Patent Publication Number: US-6991471-B2

Title: Plug-in unit, a housing and an electronic apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to electronic apparatuses and, more particularly, to a plug-in unit and a housing of an electronic apparatus, which performs information processing or communication using optical modules. 
   2. Description of the Related Art 
   Among electronic apparatuses of optical communication systems that multiplex optical signals, there is one in which an optical cable is connected to a plurality of printed wiring board through optical connectors so as to perform information processing or optical communication (for example, refer to Japanese Laid-Open Patent Application No. 2000-147269). 
   There is a demand for such an electronic apparatus to increase a capacity of a trunk network due to an increase in an amount of information to be transmitted and an increase in a demand of data transmission in association with popularization of the Internet. In order to satisfy such a demand, an increase in an information transmission capacity and an improvement of functions are required for such an electronic apparatus. However, the optical connector mentioned above cannot handle a wide variety of signals, and, thus, an electronic apparatus using optical modules is used. 
   Recently, an SFP module, which is one of optical modules, has become popular, and an attachment case and a connector for attaching the SFP module are mounted to many plug-in units. Thus, in many cases, the SFP module is mounted to the plug-in unit with an optical cable connected to the attachment case. Such an SFP module is configured and arranged to permit an addition of modules or a replacement with other modules. 
   Such an electronic apparatus is connected with circuits corresponding to necessary number of lines initially so as to minimize an initial installation cost required for the electronic apparatus. Then, an addition or replacement of optical modules or electric modules may be performed if necessary. 
     FIG. 1  is a perspective view of a conventional electronic apparatus.  FIG. 2  is a plan view of a plug-in unit to which a back board is attached.  FIG. 3  is a plan view of the electronic apparatus accommodate in a locker. It should be noted that “front side” shown in  FIGS. 1 through 3  indicates a side of the electronic apparatus  10  where attachment levers  14  are provided, and “apparatus back side” indicates a side of the electronic apparatus  10  opposite to the side where the attachment levers  14  are provided. 
   As shown in  FIG. 1 through 3 , the electronic apparatus  10  generally comprises a housing  11 , a plurality of plug-in units  12  and a back board  25 . As shown in  FIG. 1 , an opening is formed in the housing  11  on the front side so that the plug-in units  12  are inserted and into the housing  11  through the opening and are accommodated in the housing  11 . 
   The plug-in unit  12  comprises a printed wiring board  13 , the attachment levers  14 , attachment cases  15 , electronic parts  16 , LED parts  17 , optical modules  18 , plugs  19 , optical cables  21  and connectors  23  for electric connection. The electronic parts are mounted on the printed wiring board  13 . 
   The attachment levers  14  for attaching the plug-in unit  12 , the attachment cases  15  for attaching the optical modules  18  and LED parts  17  for indicating operations are provided on the front side of the printed wiring board  13 . Additionally, indication labels are provided in the vicinity of the respective LED parts  17 . 
   A connector  22  to be connected to the optical module  18  is provided in each of the attachment cases  15 . As shown in  FIG. 2 , the optical cables  21  are connected to the printed wiring board  13  by attaching the optical modules  18  to the attachment cases  15 . The optical modules  18  are not always connected to all the attachment cases  15 , and only a desired number of optical modules  18  are connected to the respective attachment cases  15 . Additionally, the optical cables  21  are bundled by holders  24  so that the LED parts  17  and the indication labels can be checked easily. The connectors  23  for electric connections are mounted on the printed wiring board  13  on the back side so as to connect the back board  15  to the printed wiring board  13 . 
   The back board  25  comprises a back board body  26  and plugs  27  mounted on the back board body  26 . The back board  25  is electrically connected to the plug-in unit  12  by attaching the plugs  27  to the connectors  23 . 
