Abstract:
Apparatus for connecting an interconnecting cable between first and second printed circuit (PC) boards comprises: a base member disposed on a side of the first PC board for fixedly attaching one end of the interconnecting cable to the first PC board; a first connector attached to the other end of the interconnecting cable; a second connector disposed on a side of the second PC board; and a spring member attached to the base member for supporting the first connector away from the side of the first PC board, the spring member operative to force the first connector against the side of the second PC board to cause slidable engagement of the first and second connectors when one of the first and second PC boards is slid past the other of the first and second PC boards. Apparatus and method of providing optical connection between a first optical array electrically coupled to a first printed circuit (PC) board and a second optical array electrically coupled to a second PC board for providing optical communication between the first and second optical arrays are also disclosed.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to optical communications, in general, and more particularly to apparatus and method of providing an optical connection between printed circuit (PC) boards for optical communication there-between. 
   Greater demands for increased bandwidth are being made on data communication between electrical data processing units or subunits, like printed circuit (PC) boards, for example. Communication rates of tens of gigabits per second are exemplary of such demands. These demands can not be met by traditional metal electrical connections, like those found on mother boards and back plane connections, for example. One solution to meet these demands is to create optical communication channels for board-to-board communication using light coupling between an array of light emitters of one PC board and an array of light detectors of another PC board. 
   A drawback to this solution is that a mechanical light coupling interconnection between parallel PC boards is no simple task. Thus, a simple and automatic interconnection of the light coupling between PC boards is desirable to render optical communication between PC boards a commercially viable reality. The present invention intends to satisfy this desire through suitable interconnection apparatus. 
   SUMMARY 
   In accordance with one aspect of the present invention, apparatus for connecting an interconnecting cable between first and second printed circuit (PC) boards comprises: a base member disposed on a side of the first PC board for fixedly attaching one end of the interconnecting cable to the first PC board; a first connector attached to the other end of the interconnecting cable; a second connector disposed on a side of the second PC board; and a spring member attached to the base member for supporting the first connector away from the side of the first PC board, the spring member operative to force the first connector against the side of the second PC board to cause slidable engagement of the first and second connectors when one of the first and second PC boards is slid past the other of the first and second PC boards. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view illustration of optical fiber interconnection apparatus suitable for embodying the principles of the present invention. 
       FIG. 1A  is a cross-sectional sketch illustrating an exemplary optical interface at one end of an optical fiber cable suitable for use in an embodiment of the present invention. 
       FIG. 1B  is a cross-sectional sketch illustrating an exemplary optical interface at the other end of the optical fiber cable suitable for use in an embodiment of the present invention. 
       FIG. 2  is an illustration of a pivot pin suitable for use in the embodiment of  FIG. 1 . 
       FIG. 3  is a top view illustration of an exemplary arm suitable for use in the embodiment of  FIG. 1 . 
       FIGS. 4A and 4B  are side and top view illustrations, respectively, of a spring mechanism suitable for use in the embodiment of  FIG. 1 . 
       FIGS. 5A ,  5 B and  5 C are top, bottom and end view illustrations, respectively, of a fiber connector suitable for use in the embodiment of  FIG. 1 . 
       FIG. 6  is a side view illustration showing one mode of operation of the embodiment of  FIG. 1 . 
       FIG. 7  is a side view illustration showing another mode of operation of the embodiment of  FIG. 1 . 
       FIGS. 8 and 9  are side and end view illustrations, respectively, of an alternate embodiment of the present invention. 
       FIG. 10  is a side view illustration of an alternate optical interconnection apparatus suitable for embodying the principles of the present invention. 
