Abstract:
A fiber optic connector for mounting on a panel comprises an outer housing defining an interior passage extending longitudinally therethrough, and at least one mounting element connected with the outer housing for mounting the connector onto the panel. The connector also includes a connector insert subassembly inserted through the rear end of the outer housing into the interior passage thereof. The connector insert subassembly is slidable longitudinally within the outer housing, and comprises an inner housing defining an inner passage extending longitudinally therethrough, and a ferrule holder and ferrule mounted within the inner passage of the inner housing. A compression spring is inserted into the rear end of the outer housing abutting the connector insert subassembly, and a spring retainer is inserted into the outer housing behind the compression spring to capture the spring in a compressed condition so as to cause the spring to bias the connector insert subassembly forwardly against a stop defined by the outer housing.

Description:
FIELD OF THE INVENTION 
     The present invention relates to fiber optic connectors. The invention relates more particularly to fiber optic connectors that can be mounted on a circuit board, backplane, or other panel, and that are compatible with standard adapters and other fixtures such as polishing fixtures that are commonly used. 
     BACKGROUND OF THE INVENTION 
     Fiber optic connectors are attached at to ends of optical fibers to enable one or more optical fibers to be optically coupled with one or more other optical fibers of another connector or other optical transmission device. A fiber optic connector generally includes a housing in which a forwardly projecting ferrule is mounted. Usually, one or more optical fibers pass through the ferrule and have ends that are flush with or project slightly beyond the forward end of the ferrule for coupling with the end of one or more other optical fibers in a complementary fiber optic connector or device. The housing of the connector typically includes features for locking the connector in engagement with the complementary connector or device. 
     In some applications, it is desirable to mount a fiber optic connector on a circuit board, backplane, or other panel. Various panel-mountable fiber optic connectors have been developed. U.S. Pat. No. 5,245,683 shows one such panel-mounted connector, comprising a housing, a cylindrical ferrule, and a ferrule holder adapted to be secured around the ferrule. The ferrule holder has a flange and the housing has a rearwardly facing shoulder against which the flange of the ferrule holder abuts when the ferrule holder is inserted through the rear end of the housing. A spring is inserted into the rear end of the housing behind the ferrule holder, and the spring engages the flange of the ferrule holder. The legs of a U-shaped spring-retaining clip are inserted transversely into the housing through openings therein for holding the spring in a compressed position so that the spring biases the ferrule holder and ferrule forwardly. The spring allows the ferrule to “float” to facilitate close coupling of the ferrule with the ferrule of another connector. The housing is molded of plastic and has a pair of integrally formed projecting pegs for inserting into holes in a circuit board to mount the connector on the board. The spring-retaining clip can be removed while the connector remains mounted on the board, so that the ferrule holder and ferrule can be removed from the housing for repair or replacement. 
     Another type of panel-mounted connector that is commercially available is an SC compatible connector that has a ferrule holder that can be oriented in one of four different positions rotationally displaced from one another about the axis of the ferrule for “tuning” the direction of the concentricity of the optical fiber in the ferrule with respect to the housing of the connector. A disadvantage of this connector is that the ferrule concentricity angle cannot always be optimized, and thus the insertion loss cannot always be minimized. Another disadvantage of this connector is that it is not compatible with standard automated SC polishing fixtures that are used for other SC connectors, and hence the ferrule must be manually polished. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above needs by providing a panel-mounted (or board-mounted) fiber optic connector that, in preferred embodiments of the invention, can be used in automated polishing fixtures and is compatible with standard adapters. The connector preferably also includes a “pre-tuned” ferrule holder and ferrule assembly whose concentricity angle is in a predetermined orientation, the ferrule holder being mountable in the connector in only one orientation so that the concentricity angle is always in a predetermined orientation relative to the connector. 
