Abstract:
An optical connector adapter has a tubular sleeve having opposite open ends each for receiving a ferrule supporting an optical fiber to bring front end faces of the ferrules into contact with each other to optically connect together the optical fibers. An adapter housing supports therein the sleeve. The adapter housing has at least one elastically deformable engaging portion projecting from an outer peripheral surface portion of the adapter housing for detachable engagement directly to a mounting board or for detachable engagement to a mounting member detachably engageable with the mounting board to detachably mount the adapter housing to the mounting board.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is a division of U.S. application Ser. No. 10/651,517, filed Aug. 29, 2003 now U.S. Pat. No. 6,908,233, which is hereby incorporated by reference, and priority thereto for common subject matter is hereby claimed. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical connector plug and an optical connector adapter as well as an optical connector for holding a front end of an optical fiber and optically connecting the optical fibers. 
   2. Description of the Related Art 
   In a related art, optical connection of optical fibers used in optical communication is carried out by a method of using an optical connector having an optical connector plug holding a front end of the optical fiber and an optical connector adapter for carrying out optical connection of the optical fibers by fixing the optical connector plugs, or a method of welding front end faces of the optical fibers. 
   According to the optical connection of the optical fibers achieved by a welding process, there is a problem that attachment and detachment of the optical connection of the optical fibers cannot be carried out and a problem that the welding steps are complicated, thereby restricting the use of the optical connector. 
   Further, according to an optical connector of an SC type, an FC type or the like for carrying out optical connection by using a cylindrical member for a ferrule holding an optical fiber and having an outer diameter of φ2.5 mm, the optical connector cannot be downsized and a wide mounting area is needed in mounting the optical connector to a mounting board. 
   Therefore, there has been proposed an MU type optical connector using a cylindrical member for a ferrule holding an optical fiber and having an outer diameter of φ1.25 mm and comparatively downsized (for example, refer to nonpatent literature 1 described below). 
   According to the MU type optical connector, an optical connector plug and an optical connector adapter are difficult to disengage from each other and reliability of optical connection can be promoted. However, such an MU type optical connector is generally designed to carryout optical connection using an optical fiber cord provided with a tension member and a coating further on an outer periphery of an optical fiber core line provided with a coating on an outer periphery of an optical fiber to carry out optical connection at a panel face on an outer side of an optical transmission apparatus. Therefore, a number of parts is large and downsizing thereof is difficult. Therefore, a wide mounting are is needed for mounting a comparatively small-sized MU type optical connector at a mounting board and there poses a problem that downsizing of the mounting board per se cannot be achieved. 
   Further, when the optical connector of the related art is mounted to the mounting board, the optical adapter is directly fixed to the mounting board and therefore, a space for attaching and detaching the optical connector plug holding the optical fiber is needed on the mounting board and there poses a problem that not only the mounting board is large-sized but also operational efficiency is poor. 
   Further, there is a problem that the conventional optical connector has a large number of parts and that integration of the optical connector flag and the optical connector adapter of the conventional optical connector is difficult to achieve. 
   In order to resolve such a problem, there has been proposed an optical connector for urging to hold a ferrule holding an optical fiber to a side of a front end face thereof in an axial direction by a leaf spring fixed to a mounting board to thereby bring the front end faces of the ferrules into contact with each other by predetermined pressure (for example, refer to patent literatures 1 and 2). 
   (patent literature 1) 
   JP-A-2-259708 (pages 1 through 2, FIGS. 1 through 3) 
   (patent literature 2) 
   JP-UM-A-6-73705 (page 5, FIG. 1) 
   (nonpatent literature 1) 
   Japanese Industrial Standards (JIS) C5983 F14 type connector 
   However, according to the above-described optical connector using the leaf spring, there poses a problem that owing to durability performance of the leaf spring, when attachment and detachment are repeated, durability of the leaf spring is deteriorated, a deterioration in opposing connection of optical fibers, that is, a deterioration in insertion loss is brought about and therefore, a number of times of attachment and detachment is restricted. 
   Further, according to the above-described optical connector using the leaf spring, since there is no means for restricting movement of the ferrule holding the front end of the optical fiber in a rotating direction centering on an axis thereof, an eccentric direction of the core of the optical fiber cannot be prescribed and the inserting loss is increased by bringing about an eccentric shift of the core. 
   Further, according to the above-described optical connector using the leaf spring, there poses a problem that the ferrule is liable to disengage from the leaf spring by vibration and impact and the reliability is poor. 
   Further, according to the above-described optical connector using the leaf spring, the front end portion of the cylindrical body for ferrule is directly inserted into a sleeve for optical connection and therefore, there poses a problem that a defect is liable to be brought about at the polished front end face of the cylindrical member for ferrule when an inserting angle is large or by repeating attachment and detachment, the inserting loss in optical connection is liable to increase and the reliability is poor. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an optical connector which promotes reliability by reducing insertion loss of an optical fiber and which is downsized. 
   In order to resolve the above-described problem, according to a first aspect of the invention, there is provided an optical connector plug comprising a ferrule including a cylindrical member for the ferrule for holding an optical fiber and a flange member provided at a rear end portion of the cylindrical member for the ferrule, an urge spring provided on a side of a rear end portion of the flange member of the ferrule, and a plug housing for holding the ferrule and the urge spring directly at inside thereof and directly engaged with an optical connector adapter inserted with a front end portion of the ferrule to carry out optical connection, wherein the plug housing is formed with a slit capable of inserting the optical fiber in a radius direction thereof at a portion of an outer periphery thereof over an axial direction. 
   According to a second aspect of the invention, there is provided the optical connector plug according to the first aspect, wherein the rear end portion of the flange member is provided with an engaging portion for engaging with the plug housing and the plug housing includes a holding hole for holding the ferrule in a state of being urged by the urge spring to a front end side in the axial direction by engaging with the engaging portion of the flange member and a first rotation stopper portion engaged with the flange member for restricting movement of the ferrule in a rotating direction centering on an axis thereof. 
   According to a third aspect of the invention, there is provided the optical connector plug according to the second aspect, wherein the first rotation stopper portion of the plug housing is provided to be able to change relative positions of the plug housing and the ferrule in a state in which the ferrule is pushed against the urge spring. 
   According to a fourth aspect of the invention, there is provided the optical connector plug according to any one of the first through the third aspects, wherein the flange member is engaged with the optical connector adapter to restrict the ferrule from moving in the rotating direction centering on the axis of the ferrule. 
   According to a fifth aspect of the invention, there is provided the optical connector plug according to any one of the second through the fourth aspects, wherein the flange member includes an outer periphery a section of which is rectangular, and the ferrule is restricted from moving in the rotating direction by bringing the first rotation stopper portion into contact with two faces of an outer peripheral face of the flange member on one side opposed to each other and bringing two faces of the flange member on other side into contact with the optical connector adapter. 