       FIG. 10A  is a cross-sectional sketch illustrating an exemplary optical interface of optical arrays between two connectors suitable for use in an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a side view illustration of optical fiber cable interconnection apparatus suitable for embodying the principles of the present invention. In the present embodiment, two PC boards  10  and  12  of a data processing system, for example, are disposed in a parallel side-by-side configuration. The PC boards  10  and  12  of the present embodiment may be fixed in place in the parallel configuration through board connectors of a backplane or a motherboard (not shown). Apparatus is provided to support optical communication between an array of light emitters on one board and an array of light detectors on the other board through a cable of optical fibers. This apparatus permits an automatic mechanical interconnect of the cable of optical fibers between PC boards  10  and  12  as one board is slid into its connector with the other board fixed in place as will become more evident from the following description. 
   Referring to  FIG. 1 , a platform or base  14  which may be molded plastic, for example, is fixedly disposed over a side  16  of PC board  10 . One end of a cable of optical fibers  18  is aligned in cross-section with an array of emitters or detectors  20  disposed on side  16  of board  10 . The end of cable  18  is held in alignment with and in proximity to the array  20  by the base  14  as shown by way of example in the cross-sectional sketch of  FIG. 1A . The base  14  includes a pivot structure  22  at a distance from the cable  18 , preferably close to an end  24 . Pivotally coupled to the pivot structure  22  is one end of an arm  26  which is forced away from the base  14  by a spring mechanism  28  attached to both the base  14  and arm  26 . A suitable spring mechanism  28  for the present embodiment is shown in the side and top view sketches of  FIGS. 4A and 4B , respectively. 
   The arm  26  which is exemplified in structure by the top view sketch of  FIG. 3  may be stamped metal or molded plastic, for example. In the present embodiment, a pivot pin, which may be either plastic or metal, is disposed through an aperture  30  in the pivot structure  22  and through co-aligned apertures at the one end of the arm  26  to provide the pivotal coupling therebetween. An example of a pivot pin for use in the present embodiment is shown in  FIG. 2 . In the present embodiment, the pivot pin may be also inserted through a loop  31  in the spring mechanism  28  to provide a fulcrum for the spring  28  as well as retain the spring  28  in position. Once inserted though the corresponding apertures of the pivot structure  22  and arm  26 , and the loop  31  of spring mechanism  28 , the plain end of the pivot pin may be headed to retain it in place. 
   The other end of arm  26  is pivotally coupled to a connector  32  including a female interconnecting structure which is slidably engagable with a male interconnecting structure of a connector  34  which is shown in greater detail in the side view sketches of  FIGS. 6 and 7 . A suitable female connector  32  for use in the embodiment of  FIG. 1  is shown in top, bottom and end views in  FIGS. 5A ,  5 B and  5 C, respectively. Referring to  FIGS. 5A–5C , the female connector  32  includes pivot structures  36  at opposite sides of the top thereof. Each pivot structure  36  includes an aperture  38 . Apertures at other end of the arm  26  are co-aligned with the apertures  38  of the pivot structure  36  and another pivot pin may be inserted through the corresponding apertures of the connector  32  and arm  26  to render the pivotal coupling in the present embodiment. This pivot pin may be headed after insertion to hold it in place. 
   Also, at opposite sides of the bottom of the female connector  32  are wrap-around winged female interconnecting structures  40  which accommodate the slidable engagement and mating with the male interconnecting structure of connector  34  as shown in  FIG. 1 . In addition, the female connector  32  includes an aperture  42  through the body thereof which is aligned over an array of emitters or detectors  44  in the male connector  34  in the mated state. The other end of the cable of optical fibers  18  may be attached to the aperture  42  so that when the female connector  32  is mated with the male connector  34  as shown in  FIG. 1 , the other end of the cable  18  will be aligned in cross-section over the array  44  as shown by way of example in the cross-sectional sketch of  FIG. 1B . In the present embodiment, a ramp like structure  46  is disposed on a side  48  of board  12  and the male connector  34  containing the array  44  is fixedly disposed in the vicinity of the peak of ramp structure  46 . The ramp structure  46  may be stamped metal or molded plastic, for example. Wiring  49  from the array  44  may pass through the connector  34  and ramp section  46  to circuitry on the PC board  12 . 
