Abstract:
In an optical fiber connector ( 1 ), an outer member ( 2 ) holds a portion of an optical fiber (4A) remote from its connecting end which is connectable to a connecting end of a counterpart optical fiber. An aligning member ( 3 ) is held by the outer member so as to be movable along the optical fiber. The aligning member carries out positioning of the connecting end of the optical fiber. The aligning member is urged by a spring ( 5 ) in a direction to project from the outer member. When connecting the optical fiber to the counterpart optical fiber, the aligning member is moved in a direction opposite to the foregoing direction against an urging force applied by the spring so that the connecting end of the optical fiber is projected from the aligning member.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an optical fiber connector for connection between optical fibers. 
     For a better understanding of the present invention, description will be made at first as regards a first and a second conventional optical fiber connector. 
     Referring to FIG. 1, the first conventional optical fiber connector is of a plug-adapter-plug type for connecting plugs  30  and  30 ′ via an adapter  40 . The plug  30  comprises an outer member  31 , an optical fiber aligning base plate  32  having a number of V-grooves, a pair of optical fiber guides  33  each having a number of V-grooves, an optical fiber aligning guide  34 , a rear shell  35 , a pair of plate springs  36  provided at both sides of the rear shell  35  for pressing the optical fiber aligning guide  34 , and an optical fiber bunch  37 . 
     The optical fiber aligning base plate  32  and the optical fiber guides  33  are disposed in the optical fiber aligning guide  34 . The optical fiber bunch  37  is formed by aligning optical fibers  37 A in parallel. The optical fibers  37 A are inserted from a side of the rear shell  35 , then pass on the V-grooves of the optical fiber aligning base plate  32  and between the V-grooves of the pair of optical fiber guides  33  so as to be projected from an end surface  31 A of the outer member  31 . The plug  30 ′ has the same structure as the plug  30 . 
     The adapter  40  comprises a pedestal holder  41 , a pair of blocks  42  provided at both sides of the center of the holder  41 , a micro-sleeve retaining base plate  43  having a number of V-grooves, a number of micro-sleeves  44  parallelly arranged on the micro-sleeve retaining base plate  43 , an aligning plate spring  45  symmetrically provided on an upper surface of each of the blocks  42 , and a guide holding plate spring  46  symmetrically provided on a side of each of the blocks  42 . 
     When the plugs  30  and  30 ′ are fitted to the adapter  40  from both sides thereof, the optical fibers  37 A and  37 ′A are inserted into the corresponding micro-sleeves  44  from both sides thereof so that end surfaces of the optical fibers  37 A and  37 ′A abut each other to be connected. 
     Referring now to FIGS. 2 to  4 , the second conventional optical fiber connector is of a plug-receptacle type for connecting a plug  50  to a receptacle  70 . The plug  50  comprises a plug frame  60 , an optical fiber bunch  52  formed by parallelly aligning a number of optical fibers  52 A, a first base plate  53  having a number of V-grooves, a second base plate  54  having a number of V-grooves, a V-groove guide  55 , a clamping presser plate  56 , contractile tubes  57  for covering the optical fibers, a rear shell  59 , a pair of plate springs  58  provided at both sides of the rear shell  59  for pressing the V-groove guide  55 , and an optical fiber fixing base plate  61 . 
     The first and second base plates  53  and  54  are disposed in the V-groove guide  55 . Since the first and second base plates  53  and  54  and the V-groove guide  55  cooperatively align the optical fibers  52 A, they are generically called an optical fiber aligning member  65 . 
     The receptacle  70  comprises a shell  75 , a V-groove guide  73  having a ]-shape in section, a V-groove base plate  72  disposed in the V-groove guide  73  and having a number of V-grooves, a number of micro-sleeves  71  aligned on the V-groove base plate  72 , optical fibers  77  received in the corresponding micro-sleeves  71 , and a presser plate  76 . 
     The plug  50  is fitted to the receptacle  70  and then fixed by a fixing spring  78 . The plug frame  60  is attached to the V-groove guide  73  so that the optical fibers  52 A are inserted into the micro-sleeves  71 . In the micro-sleeves  71 , end surfaces of the optical fibers  52 A come in abutment with end surfaces of the corresponding optical fibers  77  so as to be connected to each other. 
