BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to optical connectors and, especially, to an optical connector having an optical element such as an attenuator or filter.  
           [0003]    2. Description of the Related Art  
           [0004]    Japanese patent application Kokai No. 2000-221326 discloses an optical connector having an attenuator or filter for attenuation or filtering function. As shown in FIGS. 7 and 8, this optical connector  1  comprises a housing  2 , an optical element or attenuator  3  incorporated in the housing  2 , an aligning sleeve  4  put over the attenuator  3  from the base side of the attenuator, and a body member  5  connected to the attenuator  3  via the aligning sleeve  4 .  
           [0005]    The housing  2  is made from a synthetic resin in the form of a cylinder and has a J-shaped engaging slot  6  provided in the side wall and a through-hole  7  in the axial direction. Also, it has first and second step portions  8  and  9  to form front, middle, and base sections  10 ,  11 , and  12 , respectively, so that the diameter of the through-hole  7  increases in a stepwise fashion.  
           [0006]    The attenuator  3  comprises a ferrule for holding an optical fiber  13   a  having an attenuation function and an annular stopper member  15  attached to the central area of the ferrule  14 . The stopper member  15  is made of a metal, for example, so as to have an outside diameter greater than the front section  10  but smaller than the middle section  11  and an identification mark on the outside surface to identify the attenuation characteristics and model No. of the attenuator  3 . The aligning sleeve  4  has a cylindrical form and a slit in the axial direction to provide elasticity.  
           [0007]    The body member  5  comprises an insulated cable  16 , a fixing metal  17  for fixing the front portion of the insulated cable  16 , a crimping metal  18  for fixing by crimping the insulated cable  16  to the fixing metal  17 , a ferrule  19  for holding the front portion of an optical fiber  13   b  or another optical element, a sliding sleeve  20  fixed to the base side of the ferrule  19 , and a coil spring  21  provided between the sliding sleeve  20  and the fixing metal  17  to bias the ferrule  19  forwardly. The fixing metal  17  has such a shape that it is fitted in the middle section  11  of the housing  2  and a projection  22  on the outside surface for engagement with the engaging slot  6 .  
           [0008]    To assemble such an optical connector  1 , the attenuator  3  is put into the through-hole  7  through the base side of the housing  2 , and the aligning sleeve  4  is put over the base side of the ferrule  14 . Then, the body member  5  is pushed into the housing  2  such that the projection  22  engages the engaging slot  6 . As a result, the fixing metal  17  fits in the middle section  11 , the ferrule  19  fits in the base side of the aligning sleeve  4 , and the front end of the stopper member  15  abuts on the first step portion  8 . Then, the body member  5  is further pushed into the housing  2  such that the ferrule  19  abuts face-to-face on the ferrule  14  of the attenuator  3  so that the optical fibers  13   a  and  13   b  are connected to each other and the ferrule  19  is slid toward the base side along with the sliding sleeve  20  against the coil spring  21 . Then, when the housing  2  is rotated in the predetermined direction and the pushing operation is terminated, the coil spring  21  brings the housing  2  toward the front side so that the projection  22  engages the engaging slot  6  to lock the body member  5  to the housing  2 .  
           [0009]    The above optical connector, however, requires a large amount of work for replacing the attenuator  3 . That is, each of the attenuator  3 , aligning sleeve  4 , and body member  5  is removed from the housing  2  and, then, a new attenuator is put into the housing  2 , followed by reassembling the aligning sleeve  4  and body member  5 . In addition, the attenuator  3  is so small that it is difficult to read the identification mark, frequently resulting in the installation of a wrong attenuator or the loss of a replacement attenuator.  
         SUMMARY OF THE INVENTION  
         [0010]    Accordingly, it is an object of the invention to provide an optical connector enabling to simplify the replacement operation and increase the efficiency of the operation.  
           [0011]    According to the invention there is provided an optical connector, comprising a housing; an optical element provided in the housing; retaining means for preventing separation of the optical element from the housing so that the optical element can be replaced together with the housing as a unit; the retaining means comprising a stopper member; an abutment portion provided on the housing for abutment with one end of the stopper member to restrict movement of the optical element toward one end of the housing; a retaining member secured to the housing for abutment with the other end of the stopper member to restrict movement of the optical element toward the other side, thereby preventing the optical element from falling off from the housing.  
           [0012]    It is preferred that it further comprises an aligning sleeve for aligning and holding the optical element and another optical element to be connected to the optical element and enabling to replace the optical element together with the housing and the aligning sleeve as a unit.  