   According to a sixth aspect of the invention, there is provided the optical connector plug according to any one of the first through the fourth aspects, wherein the outer peripheral face of the flange member is provided with an urge spring engaging projection projected over the circumferential direction for engaging with the urge spring. 
   According to a seventh aspect of the invention, there is provided the optical connector plug according to any one of the first through the sixth aspects, wherein an outer diameter of the cylindrical member for the ferrule is 1.25 mm. 
   According to an eighth aspect of the invention, there is provided an optical connector including the optical connector plug according to any one of the first through the seventh aspects. 
   According to a ninth aspect of the invention, there is provided an optical connector adapter comprising a sleeve for optical connection inserted with ferrules holding optical fibers from sides of both ends thereof for bringing end faces of the ferrules into contact with each other to be connected optically, and an adapter housing holding the sleeve for optical connection and, optically coupling optical connector plugs held by the ferrules, wherein an outer periphery of the adapter housing is provided with a first mount engaging portion attachably and detachably engaging with a mounting board or a mounting member attachably and detachably fixed to the mounting board to project from one face thereof. 
   According to a tenth aspect of the invention, there is provided the optical connector adapter according to the ninth aspect, wherein the adapter housing comprising a housing main body provided by integral molding to open a sleeve inserting hole inserting to hold the sleeve for optical connection on one side of a side face thereof, and a lid member fitted to the sleeve inserting hole of the housing main body, wherein the lid member is integrally provided with the first mount engaging portion projected to a side of other face of the housing main body. 
   According to an eleventh aspect of the invention, there is provided the optical connector adapter according to the tenth aspect, wherein engagement of the lid member by the first mount engaging portion is disengaged by an attaching and detaching jig. 
   According to a twelfth aspect of the invention, there is provided the optical connector adapter according to the eleventh aspect, wherein the attaching and detaching jig is provided with a shape of a pin and the engagement is disengaged by elastically deforming the first mount engaging portion by inserting the attaching and detaching jig between the first mount engaging portion and the housing main body. 
   According to a thirteenth aspect of the invention, there is provided the optical connector adapter according to the ninth aspect, wherein the adapter housing is formed by integral molding and the one face of the adapter housing is provided with a sleeve inserting hole for inserting the sleeve for optical connection. 
   According to a fourteenth aspect of the invention, there is provided the optical connector according to any one of the ninth through the thirteenth aspects, wherein an inner side of an outer edge of an opening of the sleeve inserting hole is provided with a projection of the sleeve brought into contact with an outer peripheral face of the sleeve for optical connection for preventing detachment from the sleeve inserting hole. 
   According to a fifteenth aspect of the invention, there is provided the optical connector adapter according to any one of the ninth through the fourteenth aspects, wherein the side of the other face of the adapter housing is provided with a second mount engaging portion for engaging with the first mount engaging portion of other one of the adapter housing. 
   According to a sixteenth aspect of the invention, there is provided the optical connector adapter according to the fifteenth aspect, wherein a plurality of pieces of the adapter housings are laminated. 
   According to a seventeenth aspect of the invention, there is provided the optical connector adapter according to any one of the ninth through the sixteenth aspects, wherein the adapter housing is provided with a second rotation stopper portion engaged with an outer periphery of the ferrule for restricting the ferrule from moving in a rotating direction. 
   According to an eighteenth aspect of the invention, there is provided an optical connector comprising the optical connector adapter according to any one of the ninth through the seventeenth aspects. 
   According to a nineteenth aspect of the invention, there is provided an optical connector comprising a ferrule comprising a cylindrical member for the ferrule holding a front end of an optical fiber and a flange member fitted to a rear end portion thereof and including an engaging portion on a side of a rear end portion of the flange member, an optical connector plug comprising an urge spring provided on the side of the rear end portion of the flange member of the ferrule, and a plug housing directly holding the ferrule in a state of being urged to a side of a front end thereof in an axial direction by the urge spring by being engaged with the engaging portion of the ferrule and provided with a slit capable of inserting the optical fiber in a radius direction thereof at a portion of an outer periphery thereof over the axial direction and an optical connector adapter comprising a sleeve for optical connection inserted with the cylindrical members for the ferrules from sides of both ends thereof for bringing end faces of the cylindrical members for the ferrules into contact with each other to optically connect, and an adapter housing holding the sleeve for optical connection and having a shape for optically coupling the optical connector plugs, wherein the plug housing and the adapter housing are formed with engaging portions for engaging the plug housing and the adapter housing with each other, an outer periphery of the adapter housing is provided with a first mount engaging portion for attachably and detachably engaging with a mounting board or a mounting member fixed attachably and detachably to the mounting board to project from one face thereof. 
   According to a twentieth aspect of the invention, there is provided the optical connector according to the nineteenth aspect, wherein the plug housing is provided with a first rotation stopper portion engaged with the flange member for restricting the ferrule from moving in a rotating direction centering on an axis thereof and the adapter housing is provided with a second rotation stopper portion engaged with the flange member of the optical connector plug engaged with the adapter housing for restricting the ferrule from moving in the rotating direction centering on the axis of the ferrule. 
   According to a twenty-first aspect of the invention, there is provided the optical connector according to the twentieth aspect, wherein the flange member is provided with an outer periphery having a section in a rectangular shape and the ferrule is restricted from moving in the rotating direction by bringing the first rotation stopper portion into contact with two faces on one side of an outer peripheral face of the flange member opposed to each other and bringing the second rotation stopper portion into contact with two faces on other side of the outer peripheral face of the flange member opposed to each other. 
   According to a twenty-second aspect of the invention, there is provided the optical connector according to any one of the nineteenth through twenty-first aspects, wherein the plug housing and the adapter housing are provided with engagement restricting portions for restricting engaging positions in the rotating direction centering on axes thereof. 
   According to the invention, fabrication cost can be reduced and an integrating step can be simplified by reducing a number of parts of the optical connector comprising the optical connector plug and the optical connector adapter. Further, the reliability can be promoted without restricting a number of times of attachment and detachment of the optical connector plug and the optical connector adapter and without damaging a front end face of the optical fiber. Further, by providing the mounting member attachable and detachable to and from the optical connector adapter at the optical connector, it is not necessary to attach and detach the optical connector adapter and the optical connector plug on the mounting board and the mounting board can be downsized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a step of mounting an optical connector according to Embodiment 1 of the invention; 
       FIGS. 2A ,  2 B and  2 C are sectional views of the optical connector according to Embodiment 1; 
       FIGS. 3A ,  3 B and  3 C are plane views and a sectional view of an optical connector plug according to Embodiment 1 of the invention; 
       FIG. 4  is a plane view showing a step of integrating the optical connector plug according to Embodiment 1 of the invention; 