     In the first conventional optical fiber connector, it is necessary that the ends of the optical fibers  37 A be projected beyond the end surface  31 A of the outer member  31  as shown in FIG.  1 A. On the other hand, in the second conventional optical fiber connector, the ends of the optical fibers  52 A may be retreated from an end surface  60 A of the plug frame  60  as shown in FIG.  3 . However, since the optical fibers  37 A and  52 A are exposed to the exterior both in the first and second conventional optical fiber connectors, they are highly liable to be damaged. 
     Further, since the optical fibers  37 A and  52 A in the plugs  30  and  50  are subjected to positioning in the aligning members  44  and  71  of the adapter  40  and the receptacle  70  and then connected to the optical fibers  37 ′A and  77 , respectively, it is necessary that the optical fibers  37 A and  52 A be projected from an end surface  34 A of the optical fiber aligning guide  34  and an end surface  55 A of the V-groove guide  55  at least by about 2 to 3 mm. 
     For example, for realizing a multi-fiber connector of 0.25 mm pitch, the accuracy required for positioning between each optical fiber in a plug and an aligning member of an adapter or receptacle is about 0.1 mm (0.05 mm on one side). 
     When performing the positioning between each optical fiber and the aligning member, a positional error is caused in a pitch direction or in a direction perpendicular to the pitch direction due to dimensional dispersion of the respective portions of the optical fiber connector. This positional error has been dealt with by improving the dimensional accuracy of the parts, thereby resulting in increased producing cost of the optical fiber connector. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an optical fiber connector which has a structure for protecting an optical fiber and is capable of facilitating positioning between the optical fiber and an aligning member thereby to reduce the producing cost thereof. 
     It is another object of the present invention to provide an optical fiber connector which can stably perform positioning between an optical fiber and an adapter. 
     It is another object of the present invention to provide an optical fiber connector which can easily select bending or non-bending of an optical fiber. 
     Other objects of the present invention will become clear as the description proceeds. 
     According to one aspect of the present invention, there is provided an optical fiber connector for connecting an optical fiber to a counterpart optical fiber by abutting a connecting end of the optical fiber against a connecting end of the counterpart optical fiber in a given direction while bending of the optical fiber is caused at a portion thereof, the connector comprising an outer member which holds a portion of the optical fiber remote from the connecting end of the optical fiber, an aligning member which is held by the outer member so as to be movable in the given direction and in a direction opposite to the given direction, the aligning member positioning the connecting end of the optical fiber, and an urging member which urges the aligning member in the given direction, the aligning member being moved, when connecting the optical fiber to the counterpart optical fiber, in the direction opposite to the given direction against an urging force applied by the urging member so that the connecting end of the optical fiber is projected from the aligning member. 
     It may be arranged that a connecting-side end surface of the aligning member is located on the same plane as a connecting-side end surface of the outer member before connecting the optical fiber to the counterpart optical fiber. 
     It may be arranged that a connecting-side end surface of the aligning member is projected from a connecting-side end surface of the outer member before connecting the optical fiber to the counterpart optical fiber. 
     It may be arranged that the connecting end of the optical fiber is retreated from an connecting-side end surface of the aligning member before connecting the optical fiber to the counterpart optical fiber. 
     It may be arranged that the urging member is made of metal. 
     It may be arranged that the urging member is made of resin. 
     It may be arranged that the urging member has a shape of a torsion coil. 
     It may be arranged that the urging member has a shape of an expansion coil. 
     It may be arranged that the urging member has a plate shape. 
     It may be arranged that the optical fiber connector further comprises an adapter to be fitted to the outer member, wherein the adapter comprises an aligning member for receiving therein the connecting end of the optical fiber for alignment thereof and, upon fitting of the outer member and the adapter, the adapter moves the aforementioned aligning member in the direction opposite to the given direction against the urging force applied by the urging member. 
     It may be arranged that the adapter is guided by an inner periphery of the outer member when moving the aforementioned aligning member in the direction opposite to the given direction. 
     It may be arranged that the optical fiber connector further comprises a fitting piece which is attached to the outer member so as to contact the optical fiber to control the bending of the optical fiber. 
     It may be arranged that the fitting piece is detachable relative to the outer member. 
