Abstract:
The present invention provides a host board system in which transceivers of two sizes (the larger approximately twice the width of the smaller) can be arbitrarily mixed within a given host board design. This is accomplished by specifying an arrangement of electrical connectors, a guide rail design, a set of transceiver features, and a bezel configuration to meet this need as well as the other requirements of optoelectronic transceivers. Typically, two slots and connectors are lined up behind an opening in a bezel that provides transceiver access to two connectors. So that either double-width or single-width transceivers can be used in the same opening, the double-width transceiver is designed to engage with the connectors in the same position as a single-width transceiver. Further, the slots and connectors are spaced evenly so that all of the slots and connectors can accommodate a single-width transceiver and all adjacent slots and connectors can accommodate a double-width transceiver.

Description:
The present invention relates generally to host board systems, and particularly to a host board system configured to receive transceivers of multiple widths. 
   BACKGROUND OF THE INVENTION 
   An optical transceiver is a physical device that connects a host interface (i.e., host board) to a fiber optic network or other communication system. In the present invention, the transceivers are optoelectronic transceivers, which means that data is transmitted to and from the transceivers electrically at one end, and optically at the other end. In systems that use optoelectronic transceivers, it is often desirable to pack as many transceivers as possible on the edge (i.e., back face) of a host board to maximize the communication bandwidth of the systems. Very narrow transceivers that can be packed at a dense pitch are, therefore, desirable. As a result, host boards are often configured to accommodate a series of small form factor (i.e., narrow or single-width) transceivers. 
   Such host boards are only viable, however, if each transceiver connected thereto has a common form factor (i.e., similar width). But there exist a variety of transceiver designs to address different needs. For example, vertical-cavity surface emitting lasers (VCSELs) are often used for very short optical links (i.e., the distance light must travel from a light source to a receiver) of up 500 meters. Simple Fabry-Perot 1310 nm lasers are often used for optical link lengths of up to 20 km in systems designed for 1 Gigabit per second data rates or 2 km in systems designed for 10 Gigabit per second data rates. But for much longer optical links with lengths of up to 80 km at 1 Gb per second data rates and up to 10 to 40 km at 10 Gb per second data rates and where it is desired to combine signals of different wavelengths, transceivers integrating DFB lasers with temperature controllers and avalanche photo diodes (APDs) are often required. 
   The VCSEL and Fabry-Perot laser based transceivers can often be constructed in very narrow widths (i.e., small form factor designs or single-width transceivers), but more complex designs, such as transceivers integrating DFB lasers with temperature controllers and avalanche photo diodes, often require a greater widths (i.e., larger form factor designs) to accommodate the extra circuitry and thermal dissipation considerations. 
   These larger form factor transceivers cannot be used on the above described host boards because each slot available to a transceiver is designed to fit only single-width transceivers. To address this problem, some host boards have been designed to accommodate a fixed number of small form factor transceivers and another fixed number of larger form factor transceivers. This solution is inefficient and inflexible. Host boards designed to accommodate a fixed number of small form factor transceivers and another fixed number of larger form factor transceivers limit users to a certain number of small form factor and another certain number of larger form factor transceivers even though needs can and do change. 
   SUMMARY OF THE INVENTION 
   The present invention is a host board system comprising a host board at least partially positioned within a housing having a set of openings. The host board includes a set of connectors. Each opening in the set of openings is aligned with at least two connectors so that a transceiver inserted through the openings can electrically engage with one or more of the two connectors. Each opening in the set of openings is configured to accept two single-width transceivers or one double-width transceiver. The double-width transceiver may or may not engage with both connectors. 
   In another aspect of the invention, the host board system includes a set of slots. The connectors are mounted on the host board and the slots are routed into the host board. Each slot is configures so that a transceiver can slidingly engage the slot. Further, the set of connectors is positioned with respect to the set of slots such that a single-width transceiver can slidingly engage a connector from any of the slots. Finally, the set of connectors is also positioned with respect to the set of slots so that double-width transceivers slidingly engage adjacent slots and electrically couple with a corresponding connector from the set of connectors. Transceivers of triple width or larger could also be accommodated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional objects and features of the invention will be more readily apparent from the following detailed description and appended claims when taken in conjunction with the drawings, in which: 
       FIG. 1  is a diagram of a host board system of a preferred embodiment of the present invention from a top, perspective view. 