       FIGS. 5A ,  5 B and  5 C are a plane view and sectional views of an optical connector adapter according to Embodiment 1 of the invention; 
       FIGS. 6A and 6B  are plane views of the optical connector adapter according to Embodiment 1 of the invention; 
       FIG. 7  is a perspective view showing a step of mounting to laminate the optical connectors according to Embodiment 1 of the invention. 
       FIG. 8  is a perspective view showing a state of mounting to laminate the optical connector according to Embodiment 1 of the invention; 
       FIGS. 9A and 9B  are a plane view and a sectional view showing a state of mounting to laminate the optical connectors according to Embodiment 1 of the invention; 
       FIG. 10  is a perspective view showing a step of mounting to laminate optical connectors according to Embodiment 2 of the invention; 
       FIG. 11  is a perspective view showing a state of mounting to laminate the optical connectors according to Embodiment 2 of the invention; 
       FIG. 12  is a perspective view showing a step of integrating an optical connector adapter according to Embodiment 3 of the invention; 
       FIGS. 13A and 13B  are a plane view and a sectional view of the optical connector adapter according to Embodiment 3 of the invention; 
       FIG. 14  is a perspective view showing a state of connecting the optical connector and a plug releasing jig according to Embodiment 3 of the invention; 
       FIG. 15  is a perspective view showing a step of mounting to laminate the optical connectors according to Embodiment 3 of the invention; 
       FIG. 16  is a perspective view showing a state of mounting to laminate the optical connectors and a mount releasing jig according to Embodiment 3 of the invention; and 
       FIG. 17  is a perspective view showing a mounting step showing other example of a mounting member according to other embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The invention will be explained in details based on embodiments as follows. 
   Embodiment 1 
     FIG. 1  is a perspective view showing a step of mounting an optical connector according to Embodiment 1,  FIG. 2A  is a sectional view showing a step of connecting the optical connector,  FIG. 2B  is a sectional view showing a state of connecting the optical connector,  FIG. 2C  is a sectional view taken along a line  2 C— 2 C of  FIG. 2B ,  FIGS. 3A and 3B  are plane views of an optical connector plug,  FIG. 3C  is a sectional view taken along a line  3 C— 3 C of  FIG. 3A  and  FIG. 4  is a plane view showing a step of integrating the optical connector plug. 
   As illustrated, an optical connector jig  10  comprises an optical connector plug  20 , an optical connector adapter  50  and a mounting member  70 . 
   The optical connector plug  20  is constituted by a ferrule  21  for holding an optical fiber  1 , a plug housing  23  for directly holding the ferrule  21  movably in an axial direction in a predetermined range and provided with a first rotation stopper portion  22  for restricting movement in a rotating direction, and a biasing or urge spring  24  for urging the ferrule  21  to a side of a front end face in the axial direction thereof. 
   The ferrule  21  includes a ferrule cylindrical member  25  and a flange member  26  provided at a rear end portion of the ferrule cylindrical member  25 . 
   The ferrule cylindrical member  25  is provided with a cylindrical shape and includes an optical fiber inserting hole  27  capable of inserting the optical fiber  1  by penetrating in the axial direction at inside thereof. A rear end portion of the optical fiber inserting hole  27  is provided with a taper portion  27   a  an inner diameter of which is gradually increased to an opening side. By providing such a taper portion  27   a , when the optical fiber  1  is inserted into the optical fiber inserting hole  27 , a front end of the optical fiber  1  can be prevented from being chipped or broken by being brought into contact with an end face of the ferrule cylindrical member  25 . 
   Further, as a material of the ferrule cylindrical member  25 , for example, a ceramics material of zirconia or the like, a plastic material, a glass material of crystallized glass, borosilicate glass, quartz or the like, a metal material of stainless steel, nickel or the like can be pointed out. Further, an outer diameter of the ferrule cylindrical member  25  is set to 1.25 mm according to the embodiment. 
   The flange member  26  includes an optical fiber core line inserting hole  28  communicating with the optical fiber inserting hole  27  of the ferrule cylindrical member  25  and capable of inserting an optical fiber core line  2  having a coating at an outer periphery of the optical fiber  1 . A side of a front end portion of the optical fiber core line inserting hole  28  constitutes a fitting hole  28   a  formed by an inner diameter of a size substantially equivalent to an outer diameter of the ferrule cylindrical member  25  and fixedly attached to a rear end portion of the ferrule cylindrical member  25  by press-fitting or adherence. 
   Further, an outer periphery on a side of a front end portion of the flange member  26  includes a flange portion  29  projected in a rectangular shape over a circumferential direction. The flange portion  29  is engaged with a first rotation stopper portion  22  of the plug housing  23  to be mentioned later in details to restrict the movement of the ferrule  21  in the rotating direction centering on an axis thereof. 
   Further, an inserting portion  30  capable of inserting the urge spring  24  is extended on a rear die of the flange member  26 . The inserting portion  30  is constituted by a small diameter portion  31  an outer diameter of which is comparatively small on a side of a rear end portion thereof and a large diameter portion  32  an outer diameter of which is larger than that of the small diameter portion  31  on a side of the flange portion  29 . 
   An outer periphery of the large diameter portion  32  of the inserting portion  30  is provided with a projection for spring  33  engaging with the urge spring  24  by being projected over a circumferential direction thereof. 
   Further, an outer periphery of the small diameter portion  31  of the inserting portion  30  is provided with an engaging projection  34  an outer diameter of which is substantially equivalent to that of the large diameter portion  32  over a circumferential direction thereof and an inclined taper face  34   a  is constituted by a face on a side of a rear end portion of the engaging projection  34 . The taper face  34   a  provided at the engaging portion  34  is for inserting the inserting portion  30  of the flange member  26  into an engaging hole  36  of the plug housing  23 , mention later, while pushing to widen the engaging hole  36  in inserting thereinto. 
   Further, according to the embodiment, the flange member  26  is formed by a metal of stainless steel or the like. Further, the material and a method of fabricating the flange member  26  are not particularly limited thereto but, for example, the flange member  26  may integrally be molded to a rear end portion of the ferrule cylindrical member  25  by plastic. 
   Further, the urge spring  24  of a compression spring or the like is provided at an outer periphery of the inserting portion  30  of the flange member  26 . The urge spring  24  is engaged with the projection for spring  33  provided at the large diameter portion  32  of the inserting portion  30  to thereby temporarily prevent the urge spring  24  from being detached from the ferrule  21 . 
   Meanwhile, the plug housing  23  comprises, for example, plastic or the like and is provided with a ferrule holding hole  35  for holding the ferrule  21  and the urge spring  24  by penetrating in the axial direction. 
   A rear end portion of the ferrule holding hole  35  is provided with the engaging hole  36  having an inner diameter larger than the small diameter portion  31  of the flange member  26  and smaller than the engaging projection  34 . 
   By inserting the small diameter portion  31  of the inserting portion  30  of the flange member  26  into the engaging hole  36 , the ferrule  21  is held in the plug housing  23  movably in the axial direction by a predetermined amount. 
   That is, when the inserting portion  30  of the flange member  26  is inserted into the engaging hole  36 , the engaging projection  34  having an outer diameter larger than the engaging hole  36  pushes to widen the engaging hole  36  to elastically deform. When the engaging projection  34  has passed through the engaging hole  36 , the inner diameter of the engaging hole  36  recovers to the original inner diameter and the engaging projection  34  is brought into contact with the rear end face of the plug housing  23  at which the engaging hole  36  is opened to thereby hold the ferrule  21  to the plug housing  23  in a state in which movement thereof on a side of a front end face thereof is restricted. 
