Abstract:
The invention relates to an optical transceiver system for use in a host device including an optical transceiver receptacle or cage with a heat dissipating structure mounted thereon. The heat dissipating structure is electronically powered by an external source in the host device, which are electrically connected by insertion of a transceiver module into the transceiver receptacle. The present invention enables optical transceivers to support very high data rates, e.g. &gt;8 Gb/s, while still supporting very high density applications, e.g. SFF/SFP. Actuating features on the transceiver module and cage enable the heat dissipating structure to be turned on when the transceiver module is fully inserted into the cage, and turned off when the transceiver module is removed or at least partially removed from the cage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention does not claim priority 
   TECHNICAL FIELD 
   The present invention relates to a heat dissipating cage for a pluggable electronic module, and in particular to a thermal electric cooler (TEC) or a fan mounted on an optical transceiver cage activated by insertion of an optical transceiver into the cage. 
   BACKGROUND OF THE INVENTION 
   Typically the size of optical transceiver modules are chosen by multiple suppliers in a consortium known as a multi-sourcing agreement (MSA). The MSA determines the specifications of the transceiver after considerable engineering effort is expended. Attributes, such as the physical size, are determined by the power dissipation of the module and typical customer cooling capabilities. Other factors contributing to the design process include the maturity of the internal technology needed to build the module, i.e. newer technology tend to be smaller and consume less power, but are less likely to be readily available in the marketplace quickly. 
   Currently, optical transceivers with data rates up to 4 Gb/s are packaged in small form factor (SFF or SFP) packages, while optical transceivers with higher data rates, e.g. 10 Gb/s, are in larger packages, such as XFP, X2, and XENPAK. A conventional XFP arrangement is illustrated in  FIG. 1 , in which an XFP transceiver module  1  is plugged into a host cage assembly  2  mounted on a host circuit board  3 . The host cage assembly  2  includes a front bezel  4 , a cage receptacle  5 , and a host electrical connector  6 . The transceiver module  1  is inserted through an opening in the front bezel  4 , and through an open front of the cage receptacle  5 , until an electrical connector on the transceiver module  1  engages the host electrical connector  6 . The cage receptacle  5  has an opening  7  in the upper wall thereof through which a heat sink  8  extends into contact with the transceiver module  1  for dissipating heat therefrom. A clip  9  is provided for securing the heat sink  8  to the cage receptacle  5  and thereby into contact with the transceiver module  1 . With this arrangement, the heat sink  8  can be changed to suit the owners&#39; individual needs without changing the basic transceiver module  1 . 
   Currently, there is motivation in the industry to extend the SFF/SFP package to 8 Gb/s or even higher data rates; however, considerable concern has been expressed on both temperature and EMI performance as well as how the large power consumption will limit the density of usage and/or the number of reaches (LR, ER, etc) available. 
   An object of the present invention is to overcome the shortcoming of the prior art by providing an optical transceiver arrangement that will support both very high data rates and very high density applications. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention relates to an optical transceiver receptacle mountable on a host printed circuit board, in a host device with a host power source, for receiving an optical transceiver module with a first electrical connector comprising: 
   a frame including a pair of side walls, an upper wall, and an open front for receiving the optical transceiver module therethrough; 
   a second electrical connector at a rear of the frame for mating with the first electrical connector when the transceiver module is inserted into the frame; 
   heat dissipating means mounted on the upper wall of the frame electrically powered by the host device; and 
   electrical connecting means for establishing an electrical connection between the heat dissipating means and the host power source when the optical transceiver module is fully inserted into the frame, and disconnecting the heat dissipating means from the host power source, when the optical transceiver module is at least partially removed from the frame. 

