Abstract:
A tunable connector and method for assembling a tunable connector. The connector includes a ferrule that is retainably engaged within a hub. The connector further includes a rear housing and a front housing. The rear housing is sized to receive and rotationally retain the hub. The front housing has a bore that receives and engages the exterior surface of the rear housing. The front and rear housing include engagement members that allow the rear housing to be retained within the front housing and rotated relative to the front housing between discrete positions.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to tunable fiber optic connectors for use in optical fiber signal transmission systems, and to methods for assembling such fiber optic connectors.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fiber optic cables are used in the telecommunication industry to transmit light signals in high speed data and communication systems. A standard fiber optic cable includes a fiber with an inner light transmitting optical core. Surrounding the fiber typically is a reinforcing layer and an outer protective casing.  
           [0003]    A fiber terminates at a fiber optic connector. Connectors are frequently used to non-permanently connect and disconnect optical elements in a fiber optic transmission system. There are many different fiber optic connector types. Some of the more common connectors are FC and SC connectors. Other types of connectors include ST and D4-type connectors.  
           [0004]    A typical SC fiber optic connector includes a housing having a front end positioned opposite from a rear end. The front end of the SC connector housing is commonly configured to be inserted within an adapter. An example adapter is shown in U.S. Pat. No. 5,317,663, the disclosure of which is incorporated by reference. The SC connector typically further includes a ferrule that is positioned within the front and rear ends of the housing, and adjacent the front end. The ferrule is axially moveable relative to the housing, and is spring biased toward the front of the connector. The fiber optic cable has an end that is stripped. The stripped end includes a bare fiber that extends into the connector and through the ferrule.  
           [0005]    A connector, such as the connector described above, is mated to another connector within an adapter like the adapter of U.S. Pat. No. 5,317,663. A first connector is received within the front portion of the adapter, and a second fiber is received within the rear portion of the adapter. When two connectors are fully received within an adapter, the ferrules (and hence the fibers internal to the ferrule) contact or are in close proximity to each other to provide for signal transmission between the fibers.  
           [0006]    Signal losses within a system often occur within the connection between two optical fiber cores. Due to manufacturing tolerances of the ferrule outer diameter to inner diameter concentricity, ferrule inner diameter hole size and fiber outer diameter, and fiber core to fiber outer diameter concentricity, when the fiber is inserted into the ferrule the core of a fiber may not and typically does not end up perfectly centered relative to the ferrule outer diameter. If one or both of the fibers are off center, when they are connected within an adapter, the fibers will not be aligned and thus there will be a signal loss when the signal is transmitted between the two fibers. It is therefore desirable to have a tunable connector that can provide for optimal alignment with another connector so as to minimize signal loss.  
         SUMMARY OF THE INVENTION  
         [0007]    One aspect of the present invention relates to a fiber optic connector. The connector includes a ferrule that is retainably engaged within a hub. The connector further includes a rear housing and a front housing. The rear housing is sized to receive and rotationally retain the hub. The front housing has a bore that receives and engages the exterior surface of the rear housing. The front and rear housing include engagement members that allow the rear housing to be retained within the front housing and rotated relative to the front housing between discrete positions.  
           [0008]    Another aspect of the present invention relates to a method for assembling a fiber optic connector. The method includes providing a ferrule retainably engaging a hub. This assembly is then positioned within the bore of a rear housing with the hub rotationally retained within the bore. Next, the rear housing is inserted into the bore of a front housing, and the rear housing is then rotated within the front housing between discrete positions.  
           [0009]    A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate several aspects of the invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows:  
         [0011]    [0011]FIG. 1 is a side view of an SC-type connector constructed in accordance with the principles of the present invention without the grip;  
         [0012]    [0012]FIG. 2 is a partial cross-sectional side view taken longitudinally through the connector of FIG. 1 between line  2 - 2  without the boot;  
         [0013]    [0013]FIG. 3 is a cross-sectional side view of the connector of FIG. 1 fully assembled including the grip mounted over the front of the connector and a fiber optic cable attached to the connector;  
         [0014]    [0014]FIG. 4 is a cross-sectional side view of the fully assembled connector shown in FIG. 3 rotated 90 degrees to a second orientation about the longitudinal axis;  
         [0015]    [0015]FIG. 5 is a cross-sectional end view taken along line  5 - 5  in FIG. 4;  
         [0016]    [0016]FIG. 6 is a further cross-sectional end view taken along line  6 - 6  in FIG. 4;  
         [0017]    [0017]FIG. 7 is an exploded perspective view of the SC-type connector of the present invention;  
         [0018]    [0018]FIG. 8 is a cross-sectional side view of the hub with connected ferrule used in the SC-type connector of the present invention;  
         [0019]    [0019]FIG. 9 is a cross-sectional side view of the front housing piece of the SC-type connector of the present invention; and  
         [0020]    [0020]FIG. 10 is an enlarged cross-sectional side view showing a portion of the collar on the rear housing piece of the SC-type connector engaging one of the slots in the front housing piece. 