     It may be arranged that the fitting piece has an elastic member which contacts the optical fiber. 
     According to another aspect of the present invention, there is provided an optical fiber connector comprising a first optical connector plug and an adapter for connecting the first optical connector plug to a second optical connector plug, the first optical connector plug comprising an outer member which holds an optical fiber, a first aligning member which performs positioning of the optical fiber at a connecting-side end of the outer member, and a spring which urges the first aligning member in a first direction, the adapter comprising a second aligning member which receives a connecting end of the optical fiber for alignment thereof, the second aligning member being moved, upon fitting of the first optical connector plug and the adapter, along an inner periphery of the outer member to a given position in a second direction opposite to the first direction and then pushes the first aligning member to slide it in the second direction, so that the optical fiber in the first connector plug is inserted into the second aligning member for connection. 
     According to still another aspect of the present invention, there is provided an optical fiber connector comprising a first and a second optical connector plug each having an optical fiber and an adapter for connecting the first and second optical connector plugs via the adapter, wherein a contact force between an end surface of the optical fiber of the first optical connector plug and an end surface of the optical fiber of the second optical connector plug is obtained from a buckling load caused by bending of at least one of the optical fibers, each of the first and second optical connector plugs comprising a clamp member which firmly holds a first portion of the optical fiber other than a tip portion thereof including the end surface, a first outer member which holds the clamp member, and a fitting piece which is detachably held by the first outer member, the adapter comprising an aligning member which slidably holds the tip portion of the optical fiber, and a second outer member which holds the aligning member, the fitting piece having one of a first shape which presses a second portion of the optical fiber between the first portion and the tip portion when the fitting piece is held by the first outer member, and a second shape which does not press the second portion of the optical fiber when the fitting piece is held by the first outer member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIGS. 1A to  1 C are perspective views of a first conventional optical fiber connector, wherein FIG. 1A shows one of optical connector plugs, FIG. 1B shows the other optical connector plug and FIG. 1C shows an adapter; 
     FIG. 2 is a vertical sectional view of a second conventional optical fiber connector; 
     FIG. 3 is a partly-sectioned perspective view of an optical connector plug of the optical fiber connector shown in FIG. 2; 
     FIG. 4 is a partly-sectioned perspective view of a receptacle of the optical fiber connector shown in FIG. 2; 
     FIG. 5 is a partly-sectioned perspective view of an optical connector plug as an optical fiber connector according to a first embodiment of the present invention, wherein an end surface of an aligning member is projected from an end surface of an outer member; 
     FIG. 6 is a partly-sectioned perspective view of the optical connector plug shown in FIG. 5, wherein the end surface of the aligning member is retreated from the end surface of the outer member; 
     FIGS. 7A and 7B are partly-sectioned perspective views contrastively showing two states of the optical connector plug shown in FIG. 5, wherein FIG. 7A shows the state before fitting and FIG. 7B shows the state after fitting; 
     FIGS. 8A and 8B are partly-sectioned perspective views, wherein the optical connector plugs each having the structure shown in FIG. 5 are connected in a plug-adapter-plug fashion and wherein FIG. 8A shows the state before fitting and FIG. 8B shows the state after fitting; 
     FIG. 9 is a partly-sectioned perspective view, wherein the optical connector plug shown in FIG. 5 is connected in a plug-receptacle fashion and wherein the state before fitting is shown; 
     FIG. 10 is a horizontal sectional view of FIG. 8B; 
     FIG. 11 is a vertical sectional view, wherein the optical connector plug shown in FIG.  5  and an optical connector plug applied with a partial design change are connected in the plug-adapter-plug fashion and wherein the state after fitting is shown; 
     FIG. 12 is a horizontal sectional view, wherein the optical connector plug shown in FIG.  5  and the optical connector plug applied with the partial design change are connected in the plug-adapter-plug fashion and wherein only one of the optical connector plugs is fitted to an adapter; 
