Optical fiber ferrule holding plate for optical fiber end polishing apparatus

Abstract: An optical fiber ferrule holding plate for an optical fiber end polishing apparatus for simultaneously polishing the end surfaces of a plurality of ferrules (17) with optical fibers (16) permits further improved durability and workability. The optical fiber ferrule holding plate is constructed by a ferrule outer periphery supporting member (14) which is made of a hard burned ceramic member provided, at the center thereof, with an inserting hole (15) for receiving the end outer periphery of the ferrule (17) with an optical fiber (16) and which receives and supports a plurality of ferrules (17) with optical fibers (16); a holding plate main unit (12) which has a plurality of through holes (13) for receiving a plurality of ferrule outer periphery supporting members (14) and which receives, fixes, and supports the ferrules (17) with optical fibers (16) in the through holes; and means (18 - 22) for detachably holdling the ends of the ferrules (17, 17a) with optical fibers (16), which have been inserted in the members (14) for supporting the outer peripheries of the ferrules (17) with optical fibers (16), toward a polishing board.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for simultaneously polishing, using a polishing board, the end surfaces of a plurality of ferrules each retaining an optical fiber according to the preamble of claim 1. 2. Description of the Related Art There have been proposed many optical fiber end surface polishing apparatuses for polishing a plurality of optical fiber end surfaces at the same time. Takahashi, who has achieved the present invention, has many filed applications for optical fiber end surface polishing apparatuses and has acquired U.S. Patent No. 4979334 ("Polishing apparatus for end faces of optical fibers") and U.S. Patent No. 5216846 acquired on June 8, 1993 ("Method and apparatus for grinding foremost end surface of a ferrule"). The aforesaid optical fiber end surface polishing apparatuses are designed to hold an optical fiber ferrule with a plurality of optical fibers thereto in an optical fiber ferrule holding plate and cause relative movement based on circular motion between a polishing board and the distal end of the optical fiber ferrule, thereby polishing the distal end of the optical fiber ferrules together with the optical fibers. The inventor has filed an application for "Optical fiber end polishing apparatus for polishing a plurality of types of optical fibers" (EP-A-0 705662 Published 10.04.1996) on a polishing apparatus equipped with an improved optical fiber ferrule holding plate for holding a plurality of optical fiber ferrules with optical fibers attached thereto in order to accomplish higher operation efficiency of the aforesaid polishing apparatuses. This apparatus displays the features of the preamble of claim 1 of present application Fig. 4 is a top view schematically showing the principle of the optical fiber ferrule holding plate which can be used for the optical fiber end polishing apparatus stated above. Fig. 5 is a front cross-sectional view showing a part of the optical fiber ferrule holding plate for the optical fiber end polishing apparatus illustrated in Fig. 4. A cylindrical hub 2 to be coupled to a holding shaft (not shown) is provided at the center of a holder plate main unit 1. A plurality of ferrule fixing sections 3 with optical fibers of the same type are provided on a concentric circle of the holder plate main unit 1. A cross-sectional view A-A' of Fig. 5 shows the details of the ferrule fixing section 3 with a single optical fiber attached. A plurality of FC type ferrules 5 with optical fibers 4 are fixed by the fixing sections 3 and end surfaces 6 of the optical fiber ferrules are pressed against a polishing board 11 at a right angle. Provided at the center of a ferrule receiving cylindrical bushing mounting member 8 of the fixing section 3 is a through hole 7 through which the ferrule 5 is inserted, an external screw 8a being provided on the outer periphery thereof. A box nut 9 is provided with a slit 10 and an internal thread which engages with the external thread 8a so as to tighten and fit the optical fiber ferrule onto the cylindrical bushing mounting member 8. Even with the optical fiber ferrule holding place for the optical fiber end polishing apparatus stated above, in order to polish smaller optical fiber ferrules, the fixing sections need to be installed densely on the disc and the slitted box nut 9 and the like must accordingly be made smaller. This has led to a problem in that the box nut 9 or the like tends to be lost during work; and installing or removing a single fixing section with the screw takes 10 to 20 seconds. Currently, a major optical connector ferrule measures 2.5 mm in outside diameter and 8 mm in effective length. With the increasing trend toward smaller optical circuit systems, however, an optical connector ferrule which is as small as half the size of one currently available has been developed and it is being put to practical use. In such a small optical connector ferrule, the screw-tightening structure becomes so small that it is difficult to handle. This prevents a ferrule with an optical fiber attached thereto from being fixed to the polishing holder by the conventional screw-tightening method. Furthermore, the squareness or an error in the tilt angle of the end surface of a polished ferrule with an optical fiber with respect to the central axis seriously affects the connecting performance of the optical fiber connector. The angle of the end surface is known to depend on the gap between the through hole in the mounting member and the outer periphery of the ferrule. If the allowable angle error is taken as 0.2 degree, then the gap has to be designed and manufactured to satisfy one tenth thereof, namely, approximately 0.02 degree. Hence, when the ferrule supporting length of the through hole in the mounting member is 5 mm, the allowable gap is 2 µm in diameter. