Patent Abstract:
Provided is an optical connector in which a through-hole of a housing is opened in a side surface of the housing and a ferrule can be mounted to the housing from an opening portion formed in the side surface of the housing. Thus, it is unnecessary to constitute the housing by a plurality of components. Consequently, reduction in the numbers of components and assembly steps and reduction in cost can be achieved.

Full Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an optical connector for connecting an optical fiber to another optical fiber or an optical element. 
       BACKGROUND ART 
       [0002]    For example, in JP 2001-56420 A, there is described an optical connector including a ferrule (27) having a flange (26), and a housing (constituted by a front portion (12) and a rear portion (13)) for holding the ferrule. A through-hole is formed in the housing, and the ferrule is held in an inner periphery of the through-hole. Specifically, the through-hole is formed in each of the front portion (12) and the rear portion (13) of the housing. A forward end side of the ferrule is inserted into the through-hole of the front portion, and a proximal end side of the ferrule (which is hereinafter represented as a side opposite to the forward end side thereof) is inserted into the through-hole of the rear portion. In this state, the front portion and the rear portion are fixed to each other, and thus the ferrule is mounted in the inner periphery of the through-hole of the housing. 
         [0003]    The above-mentioned optical connector has a spring (coil spring (29)) mounted between the flange of the ferrule and the rear portion (13) of the housing, and hence the ferrule is biased toward the front portion (12). When such optical connector on one part is connected to an optical connector on the other part through an optical adapter, a forward end of the ferrule on the one part is brought into contact with a ferrule on the other part. Consequently, the ferrule on the one part retreats against resilience of the coil spring. Owing to a buffer function of the spring, the forward ends of the ferrules can be reliably brought into contact with each other. 
       Citation List 
       [0004]    Patent Literature 
       Patent Literature 1: JP 2001-56420 A 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    As described above, owing to a configuration in which the ferrule is completely received in the through-hole of the housing constituted by the front portion (12) and the rear portion (13), it is possible to reliably protect the ferrule from external impact. However, an optical connector used behind the wall (BTW), i.e., in an inside of a module box or the like, is rarely subjected to external contact, and hence the external impact is less likely to be applied thereto in comparison with an optical connector used on the wall (OTW). Thus, in the optical connector used on a place where the optical connector is rarely subjected to the external impact, the configuration having the above-mentioned housing constituted by a plurality of components becomes sometimes excessive. 
         [0006]    An object of the present invention is therefore to simplify a structure of the optical connector and to achieve reduction in cost. 
       Solution to Problem 
       [0007]    In order to achieve the above-mentioned object, the present invention provides an optical connector including: a ferrule including a flange portion; and a housing including a through-hole formed to hold the ferrule therein, in which the through-hole is opened in a side surface of the housing, and the ferrule is allowed to be mounted to an inner periphery of the through-hole from an opening portion formed in the side surface. 
         [0008]    As described above, the through-hole is opened in the side surface of the housing, and the ferrule is allowed to be mounted to the inner periphery of the through-hole from an opening portion formed in the side surface. Thus, it is unnecessary to constitute the housing by a plurality of components, and reduction in the numbers of components and assembly steps and reduction in cost can be achieved. The above-mentioned optical connector can be preferably used on a place where the optical connector is rarely subjected to external contact (behind the wall, for example). 
         [0009]    The optical connector may further include a reference surface formed integrally with the housing, for regulating retreat of the ferrule by being brought into contact with the flange portion of the ferrule from a proximal end side thereof. When the optical connector is mounted to an optical adapter, the ferrule on one part of the optical connector is pushed to the proximal end side by being brought into contact with a ferrule on the other part, and thus the flange portion is brought into contact with the reference surface. In this way, the retreat of the ferrule is regulated. As described above, the ferrule is positioned in the housing during use of the optical connector (during mounting to the optical adapter) by the reference surface provided integrally with the housing, and hence it is possible to omit a spring, and to achieve further reduction in cost. Such optical connector on the one part has no buffer function of the spring, and hence can be preferably used in a case where the optical connector on the other part connected thereto has a buffer function of the spring or the like. In this case, when a position of the reference surface is set within a movable range of the ferrule on the other part, it is possible to reliably bring the forward ends of the ferrules into contact with each other by the buffer function of the ferrule on the other part. 
