Abstract:
A connector is disclosed for use with a fiber optic cable. The connector of the present invention includes a housing portion having a first end and a second end, the first end for mating with a second connector, the second end for receiving the fiber optic cable, the housing further including a cavity formed therein. A strain relief member communicates between the second end of the housing and the fiber optic cable for providing support therebetween. The connector further includes a lead-in tube disposed in the cavity, the lead-in tube having first fiber passageways formed therein. A ferrule is disposed in the cavity adjacent the lead-in tube. The ferrule includes a removable insert, the insert having second fiber passageways formed therein. The ferrule insert is further composed of a material which readily bonds with a quick-curing adhesive.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. provisional patent application serial No. 60/225,116, filed Aug. 14, 2000, the entire contents of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    An optical connector arrangement  10 , as shown in FIGS. 1 and 2, generally provides an arrangement for the mating of optical fibers, particularly, the mating of two pairs of optical fibers. Arrangement  10  includes connectors  12  which mate at an adapter  14 .  
           [0003]    Connector  12  generally includes a housing  16  having a lead-in tube  18  releasably connected therein and extending from a rear portion of housing  16 . Lead-in tube  18  is fitted with a spring  20 . Lead-in tube  18 , spring  20 , and the rear portion of connector housing  16  are mounted within a strain relief boot  22  to form connector  12 . A fiber optic cable  24  is terminated at connector  12  such that fibers  26  are passed through lead-in tube  18  and connector housing  16 , extending therefrom for mating within adapter  14 .  
           [0004]    Connector  12  further includes a ferrule  28  located within connector housing  16 . Ferrule  28  contains fibers  26  and allows passage there through to the exterior of connector housing  16 . At a back end  30 , ferrule  28  communicates with lead-in tube  18 . At a front end  32 , ferrule  28  emerges from connector housing  16  exposing fibers  26 . Fibers  26  may be cleaved and polished as known in the art. Connector housing  16  and ferrule  28  are typically formed of a plastic material. Ferrule  28  may be integral with connector housing  16  or ferrule  28  may be slidably received by connector housing  16 .  
           [0005]    Fibers  26  are seated within ferrule  28  by an adhesive bonding process. First, an adhesive epoxy is mixed. The epoxy is then loaded into a syringe. The syringe is used to inject the epoxy into back end  30  of ferrule  28 . Fibers  26  are inserted into ferrule  28  such that the fibers  26  protrude from front end  32  of ferrule  28  by typically ½ inch. Cable  24  is properly seated and mated with connector housing  16 , lead-in tube  20 , and strain relief boot  22 . Now fibers  26  are disposed within ferrule  28  and are coated and surrounded by the injected adhesive epoxy. Further cable  24  is connectorized with connector  12 .  
           [0006]    The next step in the process of adhesively bonding fibers  26  within ferrule  28  is the curing of the epoxy. The connectorized connector  12  is installed into a curing holder. The curing holder serves to protect fibers  26  protruding from connector housing  16  from damage that could occur from handling during curing of the epoxy. Connector  12  and the curing holder are placed into a curing oven. The curing oven, generally, includes a hot plate having approximately 12 to 20 holes formed therein for receiving connector  12  and the curing holder. Connector  12  is subjected to a predetermined temperature for a predetermined time period, thus curing the adhesive epoxy located within ferrule  28  and securing fibers  26  therein.  
           [0007]    The remaining steps of the bonding process involve cleaning and preparing front end  32  of ferrule  28 . Fibers  26  protruding from connector housing  16  are cleaved using a pocket pen style scriber, removing the cleaved portion of fibers  26  with a straight, non-twisting pull, and disposing of the removed portion. Then, excess epoxy is removed from front end  32  of ferrule  28  using a relatively coarse grit polishing film. The tips of fibers  26  protruding from ferrule  28  are polished to a desired smoothness using increasingly finer grit films. Finally, front end  32  of ferrule  28  and the exposed portion of fibers  26  are cleaned, connector  12  is inspected, tested, and placed into use.  
