Abstract:
An optical connector for optically connecting a first optical waveguide and second optical waveguide, includes a first connector module including a first fixing portion attached to a first board in such a manner that a fixed position is adjustable, a first connecting portion, a first ferrule to which the first optical waveguide is connected, and a guide pin attached to the first ferrule and provided with a tapered portion at a front end; and a second connector module including a second fixing portion fixed to a second board, a second connecting portion connectable to the first connecting portion of the first connector module, a second ferrule to which the second optical waveguide is connected and provided with a fitting hole that fits the guide pin, and a holding unit that movably holds the second ferrule.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on and claims the benefit of priority of Japanese Priority Application No. 2012-266593 filed on Dec. 5, 2012, the entire contents of which are hereby incorporated by reference. 
       FIELD 
       [0002]    The present invention relates to an optical connector, an optical connector system and an optical backplane apparatus. 
       BACKGROUND 
       [0003]    Conventionally, optical connectors in each of which a ferrule is connected to an optical fiber have been used in order to connect optical fibers while relaying lights therebetween. In order to reduce transmission loss between optical waveguides in connection, it is necessary for the optical connectors to be configured such that the ferrules are connected while facing each other in an accurate manner. In particular, high connection accuracy is required for the optical waveguides formed by a multi core optical fiber or a plurality of optical fibers. 
         [0004]    For example, Patent Document 1(Japanese Laid-open Patent Publication No. 2010-197817) discloses an optical connector capable of easily and precisely positioning optical fibers and optical elements using ferrules. 
         [0005]    Patent Document 2 (Japanese Laid-open Patent Publication No. 2008-040264) discloses an optical connector capable of inserting and pulling a plurality of optical connectors at the same time. 
         [0006]    On the other hand, in accordance with recent increases in the amount of communications using optical communications, a communication system in which a plurality of optical waveguides are aggregated has been provided. For example, there has been provided a large-scale optical waveguide integrated system in which a plurality of system boards, to each of which an optical fiber is connected, are connected to a single backplane board. 
         [0007]    In such an optical waveguide integrated system, integration density of the optical waveguides is increased by horizontally mounting a plurality of the system boards on a system rack or the like and connecting the system boards to the backplane board that is orthogonal to the system boards. 
         [0008]    Further, in such an optical waveguide integrated system, opto-electric conversion is performed in system boards and the system boards and the backplane board are electrically connected by electrical connectors, respectively. 
         [0009]    However, in order to handle light signals in the backplane board, it is necessary to use the optical connectors as explained above for passing the light signal to the backplane board without performing the opto-electric conversion. For such a system in which optical connectors are additionally provided, an operator who attaches the system boards to the backplane board has to, first, fix the system boards by sliding the system boards into slots of the system rack, and then, has to serially connect the optical connectors while taking care of bending or the like of the optical fibers. 
         [0010]    For example, Patent Document 3 (Japanese translation of PCT international application No. 2004-520604) discloses a connector that optically connects a first board and a second board orthogonal to each other. 
         [0011]    However, when optical waveguides provided to boards are connected by the conventional optical connector disclosed in Patent Documents 1 to 3, if the spaces between the system boards are narrowed in order to increase integration density of the system boards, it is difficult for an operator to insert and pull the optical connector to cause reduction of workability. In particular, when inserting or pulling one of the system boards that are already attached to the rack, workability of inserting and pulling the connector becomes worse due to the adjacent system boards, and thus, it is necessary to retain the spaces between the system boards to a certain extent. 
         [0012]    Further, generally, connection accuracy between the system rack and the system boards is lower than connection accuracy between optical connectors. Thus, it was difficult to connect optical connectors at the same time with attaching the boards like a case in which the system boards are attached to the backplane board using the electrical connectors. 
       PATENT DOCUMENT 
       [0000]    
       
         [Patent Document 1] Japanese Laid-open Patent Publication No. 2010-197817 
         [Patent Document 2] Japanese Laid-open Patent Publication No. 2008-040264 
         [Patent Document 3] Japanese translation of PCT international application No. 2004-520604 
       
     
       SUMMARY 
       [0016]    According to an embodiment, there is provided an optical connector for optically connecting a first optical waveguide and second optical waveguide, including a first connector module including a first fixing portion attached to a first board in such a manner that a fixed position is adjustable, a first connecting portion, a first ferrule to which the first optical waveguide is connected, and a guide pin attached to the first ferrule and provided with a tapered portion at a front end; and a second connector module including a second fixing portion fixed to a second board, a second connecting portion connectable to the first connecting portion of the first connector module, a second ferrule to which the second optical waveguide is connected and provided with a fitting hole that fits the guide pin, and a holding unit that movably holds the second ferrule. 