         [0010]    Incidentally, it is desirable that a fiber core of an optical fiber inserted through the ferrule be arranged at a central axis position of the forward end of the ferrule. However, actually, due to factors such as eccentricity of an insertion hole with respect to an outer peripheral surface of the ferrule, eccentricity of the optical fiber with respect to an inner peripheral surface of the insertion hole, and eccentricity of the fiber core with respect to an outer peripheral surface of the optical fiber, the fiber core is arranged to be eccentric to the central axis position of the ferrule. For example, when, of a pair of ferrules of optical connectors connected together through the optical adapter, a fiber core of one ferrule is eccentric in an upward direction and a fiber core of the other ferrule is eccentric in a downward direction, deviation of the fiber cores is increased when the ferrules are brought into contact with each other. In contrast, when eccentric directions of the fiber cores of both the ferrules are aligned with a predetermined direction (upward direction, for example), the deviation of the fiber cores can be decreased. (As described above, an operation for aligning the eccentric directions of the fiber cores with the predetermined direction is referred as to “centering”.) 
         [0011]    When the ferrule is detachably attached to the housing, it is possible to easily perform centering. That is, in a state in which the ferrule is mounted to the housing, the eccentric direction of the fiber core of the optical fiber inserted through the ferrule is ascertained. Then, the ferrule is temporarily detached from the housing, rotated by a predetermined angle, and re-mounted to the housing. In this state, the eccentric direction of the fiber core is ascertained. The above-mentioned operation is repeated, and the ferrule is mounted to the housing at a position at which the eccentric direction is aligned with the predetermined direction. Consequently, the centering is completed. 
         [0012]    When provided is a cover portion which is formed integrally with the housing, covers an outer periphery of the ferrule projecting to the proximal end side thereof relative to the housing, and extends to the proximal end side relative to a proximal end of the ferrule, it is possible to protect the optical fiber inserted into the ferrule. 
         [0013]    When the ferrule is held in close contact with the housing on a cylindrical outer peripheral surface of the ferrule in a peripheral region extending over more than half of a circumference of the cylindrical outer peripheral surface, the ferrule can be restrained in an entire radius direction. Therefore, it is possible to reliably hold the ferrule by the housing. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0014]    As described above, according to the present invention, it is possible to simplify a structure of the optical connector and to achieve reduction in cost. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1A  A perspective view of an optical connector. 
           [0016]      FIG. 1B  A perspective view of the optical connector. 
           [0017]      FIG. 2A  A side view of the optical connector. 
           [0018]      FIG. 2B  A plan view of the optical connector. 
           [0019]      FIG. 2C  A front view of a forward end side of the optical connector. 
           [0020]      FIG. 2D  A front view of a proximal end side of the optical connector. 
           [0021]      FIG. 3A  A cross-sectional view taken along the line A-A of  FIG. 2B . 
           [0022]      FIG. 3B  A cross-sectional view taken along the line B-B of  FIG. 2A . 
           [0023]      FIG. 3C  A cross-sectional view taken along the line C-C of  FIG. 2A . 
           [0024]      FIG. 3D  A cross-sectional view taken along the line D-D of  FIG. 2A . 
           [0025]      FIG. 4  An enlarged view of  FIG. 3A . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    In the following, an embodiment of the present invention is described with reference to the drawings. 
