Abstract:
An optical module is inserted into a cage containing a connector electrically connected to a conductive wiring on a host board. The cage, the connector and the conductive wiring is provided on the host board. The optical module includes a circuit board and a housing. The circuit board has a card edge connector at an edge thereof. The card edge connector mates with the connector on the host board. The housing has a conductive ceiling with a rear edge and builds the circuit board therein. The conductive ceiling has a stopper supported thereby and protrudes therefrom. The stopper extrudes from the edge of the circuit board and the rear edge of the conductive ceiling.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical module and an optical hub system. 
   2. Related Background Art 
   Publication (U.S. Pat. No. 6,335,869) discloses a transceiver module. This optical module is inserted into a cage provided on a host board. A circuit board in the optical module is electrically and mechanically connected to a connector provided on the hostboard. The optical module has a cover for suppressing the radiation of electromagnetic waves. 
   Such a transceiver module is used in a cage by inserting the transceiver module thereinto and, however, the transceiver module can be inserted upside down thereinto. When the optical module is inserted upside down in the cage, a metal cover of the optical module may come into contact with a conductive pattern provided on the host board, thereby causing a short circuit in the host board. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an optical module which prevents a short circuit from occurring therethrough in a host board when the optical module is inserted upside down in a cage on the host board. 
   One aspect of the present invention is an optical module inserted into a cage containing a connector electrically connected to a conductive wiring on a host board, and the cage, the connector and the conductive wiring is provided on the host board. The optical module comprises a circuit board and a housing. The circuit board has a card edge connector at an edge thereof. The card edge connector mates with the connector on the host board. The housing has a conductive ceiling with a rear edge and builds the circuit board therein. The conductive ceiling has a stopper supported thereby and protruding therefrom. The stopper extrudes from the edge of the circuit board and the rear edge of the conductive ceiling. 
   The stopper is provided between the conductive ceiling and the circuit board. 
   A distance from the stopper to the rear edge of the conductive ceiling is greater than a length of an exposed portion of the conductive wiring provided on the host board. 
   The housing further comprises a first projection and a second projection, and the stopper has one end connected to the first projection and another end connected to the second projection. The first projection, the second projection and the stopper are integrally formed. 
   The first projection is provided in one of the pair of sides and the second projection is provided in the other of the pair of sides. 
   In the optical module as above, the first projection and the second projection are provided in the conductive ceiling. 
   Another aspect of the present invention is an optical module inserted into a cage containing a connector electrically connected to a conductive wiring on a host board, and the cage, the connector and the conductive wiring is provided on the host board. The optical module comprises a circuit board and a housing. The circuit board has a card edge connector at an edge thereof. The card edge connector mates with the connector on the host board. The housing has a conductive ceiling with an insulating portion and builds the circuit board therein. An edge of the insulating portion of the conductive ceiling extrudes from the edge of the circuit board. 
   A width of the insulating portion is greater than a length of an exposed portion of the conductive wiring provided on the host board. 
   The insulating portion of the conductive ceiling is an insulating film coated on the conductive ceiling. 
   According to still another aspect of the present invention, an optical hub system comprises a host board, a cage and an optical module. The host board has a conductive wiring provided thereon. The cage contains a connector therein and is provided on the host board. The optical module is inserted into the cage. The optical module includes a circuit board and a housing. The circuit board has a card edge connector at an edge thereof, and the card edge connector mates with the connector in the cage. The housing builds the circuit board therein and has a conductive ceiling with a rear edge, and the conductive ceiling has a stopper supported thereby and protruding therefrom. The stopper extrudes from the edge of the circuit board and the rear edge of the conductive ceiling. 
   The stopper is provided between the conductive ceiling and the circuit board. 
   A distance from the stopper to the rear edge of the conductive ceiling is greater than a length of an exposed portion of the conductive wiring provided on the host board. 