         [0017]    According to another embodiment, there is provided an optical connector system including the above described optical connector; a first optical waveguide connected to the first ferrule of the first connector module; and a second optical waveguide connected to the second ferrule of the first connector module. 
         [0018]    According to another embodiment, there is provided an optical backplane apparatus including: a plurality of the above described optical connectors; a plurality of first boards; and a second board to which the plurality of the first boards are connected via the plurality of the optical connectors, respectively. 
         [0019]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive to the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]      FIG. 1  is a perspective view illustrating an example of an optical connector of an embodiment before being fitted; 
           [0021]      FIG. 2A  and  FIG. 2B  are respective perspective views illustrating the optical connector of the embodiment after being fitted; 
           [0022]      FIG. 3  is a perspective view illustrating an example of a structure of an SB-side connector; 
           [0023]      FIG. 4  is a perspective view illustrating an example of a structure of an SB-side first housing and an SB-side ferrule; 
           [0024]      FIG. 5  is an elevation view illustrating an example of the structure of the SB-side first housing and the SB-side ferrule; 
           [0025]      FIG. 6  is a cross-sectional view taken along an A-A line in  FIG. 3 ; 
           [0026]      FIG. 7A  to  FIG. 7D  are views illustrating an example of the SB-side ferrule; 
           [0027]      FIG. 8  is a perspective view illustrating an example of a guide pin; 
           [0028]      FIG. 9  is a perspective view illustrating a structure of a BP-side connector; 
           [0029]      FIG. 10  is a cross-sectional view of the BP-side connector taken along a C-C line in  FIG. 9 ; 
           [0030]      FIG. 11  is an elevation view illustrating a fitting portion of the SB-side connector and the BP-side connector in detail; 
           [0031]      FIG. 12A  to  FIG. 12D  are views illustrating an example of the optical connector before being fitted; 
           [0032]      FIG. 13A  and  FIG. 13B  are cross-sectional views illustrating an example of the optical connector before being fitted; 
           [0033]      FIG. 14A  to  FIG. 14D  are views illustrating an example of the optical connector after being fitted. 
           [0034]      FIG. 15A  and  FIG. 15B  are cross-sectional views illustrating an example of the optical connector after being fitted; and 
           [0035]      FIG. 16  is a perspective view illustrating a fitting portion of the SB-side connector and the BP-side connector. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0036]    The invention will be described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes. 
         [0037]    It is to be noted that, in the explanation of the drawings, the same components are given the same reference numerals, and explanations are not repeated. 
         [0038]      FIG. 1  is a perspective view illustrating an example of an optical connector of the embodiment before being fitted. 
         [0039]    The optical connector includes a first connector  1  to which a first optical waveguide  14  is connected and a second connector  2  to which a second optical waveguide  26  is connected. The first connector  1  is attached to a system board  3 . 
         [0040]    The second connector  2  is attached to a backplane board  4 . 
         [0041]    Hereinafter, the “system board” is also referred to as “SD” and the “backplane board” is also referred to as “BP”. Further, hereinafter, the first connector  1  is referred to as a “SB-side connector  1 ” and the second connector  2  is referred to as a “BP-side connector  2 ”. The SB-side connector  1  engages with the BP-side connector  2 . 
         [0042]    Although not illustrated in the drawings, a plurality of the BP-side connectors  2  may be attached to the backplane board  4 . Thus, the backplane board  4  is capable of mounting a plurality of the SB-side boards  3  in an orthogonal direction by fitting the BP-side connectors  2  with the SB-side connectors  1 , respectively. 
         [0043]    The SB-side boards  3  are held by a system rack, not illustrated in the drawings, provided with a plurality of slots. Specifically, the SB-side boards  3  are held by the slots of the system rack, respectively. The slots of the system rack are formed such that the SB-side connectors  1  fit the BP-side connectors  2  when the SB-side boards  3  are slid in the slots, respectively. This means that an operator can fit the SB-side connector  1  and the BP-side connector  2  by inserting and sliding each of the SB-side boards  3  in the respective slot of the system rack. 
