Abstract:
An optical networking system has connector blocks, each having a series of sockets. Each socket receives an optical transceiver and provides a full EMI shield. An active cooling system has heat pipes for drawing heat from the devices, through the sockets and to a heat exchanger.

Description:
INTRODUCTION  
       [0001]     The invention relates to optical networking equipment.  
         [0002]     At present, such equipment typically comprises racks each having a board with a line of transceiver device sockets along one edge, facing outwards. Each socket comprises an electrical signal and power terminal, and an EMI housing having a front opening for insertion of the device. There is typically an array of apertures in the EMI housing for heat convection from the device inside in use.  
         [0003]     In recent years there has been good progress in miniaturisation of the electronic and laser components of the devices. This has led to development of smaller devices, giving the ability for increasing numbers of devices in a rack. This, however, has led to increasing heat generation within the volume of space of a rack. If, say, 24 connectors are now fitted in a rack instead of 8 the heat generated rises from 8×4 W to 24×4 W for the same volume.  
         [0004]     Manufacturers of transceiver devices have heretofore relied on the users to install adequate cooling equipment, possibly a fan for each group of three racks. However, despite best efforts at providing such cooling equipment it is often the case that there is a non-uniform temperature profile along a rack, and the hotter devices are prone to development of heat-induced faults.  
         [0005]     Another problem with the existing networking equipment is that the housings are inadequate for full EMI shielding because they need to be open enough for heat convection. This problem is exacerbated as the electronic and laser components operate at ever-greater frequencies, in excess of 10 Gb/sec.  
         [0006]     The invention is therefore directed towards providing optical device networking equipment providing improved cooling of transceiver devices for uniform connector temperatures, and also improved EMI shielding.  
       STATEMENTS OF INVENTION  
       [0007]     According to the invention, there is provided a transceiver networking system comprising: 
        sockets for receiving transceiver devices, the sockets being in a connector block providing an EMI shield, and     the connector block comprises an active cooling system for heat removal from the devices.        
 
         [0010]     In one embodiment, the system comprises a plurality of connector blocks whereby the sockets form a grid in a front face of a housing.  
         [0011]     In another embodiment, the cooling system comprises heat pipes.  
         [0012]     In a further embodiment, the heat pipes are at the rear of the sockets.  
         [0013]     In one embodiment, the heat pipes run along the length of the connector blocks.  
         [0014]     In another embodiment, the cooling system comprises a heat sink extending along the length of the connector block.  
         [0015]     In a further embodiment, the heat sink comprises fins extending rearwardly from the connector block.  
         [0016]     In one embodiment, the heat pipes are located between the sockets and the heat sink.  
         [0017]     In another embodiment, the system comprises a line card, which extends underneath the heat sink and is bent upwardly to connect to the sockets or transceiver devices in the sockets.  
         [0018]     In a further embodiment, the line card comprises a series of fingers, each bent upwardly to connect to a socket or transceiver device.  
         [0019]     In one embodiment, the line card is connected to the sockets or transceiver devices by a connector, which is of a high thermal conductivity material for thermal conduction through the socket, the connector, the card, and to the cooling system.  
         [0020]     In another embodiment, the card is of thin material. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:— 
         [0022]      FIG. 1  is a front perspective view of an optical networking system of the invention, in which only one connector block is shown;  
         [0023]      FIGS. 2 and 3  are front and rear perspective views of a connector block when removed from the housing;  
         [0024]      FIG. 4  is a front view showing heat pipes connected to an external heat exchanger;  
         [0025]      FIG. 5  is a front perspective view of an alternative connector block, in which an outer housing is omitted for visibility of internal parts, and  FIGS. 6 and 7  are front and rear perspective views; and  
         [0026]      FIG. 8  is a rear perspective view showing how a board is connected. 
     
    
       [0027]     Referring to FIGS.  1  to  4  a networking system  1  comprises a housing  2  and multiple connector blocks  3  for receiving transceiver devices  4 . There are multiple connector blocks  3 , one above the other, although only one of the blocks  3  is shown in FIGS.  1  to  4 , for clarity. Each connector block  3  is at the edge of a line card  5  and has sockets  6  for receiving transceiver devices  4 .  
         [0028]     Each connector block  3  has an active cooling system for removing heat by conduction through a rear wall of each socket. Referring to  FIG. 4 , the connector block  3  comprises heat pipes  20  for heat transfer to an external heat exchanger  21 . Thus, there is active and effective heat transfer from each device  4  inserted in a socket  6  in a uniform manner. This avoids hot-spots and in general improves the reliability of the optical devices. In effect, the main body of each connector block  3  forms a heat sink for initial heat conduction from the devices  4 , the remaining heat transfer being through the heat pipes  20  to the external heat exchanger  21 .  
         [0029]     Also, each socket  6  forms a complete enclosure, shielding the environment from EMI generated by the device  4  inserted in it. There are no openings for heat convection  20  because of the heat conduction paths described above.  
         [0030]     Referring to  FIGS. 5, 6 ,  7 , and  8  a connector block  30  comprises heat pipes  31  which transfer heat efficiently from sockets  32  to a heat sink  33  extending along the length of the connector block  30 . This is a more compact arrangement, not requiring an external heat exchanger.  
         [0031]     Referring specifically to  FIG. 8 , the manner in which a line card board  35  is connected to the block  30  and the devices  4  is shown. The board  35  includes a finger  36  connected at a connector  37  to each socket  32 . Each finger  36  is bent through 90° so that it fits underneath the heat sink and slots into a gap between the sockets and the heat sink  33 . The fingers  36  are of flexible PCB material, and they each have a meg array style connector  37 . Each finger  36  and the connector  37  are together a further EMI seal for the back of the socket  32 .  
         [0032]     In use, heat is conducted from the transceiver  4 , through the meg array connector  37 , the PCB  36  (which is thin), and into the heat pipes. There is also heat conduction through the rear wall of the connector block  3  and by connection to the heat pipes.  
         [0033]     The invention is not limited to the embodiments described but may be varied in construction and detail.