   The electronic apparatus  10  is accommodated in a locker  29  as shown in  FIG. 3 , and is supported by support parts  29   a . An area A is provided between a front face  29 A and the electronic apparatus  10  so that the bundled optical cables  21  are accommodated therein. Additionally, reinforcing members  31  are provided to the support parts  29   a  of the locker  29  so as to firmly support the electronic apparatus  10 . 
   According to the electronic apparatus  10  having the above-mentioned structure, a necessary number of optical modules  18  can be mounted so as to minimize the initial investment to the electronic apparatus  10 . Additional optical modules  18  can be attached without removing the plug-in unit  12  while other lines are being in operation. The optical modules  18  can be replaced with other kinds of modules having a different transmissible distance. 
   However, there is a problem in the conventional electronic apparatus  10  in that a number of optical modules  18  for attaching the optical modules  18  is limited due to a limited area where the attachment cases  15  are provided since the attachment cases  15  are mounted to the printed wiring board  13  on the front side where the LED parts  17  and the indication labels are provided. 
   Additionally, there is a problem in that the optical cables are obstructive when inserting or removing the plug-in unit  12  since the optical modules connected to the optical cables  21  are attached to the attachment cases  15  provided on the front side of the apparatus. Further, there is a problem that it is difficult to visually recognize the LED parts  17  and the indication labels since the optical cables form an obstacle. Furthermore, the optical cables  21  connected to the plug-in unit  12 , which is to be removed from the housing  11  for maintenance check, must be removed from the plug-in unit  21  concerned, which deteriorates maintainability. 
   Additionally, there is a problem in that the reinforcing members  31  must be provided to the support parts  29   a  of the locker  29  since the area A, where the bundled optical cables  21  are accommodated when the electronic apparatus  10  is accommodated in the locker  29 , must be provided on the side of the front face  29 A of the locker  29 . 
   SUMMARY OF THE INVENTION 
   It is a general object of the present invention to provide an improved and useful electronic apparatus having a plug-in unit and a housing, in which the above-mentioned problems are eliminated. 
   A more specific object of the present invention is to provide an electronic apparatus having a plug-in unit and a housing that can easily increase a number of optical modules connected thereto. 
   Another object of the present invention is to provide an electronic apparatus having a plug-in unit and a housing that can provide easy visual recognition of LED parts and indication labels. 
   A further object of the present invention is to provide an electronic apparatus having a plug-in unit and a housing that can improve maintainability thereof. 
   In order to achieve the above-mentioned objects, there is provided according to the present invention a plug-in unit comprising: a first connector connectable to an optical module connected to an-optical cable; a connector housing accommodating the first connector and having an insertion part into which the optical module is inserted; and an attachment lever that is used for fixing the plug-in unit to a housing in which the plug-in unit is accommodated, wherein the first connector is located on a first side of the plug-in unit opposite to a second side where the attachment lever is located. 
   According to the above-mentioned invention, a plurality of the connector housings can be provided on the second side, which is a back side of the plug-in unit since no attachment lever is provided on the second side and the there is no part that may be influenced by the optical cable that extends from the optical module. Thus, a more number of the connector housings can be provided to the plug-in unit than a conventional plug-in unit that has the connector housing on the first side, which is a front side of the plug-in unit without deteriorating visibility of LED parts and indication labels that are provided on the front side of the plug-in unit. 
   In the plug-in unit according to the present invention, an open end of the insertion part may have a chamfer part that guides the optical module moving into the insertion part. 
   Additionally, there is provided according to another aspect of the present invention a housing configured and arranged to accommodate a plug-in unit, comprising: a back board to which the plug-in unit is attached; and an optical module housing mounted on the back board, the optical module detachably attaches the optical module. 
   According to the above-mentioned invention, when a maintenance work is performed on the plug-in unit, the plug-in unit can be taken out of the housing without removing the optical cable connected to the optical module, thereby improving maintenanceability. 
   In the housing according to the present invention, the optical module housing may have an engagement part configured and arranged to be engaged with the optical module so as to hold the optical module in the optical module housing. Accordingly, the plug-in unit can be attached to and detached from the housing while the optical module is maintained to be engaged with the optical module housing. 