   Further, the urge spring  24  held at an outer peripheral face of the inserting portion  30  of the flange member  26  of the ferrule  21  urges the ferrule  21  to a front end side in the axial direction of the plug housing  23  by bringing one end thereof into contact with the flange portion  29  and bringing other end thereof into contact with an inner face thereof at which the engaging hole  36  is opened. 
   Further, as described above, the ferrule  21  urged to the front end side in the axial direction by the urge spring  24  is held in the state in which the ferrule  21  is urged to the front end face side by restricting the movement to the front end side in the axial direction by bringing the engaging projection  34  provided at the flange member  26  into contact with the rear end face of the plug housing  23  at which the engaging hole  36  is opened. 
   Further, since the engaging hole  36  of the plug housing  23  is pushed to widen to the engaging projection  34  when the inserting portion  30  of the flange member  26  is inserted thereinto, two intermittent opening portions  37  are provided at the rear end portion of the plug housing  23  at which the engaging hole  36  is provided over a circumferential direction at a surrounding of the engaging hole  36 . The surrounding of the engaging hole  36  is liable to be deformed elastically by the opening portions  37  and the inserting portion  30  of the flange member  26  is facilitated to be inserted into the engaging hole  36 . 
   Further, an outer peripheral face of the plug housing  23  is provided with a slit for optical fiber  38  for communicating the ferrule holding hole  35  to outside over the axial direction. The slit for optical fiber  38  is formed by a width larger than diameters of the optical fiber  1  and the optical fiber core line  2  held by the ferrule  21  and more or less smaller than the outer diameter of the small diameter portion  31  of the flange member  26 . 
   In integrating the optical connector plug  20 , the slit for optical fiber  38  simplifies the integration by attaching the plug housing plug  23  to the ferrule  21  holding the optical fiber  1  and the optical fiber core line  2  later without previously inserting the optical fiber  1  and the optical fiber core line  2  into the plug housing  23 . 
   By providing the slit for optical fiber  38  to the plug housing  23  in this way, it is not necessary to previously insert the optical fiber  1  into the plug housing  23  and therefore, the yield can be promoted by preventing the optical fiber  1  from being broken or damaged. 
   Further, the plug housing  23  is provided with a pair of claw portions  40  to interpose the ferrule  21  and provided with locking claws  39  at inner faces of front end portions thereof opposed to each other. 
   The claw portions  40  are for engaging the optical connector plug  20  and the optical connector adapter  50  by being engaged with an adapter housing  52  of the optical connector adapter  50  to be mentioned later in details. 
   Further, regions of the respective claw portions  40  opposed to the flange portion  29  are respectively provided with the first rotation stopper portions  22  provided to project to be brought into contact with respectives of the pair of faces of the outer peripheral face of the flange portion  29  opposed to each other. 
   The first rotation stopper portions  22  provided at respectives of the claw portions  40  are brought into contact with the pair of faces of the outer peripheral face of the flange portion  29  opposed to each other, that is, by interposing the flange portion  29  by the first rotation stopper portions  22  provided at the pair of claw portions  40 , movement of the ferrule  21  in the rotating direction centering on the axis is restricted relative to the plug housing  23 . 
   Further, the pair of claw portions  40  are formed at an interval by which inner faces thereof opposed to each other on a side of the rear end portion of the first rotation stopper portion  22  is not brought into contact with the flange portion  29  when the flange portion  29  is rotated. 
   That is, when the ferrule  21  of the optical connector plug  20  is pressed to the side of the rear end portion in the axial direction against urge force of the urge spring  24 , engagement between the first rotation stopper portion  22  and the flange portions  29  is disengaged and the ferrule  21  can be rotated relative to the plug housing  23 . Thereby, even after integrating the ferrule  21  and the plug housing  23 , positioning of the ferrule  21  in the rotating direction can be carried out by an eccentric direction of the optical fiber  1 , and insertion loss can be reduced by matching eccentric directions of the optical connector plugs  20  when the optical connector plugs  20  are opposedly connected by the optical connector adapter  50  to be mentioned later in details. 
   Further, according to the embodiment, a groove portion  41  having a predetermined depth is formed at a front end face of the flange portion  29  and the ferrule  21  may be pressed to the rear end portion side and rotate in a pressed state by a jig engaged with the groove portion  41 , although not particularly illustrated. 
   Further, as shown by  FIG. 1 , one of edge portions of one of the claw portions  40  is provided with an engagement restricting portion  42  to be engaged with an engagement restricting recess portion  63   a  of the optical connector adapter  50 , mentioned later. 
   By providing the engagement restricting portion  42  only at one of the edge portions of one of the claw portions  40 , the engagement restricting portion  42  can restrict a position of engaging the optical connector plug  20  to the optical connector adapter  50  in the rotating direction centering on the axis. That is, when the optical connector plug  20  is engaged with the optical connector adapter  50 , the optical connector plug  20  and the optical connector  50  can be engaged with each other always at the same rotating position. Thereby, when the optical connector plugs  20  are opposedly connected, eccentric directions of the optical fibers  1  are not different from each other and the insertion loss can be prevented from increasing. 
   As a method of integrating the optical connector plug  20 , first, the ferrule  21  is formed by fixing the flange member  26  to the rear end portion of the ferrule cylindrical member  25  by press-fitting. Next, by inserting the inserting portion  30  of the flange member  26  into the urge spring  24 , the urge spring  24  is engaged with the projection for spring  33  provided on the large diameter portion  32  and the urge spring  24  is tackedly fixed or integrally mounted to the outer peripheral face of the inserting portion  30 . 
   Next, the ferrule  21  integrally mounted or tackedly fixed with the urge spring  24  is adhered with the optical fiber  1  and the optical fiber core line  2  via a thermosetting type adhering agent. A front end face of the ferrule  21  holding the optical fiber  1  and the optical fiber core line  2  in this way is polished by a polishing apparatus or the like along with a front end face of the optical fiber  1 . 
   Thereafter, as shown by  FIG. 4 , the optical fiber core line  2  held by the ferrule  21  is inserted into the slit for optical fiber  38  of the plug housing  23  and the inserting portion  30  of the flange member  26  is inserted into the engaging hole  36  of the plug housing  23 . At this occasion, the inserting portion  30  is inserted into the engaging hole  36  while pressing to widen the engaging hole  36  by the engaging projection  34  and the engaging projection  34  is engaged with the engaging hole  36  in the state in which movement to the front end side is restricted. 
   Thereby, the optical connector plug  20  according to the embodiment can be constituted by holding the ferrule  21  movably in the axial direction by a predetermined amount in the ferrule holding hole  35  of the plug housing  23  in the state in which the ferrule  21  is urged to the front end side in the axial direction and the movement in the rotating direction centering on the axis is restricted by the first rotation stopper portions  22  of the claw portions  40 . 
   Since the optical connector plug  20  is constituted only by the ferrule  21 , the urge spring  24  and the plug housing  23  in this way, fabrication cost can be reduced by reducing a number of parts. Further, a procedure of integrating the optical connector plug  20  can be simplified since the urge spring  24  can tackedly be fixed to the rear end portion of the ferrule  21  and the plug housing  23  can be fixed to the ferrule  21  after fixing the optical fiber  1  to the ferrule  21 . 
   Further, a comparison of dimensions and numbers of parts between the optical connector plug  20  having such a constitution and the MU type optical connector plug (JIS C5983 F14 type optical connector) of the related art is shown in Table 1 shown below. 
   
