Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1999-07-30
2001-03-06
Ullah, Akm E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
Reexamination Certificate
active
06196732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical connector for establishing an optical connection by bringing the end surfaces of optical fibers into contact with each other, a method of making the same, and a ferrule for this optical connector.
2. Related Background Art
Conventionally known as a technique in this field is one disclosed in Japanese Patent Application Laid-Open No. 6-258552. The optical connector disclosed in this publication has a protruded portion at the center of the nose of its ferrule, and the fiber positioning hole for securing an optical fiber is formed so as to have an opening at the protruded portion. As a consequence, the protruded portion enables ferrules to come into close contact with each other, thereby realizing a stable PC (Physical Contact) connection with low optical loss.
Similarly, Japanese Patent Application Laid-Open No. 6-222247 discloses an optical connector capable of PC connections. In the method of making this optical connector, a spacer with thickness equal to the protruded length of the optical fiber is used. A pin of the spacer is initially inserted into a guide pin hole of the ferrule, and then the part of optical fiber projected from the nose surface of the spacer is ground until the grinder surface reaches the spacer. As a result, the end portion of the optical fiber can be projected from the nose surface of the ferrule in conformity with the thickness of the spacer.
SUMMARY OF THE INVENTION
Since the conventional connectors are configured as mentioned above, there have been problems as follows. Namely, when the end portion of the optical fiber is projected from the nose surface of the ferrule by a predetermined amount, extreme care should be taken so as not to grind the nose surface of the ferrule at the time of grinding the end surface of the optical fiber, and high-precision grinding control is necessary so as not to grind the end surface of the optical fiber in excess.
In view of such problems, it is an object of the present invention to provide an optical connector securing an optical fiber projecting therefrom by a predetermined amount, which is easy to make; a method of making the same; and an optical connector ferrule used in this optical connector.
In order to overcome the above-mentioned problems, the optical connector in accordance with the present invention is an optical connector in which at least one optical fiber is provided within a ferrule such that an end portion of the optical fiber projects from a nose surface of the ferrule; wherein the nose surface of the ferrule comprises a first portion and a second portion, the first portion having a flat surface at the front extremity of the ferrule and the second portion being shaped such that the optically connecting end portion of the optical fiber is protruded from the second portion to the extent of a hypothetical plane extended from the first portion.
In the optical connector ferrule in accordance with the present invention, on the other hand, the ferrule has an optical fiber positioning hole for receiving and securing an optical fiber, the nose surface of the ferrule has a first flat portion, the nose surface excluding the first flat portion is positioned nearer the ferrule than is a plane including the first flat portion, an opening of the optical fiber positioning hole on the nose surface is positioned excluding the first flat portion.
The method of making an optical connector in accordance with the present invention comprises: a step of inserting the fiber into said ferrule, the ferrule having a nose surface comprising a first flat portion at the front extremity of the ferrule, and the remaining portion excluding the first portion, such that the end portion of the fiber is projected from the nose surface of the ferrule beyond a hypothetical plane extended from the first portion; and a step of grinding an end face of the fiber while using the first portion as a reference surface until the surface of the first flat portion and the end surface of the fiber are flush with each other, such that the end portion of the fiber projects from the remaining portion by a predetermined length, so as to form an end surface.
Since the optical connector in accordance with the present invention is configured as mentioned above, connectors can tightly be connected together by use of the first flat portion, thus allowing a stable PC connection with low optical loss to be realized. Also, this optical connector can easily be made by the manufacturing method in accordance with the present invention mentioned above using the optical connector ferrule in accordance with the present invention. Namely, when securing the optical fiber to the ferrule, as the end surface of the optical fiber is ground, while being projected ahead of the first flat portion, with the front face of the first flat portion being used as a reference surface, i.e., as the grinder surface of a grinding jig is set parallel to the first flat portion and grinds the end surface of the optical fiber, the spacer conventionally needed at the time of grinding becomes unnecessary. Further, until the grinder surface reaches the first flat portion, the grinding force is small since the optical fiber is ground alone, whereby the grinding speed can be made sufficiently high. After the grinder surface has reached the first flat portion, by contrast, the first flat portion is ground together, whereby the grinding area suddenly enlarges, which drastically decreases the grinding speed of the optical fiber. As a result, in an optical connector which requires the amount of projection of the optical fiber to be controlled on the order of microns, a greater margin in terms of time is obtained at the moment when stopping the grinding operation, whereby the control becomes easier. Also, the position of the end surface of the optical fiber can always be made flush with the first flat portion. Therefore, it is preferred that the first flat portion be ground together with the end surface of the optical fiber in the final stage of the grinding step.
The second portion may has a flat surface parallel to the flat surface of the first portion. As a consequence, the amount of projection of the optical fiber can easily be controlled according to the distance between the flat surfaces of first and second portions.
The flat surface of the first portion may be formed so as to be perpendicular to an axis of the optical fiber, or tilted with respect to an axis of the optical fiber. When formed with a tilt, it is preferred that the angle which the normal line of the flat surface of the first portion forms with the axis of the optical fiber is 8 degrees. The second portion has a flat surface connected to the first flat portion at a predetermined angle. Alternatively, the second portion has a curved surface connected to the first flat portion.
In any of the above-mentioned configurations, a predetermined amount of an optical fiber can easily be projected at the time when making an optical connector, and a secure PC connection can be realized in thus made optical connector.
Preferably, the end surface of the optical fiber may have a substantially convex semi-spherical surface. This convex surface is achieved by buffing the end surface of the optical fiber. According to this convex surface, it is easy to achieve secure PC connection.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from thi
Kakii Toshiaki
Ohtsuka Kenichiro
Tamekuni Yoshikyo
Ueda Tomohiko
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
Ullah Akm E.
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