Abstract:
The invention relates to a latch device for a pluggable opto-electronic module, such as an optical transceiver, for locking the module in a rail or cage system of a host machine. The latest generation of optical transceivers include all metal housings, instead of all plastic or partial plastic, to ensure adequate heat dissipation. The relatively heavier housings necessitate the use of more robust latch devices. The latch device according to the present invention includes a sliding element with arms extending therefrom for pivoting a latching hook out of engagement with the rail or cage system. In a preferred embodiment, a pair of latching hooks are provided, one on each side of the module. The latching hooks are mounted on the ends of spring arms, which extend from the same sheet of spring metal positioned across the bottom of the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims priority from U.S. patent applications Ser. Nos. 60/390,147 filed Jun. 21, 2002; 60/392,353 filed Jul. 1, 2002; 60/405,718 filed Aug. 26, 2002; and 60/453,654 filed Mar. 11, 2003. 

   TECHNICAL FIELD 
   The present invention relates to a latch for a pluggable optical transceiver, and in particular to a latch for facilitating removal of the transceiver from a guide rail or cage of a host device. 
   BACKGROUND OF THE INVENTION 
   Conventional optical transceivers include a transmitter optical subassembly (TOSA) and a receiver optical subassembly (ROSA) connected to a printed circuit board for transmitting and receiving optical signals, respectively, between an optical network and a host device. A “hot pluggable” optical transceiver includes an electronic connector electrically connected to the printed circuit board for mating with a corresponding optical coupler mounted on a printed circuit board in the host device. A cage or a rail system is provided on the host device&#39;s printed circuit board to facilitate the mating of the optical connector with the optical coupler. A latch requiring manual actuation is provided to ensure that the transceiver is secure in the cage or rail system. Conventional latch devices are disclosed in U.S. Pat. No. 5,901,263 issued May 4, 1999 in the name of Gaio et al; U.S. Pat. No. 6,287,128 issued Sep. 11, 2001 in the name of Jones et al; and U.S. Pat. No. 6,439,918 issued Aug. 27, 2002 in the name of Togami et al. 
   Unfortunately, all of the conventional latch devices were developed for relatively small, lightweight modules, and therefore not sufficiently robust for heavier modules. The latest 10GB optical transceivers have large metallic heat sinks extending from housings, which are made entirely of metal. Accordingly, any latch device for the newer transceivers needs to be considerably more robust to repeatedly engage and disengage the guide rail or cage, as well as support the entire module during removal. Moreover, conventional transceivers are mounted almost flush with a front face of the host device leaving very little of the module to grasp, while leaving gaps resulting in electro-magnetic interference (EMI) leakage. 
   An object of the present invention is to overcome the shortcomings of the prior art by providing a robust latch device for an optical transceiver that is effective for use with larger and heavier modules. 
   Another object of the present invention is to provide an improved housing front end design, which reduces EMI and is easily grasped for removal. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention relates to an optical transceiver module for insertion into an electrical coupler mounted in a guide rail or cage of a host device comprising: 
   a first optical sub-assembly for converting optical signals into electrical signals or electrical signals into optical signals; 
   a printed circuit board electrically connected to the optical sub-assembly including circuitry for controlling the optical sub-assembly; 
   a housing for supporting the optical sub-assembly and the printed circuit board therein; 
   an electrical connector extending from a first end of the housing electrically connected to the printed circuit board for mating with the electrical coupler mounted in the host device; 
   an optical couple extending outwardly from the second end of the housing for receiving an optical connector on the end of an optical fiber; 
   a reciprocating slide extending at least partially around the optical coupler moveable between a latch position and an unlatch position; 
   a first arm extending from the slide into the housing; 
   a first lever pivotally mounted to the housing; 
   a first latch hook extending outwardly from the first lever for contacting a first latching surface on the guide rail or cage for locking the module in position; and 
   a first camming surface on the first lever for engaging the first arm when the slide is in the unlatch position, thereby pivoting the first latch hook out of engagement with the first latching surface enabling removal of the module from the host device. 