     To these ends, a fiber optic connector in accordance with one preferred embodiment of the invention comprises an outer housing defining an interior passage extending longitudinally therethrough, and at least one mounting element connected with the outer housing for mounting the connector onto a panel. The connector also includes a connector insert subassembly inserted through the rear end of the outer housing into the interior passage thereof. The connector insert subassembly is slidable longitudinally within the outer housing, and comprises an inner housing defining an inner passage extending longitudinally therethrough, and a ferrule holder, ferrule, and a spring mounted within the inner passage of the inner housing. A compression spring is inserted into the rear end of the outer housing abutting the connector insert subassembly, and a spring retainer is inserted into the outer housing behind the compression spring to capture the spring in a compressed condition so as to cause the spring to bias the connector insert subassembly forwardly against a stop defined by the outer housing. 
     Preferably, the ferrule holder and ferrule are slidable as a unit in the longitudinal direction within the inner housing, and the connector insert subassembly further comprises a ferrule spring and a member connected with the inner housing for compressing the ferrule spring between the member and the ferrule holder such that the ferrule spring biases the ferrule holder forwardly against a stop defined by the inner housing. A forward portion of the ferrule preferably projects longitudinally forward out a forward end of the inner housing when the ferrule holder is biased forward by the ferrule spring against the stop of the inner housing. The forward end of the inner housing preferably also projects longitudinally forward out the forward end of the outer housing when the connector insert subassembly is biased forward by the compression spring against the stop of the outer housing. 
     In the preferred embodiment of the invention, the outer housing defines openings through opposite side walls thereof, and the inner housing includes projections that are accessible through the openings in the outer housing for engagement with resilient fixing members of a polishing fixture. Thus, the connector can be inserted into the polishing fixture of polishing apparatus until the resilient fixing members of the polishing fixture engage the projections on the inner housing of the connector, thereby securing the connector in the fixture. The outer housing preferably also includes ramp surfaces proximate the openings through the side walls thereof, the ramp surfaces sloping outwardly away from a central longitudinal axis of the connector in the forward longitudinal direction such that pulling rearwardly on the outer housing causes the ramp surfaces to move the resilient fixing members of the polishing fixture outwardly to disengage the projections on the inner housing so that the connector can be removed from the fixture. 
     The spring retainer and the outer housing preferably are structured and arranged such that the spring retainer is inserted into the rear end of the outer housing in the forward longitudinal direction until cooperative retaining elements formed on the spring retainer and the outer housing engage each other to fix the spring retainer in the longitudinal direction. The retaining elements comprise one or more resilient projections formed on one of the spring retainer and the outer housing, and one or more recesses formed in the other of the spring retainer and the outer housing for receiving the resilient projection(s). Preferably, the spring retainer has the projection(s) and the outer housing has one or more openings therethrough so that the spring retainer can be removed from the outer housing by depressing the projection(s) so as to disengage the opening(s), enabling the spring retainer to be pulled out the rear end of the outer housing. 
     If desired, a mounting element that mounts the connector on the panel can also be provided. This can be accomplished in one embodiment by providing the mounting element in the form of an elongate fastener passing transversely through the outer housing and out one side wall thereof for engaging an opening through the panel, and by providing the spring retainer with a recess through which the elongate fastener extends such that the spring retainer may be removed with the fastener installed. However, the spring retainer may also be configured to allow its removal with the fasteners installed. 
     The mounting element preferably has a pair of the elongate fasteners that pass through the outer housing for engaging a pair of holes in the panel. Alternatively or additionally, the mounting element can include a pair of protrusions formed integrally with the outer housing for engaging openings in the panel. The protrusions can be split so that they resiliently snap into the openings in the panel. 