       FIG. 2A  is a diagram of a bezel and bezel-opening inserts consistent with a preferred embodiment of the present invention. 
       FIG. 2B  is a diagram of a bezel-opening insert consistent with a preferred embodiment of the present invention. 
       FIG. 2C  is a diagram of a bezel-opening insert consistent with a preferred embodiment of the present invention. 
       FIG. 2D  is a diagram of a bezel-opening insert consistent with a preferred embodiment of the present invention. 
       FIG. 2E  is a diagram of a bezel-opening insert consistent with a preferred embodiment of the present invention. 
       FIG. 3A  is a diagram of a flange included on transceivers in a manner consistent with a preferred embodiment of the present invention. 
       FIG. 3B  is a diagram of a flange included on transceivers in a manner consistent with a preferred embodiment of the present invention. 
       FIG. 4  is a diagram of a guide rail and latch included on a transceiver in a manner consistent with a preferred embodiment of the present invention. 
       FIG. 5  is a diagram of a number of notches, latches, and guide rails consistent with a preferred embodiment of the present invention. 
       FIG. 6  is a diagram of a flange, guide rail, and latch included on transceiver in a manner consistent with a preferred embodiment of the present invention. 
       FIG. 7  is a diagram of a host board system, with emphasis on connectors included in the host board system, consistent with a preferred embodiment of the present invention. 
       FIG. 8  is a diagram of a host board system, with emphasis on functional and non-functional plugs included in the host board system, consistent with a preferred embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a host board system  2  consistent with a preferred embodiment of the present invention. Included in  FIG. 1  are a host board  10 , a bezel  20 , a series of bezel openings  30 , bezel-opening inserts  40  and  50 , double-width transceivers  60 , single-width transceivers  70 , a series of slots  80 , and a series of connectors  90 . 
   The host board  10  is preferably rectangular in shape and includes a variety of electronic components necessary to process signals originating from one or more transceivers  60 ,  70  electrically engaged with the host board  10 . Aside from the circuitry specifically discussed herein, the contents of the host board are otherwise standard, and not critical to the present invention. 
   Attached to the back edge of the host board  10  is a bezel  20 . The bezel  20  serves to contain electromagnetic emissions (“EMI”) produced by the signals originating from the one or more transceivers  60 ,  70  electrically engaged with the host board  10  or from other circuitry within the enclosure. The bezel  20  also serves to support and guide one or more transceivers  60 ,  70  engaged with the host board  10 . When the host board  10  is fully inserted in a larger signal processing system, the bezel  20  and the larger signal processing system contain EMI emissions in all directions. It is, therefore, the shape of the larger signal processing system that dictates the size and shape of the bezel  20 . But the size and shape of the bezel  20  are not critical to the present invention. 
   The bezel  20  includes bezel openings  30 , which are distributed in series across the bezel  20 . The bezel openings  30  are large enough to accommodate transceivers of a variety of sizes. In the preferred embodiment, however, the largest transceiver is a double-width transceiver  60 , so the bezel openings  30  are “double-width bezel openings.” The specific size of the bezel openings  30  is not critical to the present invention. What is important is the positioning of the bezel openings with respect to the slots  80  and connectors  90 . Specifically, a double-width transceiver  60  or one or two single-width transceivers  70  must be able to electrically engage a corresponding connector  90  when inserted into any of the bezel openings  30 . This aspect of the present invention allows users of the invention to use varying combinations of single-width transceivers  70  and double-width transceivers  60  with the same host board system  2 , without having to modify the host board system  2 . Thus, the host board system  2  may accommodate a set of densely packed single-width transceivers  70  (i.e., two inserted into each opening  30 ) or half as many double-width transceivers  60  (i.e., one double-width transceiver  60  per opening  30 ) or any other combination. Further, not every opening  30  need be used or completely filled with transceivers. Unused openings may be closed with an EMI blocking insert, and partially used openings (e.g., occupied by only one single-width transceiver  70 ) may have their unused portion covered by a smaller EMI blocking insert. 
   As illustrated in  FIG. 1 , the bezel openings  30  are evenly spaced. This spacing reflects the spacing of corresponding slots  80  and connectors  90 . More specifically, the amount of space between each of the slots  80  and connectors  90  is the same. In alternate embodiments, the slots  80  and connectors  90  are grouped such that a greater amount of space separates the groups of slots  80  and connectors  90  than the slots  80  and connectors  90  of each group. The key is that the slots  80  and connectors  90  corresponding to a given bezel opening  30  are spaced so that a group of slots  80  and connectors  90  can accommodate either one double-width transceiver  60 , two single-width transceivers  70 , or one single-width transceiver  70 . 