     FIG. 13 is a vertical sectional view, wherein the optical connector plug shown in FIG.  5  and the optical connector plug applied with the partial design change are connected in the plug-adapter-plug fashion and wherein only one of the optical connector plugs is fitted to the adapter; 
     FIG. 14 is a partly-sectioned perspective view showing a positional relationship between the aligning member and each of optical fibers in the optical connector plug shown in FIG. 5; 
     FIG. 15 is a partly-sectioned perspective view showing a bending state of each of the optical fibers in the optical connector plug shown in FIG. 5; 
     FIG. 16 is a partly-sectioned perspective view showing an optical fiber connector according to a second embodiment of the present invention; 
     FIG. 17 is a partly-sectioned perspective view showing the state of connecting an optical connector plug and an adapter shown in FIG. 16; 
     FIG. 18 is a partly-sectioned perspective view showing the state of connecting the optical connector plug and the adapter shown in FIG. 16; 
     FIG. 19 is an enlarged view of the main part shown in FIG. 18; 
     FIG. 20 is a partly-sectioned perspective view showing an optical fiber connector according to a third embodiment of the present invention; 
     FIG. 21 is a perspective view showing the connected state of the optical fiber connector shown in FIG. 20; 
     FIG. 22 is a horizontal sectional view showing the state of the optical fiber connector shown in FIG. 20 just before the complete connection thereof; 
     FIG. 23 is a vertical sectional view showing the state of the optical fiber connector shown in FIG. 20 just before the complete connection thereof; 
     FIG. 24 is an enlarged view of the main part shown in FIG. 23; 
     FIG. 25 is a horizontal sectional view showing the completely connected state of the optical fiber connector shown in FIG. 20; 
     FIG. 26 is a perspective view of an optical connector plug used in an optical fiber connector according to a fourth embodiment of the present invention; 
     FIG. 27 is a perspective view of a fitting piece used in the optical connector plug shown in FIG. 26; 
     FIG. 28 is a perspective view of another fitting piece used in the optical connector plug shown in FIG. 26; 
     FIG. 29 is a partly-sectioned perspective view showing an example wherein two optical connector plugs each having the structure shown in FIG. 26 are connected via an adapter; 
     FIG. 30 is a partly-sectioned perspective view showing the state wherein optical fibers are bent in the optical connector plug using the fitting piece shown in FIG. 27; 
     FIG. 31 is a partly-sectioned perspective view showing the state wherein optical fibers are not bent in the optical connector plug using the fitting piece shown in FIG. 28; 
     FIG. 32 is a perspective view of the main part shown in FIG. 31; 
     FIG. 33 is a vertical sectional view showing the state wherein the optical connector plugs both using the fitting pieces shown in FIG. 27 are connected via the adapter; and 
     FIG. 34 is a vertical sectional view showing the state wherein the optical connector plug using the fitting piece shown in FIG.  27  and the optical connector plug using the fitting piece shown in FIG. 28 are connected via the adapter. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 5 to  15 , description will be made as regards an optical connector plug  1  as an optical fiber connector according to a first embodiment of the present invention. 
     In FIG. 5, an end surface  3 B of an aligning member  3  is projected from an end surface  2 A of an outer member  2 . In the outer member  2 , the aligning member  3  is slidably disposed. The aligning member  3  is formed near the end surface  3 B thereof with a number of parallel slots  3 A for receiving therein a number of optical fibers  4 A (only some of which are shown). The aligning member  3  is further formed with a number of small holes  3 C which parallelly extend inward from the end surface  3 B. Each of the small holes  3 C has an inner diameter (0.14 mm) which is slightly greater than an outer diameter (0.125 mm) of each of the optical fibers  4 A. The aligning member  3  is urged by a torsion coil spring  5  in a direction to project from the end surface  2 A of the outer member  2 . Two pairs of first and second clamp members  6  and  7  are mounted in a concave portion  2 B of the outer member  2 . The optical fibers  4 A forming a pair of tape fibers  4  are bonded to the corresponding first clamp members  6  and can be projected from the corresponding small holes  3 C via a number of parallel slots  7 A formed on the second clamp members  7 , the inside space of the outer member  2  and the slots  3 A of the aligning member  3 . The second clamp members  7  are bonded to the corresponding first clamp members  6  for protecting those portions where the optical fibers  4 A are bonded to the first clamp members  6 . On the other hand, the second clamp members  7  may be formed integral with the outer member  2 . 
