Abstract:
An adapter with novel alignment features engages alignment features on a plug, providing general alignment of the ferrule holders and ferrules in the plug. After the plug engages the adapter, the ferrule holders engage a second set of alignment features in the adapter to provide fine alignment for the ferrules.

Description:
REFERENCE TO RELATED CASE 
       [0001]    This application claims priority under 35 U.S.C. § 119 (e) to provisional application no. 61/789,499 filed on Mar. 15, 2013, the contents of which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    There is a need for fiber optic connectors with fiber optic ferrules that are ganged together with a tight pitch between those fiber optic ferrules. Such a design allows for many fiber optic ferrules to be connected simultaneously while occupying less space. In addition, it allows the fiber optic ferrules to be organized in a prearranged routing of the optical fibers so that the complexity of fiber optic connector routing is reduced for the user. Typically, these ganged fiber optic ferrules are mounted into a single housing and the housings are then mated to one another. The alignment between a pair of ferrules to be mated is complex and requires tight tolerances because there is a tolerance stack-up that includes the true position of the fiber optic ferrule relative to the housing. By requiring a tight tolerance of the housing relative to the fiber optic ferrule, the designs are expensive to design, maintain, and to scale to various fiber optic ferrule counts. It is also difficult to scale to very large arrays of fiber optic ferrules within one housing due to the true position tolerance required for every fiber optic ferrule to the housings and also the larger distances from the fiber optic ferrules to the housings. 
         [0003]    An alternative way to align the ferrules to each other is to align the ferrule holders to one another through features in the adapter. Rather than using the sides of the ferrule holder to align the ferrule holder to the adapter, top and bottom keys on the ferrule holder align the ferrule holder relative to the adapter in the x-direction. The orientation of the ferrule holder is controlled by the width difference between the top and the bottom key. The height of the ferrule holder aligns the ferrule holder in the y direction. A plug is used to assemble a plurality of the ferrule holders together. The ferrule holders protrude through the plug so the ferrule holder features can be aligned in the adapter after the plug engages the adapter and aligns the ferrule holders with their own structures. The alignment in the X and Y directions between the ferrule holder and the adapter are maintained within 100 microns, preferably within 50 microns. The ferrule holders are relatively loosely held within the plug so as to not over constrain the ferrule holders in the adapter (greater than 100 microns). The grooves within the adapter that aligns the ferrule holders is one continuous feature for both sides of the adapter and the mating ferrule holders. By making the groove one continuous feature for both sides, the alignment the mating ferrule holders is guaranteed. The size of the groove is critical but the true position of the alignment feature relative to the adapter-to-plug alignment feature is not critical. By using this alignment mechanism, large arrays of ferrule holders can be manufactured. Only the size of the alignment mechanism in the ferrule holder and the size of the alignment mechanism in the adapter must be maintained. The true position tolerances are significantly reduced. 
         [0004]    Thus, an adapter and adapter assembly with novel alignment features is provided to engage with alignment features on a plug, which is turn assists in aligning the ferrule holders with alignment grooves in the adapter. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is directed to an adapter for aligning fiber optic ferrules inserted from opposing sides that includes a main body having an opening extending between a first side and a second side, the first side and the second side separated by a central portion, at least one groove in a top surface and a bottom surface of the first side and the second side, and a plurality of grooves disposed in a top surface and the bottom surface of the central portion, each of the plurality of grooves extending through the central portion from the first side to the second side. 
         [0006]    According to another aspect of the present invention, adapter assembly for aligning one plurality of optical ferrules to another plurality of optical ferrules includes an adapter having an opening extending between a first side and a second side, the adapter having a plurality of grooves in the opening and extending in a direction from the first side to the second side, a plurality of ferrule holders, each of the plurality of ferrule holders having a central opening extending from a first end to a second end to resiliently retain a fiber optic ferrule therein, each of the plurality of ferrule holders having an opening in first end and in communication with the central opening, the second end opposite the first end and through which optical fibers extend, each of the plurality of ferrule holders having a projection on opposite outside surfaces to engage a corresponding groove in the adapter, and a plug having an outside surface and an inside surface, the inside surface defining an opening through the plug to hold a plurality of ferrule holders therein adjacent one another, the plug having grooves in the inside surface to engage the projections from the plurality of ferrule holders to align and orient the ferrule holders in the plug. 