     
    
     DETAILED DESCRIPTION  
       [0021]    Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Where ever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0022]    [0022]FIG. 1 illustrates an SC-type connector  20  constructed in accordance with the principles of the present invention. The connector  20  includes a housing  22  having a front housing  24  that connects to a rear housing  26 . A boot  28  is mounted at the rear end  23  of the connector  20 . The front portion  49  of a ferrule  48  is shown extending out the front end  25  of the connector  20 . The ferrule  48  is mounted to a hub  44  (not shown in FIG. 1) which together are slidably mounted within the connector  20 . As shown, the rear housing  26  is a unitary piece. However, it could alternatively be a constructed of more than one piece such as the two-piece construction shown and described in pending U.S. patent application Ser. No. 09/459,968, filed Dec. 13, 1999, the disclosure of which is expressly incorporated by reference herein.  
         [0023]    For clarity, no fiber optic cable is shown in FIG. 1. Also for clarity, FIG. 1 does not include the slidable outer grip located at the front of the housing that is typically found on an SC-type connector. However, the grip and the cable are shown on other figures and will be described later in the specification in connection with the description of those other figures.  
         [0024]    Referring to FIG. 2, the front housing  24  of the connector  20  extends along a longitudinal axis  30  and includes a front end  32  positioned opposite from a rear end  34 . The front housing  24  also defines a front chamber  36  and a rear chamber  38 . A transverse wall  40  separates the front and rear chambers  36  and  38 . An opening  42  centered about the longitudinal axis  30  is defined by the transverse wall  40 . The front and rear ends  32  and  34  of the front housing piece  24  are open with a bore  33  (see FIG. 4) formed therebetween extending along longitudinal axis  30 .  
         [0025]    The connector  20  also includes a hub  44  positioned within the connector  20 . The hub  44  is mounted to slide longitudinally along the axis  30  relative to the front housing piece  24 . The hub  44  has openings  45  and  47  at its front and rear portions  55  and  57  with a bore  53  extending between the openings.  
         [0026]    The hub  44  secures a ferrule  48 . The ferrule  48  includes a rear portion  51  mounted within the front opening  45  defined by the hub  44 . The ferrule  48  may be secured to the hub  44  using a conventional fastening technique, such as an epoxy adhesive. The hub  44  can also be mounted to the ferrule  48  with an interference fit or it can be molded around the ferrule  48 . The ferrule  48  includes a bore  59  for receiving a bare optical fiber. The ferrule  48  extends along the longitudinal axis  30  from the hub  44  toward the front end  32  of the front housing piece  24 . The ferrule  48  extends through the central opening  42  of the transverse wall  40  between the front and rear chambers  36  and  38  of the front housing piece  24 , and protrudes out from the front end  23  of the connector  20 .  
         [0027]    The connector  20  further includes a coil spring  56  positioned within the rear chamber  38 . The coil spring  56  surrounds the rear portion  57  of the hub  44  and is captured between a forwardly facing shoulder  58  formed by the rear housing piece  26  and a rearwardly facing shoulder  60  formed by the hub  44 . The spring  56  functions to bias the hub  44  toward the front end  32  of the front housing piece  24 . Because the ferrule  48  is connected to the hub  44 , the spring  56  also functions to bias the ferrule  48  in a forward direction.  
         [0028]    The rear housing  26  also extends along longitudinal axis  30  and includes a front end  62  positioned opposite from a rear end  64 . The hub  44  and surrounding spring  56  slide into the opening  27  at the front end  62  of the rear housing  26 . The hub  44  and spring  56 , however, are not mechanically fastened to the rear housing  26 , and thus are free to move longitudinally along axis  30  with respect to the rear housing  26 . The only limit placed on the rearward movement of the hub  44  and spring  56  into the rear housing  26  is the forward facing shoulder  58  on the rear housing  26  which, as mentioned above, engages the spring  56 . The engagement of the spring  56  to the shoulder  58  functions to bias the hub  44  and connected ferrule  48  outward from the opening  27  at the front end  62  of the rear housing  26 .  