         [0027]    As illustrated in  FIGS. 1A and 1B , an optical connector  1  according to the embodiment of the present invention includes a ferrule  10  and a housing  20  for holding the ferrule  10 . The optical connector  1  is mounted to an optical adapter (not shown), and is a so-called LC-type optical connector in which the ferrule  10  and the housing  20  are prevented from slipping off through engaging, with a locking portion of the optical adapter, a latch  22  provided to the housing  20  of the optical connector  1 . Note that, in the following, for convenience of the description, a central axis direction (Y direction in  FIGS. 1A and 1B ) of the ferrule  10  mounted to the housing  20  is referred to as an “axial direction”, a side on which a capillary  11  of the ferrule  10  projects from the housing  20  in the axial direction is referred to as a forward end side, and a side opposite thereto is referred to as a proximal end side. Further, a Z direction illustrated in  FIGS. 1A and 1B  is referred to as an up-down direction, a side on which the latch  22  of the housing  20  is provided is referred to as an upper side, and a side opposite thereto is referred to as a lower side. Moreover, a direction (X direction in  FIGS. 1A and 1B ) orthogonal to both of the axial direction and the up-down direction is referred to as a width direction. 
         [0028]    The ferrule  10  is attached to a forward end of an optical fiber (optical fiber wire or optical fiber wire with coating (not shown)). As illustrated in  FIG. 2A , the ferrule  10  includes the capillary  11 , a capillary holding portion  12 , and a protective tube  13 . The capillary  11  is made of a material such as ceramics (zirconia, for example) or glass, and has a micropore  11   a  which extends in the axial direction and through which the optical fiber is inserted (see  FIG. 3A ). The capillary holding portion  12  is made of a metal material such as brass, and has an inner hole  12   a  which extends in the axial direction and through which the optical fiber is inserted. On the forward end side of the inner hole  12   a , there is provided a fixation hole  12   a   1  having a diameter slightly larger than a diameter of the inner hole  12   a . The capillary  11  is press-fitted and fixed into the fixation hole  12   a   1 . A radial shoulder surface  12   a   2  is formed between the inner hole  12   a  and the fixation hole  12   a   1 , and an axial gap is formed between the shoulder surface  12   a   2  and a proximal end  11   c  of the capillary  11  (see  FIG. 4 ). 
         [0029]    A flange portion  12   b  projecting to a radially outer side thereof is formed at the forward end of the capillary holding portion  12 . As illustrated in  FIG. 4 , in the flange portion  12   b , there are formed a forward end surface  12   b   1  extending in a radial direction, a tapered surface  12   b   2  extending from the forward end surface  12   b   1  to the proximal end side to gradually increase in diameter to the proximal end side, and a larger-diameter outer peripheral surface  12   c  extending from the tapered surface  12   b   2  to the proximal end side. On the proximal end side of the flange portion  12   b  in an outer peripheral surface of the capillary holding portion  12 , a smaller-diameter outer peripheral surface  12   d  is formed. The larger-diameter outer peripheral surface  12   c  has a regular hexagonal cross-section in the radial direction (see  FIG. 3C ), and the smaller-diameter outer peripheral surface  12   d  has a cylindrical surface (see  FIG. 3D ). A shoulder surface  12   e  is formed between the larger-diameter outer peripheral surface  12   c  and the smaller-diameter outer peripheral surface  12   d  (see  FIG. 4 ). 
         [0030]    In the proximal end of the capillary holding portion  12 , there is provided a cylinder portion  12   f  which includes a claw portion at its end and has a diameter still smaller than a diameter of the smaller-diameter outer peripheral surface  12   d  (see  FIG. 3A ). The cylinder portion  12   f  projects to the proximal end side relative to a main body  21  of the housing  20 . The optical fiber (not shown) is inserted through an inner periphery of the cylinder portion  12   f , and the protective tube  13  is mounted so as to cover both of the outer peripheral surface of the cylinder portion  12   f  and the outer peripheral surface of the optical fiber. The protective tube  13  is made of a material (fluororesin or rubber, for example) being elastic enough to be able to be mounted on the outer periphery of the cylinder portion  12   f . Further, the protective tube  13  may be made of a material having a heat shrinkage property and be formed into a so-called heat-shrinkable tube. By being caused to shrink by heating, the protective tube  13  may be brought into close contact with the cylinder portion  12   f  and the optical fiber. The claw portion of the cylinder portion  12   f  bites into an inner peripheral surface of the protective tube  13 , and thus the protective tube  13  is elastically deformed to the radially outer side thereof. As a result, the protective tube  13  and the claw portion are engaged with each other in the axial direction, and hence the protective tube  13  is regulated from slipping off. 