     
       
             
             
             
             
           
             
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
                 
               embodiment 1 
               related art 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               total length (mm) 
               12.8 
               35 
             
             
                 
               width (mm) 
               4.5 
               6.6 
             
             
                 
               height (mm) 
               3.6 
               4.35 
             
             
                 
               number of parts 
               4 
               7 
             
             
                 
                 
             
           
        
       
     
   
   As shown by Table 1, a number of parts of the optical connector plug  20  of Embodiment 1 is smaller than that of the MU type optical connector plug of the related art and all of the total length, the width and the height can be downsized. Thereby, downsizing of the optical connector  10  using the optical connector plug  20  can be achieved and when the optical connector  10  is mounted to a mounting board, high density formation can be achieved. 
   Further, the optical connector  10  using the optical connector plug  20  optically connects the optical fiber core lines  2  provided with coatings at outer peripheries of the optical fibers  1  above a mounting board  100  and therefore, it is not necessary to use an optical fiber cable provided with a tension member and a coating at the outer periphery of the optical fiber core line  2  and downsizing can be carried out also thereby. 
   Next, the optical connector adapter  50  of the optical connector  10  will be explained in details. 
     FIG. 5A  is a plane view from a side of a bottom face of the optical connector adapter,  FIG. 5B  is a sectional view taken along a line  5 B— 5 B of  FIG. 5A ,  FIG. 5C  is a sectional view taken along a line  5 C— 5 C of  FIG. 5A  and  FIGS. 6A and 6B  are plane views from a side of an end face and a side of an upper face of the optical connector adapter. 
   As shown by  FIGS. 5A ,  5 B and  5 C, the optical connector adapter  50  is constituted by a sleeve for optical connection  51  inserted with the front end portion of the ferrule cylindrical member  25  and the adapter housing  52  including the sleeve for optical connection  51 . 
   The sleeve for optical connection  51  is provided with a cylindrical shape and includes a ferrule inserting hole  53  provided by penetrating in an axial direction thereof and a streak of slit  53   a  provided from one end side to other end side in the longitudinal direction. Further, the ferrule inserting hole  53  is formed by an inner diameter more or less smaller than an outer diameter of the cylindrical member for ferrule  25 . 
   Optical connection is carried out by respectively inserting front end portions of the cylindrical members for ferrule  25  from openings on both sides of the ferrule inserting hole  53  of the sleeve for optical connection  51 . At this occasion, the sleeve for optical connection  51  is elastically deformed in a direction of expanding the slit  53   a  by inserting the front end portions of the cylindrical members for ferrule  25  and therefore, the front end portions of the cylindrical members for ferrule  25  can opposedly be connected by being brought into close contact with the inner face of the ferrule inserting hole  53  to hold. 
   Furthers as a material of the sleeve for optical connection  51 , for example, a ceramic material of zirconia or the like or a metal material of copper alloy or the like can be pointed out. 
   Further, the adapter housing  52  is formed by, for example, integrally molding a resin of plastic or the like and is provided with a through hole  54  for holding the sleeve for optical connection  51  by penetrating in the axial direction. 
   The cylindrical members for ferrule  25  are inserted from the both end sides of the through hole  54  to be inserted into the sleeve for optical connection  51  held in the through hole  54 . 
   That is, the through hole  54  is provided with a sleeve holding portion  55  having a diameter more or less larger than the outer diameter of the sleeve for optical connection  51  substantially on a central side thereof and communication holes  56  each having an inner diameter substantially equivalent to the outer diameter of the cylindrical member for ferrule  25  on both end sides of the sleeve holding portion  55  and a stepped difference portion  57  is provided by a difference between inner diameters of these. 
   By bringing both end faces of the sleeves for optical connection  51  in contact with the stepped difference portions  57 , the sleeve for optical connection  51  is held by the sleeve holding portion  55  in a state in which movement thereof in the axial direction is restricted. 
   Further, the adapter housing  52  is provided with a sleeve inserting hole  58  formed by a size equivalent to that of the sleeve holding portion  55  for communicating the sleeve holding portion  55  to outside and the sleeve for optical connection  51  is inserted into the sleeve holding portion  55  from the sleeve inserting hole  58 . 
   Further, inner side faces of the sleeve inserting hole  58  opposed to each other are provided with two pairs of projections for sleeve  59  to be opposed to each other which are provided to project such that widths thereof are narrower than that of the sleeve holding portion  55 . The projection for sleeve  59  is provided in a taper shape such that an amount of projection thereof is reduced to an opening side of the sleeve inserting hole  58 . The sleeve for optical connection  51  inserted from the sleeve inserting hole  58  is inserted into the sleeve holding portion  55  by pressing to widen the two pairs or projections for sleeve  59  and the projections for sleeve  59  are brought into contact with an outer peripheral face of the inserted sleeve for optical connection  51 , thereby, the sleeve for optical connection  51  is held in the sleeve holding portion  55  in a state in which movement in a radius direction thereof is restricted. 
   Further, as shown by  FIG. 1  and  FIGS. 2A and 2B , at the peripheries of the both end portions of the adapter housing  52 , engaging recess portions  60  for engaging with the pair of claw portions  40  of the optical connector plug  20  are provided at respective opposed faces thereof. 
   The engaging recess portions  60  are formed from both end faces of the adapter housing  52  such that lengths and thickness thereof are substantially equivalent to those of the claw portions  40  and a bottom face of the engaging recess portion  60  is provided with an engaging projection portion  61  projected to a side of an opening face of the engaging recess portion  60 . A taper face  61   a  is formed at a face of the engaging projection portion  61  on a side thereof inserted with the claw portion  40 . When the claw portions  40  are inserted into the engagement recess portions  60  from sides of end faces thereof, an interval between the pair of claw portions  40  is pressed to widen by elastically deforming the claw portions  40  by bringing the locking claws  39  into contact with the taper faces  61   a  of the engaging projection portions  61  and the locking claws  39  passing the engaging projection portions  61  are engaged with the engaging projection portions  61  to thereby engage the optical connector plug  20  and the optical connector adapter  50 . 
   Further, both end faces of the adapter housing  52  are provided with second rotation stopper portions  62  for restricting movement in the rotating direction of the ferrule  21  centering on the axis by being engaged with the flange portions  29  of the flange member  26 . 
   The second rotation stopper portions  62  are formed as a communicating hole in a rectangular shape communicating with the communication hole  56  of the through hole  54  and having a size of inserting the flange portions  29  of the flange member  26  and notch portions  63  are formed on sides thereof of the engaging recess portions  60  inserted with the flange portions  29  of the second rotation stopper portion  62 . That is, the movement in the rotating direction centering on the axis of the ferrule  21  is restricted by bringing the first rotation stopper portions  22  provided at the claw portions  40  into contact with ones of the outer peripheral faces of the flange portions  29  opposed to each other and bringing the second rotation stopper portions  62  into others of the outer peripheral faces of the flange portions  29  opposed to each other. 
   That is, the movement in the rotating direction centering on the axis of the ferrule  21  is restricted by engaging the optical connector plug  20  and the optical connector adapter  50  by the claw portions  40  and the engaging recess portions  60 . 
   As shown by  FIG. 1  and  FIGS. 6A and 6B , one of the edge portions of one of the notch portions  63  is provided with the engagement restricting recess portion  63   a  to be inserted with the engagement restricting portion  42  of the optical connector plug  20 . 
   The engaging restricting recess portion  63   a  restricts an engaging position in the rotating direction centering on the axis of the optical connector plug  20  by being provided at one of the edge portions of one of the notch portions  63 . 
   An explanation will be given here of optical connection of the optical connector plugs  20 . 
   As shown by  FIG. 2A , one of the optical connector plugs  20  is inserted into one end side of the optical connector adapter  50  for engagement therewith. 
   More specifically, the claw portions  40  of the optical connector plug  20  are engaged with the engaging recess portions  60  of the optical connector adapter  50 . At this occasion, the optical connector plug  20  is provided with the engagement restricting portion  42  only at one of the edge portions of the one of the claw portions  40  and, therefore, the claw portions  40  are engaged with the engagement recess portions  60  such that the engagement restricting portion  42  is inserted into the engagement restricting recess portion  63   a  of the optical connector adapter  50 . 
   Thereby, the engaging position in the rotating direction of the optical connector plug  20  can be positioned relative to the optical connector adapter  50 . 
   Further, the ferrule  21  held between the optical connector adapter  50  and the optical connector plug  20  which are engaged is held in a state in which movement in the rotating direction centering on the axis is restricted by the first rotation stopper portions  22  and the second rotation stopper portions  62 . 
   The ferrule  21  is urged to be held in a state in which movement on the front end side is restricted by bringing the engaging projection  34  of the inserting portion into contact with the engaging hole  36  and such that movement thereof to the rear end side by pressing can be carried out. 
   Next, as shown by  FIG. 2B , another of the optical connector plugs  20  is inserted into the other end side of the optical connector adapter  50  for engagement therewith. 
   Furthermore, the engagement between the optical connector adapter  50  and the optical connector plug  20  is carried out by engaging the claw portions  40  and the engagement recess portions  60  similar to the one optical connector plug  20  and the optical connector adapter  50 , as described above. 
   When the other optical connector plug  20  is engaged with the optical connector adapter  50  in this way, by bringing the front end faces of the ferrules  21  into contact with each other, the ferrules  21  are moved to rear end portion sides against the urge or biasing force of the urge springs  24 . 
   In this way, optical connection can be carried out by bringing the ferrules  21  into contact with each other in the state in which the front end faces of the ferrules  21  urged to the front end portion sides by the urge force of the urge springs  24  are pressed by predetermined pressure. 
   In this way, the optical connector plug  20  and the optical connector adapter  50  can be readily attached to each other and detached from each other by optically connecting the optical connector plugs  20  via the optical connector adapter  50 . 
   Further, the movement of the ferrule  21  in the rotating direction is restricted by the second rotation stopper portion  62  and therefore, the ferrule  21  is not inserted into the sleeve for optical connection  51  in a skewed direction and the front end face of the ferrule  21  is difficult to be damaged. Thereby, not only the insertion loss in optical connection can be reduced but also the reliability can be promoted. 
   Further, in disengaging the engagement between the optical connector plug  20  and the optical connector adapter  50 , the engagement may be disengaged by widening the claw portions  40  of the optical connector plug  20  by a jig although not particularly illustrated. 
   Further, one face of the adapter housing  52  is provided with a mount engaging portion  64  for engaging with the mounting member  70 . 
   According to the embodiment, the mount engaging portions  64  are provided as projections projected at four locations at a face of the adapter housing  52  on the side of the sleeve inserting hole  58  and an engaging groove  64   a  is formed on the inner face side of the mount engaging portion  64 . 
   Further, as shown by  FIGS. 6A and 6B , other face of the adapter housing  52  is provided with a projection for lamination  65  and an engaging portion for lamination  66  having shapes equivalent to those of a projection for adapter  76  and an engaging portion for adapter  77  of the mounting member  70  used in attachment and detachment to and from the adapter housing  52  which will be described later in details. 
   The projection for lamination  65  and the engaging portion for lamination  66  are for laminating a plurality of the optical connectors  10  by engaging with the adapter housing of other optical connector adapter attachably and detachably thereto and therefrom although details thereof will be described later. 
   Since the optical connector adapter  50  is constituted by the sleeve for optical connection  51  and the integrally molded adapter housing  52 , the cost can be reduced by reducing the number of parts. 
   A comparison of dimensions and numbers of parts between the optical connector adapter  50  constituted in this way and the MU type optical connector adapter (JIS C5983 F14 type optical connector) of the related art is shown in Table 2 shown below. 
   