     In FIG. 6, the end surface  3 B of the aligning member  3  is retreated from the end surface  2 A of the outer member  2 . Since each of the optical fibers  4 A is located inward of the end surface  3 B of the aligning member  3  (see FIG.  14 ), a fitting-side end portion of the optical connector plug  1  is protected. However, since a fitting-side end of each optical fiber  4 A is located inward of the outer member  2 , connection of a plug-adapter-plug type (see FIGS. 8A,  8 B) can not be achieved using two optical connector plugs  1 . On the other hand, connection of a plug-receptacle type (see FIG. 9) can be achieved using one optical connector plug  1  and one receptacle. 
     In FIG. 7A, the end surface  3 B of the aligning member  3  is projected from the end surface  2 A of the outer member  2 . Specifically, FIG. 7A shows the state of the optical connector plug  1  before the end surface  3 B of the aligning member  3  is pushed into the outer member  2  by a member of an adapter (not shown), i.e. the state before fitting to the adapter (initial state). 
     In FIG. 7B, the end surface  3 B of the aligning member  3  is retreated from the end surface  2 A of the outer member  2 . Specifically, FIG. 7B shows the state of the optical connector plug  1  wherein the end surface  3 B of the aligning member  3  is pushed into the outer member  2  by the member of the adapter, i.e. the state after fitting to the adapter, and the optical fibers  4 A are projected from the end surface  3 B. 
     In FIGS. 8A and 8B, the optical connector plug  1 ′ has the same structure as the optical connector plug  1 . Portions of the optical connector plug  1 ′ correspond to those of the optical connector plug  1  are assigned the same reference signs with dash (′). 
     In FIG. 8A showing the state before fitting to an adapter  11 , the adapter  11  comprises a pair of outer members  12  each in the form of a rectangular tube with a pair of flanges, a V-groove base plate retaining member  13  disposed in the outer members  12  at an adjoined portion thereof, a V-groove base plate  14  disposed on the V-groove base plate retaining member  13 , and a number of micro-sleeves  15  parallelly arranged on the V-groove base plate  14 . The outer members  12  are fixed together by inserting bolts into holes  12 C formed through the respective flanges thereof. The V-groove base plate retaining member  13 , the V-groove base plate  14  and the micro-sleeves  15  may be formed integral with each other of a resin material. 
     In FIG. 8B showing the state after fitting to the adapter  11 . For fitting to the adapter  11 , the optical connector plugs  1  and  1 ′ are first inserted into rectangular tubular portions  12 A of the corresponding outer members  12 . Then, bent engaging portions  16 A of each of lock springs  16 , formed at both sides of the lock spring  16  at one end thereof, are engaged with engaging concave portions  12 B of the corresponding outer member  12  formed at both sides of the outer member  12  at one end thereof, and curved plate spring portions  16 B of each lock spring  16 , formed at both sides of the lock spring  16  at the other end thereof, are engaged with end surface engaging portions  2 C or  2 ′ C of the corresponding optical connector plug  1  or  1 ′ formed at both sides of the optical connector plug  1  or  1 ′ at the other end thereof. 
     In FIG. 9, a receptacle  21  comprises an outer member  22  in the form of a flanged rectangular tube, a V-groove base plate retaining member  23  disposed in the outer member  22 , a V-groove base plate  24  disposed on the V-groove base plate retaining member  23 , and a number of micro-sleeves  25  parallelly arranged on the V-groove base plate  24 . 
     Optical fibers  26 A are bonded to the corresponding micro-sleeves  25 . Each of the micro-sleeves  25  has an outer diameter of 0.25 mm and an inner diameter of 0.126 mm, while each of the optical fibers  26 A has an outer diameter of 0.125 mm. Positioning between each of the optical fibers  26 A and the corresponding micro-sleeve  25  is carried out so that each optical fiber  26 A is connected to the corresponding micro-sleeve  25 . The micro-sleeves  25 , the V-groove base plate  24  and the V-groove base plate retaining member  23  may be formed integral with each other of a resin material. 
     In FIG. 10, an end surface of each of the optical fibers  4 A of the optical connector plug  1  and an end surface of each of optical fibers  4 ′A of the optical connector plug  1 ′ are so positioned as to confront each other in the corresponding micro-sleeve  15  of the adapter  11 . One of the flanges of each of the outer members  12  is formed with a positioning projection  12 D, while the other is formed with a hole  12 E. The positioning projection  12 D of each of the outer members  12  is first inserted into the hole  12 E of the confronting outer member  12 , then both outer members  12  are firmly fixed together by means of bolts  12 F and nuts  12 G at the holes  12 C of the flanges of the outer members  12 . 