   In the housing according to the present invention, the plug-in unit may comprise: a first connector connectable to an optical module connected to an optical cable; a connector housing accommodating the first connector and having an insertion part into which the optical module is inserted; and an attachment lever that is used for fixing the plug-in unit to the housing, wherein the first connector is located on a first side of the plug-in unit opposite to a second side where the attachment lever is located. 
   Additionally, there is provided according to another aspect of the present invention an electronic apparatus comprising: a housing including: a back board to which the plug-in unit is attached; and an optical module housing mounted on the back board so as to detachably attach the optical module; and a plug-in unit that is accommodated in the housing, the plug-in unit including: a first connector connectable to an optical module connected to an optical cable; a connector housing accommodating the first connector and having an insertion part into which the optical module is inserted; and an attachment lever that is used for fixing the plug-in unit to the housing, wherein the first connector is located on a first side of the plug-in unit opposite to a second side where the attachment lever is located. 
   According to the above-mentioned invention, a more number of the connector housings can be provided to the plug-in unit than a conventional plug-in unit without deteriorating visibility of LED parts and indication labels that are provided on the front side of the plug-in unit. 
   In the electronic apparatus according to the present invention, the optical module housing may include: a first housing provided on a first surface of the back board, the first housing forming a first insertion part that is a part of the insertion part; and a second housing provided on a second surface of the back board opposite to the first surface and forming a second insertion part that is a part of the insertion part, a metal plate being provided in the second insertion part so as to discharge static electricity, wherein the first insertion part and the second insertion part are configured and arranged to receive the optical module. 
   According to the above-mentioned invention, the optical module can be easily inserted into the first and second insertion parts. Additionally, static electricity formed in the optical module can be discharged through the metal plate, which prevents the plug-in unit form being damaged. 
   In the electronic apparatus, the metal plate may have a first elastically deformable part configured and arranged to be connected to the second surface of the back board. Additionally, the metal plate may have a second elastically deformable part configured and arranged to support the optical module. 
   In the electronic apparatus according to the present invention, the first housing may have a pair of mis-insertion preventing members each of which has an end having a chamfer part. 
   Additionally, in the electronic apparatus according to the present invention, the optical module may have an engagement protrusion, and the optical module housing may have an engagement groove that is engaged with the engagement protrusion when the optical module is attached to the optical module housing. 
   Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a conventional electronic apparatus; 
       FIG. 2  is a plan view of a plug-in unit to which a back board is attached; 
       FIG. 3  is a plan view of the electronic apparatus accommodate in a locker; 
       FIG. 4  is a perspective view of an electronic apparatus according to an embodiment of the present invention; 
       FIG. 5  is a plan view of a plug-in unit according to the present invention; 
       FIG. 6  is a plan view of a connector housing shown in  FIG. 5 ; 
       FIG. 7  is a perspective view of a connector provided in the plug-in unit shown in  FIG. 5 ; 
       FIG. 8  is a front view of the connector shown in  FIG. 7 ; 
       FIG. 9  is a plan view of a back board to which optical modules are connected; 
       FIG. 10  is an enlarged view of an optical module housing provided to the back board; 
       FIG. 11  is a cross-sectional view of a second housing shown in  FIG. 10  taken along a line XI—XI of  FIG. 10 ; 
       FIG. 12  is a cross-sectional view of the second housing shown in  FIG. 10  taken along a line perpendicular to the line XI—XI of  FIG. 10 ; 
       FIG. 13  is a plan view of an optical module; 
       FIG. 14  is a view of the optical module viewed in a direction indicated by an arrow D of  FIG. 13 ; 
       FIG. 15  is a part of the optical module in a state where the optical module is attached to the optical module housing; 
       FIG. 16  is a plan view of the plug-in unit, the back board and the optical modules before being connected; 
       FIG. 17  is a plan view of the plug-in unit, the back board and the optical modules in a state where the optical modules are connected to the back board; 
       FIG. 18  is a plan view of the plug-in unit, the back board and the optical modules in a state where the optical modules are connected to the back board and also the plug-in unit is connected to the back board; and 
       FIG. 19  is a plan view of the electronic apparatus, which is accommodated in a locker. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A description will now be given, with reference to the drawings, of an embodiment of the present invention. 