         [0044]      FIG. 2A  and  FIG. 2B  are respective perspective views illustrating the optical connector of the embodiment after being fitted.  FIG. 2A  illustrates the optical connector seen from a side the same as  FIG. 1  and  FIG. 2B  illustrates the optical connector seen from a side opposite from  FIG. 1 . 
         [0045]    When the SB-side connector  1  is slid toward the BP-side connector  2  in a fitting direction F 1  as illustrated in  FIG. 1 , the SB-side connector  1  and the BP-side connector  2  are fitted as illustrated in  FIG. 2A  and  FIG. 2B . 
         [0046]    As illustrated in  FIG. 2B , the SB-side connector  1  is provided with long holes  1011  and the system board  3  is fixed to the SB-side connector  1  by bolts inserted in the long holes  1011  of the SB-side connector  1 , respectively. With this configuration, the position of the SB-side connector  1  with respect to the system board  3  can be adjusted. Thus, these bolts are used when adjusting the position of the SB-side connector  1  when the system board  3  is inserted in the slot of the system rack not illustrated in the drawings. For example, the bolts may be temporarily fixed to the SB-side connector  1  and the system board  3  first. Then, after fitting the SB-side connector  1  and the BP-side connector  2  and confirming that the SB-side connector  1  and the BP-side connector  2  are appropriately fitted, the bolts may be tighten. With this operation, the SB-side connector  1  and the BP-side connector  2  can be connected with a high degree of accuracy without being influenced by attachment accuracy to the system rack. 
         [0047]      FIG. 3  is a perspective view illustrating an example of the structure of the SB-side connector  1 . 
         [0048]    The SB-side connector  1  includes an SB-side first housing  10 , an SB-side second housing  11 , and an SB-side ferrule  12 . Here, the first optical waveguide  14  is not illustrated in  FIG. 3 , although the first optical waveguide  14  is connected to a rear portion of the SB-side ferrule  12   
         [0049]    As will be explained later in detail, the SB-side first housing  10  is provided with a concave portion that extends in a width direction W and in a height direction H, and the SB-side ferrule  12  is housed in the concave portion. The SB-side first housing  10  and the SB-side second housing  11  are fixed with each other by screws with the SB-side ferrule  12  provided therebetween in the height direction H. 
         [0050]    The SB-side ferrule  12  is explained in detail with reference to  FIG. 7A  to  FIG. 8 . 
         [0051]      FIG. 7A  is a perspective view of the SB-side ferrule  12  in which guide pins  125  are inserted, seen from a front end.  FIG. 7B  is a perspective view of the SB-side ferrule  12  in which the guide pins  125  are not inserted, seen from a rear end.  FIG. 7C  is a transparent plan view of the SB-side ferrule  12  in which the guide pins  125  are inserted and  FIG. 7D  is an enlarged view of  FIG. 7C . 
         [0052]    The SB-side ferrule  12  includes an SB-side ferrule body  121 , an SB-side ferrule flange  122 , an optical waveguide placing surface  123 , guide pin insertion holes  124  and the guide pins  125 . An optical waveguide array, not illustrated in the drawings, is placed on the optical waveguide placing surface  123  that has a rectangular shape and is provided at a front end of the SB-side ferrule body  121 . The SB-side ferrule  12  is integrally formed with the optical waveguide array. The optical waveguide array is formed by a plurality of optical waveguide lens and faces a BP-side ferrule  25 , which will be explained later with reference to  FIG. 11 , at the front end in  FIG. 7A . 
         [0053]      FIG. 8  is a perspective view illustrating an example of the guide pin  125 . The guide pin  125  includes a guide pin body  1251 , a flange portion  1252  and a tapered portion  1253 . The diameter of the guide pin body  1251  may be slightly smaller than that of the guide pin insertion hole  124  illustrated in  FIG. 7B  to  FIG. 7D . With this configuration of the diameter, inappropriate force is not applied to the guide pin  125  when the guide pin  125  is inserted into the respective guide pin insertion hole  124  so that deformation of the guide pin  125  can be prevented. 