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical fiber end polishing apparatus having an optical fiber ferrule holding plate for polishing thin and Short optical fiber ferrules with improved accuracy. The invention makes us of the following observation. Normally, stainless steel which is hardened to about 52 to 60 in Rockwell hardness is used for the material of the mounting member from the aspect of workability. It is practically impossible to completely avoid the adherence of hard diamond or green carborundum powder, which is used as the abrasive, in the gap. It is accordingly impossible to avoid the deterioration in the end surface polishing accuracy with time due to the wear from scratches on the wall surface of the through hole 7 in the fixing section. According to the invention, the object is achieved by an apparatus with the features of claim 1. The through holes for receiving the ferrule outer periphery supporting members can be provided at a right angle or at any angle with respect to a polishing surface. The holding means can be rotated around a shaft provided on the polishing holder plate surface and it may be comprised of a holding plate which is urged downward by a spring. The through holes for receiving the ferrule outer periphery supporting members can be provided in a ferrule outer periphery supporting member mounting plate which is fixed integrally at an arbitrary angle with respect to the optical fiber ferrule holding plate for an optical fiber end polishing apparatus. The ferrule outer periphery supporting member mounting plate can be provided with a threaded section for the means for detachably holding the end of a ferrule with an optical fiber toward a polishing board. Preferably, the hardness of the hard ceramic burned member constituting the ferrule outer periphery supporting member is 1000 or more in Vickers hardness. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a top view showing a part of an embodiment of an optical fiber ferrule holding plate for an optical fiber end polishing apparatus in accordance with the present invention; Fig. 2 is a front cross-sectional view of the section of the embodiment mentioned above; Fig. 3 is a front cross-sectional view showing a part of another embodiment of the optical fiber ferrule holding plate for an optical fiber end polishing apparatus in accordance with the present invention; Fig. 4 is a top view showing an optical fiber ferrule holding plate for an optical fiber end polishing apparatus in accordance with a previous application filed by the inventor. Fig. 5 is a front cross-sectional view showing a part of the optical fiber ferrule holding plate for an optical fiber end polishing apparatus illustrated in Fig. 4. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in further detail with reference primarily to the accompanying drawings. Fig. 1 is the top view showing a part of a first embodiment of the optical fiber ferrule holding plate for an optical fiber end polishing apparatus in accordance with the present invention; and Fig. 2 is a front cross-sectional view of the section of the embodiment mentioned above. A holder plate main unit 12 made of a thin plate is provided with a plurality of through holes 13 for receiving ferrule receiving members 14 on a concentric circle. Provided at the center of the ferrule receiving member 14 is a ferrule inserting hole 15. The ferrule receiving member 14, which is made of a burned zirconia ceramic material with Vickers hardness of 1800, is press-fitted in or fixed with an adhesive to the through hole 13 of the holder plate main unit 12. A ferrule 17 with an optical fiber 16 is inserted in the aforesaid through hole. A fixed shaft 18 is mounted perpendicularly to a polishing holder plate 12 with a screw adjacently to the ferrule receiving member 14. A ferrule holding plate 19 has a hole 21, through which the fixed shaft 18 is inserted, at the center thereof and a cylindrical rotary knob 20 on the head thereof. The ferrule holding plate can be horizontally turned around the fixed shaft 18 and it is provided with a hole 21, through which the cylindrical rotary knob 20 and the fixed shaft 18 are inserted, at its center. A compression coil spring 22 is provided between the rotary knob 20 and the fixed shaft 18. To fix the ferrule 17 with an optical fiber attached, the rotary knob 20 is lifted and the holding plate 19 is placed as shown in the broken line indicated by a line A-A in Fig. 1. With the holding plate set in this position, the ferrule 17 with an optical fiber is inserted in the hole 