     
       
             
             
             
             
           
             
             
             
             
           
         
             
                 
               TABLE 2 
             
             
                 
                 
             
             
                 
                 
               embodiment 1 
               related art 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               total length (mm) 
               13.6 
               26 
             
             
                 
               width (mm) 
               4.5 
               10.4 
             
             
                 
               height (mm) 
               4.0 
               7.5 
             
             
                 
               number of parts 
               2 
               5 
             
             
                 
                 
             
           
        
       
     
   
   As shown by Table 2, a number of parts of the optical connector adapter  50  according to the embodiment is smaller than that of the MU type optical connector adapter of the related art and all of the total length, the width and height can be downsized. Thereby, downsizing of the optical connector  10  using the optical connector adapter  50  can be downsized and the high density formation can be achieved when the optical connector  10  is mounted to a mounting board. 
   Next, the mounting member  70  will be described in details. 
   As shown by  FIG. 1  and  FIG. 2C , the mounting member  70  is constituted by fixing portions  71  of bent both end portions having a channel-like shape formed by bending both end portions of a member in a shape of a flat plate and a base seat portion  72  at a region between the two mixing portions  71 . 
   The fixing portion  71  is inserted into a fixing hole  101  provided to penetrate the mounting board  100  to hold and a front end portion thereof is constituted by a stepped difference portion  73  a width of which is wider than that of the side of the base seat portion  72  and wider than an inner diameter of the fixing hole  101 . 
   Further, a front end face of the fixing portion  71  is formed by a taper face  74  to facilitate to be inserted into the fixing hole  101  and a notch portion  75  notched by a predetermined amount in a longitudinal from the front end is provided at substantially a central portion thereof in the width direction. 
   When the fixing portion  71  is inserted into the fixing hole  101  of the mounting board  100 , the fixing portion  71  is inserted into the fixing hole  101  by bringing an edge portion of the fixing portion  71  into contact with the taper face  74  of the fixing portion  71  and elastically deforming the fixing portion  71  to narrow the width of the notch portion  75 . 
   Further, the inserted fixing portion  71  is held by preventing the mounting member  70  from drawing from the fixing hole  101  by bringing the stepped difference portion  73  into contact with an opening edge portion of the fixing hole  101 . 
   Further, the base seat portion  72  of the mounting member  70  is provided with a pair of projections for adapter  76  projected into the sleeve inserting hole  58  of the adapter housing  52  by being projected to a side opposed to the fixing portion  71  substantially at a central portion thereof and four adapter engaging portions  77  engaged with respectives of the engaging grooves  64   a  of the four mount engaging portions  64  of the adapter housing  52  at edge portions in the width direction of the base seat portion  72 . 
   The projections for adapter  76  are provided to project to sides of both ends in the longitudinal direction of the sleeve inserting hole  58  of the adapter housing  52  and by bringing the projections for adapter  76  into contact with the both ends in the longitudinal direction of the sleeve inserting hole  58 , movement of the adapter housing  52  in the axial direction of the optical fiber  1  is restricted relative to the mounting member  70 . 
   Further, the adapter engaging portion  77  is formed to be projected to be inclined to the width to the width direction of the base seat portion  72  and by engaging the adapter engaging portion  77  to the engaging groove  64   a  of the mount engaging portion  64 , the adapter engaging portion  77  is held by restricting movement of the adapter housing  52  in the width direction and the attaching and detaching direction relative to the mounting member  70  of the adapter housing  52 . 
   That is, when a face of the adapter housing  52  provided with the sleeve inserting hole  58  is brought into contact with the base seat portion  72  of the mounting member  70 , the adapter engaging portion  77  of the mounting member  70  is engaged with the mount engaging portion  64  of the adapter housing  52 , the movement in the width direction and the attaching and detaching direction is restricted, the pair of projections for adapter  76  provided at the base seat portion  72  are projected into the sleeve inserting hole  58  of the adapter housing  52 , thereby, the adapter housing  52  is held by restricting the movement in the longitudinal direction. 
   Further, since the inner faces of the engaging grooves  64   a  of the mount engaging portions  64  are formed by the inclined faces and the adapter engaging portions  77  are formed to be inclined, the mounting member  70  and the optical connector adapter  50  can be attached and detached to and from each other by being pressed or drawn by predetermined force. 
   Such a mounting member  70  can be formed by, for example, metal pressing. 
   As a method of integrating the optical connector constituted by the optical connector plug, the optical connector adapter and the mounting member, first, the mounting member  70  is fixed to the mounting board  100 . Next, the optical connector plugs  20  are fixed to the both sides of the optical connector adapter  50  to thereby optically connect the optical connector plugs  20 . Thereafter, by fixing the optical connector adapter  50  fixed with the optical connector plugs  20  to the mounting member  70 , the optical connector  10  optically connecting the optical fibers  1  can be mounted to the mounting board  100 . 
   Further, in order to disengage the optical connector plug of the optical connector mounted to the mounting board  100  in this way, the optical connector plug  20  may be disengaged from the optical connector adapter  50  after disengaging the optical connector adapter  50  fixed with the optical connector plugs  20  from the mounting member  70 . 
   By making the mounting member attachable and detachable to and from the optical connector adapter  50 , the optical connector adapter  50  can be attached and detached thereto and therefrom after fixing the mounting member  70  to the mounting board  100  and therefore, it is not necessary to engage the optical connector adapter  50  and the optical connector plug  20  on the mounting board  100  and it is not necessary to provide a space for attaching and detaching the optical connector adapter  50  to and from the optical connector plug  20  at the mounting board  100 . Thereby, not only the mounting board  100  can be downsized but also mounting of the optical connector  10  can easily be carried out. 
   Here,  FIG. 7  is a perspective view showing a step of mounting to laminate optical connectors,  FIG. 8  is a perspective view showing a state of mounting to laminate optical connectors and  FIGS. 9A and 9B  are a plane view showing a state of mounting to laminate optical connectors and a sectional view taken along a line  9 B— 9 B thereof. 
   The projection for lamination  65  and the engaging portion for lamination  66  are provided at a face of the adapter housing  52  of the optical connector adapter  50  on a side opposed to the mount engaging portion  64 . 
   As shown by  FIGS. 5A ,  5 B and  5 C and  FIGS. 6A and 6B , the projection for lamination  65  is provided with a shape equivalent to that of the projection for adapter  76  of the mounting member  70  and projected into the sleeve inserting hole  58  of other of the optical connector adapter  50  to thereby prevent the other optical connector adapter  50  from moving in the longitudinal direction relative to the optical connector adapter  50 . 
   Further, the engaging portion for lamination  66  is formed to project by forming the groove along an outer peripheral edge portion to be engaged with the mount engaging portion  64  of the other optical connector adapter  50 . By engaging the engaging portion for lamination  66  with the mount engaging portion  64  of the other optical connector adapter  50 , the other optical connector adapter is held attachably and detachably to and from the optical connector adapter  50 . 
   By providing the projection for lamination  65  and the engaging portion for lamination  66  for engaging with the optical connector adapter  50  at the face of the optical connector adapter  50  on the side opposed to the mount engaging portion  64  in this way, a plurality of the optical connector adapters  50  can be laminated, it is not necessary to align a plurality of the optical connectors  10  on the mounting board  100  in the face direction and downsizing can be achieved by narrowing the mounting area of the mounting board  100 . 
   Here, a comparison of the total lengths and mounting densities of the optical connector  10  according to Embodiment 1 and the MU type optical connector plug (JIS C5983 F14 type optical connector) of the related art is shown in Table 3, shown below. Further, the mounting density shown in Table 3, shown below, is constituted by fixing the optical connector plugs  20  on the both sides of the optical connector adapter and is a relative value by constituting a reference by the MU type optical connector of the related art. 
   
     
       
             
             
             
             
           
         
             
                 
               TABLE 3 
             
             
                 
                 
             
             
                 
                 
                 
               related art 
             
             
                 
                 
               embodiment 1 
               (nonpatent literature 1) 
             
             
                 
                 
             
           
           
             
                 
               total length 
               ⅓ 
               1 
             
             
                 
               mounting density 
               2 or more 
               1 
             
             
                 
               (width direction) 
             
             
                 
               mounting density 
               2 
               1 
             
             
                 
               (height direction) 
             
             
                 
                 
             
           
        
       
     