   The connector in the cage further comprises a base portion and a connector portion supported by the base portion. The connector portion has an electrode connected to the card edge connector of the optical module, and the base portion has a front with a plurality of grooves and lead terminals provided in respective grooves. The electrode in the connector portion is connected to the conductive wiring on the host board through the lead terminals. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the optical module according to a first embodiment; 
       FIG. 2  is a perspective view showing the optical module according to the first embodiment; 
       FIG. 3  is a perspective view showing a host device; 
       FIG. 4  is a perspective view showing the host device; 
       FIG. 5  is a perspective view showing the optical module inserted in the cage; 
       FIG. 6A  is a view showing a host board and a host connector, whereas  FIG. 6B  is a sectional view showing the front end face of the host connector taken along the line II—II of  FIG. 6A ; 
       FIG. 7  is a sectional view showing the host board and host connector; 
       FIG. 8A  is a plan view showing the optical module,  FIG. 8B  is a partial sectional view showing the optical module taken along the line III—III of  FIG. 8A , and  FIG. 8C  is a bottom view showing the optical module; 
       FIG. 9  is a sectional view showing the host board and the optical module connected thereto; 
       FIG. 10  is a perspective view showing the optical module inserted upside down into the cage; 
       FIG. 11  is a perspective view showing an optical module; 
       FIG. 12A  is a view showing a cage and the optical module inserted upside down therein, whereas  FIG. 12B  is a partially enlarged view of  FIG. 12A ; 
       FIG. 13A  is a view showing the cage and the optical module inserted therein upside down according to the first embodiment, whereas  FIG. 13B  is view partially enlarged view of  FIG. 13A ; 
       FIG. 14  is a perspective view showing the rear of a modified optical module according to the first embodiment; 
       FIG. 15A  is a view showing the rear of the optical module according to the first embodiment, whereas  FIGS. 15B and 15C  are perspective views each showing the rear of a modified optical module; 
       FIG. 16  is a perspective view showing an optical module according to a second embodiment; 
       FIG. 17  is a perspective view showing the rear of the optical module according to the second embodiment; 
       FIG. 18  is a sectional view showing a host board and the optical module connected thereto; and 
       FIG. 19  is a sectional view showing the cage and the optical module inserted upside down therein. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be explained with reference to the drawings. When possible, parts identical or similar to each other will be referred to with numerals identical to each other. 
   First Embodiment 
     FIG. 1  is a perspective view showing an optical module according to a first embodiment.  FIG. 2  is a perspective view showing the optical module according to this embodiment.  FIGS. 3 and 4  are perspective views each showing a cage into which the optical module is inserted. In  FIG. 4 , the outer structure of the cage  25  is partly removed in order to show the interior of the cage  25 .  FIG. 5  is a perspective view showing the optical module. The outer structure of the cage  25  is partly removed in  FIG. 5  in order to show the optical module  10 . 
   As shown in  FIGS. 3 and 4 , a connector  21  and a metal cage  25  are provided on a host board  20 , whereas the cage  25  covers the connector  21 . The cage  25  includes side walls  25   a  and  25   b , a ceiling  25   c , a rear wall  25   d , and a bottom  25   e . These portions  25   a  to  25   e  are integrally formed with each other. The cage  25  has an opening  25   f  for receiving the optical module  10  therein. As shown in  FIG. 4 , the bottom  25   e  of the cage  25  also has an opening in which the connector  21  is located. The connector  21  has leads  22  soldered to the host board  20 , and is electrically connected to the host board  20  via the leads  22 . Referring to  FIG. 5 , the optical module  10  is connected to the connector  21  provided on a circuit board, such as the host board  20 , in an optical hub system  40 . 
   As shown in  FIGS. 1 and 2 , the optical module  10  includes a housing  12  and a circuit board  14 . The optical module  10  has a front portion  10   a , a primary portion  10   b , and a rear portion  10   c . The housing  12  includes a metal cover  16 . The cover  16  includes a pair of side walls  16   a  and  16   b  and a ceiling  16   c . These portions  16   a  to  16   c  are formed integrally. The rear of the housing  12  has an opening  16   d  for receiving the connector  21  therein. The circuit board  14  has a card edge connector  14   a  provided to be connected with the connector  21 . The optical module  10  has a stopper  18  formed integrally with the cover  16 . The stopper  18  is provided at the rear portion  10   c  of the optical module  10 . 
   As shown in  FIG. 2 , the rear edge  14   b  of the circuit board  14  is located on a first reference plane R 1 . The rear edge  16   e  of the ceiling  16   c  is located on a second reference plane R 2 . The stopper  18  is located on a third reference plane R 3 . The third reference plane R 3  is behind the first reference plane R 1  and the second reference plane R 2 . 
   If the optical module  10  is inserted upside down into the cage  25 , the stopper  18  abuts against the connector  21  before the rear edge  16   e  of the ceiling  16   c  reaches a conductive pattern on the host board  20 . The stopper  18  can prevent the ceiling  16   c  from coming into contact with the conductive pattern. 
     FIG. 6A  is a view showing components provided on the host board.  FIG. 6B  is a sectional view showing the front of the host connector taken along the line II—II of  FIG. 6A .  FIG. 7  is a view showing the host board taken along the line I—I of  FIG. 4 . 
