Patent Publication Number: US-2005135753-A1

Title: Fibre-optic plug-in connector system

Description:
TECHNICAL FIELD  
      The present invention relates to the field of fiber-optic connection technology. It concerns a fiber-optic plug-in connector system according to the the preamble of claim  1 .  
      Such a system is known for example from the printed document EP-A2-0 430 107 (FIG. 27 and associated text) or EP-A2-1 168 020.  
     PRIOR ART  
      In the technology of fiber-optic signal transmission, cables in which a plurality of, for example, 12 individual parallel fibers are combined in a cable (known as a ribbon cable) have long been in use. For cables of this type there are special plug-in connector systems, in which all the fibers of the cable are simultaneously connected to one another by a plug-in connector in a predetermined, invariable arrangement. Examples of plug-in connector systems of this type are disclosed in U.S Pat. No. 5,214,730 or in U.S. Pat. No. 6,352,372. The last-mentioned document in particular makes it clear that large-scale integration plug-in connector systems with an extremely high connecting density can be realized in this way.  
      However, on the other hand there is the desire to connect the individual fibers of such multi-fiber cables to one another or to other fiber-optic single-fiber or multi-fiber cables according to requirements and in a largely freely determinable arrangement. In principle, this is possible using standardized plug-in connector systems with individual plug-in connectors if the fibers of the multi-fiber cable are correspondingly separated at the end of the cable and each individual one is provided with a separate plug-in connector. In the case of a ribbon cable with 12 individual fibers, at the end of the cable there are then for example 12 individual plug-in connectors, which have to be further connected in a plug-in connector system.  
      In the document cited at the beginning, EP-A2-1 168 020, there is already a description of a plug-in connector system in which a number of individual plug-in connections can be produced independently of one another for multi-fiber cables within a common adapter. The adapter comprises a frame into which a plurality of individual adapter housings of a multi-fiber connector system can be snap-fitted next to one another. However, the combination of a number of individual standardized plug-in connector systems to form an overall system results in an overall system with considerable dimensions, which runs counter to the efforts constantly being made to reduce the size of communication systems.  
      This also applies to the plug-in connector system shown in FIG. 27 of EP-A2-0 430 107, in which a plurality of slots are arranged next to one another in a one-part adapter housing for the separate connection to standardized plug-in connectors which are provided with a relatively large housing. With a plug-in connector system for separately connecting the fibers of a multi-fiber cable comprising 12 fibers, this produces an arrangement which takes up considerable space and therefore cannot be used in practice for this purpose. Disadvantages are also brought about by the locking system accommodated in the adapter housing, which leads to a significant increase in the overall height.  
      In an earlier patent application of the applicant (WO-A1-01/59499), multiple plug-in connector systems in which very narrow individual plug-in connector inserts are combined in a common housing to form a multiple plug-in connector have already been proposed for use in backplane connections. That application does not envisage freely determinable plug-in connection between individual plug-in connector inserts.  
     SUMMARY OF THE INVENTION  
      It is therefore the object of the invention to provide a fiber-optic plug-in connector system which is distinguished by an extremely compact arrangement and in particular a low overall height, and which makes it possible for a multiplicity of individual fibers to be connected according to choice in an extremely small space while at the same time being easy to handle.  
      The object is achieved by the features of claim  1  in their entirety. The essence of the invention is to achieve a low overall height and at the same time a high connector density by a multi-part adapter housing in which the guiding sleeves necessary for the plug-in connection are held directly between the housing parts.  
      The plug-in connector system is particularly simple and space-saving if, according to a preferred refinement of the invention, the adapter housing is made up of a flat, plate-shaped upper part and a flat, plate-shaped lower part.  
      The correct assembly of the multipart adapter housing is facilitated by guiding means being provided on the upper part and/or the lower part for aligning the two parts with each other, the guiding means preferably comprising a number of guiding pins which are arranged in a distributed manner, are attached in one of the parts and enter into a corresponding bore in the other part.  