   
     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 a partially exploded isometric view of a conventional XFP optical transceiver arrangement; 
       FIG. 2  is a partially sectioned isometric view of an optical transceiver arrangement according to the present invention; 
       FIG. 3  is a partially sectioned isometric view of an alternative embodiment of an optical transceiver arrangement according to the present invention; 
       FIG. 4  is a partially sectioned isometric view of an alternative embodiment of an optical transceiver arrangement according to the present invention; and 
       FIG. 5  is a partially sectioned isometric view of an alternative embodiment of an optical transceiver arrangement according to the present invention; 
   

   DETAILED DESCRIPTION 
   With reference to  FIG. 2 , an optical transceiver receptacle  11  according to the present invention includes a basic rectangular frame or cage  12 , a host electrical connector  13 , and a heat dissipating structure  14  mounted on top of the frame  12 . Typically, the frame  12  has a pair of side walls; an upper wall; a rear wall; and an open front positioned near an edge of the host printed circuit board  16 . The side walls have connectors (not shown) extending from a bottom edge thereof for latching onto a host printed circuit board  16 . Ideally the frame  12  is constructed of sheet metal, to provide electromagnetic shielding, with holes to enable airflow, although other structures that include other materials, e.g. plastic, and other structures are possible. The host electrical connector  13  is disposed adjacent to the rear wall of the frame  12 , whereby when an optical transceiver module  17  with an electrical connector  18  extending therefrom, e.g. a card edge connector, is fully inserted into the receptacle  11 , the module electrical connector  18  is fully engaged in the host electrical connector  13 . 
   The heat dissipating structure  14  includes a thermal electric cooler (TEC)  19 , which extends through an opening  20  in the upper wall of the frame  2  into contact with an upper surface of the optical transceiver module  17 . First electrical contacts  21  are provided on the TEC  19  for engaging second electrical contacts  22  provided on the upper surface of the optical transceiver module  17 , whereby power can be transmitted from the host device via the transceiver module  17  to the TEC  19 . One or both of the first and second electrical contacts  21  and  22  can be spring biased outwardly to ensure good electrical contact. Alternatively, one or both of the first and second electrical contacts  21  and  22  extend outwardly for frictionally engaging each other when the transceiver module  17  is fully inserted into the frame  2 . Accordingly, the TEC  19  is electrically connected to a source of power, i.e. switched to an on-state, by the first electrical contacts  21  engaging the second electrical contacts  22  when the transceiver module  17  is fully inserted into the frame  2 , and switched to an off-state, when the transceiver module  17  is at least partially removed from the frame  2 , i.e. the first and second electrical contacts  21  and  22  become disengaged. The TEC  19  or the module  17  can include a thermostat, e.g. provided in the module&#39;s firmware, for actuating the TEC  19 , while in the on-state, whenever the temperature of the module  17  rises above a predetermined temperature, and deactivating the TEC  19 , whenever the temperature of the module  17  falls below the predetermined temperature. The thermostat enables the overall life of the TEC  19  to be extended, as well as reducing overall power consumption. Alternatively, the TEC  19  can be actuated upon entry into the on-state, i.e. when the module  17  is fully inserted into the frame  2 . 
   To improve the thermal performance of the TEC  19 , a heat sink  23  with heat dissipating pins or fins can be provided as part of the heat dissipating structure  14 . A clip, as illustrated in  FIG. 1 , can be provided to hold the heat dissipating structure  14  in place, and spring bias the heat dissipating structure  14  into contact with the transceiver module  17  and the first electrical contact  21  into contact with the second electrical contact  22 . 
   The optical transceiver module  17  includes the standard opto-electronic components of conventional transceivers including, a receiver optical sub-assembly (ROSA)  26 , a transmitter optical sub-assembly (TOSA)  27 , on optical connector  28  for aligning an optical fiber with the ROSA  26  and the TOSA  27 , and a module printed circuit board  29  including circuitry and components for controlling the ROSA  26  and TOSA  27 . Ideally the module electrical connector  18  is formed on an edge of the module printed circuit board  29 . 