   The host board  20  has an insulating substrate  20   a . The substrate  20   a  includes a primary surface  20   b  having first to third areas  20   c ,  20   d  and  20   e . Conductive patterns  20   f  are provided on the second area  20   d . The connector  21  is provided on the third area  20   e . The leads  22  of the connector  21  are connected to the conductive patterns  20   f , respectively. 
   The optical module  10  is inserted through the opening  25   f  of the cage  25  and is mated with the connector  21 . After the optical module has been mated with the connector  21 , the optical module  10  can receive electrical power through the connector  21  and work. Upon this mating, the electrically conductive cover  16  of the optical module  10  does not come into contact with the leads  22  of the connector  21  and the conductor pattern  20   f  of the host board  20 . Therefore, the optical module  10  can be used as a hot-swappable or hot-pluggable optical module. 
   As shown in  FIG. 6A , the host connector  21  includes a base portion  21   a  and a connector portion  21   b . The connector portion  21   b  includes electrodes  23  which are connected with the card edge connector  14   a  of the circuit board  14  in the optical module  10 . The base portion  21   a  has an electrically insulating front face  21   c , a plurality of grooves  21   e  provided in the front face  21   c , and the leads  22  provided in the respective grooves  21   e . The leads  22  connect the electrodes  23  in the connecting portion  21   b  to the conductive patterns  20   f  on the host board. A plurality of projections  21   d  are provided to form the grooves  21   e.    
   Since the base portion  21   a  has the projections  21   d , the stopper  18  of the optical module  10  abuts against the projections  21   d  and prevents the cover of the optical module from coming into contact with the leads  22  provided on the front  21   c  of the host connector  21  when the upside-down optical module  10  reaches the connector  21 . 
     FIG. 8A  is a plan view showing the optical module.  FIG. 8B  is a sectional view showing the optical module taken along the line III—III of  FIG. 8A .  FIG. 8C  is a bottom view showing the optical module. 
   Referring to  FIGS. 8A and 8C , the cover  16  has first and second projections  19   a  and  19   b . The side walls  16   a  and  16   b  are provided with the projections  19   a  and  19   b , respectively. One end of the stopper  18  is connected to one projection  19   a , whereas the other end of the stopper  18  is connected to the other projection  19   b . The stopper  18  is formed integrally with the cover  16 . The stopper  18  is projected outward from the rear ends of the side walls  16   a  and  16   b.    
   If the optical module  10  is inserted upside down into the cage  25 , the stopper  18  abuts against the connector  21  before the rear end  16   e  of the ceiling  16   c  contacts with the connector  21 . If the optical module  10  is inserted into the cage  25  in the correct orientation, the stopper  18  does not contact with the connector  21  and the circuit board  14  in the optical module  10  is mated with the connector  21 . 
   Referring to  FIG. 8B , the stopper  18  is provided between the ceiling  16   c  of the optical module and the circuit board  14 . The rear end of the cover  16  has the opening  16   d  for receiving the connector  21 . 
     FIG. 9  is a sectional view showing the optical module mated to the host connector. In a preferred example, the optical module  10  can be an optical transceiver having two insertion holes  11  which receives an optical connector  8  therein for transmitting and receiving light. However, the present invention is not limited thereto, and the optical module according to the present invention can be either an optical transmitting module including a plurality of optical transmitting subassemblies or an optical receiving module including a plurality of optical receiving subassemblies. 
   As shown in  FIG. 10 , the optical module  10  can be inserted upside down into the cage  25 .  FIG. 11  is a view showing a conventional optical module  30  with no stopper.  FIG. 12A  is a view showing the optical module  30  inserted upside down in the cage.  FIG. 12B  is an enlarged view of the region B 1  shown in  FIG. 12A .  FIG. 13A  is a view showing the optical module  10  according to the present invention, which is inserted upside down in the cage.  FIG. 13B  is an enlarged view of the region B 2  shown in  FIG. 13A . 
   As shown in  FIG. 11 , the metal cover of the optical module  30  does not have any stopper, and an edge  31  of the ceiling of the cover is located at the rear end of the optical module  30 . This edge  31  protrudes upward at the rear end of the optical module  30 . 
   If the optical module  30  is inserted upside down into the cage  25 , the edge  31  of the optical module  30  comes into contact with the conductive patterns  20   f  on the host board  20  as shown in  FIG. 12B . Since the host board  20  has already been fed with power, a short circuit occurs between the metal end  31  of the optical module  30  and the conductive patterns  20   f  through the edge  31 . 