      Assembly is further simplified and improved by connecting means which comprise screw couplings in particular being provided for releasably connecting the upper part and the lower part. This allows the system to be easily dismantled again if need be for maintenance or repair purposes.  
      According to another preferred refinement of the invention, respectively provided in the upper part and the lower part is a central web, which runs transversely in relation to the plugging direction and has a plurality of half-cylindrical depressions for receiving the guiding sleeves, arranged one behind the other in the longitudinal direction of the central web. Also respectively provided in the upper part and the lower part, in front of and behind the central web in the plugging direction, are guiding rails, which run between the guiding sleeves in the plugging direction and define for each of the guiding sleeves an associated insertion channel for a plug-in connector.  
      Possibilities for flexible use of the plug-in connector system are achieved by means for fastening and/or aligning the adapter housing being provided on the adapter housing.  
      An optimal combination of good operating suitability and a high connection density is obtained in particular if the spacing of the guiding sleeves arranged directly next to one another, measured from sleeve axis to sleeve axis, is approximately twice the inside diameter of the guiding sleeves. It is also of advantage in this connection if the ferrules used in the plug-in connectors have an outside diameter of 1.25 mm.  
      Also essential for the compact construction of the plug-in connector system is the configuration of the individual plug-in connectors. A preferred refinement of the invention is characterized in that the plug-in connectors respectively have a holder, preferably consisting of a plastic, in the form of a rectangular frame, which is elongate in the plugging direction, encloses an interior space and in the front side of which an opening for the ferrule and in the rear side of which a through-bore for leading through a fiber-optic cable are provided, in that a spring element, in particular in the form of a spiral spring, is mounted in the interior space of the holder for the sprung-mounting of the ferrule, and in that the opening for the ferrule is formed such that it is open toward the side to facilitate assembly.  
      To provide the possibility of adjustment of the optical fiber in the plug-in connector, the ferrule is preferably inserted in an inner part, preferably consisting of metal, arranged in the interior space of the holder, the inner part has a guiding sleeve for guiding the spring element, and means which permit an adjustment of the inner part into different angular positions by rotation about its longitudinal axis are provided on the inner part, the adjusting means comprising in particular an adjusting portion with a square cross section, which adjoins the guiding sleeve in the front region of the inner part and has a receiving bore for receiving the ferrule, and on which the spring element is supported by its front end.  
      The securing of the plug-in connections is preferably made possible by a side wall on the holders respectively having a resilient portion with a latching element arranged on it, and by latching openings into which the plug-in connectors engage with their latching elements on insertion in the adapter housing being provided in the adapter housing.  
      To facilitate use of the plug-in connector system, it may be of advantage if the guiding sleeves in the adapter are combined into a number of groups, respectively comprising a number of guiding sleeves. With a total of 12 individual plug-in connections, it is of advantage if two groups of six guiding sleeves each are provided in the adapter.  
      Further embodiments emerge from the dependent claims. 
    
    
     BRIEF EXPLANATION OF THE FIGURES  
      The invention is to be explained in more detail below on the basis of exemplary embodiments in conjunction with the drawing, in which  
       FIG. 1  shows in a perspective side view a fiber-optic plug-in connector system according to a preferred exemplary embodiment of the invention for the individual connection of a total of 12 fibers in two groups of 6 fibers each;  
       FIG. 2  shows the adapter of the plug-in connector system from  FIG. 1  in an exploded representation;  
       FIG. 3  shows the adapter in the representation according to  FIG. 2  with the associated plug-in connectors in the partially inserted state;  
       FIG. 4  shows an individual plug-in connector from  FIG. 3  in an exploded representation; and  
       FIG. 5  shows the adapter from  FIG. 1  in the view from the front and in the plan view from above. 