           [0008]    The process of adhesively bonding fibers  26  within ferrule  28  is neither convenient nor economical for field terminations of connector  12 . As mentioned, this process requires an installer to use an oven to cure the epoxy. The oven constitutes an additional piece of equipment to be purchased, maintained, and carried by the installer, thus adding to the cost and heightening the inconvenience of terminating connectors  12 . Further, use of the oven presents the installer with added concerns of personal and work place safety due to heightened temperatures associated with curing oven operation. Additionally, the curing time of adhesive epoxies used with plastic ferrule  28  can be excessive causing termination delays reducing overall installation efficiency. For instance, a typical adhesive epoxy takes one-half hour to cure in a curing oven at 120° C.  
           [0009]    Thus, it would be advantageous to have a fiber optical connector having a ferrule capable of fiber installation in a short time period and without the use of high temperature curing ovens.  
         SUMMARY OF THE INVENTION  
         [0010]    A connector is disclosed for use with a fiber optic cable. The connector of the present invention includes a housing portion having a first end and a second end, the first end for mating with a second connector, the second end for receiving the fiber optic cable, the housing further including a cavity formed therein. A strain relief member communicates between the second end of the housing and the fiber optic cable for providing support therebetween. The connector further includes a lead-in tube disposed in the cavity, the leadin tube having first fiber passageways formed therein.  
           [0011]    A ferrule is disposed in the cavity adjacent the lead-in tube. The ferrule includes a removable insert, the insert having second fiber passageways formed therein. The ferrule insert is further composed of a material which readily bonds with a quick-curing adhesive.  
           [0012]    The fibers pass from the cable into the cavity at the second end of the housing where the fibers pass through the first and second fiber passageways to the first end of the housing for mating with the second connector. The fiber is bonded within the second fiber passageway to the insert using a quick drying adhesive.  
           [0013]    The ferrule with bondable insert of the present invention allows a convenient and simple means of setting optical fibers within the ferrule and further provides for the efficient termination of a fiber connector. The exemplary ceramic composition of the ferrule serves as an appropriate substrate to allow bonding of optical fiber thereto using a quick-curing adhesive agent. Thus, no oven or associated elevated temperatures are necessary in the setting of the fibers reducing complexity of the process and ensuring worker and workplace safety. Yet, the ferrule, itself, remains of a plastic composition, retaining functionality within the fiber optic connector. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:  
         [0015]    [0015]FIG. 1 is a perspective view of a conventional fiber optic connector arrangement;  
         [0016]    [0016]FIG. 2 is a cross-sectional view of a fiber optic connector of FIG. 1;  
         [0017]    [0017]FIG. 3 is a front perspective view of one embodiment of a fiber optic connector according to the present invention;  
         [0018]    [0018]FIG. 4 is a rear perspective view of the fiber optic connector of FIG. 3;  
         [0019]    [0019]FIG. 5 is a front perspective exploded view of the fiber optic connector of FIG. 3;  
         [0020]    [0020]FIG. 6 is a front elevational view of the fiber optic connector of FIG. 3;  
         [0021]    [0021]FIG. 7 is a cross-sectional view of the fiber optic connector of FIG. 6 along line  7 - 7 ;  
         [0022]    [0022]FIG. 8 is a cross-sectional view of the fiber optic connector of FIG. 6 along line  8 - 8 ;  
         [0023]    [0023]FIG. 9 is a perspective view of one embodiment of a ferrule according to the present invention;  
         [0024]    FIGS.  10 - 11  are side elevational views of the ferrule of FIG. 9;  
         [0025]    [0025]FIG. 12 is a front elevational view of the ferrule of FIG. 9;  
         [0026]    [0026]FIG. 13 is a rear elevational view of the ferrule of FIG. 9;  
         [0027]    [0027]FIG. 14 is a cross-sectional view of the ferrule of FIG. 13 along line  14 - 14 ;  
         [0028]    [0028]FIG. 15 is an enlarged view of the ferrule of FIG. 14;  
         [0029]    [0029]FIG. 16 is a front perspective view of one embodiment of the ferrule insert of FIG. 13;  
         [0030]    [0030]FIG. 17 is a front elevational view of the ferrule insert of FIG. 16;  
         [0031]    [0031]FIG. 18 is a cross-sectional view of the ferrule insert of FIG. 17 along line  18 - 18 ;  
         [0032]    FIGS.  19 - 20  are various enlarged views of the ferrule insert of FIG. 18; and  
         [0033]    [0033]FIG. 21 is an elevational view of a partially stripped fiber optic cable. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    FIGS.  3 - 8  present various views of a fiber optic connector  100 . Connector  100  includes a front housing  102  having a front end  104  and a rear end  106  located opposite one another. Front end  104  includes flanges  108  to facilitate mating connector  100  with a fiber optic adapter such as that shown in FIG. 1. Front housing  102  also includes a latching key  110  to further facilitate mating connector  100  with a fiber optic adapter. Rear end  106  of front housing  102  includes an opening  112  and latch holes  114  formed therein for receiving a rear housing  116  of connector  100 . A passageway is formed on an interior of connector  100 , traversing the length thereof from front end  104  to rear end  106 .  