     In FIG. 11, the optical connector plug  1 ′ differs in structure from the optical connector plug  1  only in the following points: Specifically, the optical connector plug  1 ′ is provided with a third clamp member  8 ′ adjacent to a first clamp member  6 ′, and optical fibers  4 ′A are bonded to the third clamp member  8 ′. Further, a length of each optical fiber  4 ′A of the optical connector plug  1 ′ is set to be slightly shorter than that of each optical fiber  4 A of the optical connector plug  1 . 
     Therefore, only each optical fiber  4 A of the optical connector plug  1  is subjected to bending as shown in FIG.  11 . Accordingly, an end surface of each optical fiber  4 A and an end surface of each optical fiber  4 ′A abut each other with an adequate pressing force, so that the optical performance is stabilized. A length of a bent portion of each optical fiber  4 A is about 10 mm so that the pressing force is suppressed to an extent where an adequate buckling load is applied to each optical fiber  4 ′A. 
     In FIG. 12, the optical connector plug  1 ′ is fitted to the adapter  11  while the optical connector plug  1  is not yet fitted to the adapter  11 . An aligning member  3 ′ of the optical connector plug  1 ′ is pressed by the V-groove base plate retaining member  13  of the adapter  11  so as to be pushed into an outer member  2 ′ against a torsion force of a torsion coil spring  5 ′. Accordingly, one end of each optical fiber  4 ′A is projected from an end surface  3 ′B of the aligning member  3 ′ and thus can be inserted into the corresponding micro-sleeve  15  of the adapter  11 . Since the aligning member  3  of the optical connector plug  1  is not yet pressed by the V-groove base plate retaining member  13  of the adapter  11 , one end of each optical fiber  4 A is not projected from the end surface  3 B of the aligning member  3 . 
     In FIG. 13, the optical connector plug  1 ′ is fitted to the adapter  11  while the optical connector plug  1  is not yet fitted to the adapter  11 . 
     In FIG. 14, since a width of each slot  3 A is set to be slightly greater than the outer diameter of each optical fiber  4 A, each optical fiber  4 A is slidably received in the corresponding slot  3 A. On the other hand, since a depth of each slot  3 A is set to be several times the outer diameter of each optical fiber  4 A, a bending direction of each optical fiber  4 A is limited to a depth direction of the slot  3 A. 
     In FIG. 15, since the parallel slots  3 A are provided on the aligning member  3  of the optical connector plug  1 , the optical fibers  4 A received in the corresponding slots  3 A can be bent in one direction, i.e. upward. 
     In the foregoing description, the end surface  3 B of the aligning member  3  is projected beyond the end surface  2 A of the outer member  2  before the fitting. However, it may be arranged that the end surface  3 B of the aligning member  3  is located on the same plane as the end surface  2 A of the outer member  2 . Further, a material of the torsion coil springs  5  and  5 ′ is not limited to metal, but may be synthetic resin or the like. Moreover, the torsion coil springs  5  and  5 ′ may be replaced with expansion coil springs, plate springs or the like. 
     The foregoing optical connector plug  1  can achieve the following effects: 
     1. A fitting-side end of each optical fiber is not projected from the aligning member and is thus protected therewithin when the optical connector plug is not fitted to the adapter or receptacle. Thus, handling of the optical connector plug is facilitated. 
     2. The aligning member is slidable upon fitting so that positioning between the optical connector plug and the adapter or receptacle is easy. Accordingly, it is applicable to a narrow-pitch or multi-fiber optical fiber connector. 
     3. Since the positioning accuracy required for the narrow-pitch or multi-fiber optical fiber connector is relaxed, the cost can be reduced. 
     4. Since the optical connector plug is applicable to not only the plug-receptacle type connection, but also the plug-adapter-plug type connection, it can contribute to realization of a general purpose optical fiber connector. 
     With reference to FIGS. 16 to  19 , the description will be made as regards an optical fiber connector according to a second embodiment of the present invention. Similar parts are designated by like reference numerals. 
