Abstract:
An optical fiber loading device includes a loading stage, which includes a first clamp block, fitted in a first opening defined in a first base portion, including first grooves adapted to position first optical fibers of a first optical fiber cable; and a first clamp arranged to releasably contact the first clamp block to clamp the first optical fibers therebetween, wherein the first clamp block and first base portion are formed of two different materials. The device also includes a first holder adapted to hold the first optical fiber cable, and to move the first optical fiber relative to the loading stage to bring the first optical fibers in contact with second optical fibers of a second optical fiber cable.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2004-172728, filed on Jun. 10, 2004 in the Japanese Patent Office, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to an optical fiber fusion splicer and an optical fiber loading device thereof, which provides highly precise alignment positioning of end faces of optical fibers, of optical fiber cables, to each other to be brought in contact for fusion splicing.  
         [0003]     Fusion splicing end faces of optical fibers of optical fiber cables to each other requires highly precise alignment positioning. Thus, a fusion splicer requires a V-groove block with a highly precisely machined V-groove. Positioning of the optical fibers of the optical fiber cables by the fusion splicer requires: (1) wear resistance; (2) heat resistance; (3) a small linear expansion coefficient; and (4) electric insulation.  
         [0004]     A related fusion splicer is disclosed in Japanese Examined Patent Application No. H07-43453. This fusion splicer includes a standing body frame for fusion splicing. The fusion splicer has, at the left and right portions of the body frame for fusion splicing, for example, leftward and rightward movable left and right fiber holders. The left and right holders have a lower left fiber holder and a lower right holder; and an upper left holder and an upper right holder, respectively. The upper left holder and the upper right holder are vertically movable relative to the lower left fiber holder and the lower right holder using, for example, a hinge pin. The lower left holder and the lower right holder have surfaces that each has, for example, upward open rectangular grooves for holding, for example, an optical fiber ribbon cord with four optical fibers.  
         [0005]     The body frame for fusion splice inside the left fiber holder and the right fiber holder has a loading device located thereof. The loading device includes, for example, a resinous loading body frame on the body frame for fusion splice. The loading body frame has a recessed shape as viewed from front, with a recessed portion at the substantially central portion between the left and right and between the front and rear of the body frame. The recessed portion has, at the front and rear, holes communicating with the recessed portion. The loading body frame includes, thereon, a ceramic block identical in shape with a lower clamp, as viewed from top. The ceramic block has a recessed portion; and identically shaped holes positioned in coincidence with the hole. The loading body frame has, thereon, a ceramic block integrally adhered thereto using an adhesive.  
         [0006]     Ceramic block portions opposed to each other relative to the recessed portion in a left and right direction have surfaces with V grooves extended in the left and right direction. For clamping optical fibers exposed by removing sheaths from optical fiber ribbon cords, upper clamps are provided to be vertically movable relative to the ceramic blocks.  
         [0007]     The related fusion splicer has the following problems: (1) the ceramic block has a large size and expensive production costs; (2) the ceramic block has complicated machining and expensive production costs; and (3) poor adhesion causes the ceramic block to be separated form the body frame, thus putting the fusion splicer out of use.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     In a first aspect of the invention, an optical fiber loading device is provided, including: a loading stage, comprising: a first clamp block, fitted in a first opening defined in a first base portion, comprising first grooves adapted to position first optical fibers of a first optical fiber cable; and a first clamp arranged to releasably contact the first clamp block to clamp the first optical fibers therebetween, wherein the first clamp block and first base portion are formed of two different materials; and a first holder adapted to hold the first optical fiber cable, and to move the first optical fiber relative to the loading stage to bring the first optical fibers in contact with second optical fibers of a second optical fiber cable.  
         [0009]     In another aspect of the invention, an optical fiber fusion splicer is provided, including, in addition to the loading stage, a first electrode configured to discharge between the first and second optical fibers to fusion splice the first and second optical fibers to each other.  
         [0010]     In another aspect of the invention, the loading stage further comprises: a second clamp block, fitted in a second opening defined in a second base portion, comprising second grooves adapted to position the second optical fibers of the second optical fiber cable; and a second clamp arranged to releaseably contact the second clamp block to clamp the second optical fibers therebetween, wherein the second clamp block and second base portion are formed of two different materials.  
         [0011]     In other aspects of the invention, the first clamp block is formed of a material more brittle that the material of which the first base portion is formed, the first base portion is formed of a resinous material, and the first clamp block is formed of a ceramic material.  
         [0012]     In another aspect of the invention, a method of insert molding a loading stage for an optical fiber is provided, including: fitting a first clamp block to a mold; and filling a resin into the mold having the first clamp block fitted thereto to form a first base portion around the first clamp block.  
         [0013]     In another aspect of the invention, the first grooves in the first clamp block are formed after the first clamp block is insert molded to the first base portion.  
         [0014]     In another aspect of the invention, the first grooves in the first clamp block are formed before the first clamp block is insert molded to the first base portion.  