    
    
     WAYS OF IMPLEMENTING THE INVENTION  
      In  FIG. 1 , a fiber-optic plug-in connector system according to a preferred exemplary embodiment of the invention is represented in a perspective side view. The fiber-optic plug-in connector system  10  comprises an adapter  11 , which has a rectangular, flat adapter housing  12  comprising an upper part  17  and a lower part  18 . Respectively arranged on the opposite longitudinal sides of the adapter  11  are two rows of insertion openings  16  lying directly next to one another (see also  FIG. 5 , upper part-figure). In the example represented, there are in each case 6 insertion openings 16 per row, that is a total of 12 insertion openings  16 . For better identification and differentiation of the individual insertion openings  16 , associated numbers 1 . . . 12 have been applied to the upper side of the adapter housing  12 . Each of the insertion openings  16  is assigned an insertion channel ( 47  in  FIG. 2 ), running inside the adapter housing  12 . Every two insertion openings  16  and insertion channels  47  lying directly opposite one another respectively form a pair, which can be used for connecting two optical fibers. For this purpose, the optical fibers are respectively provided at their ends. with a plug-in connector  13  made to match the adapter  11 . With the adapter represented in  FIG. 1 , a maximum of 12 pairs of optical fibers can be connected to one another according to choice, for which purpose a total of at most 24 plug-in connectors  13  shown in  FIG. 1  are required (23 plug-in connectors are shown in the inserted state in  FIG. 1 , 1 plug-in connector at position  1  is shown pulled out).  
      The two parts  17  and  18  of the adapter housing are releasably connected to each other by a number of screw couplings  19 . The screw couplings  19  preferably each comprise a screw ( 19   a  in  FIG. 2 ) and a nut ( 19   b  in  FIG. 2 ). Screw heads and nuts are countersunk on the adapter housing  12  in corresponding screw holes ( 22  in  FIG. 2 ). In order that the adapter  11  can be fastened on an underlying surface (rear wall, printed circuit board or the like), a fastening hole  20  passing through the adapter housing  12  is provided in the middle. At the same time, the adapter housing  12  has on its transverse sides semicircular recesses, which can be used for positioning and/or fastening.  
      The internal construction of the adapter  11  is reproduced in the exploded representation of  FIG. 2 . Central elements of the adapter  11  are a plurality of cylindrical guiding sleeves  45 , of which there is one per plug-in connection, that is a total of 12. The guiding sleeves  45  receive the ferrules ( 23  in  FIGS. 3, 4 ) of the plug-in connectors  13  in a way known per se and guide them in such a way that the ferrules of the two plug-in connectors involved in the plug-in connection and the ends of the fibers that are located in the central bores of the ferrules butt against one another with the end faces.  
      The mounting of the guiding sleeves  45  takes place directly in the parts  17  and  18  of the adapter housing  12 . For this purpose, in the upper part  17  and the lower part  18  there is respectively formed a central web  44 , which runs in the longitudinal direction and in which there are formed two rows of parallel, half-cylindrical depressions  48 , arranged one behind the other in the longitudinal direction and running in the plugging direction. In the trough-like depressions  48 , which complement one another to form a cylindrical bore when the upper part  17  and the lower part  18  are screwed together, the guiding sleeves  45  are mounted and held with a degree of play. In order that the two parts  17 ,  18  of the adapter housing  12  can be placed one on top of the other with the precision necessary for the mounting of the guiding sleeves  45 , arranged on the upper side of the lower part  18  are two widely spaced-apart guiding pins  42 , which enter into corresponding bores on the underside of the upper part  17  and in this way align the two parts  17 ,  18  with each other.  
      The upper part  17  and the lower part  18  are two flat plates of the same height, which are formed substantially mirror-symmetrically in relation to a central plane. The overall height of the adapter housing  12  is in this case no more than approximately 5 mm. Respectively provided in the upper part  17  and in the lower part  18 , in front of and behind the central web  44  in the plugging direction, in a lower-lying plane, are guiding rails  46 , which run between the guiding sleeves  45  in the plugging direction. Every two guiding rails  46  neighboring a guiding sleeve  45  define an insertion channel  47  for a plug-in connector  13 , associated with the guiding sleeve.  