         [0054]    In this embodiment, the guide pin  125  is detachably attached to the SB-side ferrule  12 . Specifically, the guide pin  125  is attached to the SB-side ferrule  12  in such a manner that the guide pin  125  is capable of being inserted in and pulled out from the SB-side ferrule  12 . 
         [0055]    As illustrated in  FIG. 7D , the guide pin insertion hole  124  is provided with a step portion  1241  to receive the flange portion  1252  of the guide pin  125  such that the respective guide pin  125  is prevented from pulled out in the fitting direction F 1 , in other words, a lower direction in  FIG. 7C  and  FIG. 7D . 
         [0056]    Next, a method of attaching the SB-side ferrule  12  to the SB-side first housing  10  is explained with reference to  FIG. 4  to  FIG. 6 .  FIG. 4  is a perspective view illustrating the SB-side first housing  10  and the SB-side ferrule  12 .  FIG. 5  is an elevation view illustrating the SB-side first housing  10  and the SB-side ferrule  12 . 
         [0057]    As illustrated in  FIG. 4 , the SB-side first housing  10  includes an SB-side fixing portion  101 , an SB-side attachment portion  102  and an SB-side connecting portion  103 . 
         [0058]    The SB-side fixing portion  101  is provided with the long holes  1011  that function as an adjusting portion. The system board  3  is attached to the SB-side fixing portion  101  as illustrated in  FIG. 2B . The SB-side ferrule  12  is attached to the SB-side attachment portion  102 . 
         [0059]    The SB-side connecting portion  103  is provided with an SB-side insertion hole  1031  and a slit  1032  for confirming a fitting state of ferrules. 
         [0060]    The SB-side insertion hole  1031  has a tube form extending in the fitting direction F 1 . The SB-side insertion hole  1031  functions as a guide for guiding the BP-side connector  2  when the SB-side connector  1  is connected to the BP-side connector  2 . As illustrate in  FIG. 11 , a BP-side connecting portion  213  of the BP-side connector  2  is inserted in the SB-side insertion hole  1031  when the BP-side connector  2  is connected to the SB-side connector  1 . An opening portion of the SB-side insertion hole  1031  is chamfered to adjust the position of the BP-side connecting portion  213  of the BP-side connector  2 . Due to this configuration, when the BP-side connecting portion  213  of the BP-side connector  2  is inserted in the SB-side insertion hole  1031 , the SB-side ferrule  12  and the BP-side ferrule  25  are adjusted at appropriate positions such that the SB-side ferrule  12  and the BP-side ferrule  25  face each other just before the SB-side ferrule  12  and the BP-side ferrule  25  are being fitted. 
         [0061]    A function of the slit  1032  is explained later with reference to  FIG. 16 . 
         [0062]    As illustrated in  FIG. 5 , the SB-side attachment portion  102  includes an SB-side optical waveguide laying portion  1021 , a protruding portion  1022 , an SB-side flange housing portion  1023 , an SB-side ferrule width defining portion  1024 , and an SB-side ferrule exposing portion  1025 . 
         [0063]    The SB-side optical waveguide laying portion  1021  is a portion on which the first optical waveguide  14 , not illustrated in  FIG. 5 , is laid. The first optical waveguide  14  may be a single core or multi core optical fiber, or may be in an arbitrary form such as a ribbon or a sheet. The SB-side optical waveguide laying portion  1021  is formed to have a sufficient width in the width direction W so that the first optical waveguide  14  extending from the SB-side ferrule  12  can be bent. 
         [0064]    The protruding portion  1022  is provided between the SB-side optical waveguide laying portion  1021  and the flange housing portion  1023  and protrudes in the width direction W. As discussed below, the protruding portion  1022  has two functions. The SB-side ferrule  12  is housed in the concave portion formed by the SB-side flange housing portion  1023  and the SB-side ferrule width defining portion  1024  while being in contact with surfaces “a” of the protruding portion  1022 , illustrated by bold lines, facing the flange housing portion  1023 . This means that the protruding portion  1022  stops the movement of the SB-side ferrule  12  in a direction opposite to the fitting direction F 1 , in other words, in an upper direction in  FIG. 5 . Further, the protruding portion  1022  has a stops the movement of the guide pins  125 , as will be explained later. 