   Before one or more transceivers  60 ,  70  are inserted into the bezel openings  30 , bezel-opening inserts are preferably “snapped” into the bezel openings  30 . Preferred embodiments of the present invention include four types of bezel opening inserts.  FIG. 2A  illustrates a first type of bezel-opening insert  40 , a second type of bezel-opening insert  50 , a third type of bezel-opening insert  52 , and a fourth type of bezel-opening insert  54  inserted into four bezel openings  30  of a bezel  20 . In the preferred embodiments, each of the bezel-opening inserts is made of metal, or metal impregnated or metal coated plastic, so as to block electromagnetic radiation originating from inside the system  2 . Thus, the bezel-opening inserts act as EMI shields. 
   The first type of bezel-opening insert  40 , which is separately illustrated in  FIG. 2B , is designed to accommodate one double-width transceiver  60 . This first type of bezel-opening insert  40  serves to reduce the size of the bezel opening  30  so that a double-width transceiver forms a seal with the bezel-opening insert  40  when inserted through a bezel opening  30  and electrically engaged with a connector  90 . Like the other types of bezel-opening inserts, this first type of bezel-opening insert  40  snaps into place, forming a seal with the bezel  20 . 
   The second type of bezel-opening insert  50 , which is separately illustrated in  FIG. 2C , is designed to simultaneously accommodate two single-width transceivers  70 . That is, the second type of bezel-opening insert  50  permits two single-width transceivers  70  to engage a slot  80  and connector  90 . This type of bezel-opening insert  50  accommodates two side-by-side single-width transceivers  70 . The openings in this insert  50  are essentially sized and positioned the same as the opening in the first type of bezel-opening insert  40 , except that a divider is included to separate the two single-width transceivers  70 . This second type of bezel opening  50  serves to reduce the size of the bezel opening  30  to two smaller openings so that each single-width transceiver  70  forms a seal with the bezel-opening insert  50  when inserted through a bezel opening  30  and electrically engaged with a connector  90 . 
   The third type of bezel-opening insert  52 , which is separately illustrated in  FIG. 2D , is designed to accommodate one single-width transceiver  70 . Importantly, the opening in this third type of bezel opening  52  insert is not centered. Rather, the opening is offset so that it is in the same position as one of the openings in the second type of bezel-opening insert  50 . 
   This means that single-width transceivers  70  consistent with a preferred embodiment of the present invention may be used with either type of bezel-opening insert  50 ,  52 . This third type of bezel opening  52  serves to reduce the size of the bezel opening  30  to one smaller opening so that a single-width transceiver  70  forms a seal with the bezel-opening insert  52  when inserted through a bezel opening  30  and electrically engaged with a connector  90 . 
   Finally, the fourth type of bezel-opening insert  54 , which is separately illustrated in  FIG. 2E , is not designed to accommodate any transceivers. The purpose of the fourth type of bezel-opening insert  54  is to seal an unused bezel opening  30  (i.e., a bezel opening  30  without a transceiver). 
   To facilitate the formation of a seal between a bezel-opening insert and a transceiver, a flange  100  is included on both the single-width transceivers  70  and the double-width transceivers  60 . Though included in all illustrations of the transceivers,  FIGS. 3A and 3B  point out the flange  100  with particularity. The flange  100  preferably extends around the entire perimeter of the transceivers. And as illustrated in  FIGS. 3A and 3B , the flange  100  is oriented so that when a transceiver is inserted into a bezel opening  30 , the entire flange  100  is flush against a bezel-opening insert. 
   The flange  100  is preferably made of metal, or metal impregnated or metal coated plastic, so as to block electromagnetic radiation originating from inside the system  2 . In addition, the bezel  20  of the system  2  is also made of metal is preferably grounded to the overall chassis ground of the system which is in turn connected to the circuit ground at a single location. The flange  100  of each transceiver  60 ,  70  forms an electrical connection with the bezel  20  so as to ground the outside housing of the transceiver  60 ,  70 . Grounding the transceiver&#39;s housing at the opposite end from the connectors  90  helps to prevent the transceiver from transmitting electromagnetic radiation into the environment surrounding the system  2 . More generally, the bezel  20 , transceiver flanges  100  and bezel-opening inserts work together to prevent the transmission or leakage of electromagnetic radiation into the environment surrounding the system  2 . 