      The plug-in connectors can be inserted into the insertion channels  47  formed in this way—as represented in  FIG. 3 , their ferrules  23  being received by the associated guiding sleeves  45 . Since each individual one of the 12 plug-in connections on each side of the guiding sleeve  45  has an insertion channel of its own, the 12 plug-in connections can be made completely independently of one another, as indicated by the plug-in connectors  13  depicted in offset arrangement in  FIG. 3 . In order that the plug-in connectors  13  are securely held in the adapter  11  in the inserted state, a latching device is provided for each plug-in connector, comprising according to  FIG. 1 a  resilient latching element  14  in the form of a latching stage on the plug-in connector  13 , with which the plug-in connector  13  engages in a latching opening  15  in the upper part  17  of the adapter housing  12  in the inserted state. For releasing the latching engagement, the latching element  14  can be pressed with a suitable object or implement downward from above through the latching openings  15 , and the plug-in connector  13  at the same time lifted out of the insertion channel  47 .  
      The particularly compact and space-saving construction of the plug-in connector system  10 , and in particular of the adapter  11 , is only possible if the plug-in connectors  13  themselves are restricted to a minimum in their outer dimensions. Used with preference as plug-in connector  13  in the present case is a configuration which has already been used by the applicant in an earlier application (WO-A1-01/59499) in a different context, that is as an insert in a backplane connector. The construction of the plug-in connector  13  is reproduced in an exploded representation in  FIG. 4 .  
      According to  FIG. 3 , an individual plug-in connector  13  comprises the ferrule  23  (material: for example zirconia; diameter: preferably 1.25 mm), an inner part  24  (made of metal), a spring element  28  in the form of a spiral spring, a frame-shaped holder  29  (injection molding made of plastic), a crimping neck  37  (made of metal) and a crimping sleeve  41  (likewise made of metal). It goes without saying that, instead of the spiral spring, some other spring element, for example a rubber tube, may also be used. The holder  29  forms the basic component of the plug-in connector  13  and gives the plug-in connector  13  the necessary mechanical stability. The other components  23 ,  24 ,  28 ,  37  and  41  are accommodated in the holder  29  or attached to the holder  29 . The holder  29  has the form of a rectangular frame which is elongate in the plugging direction and encloses an interior space  33 . In the front wall (front side) of the frame, an opening  30  is provided for the ferrule  23 . In the rear wall (rear side), a through-bore  34  is provided for leading through the fiber-optic cable  32 , and a rectangular receiving space  35  is provided. Arranged on the outer side of the rear wall is a square recess (not visible in  FIG. 3 ).  
      The crimping neck  37  comprises a square holding plate  39 , which is respectively adjoined at the front and rear in the axial direction by a tube stub  38  and  40 . The front tube stub  38  additionally bears a concentric annular bead  43 . When the crimping neck  37  is pressed into the through-bore  34  of the holder  29 , the tube piece  38  engages with its annular bead  43  in the receiving space  35 . At the same time, the holding plate  39  comes to lie in the aforementioned recess in the rear wall and in this way secures the crimping neck  37 , pressed into the holder  29 , against being twisted by a torsional force acting. on the cable  32 . The front tube stub  38 , protruding into the interior space  33  when the crimping neck  37  is pressed in, serves for supporting the spiral spring  28  inserted into the interior space  33 . The rear tube stub  40 , protruding out of the holder  29  to the rear, serves for securing the strain relief of the fiber-optic cable  32  by means of the crimping sleeve  41  pushed over it and subsequently pressed.  