   By contrast, as shown in  FIG. 13B , the optical module  10  has the stopper  18  formed integrally with the electrically conductive cover  16 . If the optical module  10  is inserted upside down into the cage  25 , the stopper  18  prevents the conductive patterns  20   f  from coming into contact with the electrically conductive cover  16 . If the optical module  10  is inserted in the correct orientation thereof, the circuit board  14  is connected to the connector  21  and the stopper  18  does not prevent this connection. 
     FIG. 14  is a view showing a modified optical module according to the first embodiment. This optical module  9   a  has a metal cover  26  in place of the cover  16 . The cover  26  has a ceiling  26   c  with first and second projections  29   a  and  29   b . The projections  29   a  and  29   b  are provided not at the side walls  26   a  and  26   b  but at an edge  26   e  of the ceiling  26   c . The stopper  18  projects rearward from the ceiling  26   c  and is exterior to the rear end  26   e . If the optical module  10  is inserted upside down into the cage  25 , the stopper  18  reaches the connector  21  before the rear end  26   e  of the ceiling  26   c  reaches the connector  21 , so that the end face  18   a  of the stopper  18  comes into contact with the connector  21 . 
   In the optical module  9   a , a step is provided at an edge  15   a  forms a gap between the projections  29   a  and  29   b.    
     FIG. 15A  is a side view showing the rear end of the optical module  10  according to the first embodiment. The length D 1  of the projections is preferably at least 1.5 mm, for example. The depth D 2  of the step between the stopper  18  and the ceiling  16   c  is preferably at least 0.5 mm, for example.  FIGS. 15B and 15C  are side views each showing a modified optical module according to the first embodiment. In the optical module  9   b , a projection  19   c  has a tilt between the ceiling  16   c  and stopper  18 . In the optical module  9   c  shown in  FIG. 15C , a projection  19   d  has a curve extending from an edge of the ceiling  16   c  to an edge of the stopper  18 . 
   Second Embodiment 
     FIG. 16  is a perspective view showing the bottom of an optical module  9   d .  FIG. 17  is a perspective view showing a rear end of the optical module  9   d.    
   The optical module  9   d  includes a housing  12  having an insulating member  34  and a metal cover  36 . The insulating member  34  constitutes the rear end of the housing  12 . The ceiling  36   c  of the cover and the insulating member  34  extend along a predetermined plane. 
   The rear end  14   b  of the circuit board  14  is located on a first reference plane S 1 . The rear end of the ceiling  36   c  is located on a second reference plane S 2 . The rear end of the insulating member  34  is located on a third reference plane S 3 . The third reference plane S 3  is behind the first reference plane S 1  and the second reference plane S 2 . 
   If the optical module  9   d  is inserted upside down into the cage  25 , the rear end of the insulating member  34  reaches the connector  21  before the rear end of the ceiling  36   c  contacts with the conductive patterns  20   f  of the host board  20 . 
   Referring to  FIG. 17 , the width D 3  of the insulating member  34  in the optical module  9   d is preferably at least 1.5 mm but not greater than 8.0 mm, for example. The height D 4  of the rear end face of the insulating member  34  is preferably at least 0.5 mm but not greater than 3.3 mm, for example. The insulating member  34  may be attached to the cover  36 . 
   The insulating member  34  has openings  34   e  and  34   f , and a block  38  appears at the openings  34   e  and  34   f . The heat generated by the optical module  9   d  is transmitted to the cover  36  by way of the metal block  38 . 
   The cover  36  can be used as the metal block  38 . That is, the ceiling  36   c  appears at the opening  34   e  of the insulating member  34 , and the rear wall of the cover  36  appears at the opening  34   f.    
   The insulating member  34  may be made of resin, for example. The insulating member  34  may be an insulating coating film provided on the cover  36 . 
     FIG. 18  is a sectional view showing the connector and optical module according to the second embodiment.  FIG. 19  is a sectional view showing the optical module  9   d  inserted upside down in the cage. 
   Referring to  FIG. 18 , if the optical module  9   d  is correctly inserted into the cage  25 , the rear end  14   a  of a circuit board in the optical module  9   d  is mated with the connector  21 , and the optical module  9   d  is electrically connected to the host board  20  via the leads  22 . 
   When the optical module  9   d  is inserted upside down in the cage  25  as shown in  FIG. 19 , the insulating member  34  provided at the rear end of the optical module  9   d  makes contact with the connector  21 , whereby the optical module  9   d  is not completely inserted into the cage  25 . As shown in  FIG. 19 , the insulating member  34  abuts against the host connector  21 , thereby preventing the conductive patterns  20   f  from coming into contact with the electrically conductive cover  36 .