           [0013]    It is further preferred that the retaining member is made such that it is press-fitted into the housing from the other side of the stopper member, it is screwed into the housing from the other side of the stopper member, or that it is inserted into the housing through a slot in a side wall of the housing.  
           [0014]    Since the optical element is made such that it is replaced together with the housing as a unit, the replacing operation is simplified, leading to the increased efficiency of the operation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is an exploded sectional view of an optical connector according to an embodiment of the invention;  
         [0016]    [0016]FIG. 2 is a partially sectional side view of the optical connector;  
         [0017]    [0017]FIG. 3 is an exploded sectional view of an optical connector according to the second embodiment of the invention;  
         [0018]    [0018]FIG. 4 is an exploded sectional view of an optical connector according to the third embodiment of the invention;  
         [0019]    [0019]FIG. 5 is an exploded sectional view of an optical connector according to the fourth embodiment of the invention;  
         [0020]    [0020]FIG. 6 is an exploded sectional view of an optical connector according to the fifth embodiment of the invention;  
         [0021]    [0021]FIG. 7 is a sectional view of a conventional optical connector; and  
         [0022]    [0022]FIG. 8 is an exploded side view of the conventional optical connector. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    In the following embodiments, the same components as those of the above conventional connector  1  will be given like reference numbers and their description will be omitted.  
         [0024]    In FIGS. 1 and 2, an optical connector  31  comprises a case  32 , a housing  33  accommodated in the case  32 , an attenuator  3 , a retaining member  34  press-fitted in the housing  33  from the base side of the housing  33 , an aligning sleeve  4 , and a body member  5 .  
         [0025]    The case  32  is made of a metal, for example, in the form of an elongated rectangular shape and an identification mark on the outside surface to identify the attenuation characteristics and model No. The case  32  has a front opening  35  at the front side, a rear opening  36  at the base side, and an inward projection  54  behind the first opening  35 .  
         [0026]    The housing  33  is made of a synthetic resin, for example, in the form of a tube and is slidable in the axial direction of the case  32 . It has an outward projection  37  on the front portion for abutment with a front face  38  of the first opening  35 . Also, it has first and second inclined surfaces  39  and  40  and a shallow indentation  41  behind the second inclined surface  40  so that the inward projection  54  abuts on the front face  55  of the indentation  41 . Further, it has a J-shaped engaging slot  50  and a through-hole  42  in the axial direction, and first, second, and third step portions  43 ,  44 , and  45  in the inside wall to enlarge stepwise the diameter of the through-hole  42  to form front, first middle, second middle, and base sections  46 ,  47 ,  48 , and  49 , respectively.  
         [0027]    The attenuator  3  comprises a ferrule  14  for holding an optical fiber  13   a  and a stopper member  15  fixed to the central area of the ferrule  14 . The stopper member  15  is made of a metal, for example, and has an outside diameter greater than the front section  46  but smaller than the first middle section  47 , and the front end for abutment with the first step portion  43 .  
         [0028]    The aligning sleeve  4  is made of a zirconia, for example, in the form of a cylinder and has a slit in the axial direction for fitting in the base side of the ferrule  14 . A retaining sleeve  51  made of a phosphorous bronze, for example, is fitted over the front portion of the aligning sleeve  4  to secure the aligning sleeve  4  to the ferrule  14 .  
         [0029]    The retaining member  34  is made of a stainless steel, for example, in the form of a cylinder and has an inside diameter of greater than the outside diameter of the retaining sleeve  51  but smaller than the stopper member  15  and the front end for abutment with the base of the stopper member  15 . It has at the front portion a jaw portion  52  having a rounded inclined surface. Its base portion  53  has an inclined outside surface and a tapered inside surface.  
         [0030]    How to assemble the optical connector  31  will be described.  
         [0031]    The housing  33  is inserted into the case  32  from the base side of the case  32  such that the inward projection  54  slides on the inclined surface  40  and snaps in the indentation  41  to attach the housing  33  to the case  32  for sliding movement. The outward projection  37  abuts on the front face  38  of the front opening  35  to restrict forward movement of the housing  38  and the inward projection  54  abuts on the notched face  55  to restrict rearward movement of the housing  38  so that the housing  38  is slidable between them in the axial direction.  
