92 . Cut outs  90 ,  92  allow access for a user of device  10  to inner bore  48 . Also, cut outs  90 ,  92  can be used to reach in with a tool (tweezers) to pull inner tubes  32  toward inner jacket  20 . In some instances, it may be desirable to insert inner tubes  32  into inner jacket  20 . 
   Referring now to  FIGS. 8 through 14  in addition to  FIGS. 1 through 7 , a preferred method of assembly is shown. In  FIG. 8 , upjackets  30  are shown where two outer tubes  36  are positioned over first and second tubes  66 ,  68 . Strength member  34 , comprised of a plurality of fibers or strands, of each jacket  30  is shown extending from outer tubes  36 , prior to crimping. Inner tubes  32  are shown extending through inner bore  48  and exiting device  10  at rear end  44 . 
     FIG. 9  shows strength members  34  being crimped with a crimp tool  98  to body  40 .  FIG. 10  shows the resulting crimp ring  80  crimped into position. 
     FIG. 11  shows strength members  34  passing into cut outs  90 ,  92  into inner bore  48 . 
     FIG. 12  shows cable  16  with terminal ends  22 ,  24  of outer and inner jackets  18 ,  20  inserted into inner bore  48 . 
     FIG. 13  shows a heat shrinkable tube  96  prior to heat shrinking around device  10 , cable  16 , and upjackets  30 . Tube  96  is any of a known heat shrink device, such as a polyolefin tube with heat activated adhesive inside. 
     FIG. 14  shows tube  96  after the heat shrinking process is completed. 
   Device  10  of the present invention reduces the risk of a fiber breaking within the connector of an upjacket when a tensile load is applied. By crimping strength member  34  to body  40 , slack in strength member  34  is avoided. With prior art techniques, any slack in strength member  34  which was not accounting for, could lead to fiber breakage since any tensile loading would be applied to the fiber, until any slack in strength member  34  was taken up. In the present invention, the strength member  34  is crimped adjacent to the location it exits outer tube  36  of upjacket  30 . Device  10  is then mechanically attached to cable  16 , and to outer tubes  36 , such as with a heat shrunk tubing. IN  FIGS. 15 and 16  strength members  34  of the prior art were attached only at the exposed ends  101  which extended past sleeve  102 . 
   Strength members  34  which extend past crimp ring  80  in the present invention are believed to further assist with attachment of upjacket  30  and device  10  to cable  16 . It is to be appreciated that the extending strength members  34  past crimp ring  80  is optional. 
   The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.