         [0031]    The housing  20  is integrally die-molded (injection-molded, for example) of a resin material, etc. The housing  20  includes the main body  21  of a substantially rectangular parallelepiped, the latch  22  provided on one side surface (upper surface) of the main body  21 , and a cover portion  23  extending from the main body  21  to the proximal end side. 
         [0032]    The main body  21  has a through-hole  30  formed to pass through the main body  21  in the axial direction. The ferrule  10  is held in an inner periphery of the through-hole  30 . The through-hole  30  is opened in a side surface (surface except for end surfaces on both sides in the axial direction) of the housing  20 . In the illustrated example, the through-hole  30  is opened in one side surface in the width direction of the main body  21  over an entire axial length thereof. Thus, the main body  21  is formed into a substantially C-shape in its front view (see  FIGS. 2C and 2D ). Note that, except for a case where the through-hole  30  is opened in the side surface as in the illustrated example, the through-hole  30  may be opened in the other side surface in the width direction of the housing  20  or a side surface on the lower side of the housing  20 . 
         [0033]    The through-hole  30  includes a larger-diameter hole  31  opened in the forward end surface of the main body  21 , and a holding hole  32  provided on the proximal end side of the larger-diameter hole  31  (see  FIG. 3A ). The capillary  11  is placed in the inner periphery of the larger-diameter hole  31 , and the capillary holding portion  12  is held in the inner periphery of the holding hole  32 . 
         [0034]    As illustrated in  FIG. 4 , in the inner peripheral surface of the holding hole  32 , there are formed a partially-tapered inner surface  32   a  gradually decreasing in diameter to the forward end side to be opened in one side surface in the width direction of the housing  20 , a partially-angled inner surface  32   b  extending from the partially-tapered inner surface  32   a  to the proximal end side to be opened in the one side surface in the width direction thereof (see  FIG. 3C ), and reference surfaces  32   c  extending upright from the partially-angled inner surface  32   b  radially inward. The partially-tapered inner surface  32   a , the partially-angled inner surface  32   b , and the reference surfaces  32   c  are die-molded integrally with the housing  20 . The partially-tapered inner surface  32   a  and the partially-angled inner surface  32   b  are opposed to the flange portion  12   b  of the capillary holding portion  12  through a gap, and the reference surfaces  32   c  are brought into contact with the proximal-end side surface  12   e  (shoulder surface  12   e ) of the flange portion  12   b  from the proximal end side. The reference surfaces  32   c  are provided to end surfaces on the forward end side of protrusions  21   a  projecting from two upper and lower positions in an inner surface of the holding hole  32  of the main body  21 . 
         [0035]    As illustrated in  FIG. 3D , at a deep side in the width direction (an opposite side to an opening side) of the holding hole  32 , which is formed between protrusions  21   a  provided at the upper and lower positions, there is provided a partially-rounded inner surface  32   d  for holding the smaller-diameter outer peripheral surface  12   d  of the capillary holding portion  12  of the ferrule  10 . The partially-rounded inner surface  32   d  is held in close contact with the smaller-diameter outer peripheral surface  12   d  in a peripheral region M extending over more than half of a circumference of the smaller-diameter outer peripheral surface  12   d . Thus, the ferrule  10  is restrained in an entire radius direction. In the illustrated example, the partially-rounded inner surface  32   d  is held in close contact with the smaller-diameter outer peripheral surface  12   d  in an entire region on a deep side in the width direction with respect to an upper end and a lower end of the smaller-diameter outer peripheral surface  12   d  and in a partial region on the opening side in the width direction with respect to the upper end and the lower end thereof. An inner diameter of the partially-rounded inner surface  32   d  of the housing  20  before mounted with the ferrule  10  is slightly smaller than an inner diameter D of the smaller-diameter outer peripheral surface  12   d  of the ferrule  10 , and is set to be slightly larger than a space S in the up-down direction between the protrusions  21   a . Therefore, the ferrule  10  is mounted to the partially-rounded inner surface  32   d  of the holding hole  32  of the housing  20  while elastically deforming the housing  20  by pushing the smaller-diameter outer peripheral surface  12   d  in between the upper and lower protrusions  21   a . Note that, a configuration of the partially-rounded inner surface  32   d  is not limited to the above-mentioned one. For example, the inner diameter of the partially-rounded inner surface  32   d  may be equal to the space S in the up-down direction between the upper and lower protrusions  21   a . In this case, through press-fitting the ferrule  10  to the partially-rounded inner surface  32   d  while deforming the housing  20 , the partially-rounded inner surface  32   d  can be held in close contact with the smaller-diameter outer peripheral surface  12   d  of the ferrule  10  in the peripheral region extending over more than half of the circumference of the smaller-diameter outer peripheral surface  12   d.    
