Abstract:
To prevent newly developed transceiver modules from being plugged into legacy cages, which may not have the correct electrical connector therein, the new transceiver modules are built with one or more tabs extending outwardly therefrom for abutting an edge of the opening of the cage, thereby preventing the transceiver module from being fully inserted into the cage. New cages, which include the correct electrical connector, are built with slots extending from the opening of the cage to enable the tabs to pass freely, thereby enabling the transceiver module to be fully engaged in the new cage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present invention claims priority from U.S. Patent Application No. 60/715,102 filed Sep. 8, 2005, which is incorporated herein by reference for all purposes. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to an optical transceiver and cage system, and in particular to an optical transceiver and cage system that enables a new or a legacy transceiver module to be plugged into a new cage, but prevents a new transceiver model from being plugged into a legacy cage.  
       BACKGROUND OF THE INVENTION  
       [0003]     A conventional opto-electronic system, illustrated in  FIG. 1 , includes an opto-electronic module  1 , e.g. a transceiver, and a cage/guide rail assembly  2 . The module  1  includes an optical connector  3  at a front end thereof, and an electrical connector  4  at a rear end thereof. Typically, the optical connector  3  includes a pair of ports for receiving a first optical fiber to be optically coupled to a receiver optical sub-assembly (ROSA), and a second optical fiber to be optically coupled to a transmitter optical sub-assembly (TOSA). The TOSA and the ROSA are disposed adjacent one another on a module printed circuit board within a module housing  6 . For convenience, the electrical connector  4  is formed on an edge of the module printed circuit board.  
         [0004]     The cage/guide rail assembly is for mounting in a host computer device, and includes a faceplate  7  mounted on an edge of a host printed circuit board  8 , and a cage or guide rail  9  mounted on the host circuit board  8  extending from the faceplate  7 . An access hole  10  is provided in the faceplate  7  enabling the module  1  to pass therethrough into the cage  9 . An electrical connector  11  is mounted within the cage  9  for receiving the electrical connector  4 , and for transmitting electrical signals between the host computer device and the opto-electronic module  1 .  
         [0005]     Conventional optical transceiver cages are generally rectangular in shape with a rectangular opening in one end thereof for receiving the optical transceiver module. In the past, most major changes in transceiver design were accompanied by a change in the overall size of the module, i.e. from larger to smaller at one data rate (1 or 2 Gb/s), and then from larger to smaller again at larger data rates (10 Gb/s). Accordingly, there was very little confusion over which transceivers were for which cages, since only the correct transceiver would fit in the correct cage. However, recent developments in transceiver technology have not effected the size of the module resulting in some confusion over whether certain cages are compatible with certain transceiver modules, i.e. whether the cage includes certain advanced features that legacy cages do not have in their electrical interfaces.  
         [0006]     An object of the present invention is to overcome the shortcomings of the prior art by providing an optical transceiver system in which new transceiver modules can not be plugged into legacy transceiver cages, while both new and legacy transceiver modules can be plugged into new transceiver cages.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, the present invention relates to a transceiver system for mounting on a host device comprising:  
         [0008]     an opto-electronic transceiver module including: a housing including at least one tab extending therefrom; an optical coupler on a front end of the housing for coupling at least one optical fiber; at least one optical sub-assembly (OSA) for converting optical signals to electrical signals or vice versa; a printed circuit board for controlling each OSA, and transmitting electrical signals between the OSA and the host device; and a first electrical connector electrically connected to the printed circuit board; and  
         [0009]     a transceiver cage including an open front end for receiving the transceiver module, a second electrical connector for mating with the first electrical connector when the transceiver is fully inserted into the cage, and a slot for receiving each tab;  
         [0010]     whereby each tab on the transceiver module will become fully engaged into each slot on the cage to enable the first and second electrical connectors to be connected, while the tabs on the transceiver module prevent the transceiver module from being fully inserted into a legacy cage without matching slots therein.  
         [0011]     Another aspect of the present invention relates to a transceiver module for mounting in a cage on a host printed circuit board comprising:  
         [0012]     a housing including at least one tab extending therefrom;  
         [0013]     an optical coupler on a front end of the housing for coupling at least one optical fiber;  
         [0014]     at least one optical sub-assembly (OSA) for converting optical signals to electrical signals or vice versa;  
         [0015]     a printed circuit board for controlling each OSA, and transmitting electrical signals between the OSA and the host device; and  
         [0016]     an electrical connector electrically connected to the printed circuit board;  
         [0017]     whereby the tab prevents the transceiver module from being fully plugged into a cage without matching slots therein.  
         [0018]     Another aspect of the present invention relates to a transceiver cage for mounting on a host printed circuit board for receiving a transceiver module therein comprising:  
         [0019]     an open front end for receiving the transceiver module;  
         [0020]     an electrical connector for mating with an electrical connector on the transceiver module when the transceiver module is fully inserted into the cage; and  
         [0021]     a slot for receiving each tab, thereby enabling a transceiver module with one or more tabs extending therefrom to become fully inserted therein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein:  
         [0023]      FIG. 1  is an isometric view of a conventional optical transceiver system;  
         [0024]      FIG. 2  is an isometric view of a optical transceiver system according to an embodiment of the present invention;  
         [0025]      FIG. 3  is an isometric view of an optical transceiver system according to an embodiment of the present invention;  
         [0026]      FIG. 4  is an isometric view of a optical transceiver system according to an embodiment of the present invention;  
         [0027]      FIG. 5  is an isometric view of an optical transceiver system according to an embodiment of the present invention;  
         [0028]      FIG. 6  is an isometric view of a optical transceiver system according to an embodiment of the present invention;  
         [0029]      FIG. 7  is a top view of the optical transceiver module of  FIG. 6 ; and  
         [0030]      FIG. 8  is an isometric view of an optical transceiver cage according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0031]     With reference to  FIG. 2 , an optical transceiver system, according to an embodiment of the present invention, includes a generally rectangular optical transceiver module  21  and a rectangular optical transceiver cage  22 . The cage  22  has dimensions suitable to accept the transceiver module  21  in accordance with multi-source agreement standards, and is mounted on a host printed circuit board  23  with a host electrical connector therein. Some form of latching feature is usually provided on the cage, such as flexible tongue  24  for engaging a latch on the transceiver module  21 . Perforations  26  are provided in the upper wall  27  and the side wall  28  of the cage  22  to enable air to circulate over the transceiver module  21  for dissipating heat therefrom. The cage  22  has a rectangular open front end  29  enabling the transceiver module  21  to be slideably received therein. A slot or cut-out  31  in the upper wall  27  extends from the front edge thereof, i.e. the open front  29 , towards the rear end of the cage  22 .  