   Another aspect of the present invention relates to an optical transceiver module insertable along an insertion direction into an electrical coupler of a cage or rail system in a host device, which includes a front bezel, comprising: 
   a transmission optical sub-assembly for converting electrical signals into optical signals; 
   a receiver optical sub-assembly for converting optical signals into electrical signals; 
   a printed circuit board electrically connected to the transmission and receiver optical sub-assemblies including circuitry for controlling the transmission and receiver optical sub-assemblies; 
   a housing for supporting the transmission and receiver optical sub-assemblies and the printed circuit board therein; 
   an electrical connector extending from a first end of the housing electrically connected to the printed circuit board for mating with the electrical coupler mounted in the host device; 
   a flange extending outwardly from around a second end of the housing for abutting the front bezel of the host device, said flange defining a first frontal area; 
   a duplex optical coupler extending outwardly from the second end of the housing for receiving a pair of optical connectors on the ends of a pair of optical fibers, said optical coupler defining a second frontal area, which is less than said first frontal area; and 
   a shoulder extending from opposite sides of the optical coupler for manually gripping the module to facilitate removal thereof from the host device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein: 
       FIG. 1  is an isometric view of an opto-electronic transceiver according to the present invention; 
       FIG. 2  is an exploded view of the transceiver of  FIG. 1 ; 
       FIG. 3  is an isometric view of an alternative divider shield for the transceiver of  FIG. 1  according to the present invention; 
       FIG. 4  is an isometric view of the front end of the transceiver of  FIG. 1 ; 
       FIG. 5  is a partially exploded view of internal elements of the front end of the transceiver of  FIG. 1 ; 
       FIG. 6   a  is an isometric view of an opto-electronic transceiver according to a second embodiment of the present invention; 
       FIG. 6   b  is an isometric view of the transceiver of  FIG. 6   a  with the latch in the unlatched position; 
       FIG. 7  is an isometric view of an opto-electronic transceiver according to a third embodiment of the present invention; 
       FIG. 8  is an isometric view of the transceiver of  FIG. 7  with the cover removed to illustrate the latching device; 
       FIG. 9  is an isometric view of an opto-electronic transceiver according to a fourth embodiment of the present intention; 
       FIG. 10  is an isometric view of an opto-electronic transceiver according to a fifth embodiment of the present intention; and 
       FIG. 11  is an isometric view of an opto-electronic transceiver according to a sixth embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   With reference to  FIGS. 1 ,  2 ,  3  and  4 , the pluggable optical transceiver  1  according to the present invention includes a module housing  2 , which supports a ROSA  3 , a TOSA  4 , and a printed circuit board  6 . The housing  2  is comprised of a base  7  and a heat-dissipating cover  8 , which includes a plurality of heat sink fins  9 . A plurality of lands  11  extend from the base  7  for supporting the printed circuit board  6 . A flange  12  is provided on the cover  8  for abutting a front face plate disposed on the host device, when the module is inserted therein. The flange  12  has dimensions that are taller and wider than those of the remainder of the housing  2  to provide a shield against electro-magnetic interference (EMI). A gasket  13  is wrapped around the housing  2  between the flange  12  and the host device face plate to further limit the passage of EMI. The gasket  13  can be either a foam conductive strip or a plurality of spring fingers. A snout  14 , extending from the flange  12 , is formed by a top portion  16  extending from the cover  8  and a bottom portion extending from the base  7 . The snout  14  forms an optical coupler for receiving optical connectors provided on the ends of optical fibers, which transmit optical, signals to and from the optical network. Threaded fasteners  18  are used to fix the base  7  to the cover  8 . The sides of the base  7  and cover  8  overlap to ensure proper alignment and to limit the amount of EMI, i.e. any EMI must follow a circuitous route to pass through the joint therebetween. 
   The ROSA  3  and the TOSA  4  are electrically connected to the printed circuit board  6  via a plurality of leads  19  extending from the side and rear of each of the optical subassemblies  3  and  4 . To increase the amount of available space, the printed circuit board  6  includes a daughter board  20  electrically connected to the main board  6 . An electrical connector  21 , in the form of a card edge connector from the daughter board  20 , extends from the rear end of the transceiver housing  2  for electrically connecting the transceiver  1  to a corresponding electrical coupler found at an inner end of the rail or cage system of the lost device. Compressible, non-conductive thermal pads are positioned between the cover  8  and any major heat generating elements, e.g. the ROSA  3 , the TOSA  4  and a serializer/deserializer circuit  22 . Additional thermal pads may be placed between the base  7  and the major heat generating elements. 