         [0065]    The SB-side flange housing portion  1023  is a concave portion in which the SB-side ferrule flange  122  of the SB-side ferrule  12  as illustrated in  FIG. 7A  to  FIG. 7C  is housed. The SB-side flange housing portion  1023  has a sufficient width in the width direction W to receive the SB-side ferrule flange  122  of the SB-side ferrule  12 . 
         [0066]    The SB-side ferrule width defining portion  1024  defines the position of the SB-side ferrule  12  in the width direction W at surfaces “b” as illustrated by bold lines in  FIG. 5 . There are provided slight spaces, between the SB-side ferrule width defining portion  1024  and the SB-side ferrule  12  in the width direction W. Accuracy in attachment of the SB-side ferrule  12  to the SB-side first housing  10  is determined by the spaces between the SB-side ferrule width defining portion  1024  and the SB-side ferrule  12 . 
         [0067]    The SB-side ferrule exposing portion  1025  is provided to expose an optical waveguide laying surface of the SB-side ferrule  12 . Further, the SB-side ferrule exposing portion  1025  corresponds to the slit  1032  illustrated in  FIG. 4  to facilitate confirmation of fitting. 
         [0068]      FIG. 6  is a cross-sectional view of the SB-side connector  1  taken along an A-A line in  FIG. 3  when the SB-side ferrule  12  is attached. As illustrated in  FIG. 6 , the SB-side ferrule  12  is set while having the guide pins  125  facing leftward in  FIG. 6 , in other words, the SB-side connecting portion  103 . In this embodiment, there are provided slight spaces between the SB-side ferrule  12  and the SB-side ferrule width defining portion  1024  and between the SB-side ferrule  12  and the SB-side second housing  11 , respectively. The SB-side ferrule  12  is positioned between the SB-side ferrule width defining portion  1024  and the SB-side second housing  11  while having the slight spaces therebetween so that the position of the SB-side ferrule  12  in the height direction H is determined. 
         [0069]    This means that the SB-side ferrule  12  is positioned within the housings while having the slight spaces therebetween in the width direction W and in the height direction H. With this configuration, stress due to fastening of the housings or thermal expansion can be avoided. Thus, damage to the SB-side ferrule  12  can be prevented. 
         [0070]    Next, the BP-side connector  2  is explained in detail with reference to  FIG. 9  and  FIG. 10 .  FIG. 9  is a perspective view illustrating the BP-side connector  2 .  FIG. 10  is a cross-sectional view of the BP-side connector  2  taken along a C-C line in  FIG. 9 . 
         [0071]    As illustrated in  FIG. 9 , the BP-side connector  2  includes a BP-side first housing  21 , a BP-side second housing  22 , a piston  23 , a coil spring  24  and a BP-side ferrule  25  to which a second optical waveguide  26  is connected. 
         [0072]    The BP-side first housing  21  includes a BP-side fixing portion  211 , a BP-side attachment portion  212  and the BP-side connecting portion  213 . 
         [0073]    The BP-side attachment portion  212  includes a coil spring housing portion  2121  and a BP-side optical waveguide laying portion  2122 . The BP-side fixing portion  211  is used to fix the BP-side connector  2  to the backplane board  4  in a direction orthogonal to a surface of the backplane board  4 . 
         [0074]    The BP-side connecting portion  213  is fitted with the SB-side connecting portion  103  to connect the BP-side connector  2  with the SB-side connector  1 , as will be explained later with reference to  FIG. 11 . The BP-side connecting portion  213  includes a BP-side ferrule sliding portion  2131 , a BP-side flange housing portion  2132  and a piston sliding portion  2133  provided internally. The BP-side ferrule  25  contacts with the BP-side ferrule sliding portion  2131  at its surface to be slid within the BP-side ferrule sliding portion  2131 . The BP-side flange housing portion  2132  houses the BP-side ferrule flange  252 . The piston  23  contacts with the piston sliding portion  2133  at its surface to be slid within the piston sliding portion  2133 . 
         [0075]    The BP-side second housing  22  functions as a cover of the BP-side connector  2 . The piston  23  and the coil spring  24  function to push the BP-side ferrule  25 , as will be explained later. 