     To facilitate optimization of the concentricity angle of the ferrule, the ferrule holder preferably includes a concentricity alignment feature formed thereon in a predetermined location with respect to a measured concentricity angle of an optical fiber mounted in the ferrule. The inner housing includes a cooperative alignment feature that is engaged by the concentricity alignment feature on the ferrule holder when the ferrule holder is rotated about a central longitudinal axis thereof so as to circumferentially align the alignment features. In this manner, the measured concentricity angle of the optical fiber is located in a predetermined direction with respect to the inner housing. The alignment features preferably comprise a slot formed in one of the ferrule holder and the inner housing and a key formed on the other of the ferrule holder and the inner housing for engaging the slot. Preferably, the alignment features are structured and arranged so that the ferrule holder can be mounted in the inner housing in only one position. Accordingly, the concentricity angle of the ferrule can be optimized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features, and advantages of the invention will become more apparent from the following description of certain preferred embodiments thereof, when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a panel-mounted fiber optic connector in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a perspective view of the connector of FIG. 1 sectioned in half along a vertical longitudinal plane; 
     FIG. 3 is an exploded perspective view of the connector sectioned in half as in FIG. 2; and 
     FIG. 4 is an exploded perspective view of the various components of the connector; 
     FIG. 5 is a top view of spring retainer in accordance with one embodiment of the present invention; and 
     FIG. 6 is a top view of an another embodiment of a spring retainer in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     FIGS. 1 through 4 depict a panel-mounted fiber optic connector  20  in accordance with one preferred embodiment of the invention. The connector  20  generally comprises an outer housing  22 , an inner housing  24 , a ferrule assembly  26 , a main spring  28 , a spring retainer  30 , and fasteners  32  for securing the connector to a panel. The outer housing  22  is a generally rectangular tubular structure defining an interior passage extending longitudinally therethrough. The outer housing can be formed of any suitable material such as plastic. 
     The inner housing  24  and ferrule assembly  26  collectively form a connector insert subassembly that can be assembled as a unit and then inserted (left to right in FIG. 3) into the outer housing  22  through a rear end thereof. The inner housing  24  is a generally tubular structure configured to slide into the outer housing from the rear end until surfaces on the inner housing abut a stop defined by the outer housing, as further described below. The ferrule assembly  26  is configured to slide into the inner housing  24  through a rear end thereof. The ferrule assembly  26  comprises a cylindrical ferrule  34 , a ferrule holder  36 , a ferrule spring  38 , and a crimp body  40 . The ferrule  34  is preferably made of a ceramic material although any able material may be used (e.g. thermoset or thermoplastic) and has a longitudinal bore therethrough for receiving an end of an optical fiber onto which the connector  20  is to be installed. The ferrule holder  36  is generally tubular, a forward portion of the ferrule holder  36  defining a receptacle into which the ferrule  34  is fixedly mounted such that the ferrule  34  projects longitudinally forward out from the front end of the ferrule holder. The ferrule holder  36  has a generally annular flange  42  with a slot  44  machined therein. The ferrules typically have some error in concentricity, and the concentricity of longitudinal bore relative to the outer surface of the ferrule is determined. After the concentricity is determined, the ferrule  20  is inserted into the ferrule holder  36  with the concentricity oriented in a predetermined relationship to the slot  44 . The slot  44  in turn engages a corresponding key (not shown) formed on an inner surface of the inner housing  24  such that the concentricity angle of the ferrule is in a known orientation with respect to the inner housing, and then with respect to the connector since the inner housing  24  is in a predetermined orientation. Thus, connectors made in accordance with the present invention will have their concentricity angles oriented in the same direction, and therefore the insertion loss incurred when the connectors are mated end-to-end can be minimized. 
     The ferrule spring  38  fits over a rear end of the ferrule holder  36 , and the tubular crimp body  40  in turn fits over the rear end of the ferrule holder  36  and the ferrule spring  38  so as to capture the ferrule spring  38  between the flange  42  and a shoulder defined on the inner surface of the crimp body  40 . The ferrule spring  38  urges the ferrule holder  36  and ferrule  34  longitudinally forward relative to the crimp body  40 . 
     The ferrule assembly  26 , comprising the ferrule  34  and ferrule holder  36 , the ferrule spring  38 , and the crimp body  40 , is inserted into the inner housing  24  until the flange  42  on the ferrule holder abuts a stop  46  formed on the inner surface of the inner housing. The ferrule  34  projects longitudinally forward through the stop and out the front end of the inner housing. 
     The insert subassembly comprising the ferrule assembly contained in the inner housing is then inserted into the rear end of the outer housing  22  until projections  48  formed on the inner housing  24  abut corresponding stops  50  formed at the forward end of the outer housing. In this position of the inner housing, a front portion of the inner housing projects longitudinally out from the front end of the outer housing as seen in FIG.  1 . 