         [0035]    Rear housing  116 , as best shown in FIG. 5, includes a front end  118  and an opposing rear end  120 . Rear housing  116  includes extensions  122  having latch flanges  124  formed thereon, extensions  122  being located at front end  118 . Extensions  122  are received by opening  112  of front housing  102  and latch flanges  124  are received by latch holes  114  to mate front and rear housing  102 ,  116 .  
         [0036]    Rear housing  116  also includes a passage way  126  traversing the length of the housing from front end  118  to rear end  120 . Finally, rear housing  116  includes a cable portion  128  for mating with an unsheathed portion of a fiber optic cable as described in greater detail herein. A strain relief boot  130  fits over the cable portion  128  to enhance reception of and mating with an optical cable.  
         [0037]    Fiber optic connector  100  further includes a lead-in tube  132 , best shown in FIG. 5, having a tube portion  134  and an opposing plug portion  136 . Tube portion  134  is received into passageway  126  of rear housing  116  upon assembling connector  100 . A spring  138  is located about the tube portion  134  of lead-in tube  132  such that lead-in tube  132  and rear housing  116  interact elastically relative one another, biased about spring  138 . Lead-in tube  132  includes fiber passages  140  formed therein from tube portion  134  to plug portion  136 , through which optical fibers traverse the length of lead-in tube  132 .  
         [0038]    Plug portion  136  of lead-in tube  132  includes a raised portion  133  extending away from the plug portion. Raised portion  133  includes mating openings  142  formed therein to facilitate assemblage of the connector  100 .  
         [0039]    Fiber optic connector  100  additionally includes a ferrule  144  as shown in FIGS.  5 - 15 . Ferrule  144  has opposing front and rear ends  146 , 148 . Front end  146  is shaped and sized to be received through rear opening  112  of front housing  102  and retained in the passageway formed therein. Rear end  148  of ferrule  144  is shaped and sized to receive plug portion  136  of lead-in tube  132 .  
         [0040]    More specifically, rear end  148  of ferrule  144  includes a receptacle  150  having an opening  152  sized and shaped to receive raised portion  133  of lead-in tube  132 . Ferrule  144  also includes an insert chamber  154  formed therein having an opening  156  located within receptacle  150 . Insert chamber  154  extends the longitudinal length of ferrule  144  from rear end  148  to front end  146  where insert chamber  154  terminates at wall  157 . Wall  157  is formed at front end  146  of ferrule  144  and serves as a partition between insert chamber  154  and an exterior of ferrule  144 . Wall  157  includes a plurality of fiber bores  158  formed therein for allowing passage therethrough of optical fibers. Fiber bores  158  include funnel receptors  159  formed in wall  157  adjacent insert chamber  154  for facilitating reception of fibers within bores  158  and passage therethrough. Further, as discussed herein, funnel receptors  159  facilitate in assembling fiber optic connector  100 . In an exemplary embodiment of the present invention, ferrule  144  includes two fiber bores  158  formed adjacent one another with two corresponding funnel receptors  159 .  
         [0041]    Adjacent and parallel to insert chamber  154 , a plurality of post passageways  160  are formed in ferrule  144 . Post passageways  160  extend the longitudinal length of ferrule  144  and have front openings  162  formed at front end  146  and rear openings  164  formed at rear end  148  within receptacle  150 . In an exemplary embodiment, ferrule  144  is made of a plastic material.  