     As shown in FIG. 16, the optical fiber connector basically comprises an optical connector plug  1  and an adapter  11  for connecting the optical connector plug  1  to another optical connector plug such as an optical connector plug  1 ′ shown in FIG.  20 . 
     The optical connector plug  1  (or the optical connector plug  1 ′) comprises a pair of tape fibers  4  each obtained by forming a number of parallel optical fibers  4 A together into a flat plate shape using synthetic resin or the like, a pair of clamp members  6  clamping the optical fibers  4 A which are exposed by removing coating of the tape fibers  4  at end portions thereof, an aligning member  3  holding tip portions of the optical fibers  4 A in an aligned state, an outer member  2  holding the clamp members  6 , the aligning member  3  and so forth, and an elastic member  5  elastically pressing the aligning member  3  in a direction (lower-left direction in FIG. 16) to project from the end surface of the outer member  2 . The aligning member  3  is slidable inside the outer member  2  along the optical fibers  4 A. 
     The adapter  11  includes a V-groove base plate retaining member  13 . On the V-groove base plate retaining member  13 , there are mounted a V-groove base plate  14  formed thereon with a number of parallel V-grooves, and a number of micro-sleeves  15  as an aligning member which are retained in the corresponding V-grooves and allow the corresponding optical fibers  4 A to pass therethrough. In this fashion, the tip portions of the optical fibers  4 A are slidably held. 
     In this optical fiber connector, when connecting the optical fibers  4   a  to the adapter  11 , the adapter  11  is inserted along the inner periphery of the outer member  2  to a predetermined position as shown in FIG.  17 . Then, the end surface of the aligning member  3  is caused to abut an end surface of the V-groove base plate retaining member  13 . Subsequently, as shown in FIGS. 16 to  19 , the aligning member  3  is further pushed by the adapter  11  so as to slide in a direction opposite to the direction in which the aligning member  3  is pressed by the elastic member  5 , so that the tip portions of the optical fibers  4 A are projected from the aligning member  3 . Then, by further pushing the aligning member  3  in the same direction, the tip portions of the optical fibers  4 A are inserted into the micro-sleeves  15  of the adapter  11 . 
     The position of the optical fibers  4 A in the optical connector plug  1  is set based on the inner periphery of the outer member  2 . Further, the position of the micro-sleeves  15  relative to the optical connector plug  1  is set based on the outer periphery of the V-groove base plate retaining member  13 . Then, positioning between the aligning member  3  and the V-groove base plate retaining member  13  is carried out using the inner periphery of the outer member  2  as an aligning guide or a positioning guide. 
     According to the optical fiber connector in this embodiment, the positioning between the optical fibers and the adapter can be achieved stably. Since the positioning between the optical fibers in the optical connector plug and the aligning member in the adapter can be stably carried out, it is applicable to the narrow-pitch multi-fiber connector. Further, by using the inner periphery of the outer member of the optical connector plug as an aligning or positioning guide, the optical connector plug can be reduced in size. 
     With reference to FIGS. 20 to  25 , the description will be made as regards an optical fiber connector according to a third embodiment of the present invention. Similar parts are designated by like reference numerals. 
     In the optical fiber connector, an optical connector plug  1  and an optical connector plug  1 ′ are connected via an adapter  11 . Specifically, as shown in FIGS. 20 and 21, the optical fiber connector comprises the optical connector plug  1 , the optical connector plug  1 ′, the adapter  11  and two lock springs  16  for connecting the optical connector plugs  1  and  1 ′ to the adapter  11 , respectively. As in the foregoing embodiments, the adapter  11  includes a V-groove base plate retaining member  13  mounted thereon with a V-groove base plate  14  and micro-sleeves  15 , and a pair of outer members  12  holding the V-groove base plate retaining member  13 . 
     In the optical fiber connector, the optical connector plug  1  is connected to the adapter  11  in the foregoing manner, and the optical connector plug  1 ′ is also connected to the adapter  11  in the same manner. The connected state is shown in FIGS. 22 to  24 . As shown in FIG. 22, an outer member  2  ( 2 ′) of the optical connector plug  1  ( 1 ′) is provided with engaging portions  21  ( 21 ′), and each of the outer members  12  of the adapter  11  is provided with elastic engaging straps  121  ( 121 ′). Through engagement between the engaging portions  21  ( 21 ′) and the engaging straps  121  ( 121 ′), the optical connector plug  1  ( 1 ′) can be provisionally fixed to the adapter  11 . 