   Distributed across the edge of the host board  10  closest to the bezel  20  is a series of slots  80 . 
   The slots  80  are designed to guide a transceiver to a corresponding connector  90  and secure the transceiver in place once the transceiver is electrically engaged with a corresponding connector  90 . As indicated above, the slots  80  are preferably spaced evenly so that all of the slots  80  can simultaneously accommodate single-width transceivers  70 , and so that adjacent pairs of slots  80  can each accommodate a double-width transceiver  60 . Additionally, in the preferred embodiment, the slots are routed into the host board  10 . This is preferred because the amount of space required by the host board system  2  is reduced. More specifically, the portion of the transceivers that secure the transceivers to the host board  10  fits into the slots  80 , and therefore, uses space that would otherwise be inactive. As illustrated in  FIG. 1 , the difference in thickness between the host board  10  and the transceivers is not so great as to render this space-savings meaningless. Nevertheless, alternate embodiments do not route slots  80  into the host board  10 . Instead, these alternate embodiments mount a raised slot  80  onto the host board  10 . These raised slots  80  function in much the same way as the slots  80  illustrated in the various figures included herein. 
   In the preferred embodiment, as illustrated in  FIG. 4 , the transceivers  60 ,  70  include one or more guide rails  110  that slidingly engage the slots  80 . The view of the single-width transceiver  70  in  FIG. 4  is a bottom perspective of the single-width transceiver  70 , so the guide rails  110  are preferably located on a bottom surface of the transceivers and abut the flange  100 . The precise shape of the guide rail  110  is not critical so long as the guide rail  100  fits securely in each of the slots  80 . 
   Included with the guide rails  110  is a latch  120 , which is designed to secure the guide rails  110  (and thus the transceiver) within a slot  80  once the guide rail  110  is fully inserted into the slot  80 .  FIG. 4 , and the detail  112  included with  FIG. 4  in particular, illustrate part of the latch  120  that is viewable from the exterior of the guide rail  110 . The latch  120  is also illustrated by  FIG. 5  in the cut-away view  140 , which shows the latch  120  extending through a corresponding guide rail  110  and into two notches  130  on both sides of the slot  80 . As illustrated in the cut-away view  140 , the latch  120  secures the transceiver in place. To remove a transceiver, the latch  120  is slid forward which causes it to retract within the guide rail  110  and out of the notches  130 . Once the latch  120  is drawn inside the guide rail  110 , the transceiver is removable with minimal effort. 
   Also distributed across the host board  10  is a series of connectors  90 , which are preferably equal in number to the slots  80 .  FIG. 7  more clearly illustrates the connectors  90 . Note that the connectors  90  are lined-up directly behind the slots  80  so that a single-width transceiver  70  can engage a connector  90  when inserted into any of the slots  80 .  FIG. 7  illustrates double-width transceivers  60  and single-width transceivers  70  before and after being electrically interfaced with a connector  90 . 
   As indicated above, the transceivers electrically interface the connectors  90  when fully inserted into a slot  80 .  FIG. 8  illustrates functional plugs  150  and a non-functional plug  160 . Each transceiver includes at least one functional plug  150 , which passes signals between the transceiver and a connector  90  when engaged with the connector  90 . Accordingly, single-width transceivers  70  include only one plug, but double-width transceivers  60  typically include one functional plug  150  and one non-functional plug  160  as illustrated in  FIG. 8 . In a preferred embodiment, the non-functional plug  160  mechanically engages a connector, but does not electrically engage the connector  90 . The non-functional plug  160  thereby caps a connector  90  that is not accessible by other transceivers or otherwise used. In alternate embodiments, double-width transceivers  60  and wider transceivers include more than one functional plug  150  in order to increase the bandwidth of these transceivers. In yet another alternate embodiment, double-width transceivers  60  and wider transceivers include one functional plug  150  and one or more stabilizing plugs that mechanically engage with a connector and furthermore couple to ground and/or power supply connections with the connector so as to provide additional circuit ground and power supply connections to the transceiver. 
   ALTERNATE EMBODIMENTS  
   While the present invention has been described with reference to a few specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.