Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Patent
1996-11-22
1998-03-31
Healy, Brian
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
385142, 385143, 385145, 385123, G02B 602
Patent
active
057347735
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a multicore plastic optical fiber for light signal transmission which has low transmission loss in a broad transmission bandwidth and does not experience greatly increased transmission loss even during bending of the fiber.
BACKGROUND OF THE INVENTION
Heretofore, a plastic optical fiber cable prepared by covering a single core plastic optical fiber with a thermoplastic resin such as polyethylene, by thinly covering a core having a diameter of about 0.5 to 1.5 mm with a cladding material in a concentric configuration, is employed for optical communication. Plastic Optical Fiber and Applications Conference '92, PROC., 3 (1992) reports that conventional step index type single core plastic optical fibers have a transmission bandwidth of 40 MHz when the fiber length is 100 meters and the launch numerical aperture of the light source is 0.65. However, when the light source launch numerical aperture is collimated to 0.01, its transmission bandwidth becomes 115 MHz in the case of a 100-meter long fiber.
A bundle cable prepared by covering a bundle of some tens of thin plastic optical fibers having a diameter of 0.125 to 0.25 mm with a thermoplastic resin has been also applied to practical use. Since the fibers composing the bundle cable are not fused each other, they shift and make the end of the cable uneven. As a result, the light capacity of the cable is considerably reduced. Further, when a bundle cable comprising plastic fibers having a small diameter is used, the optical fibers are easily snapped or transmission loss greatly increases when the cable is covered with a thermoplastic resin.
Japanese Patent Application Laid-Open No. 265606/1987 discloses a single core plastic optical fiber using a methacrylate fluoride type copolymer and the like as a cladding material. This fiber has a relatively small transmission bandwidth so that it is only applicable to short distance signal transmission at a low speed such as audio or factory automation (FA).
On the other hand, Japanese Patent Application Laid-Open No. 53035/1993 discloses a multicore plastic fiber for signal transmission comprising 500 or more cores which are made of a transparent resin possessing a high refractive index, and have a diameter of 50 .mu.m or less. This fiber minimizes changes in light capacity upon bending by making the core diameter 50 .mu.m or less.
Japanese Patent Application Laid-Open No. 341147/1993 discloses an multicore type single mode optical fiber about 5 meters long which efficiently links a silica optical fiber with a light source or a light receiving element and a transmission method using the fiber. Since this fiber satisfies the single mode transmission conditions, its core diameter is quite small, 5.3 .mu.m, when the difference of refractive indexes between the core resin and the cladding resin is 0.003 or more.
Some multicore optical fibers are put into practice as an image fiber, not as a fiber for light signal transmission. An image fiber transmits an image from one tip of the fiber to the other while maintaining a picture focused at one tip and a positional relation of optical strength patterns. Accordingly, the purpose of an image fiber is completely different from that of the light signal transmission fiber.
As described above, the conventional plastic optical fibers do not achieve simultaneously a low transmission loss at a broad transmission bandwidth and a small change in light capacity upon bending the fiber. In order to improve the conventional plastic optical fibers and develop a useful plastic optical fiber which is applicable to a middle-distance signal transmission at a high speed such as a local area network (LAN), the present inventors carried out extensive and intensive studies and accomplished the present invention.
DISCLOSURE OF THE INVENTION
The present invention relates to a multicore plastic optical fiber for light signal transmission comprising 7 or more cores having a diameter of 50 to 200 .mu.m which are covered with a cladding resin having a r
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Katsuta Shigeki
Munekuni Hajime
Teshima Shin'ichi
Asahi Kasei Kogyo Kabushiki Kaisha
Healy Brian
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