Patent
1986-04-04
1989-04-04
Sikes, William L.
350 962, G02B 638
Patent
active
048180610
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical connector for connecting optical fibers on their ends which are used as a transmission medium in optical communication and to a "ferrule" which is a component part of an optical connector used to sheath the ends of optical fibers.
2. Description of the Prior Art
Optical fibers with excellent transmission characteristics such as high band and low loss have been extensively used recently as a medium in transmission of data and photo-energy. Along with such development, there is keenly felt demand for a method for connecting optical fibers of the diameter of ca. 0.1 mm which are often used for high speed data transmission with low coupling loss at low cost.
Since optical fibers are thin and fragile, connecting optical fibers requires technology more sophisticated than in electric connection. More specifically, in order to connect optical fibers at a coupling point at lower energy loss, it is necessary to align optical axes of two optical fibers at precision of several microns so as to have less gap between interfaces thereof. (This is referred to as alignment of optical axes.)
Conventional methods for connecting optical fibers are outlined, for example, in Technical Stuff of CSELT: "OPTICAL FIBER COMMUNICATION," pp. 541-643, especially pages 571-602 1980, McGraw-Hill New York. They are roughly classified into two: the one which permanently connects optical fibers and the other which employs a connector to allow connection and disconnection of optical fibers. As the present invention is intended for connection between equipments, it relates to the latter category method which connects optical fibers by means of a connector in a manner to allow detachment.
Structure of such optical connectors in the prior art generally comprises ferrules and a sleeve such as shown in Japanese Patent Publication No. Sho 55-22707. The ferrule is tubular and has a circular section which is axially bored a throughhole having a slightly larger diameter than the outer diameter of an optical fiber for receiving the same. A sleeve is a cylindrical member for accurately abutting two ferrules. Optical fibers are connected by inserting terminals of two optical fibers into throughholes on the ends of ferrules respectively, aligning and fixing end faces thereof and the ferrules on the same plane, and inserting the ferrules into a sleeve to abut end faces of the ferrules on each other.
In such structure of optical fiber connection, if there is angular or axial deviation between the optical fibers, coupling loss is increased. In order to achieve excellent connection at low coupling loss, axial or angular deviation should be kept to minimum. Conventional ferrules are designed as rigid bodies to avoid distortion which may lead to axial and regular deviation of the optical fiber axis to thereby prevent any increase in coupling loss. Favorable characteristics of optical fibers such as smaller diameter and flexibility are therefore not fully utilized.
An example of conventional ferrules is shown in FIG. 1. A ferrule 1 is made of stainless steel and comprises a cylindrical part 2 and a flange 3. The diameter D of the cylindrical part 2 (hereinafter referred to as "outer diameter of a ferrule") is 2.5 mm and the length L of the cylindrical part from the flange 3 to an end 4 of the ferrule (hereinafter referred to as "length of a ferrule cylinder) is 8.0 mm. A capillary 7 made of ceramics with a precision bore hole 6 is fitted into the tip end of the cylindrical part 2. The spring constant when fixed as shown in FIG. 2 and deformed by the stress applied on the tip end 4 becomes approximately 20 kg/mm, suggesting the high rigidity of the ferrule. The weight applied at breaking is ca. 10 kg. Displacement at the tip end even at this time is less than 0.1 mm. FIG. 3 shows another type of ferrule of a similar shape to the one shown in FIG. 2. However, this ferrule is not provided with a capillary and made of plastics (PPS resin containing a reinforcing agent
REFERENCES:
patent: 4090778 (1978-05-01), Phillips et al.
patent: 4264128 (1981-04-01), Young
patent: 4362356 (1982-12-01), Williams et al.
patent: 4458983 (1984-07-01), Roberts
patent: 4556282 (1985-12-01), Delebecque
patent: 4579419 (1986-04-01), Scrivo
Sixth European Conference on Optical Communication, York, England, (Sep. 16-19, 1980) LeNoane et al., pp. 330-334, "Progress in Low-Loss Interconnection System Design".
Optical Fibre Communication-Technical Staff of CSELT-Torino, Italy-pp. contents, 541-643.
Ando Yasuhiro
Iwano Shin'ichi
Ngo John
Nippon Telegraph and Telephone Corporation
Sikes William L.
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