     The main spring  28  is then inserted into the rear end of the outer housing  22  and over the tubular rear end of the crimp body  40  until the spring abuts an annular flange  52  formed on the crimp body. The rear end of the crimp body  40  serves as a spring guide for the main spring  28 . Next, the spring retainer  30  is inserted into the rear end of the outer housing  22 . The spring retainer is a generally cup-shaped body whose open forward end receives the rear end of the main spring  28 . The rear end of the spring retainer has a bore  31  therethrough for receiving an optical fiber. The spring retainer has a resilient finger  51  that defines a projection or catch  54  that is depressed inwardly upon inserting the spring retainer into the outer housing. The catch  54  springs outwardly into engagement with an aperture or recess  56  in the outer housing so as to prevent the spring retainer from being pushed out the rear end of the outer housing. Preferably, the main spring  28  is somewhat compressed by the spring retainer  30  so that the main spring continuously urges the crimp body  40  forward, which in turn urges the ferrule holder  36  forward via the ferrule spring  38 . The substantial length of the outer housing  22  and the main spring  28  and ferrule spring  38  enable the ferrule  34  to “float” to a significant extent within the connector. The finger and recess in the preferred embodiment are generally directed upward. This orientation allows a plurality of connectors to be mounted adjacent one another and still allow the access to the fingers or the potential to remove the inner housing to fix, replace, etc., the inner housing or its components without having to remove the outer housing or even adjacent connectors from the board. 
     The outer housing  22  includes mounting elements for mounting the connector on a panel such as a circuit board, backplane, panel, or the like. In the illustrated embodiment, the mounting elements comprise a pair of elongate screws  32  that pass through the outer housing from one side thereof and project out the opposite side of the housing, and a pair of projections  58  integrally formed on the side of the housing. The projections  58  engage holes in the panel (not shown), the threaded ends of the screws  32  pass out the bottom of the housing and into other holes in the panel and are secured with nuts  60  on the opposite side of the panel from the connector, thereby securing the connector to the panel. Preferably, the screws  32  are torque-resistant screws, although any appropriate screws could be used. Other types of mounting elements could be used instead of the screws  32  and projections  58 . For instance, the projections  58  could be omitted, or the screws  32  could be omitted and the projections could be configured to snap into holes in the panel such as by forming the projections as split protrusions or the like. Other types of fasteners could be used also. 
     In the illustrated embodiment, removal of the spring retainer  30  is allowed even though the rear elongate screw is mounted to the panel. This is accomplished by providing the spring retainer  30  with a recess  62  that is engaged by the rear screw  32  and a portion  35  having a reduced width at a forward end of the spring retainer  30  as best shown in FIG.  5 . Screw  32  also has a reduced diameter  33  where the screw engages recess  62 . The spring retainer can be removed by depressing the resilient projection  54  to disengage it from the aperture  56  in the outer housing. Alternatively and as shown in FIG. 6, the spring retainer could be designed without the reduced width portion  35  to prevent the spring retainer from being removed without removing at least the rear screw  32 . 
     Preferably, the inner housing  24  is configured as a standard inner housing so that part commonality is provided between the panel-mounted connectors of the invention and standard non-panel-mounted connectors. While a standard SC-type connector is illustrated, other ferrules and/or connector configurations could be used, e.g., LC, ST®, DC, etc. Additionally, the forward portion of the outer housing  22  is preferably configured as a standard SC outer housing so that the connector  20  is compatible with standard polishing fixtures used for non-panel-mounted SC connectors. More particularly, the forward portion of the outer housing  22  includes openings  64  through opposite side walls thereof through which resilient fixing members of a polishing fixture can extend so as to engage the projections  48  on the inner housing to restrain the inner housing from moving rearward during a polishing operation. The outer housing further includes ramp surfaces  66  proximate the openings  64  through the side walls thereof, the ramp surfaces sloping outwardly away from a central longitudinal axis of the connector in the forward longitudinal direction such that pulling rearwardly on the outer housing  22  causes the ramp surfaces  66  to move the resilient fixing members of the polishing fixture outwardly to disengage the projections  48  on the inner housing so that the connector can be removed from the polishing fixture. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.