   The transceiver  1  is held in the rail or cage system using a latch device comprised of a reciprocating slide  26 , which is used to pivot a pair of latching lever arms  27 . The slide  26  surrounds the snout  14 , at least on three sides, and is slideable thereon between an inner, latched position and an outer, unlatched position. Arms  28  extend from the rear end of the slide  26  into the housing  2  along each side thereof. Fingers  29  are provided at the outer free end of each arm  28 , for reasons that will be explained hereinafter. In the preferred embodiment, both of the latching lever arms  27  are leaf springs formed from a single sheet of flexible metal  31 , which is mounted in the base  7 . To correctly position the sheet  31 , elongated slots  32  are cut out of the sheet  31  for receiving raised portions  33  formed in the base  7 . Each latching lever arm  27  includes a latch hook  34  for engaging a corresponding latching surface, e.g. an opening, in the guide rail or cage, and a ramped surface  36  providing a camming surface for the fingers  29 . The rear surface of the latch hook  34  is beveled to ensure the latch hook  34  is pivoted inwardly by the side wall of the guide rail or cage, while the transceiver  1  is being inserted therein. 
   In the latched position (FIG.  1 ), the latch hook  34  is normally spring bias outwardly and extends through a hole  37  in the base  7  for engaging the corresponding hole in the guide rail or cage. To disengage the transceiver  1  from the guide rail or cage, the slide  26  is pulled in the direction of the transceiver&#39;s removal. To facilitate this action, a bail  38 , pivotally mounted on the slide  26 , is provided. In so doing, the fingers  29  engages the ramped surfaces  36 , which causes the latching lever arms  27  to pivot inwardly, thereby disengaging the latch hooks  36  from the guide rail or cage (FIG.  3 ). 
   A rectangular flap  41  is bent from the sheet  31  and positioned between the ROSA  3  and the TOSA  4  forming a divide shield to limit crosstalk therebetween. Additional flaps, bent upwardly from the sheet  31  for contacting the ROSA  3  and the TOSA  4 , may be provided for grounding the ROSA  3  and the TOSA  4  to the housing  2 , i.e. to the base  7  and/or the cover  8 . Alternatively, a separate divider shield  45  can be positioned between the ROSA  3  and the TOSA  4  to provide the same protection. As illustrated in  FIG. 3 , the divider shield  45  includes OSA flaps  46   a  and  46   b  for contacting the tops of the ROSA  3  and the TOSA  4 , respectively. Coupler flaps  47   a  and  47   b  are spring biased outwardly from the side of the shield  45  for contacting, i.e. grounding, the ROSA optical coupler and the TOSA optical coupler found in the snout  14 . Grounding flaps  48   a  and  48   b  are biased upwardly from the shield  45  for contacting the inside of the heat dissipating cover  8 , thereby providing a grounding path between the base  7  and the cover  8 . 
   Spring claws  42  extend forwardly from the sheet  31  through slots  43  in the snout  14  into engagement with the slide  26  for locking the slide  26  in the latched position when an optical connector is present in the optical coupler, i.e. snout  14 . Rectangular recesses  44  in the slide  26  align with the slots  43  when in the latched position for receiving the curved outer free ends of the spring claws  42 . If an optical connector is not positioned in the snout  14 , then the relative movement between the slide  26  and the snout  14  lifts the ends of the spring claws  42  up out of engagement with the recesses  44 . However, if an optical connector is inserted into the snout  14 , then the presence of the optical connector forces the ends of the spring claws  42  into the recesses  44  and prevents them from becoming disengaged. 