         [0036]    The latch  22  extends obliquely upward from a forward-end side portion of the upper surface of the main body  21  to the proximal end side, and includes on its middle portion a locking surface  22   a  facing the proximal end side. In a state in which the optical connector  1  is mounted to the optical adapter, the locking surface  22   a  is engaged with the locking portion of the optical adapter in the axial direction, and thus the optical connector  1  is regulated from slipping off from the optical adapter. The latch  22  is pushed downward while being elastically deformed, and engagement between the locking surface  22   a  and the locking portion of the optical adapter is released. Consequently, the optical connector  1  can be detached from the optical adapter. 
         [0037]    In the optical connector  1 , in order to reliably bring the forward end of the ferrule  10  of the optical connector  1  on one part into contact with a ferrule of an optical connector on the other part connected thereto through the optical adapter, it is necessary to set a projecting amount of the capillary  11  with respect to the housing  20  within a range defined by a predetermined standard. Specifically, as illustrated in  FIG. 2A , it is necessary to set an axial length L 1  between a forward end  11   b  of the capillary  11  and the reference surfaces  32   c  of the housing  20 , and an axial length L 2  between the reference surfaces  32   c  and the locking surface  22   a . As in this embodiment, when the locking surface  22   a  and the reference surfaces  32   c  are die-molded integrally with the housing  20 , those surfaces can be finished with high dimensional accuracy. Thus, it is possible to set the projecting amount of the capillary  11  with respect to the housing  20  with good accuracy. 
         [0038]    The cover portion  23  covers the outer periphery of the cylinder portion  12   f  of the ferrule  10  projecting to the proximal end side relative to the main body  21 , and extends to the proximal end side beyond the proximal end of the cylinder portion  12   f . In the illustrated example, a pair of long plate-like members provided above and below the cylinder portion  12   f  constitute the cover portion  23 . As in the illustrated example, the cylinder portion  12   f  and a connecting portion connected to the optical fiber are covered with the protective tube  13 , and the cover portion  23  protects the connecting portion from above and below. Thus, it is possible to prevent a situation in which the optical fiber (not shown) is bent at an entrance portion (proximal end) of the cylinder portion  12   f  when operating the latch  22 . 