   First, a description will be given, with reference to  FIG. 4 , of an electronic apparatus  40  according to an embodiment of the present invention.  FIG. 4  is a perspective view of the electronic apparatus  40  according to the embodiment of the present invention. 
   The electronic apparatus  40  generally comprises a housing  41  and a plurality of plug-in units  42  accommodated and arranged in the hosing  41 . It should be noted that, in  FIG. 4 , “front side” indicates a side of the electronic apparatus  40  where attachment levers  44  are located, and “apparatus back side” indicates a side of the electronic apparatus  40  opposite to the side where the attachment levers  44  are located. The attachment levers  44  are provided on the apparatus front side so that each plug-in unit  42  can be removably fixed to the housing  41  of the electronic apparatus  40 . The plug-in units  42  are accommodated in the housing  41 , and are attached to a back board provided to the housing  41 . 
   A description will now be given, with reference to  FIG. 5  through  FIG. 8 , of the plug-in unit  42 .  FIG. 5  is a plan view of the plug-in unit  42  according to the present embodiment.  FIG. 6  is a plan view of a connector housing  50  shown in  FIG. 5 .  FIG. 7  is a perspective view of a connector provided in the plug-in unit  42  shown in  FIG. 5 .  FIG. 8  is a front view (viewed in a direction B in  FIG. 7 ) of the connector shown in  FIG. 7 . It should be noted that, in  FIG. 5 , “front side” indicates a side of the electronic apparatus  40  where the attachment levers  44  are located, and “back side” indicates a side of the electronic apparatus  40  opposite to the side where the attachment levers  44  are located. Additionally, arrows B 1  and B 2  in  FIG. 5  indicate directions of movement of the attachment levers  44 . 
   As shown in  FIG. 5 , each plug-in unit  42  comprises a printed wiring board  43 , the attachment levers  44 , electronic parts  45 , LED parts  46 , switch parts  47 , a connector part  48  for electrical connection and connector housings  50 . The electronic parts  45  are mounted on the printed wiring board  43 , and wiring to be electrically connected to the electronic parts  45  is formed on the printed wiring board  43 . The pair of attachment levers  44  are mounted on the front side of the printed wiring board  43  so that the plug-in unit  42  can be removably attached to the housing  41 . Also provided on the front side of the printed wiring board  43  are the LED parts  46 , the switch parts  47  and indication labels that indicate designation of the corresponding parts. 
   The attachment levers  44  are configured to be movable in the directions B 1  and B 2  shown in  FIG. 5 , respectively, so that the plug-in unit  42  is fixed to the housing  41  or pulled out of the housing  41 . The connector part  48  for electrical connection and the connector housings  50  are mounted to the printed wiring board  43  on the back side of the electronic apparatus  40 . The connector part  48  for electrical connection is configured and arranged to be connected to a plug  62  for electrical connection provided in the back board  60  mentioned later. The connector part  48  for electrical connection is provided with an engagement protrusion  49 . The engagement protrusion  49  is engaged with an engagement groove  63  provided in the plug  62  for electrical connection mentioned later. The connector housings  50  are configured and arranged to be connected with optical modules  80  attached to optical module housings  65  mentioned later. Since the LED parts, the switch parts  47  and the indication labels must be located on the front side of the electronic apparatus  40  due to their functions, an area where the connector housings  50  can be mounted is limited on the front side but there is a large freedom on the back side of the electronic apparatus  40 . 