         [0029]    The front portion  55  of the hub  44  and the opening  27  at the front end  62  of the rear housing  26  are sized so that the hub  44 , when received within the rear housing  26 , cannot be rotated within the rear housing  26 . Likewise, the ferrule  48 , which is secured to the hub  44 , does not rotate relative to the rear housing  26  when the hub  44  is fully inserted therein. This can be achieved by having a non-circularly shaped hub  44  and a corresponding non-circularly shaped opening  27  at the front end  62  of the rear housing  26 . In the embodiment shown, the hub  44  and the opening  27  to the rear housing  26  have the same non-noncircular shape so that the hub  44  can only be received within the opening  27  in one orientation. As shown in FIG. 7, the outer circumference of the hub  44  and opening in the rear housing  26  are each defined by three planar sides  100  and an arched side  103 . This configuration permits the hub  44  to be received within the rear housing  26  in only one orientation, and once received within the opening, the hub  44  (and ferrule  48 ) is not rotatable relative to the rear housing  26 . It can be appreciated that other configurations could be used which allow the hub  44  to be inserted into the rear housing  26  in multiple orientations but not be rotatable once the hub  44  is received within the rear housing  26 .  
         [0030]    Further details of the front housing  24  can be seen in FIGS. 7 and 9. The rear portion  34  of the front housing  24  includes two extensions  66  and  68  that define the opening  29  at the rear portion  34 . The extensions  66  and  68  also define two tapered cut-outs  70  that extend longitudinally toward the front end  32  of the front housing  24  on two of the sides of the front housing  24  (see FIG. 7 showing one of the tapered cut-outs  70  on the top-facing side of the front housing  24 ). The cut-outs  70  give the extensions  66  and  68  a resiliency allowing them to be deflected outward when suitable pressure is applied from within the opening  29 . On the inside of each of the resilient extensions  66  and  68  proximate the opening  29  at the rear end  34  are a pair of projections, or teeth  74  and  76 , extending into the bore  33  of the front housing  24  (see FIG. 5). Each of the pairs of teeth  74  and  76  defines a recess  78  therebetween. Adjacent the pairs of teeth  74  and  76  are slots  80  formed within the resilient extensions  66  and  68 .  
         [0031]    As noted above, the front housing  24  connects to the rear housing  26 . The front end  62  of rear housing  26  is received into the opening  29  at the rear end  34  of the front housing  24 . A collar  82  extends around the external surface of the rear housing  26 . When the rear housing  26  is inserted into the opening  29  of the front housing  24 , the collar  82  presses up against the pairs of teeth  74  and  76  that project into the bore  33  of the front housing  24 , inhibiting further insertion of the rear housing  26  into the front housing  24 . However, when added longitudinal pressure is applied by the rear housing  26  against the front housing  24 , the resilient extensions  66  and  68  are deflected outward which increases the opening  29  slightly to allow the collar  82  to pass over the pairs of teeth  74  and  76 . Immediately after passing over the two pairs of teeth  74  and  76 , the collar  82  snaps into the adjacent slots  80  formed in the front housing  24 . When that occurs, the resilient extensions  66  and  68  quickly return to their natural positions, which secures the rear housing  26  to the front housing  24 . FIG. 10 shows a cross-sectional view of the collar  82  retained within one of the slots  80 . Forward and backward facing shoulders  86  and  88  on the front housing  24 , which define the slot  80 , prevent longitudinal movement of the mounted rear housing  26  relative to the front housing  24  when the collar  82  is positioned within the slots  80 .  
         [0032]    The front and rear housings  24  and  26  further include structure that inhibits rotational movement of the rear housing  26  when it is snapped into the front housing  24 . Adjacent the collar  82  on the rear housing  26  is a ring of projections, or teeth  90 , that extend outward around the circumference of the rear housing  26 . The exemplary embodiment shown includes twelve evenly spaced teeth  90  formed around the circumference of the rear housing  26 . These projections  90  are seen most clearly in FIGS. 5 and 7. When the collar  82  snaps into the slots  80  on the front housing  24 , as described above, the ring of teeth  90  on the external surface of the rear housing  26  at the same time engages and is aligned with the pairs of internally projecting teeth  74  and  76  within the bore  33  of the front housing  24 . Each of the teeth  90  on the rear housing  26  are sized to be received within the recesses  78  formed between the pairs of teeth  74  and  76 . As such when the rear housing  26  is snapped into the front housing  24 , two of the teeth  90  on directly opposite sides are forced into the recesses  78  formed on the opposing resilient extensions  66  and  68  of the front housing  24 . This engagement is shown in FIG. 5. With this arrangement, the rear housing  26  is not freely rotatable within the front housing  24 , but is held at a discrete position. However, if the rear housing  26  is twisted relative to the front housing  24  with sufficient rotational pressure, the resilient extensions  66  and  68  will deflect outward slightly, allowing the rear housing  26  to be rotated within the front housing  24  to a second position with a new set of opposing teeth  90  on the rear housing  26  engaging the recesses  78 . Because there are twelve different teeth  90  on the rear housing  26  in the exemplary embodiment, there are twelve different discrete rotational positions that can be selected when rotationally positioning the rear housing  26  within the front housing  24 . It is understood that the number and configuration of the projections on the front and rear housings  24  and  26  could be altered without departing from the scope of the present invention. Other structure for providing the selection of discrete rotational positions of the inserted rear housing  26  with respect to the front housing  24  could also be used that are consistent with the teachings of this invention.  