         [0076]    As illustrated in  FIG. 10  and  FIG. 11 , the BP-side ferrule  25  is provided with guide pin fitting holes  251 . The guide pin fitting holes  251  function to fit the guide pins  125  of the SB-side connector  1 , respectively. In other words, the guide pin fitting holes  251  function as position determining portions that connects the first optical waveguide  14  of the SB-side ferrule  12  and the second optical waveguide  26  of the BP-side ferrule  25  with a predetermined accuracy. 
         [0077]    The second optical waveguide  26  may be a single core or multi core optical fiber, or may be in an arbitrary form such as a ribbon or a sheet. 
         [0078]    As illustrated in  FIG. 10 , the BP-side ferrule  25  is housed in the BP-side ferrule sliding portion  2131 . There is provided a slight space between the BP-side ferrule  25  and the BP-side ferrule sliding portion  2131  in the height direction H so that the BP-side ferrule  25  and the BP-side ferrule sliding portion  2131  slide with respect to each other. 
         [0079]    The piston  23  housed in the piston sliding portion  2133  is pushed by the coil spring  24  housed in the coil spring housing portion  2121  to push the BP-side ferrule  25  toward a fitting direction F 2 . The coil spring  24  has a spring constant sufficient to push the BP-side ferrule  25  to be fitted with the SB-side ferrule  12 . On the other hand, if a force that is larger than the force necessary for fitting of the BP-side ferrule  25  and the SB-side ferrule  12  is applied to the BP-side ferrule  25  via the piston  23 , the BP-side ferrule  25  slides in the BP-side connecting portion  213  in a backward direction, a direction opposite to the fitting direction F 2 . Thus, damage to the ferrules can be prevented. Further, a front end of the BP-side ferrule  25  is protruded from the BP-side ferrule sliding portion  2131 , and it is possible to clean the front end portion of the BP-side ferrule  25 . 
         [0080]    The second optical waveguide  26  passes through the piston  23  and the coil spring  24  and is connected to the backplane board  4  after being drawn from the BP-side optical waveguide laying portion  2122 . The BP-side first housing  21  is configured to retain a predetermined distance from a surface of the backplane board  4  to the BP-side optical waveguide laying portion  2122  so that the second optical waveguide  26  can be bent with a predetermined radius. 
         [0081]    Next, an operation of the guide pin  125  is explained with reference to  FIG. 11 . 
         [0082]      FIG. 11  is an elevation view illustrating a fitting portion of the SB-side connector  1  and the BP-side connector  2 . 
         [0083]    As described above, there are provided slight spaces between the SB-side ferrule  12  and the housings of the first connector  1  (the SB-side first housing  10  and the SB-side second housing  11 ) in the width direction W and in the height direction H. Similarly, as described above, there are provided slight spaces between the BP-side ferrule  25  and the housings of the BP-side connector  2  (the BP-side first housing  21  and the BP-side second housing  22 ) in the width direction W and in the height direction H. With these slight spaces, the SB-side ferrule  12  and the BP-side ferrule  25  are capable of moving freely in the width direction W and the height direction H, respectively. 
         [0084]    Further, the guide pins  125  of the SB-side connector  1  are configured to fit in the guide pin fitting holes  251  of the BP-side connector  2 , respectively. Thus, even when the SB-side ferrule  12  and the BP-side ferrule  25  are positioned at opposite sides from each other, first, for example, positions of the SB-side ferrule  12  and the BP-side ferrule  25  can be adjusted when the guide pins  125  are inserted in the guide pin fitting holes  251 , respectively. Further, as the tapered portion  1253  is provided at the front end of the guide pin  125 , the guide pin  125  can be easily fitted in the respective guide pin fitting hole  251 . 
         [0085]    A front end portion of the BP-side connecting portion  213  is chamfered and is inserted into the SB-side connecting portion  103  that is also chamfered, as described above. Further, the system board  3  to which the SB-side connector  1  is attached is slidably attached to a slot of a system rack, not illustrated in the drawings. With this configuration, the SB-side connecting portion  103  of the SB-side connector  1  and the BP-side connecting portion  213  of the BP-side connector  2  can be connected in such a way that an attachment error caused between the system board  3  and the system rack can be eliminated. 