   
   As shown by Table 3, according to the optical connector  10  of the embodiment, the mounting density twice or more as much as that of the MU type optical connector plug of the related art in the width direction and the mounting density twice as much as that of the MU type optical connector plug of the related art in the height direction can be realized. Further, since the total length of the optical connector  10  of the embodiment can be made ⅓ of that of the MU type optical connector of related art, also the mounting density in the longitudinal direction of the embodiment can be three times as much as that of the MU type optical connector of the related art. Further, in the longitudinal direction, engagement and disengagement of the optical connector plug  20  and the optical-connector adapter  50  can be carried out by a narrow area and therefore, a substantial mounting density of the embodiment can be made three times as much as that of the MU type optical connector of the related art. 
   Embodiment 2 
     FIG. 10  is a perspective view showing a step of mounting to laminate optical connectors according to Embodiment 2 and  FIG. 11  is a perspective showing a state of mounting to laminate optical connecters according to Embodiment 2. Further, members similar to those of Embodiment 1, mentioned above, are attached with the same notations and duplicated explanation thereof will be omitted. 
   As shown by  FIG. 10  and  FIG. 11 , an optical connector  10 A is provided with the optical connector plug  20 , an optical connector adapter  50 A and a mounting member  70 A. 
   The mounting member  70 A comprises the bent portion  71  and a base seat portion  72 A and adapter engaging portions  77 A are provided at edge portions on both sides in a width direction of the base seat portion  72 A. 
   The adapter engaging portions  77 A are formed to bend to project to a side opposed to the bent portion  71  and formed such that front end portions thereof are bent to both sides in the width direction to constitute directions the same as directions of the face of the base seat portion  72 A. 
   An adapter housing  52 A of the optical connector adapter  50 A engaged with the mounting member  70 A is provided with a mount engaging portion  64 A projected to a side of the sleeve inserting hole  58 . 
   The mount engaging portion  64 A is provided to project to the side of the mounting member  70 A and a front end portion thereof is formed in a shape projected to an inner side. 
   The optical connector adapter  50 A and the mounting member  70 A can engage the mount engaging portion  64 A and the adapter engaging portion  77 A by sliding to move in a state in which a face of the adapter housing  52 A on the side of the sleeve inserting hole  58  is brought into contact with the base seat portion  72 A of the mounting member  70 A. 
   Further, a face of the mount engaging portion  64 A of the adapter housing  52 A on a side opposed to the mount engaging portion  64 A is provided with a lamination engaging portion  66 A in a groove-like shape to be engaged with the mount engaging portion  64 A of other of the optical connector adapter  50 A. 
   The optical connectors  10 A can be mounted to laminate on the mounting board  100  by attachably and detachably laminating a plurality of the optical connector adapters  50 A by the lamination engaging portions  66 A. 
   In this way, according to the embodiment, the optical connector adapter  50 A is moved to slide to engage with the mounting member  70 A to thereby make the optical connector adapter  50 A and the mounting member  70 A attachable and detachable to and from each other and thereby, similar to Embodiment 1, mentioned above, attachment and detachment of the optical connector adapter  50 A to and from the optical connector plug  20 A can be facilitated to execute and the mounting board  100  can be downsized. 
   Embodiment 3 
     FIG. 12  is a perspective view showing a step of integrating an optical connector adapter according to Embodiment 3 and  FIGS. 13A and 13B  are a plane view of the optical connector adapter and a sectional view taken along a line  13 B— 13 B thereof. Further, members similar to those of Embodiments 1 and 2, mentioned above, are attached with the same notations and a duplicated explanation thereof will be omitted. 
   As shown by  FIG. 12  and  FIGS. 13A and 13B , an optical connector adapter  50 B of the embodiment is provided with the sleeve for optical connection  51  inserted with a front end portion of a cylindrical member for ferrule and an adapter housing  52 B including the sleeve for optical connection  51  and an adapter housing  52 B and is constituted by a housing main body  110  provided with a sleeve inserting hole  58 B inserted with the sleeve for optical connection  51  and opened at one face thereof and a lid member  120  fitted to the sleeve inserting hole  58 B of the housing main body  110 . 
   The housing main body  110  is formed by, for example, integrally molding a resin of plastic or the like and is provided with the through hole  54  penetrated in the axial direction similar to Embodiment 1, as described above. 
   The through hole  54  includes a sleeve holding portion (not illustrated) holding the sleeve for optical connection  51  substantially on the central side and the through holes  56  inserted with the cylindrical members for ferrule on sides of both ends of the sleeve holding portion and a stepped difference portion (not illustrated) is provided by a difference between inner diameters of the sleeve holding portion and the through hole  56 . 
   Further, the housing main body  110  is provided with the sleeve inserting hole  58 B formed by a size substantially equivalent to the sleeve holding hole for communicating the sleeve holding hole and outside at the one face. A portion of an opening side of the sleeve inserting hole  58 B constitutes a fitting portion  111  larger than the sleeve holding portion such that the lid member  120  is fitted thereto and the fitted lid member  120  is not inserted up to the sleeve holding portion and there is provided a stepped difference portion for lid  112  brought into contact with the lid member  120  by the fitting portion  111  for restricting-movement of the sleeve holding portion of the lid member  120  to the sleeve holding portion. 
   Further, a pair of fixing recess portions  113  for engaging with fixing projections  122  of the lid member  120  at side faces thereof opposed to each other are provided at inner faces of the fitting portions  111  of the housing member  110 . 
   Further, two side faces of the housing main body  110  are provided with recess portions for insertion  114  into which mount engaging portions  64 B of the lid member  120  are inserted to guide when the lid member  120  is fitted to the fitting portion  111  which will be described later in details. 
   Further, the housing main body  110  is provided with a plug releasing insertion hole  115  to be inserted with a plug releasing jig, decribed later in more detail, at a region in correspondence with the locking claw  39  of the claw portion  40  of the optical connector plug  20  when the housing main body  110  is engaged with the optical connector plug  20  of Embodiment 1, as described above. 
   The plug releasing insertion hole  115  is opened to the stepped difference portion for lid  112  provided by the fitting portion  111  and is not closed when the lid member  120  is fitted to the fitting portion  111 . 
   Meanwhile, the lid member  120  is formed by, for example, integrally molding a resin of plastic or the like similar to the housing main body  110  and is constituted by a lid portion  121  fitted to the fitting portion  111  and brought into contact with the stepped difference portion for lid  112  and is constituted by the mount engaging portion  64 B projected from a side of the face opposed to a face provided with the fitting portion  111  of the housing main body  110 . 
   The lid portion  121  is provided with fixing projection portions  122  respectively projected into the pair of fixing recess portions  113  when the lid portion  121  is fitted to the fitting portion  111  of the housing main body  110 . 
   Further, the lid portion  121  is provided with a projection for lamination  65 B engaged with the mount engaging portion  64 B of other of the optical connector adapter  50 B. 
   The lid portion  121  is provided to project with the pair of mount engaging portions  64 B integrally formed therewith from a bottom face side. The mount engaging portion  64 B is provided to project by a predetermined amount from a face opposed to a face of the housing main body  110  provided with the fitting portion  111  by being inserted into the insertion recess portion  114  of the housing main body  110  when the lid member  120  is fitted to the fitting portion  111  of the housing main body  110 . 
   At inner faces of front end portions of the pair of mount engaging portions  64 B opposed to each other, there are provided mount engaging projections  113  to be engaged with a mounting member or other of the adapter holding  52 B. 
   Further, the lid portion  121  is provided with jig inserting holes  124  for inserting a mount engagement releasing jig having a shape of a pin for releasing engagement between the mount engaging portion  64 B and the mounting member or other of the adapter housing  52 B, described later in details in correspondence with respectives of the pair of mount engaging portions  64 B. 
   The jig inserting hole  124  is arranged on the inner face side of each of the mount engaging portions  64 B and the inner face of the mount engaging portion  64 B is provided with a recess portion for inserting jig  125  to be inserted with mount engagement releasing jig continuous to the inserting hole  123 . 
   A taper face  125   a  is constituted on a side of a front end portion of the mount engaging portion  64 B of the jig inserting recess portion  125  of the mount engaging portion  64 B and when the mount engagement releasing jig is inserted into the jig inserting hole  124  of the lid member  120 , a front end of the mount engagement releasing jig is brought into contact with the taper face  125   a  of the jig insertion recess portion  125 , the taper face  125   a  is pushed to widen by pushing the mount engagement releasing jig further and the mount engaging portions  64 B are elastically deformed in directions remote from each other. 
