Abrading – Machine – Rotary tool
Reexamination Certificate
2000-03-03
2003-05-20
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S041000
Reexamination Certificate
active
06565423
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus and method of polishing a ferrule end face for an optical connector, and more particularly to a technique for use when polishing the end face of a ferrule mounted to the joining part of a optical connectors that join together optical fibers, whereby a plurality of ferrule end faces are polished at one time with a uniform pressure, thereby eliminating a polishing process step, so as to both simplify and reduce the cost of polishing the ferrule end faces for an optical connector.
2. Description of the Background Art
In contrast to splicing, which provides a permanent connection between optical fibers, an optical connector is a connection joining member enabling a removable connection between optical fibers. In the past, a variety of practical optical connectors have been developed to enable connection and disconnection between optical fibers. For example, in a known single-fiber optical connector, in order to achieve a joint with little axial skew or tilt angle, an optical fiber is inserted into the center of a ceramic ferrule (i.e., a tubular reinforcement bar used for joining), and adhered in place, after which the optical connector ferrule (hereinafter simply referred to as ferrule) is inserted into a hollow tube having a precise inner diameter, the ends of ferrules being butted up against one another and screwed together by means of threads on the outside thereof. Because of its superior connection characteristics, the above-noted type of optical connector is widely used in many optical communication fields.
In an optical connector as described above, because the ferrules are directly butted up against one another, it is important that the ends of the ferrules be precisely polished, so as to lower the connection loss. Because optical connectors are used throughout an optical communications system, it is important to be able to lower the cost of the optical connector by enabling polishing in a short period of time. That is, there is a need for a technique that not only achieves highly precise optical connector characteristics, but also one that polishes the ferrule ends of an optical connector manufacturable with a low cost.
In a conventional polishing apparatus for achieving a convex spherical surface at a ferrule end face, a polishing plate formed in a concave spherical shape was held fixed, and the ferrule was fixed so as to be perpendicular to the concave spherical surface of the polishing plate. By imparting to the ferrule precession movement, comprising undulation and rotation about the center of the concave spherical surface, or forward and reverse rotation combined with undulation movement, the contact point is caused to move, thereby polishing the ferrule end face. Because of this process, there was the problem of breakage of the optical fiber connected at the rear of the ferrule by the action of the rotation or undulating movement of the ferrule. Additionally, a polishing apparatus performing such processing not only requires the formation of a polishing plate on a concave spherical surface, but also requires a highly precise mechanism to impart rotational or undulating movement to the ferrule, thereby making the polishing apparatus costly.
In general, when a bare optical fiber is inserted into a ferrule and then held in place with an optical adhesive, there is a swelling up of excess hardened adhesive on the end face of the ferrule. Thus, it is necessary to remove this adhesive agent before polishing the ferrule end face into a conex spherical shape.
Given the above, the inventor proposed a ferrule end face polishing apparatus wherein a polishing plate is caused to move in a path that describes the outer contour of the petals of a flower, this path synthesized by the revolution and autorotation of an external-tooth gear in a planetary gear mechanism having an internal-tooth sun gear and an external-tooth planet gear combined with an XY stage. This polishing apparatus is disclosed, for example, in the Japanese Patent Laid-open Application publication H6-15556. According to this polishing apparatus, after removing hardened adhesive agent from the ferrule end face without imparting rotation or undulation movement to the ferrule, the ferrule end face is polished with high precision to a convex spherical shape.
In the above-noted optical connector ferrule polishing apparatus, however, the following problems remained.
(1) Because there is a buildup of hardened adhesive agent on the end face of the ferrule to be polished, the overall length of each ferrule is different. Using the above-noted optical connector ferrule end face polishing apparatus, a plurality of ferrules are mounted to one ferrule holding jig, and pressed up against the polishing plate with a single pressure-applying mechanism. As a result, because a plurality of ferrules are polished under pressure applied by a single pressure-applying mechanism, because of the difference in the overall length of the ferrules, the pressures applied to individual ferrules differ, resulting invariations in the shape of the end faces of the ferrules. It is therefore not possible to achieve the optimum end face shape for all the ferrules mounted in the single ferrule holding jig.
(2) At the beginning of the processing step, polishing starts from ferrules that are longer. For this reason, some polishing time is required until the lengths of all the ferrules are made uniform, thereby resulting in a worsening of polishing efficiency.
(3) Because polishing starts from ferrules that are longer, in the case of polishing a ferrule end face for an optical connector, in which the polished surface area is small, a high pressure is applied to the longer ferrules during processing. For this reason, there is a tendency for the exposed surface of the optical fiber in the ferrule to become work distorted or damaged, resulting in a worsening of optical characteristics, and in particular of reflection attenuation.
(4) In polishing with a conventional polishing apparatus, because the four steps of adhesive agent removal, rough polishing, medium finishing, and a finished polishing were required, the work efficiency was extremely poor. That is, with four polishing process steps, it is necessary to perform polishing at each process step by setting proper conditions, such as the polishing film material, grit diameter, thickness, hardness and thickness of a resilient material placed on the top surface of the polishing plate, pressure applied to the ferrule, and the polishing speed, thereby resulting in an increase in the required time and cost. Additionally, the use of a diamond grit for polishing made the polishing cost high.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an apparatus and method for polishing the end faces of a plurality of ferrules of an optical connector at one time, in which independent pressure-applying mechanisms are provided corresponding to the individual ferrules to press them up against a polishing plate, a uniform pressure being applied to the plurality of ferrules, enabling the simultaneous polishing of the end face of a plurality of ferrules with a uniform pressure.
Another object of the present invention is to provide a, polishing apparatus and method in which, by selecting the material of a polishing slurry included in a polishing film used in polishing by the polishing apparatus, it is possible to simplify the polishing process, without using costly diamond grit, thereby enabling both simplification and cost reduction in the polishing process.
According to an aspect of the present invention, as shown in
FIG. 1
, an apparatus for polishing an optical connector ferrule end face is provided, wherein relative motion is imparted between an optical connector ferrule
10
and a polishing plate
4
so as to polish the end face of the ferrule
10
of the optical connector to a concave spherical surface, this polishing apparatus comprising a polishing plate
4
, a polishing
Matsui Shinsuke
Matsunaga Kazuo
Ohira Fumikazu
Kilpatrick & Stockton LLP
Nippon Telegraph and Telephone Corporation
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