   Thus, by providing the connector housings  50  of the printed wiring board  43  on the back side of the apparatus, a number of the connector housings  50 , which can be mounted on the printed wiring board  43 , can be increased so that a larger number of the optical modules  80  can be connected than a conventional one. Moreover, since the optical modules  80  are connected from the back side of the printed wiring board  43 , the LED parts, the switch parts  47  and the indication labels that are provided on the front side of the apparatus are prevented from being covered by optical cables  92  extending from the optical modules  80 , thereby improving the visibility of the LED parts, the switch parts  47  and the indication labels. 
   A description will now be given, with reference to  FIG. 6 , of the connector housing  50 .  FIG. 6  is a plan view of the connector housing  50 . The connector housing  50  generally comprises a connector housing body  51 , connectors  52  and the engagement protrusion  55 . Two insertion sections  51 A into which the optical modules  80  are inserted are formed on a side of the connector housing body  51  on which the optical modules to are to be connected. The connectors  52 , which are first connectors electrically connected to the optical modules  80 , are provided in the insertion sections  51 A. 
   As shown in  FIGS. 7 and 8 , each connector  52  comprises a connector body  56  and pin terminals  57  and  58 . An insertion section  56 A is formed in the connector body  56 . Ten pieces of the pin terminals  58  are arranged on an upper surface of the connector body  56  forming the insertion section  56 A, and ten pieces of the pin terminals  57  are arranged on a lower surface of the connector body  56 . A terminal part  81 A provided to each optical module  80  is insertable into the insertion section  56 A formed in the connector  52  so as to electrically connect the pin terminals  57  and the respective pin terminals  58  to each other. 
   The connector housing body  51  provides the engagement protrusion  55 , which is brought into engagement with a module housing  65  mentioned later. Moreover, a chamfer part  51 B is formed in the connector housing body  51  located in the area where the insertion section  51 A is formed. Thus, by forming the chamfer part  51 B in the connector housing body  51 , the optical module  80  can be smoothly guided to the insertion section  51 A when inserting the optical module  80  into the connector housing  50 . 
   A description will now be given, with reference to  FIGS. 9 through 12 , of the back board  60  provided in the housing  41 .  FIG. 9  is a plan view of the back board  60  to which the optical modules  80  are connected.  FIG. 10  is an enlarged view of the optical module housing provided to the back board  60 . It should be noted that a fist surface  61 A of the back board  61 A faces a side where the plug-in units  41  are connected, and a second surface  62  is opposite to the first surface  61 A.  FIG. 11  is a cross-sectional view of a second housing shown in  FIG. 10  taken along a line XI—XI of  FIG. 10 .  FIG. 12  is a cross-sectional view of the second housing shown in  FIG. 10  taken along a line perpendicular to the line XI—XI of  FIG. 10 . 
   As shown in  FIG. 9 , the back board  60  generally comprises a back board body  61 , the plugs  62  for electrical connection and the optical module housings  65 . The plugs  62  for electrical connection are configured and arranged to electrically connect the back board  60  to the plug-in units  42 , and are connected to the respective connector parts  48  for electrical connection. 
   A description will now be given, with reference to  FIG. 10 , of the optical module housing  65 . The optical module housing  65  is configured and arranged to mount the optical modules  80 , and comprises a first housing  67  and a second housing  71 . 
   The first housing  67  is arranged on the first surface  61 A of the back board body  61 . The first housing  67  comprises a first housing body  67 A and mis-insertion preventing members  68 . 
   The first housing body  67 A is provided with two insertion sections  67 B, which are first insertion sections into which the optical modules  80  are insertable. The engagement groove  69  is formed between the two insertion sections  67 B in the first housing body  67 A. The engagement groove  69  is configured and arranged to be engaged with the engagement protrusion  55  provided in the connector housing  50  so that the first housing  67  is attached to the connector housing  50 . The pair of mis-insertion preventing members  68  are provided to the first housing body  67 A on the plug-in unit side, and a chamfer part  68 A is provided on an end of each of the mis-insertion preventing members  68 . 