      The ferrule  23 , the inner part  24  and the spiral spring  28  are mounted in the interior space  33  of the holder  29 . The inner part  24  comprises a guiding sleeve  27  for guiding the spiral spring  28  and an adjusting portion  26  with a square cross section. The adjusting portion  26  adjoins the guiding sleeve  27  in the front region of the inner part  24  and has a receiving bore  25  for receiving the ferrule  23 . The spiral spring  28 , pulled over the guiding sleeve  27 , is supported by its front end against the rear side of the adjusting portion  26 . The ferrule  23  is pressed into the receiving bore  25  on the inner part  24  and inserted together with the inner part  24  and the pushed-on spiral spring  28  into the interior space  33  from the open side of the holder. In order that the ferrule  23  can assume its place in the front opening  30  unhindered, this opening  30  is formed such that it is open to the side. The interaction-between the square adjusting portion  26  and the rectangular interior space  33  permits an adjustment of the inner part  24  (or the fiber) into different angular positions by rotation about its longitudinal axis (in 4 steps of 90° each). The spiral spring  28  thereby presses the inner part against the front part of the holder  29 , so that the adjusted position can be held. In order to give the spiral spring  28  an additional lateral hold in the interior space  33 , elongate bounding elements  36  may be formed on the inner side of the longitudinal walls of the holder.  
      However, instead of the rectangular or square configuration with its adjustability in steps of 90°, it is also conceivable for example to provide a hexagonal configuration with an adjustability in steps of 60°. In order that the plug-in connectors  13  can be inserted into the adapter  11  with latching engagement, on each holder  29  the upper-lying side wall respectively has a resilient portion  31 , protruding outward in a slightly V-shaped manner, arranged on which is a latching stage (latching element  14 ), which as already described further above—releasably engages in the associated latching opening  15  on the adapter housing  12  when the plug-in connector  13  is pushed in.  
      The high plug-in connector density that is possible with the solution according to the invention can be seen from the front view in the upper part of  FIG. 5 , showing the height h and the width w of an an individual insertion opening  16  and the spacing d between two neighboring guiding sleeves or insertion openings  16 , measured from sleeve axis to sleeve axis. If ferrules  23  with a diameter of 1.25 mm are used, each plug-in connector  13  or each insertion opening  16  has dimensions (width×height) with a width w of approximately 2.4 mm and a height h of approximately 3.4 mm. The spacing d is then approximately the same size as the width w.  
      For comparison, the corresponding dimensions of known plug-in connectors are given below:  
                                                   Plug-in connector type   Width × height (mm × mm)                          Pres. appl. (1.25 mm ferrule)   2.4 × 3.4           LC connector (1.25 mm ferrule)   4.5 × 9.1           sc connector (2.5 mm ferrule)   7.4 × 9.0           LSH connector (2.5 mm ferrule)   6.7 × 12                       
 
      It is immediately evident from the comparison that, with the plug-in connector system according to the application, a considerably more compact solution is available for complex and flexible connections of optical fibers.  
     LIST OF DESIGNATIONS  
     
         
           10  fiber-optic plug-in connector system  
           11  adapter  
           12  adapter housing  
           13  optical plug-in connector  
           14  latching element (latching stage)  
           15  latching opening  
           16  insertion opening  
           17  upper part  
           18  lower part  
           19  screw coupling  
           19   a  screw  
           19   b  nut  
           20  fastening hole  
           21  recess  
           22  screw hole  
           23  ferrule  
           24  inner part  
           25  receiving bore  
           26  adjusting portion  
           27  guiding sleeve  
           28  spring element or spiral spring  
           29  holder (frame-shaped)  
           30  opening  
           31  resilient portion  
           32  fiber-optic cable  
           33  interior space  
           34  through-bore  
           35  receiving space (rectangular)  
           36  bounding element  
           37  crimping neck  
           38 , 40  tube stub  
           39  holding plate  
           41  crimping sleeve  
           42  guiding pin  
           43  annular bead  
           44  central web  
           45  guiding sleeve  
           46  guiding rail  
           47  insertion channel  
           48  depression (half-cylindrical)  
          d spacing  
          h height  
          w width