   Further, the recess portion for insertion  114  of the housing main body  110  to be fitted with the lid member  120  is provided with a jig guiding recess portion  115  to be inserted with a front end of the mount engagement releasing jig inserted into the jig inserting hole  124  and the mount engagement releasing jig is guided by the jig guiding recess portion  115 . 
   According to the optical connector adapter  50 B having such a constitution, since the mount engaging portion  64 B provided at the lid member  120  fitted with one face of the housing main body  110  is provided to project from other face of the housing member  110 , the mount engaging portion  64 B can be prolonged to facilitate elastic deformation. Therefore, the mount engaging portion  64 B can be prevented from being cracked or broken in engaging and disengaging the optical connector adapter  50 B to and from the mounting member or other of the optical connector adapter  50 B by the mount engaging portion  64 . 
   Here, the optical connector  10 B using the optical connector adapter  50 B will be explained. Further,  FIG. 14  is a perspective view showing a state of connecting the optical connector according to Embodiment 3 and the plug releasing jig. 
   Here, the optical connector plug  20  used in the optical connector  10 B along with the optical connector adapter  50 B of the embodiment is similar to that of Embodiment 1, mentioned above, and therefore, a duplicated explanation thereof will be omitted. 
   As shown by  FIG. 14 , the optical connector plug  20  and the optical connector adapter  50 B of the optical connector  10 B are engaged with each other similar to Embodiment 1 described above. 
   Further, the engagement is released by the adapter releasing jig  200 . 
   Here, the adapter releasing jig  200  is provided with releasing portions  201  comprising a shape of a pair of flat plates inserted into the plug releasing inserting holes  115  of the adapter housing  52 B at a front end thereof and a front end of the releasing portion  201  constitutes a taper portion  202  a thickness of which is gradually reduced. 
   When the releasing portions  201  having the taper portions  202  are inserted into the plug releasing inserting holes  115 , the releasing portions  201  are interposed between the locking claws  39  and the adapter housing  52 B while pushing to widen to elastically deform the claw portions  40  of the optical connector plug  20  to thereby release engagement between the optical connector plug  20  and the optical connector adapter  50 B. 
   Further, an explanation will be given of mounting the optical connector  10 B to a mounting board. 
     FIG. 15  is a perspective view showing a step of mounting to laminate the optical connector according to Embodiment 3 and  FIG. 16  is a perspective view showing a state of mounting to laminate the optical connector according to Embodiment 3 and the mounting releasing jig. Further, members similar to those of Embodiments 1 and 2, mentioned above, are attached with the same notations and a duplicated explanation thereof will be omitted. 
   As shown by  FIG. 15 , a mounting member  70 B to be mounted on the mounting board  100  is constituted by fixing portions  71  at the two bent end portions and a base seat portion  72 B at a region between the two fixing portions  71 . 
   The base seat portion  72 B is provided with an adapter engaging portion  77 B with which the mount engaging portion  64 B of the optical connector adapter  50 B is engaged and projections for adapter  76 B on both sides of the adapter engaging portion  77 B. 
   By bringing the projections for adapter  76 B into contact with the mount engaging portions  64 B engaged with the adapter engaging portion  77 B, the optical connector  10 B is restricted from moving in the axial direction of the optical fiber  1  relative to the mounting member  70 B. 
   The optical connector  10 B is fixed attachably and detachably to and from the mounting member  70 B via the mount engaging portions  64 B. 
   Further, other of the optical connector  10 B is laminated on the optical connector  10 B fixed to the mounting member  70 B via the mount engaging portions  64 B. 
   In details, the optical connector  10 B is laminated with other of the optical connector  10 B by engaging the mount engaging portions  64 B of the other optical connector  10 B with the projections for lamination  65 B provided at the lid member  120  of the optical connector  10 B on the mounting member  70 B. 
   Further, engagement of the laminated optical connectors  10 B and engagement of the optical connector  10 B with the mounting member  70 B can be released by the mount releasing jig  210  shown in  FIG. 16 . 
   The mount releasing jig  210  is provided with the pair of releasing portions  211  each having a shape of a pin inserted into the jig inserting holes  114  of the adapter housing  52 B at a front end thereof. 
   When the releasing portions  211  of the mount releasing jig  210  are inserted into the jig inserting holes  124 , as described above, the front ends of the releasing portions  210  push to open to elastically deform the mount engaging portions  64 B and engagement of the optical connectors  10 B or the optical connector  10 B and the mounting member  70 B is released. 
   In this way, the optical connector  10 B of the embodiment can be downsized by reducing a number of parts and since the number of parts is reduced, releasing of the engagement between the optical connector plug  20  and the optical connector adapter  50 B as well as releasing of engagement between the optical connectors  10 B or between the optical connector  10 B and the mounting member  70 B can easily be carried out by using the adapter releasing jig  200  or the mount releasing jig  210 . Further, according to the optical connector  10 B mounted to the mounting board  100 , releasing of engagement between the optical connector plug  20  and the optical connector adapter  50 B as well as releasing of engagement between the optical connectors  10 B or the optical connector  10 B and the mounting member  70 B are not carried out so frequently and therefore, the releasing is not troublesome even by the adapter releasing jig  200  or the mount releasing jig  210 . 
   Although the invention has been explained by Embodiments 1 through 3 as described above, the optical connector of the invention is not limited to the above-described. 
   For example, according to Embodiments 1 through 3, mentioned above, the shape of the flange portion  29  and the shapes of the first rotation stopper portion  22  and the second rotation stopper portion  62  for restricting movement of the ferrule  21  in the rotating direction centering on the axis are not limited to those of Embodiments 1 through 3, mentioned above, for example, there may be constructed a constitution in which the flange portion is formed in a shape of a circular disk and provided with key grooves over the axial direction at four locations uniformly over the circumferential direction and the first rotation stopper portion and the second rotation stopper portion may be constituted by projections projected into the key grooves. 
   Moreover, so far as movement of the ferrule in the rotating direction can be restricted by the optical connector plug and the optical connector adapter, an effect similar to those of Embodiments 1 through 3, as described above, can be achieved. 
   Further, although according to Embodiments 1 through 3, mentioned above, the mounting members  70  through  70 B are provided with the bent portions  71  for engaging with the fixing holes  101  of the mounting board  100  and the mounting members  70 ,  70 A through  70 B are mounted on the mounting board  100 , a method of mounting the mounting members  70 ,  70 A through  70 B on the mounting board  100  is not particularly limited thereto. 
   Here, other example of a mounting member is shown in  FIG. 17 . Further,  FIG. 17  is a perspective view showing a mounting step showing a modified example of the mounting member of Embodiment 1. 
   As shown by  FIG. 17 , a mounting member  70 C is not provided with a bent portion and is constituted only by a base sheet portion  72 C. 
   Fixing projections  72 A projected in a face direction are provided on sides of both ends in the longitudinal direction of the base seat portion  72 C and sides of bottom faces of the fixing projections  72   a  are bonded onto the mounting board  100 . 
   Further, bonding of the fixing projection  72   a  and the mounting board  100  is not particularly limited but, for example, bonding can be carried out by adhesion via an adhering agent, brazing or soldering. 
   Also the mounting member  70 C can be formed by metal pressing. 
   Further, although according to Embodiments 1 through 3, mentioned above, the optical connectors  10  through  10 B are fixed attachably and detachably to and from the mounting board  100  via the mounting members  70  through  70 B fixed thereto attachably and detachably, Embodiments 1 through 3 are not particularly limited thereto but, for example, in the case of the optical connector  10 B having the mount engaging portions  64 B according to Embodiment 3, the optical connector  10 B may directly be fixed onto the mounting board  100 . Even by such a constitution, the optical connector  10 B can be fixed attachably and detachably to and from the mounting board  100  and cost can be reduced and downsizing can be achieved by reducing the number of parts of the optical connector, particularly, the number of parts of the optical connector adapter. 
   As has been explained above, according to the invention, respectives of the optical connector plug, the optical connector adapter and the mounting member are constituted by reducing the numbers of parts and therefore, the integrating step can be simplified and downsizing can be achieved by reducing the fabrication cost. Further, the reliability can be promoted without damaging the front end or the like of the optical fiber in attachment and detachment without restricting the number of times of attachment and detachment of the optical connector adapter and the optical connector plug. Further, since the optical connector adapter and the mounting member mounted to the mounting board are made to be attachable and detachable to and from each other and therefore, it is not necessary to carry out attachment and detachment of the optical connector adapter and the optical connector plug on the mounting board and downsizing of the mounting board can be achieved.