15. Then, the rotary knob 20 is moved up again and the holding plate 19 is turned until it reaches position B-B where an outer edge section 23 of the holding plate 19 is flush with the top surface of a flange 17a of the ferrule 17 with the optical fiber. This causes the bottom surface of the outer edge section 23 of the holding plate 19, which is pressed downward by the compression spring 22, to uniformly clamp and fix each ferrule 17 with the optical fiber independently onto the holder plate main unit 12. Fig. 3 is the front cross-sectional view showing a part of another embodiment of the optical fiber ferrule holding plate for an optical fiber end polishing apparatus in accordance with the present invention. In this embodiment, a through hole 25 for receiving and supporting a cylindrical ferrule outer periphery supporting member 26 is provided in a ferrule outer periphery supporting member mounting plate 24. The ferrule outer periphery supporting member mounting plate 24 is made of stainless steel which is hardened to about 52 to about 60 in Rockwell hardness. The cylindrical bushing 26 made of a burned zirconia ceramic material having Vickers hardness of 1800 is press-fitted in the central hole 25 and fixed by adhesion in advance. The ferrule outer periphery supporting member mounting plate 24 is fixed, with screws 29, 29, in a hole 28 provided in the holding plate main unit 27. The installing angle of the ferrule outer periphery supporting member mounting plate 24 with respect to the holder plate main unit 27 is determined by machining. Thus, this embodiment is suitably used for polishing a screw-tightened JIS F01 type optical connector by tilting it by an angle . A screw 30 provided on the ferrule outer periphery supporting member mounting plate 24 is an external screw which engages with a coupling nut of the optical connector. This screw and the coupling nut of the optical connector together constitute the holding means in this embodiment, so that the main unit does not need any other holding means. As described above in detail, the holding plate for polishing the end surfaces of a ferrule with an optical fiber in accordance with the present invention uses a hard burned ceramic member (e.g. burned zirconia ceramic material having Vickers hardness of 1000 or more) for the mounting member for the ferrule with the optical fiber. This makes the wall surface of the through hole less prone to the wear from scratches caused by the adhesion of abrasive powder even after a great number of polishing cycles are performed over an extended period of time, thus enabling stable polishing quality for the end surfaces of optical fibers to be maintained. Moreover, turning the spring-loaded holding plate permits easy fixing of the ferrule with the optical fiber to the polishing holder. This method is ideally used especially for mounting and fixing an extremely small ferrule with an optical fiber. The coupling nut of the optical connector shown in the second embodiment is provided for each optical connector and it is hard to be lost. Hence, it is extremely reasonable to use such a coupling nut.

Claims: An apparatus for simultaneously polishing, using a polishing board, the end surfaces of a plurality of ferrules (17) each retaining an optical fiber (16) comprising: a holder plate (12; 27) having a plurality of through holes (13; 28); a plurality of supporting members (14; 26), each being fixed and secured in a respective through hole (13; 25) and supported by said holder plate (12; 27), each supporting member having a through hole (15) at a center thereof for receiving an end portion of a respective ferrule (17) so as to support the ferrule at an outer periphery thereof; and means for detachably holding the ferrules (17) within the respective supporting members; characterized in that said supporting members (14; 26) are comprised of a hard burned ceramic material. The apparatus according to claim 1 wherein the through holes (13) within said holder plate (12) are arranged at a right angle relative to a surface of the polishing board; and said means for detachably holding the ferrules (17) comprise: a shaft (18) connected to said holder plate (12); a ferrule holding plate (19) rotatably mounted to said shaft (18); and a spring (22) urging said ferrule holding plate (19) in a direction toward the polishing board. The apparatus according to claim 1, wherein the through holes (28) within said holder plate (27) are arranged at an arbitrary angle relative to a surface of the polishing board; and said means for detachably holding the ferrules comprise: a plurality of mounting plates (24) integrally fixed to said holder plate (27) at an arbitrary angle, each being located within a respective through hole (28) of said holder plate (27) and each having a through hole (25) for receiving a respective supporting member (26). The apparatus according to claim 3, wherein each of said mounting plates (24) includes a threaded section (30) for receiving a respective nut. The apparatus according to any of claims 1 to 4, wherein the hard burned ceramic material has a Vickers hardness of at least 1000.

Inventors: TAKAHASHI MITSUO, TAKAHASHI, MITSUO
Applicants: SEIKO GIKEN KK, SEIKOH GIKEN CO., LTD.
Application year: 1995
Main classification: B24B19
IPC codes: G02B6, B24B19