         [0086]    The guide pin  125  is provided with the tapered portion  1253  at its front end as explained above with reference to  FIG. 8 . When the guide pin  125  fits in the respective guide pin fitting hole  251  provided at the BP-side ferrule  25 , the positions of the SB-side ferrule  12  and the BP-side ferrule  25  are determined. 
         [0087]    As described above, the SB-side ferrule  12 , the BP-side ferrule  25  and the guide pin  25  are movably attached to the respective SB-side or BP-side housing ( 10 ,  11 ,  21  or  22 ) or the guide pin insertion hole  124  with the slight space therebetween. Thus, damage due to fastening of the housings or the like can be prevented. 
         [0088]    Further, in this embodiment, there is provided a slight space between the BP-side connecting portion  213  and the SB-side connecting portion  103 . Thus, the BP-side connecting portion  213  and the SB-side connecting portion  103  move relative with respect to each other in an amount defined by the slight space when the SB-side connector  1  and the BP-side connector  2  are connected. 
         [0089]    The tapered portion of the guide pin  125  is designed taking into consideration the sizes of the slight spaces explained above. The guide pin  125  is capable of absorbing misalignment/attachment errors of the SB-side connector  1  and the BP-side connector  2  within a range, at most, corresponding to radius of the guide pin  125  in a diameter direction of the tapered portion  1253 . Thus, the diameter (or radius) of the guide pin  125  may be determined based on the design of the optical connector such as the slight spaces between the housing and the ferrule, the slight spaces between the guide pin and the guide pin insertion hole, or the like, as described above. 
         [0090]    Further, when the SB-side ferrule  12  is attached to the SB-side attachment portion  102 , the protruding portion  1022  contacts the flange portion  1252  of the guide pin  125  at the surfaces “a” (see  FIG. 5 ) so that the guide pin  125  inserted in the respective guide pin insertion hole  124  is prevented from moving and is removed in a direction opposite to the fitting direction F 1 . This means that the protruding portion  1022  has stops the movement of the guide pins  125 . 
         [0091]    A method of fitting the SB-side connector  1  and the BP-side connector  2  is explained in detail with reference to  FIG. 12A  to  FIG. 15B . 
         [0092]      FIG. 12A  is an elevation view,  FIG. 12B  is a side view, and  FIG. 12C  and  FIG. 12D  are respective perspective views, of the optical connector before being fitted.  FIG. 13A  is a cross-sectional elevation view and  FIG. 13B  is a cross-sectional side view, of the optical connector before being fitted. The numerals are the same as those explained with reference to  FIG. 1  to  FIG. 11 . 
         [0093]    As illustrated in  FIG. 12A  to  FIG. 13B , the SB-side connector  1  has a structure in which the SB-side first housing  10  and the SB-side second housing  11  are fixed by screws, and the SB-side ferrule  12  is contained within the housings. 
         [0094]      FIG. 13A  corresponds to a cross-sectional view taken along a Y-Y line illustrated in  FIG. 12B .  FIG. 13A  illustrates a state in which the SB-side connector  1  and the BP-side connector  2  are not fitted yet but the BP-side connecting portion  213  of the BP-side connector  2  is inserted in the SB-side connecting portion  103 . The SB-side ferrule  12  is attached to the SB-side attachment portion  102  and is covered by the SB-side second housing  11 . At this time, the SB-side ferrule  12  is movable within a range of the slight spaces between the SB-side attachment portion  102  and the SB-side ferrule  12 . As the SB-side ferrule  12  is attached to the SB-side attachment portion  102 , the guide pins  125  are stopped by the protruding portion  1022  of the SB-side attachment portion  102  even when the SB-side ferrule  12  is pushed by the BP-side ferrule  25 . Thus, just before the SB-side connector  1  and the BP-side connector  2  are fitted, the tapered portion  1253  at the front end portion of each of the guide pins  125  explained above with reference to  FIG. 8  is positioned to face the respective guide pin fitting hole  251  of the BP-side ferrule  25 . The BP-side ferrule  25  protrudes from the BP-side first housing  21  by being pushed by the piston  23  that is pushed by the coil spring  24 . This means that the SB-side ferrule  12  and the BP-side ferrule  25  face each other at floating states, respectively. Thus, even when the system board  3 , to which the SB-side connector  1  is attached as illustrated in  FIG. 1 , is attached to the system rack, attachment error of the system board  3  and the system rack can be absorbed by the SB-side connector  1  and the BP-side connector  2  when connecting these connectors as the SB-side ferrule  12  and the BP-side ferrule  25  face each other at a floating state. 