         [0007]    In yet another aspect, a ferrule holder includes a main body having a central opening to resiliently retain a fiber optic ferrule therein, a central opening in the main body and extending from a first end to a second end to resiliently retain a fiber optic ferrule therein, the first end having an opening therein and in communication with the central opening, the second end opposite the first end and through which optical fibers extend, and a projection on opposite outside surfaces of the main body to engage a corresponding groove in an adapter. 
         [0008]    The present invention is also directed to a fiber optic connector that includes a plurality of ferrule holders, each of the plurality of ferrule holders having a central opening extending from a first end to a second end to resiliently retain a fiber optic ferrule therein, the ferrule holder having an opening in first end in communication with the central opening, the second end opposite the first end and through which optical fibers extend, each of the plurality of ferrule holders having a projection on opposite outside surfaces to engage a corresponding groove in the adapter, and a plug having an outside surface and an inside surface, the inside surface defining an opening through the plug to hold a plurality of ferrule holders therein adjacent one another, the plug having grooves in the inside surface to engage the projections from the plurality of ferrule holders to align and orient the ferrule holders in the plug 
         [0009]    Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
         [0010]    It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and, together with the description, serve to explain the principles and operations of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view of one embodiment of an adapter assembly according to the present invention; 
           [0012]      FIG. 2  is an exploded view of the adapter assembly of  FIG. 1 ; 
           [0013]      FIG. 3  is a perspective view of a cut-away view of the adapter of  FIG. 1 ; 
           [0014]      FIG. 4  is a front elevational view of the adapter of  FIG. 1 .; 
           [0015]      FIG. 5A  is a top perspective view of one embodiment of a ferrule holder and ferrule that can be used in the adapter assembly of  FIG. 1 ; 
           [0016]      FIG. 5B  is a bottom perspective view of the ferrule holder and ferrule of  FIG. 5   a;    
           [0017]      FIG. 5C  is a front view of the ferrule holder and ferrule of  FIG. 5   a;    
           [0018]      FIG. 6A  is a top perspective view of a plug and ferrule holders according to the present invention; 
           [0019]      FIG. 6B  is a bottom perspective view of the plug and ferrule holders of  FIG. 6A ; 
           [0020]      FIG. 6C  is a front elevational view of the plug and ferrule holders of  FIG. 6A ; 
           [0021]      FIG. 7A  is a partial cross sectional view of a portion of a ferrule holder of  FIG. 5 ; 
           [0022]      FIG. 7B  is a partial cross sectional view of a portion of the center portion of the adapter; 
           [0023]      FIG. 8  is a cross sectional view of the adapter assembly in the center of the adapter assembly; and 
           [0024]      FIG. 9  is a cross sectional view of the adapter assembly through a ferrule holder and ferrule. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Reference will now be made in detail to the present preferred embodiment(s) of the invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
         [0026]    Referring to  FIGS. 1 and 2 , one embodiment of an adapter assembly  10  is illustrated. The adapter assembly  10  includes an adapter  100 , a plug  200  and a ferrule holder  300 . The adapter assembly  10  is used to align ferrules  12  to other ferrules in a tightly controlled manner and in a tighter space than has been possible before. The ferrules  12  are typically multi-fiber ferrules, particularly MT type ferrules, but the present invention may include other types of ferrules. The ferrules  12  are disposed within the ferrule holder  300  and have optical fibers  14  secured therein, which may be loose optical fibers, ribbonized optical fibers, or optical fibers in any other configuration. The ferrules  12  are resiliently held in the ferrule holders  300  using a spring push  16  that engages a spring  18 . The spring  18  then presses on a pin keeper  20 , as is known in the art, to bias the ferrules  12  forward in the ferrule holder  300 . As is described in more detail below, the ferrules  12  are held somewhat loosely within the ferrule holder  300  so that they can move relative to the ferrule holder  300  to align with other ferrules  12  that are inserted in the adapter  100  from the other side. Similarly, the ferrule holders  300  are inserted into the plug  200  and they are also loosely held in the plug  200 . That is, there is typically more than 100 microns of movement in the x and y directions (See  FIG. 4 .) available to the ferrule holder  300  in the plug  200 , as explained in more detail below. 