   Moreover, the length of the cable  18  may be made greater then the distance between boards  10  and  12  so that when connectors  32  and  34  are mated, the cable  18  will flex and bend slightly. Structural features of the combination of components including the base  14 , arm  26 , the pivot structures  22  and  36  and the female connector  32  serve to limit the possible rotation of the arm/connector assembly and maintain the female connector  32  within a few degrees of parallel to the board  10 . Thus, in the fully extended position, very little, if any, force is exerted on the cable  18 . In the present embodiment, the extended position of the arm/connector assembly is controlled in order to provide accurate initial engagement of the connector  32  with the ramp  46  without stubbing into the leading edge of the other board  12  as will become more evident from the following description. Accordingly, the length of cable  18  may be made commensurate with a desired distance that the arm  26  is permitted to rotate or move when unmated. 
     FIG. 6  is a side view illustration of the present embodiment showing a slidable engagement of the female connector  32  of board  10  with the male connector  34  of board  12 . In the illustration of  FIG. 6 , board  12  is connected in place and board  10  is being moved in the direction of arrow  50  in parallel with board  12  for connection. In this state, due to the controlled extension of the arm/connector assembly as described above, female connector  32  makes initial contact with side  48  of board  10  and then, traverses up the ramp structure  46 . The spring mechanism  28  maintains a force on arm  26  to keep the connector  32  pressed against the surface of ramp  46 . Eventually, the female connector  32  will slidably engage the male connector  34  in the vicinity of the peak of the ramp  46  and will be fully engaged with the connector  34  when the board  10  is connected in place as shown by the illustration of  FIG. 1 . Note that when board  10  is connected and the connectors  32  and  34  are fully engaged, the cross-section of the other end of cable  18  will be aligned with the array  44  as shown in  FIG. 1B . Note that board  10  may be withdrawn from its connection and the connectors  32  and  34  disengaged in a reverse process to that of the foregoing. 
     FIG. 7  is a side view illustration of the present embodiment showing a slidable engagement of the female connector  32  of board  10  which is connected in place with the male connector  34  of board  12  which is being moved in the direction of arrow  52  in parallel with board  10  for connection. In this state, due to the controlled extension of the arm/connector assembly as described above, female connector  32  makes initial contact with side  48  of board  12  and then, traverses up the ramp structure  46 . The spring mechanism  28  maintains a force on arm  26  to keep the connector  32  pressed against the surface of ramp  46  from the opposite side. Eventually, the female connector  32  will slidably engage the male connector  34  in the vicinity of the peak of the ramp  46  and will be fully engaged with the connector  34  when the board  12  is connected in place as shown by the illustration of  FIG. 1 . Note that when board  12  is connected and the connectors  32  and  34  are fully engaged, the cross-section of the other end of cable  18  will be aligned with the array  44  as shown in  FIG. 1B . Note that board  12  may be withdrawn from its connection and the connectors  32  and  34  disengaged in a reverse process to that of the foregoing. 
   While the foregoing described embodiment uses a female interconnection structure for connector  32  and a male interconnection structure for connector  34 , it is understood that connector  32  may include a male interconnection structure and connector  34  a female interconnection structure to afford the same slidable engagement therebetween without deviating from the broad principles of the present invention. Alternatively, the interconnection structures for connectors  32  and  34  may be hermaphroditic. 
     FIGS. 8 and 9  are illustrations of side and end views, respectively, of an alternate embodiment of the present invention.  FIGS. 8 and 9  show the alternate embodiment in mated alignment with boards  10  and  12  connected in their parallel configuration. All of the components of the embodiment of  FIG. 1  may remain as described except for the springed and pivoted arm assembly which is being replaced in the alternate embodiment by a hollow plastic tubular spring member  60  which may be formed by molding, for example. The spring member  60  is fixedly attached at one end to the base  14  and the female connector  32  is attached at the other end thereof. One end of the cable  18  is attached to the base  14  through one end of the spring member  60  so that it is aligned in cross-section with the array  20  on the board  10  as shown in  FIG. 1A  and the other end of cable  18  is attached to the connector  32  through the other end of the spring member  60  so that it may be aligned in cross-section with the array  44  at the male connector  34  when the connectors are engaged as shown in  FIG. 1B . Also, the connectors  32  and  34  are slidably engagable and disengagable in a similar manner as described for the embodiment of  FIG. 1 . 