         [0015]     According to the aspects of the invention, the clamp blocks are not adhered to the loading stage as a conventional way, which eliminates the step of adhering the clamp block, thus reducing production costs. The aspects avoid peeling or separation of the clamp block from the loading stage, thus ensuring necessary precision.  
         [0016]     The aspects allows for the clamp block smaller in size than conventional one, and achieves remarkable reduction in costs. In addition, the aspects simplify machining of the clamp block, thus reducing production costs. 
     
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0017]     The above and other objects, features and advantages of the invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
         [0018]      FIG. 1  is a perspective view of a fusion splicer according to the invention;  
         [0019]      FIG. 2  is a plane view of the fusion splicer in  FIG. 1 , where the cover is open;  
         [0020]      FIG. 3  is a plane view of the primary portion of the fusion splicer in  FIG. 1 ;  
         [0021]      FIG. 4  is an enlarged partial left side view of a first optical fiber holder in  FIG. 3 ;  
         [0022]      FIG. 5  is an enlarged partial sectional view taken along III-III in  FIG. 3 ;  
         [0023]      FIG. 6  is an enlarged view as viewed from the arrow IV;  
         [0024]      FIG. 7  is a perspective view of a brittle lower clamp block in  FIG. 6 ;  
         [0025]      FIG. 8  is a plane view of the primary portion of the fusion splicer in  FIG. 3 , where a clamp member is added; and  
         [0026]      FIG. 9  is a perspective view illustrating a mold for insert molding of the body frame in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0027]     Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way.  
         [0028]     With reference to  FIG. 1 , an optical fiber fusion splicer  100  (referred to as a fusion splicer) includes, on the top of a casing  110 , a fusion splicing system  1  covered with a cover  122 . The fusion splicer  100  includes a monitor  130  rotatably supported to casing  110 . The monitor  130  includes a display  131  to display process of fusion splicing optical fibers to each other. The fusion splicer  100  has groups of switches  111  and  112 . The fusion splicer  100  includes a carrier handle  140  mounted on the casing  110 .  
         [0029]     With respect to  FIG. 3 , the fusion splicing system  1  includes a standing body frame  3  for fusion splice. The fusion splicing system  1  includes, at the left and right portions on the body frame  3 , first and second fiber holders  5  and  7  movable, for example, in a left and right direction or a longitudinal direction L 1 . One of the first and second fiber holders  5  and  7  may be fixed, and the other one may be movable in the longitudinal direction L 1 . Additionally with respect to  FIG. 4 , the first and second fiber holders  5  and  7  include a first lower fiber holder  5 D and a second lower fiber holder  7 D; and a first upper fiber holder  5 U and a second upper holder  7 U, respectively. The first and second upper fiber holders  5 U and  7 U are vertically rotatable relative to the first and second lower fiber holders  5 D and  7 D using, for example, hinge pins  9 . The first and second lower fiber holders  5 D and  7 D have surfaces defining, for example, upward open rectangular grooves  15  and  17  that hold optical fiber ribbon cords  11  and  13  with, for example, four optical fibers as optical fiber cables, respectively.  
         [0030]     The fusion splicing system  1  includes a loading device  19  inside the first and second fiber holders  5  and  7  on the body frame  3 . The loading device  19  includes a loading body frame  21  or a loading stage of, for example, a resin on the body frame  3 . The loading body frame  21 , additionally with respect to  FIG. 5 , is formed with a recess  23  at the substantially central portion as viewed from front. The loading body frame  21  includes left and right rising portions  21 L and  21 R on both sides of the recess  23 . The rising portions  21 L and  21 R are arranged opposite to each other relative to the recess  23 . The portions of the rising portions  21 L and  21 R have upward open openings  25 L and  25 R as viewed from side. The loading body frame  21 , as illustrated in  FIGS. 6 and 7 , includes, within the openings  25 L and  25 R, lower clamp blocks  29 L and  29 R with surfaces having V-grooves  27  as grooves. The lower clamp blocks  29 L and  29 R are made of, for example, ceramics as a brittle material. The brittle material may employ a glass material as ceramics. In this embodiment, four V-grooves  27  extend in a longitudinal direction L 1 , allowing for clamp of the optical fibers  11 A and  13 A exposed by removing the sheaths of the optical fiber ribbon cords  11  and  13 .  
         [0031]     Referring to  FIG. 3 , the loading body frame  21  has, at the front and rear of the recess  23  in a transverse direction T 1 , holes  31  and  33  communicating with the recess  23 . The recess  23  and openings  25 L and  25 R communicate with each other. As illustrated in  FIG. 6  and  8 , the loading device  19  includes upper clamps  35 L and  35 R vertically movable relative to the lower clamp blocks  29 L and  29 R of ceramics.  