         [0032]     The transceiver module  21  includes an optical connector  33  at a front end thereof, and an electrical connector  34  at a rear end thereof. The optical connector  33  comprises a duplex optical connector having a pair of ports, one for receiving a first optical fiber to be optically coupled to a receiver optical sub-assembly (ROSA), and a second port for receiving a second optical fiber to be optically coupled to a transmitter optical sub-assembly (TOSA). The TOSA and the ROSA are disposed adjacent one another on a module printed circuit board within a module housing  36 . A shoulder  35  is formed in the front end of the module  21  for abutting the front edges of the top wall  27  and the side walls  28  of the cage  22  around the opening  29 . For convenience, the electrical connector  34  is formed on an edge of the module printed circuit board. A bail latch  37  extends outwardly from the module housing  36  for grasping during insertion and retraction of the module  21 , and for unlatching the tongue  24  from a mating latching feature extending from or pivotally mounted on the housing  36 . A tab or key feature  38  extends from an upper surface of the module housing  36 , preferably from the shoulder  35 , for engaging the upper wall of legacy cages that do not have slots  31 , thereby preventing the module  21  from becoming fully engaged therein. In a newer cage, such as the cage  22 , which has the slot  31 , the tab  38  is received in the slot  31 , and thereby able to be fully engaged into the cage  22  with the electrical connector  34  plugged into the host electrical connector within the cage  22 .  
         [0033]     In an alternative embodiment of the present invention illustrated in  FIG. 3 , a cage  42  includes a pair of slots  43 , one in each side wall  28  extending rearwardly from the front edges thereof, i.e. the open front end  29 . Similar to the cage  22 , the cage  42  is mounted on a host printed circuit board  23 , and includes a tongue  24  and perforations  26  in the top wall  27  and the sidewalls  28 . A corresponding transceiver module  44  includes a tab  45  extending from each side of the module housing  36 , preferably from the shoulder  35 . As above, the transceiver module  44  includes the optical connector  33 , the electrical connector  34 , and the bail latch  37 .  
         [0034]      FIG. 4  illustrates another embodiment of the present invention, which combines the features of the previous two embodiments. Accordingly, a cage  52  includes the slot  31  in the upper wall  27  thereof, as well as the slots  43  in each of the sidewalls  28 . Similar to the cage  22 , the cage  52  is mounted on a host printed circuit board  23 , and includes a tongue  24  and perforations  26  in the top wall  27  and the sidewalls  28 . A transceiver module  53  includes the tab  38  extending from the upper surface thereof, and the tabs  45  extending from each side thereof. As above, the transceiver module  53  includes the optical connector  33 , the electrical connector  34 , and the bail latch  37 .  
         [0035]     With reference to  FIG. 5 , a transceiver module  61 , similar to the aforementioned transceiver modules  21 ,  43  and  53 , includes tabs  62  which have tapered leading ends for facilitating the insertion of the module  61  into slots  63  on a corresponding cage  64 . The tapered leading edge provides a greater clearance during initial insertion of the tabs  62  into the slots  63 , and acts to guide the transceiver module  61  into position. In the illustrated embodiment, the tabs  62  are triangular in shape with a pointed leading edge, but other shapes, e.g. spherical, pentagon, octagon, are possible within the scope of the invention. The corresponding cage  64  can include rectangular slots  43 , as in the previous embodiments, or matching triangular slots  63 , as illustrated.  
         [0036]     A transceiver module  71 , illustrated in  FIGS. 6 and 7 , includes tabs  72   a  and  72   b  on each side of the housing  36  with rounded leading edges. The rounded leading edges are tapered, thereby providing the aforementioned advantages, plus they reduce the number of sharp edges provided with square or rectangular tabs and slots. In this embodiment, the tab  72   a  is longer and extends farther down the side of the housing  36  than tab  72   b . In the corresponding cage  73  slot  74   a  is sized to receive tab  72   a , while slot  74   b  is sized to receive tab  74   b . Accordingly, the tab  72   a  will abut the end of slot  74   b  before the module  71  is able to be fully plugged into the cage  73 , thereby providing a stop in case an attempt is made to insert the module  71  upside down into the cage  73 .  
         [0037]     To minimize inventory and the number of different cages required for the various systems, a cage  81 , according to another aspect of the present invention, is constructed with frangible or perforated flaps  82 , which can be removed by the end user in accordance with which particular transceiver module is being used, e.g. a transceiver module with upper surface tabs  38 , side wall tabs  44  or both. Each flap  82  can also be of any shape or size, and include a plurality of sections depending on the shapes and sizes of the tabs being used.