         [0042]    Fiber optic connector  100  further includes alignment posts  166  as shown in FIGS.  3 - 6 , and  8 . Upon fully assembling fiber optic connector  100 , posts  166  pass through and are retained within post passageways  160  of ferrule  144 . Posts  166  thus extend from front and rear ends  146 , 148  of ferrule  144  a predetermined distance. Posts  166  include mating tips  168  which extend from rear end  148  of ferrule  144  and are received and retained within mating holes  142  of plug portion  136  of lead-in tube  132 . Posts  166  serve to align, stabilize and secure the connection of lead-in tube  132  and ferrule  144 . Additionally, posts  166  extending from front end  146  of ferrule  144  participate in connecting fiber optic connector  100  to another connector within a fiber optic adapter.  
         [0043]    Fiber optic connector  100  additionally includes a ferrule insert  170  as shown in FIGS.  5 - 8 , and  16 - 19 . Ferrule insert  170  is generally sized and shaped to be received and retained within insert chamber  154  of ferrule  144 . In an exemplary embodiment, ferrule insert  170  is an elongated rectilinear solid sized such that ferrule insert may be slidably received by ferrule  144  within insert chamber  154  and retained therein by resulting frictional forces.  
         [0044]    Ferrule insert  170  includes a front end  172  and an opposing rear end  174 . A plurality of fiber passageways  176  are formed within ferrule insert  170  and traverse the longitudinal length of ferrule  170  from front end  172  to rear end  174 . In an exemplary embodiment of the present invention, ferrule insert  170  includes passageways  176  for two optical fibers. Fiber passageways  176  are generally circular in cross-section and have an area sufficient to contain optical fibers and a volume of adhesive agent necessary for bonding the fiber therein.  
         [0045]    At front end  172 , ferrule insert  170  includes front openings  178  of fiber passageways  176  which expose the passageways to the exterior of the insert. Similarly, rear openings  180  of fiber passageways  176  are located at rear end  174  of ferrule insert  170 .  
         [0046]    Front openings  178  include annular flanges  182  formed thereabout extending from ferrule insert  170 . Front openings  178  include mouth portions  184  located within annular flanges  182 . Mouth portions  184  are larger in cross-sectional area than that of fiber passageways  176 . Annular flanges  182  and enlarged mouth portions  184  facilitate mating of ferrule insert  170  with ferrule  144  and passage of optical fibers therebetween, as discussed in greater detail herein.  
         [0047]    In a preferred embodiment, rear openings  180  include a mouth portion  186  formed proximate rear end  174  and a funnel portion  188  formed distal rear end  174 . Funnel portion  188  is frustoconical in shape with a tapered end in communication with fiber passageways  176 . A cross-sectional area of mouth portions  186  of rear openings  180  is greater than the largest cross-sectional area of conically shaped funnel portion  188 . Mouth and funnel portions  186 ,  188  of rear openings  180  aid in the reception of optical fibers into fiber passageways  176  and promote a delivery of the adhesive agent thereto.  
         [0048]    In one embodiment, ferrule insert  170  is composed of a material which would perform adequately as a substrate for the adhesive agent and promote rapid curing thereof. Specifically, ferrule insert  170  is composed of a material to which a quick-cure adhesive would readily cure. Still more specifically, ferrule insert  170  is composed of ceramic or a ceramic composite or ceramic-like material. Alternatively, ferrule insert  170  may be made from glass or metal.  
         [0049]    Now the assembling of fiber optic connector  100  and the termination of a fiber optic cable  190  therewith will be described with reference to FIGS.  1 - 21 .  
         [0050]    First, optical fibers  192  must be set within ferrule insert  170 . Cable jacket and various insulating layers  194  are stripped from a desired portion of fiber optic cable  190  and, thus, fibers  192  exposed. Tube portion  134  of lead-in tube  132  is passed through spring  138  and enters passageway  126  of rear housing  116  and seats therein. Cable  190  is passed through strain relief boot  130  and brought proximate rear housing  116 . Fibers  192  are inserted into passage  126  of rear housing  116  and therein fibers  192  are further inserted into passages  140  of lead-in tube  132 . Fibers  192  are passed through the length of lead-in tube  132  until fibers  192  emerge from the plug portion  136 . A sufficient length of fibers  192  is extended from lead-in tube  132 .  