         [0032]     In  FIG. 3 , the fusion splicing system  1  includes, for example, discharge electrodes  39  and  41  as fusion splicing means  37  arranged in the transverse direction T 1 , with the recess  23  between the lower clamp blocks  29 L and  29 R interposed therebetween. The discharge electrodes  39  and  41  have respective ends opposed to each other in the recess  23 . The holes  31  and  33  have at the lower portions, check holes  43  and  45  to which, for example, a CCD camera is mounted for checking contact state and fusion splice state between the optical fibers  11 A and  13 A. The loading body frame  21  has, on both sides of the lower clamp blocks  29 L and  29 R in the transverse direction T 1 , positioning holes  47  for use of positioning pins during insert molding.  
         [0033]     The very small lower clamp block  29 L and  29 R, as illustrated in  FIG. 7 , have, for example, a square section with a length L of 8 mm, a width W of 8 mm, and height H of 2 mm.  
         [0034]     Next, a method of fabricating the resinous loading body frame  21  will be described. As illustrated in  FIG. 9 , a mold  50  includes base  51 ; and a recess  53  at the central portion of the base  51 . The mold  50  includes a block  55  projecting from the bottom of the recess  53 . The mold  50  includes two pair of pins  57  positioned on both sides of the block  55  and projecting from the bottom of the recess.  
         [0035]     Ceramic blocks  52 A and  52 B as the lower clamp blocks  29 L,  29 R are fitted in the mold  50  to be positioned using the positioning pins  57 . A resin material for the loading body frame  21  is melted to pour into the recess  53  of the mold  50  for insert molding. The resin material is set around the ceramic blocks  52 A and  52 B, forming the loading body frame  21  having the lower clamp block  29 L and  29 R in the opening  25 L,  25 R. The block  55  is formed into the recess  23  and holes  31  and  33 . This process allows for easier and cheaper fabrication, thus achieving lower costs lower than related processes.  
         [0036]     For clamping the optical fibers  11 A an  13 A of the optical fiber ribbon cords  11  and  13 , the appropriate number of V-grooves  27  is formed after insert molding, which further enhances machining precision of the V-grooves comparing to conventional one. For clamping the optical fibers  11 A and  13 A of the optical fiber ribbon cords  11  and  13 , the V-grooves  27  may be pre-formed before insert molding.  
         [0037]     Next, a method of operating the optical fiber fusion splicer  100  will be described.  
         [0038]     In  FIG. 3 , the sheaths of the ends of two optical fiber ribbon cords  11  and  13  are removed to expose the bare optical fibers  11 A and  13 A. The optical fiber ribbon cords  11  and  13  are placed in the grooves  15  and  17  formed to the first and second fiber holders  5 D and  7 D of the first and second fiber holders  5  and  7 . When the first and second upper fiber holders  5 U and  7 U are rotated to move down to the first and second lower fiber holders  5 D and  7 D, the first and second upper fiber holders  5 U and  7 U and the first and second lower fiber holders  5 D and  7 D hold the optical fiber ribbon cords  11  and  13  therebetween, respectively. At this time, respective bare optical fibers  11 A and  13 A of the optical fiber ribbon cords  11  and  13  are placed in the grooves  27  formed to the lower clamp blocks  29 L and  29 R.  
         [0039]     In this state, when the upper clamp  35 L and  35 R are moved down as illustrated in  FIG. 8 , the lower clamp blocks  29 L and  29 R and the upper clamps  35 L and  35 R clamp the optical fibers  11 A and  13 A therebetween, respectively. In addition, for, example, the first fiber holder  5  are moved rightward, and the second fiber holder  7  are moved leftward in the longitudinal direction L 1  of  FIG. 3  to position the end faces of the bare optical fibers  11 A and  13 A at the contact position.  
         [0040]     In this state, arc discharge is performed between the discharge electrodes  39  and  41 . The arc discharge fuses the end faces of the bare optical fibers  11 A and  13 A to be fusion spliced to each other.  
         [0041]     Thus, the lower clamp blocks  29 L and  29 R of a brittle material and with V-grooves  27  are not adhered to the loading body frame  21  by conventional adhesive. This structure does not need the step of adhering the lower clamp blocks  29 L and  29 R of a brittle material and with the V-grooves  27 , reducing production costs. This structure eliminates peeling or separating of the lower clamp blocks  29 L and  29 R from the loading body frame  21  by poor adhesion, thus achieving necessary precision.  
         [0042]     This structure allows for the lower clamp blocks  29 L and  29 R of a brittle material and with the V-grooves  27  smaller in size than conventional one and achieves remarkable reduction in costs. In addition, this structure simplifies machining of the lower clamp blocks  29 L and  29 R of a brittle material and with the V-grooves  27 , thus reducing production costs.  
         [0043]     The invention is not limited to the above-described embodiment, and may be carried out with appropriately modified another embodiment. In the above-described embodiment, the optical fiber ribbon cords with four optical fibers are illustrated as an example. While, an optical fiber ribbon cord with a single optical fiber or another multiple optical fibers may be employed. As means for providing the lower clamp blocks  29 L and  29 R to the openings  25 L and  25 R, means such as press-fitting other than insert molding may be handled.  
         [0044]     Although the invention has been described above by reference to exemplary embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.