         [0032]    The attenuator  3  and then the retaining member  34  are inserted into the housing  33  from the base side of the housing. The front section and the remaining section with the jaw portion  52  and the base portion  53  of the retaining member  34  are press-fitted into the first and second middle sections  47  and  48 , respectively, so that the retaining member  34  is fixed to the housing  33 . The rounded front end and tapered jaw portion  52  and base portion  53  make this press-fitting operation easy.  
         [0033]    Then, the aligning sleeve  4  with the retaining sleeve  51  is inserted from the base side of the housing  33  into the retaining member  34  and over the base portion of the ferrule  14 . The body member  5  is pushed into the housing  33  such that the projection  22  engages the engaging slot  50  and the base portion of the aligning sleeve  4  fits over the ferrule  19 . Consequently, the ferrule  19  is brought into end-to-end contact with the ferrule  14  of the attenuator  3  to connect the optical fibers  13   a  and  13   b,  and the body member  5  is locked to the housing  33 . The front end of the stopper member  15  abuts on the first step portion  43  to restrict forward movement of the attenuator  3 , aligning sleeve  4 , and body member  5 , and the base portion of the stopper member  15  abuts on the front end of the retaining member  34  to restrict their rearward movement so that they are retained in the housing  33  for sliding movement between them in the axial direction.  
         [0034]    To replace the attenuator  3 , the housing  33  is removed from the optical connector  31  in the reverse order of the above process, and another housing in which a new attenuator and a stopper member are incorporated is inserted into the body member  5  via the aligning sleeve  4 . In this way, the number of components and operation steps for replacement of the attenuator  3  is made remarkably lower than that of the convention. The identification mark of the attenuator  3  is put in the outside surface of the housing  33  so that it is easy to read the identification mark, thus minimizing the installation of a wrong attenuator and maximizing the efficiency of the operation.  
         [0035]    In FIG. 3, a stopper member  56  has an outside surface with a sew-tooth shape and is press-fitted into the housing  33  from the base side, and a fitting groove  57  is provided in the inside surface of the housing  33  to receive the stopper member  56 .  
         [0036]    In FIG. 4, a retaining member  58  has a cylindrical form, and a press-fit portion  59  having an inside diameter smaller than the outside diameter of the retaining member  58  is provided on the inside surface of the housing. It is preferred that the base side of the press-fit portion  59  is tapered to facilitate the press-fit operation.  
         [0037]    In FIG. 5, a retaining member  60  has a threaded side surface and a screw slit  61  in the base face, and a female thread  62  is provided in the inside surface of the housing  33  for engagement with the retaining member  60  to retain the attenuator  3  in the housing  33 .  
         [0038]    In FIG. 6, a pair of insertion slots  63  are provided in the housing  33  to receive a pair of half members  64  and  64 ′ for forming a retaining member  65 . The attenuator  3  is put into the housing  33 , and the half members  64  and  64 ′ are press-fitted in the insertion slots  63  behind the stopper member  15 . The retaining member  65  may be bonded or welded to the housing  33 .  
         [0039]    It is appreciated that the pressure sleeve  51  of the embodiment in FIGS.  1 - 2  is not employed in the embodiments of FIGS.  3 - 6 .  
         [0040]    A modification may be made such that the attenuator  3  is inserted into the housing from the front side of the housing. The attenuator  3  may be replaced by a filter or isolator.  
         [0041]    Another modification may be made such that the entire housing  33  with the aligning sleeve  4  is replaced instead of only the attenuator  3  and the retaining member  34  to further reduce the number of components and operation steps for replacement.  
         [0042]    As has been described above, according to the invention, the number of components and operational steps for replacing the optical element is reduced so that the replacing operation is simplified. The identification mark of an optical element is put on the housing so that it is easy to read the ID mark, minimizing the installation of a wrong optical element. In addition, the replaceable housing minimizes the loss of a small component such as an attenuator, thus increasing the efficiency of operation.
An optical connector ( 31) comprises a housing ( 33), an optical element ( 3) incorporated in the housing ( 33), a retaining mechanism ( 15, 34, and 43) for retaining the optical element ( 3) in the housing ( 33) so that the optical element ( 3) can be replaced together with the housing ( 33) as a unit. The retaining mechanism ( 15, 34, or 43) comprises a stopper member ( 15) provided on the optical element ( 3) and a retaining member ( 34) provided on the housing ( 33) such that abutment of the stopper member ( 15) on the abutting portion of the housing ( 33) restricts movement of the optical element ( 3) toward one direction and abutment of the stopper member ( 15) on the retaining member ( 34) prevents separation of the optical element ( 3) from the housing ( 33).