         [0051]    A quick curing adhesive is now injected into fiber passageways  176  at rear end  174  of ferrule insert  170  in such a volume as to encapsulate fibers  192  upon insertion thereof into the passageways. Promptly, fibers  192  are inserted into rear openings  180  of ferrule insert  170 . The mouth and funnel portions  186 , 188  of rear openings  180  facilitate ease of inserting fibers  192 . Insertion of fibers  192  is continued until fibers  192  pass through the length of passageways  176  and emerge from the front openings  178  and extend from the ferrule insert a desired distance. The quick curing adhesive is allowed to cure.  
         [0052]    The adhesive may be any of a plurality of quick-curing adhesives currently available. In a preferred embodiment, the quick-curing adhesive is one which would most effectively bond with ferrule insert  170  made of ceramic and fibers  192  of glass in the shortest amount of time. The adhesive may be an acrylic adhesive or a two-part acrylic adhesive. An exemplary quick curing adhesive is a two-part acrylic adhesive commercially available as the LIGHTSPEED (TM) adhesive, having an approximate curing time of thirty seconds.  
         [0053]    The adhesive is preferably air cured and has a cure time between about 10 seconds and 60 seconds, and more specifically about 30 seconds. This provides rapid curing, but sufficient time for an installer to insert a fiber through the adhesive. Conventional adhesives having cure times of about 5 seconds can harden too quickly before the fiber is inserted through the ferrule. In this situation, the fiber end is trapped in the interior of the ferrule.  
         [0054]    Accordingly, fibers  192  are now fixably set within ferrule insert  170 . Preferably, ferrule insert  170  is positioned within ferrule  140  prior to application of the adhesive. Alignment posts  166  may also be position through front openings  162 , passed through post passageways  160 , and extended from rear openings  164 . Fibers  192  extending from the ferrule  140  are subsequently cleaved and polished sufficiently so as to ultimately allow connection with another set of optical fibers in, for example, a fiber optic adapter.  
         [0055]    Now, ferrule  144  is brought proximate lead-in tube  132  and positioned such that raised portion  133  of plug portion  136  is received within receptacle  150  of ferrule  144 . In so doing, fiber passages  140  of lead-in tube  132  align with fiber passageways  176  of ferrule insert  170 , the insert now being located within insert chamber  154  of ferrule  144 . Mating tips  168  of alignment posts  166  are received and retained within mating holes  142  of lead-in tube  132 . Thus, lead-in tube  132  and ferrule  144  are now releasably connected.  
         [0056]    Next, front housing  102  is drawn toward rear housing  116  such that the ferrule/ferrule insert/lead-in tube assembly is received within the passageway in the interior of front housing  102 . The ferrule/ferrule insert/lead-in tube assembly is inserted into front housing  102  until latch flanges of the rear housing snap-latch with latch holes  114  of the front housing. Alignment posts  166  and fibers  192  extend from front end  104  of housing  102 . Fibers  192  are cleaved and polished at front end  104  of front housing  102  for connection with other optical fibers.  
         [0057]    It is understood that the connector may be assembled using various ordering of steps. For example, the lead-in tube  132 , ferrule  144 , front housing  102  (and interior components) may be assembled prior to injecting the adhesive. In addition, the rear housing  116  and spring  138  may be joined to front housing  102  prior to injecting the adhesive. Thus, the order of assembly may vary.  
         [0058]    The ferrule with bondable insert of the present invention allows a convenient and simple means of setting optical fibers within the ferrule and further provides for the efficient termination of a fiber connector. The exemplary ceramic composition of the ferrule serves as an appropriate substrate to allow bonding of optical fiber thereto using a quick-curing adhesive agent. Thus, no oven or associated elevated temperatures are necessary in the setting of the fibers reducing complexity of the process and ensuring worker and workplace safety. Yet, the ferrule, itself, remains of a plastic composition, retaining functionality within the fiber optic connector.