         [0095]    Further, as described above, there are spaces between the SB-side connector  1  and the SB-side ferrule  12 , between the BP-side connector  2  and the housings, and between the BP-side ferrule  25  and the housings. However, when the tapered portions  1253  of the guide pins  125  are inserted in the guide pin fitting hole  251 , the positions of the SB-side ferrule  12  and the BP-side ferrule  25  are adjusted within a range of the spaces between each of the guide pins  125  and the SB-side ferrule  12  and between each of the guide pins  125  and the respective guide pin fitting hole  251 . 
         [0096]    With this configuration, optical connectors can be appropriately connected at the same time as attaching the system board  3  to the system rack. Thus, workability can be increased in an optical backplane apparatus in which a plurality of the system boards  3  are orthogonally connected to the backplane board  4 . 
         [0097]      FIG. 14A  is an elevation view,  FIG. 14B  is a side view, and  FIG. 14C  and  FIG. 14D  are respective perspective views, of the optical connector after being fitted.  FIG. 15A  is a cross-sectional elevation view and  FIG. 15B  is a cross-sectional side view, of the optical connector after being fitted.  FIG. 14A  to  FIG. 15B  correspond to  FIG. 12A  to  FIG. 13B , respectively and illustrate a state when the optical connector is fitted. 
         [0098]    As illustrated in  FIG. 14A  to  FIG. 15B , the SB-side connector  1  and the BP-side connector  2  are connected. At this time, the guide pins  125  are fitted in the guide pin fitting holes  251  of the BP-side ferrule  25 , respectively, and the optical waveguide laying surfaces of the SB-side ferrule  12  and the BP-side ferrule  25  contact with each other at an appropriate position. The BP-side ferrule  25  is pushed by the SB-side ferrule  12  and the piston  23  pushed by the coil spring  24  moves backward. The contacting force of the SB-side ferrule  12  and the BP-side ferrule  25  is determined in accordance with a spring constant of the coil spring  24  and an amount moved by the coil spring  24 . With this configuration, a contacting force sufficient to stably forming an optical waveguide can be obtained. 
         [0099]    Next, a method of confirming a fitting state of the SB-side connector  1  and the BP-side connector  2  is explained with reference to  FIG. 16 . 
         [0100]      FIG. 16  is a perspective view illustrating a fitting portion of the SB-side connector and the BP-side connector.  FIG. 16  illustrates a fitting state between the SB-side ferrule  12  and the BP-side ferrule  25  just before they are fitted. 
         [0101]    Due to the slit  1032  provided at the SB-side connecting portion  103 , a fitting state between the guide pins  125  of the SB-side ferrule  12  and the guide pin fitting holes  251  of the BP-side ferrule  25  can be confirmed. Even when the SB-side connector  1  is pushed toward the BP-side connector  2  and the SB-side connecting portion  103  and the BP-side connecting portion  213  are fitted with each other, if the guide pins  125  are not fitted to the guide pin fitting holes  251 , respectively, for example, a state that the guide pins  125  are exposed can be confirmed through the slit  1032 . In this embodiment, the slit  1032  for confirming the fitting state of the ferrules is provided. Further, the SB-side ferrule  12  and the BP-side ferrule  25  face each other at floating states while the SB-side ferrule  12  and the BP-side ferrule  25  are to be fitted by the pushing force of the coil spring  24 . Thus, even if there is a slight positioning misalignment between the SB-side ferrule  12  and the BP-side ferrule  25 , the positions of the SB-side ferrule  12  and the BP-side ferrule  25  can be adjusted while confirming their positions through the slit  1032 . 
         [0102]    According to the embodiment, an optical connector capable of easily and surely connecting optical waveguides of different boards is provided. 
         [0103]    Although a preferred embodiment of the optical connector, the optical connector system and the optical backplane apparatus has been specifically illustrated and described, it is to be understood that modifications may be made therein without departing from the spirit and scope of the invention as defined by the claims. 
         [0104]    The present invention is not limited to the specifically disclosed embodiments, and numerous variations and modifications and modifications may be made without departing from the spirit and scope of the present invention.