   The spring member  60  provides support for and controls the extension of female connector  32  in an unmated state. It also provides a spring force for the female connector  32  when engaged with side  48  of board  12  and alignment of connector  32  for slidable engagement with connector  34 . Accordingly, when one board is connected in place and the other board is slid in parallel configuration with the one board into its connector, the female connector  32  is forced against the side  48  and ramp  46  by a compression of the spring member  60  and slidably engages male connector  34  with movement of the sliding board. As with the embodiment of  FIG. 1 , when the sliding board is connected, the connectors  32  and  34  will be fully engaged. Thus, the alternate embodiment of  FIGS. 8 and 9  allows either board  10  or  12  to be inserted into its connector with an automatic mechanical slidable engagement of the connectors  32  and  34 . Once both boards  10  and  12  are connected in parallel configuration, the cable of optical fibers will be automatically aligned with the arrays  20  and  44  and optical communication between boards may commence. 
   Either of the foregoing described embodiments may include a low-force plastic detent, which may be formed by molding, to provide coarse alignment in the axis in the direction of slide. Also, the cable fibers and/or arrays may be attached to the slidable male and female connectors using several techniques comprising: (a) potting with an epoxy compound, (b) over-molding the fibers into an array that may be laser trimmed to effect and even mating cross-section surface, (c) looming individual fibers of the cable into an array that may be attached with an epoxy compound to provide retention and an even mating surface, (d) looming individual fibers of the cable into an array that uses “hose barb” features to retain the individual fibers, and may be laser trimmed to provide retention and an even mating surface, and (e) molding, potting, sliding or snapping an entire array assembly of emitters or detectors, including a small printed wiring board (PWB), into either connector, for example. 
     FIG. 10  is a side view illustration of yet another embodiment of the present invention in which the optical fiber cable  18  is eliminated and the optical array  20  is moved from the PC board  10  as shown in  FIG. 1  to the connector  32  so that when the connectors  32  and  34  are mated, the optical arrays  20  and  44  will be in close proximity and aligned with one another. Referring to  FIG. 10 , the optical array  20  is disposed in the connector  32  and electrically connected to circuitry on PC board  10  through a wiring cable  70  which is held in place at the PC board end by an aperture in the base  14 , for example. The cross-sectional sketch of  FIG. 10A  illustrates an exemplary optical interface between connectors  32  and  34 . 
   Referring to  FIG. 10A , as described herein above, the aperture  42  of connector  32  is positioned to be aligned with the array  44  when the connectors  32  and  34  are mated (see  FIG. 1B ). In the present embodiment, instead of the optical fiber cable  18 , the optical array  20  itself is disposed at the aperture  42  of connector  32  and oriented to face the optical array  44 . Accordingly, when the connectors  32  and  34  are mated as shown in  FIG. 10A , the arrays  20  and  44  will be aligned with one another. Wiring cables  70  and  49  will connect the elements of their respective optical arrays  20  and  44  to the respective PC boards  10  and  12 . The array  20  and wiring cable  70  may be affixed to the connector  32  at the aperture  42  by an adhesive material or potting compound  72 , for example. 
   While this alternate embodiment has been described in connection with the pivoted arm interconnection apparatus of  FIG. 1 , it is understood that it may be applied just as well to the tubular spring member apparatus of  FIGS. 8 and 9  by moving the array  20  to the connector  32  and replacing the optical fiber cable  18  with the wiring cable  70  as shown in  FIG. 10A , for example. 
   While the present invention has been described herein above in connection with a plurality of embodiments, it is understood that this presentation was made entirely by way of example. Accordingly, the present invention should not be limited to any particular embodiment, but rather construed in breadth and broad scope in accordance with the recitation of the claims appended hereto.