Optical waveguides – Optical fiber waveguide with cladding – Utilizing nonsolid core or cladding
Patent
1993-03-23
1995-11-28
Lee, John D.
Optical waveguides
Optical fiber waveguide with cladding
Utilizing nonsolid core or cladding
385115, 385126, 65393, 65401, G02B 620
Patent
active
054715539
DESCRIPTION:
BRIEF SUMMARY
Technical Field
The present invention relates to a multicore hollow optical fiber and a method for preparation thereof. More particularly, this invention is concerned with a multicore hollow optical fiber which can be used for a compact endoscope and an optical sensor in medical and measuring industries by arranging, in its hollow, an image optical fiber, a single optical fiber, optical parts such as a lens, an electric cord, electric parts such as an electrode and an electron element, fluid such as gas and liquid, a chemical reaction material and the like; and also with a method for preparation thereof.
Background Art
U.S. Pat. No. 4,806,289 discloses a hollow optical fiber comprising a hollow central part and a peripheral part wherein the first layer is a cladding layer; the second layer is a core layer; and the third layer is a cladding layer, as shown in FIG. 11 of the present specification. The hollow optical fiber is stiff and does not have bending properties because of its layer structure. Accordingly, the hollow optical fiber easily buckles by bending and it easily breaks by cracking. Further, a fiber is not easily inserted into the hollow part of the hollow optical fiber because the hollow optical fiber has low elasticity.
Japanese Patent Publication No. 211761/1969 proposes a method for preparing a multicore hollow optical fiber wherein many optical fibers 20 are arranged around stem 19 in the layer to form a fiber bundle as shown in FIG. 12 of the present specification. The fiber bundle is heated to soften the optical fibers and to fusion-bond the outer layer, and then it is wound up while drawing. In this specification, there is no description in regard to the quality of the optical fiber. However, when a plastic optical fiber is prepared according to the above-mentioned method, voids remain between each optical fiber even if the resultant fiber bundle is heated so as to completely fusion-bond each optical fiber. Therefore, a multicore hollow optical fiber obtained by this method is easily taken into pieces by bending. Further, light cannot easily pass through the fiber since the cladding and core resins are mixed up. Accordingly, there cannot be obtained a high quality multicore hollow optical fiber suitable for a medical endoscope, of which fibers have a high accuracy in a bore or an outside diameter of the hollow over one to several meters in length and do not unnaturally bend or break by bending. Further, this method for preparing the fiber has a shortcoming in high cost caused by its complicated producing steps.
On the other hand, U.S. Pat. No. 3,556,635 discloses a multicore plastic fiber having an islands-in-sea structure wherein a core resin constitutes islands and a cladding resin constitutes a sea. The multicore plastic fiber is obtained by extruding the melted core and cladding resins with a composite spinning die. However, this patent does not contain a description about a multicore hollow optical fiber. Also, a multicore hollow optical fiber obtained according to the above method has not yet been attained.
In Japanese Utility Model Application Laid-Open No. 109418/1986, an endoscope is disclosed as shown in FIGS. 13, 14A and 14B of the present specification. The endoscope comprises image fiber 14, cylindrical part 22, and a body. Cylindrical part 22 has image fiber 14 in its hollow and has a plurality of optical fibers 20 in its wall composed of molding compound 21. A part of cylindrical part 22, image fiber 14 and light guide 23 bundling a plurality of optical fibers 20 are coated with resin 25, and they form the body. However, the endoscope is not compact enough because of the difference in diameters between cylidrical portion 22 and the body. This difference is caused by the structure of the endoscope, that is, the endoscope comprises cylindrical portion 22 and light guide 23 which are coated with resin 25. The method for making the edge of light guide 23 bundling a plurality of optical fibers to the above-mentioned structure requires a long and complicated step to fabricate
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Asahi Kasei Kogyo Kabushiki Kaisha
Lee John D.
Palmer Phan T. H.
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