         [0027]    As illustrated in  FIGS. 5A-C , the ferrule holder  300  has a main body  302  with a central opening  304  that extends from a first end  306  to a second end  308  to house the fiber optic ferrules  12 . The first end  306  has an opening  310  therein to allow access to the ferrule  12 . The ferrule  12  may or may not exit the main body  302 . That is, the ferrule  12  may extend beyond the main body  302  as shown in the figures or it may be flush with the first end  306 . second end  308  allows for the optical fibers  14  (shown in  FIG. 5A and 5B  to have a boot and a covering) to exit the ferrule holder  300 . The ferrule holder  300  has a top surface  312  and a bottom surface  314 , with a cantilevered latch  316  to engage the plug  200 . The top surface  312  has a projection  320  and the bottom surface  314  has a projection  322 . The projections  320 , 322  are preferably elongated and have a chamfered front end. The projections  320 , 322  are used to engage grooves in the plug  200  and the adapter  100  to position the ferrule holders  300  with precision in the adapter  100 . The projection  320  has a width that is different that the width of projection  322  so as to act as a key in inserting the ferrule holder  300  in the plug  200 . While the projection  320  is wider than projection  322 , it could be opposite in that projection  320  is more narrow than projection  322 . The projections  320 , 322  are preferably on the top and the bottom surfaces  312 , 314  of the ferrule holder  300  to allow, as illustrated below, more ferrule holders to be inserted into the adapter  100  and the plug  200 . The projections  320 , 322  are used to position the ferrules  12  in the adapter in the x and y directions, eliminating the need for side walls to position the ferrule holders  300  and the ferrules  12 . 
         [0028]    The plug  200  will now be described relative to  FIGS. 6A-6C . The plug  200  has an outside surface  202  and an inside surface  204 . The inside surface  204  defines an opening  206  therethrough to allow the ferrule holders  300  to be inserted therein. The inside surface  204  has a plurality of grooves  208  on a top side  210  and a corresponding plurality of grooves  212  on the bottom side  214 . The grooves  208  and  212  are dimensioned to accept the projections  320 , 322  from the ferrule holders  300 . It should be noted that the ferrule holders  300  are adjacent to one another, that is side-by-side without any material from the plug  200  therebetween. Applicant means that by using the term adjacent herein, there is no structure that comes between the neighboring ferrule holders  300 . 
         [0029]    The outside surface  202  also has a projection  220  on the top of the plug  200 , seen in  FIG. 6A , and also a projection  222  on the bottom of the plug  200 , seen in  FIG. 6B . Again, as with the projections  320 , 322 , projection  220  has a width that is different that the width of projection  222  so as to act as a key in inserting the plug  200  into the adapter  100 . While the projection  220  is narrower than projection  222 , it could be opposite in that projection  220  is wider than projection  222 . 
         [0030]    The plug  200  also has two cantilevered latches  230  on the sides to engage corresponding structure on the adapter  100 . There are also latch receptacles  232  on the top side of the plug  200  to engage the latches  316  of the ferrule holders  300 . 
         [0031]    As noted above, the grooves  208  and  212  in plug  200  are dimensioned to accept the projections  320 , 322  from the ferrule holders  300 . There is sufficient movement in the ferrule holders  300  relative to the plug  200  that when the plug  200  and ferrule holders  300  as assembled is inserted into the adapter  100 , that the ferrule holders  300  can move to allow the projections  320 , 322  from the ferrule holders  300  to engage corresponding grooves in the adapter  100  as described below in more detail. 