   Thus, by providing the pair of mis-insertion preventing members  68  to the first housing  67 , the first housing  67  to which the optical modules  80  are attached is prevented from being erroneously connected to the connector part  48  for electrical connection, thereby preventing the optical modules  80  and the connector part  48  from being damaged. Moreover, by forming the chamfer parts on the ends of the pair of mis-insertion preventing members  68 , even if there is a small misalignment existing between the connector housing and the first housing  67  when connecting the back board  60  to the plug-in units  42 , the first housing  67  can be surely connected to the connector housing  50 . 
   A description will now be given, with reference to  FIGS. 10 through 12 , of the second housing  71 . The second housing  71  is arranged on the second surface  61 B of the back board body  61 . The second housing  71  comprises a second housing body  71 A and metal plates  72 . Two second insertion sections  71 B for inserting the optical modules  80  are formed in the second housing body  71 A, and the second insertion sections  71 B are connected to the respective first insertion sections  67 B. 
   The metal plates  72  are provided to a surface of the second housing  71  forming the second insertion section  71 B and a surface of the second housing on the side of the plug-in units  42  so as to discharge a static electricity. As shown in  FIG. 11 , the metal plate  72 , which is provided to the surface of the second housing forming the second insertion sections  71 B, is provided with a plurality of spring portions  74  and an engagement part  73 . The spring sections  74  are configured and arranged to support the optical module  80 , and are made of a metal of the same as the metal plate  72 . 
   A groove is formed in the engagement part  73  so as to be engaged with an engagement protrusion  82  mentioned later. Moreover, the metal plate  72  is electrically connected to the back board  60  through a spring part  75 . 
   Thus, by providing the metal plate  72  for discharging static electricity to the second housing  71 , static electricity generated in the optical module  80  can be discharged, thereby preventing the plug-in unit  42  from being damaged. Moreover, by providing the engagement part  73  to the metal plate  72 , the engagement protrusion  82  provided to the optical module  80  is engaged with the engagement part  73 , which attaches the optical module  80  in the optical module housing  65 . 
   As shown in  FIG. 12 , the metal plate  72  arranged on the surface of the second housing  71  on the side of the plug-in units  42  is provided with the spring part  75  that serves as an elastic part. The spring part  75  is formed of a metal the same as the metal plate  72 . 
   Thus, by providing the spring part  75  formed of a metal to the second housing  71  on the plug-in unit side, the second housing  71  can be electrically connected to the plug-in unit  42 , and the second housing  71  can be slightly displaced with respect to the first housing  67 , which allows the optical module  80  being inserted smoothly into the optical module housing  65 . 
   A description will now be given, with reference to  FIGS. 13 and 14 , of the optical module  80 . The optical module  80  has a photoelectric-translation function.  FIG. 13  is a plan view of the optical module  80 .  FIG. 14  is a view of the optical module  80  shown in  FIG. 13  viewed in a direction indicated by an arrow D. It should be noted that arrows C in  FIGS. 13 and 14  indicate directions (directions C) in which a slid-type lever  83  is slidable. 
   The optical module  80  generally comprises an optical module body  80 A, a terminal part  81 A, a plurality of terminals  81 , the engagement protrusion  82 , the slide-type lever  83  and a case part  84 . The of optical module body  80 A is arranged in the case part  84 . The terminal part  81 A is provided on one end of the optical module body  80 A, and the terminals  81  are arranged in the terminal part  81 A. The terminal part  81 A is inserted in the insertion section  56 A of the connector  52 , and the optical module  80  is electrically connected to the plug-in unit  42  by the terminals  81  being brought into contact with the respective pin terminals  57  and  58 . 