   With particular reference to  FIG. 5 , a dual SC connector clip  51 , preferably nickel plated, is provided to facilitate alignment and proper spacing of the optical connectors with the ROSA  3  and the TOSA  4 . The SC connector clip  51  includes a pair of cantilevered spring arms  52  for each of the two optical connectors that are optically coupled to the transceiver  1 , as is well known in the art. Spring tabs  53 , also made from or including a conductive material, are used to mount the SC connector clip  51  to bores  54  and  55  of the ROSA  3  and the TOSA  4 , respectively. One end  57  of each spring tab  53  is inserted into a slot  58  in the SC connector clip  51  Each spring tab  53  also includes a pair of U-shaped resilient arms  59 , with the free ends  61  thereof biased outwardly for contacting the cover  8  or the base  7 . With this arrangement, the spring tabs  53  ground the ROSA  3  and the TOSA  4  to the SC Connector clip  51 , and also provide a grounding path from those two elements to the base  7  and the cover  8 . The positioning of the resilient arms  59  in contact with the bores  54  and  55  is particularly advantageous for grounding the ends of the ROSA  3  and the TOSA  4 , which extend into a cavity formed by the snout  14 . The spring tabs  53  also close off the space above and below the ROSA  3  and the TOSA  4  to limit the passage of electro-magnetic interference between the transceiver housing  2  and outside thereof. 
     FIGS. 6   a  and  6   b  illustrate an alternative embodiment of the present invention in which the bail  38  is replaced by a rectangular shoulder  61 , which extends outwardly from around the slide  26 , preferably from around all four sides of the slide  26 , but any two opposing sides would also be useful.  FIG. 6   a  illustrates the slide  26  in the latched position, while  FIG. 6   b  illustrates the slide  26  in the unlatched position. During unlatching the user applies a forces behind the shoulder  61 , in the removal direction, that initially disengages the latch hook  34  and subsequently overcomes the friction force between the electrical connector  6  and the electrical coupler to pull the transceiver  1  out of the host device. 
     FIGS. 7 and 8  illustrate another embodiment of the present invention in which a transceiver  101  includes a housing  102  defined by a base  107  and a heat dissipating cover  108 . Fins  109  extend from the heat dissipating cover  108  for increasing the surface area of thereof, i.e. increasing the amount of heat dissipation. A flange  112  extends outwardly from the sides of the housing  102  providing a hard stop and an EMI shield for the transceiver  101  upon insertion into a corresponding guide rail or cage of a host device. A snout  114  extending from the flange  112  includes a top portion  116 , provided from the cover  108 , and a bottom portion  117 , provided from the base  107 . A slide  126  includes grooves in either side thereof for receiving opposing edges of the bottom portion  116 , thereby defining a slideable engagement. Arms  128  extend rearwardly from the slide  126 , with fingers  129  extending upwardly therefrom (as opposed to fingers  29 , which extend downwardly). A sheet of flexible metal  131  extends from one side of the base  107  to the other, and includes two latching lever arms  127  bent upwardly therefrom. Each latching lever arm  127  includes a latch hook  134  and a ramped camming surface  136  for engaging the fingers  129 . A bail  138  is provided to facilitate manual grasping and actuation of the slide  126 . 
   The simplest embodiments of the present invention are illustrated in  FIGS. 9 ,  10  and  11  in which transceivers  201  include a housing  202  for supporting a ROSA, a TOSA, a printed circuit board and all the other standard elements listed above, which are provided in a conventional transceiver. As above, a flange  212  is provided to provide a stop for the transceiver  201  and to block the passage of EMI. Optical coupling is provided via a snout  214  extending from and through the flange  212 . The transceivers  201  are held in a cage or rail system  271  ( FIG. 11 ) mounted on a printed circuit board  272  of a host device simply by the friction force between the electrical connector on the transceiver and the electrical coupler on the cage or rail system. Alternatively, additional latches  276  extending from the rail  271  or mounted on a faceplate of the host device, may be provided to latch onto the flange  212 . The latches  276  are bent forming channels  277  sized to fit the edges of the flange  212 . The ends of the latches  276  are bent outwardly providing an abutment surface  278  enabling the action of inserting the transceiver  201  force the latches  276  apart so that the edges of the flanges  212  can fit into the channels  277 . To facilitate removal of the transceiver  201 , a gripping shoulder  261 , extending from around the snout  214 , is provided to enable the transceiver  201  to be grasped and pulled out of the cage or rail system. In an alternative embodiment, illustrated in  FIGS. 10 and 11 , a gripping shoulder  262  is defined by inner walls of shallow indentations in the sides of the snout  214 . Preferably, the indentations take the form of a series of elongated rectangular indentations  263  and/or an oval shaped indentation  264 ; however, any geometric shape will suffice.