         [0032]    Returning to  FIGS. 3 and 4 , the adapter  100  is illustrated in more detail. The adapter  100  has a main body  102  with an opening  104  extending between a first side  106  and a second side  108 . The first side  106  and a second side  108  are separated by a central portion  110 . The first side  106  has a top surface  112  and a bottom surface  114 . The top surface  112  has a groove  116  and the bottom surface  114  has a groove  118 . The grooves  116 , 118  correspond to the projections  220 , 222  from the plug  200 . The location of the wider groove in the adapter  100  will correspond with the wider projection on the plug  200 . 
         [0033]    The adapter has the center portion  110 . Center portion  110  preferably has a wall  130  that extends across the opening  104  in the adapter  100  and divides the center portion  110  in half. The center portion  110  also has a raised bottom portion  132  and a dropped top portion  134  that narrows the opening  104  in the center portion  110 . The wall  130  preferably extends from the raised bottom portion  132  and a dropped top portion  134  or it may be excluded completely if there is no EMI concerns with the adapter  100 . The wall  130  has a plurality of openings  136  that are sized to allow the ferrules  12  to pass therethrough to engage a corresponding ferrule  12 . As noted above, if the ferrules  12  only extend to the end of the ferrule holder  330 , then the openings  136  should be sized to allow the ferrule holders to also extend therethrough. The adapter  100  may also have an elastomeric gasket  150  that encircles an external surface of the adapter  100  to provide EMI shielding. 
         [0034]    The raised bottom portion  132  and a dropped top portion  134  also have a plurality of grooves  140 ,  142 , respectively, that extend completely across the central portion  110 . The grooves  140 ,  142  are like those in the plug  200 , in that they are to engage the projections  320 , 322  from the ferrule holders  300 . The grooves  140 , 142  preferably extend completely across the center portion  110  as they are formed with the same insert in the mold. Therefore, the grooves  140 , 142  are sure to align the ferrule holders  300  on each side of the adapter  100  as they are inserted into the adapter  100 . 
         [0035]    As the plug  200  with the ferrule holders  300  positioned therein are inserted into the adapter  100 , the projections  220 , 222  from the plug  200  engage the grooves  116 , 118  on the top surface  112  and the bottom surface  114  to roughly align the ferrule holders  300  with the center portion  110  and the plurality of grooves  140  in particular. Then, as the plug  200  is inserted farther into the adapter  100 , the projections  320 , 322  from the ferrule holders  300  engage plurality of grooves  140 ,  142  to align the ferrule holders  300  with the adapter and the openings  136  in the wall  130 . When a plug  200  is inserted on the second side, the ferrules in the ferrule holders on the other side will be in alignment with the first side. 
         [0036]    The position of the ferrule holders  300  on the first side  106  of the adapter relative to the ferrule holders  300  on the second side  108  is what allows the optical ferrules to be aligned with one another. There is no need, as discussed above, to worry about the stacking of tolerances as in the prior art. The positioning of the projections  320 , 322  on the ferrule holders  300  relative to the plurality of grooves  140 ,  142  is important. With reference to  FIGS. 7A and 7B , the projections  320 , 322  are used to control the x and y locations of the ferrule holders  300 . The surfaces  350  of the projections  320 , 322  ( FIG. 7A ) align with the surfaces  150  in the adapter ( FIG. 7B ) to control the x direction of the ferrule holder  300  relative to the adapter  100 . The surfaces  352  of the ferrule holder  300  align with the surfaces  352  of the raised bottom portion  132  and the dropped top portion  134  of the center portion  110  to control the y direction of the ferrule holder  300  relative to the adapter  100 . The surfaces of the projections  320 , 322  could also align in the y direction, given that they are parallel to the surfaces  352 . 
         [0037]    A cross section of the adapter assembly  10  is illustrated in  FIG. 8  through the center of the adapter assembly. This illustrates the projections  220 , 200  in the openings  116 , 118  of the adapter  100 .  FIG. 9  is a cross sectional view of the adapter assembly  10  through a ferrule holder and ferrule illustrating the engagement of the projections  320 , 322  in the openings  140 ,  142 . 
         [0038]    It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.