   The engagement protrusion  82  and the slide-type lever  83  are provided to the case part  84  on the side where the terminal part  81  is not formed. The slide-type lever  83  is configured and arranged to be slidable in the directions C.  FIG. 15  is a view of the optical module  80  attached to the second housing  71 . It should be noted that, in  FIG. 15 , the second housing  71  is shown as a cross-sectional view. As shown in  FIG. 15 , the engagement protrusion  82  is engaged with the engagement part  73  provided to the second housing  71 . 
   The slide-type lever  83  is configured and arranged to remove the optical module  80  attached to the second housing  71 . In the state shown in  FIG. 15 , by causing the slide-type lever  83  to slide in the direction indicated by an arrow E so as to move the engagement part  73  upwardly in  FIG. 15 , the engagement protrusion  82  moves out of the groove of the engagement part  73 , which permits the optical module  80  being pulled out of the second housing  71 . 
   A description will now be given, with reference to  FIG. 16  through  FIG. 18 , a method of connecting the above-mentioned plug-in unit  42 , the back board  60  and the optical module  80 .  FIG. 16  is a plan view of the plug-in unit, the back board and the optical modules before being connected.  FIG. 17  is a plan view of the plug-in unit, the back board and the optical modules in a state where the optical modules are connected to the back board.  FIG. 18  is a plan view of the plug-in unit, the back board and the optical modules in a state where the optical modules are connected to the back board and also the plug-in unit is connected to the back board. In  FIG. 16  through  FIG. 18 , parts that are the same as the parts shown in  FIGS. 5 ,  6 ,  9 ,  10  and  13  are given the same reference numerals, and descriptions thereof will be omitted. 
   In the state shown in  FIG. 16 , the optical modules  80  to which the plugs  91  and the optical cables  92  are connected are inserted into the corresponding first and second insertion sections  67 A and  71 A, which are formed in the optical module housing  65 . As shown in  FIG. 17 , when the optical modules  80  are attached to the optical module housing  65 , terminal parts  81 A of the optical modules  80  protrude from the optical module housing  65 . It should be noted that an amount of protrusion of the terminal parts  81  are previously set so as to be smaller than an amount of protrusion of the mis-insertion preventing members  68 . Accordingly, when connecting the plug-in unit  42  to the back board  60 , the mis-insertion preventing members  68  can be brought into contact with the plug-in unit  42  prior to the optical modules  80 , thereby preventing the plug-in unit  42  and the back board  60  from being damaged due to mis-insertion. 
   The state shown in  FIG. 18  is made by connecting the plug-in unit  42  to the back board  60  to which the optical modules  80  are connected. When removing the plug-in unit  42  from the back board  60  in the state where the optical modules  80 , the back board  60  and the plug-in unit  42  are connected, there is no need to drag the optical cables away from the optical modules  80  in the present embodiment as shown in  FIG. 17 . Thus, the plug-in unit  42  can be easily attached to and detached from the back board  60 , which improves maintenanceability. 
     FIG. 19  is a plan view the electronic apparatus according to the present embodiment, which is accommodated in a locker. As shown in  FIG. 19 , in the electronic apparatus  40 , the optical cables  92  connected to the optical modules  80  extend on the back side of the apparatus, and the optical cables  92  are accommodated in an area F between a rear wall  95 C of the locker  95  and a rear wall of the electronic apparatus  40 . Therefore, it is not necessary to provide the area for accommodating the optical cables  92  on the front side of the apparatus as in the conventional one. Therefore, when accommodating the electronic apparatus  40  in the locker  95 , which can accommodate a plurality of electronic apparatuses, the front face of the electronic apparatus  40  can be substantially aligned with a front face  95 B of the locker  95 . Thus, there is no need to provide the reinforcing members to the support parts  95   a , which support the electronic apparatus as in the conventional one, thereby reducing a number of parts of the locker  95 . 
   The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
   The present application is based on Japanese priority application No. 2003-348482 file Oct. 7, 2003, the entire contents of which are hereby incorporated by reference.