     In FIG. 25, the state wherein the optical connector plugs  1  and  1 ′ are finally connected together via the adapter  11 . By allowing the optical fibers in one of the optical connector plugs to be bent in the state shown in FIG. 25, a contact force between end surfaces of the optical fibers can be obtained from a buckling load generated by bending of the optical fibers. 
     Also in the optical fiber connector of the third embodiment, positioning between the optical fibers and the adapter can be implemented stably. Since the positioning between the optical fibers in the optical connector plug and the aligning member in the adapter can be stably carried out, it is applicable to the narrow-pitch multi-fiber connector. Further, by using the inner periphery of the outer member of the optical connector plug as an aligning or positioning guide, the optical connector plug can be reduced in size. 
     With reference to FIGS. 26 to  34 , the description will be made as regards an optical fiber connector according to a fourth embodiment of the present invention. Similar parts are designated by like reference numerals. 
     In the optical fiber connector, a concave portion  22  is provided on an outer member  2 , and a fitting piece  32  is detachably held in the concave portion  22 . As the fitting piece  32 , either of a first fitting piece  321  shown in FIG. 27 and a second fitting piece  322  shown in FIG. 28 is used. As described later, the fitting piece  321  has a structure which does not press a portion of each of optical fibers  4 A between clamp members  6  and an aligning member  3  when the fitting piece  321  is fitted in the concave portion  22  of the outer member  2 . On the other hand, in the same state, the fitting piece  322  has a structure which presses the portion of each optical fiber  4 A between the clamp members  6  and the aligning member  3  so as to hold such a portion of each optical fiber  4 A substantially in a linear fashion. 
     In the optical fiber connector of the fourth embodiment, the fitting piece  321  is fitted in the optical connector plug  1 , while the fitting piece  322  is fitted in the optical connector plug  1 ′. As shown in FIG. 30, since the fitting piece  321  does not press the portion of each optical fiber  4 A between the clamp members  6  and the aligning member  3  in the optical connector plug  1 , each optical fiber  4 A is bent between the clamp members  6  and the aligning member  3 . 
     On the other hand, as shown in FIGS. 31 and 32, the fitting piece  322  presses a portion of each of optical fibers  4 ′A between clamp members  6 ′ and an aligning member  3 ′ so as to hold such a portion of each optical fiber  4 ′A substantially in a linear fashion in the optical connector plug  1 ′. The fitting piece  322  is provided with an elastic member  322   a  at the underside thereof, i.e. at the optical fiber pressing side. By providing such an elastic member  322   a , the pressing of the optical fibers  4 ′A can be reliably achieved due to elastic deformation of the elastic member  322   a.    
     According to the optical fiber connector in the fourth embodiment, the fitting pieces  321  and  322  are detachably held in the concave portions  22  and  22 ′ of the outer members  2  and  2 ′ in the optical connector plugs  1  and  1 ′, respectively. By changing between the fitting pieces  321  and  322  in view of the fitting state of the optical connector plugs upon assembling the optical fiber connector, bending of the optical fibers can be generated in either one of the optical connector plugs or in both of them so as to obtain an adequate buckling load. 
     In an example shown in FIG. 33, the fitting pieces  321  are used both in the optical connector plugs  1  and  1 ′. Accordingly, the optical fibers  4 A and  4 ′A are both bent to produce a buckling load so that the end surfaces of the optical fibers  4 A and  4 ′A abut each other with a large contact force. 
     On the other hand, in an example shown in FIG. 34, the fitting piece  321  is used in the optical connector plug  1  while the fitting piece  322  is used in the optical connector plug  1 ′, so that only the optical fibers in the optical connector plug  1  are subjected to bending. 
     Since the optical connector plugs  1  and  1 ′ in the fourth embodiment can be produced from the same parts except the fitting pieces, the parts can be shared between the optical connector plugs so that the corresponding cost reduction can be realized. 
     While the present invention has been described in terms of the preferred embodiments, the invention is not to be limited thereto, but can be embodied in various ways without departing from the principle of the invention as defined in the appended claims.