   With reference to  FIG. 3 , an optical transceiver receptacle  31  according to an alternative embodiment of the present invention includes the basic rectangular frame or cage  12 , the host electrical connector  13 , and a heat dissipating structure  34  mounted on top of the frame  12 . The transceiver module  17  and the component parts thereof are identical to those of  FIG. 2 . In this embodiment, the heat dissipating structure  14 ′ includes a low profile fan  35 , which is electrically connected with a source of power, i.e. switched to the on-state, when the first electrical contact  21  engages the second electrical contact  22 , i.e. when the transceiver module  17  with module electrical connector  18  is fully inserted into the frame  12  with host electrical connector  13 . The fan  35  or the module  17  can include a thermostat, e.g. provided in the module&#39;s firmware, for actuating the fan  35 , while in the on-state, whenever the temperature of the module  17  rises above a predetermined temperature, and deactivating the fan  35 , whenever the temperature of the module  17  falls below the predetermined temperature. The thermostat enables the overall life of the fan  35  to be extended, as well as reducing overall power consumption. Alternatively, the fan  35  can be actuated automatically upon entry into the on-state, i.e. when the module  17  is fully inserted into the frame  2 . 
   With reference to  FIG. 4 , an optical transceiver receptacle  41  according to an alternative embodiment of the present invention includes the basic rectangular frame or cage  12 , a host electrical connector  43 , and a heat dissipating structure  44  mounted on top of the frame  12 . The transceiver module  17  and the component parts thereof are identical to those of  FIG. 2 , except that the electrical actuator for the heat dissipating structure  44 , i.e. the second electrical contact  22 , is replaced by a keying feature on a module electrical connector  48 . In this embodiment, the heat dissipating structure  44  includes a TEC  49 , which is electrically connected to a source of power when the keying feature on the module electrical connector  48  engages a mating feature on the host electrical connector  43 , i.e. when the transceiver module  17  is fully inserted into the frame  12 , thereby closing an electric circuit  44  providing power from the host system to the TEC  49 . The TEC  49  or the module  17  can include a thermostat, e.g. provided in the module&#39;s firmware, for actuating the TEC  49 , while in the on-state, whenever the temperature of the module  17  rises above a predetermined temperature, and deactivating the TEC  49 , whenever the temperature of the module  17  falls below the predetermined temperature. The thermostat enables the overall life of the TEC  49  to be extended, as well as reducing overall power consumption. Alternatively, the TEC  49  can be actuated upon entry into the on-state, i.e. when the module  17  is fully inserted into the frame  2 . 
   To improve the thermal performance of the TEC  49 , the heat sink  23  with heat dissipating pins or fins can be provided as part of the heat dissipating structure  44 . A clip, as illustrated in  FIG. 1 , can be provided to hold the heat dissipating structure  44  in place, and spring bias the heat dissipating structure  44  into contact with the transceiver module  17 . 
   With reference to  FIG. 5 , an optical transceiver receptacle  51  according to an alternative embodiment of the present invention includes the basic rectangular frame or cage  12 , the host electrical connector  43 , and a heat dissipating structure  54  mounted on top of the frame  12 . The transceiver module  17  and the component parts thereof are identical to those of  FIG. 2 , except that the electrical actuator for the heat dissipating structure  54 , i.e. the second electrical contact  22 , is replaced by the keying feature on the module electrical connector  48 . In this embodiment, the heat dissipating structure  54  includes a low profile fan  55 , which is electrically connected to a source of power when the keying feature on the module electrical connector  48  engages a mating feature on the host electrical connector  43 , i.e. when the transceiver module  17  is fully inserted into the frame  12 , thereby closing an electric circuit  44  providing power from the host system to the fan  55 . The fan  55  or the module  17  can include a thermostat, e.g. provided in the module&#39;s firmware, for actuating the fan  55 , while in the on-state, whenever the temperature of the module  17  rises above a predetermined temperature, and deactivating the fan  55 , whenever the temperature of the module  17  falls below the predetermined temperature. The thermostat enables the overall life of the fan  55  to be extended, as well as reducing overall power consumption. Alternatively, the fan  55  can be actuated upon entry into the on-state, i.e. when the module  17  is fully inserted into the frame  2 . 
   In an alternative embodiment the TEC or the fan can be electrically connected to the source of power, i.e. turned on/off by the host computer sending an activation code via a serial bus in the module  17  and writing to particular registers in the module&#39;s  17  eeprom. The module  17  can periodically examine the registers and depending on the state, turn on/off the TEC or the fan.