         [0039]    The optical connector  1  having the above-mentioned configuration is assembled as follows. First, an adhesive is applied to the inner periphery of the ferrule  10  mounted with the protective tube  13 , and the adhesive is cured after the optical fiber (not shown) is inserted through the inner periphery of the ferrule  10  applied with the adhesive. Consequently, the ferrule  10  and the optical fiber are integrated together. In this state, after eliminating a portion of the optical fiber sticking out of the forward end  11   b , the forward end  11   b  of the capillary  11  is polished and finished with high accuracy. The ferrule  10  thus formed is inserted in the inner periphery of the through-hole  30  from the opening portion formed in the side surface of the main body  21  of the housing  20 . Specifically, while guided by cutout portions  21   a   1  provided at the ends on the opening side of the protrusions  21   a , the smaller-diameter outer peripheral surface  12   d  of the capillary holding portion  12  of the ferrule  10  is pushed in between the pair of upper and lower protrusions  21   a  provided on the inner peripheral surface of the through-hole  30 , and is press-fitted therebetween while elastically deforming the housing  20  and expanding the space between the protrusions  21   a . When the smaller-diameter outer peripheral surface  12   d  reaches the partially-rounded inner surface  32   d  located at the deep portion in the width direction, the housing  20  is elastically restored, and the partially-rounded inner surface  32   d  is held in close contact with the smaller-diameter outer peripheral surface  12   d . Thus, the ferrule  10  is held by the housing  20  (see  FIGS. 3B and 3D ). In this way, in order that the housing  20  is deformed within its elastic range when the ferrule  10  is mounted to the housing  20 , a diameter of the smaller-diameter outer peripheral surface  12   d  of the ferrule  10  and the space between the upper and lower protrusions  21   a  are appropriately set. As a result, the ferrule  10  is detachably attached to the housing  20 , and to easily perform a centering operation described below. Note that, the forward end  11   b  of the capillary  11  may be polished not only before the ferrule  10  is mounted to the housing  20  as described above but also after the ferrule  10  is mounted to the housing  20 . However, in comparison with a case where the ferrule  10  is polished while being assembled to the housing  20 , a backlash during polishing and assembly tolerance between members are more likely to be suppressed and polishing with higher accuracy can be attained in a case where the ferrule  10  is polished alone as described above. Therefore, it is possible to finish the forward end  11   b  with higher accuracy. 
         [0040]    Then, the centering operation is performed. Specifically, in a state in which the ferrule  10  is mounted to the housing  20 , a fiber core is connected to an optical connector (not shown) being eccentric in a predetermined direction (upward direction, for example), and splice loss in connection is measured. Then, the ferrule  10  is detached from the housing  20 , and rotated by a predetermined angle (60°, for example). The ferrule  10  is re-mounted to the housing  20 , and the splice loss is measured. The above-mentioned operation is repeated. An eccentric direction of the fiber core of the optical connector  1  is considered to be most close to the predetermined direction (upward direction, for example) when the splice loss becomes lowest, and the ferrule  10  is mounted in this direction. With the above-mentioned operation, assembly of the optical connector  1  is completed. Note that, a centering method is not limited to the above-mentioned one. For example, centering may be performed after the splice loss is measured in the ferrule  10  alone and the eccentric direction of the fiber core is ascertained. Thereafter, the ferrule  10  may be mounted to the housing  20 . 
         [0041]    As described above, in the optical connector of the present invention, the side surface of the housing  20  is opened, and hence the ferrule  10  can be mounted to the housing  20  with one-touch operation. The optical connector can be preferably used on a place where the optical connector is rarely subjected to external impact (in an inside of a module box, for example). On such place, it is less necessary to protect the optical fiber with a resin jacket or the like, and the optical connector can be used in a state in which the optical fiber is exposed. As a matter of course, there may be used a so-called optical cable in which the optical fiber is protected with the resin jacket or the like and a reinforcing fiber is interposed between the resin jacket and the optical fiber. 
         [0042]    The present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, as illustrated in  FIG. 4 , though the gap is formed between the partially-tapered inner surface  32   a  of the holding hole  32  of the housing  20  and the tapered surface  12   b   2  of the ferrule  10 , those surfaces may be brought into contact with each other (not shown). In this case, in a state in which the reference surfaces  32   c  are elastically deformed, the ferrule  10  is brought into contact with the housing  20  from the proximal end side of the flange portion  12   b , and the flange portion  12   b  is sandwiched between the partially-tapered inner surface  32   a  and the reference surfaces  32   c  of the housing  20  from the both sides in the axial direction. As a result, the ferrule  10  can be reliably held by the housing  20 . 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  optical connector 
           10  ferrule 
           11  capillary 
           12  capillary holding portion 
           12   b  flange portion 
           13  protective tube 
           20  housing 
           21  main body 
           21   a  protrusion 
           22  latch 
           22   a  locking surface 
           23  cover portion 
           30  through-hole 
           31  larger-diameter hole 
           32  holding hole 
           32   a  partially-tapered inner surface 
           32   b  partially-angled inner surface 
           32   c  reference surface 
           32   d  partially-rounded inner surface

Technology Classification (CPC): 6