Plastic-clad optical fiber

Details Plastic-clad optical fiber Plastic-clad optical fiber

1996-06-28

1997-07-29

Healy, Brian

Optical waveguides

Having particular optical characteristic modifying chemical...

Of waveguide cladding

385123, 385144, 385141, 5263297, G02B 600, C08F12018

Patent

active

056528213

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

This application claims benefit of international application PCT/JP95/02221, filed Oct. 31, 1995.


FIELD OF THE INVENTION

The present invention relates to a plastic-clad optical fiber.


RELATED ART

As a cladding material of a plastic-clad optical fiber, a silicone resin has hitherto been known (Japanese Patent Kokai Publication No. 30703/1983). However, this cladding material can not cope with the recently required simplification of a terminal processing by attachment of a crimp connector because of lack of a mechanical strength. On the other hand, as disclosed in Japanese Patent Kokai Publication No. 250047/1987, U.S. Pat. No. 4,707,076, Japanese Patent Kokai Publication Nos. 166206/1991 and 32749/1993, cladding materials comprising an ultraviolet curing resin composition are suggested. These resin compositions are superior in mechanical strength, because they have a crosslinked structure due to ultraviolet curing, and the crimp connector can be applied to an optical fiber comprising the resin composition as the cladding material. There is also an advantage that a production speed is improved when using these cladding materials.
Japanese Patent Kokai Publication No. 32749/1993 discloses that the content of fluorine is increased by incorporating a novel compound having a fluoroalkyl group and a urethane group into a cladding material to sufficiently decrease a refractive index.
However, the resin composition of Japanese Patent Kokai Publication No. 32749/1993 can give a low refractive index, but it has been found that a sufficient performance of the optical fiber (e.g. transmitting capability) can not be obtained if NA (numerical aperture) as a parameter representing a light coupling efficiency to a light source element in an optical fiber having the cladding material formed from these resin compositions is not within a specified range according to the type and diameter of a core material as well as the type of a resin composition used as the cladding material.
The structure NA of the optical fiber is represented by the following formula: ##EQU1## wherein n.sub.1 is a refractive index of a core; and n.sub.2 is that of a cladding material.
Accordingly, the refractive index of the core may be increased or that of the cladding material may be decreased in order to increase NA.
However, a transmission band of the optical fiber becomes small when NA is increased much so as to efficiently introduce light from a light source into the optical fiber. As a result, it becomes impossible to conduct high-speed transmission. Accordingly, NA of the optical fiber must be within a suitable range.


SUMMARY OF THE INVENTION

An object of the present invention is to provide a plastic-clad optical fiber having high NA, wherein the high-speed transmission and the application of a crimp connector can be conducted.
The present invention provides a plastic-clad optical fiber comprising a core formed from quartz or optical glass and a cladding material formed from a plastic having a refractive index lower than that of the core, wherein the cladding material comprises a cured material of a resin composition containing a urethane di(meth)acrylate represented by the general formula (I): ##STR2## wherein X is a hydrogen atom or a methyl group; R is an alkyl group, an aryl group or a cyclic alkyl group; aperture (NA) is in the range from 0.43 to 0.52.


BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an IR spectra chart of the product obtained in Preparative Example 1.
FIG. 2 is an IR spectra chart of the product obtained in Preparative Example 2.
FIG. 3 is an IR spectra chart of the product obtained in Preparative Example 3.
FIG. 4 is an IR spectra chart of the product obtained in Preparative Example 4.
FIG. 5 is an IR spectra chart of the product obtained in Preparative Example 5.
FIG. 6 is an IR spectra chart of the product obtained in Comparative Preparative Example 1.


DETAILED DESCRIPTION OF THE INVENTION

With respect to R in the general formula (I), the number of carbon atoms in the alkyl group is preferably from 1 t

REFERENCES:
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patent: 4779954 (1988-10-01), Tatsukami et al.
patent: 4787709 (1988-11-01), Kawada et al.
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patent: 5111526 (1992-05-01), Yamamoto et al.
patent: 5117480 (1992-05-01), Yamamoto et al.
patent: 5479555 (1995-12-01), Rot et al.
patent: 5491770 (1996-02-01), Bonafini, Jr.

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