         [0033]    The connector  20  further includes a grip  92 . The connector housing  22  inserts into a bore  93  formed within the grip  92 . The front housing  24  includes structure that mounts the connector housing  22  within the grip  92 . When the connector housing  22  is positioned within the grip  92 , the grip  92  restrains the resilient extensions  66  and  68 , preventing them from deflecting outward. As such, rotational alignment between the front and rear housings  24  and  26 , via the interlocking teeth on the housings, cannot be further altered once the grip  92  is positioned over the connector housing  22 . The external surface of the connector housing  22  and the bore  93  of the grip  92  are configured such that the connector housing  22  can be fully inserted into the grip  92  in only one orientation. Alternatively, the connector housing  22  could include other types of external keys. The external surface of the grip  92  includes a key  94  (seen in FIGS. 4 and 7) that is sized to be received into a slot of an adaptor (not shown), such as the adapter of U.S. Pat. No. 5,317,663, where the connector mates with a second SC-type connector. As described in the method of assembly below, with this configuration, prior to locking the rotational orientation of the connector housing  22 , the connector  20  can be tuned and the front and rear housings  24  and  26  rotated relative to one another to align with a key on the connector housing  22 .  
         [0034]    The present invention is further directed to a method for assembling the SC-type connector described above. The ferrule  48  is first mounted within the opening  45  formed in the front portion  55  of the hub  44 . A cross-sectional side viewing of this arrangement is shown in FIG. 8. The spring  56  is then positioned over the rear portion  57  of the hub  44 , and together these are inserted into the front end  62  of the rear housing  26 . As mentioned above, the front portion  55  of the hub  44  is sized so that when it is inserted into the rear housing  26  the hub  44  (and connected ferrule  48 ) cannot rotate relative to the rear housing  26 .  
         [0035]    Next, the rear housing  26  is snapped into the front housing  24 , thereby retaining the hub  44  and ferrule  48  (and spring  56 ) within the connected housing  22 . This connection is made to prevent longitudinal movement of the rear housing  26  relative to the front housing  24 . However, the engagement does not prevent rotational movement between the two housings  24  and  26 .  
         [0036]    At this point, a fiber optic cable  96 , having a central fiber  98 , is attached to the connector  20  using conventional techniques well known in the art. This includes stripping the end of the cable  96  to expose the fiber  98 . The fiber  98  is then fed into the connector  20  all the way through the bore  59  in the ferrule  48 . The fiber may be either mechanically or adhesively retained within the ferrule  48 . A reinforcement layer of the fiber optic cable  96  is crimped with a crimp sleeve  71 . The boot  28  is positioned over the crimp  71  and helps provide strain relief. The exposed bare fiber at the front end  49  of the ferrule  48  may then be polished.  
         [0037]    The connector  20  is then tuned. This includes measuring the eccentricity with appropriate test equipment to identify, for example, any offset of the optical core within the fiber  98  or offset of the fiber  98  within the ferrule  48 . After determining the direction of any such offset, the rear housing  26  is rotated within the front housing  24  to one of the selectable discrete positions. Those positions are defined by the rotational positions of the projections  90  on the external surface of the rear housing  26  that engage a corresponding alignment feature, such as a recess  78  between a pair of projections (e.g., pairs of teeth  74  and  76 ), on the internal surface of the front housing  24 . A position is selected that will minimize signal loss when the connector  20  is mated with another connector within an adaptor. As mentioned, the front housing  24  has a shape that permits insertion of it into a grip  92  in only one orientation. As shown in FIG. 6, the grip  92  includes tabs  95  and  97  that block access of the connector housing  22  into the grip  92  if the housing  22  is improperly orientated. Thus, the discrete position is selected to align with the orientation in which the connector  20  is to be inserted within the grip  92 . In this way, the configuration of the housing serves as a key to which the selectable discrete position is aligned. Other alternative keys could be included on the housing to align with the selectable discrete position.  
         [0038]    Finally, once the proper rotational position is selected, connector  20  is inserted within a grip  92 . The grip  92  prevents the extensions  66  and  68  from deflecting outward, and thus rotationally locks the rear housing  26  to the front housing  24  at the previously-selected discrete position. The connector  20  can then be inserted into an adaptor (not shown) for mating with a second SC-type connector.  
         [0039]    With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size and arrangement of the parts without departing from the scope of the present invention. It is intended that the specification and depicted aspects be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the following claims.