Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Reexamination Certificate
2003-06-02
2004-10-12
Lee, John R. (Department: 2881)
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
Reexamination Certificate
active
06804442
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The subject application is related to subject matter disclosed in the Japanese Patent Application No.2002-167680 filed in Jun. 7, 2002 in Japan and the Japanese Patent Application No.2002-167665 filed in Jun. 7, 2002 in Japan, to which the subject application claims priority under the Paris Convention and which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber and an optical fiber cable having a first jacket layer and the second jacket layer, and a method of manufacturing the same.
2. Description of the Related Art
Generally speaking, an optical fiber is composed of a fiber glass structure (bare fiber), a first jacket layer directly covering the external surface of the fiber glass structure, and a second jacket layer covering the external surface of the fiber glass structure through the first jacket layer.
The first jacket layer is made of a soft UV curable resin while the second jacket layer is made of a rigid UV curable resin. This is because, when an external force is applied to the optical fiber, the deformation of the entirety of the optical fiber is suppressed by the second jacket layer while the first jacket layer serves to suppress small deformation remaining after suppression by the second jacket layer for the purpose of protecting the fiber glass structure from the external force.
While the resin temperature of UV curable resins largely falls from the temperature when the rigid UV curable resin starts hardening to the temperature when the hardening is finished, the first jacket layer tends to thermally contract in the three-dimensional directions. Since the three-dimensional contraction of the first jacket layer is restricted between the fiber glass structure and the second jacket layer, the first jacket layer is subjected to tensile stress uniformly in the three-dimensional directions. In this case, the first jacket layer is subjected to tensile stress not only when the hardening is finished but also thereafter while the environmental temperature may be changed.
Accordingly, if the mechanical factors of the fiber glass structure, the mechanical factors of the first jacket layer and the mechanical factors of the second jacket layer are not appropriate, the average tensile stress of the three-dimensional tensile stress applied to the first jacket layer exceeds a predetermined destructive stress after hardening is finished resulting in voids or cracks in the first jacket layer. For this reason, the supporting condition of the fiber glass structure by the first jacket layer becomes unstable so that there occurs slight bending of the fiber glass structure resulting in transmission loss and the deterioration of the quality of optical fiber.
BRIEF SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, an optical fiber comprises: a fiber glass structure; a first jacket layer made of a soft curable resin and directly covering the external surface of said fiber glass structure; and a second jacket layer made of a rigid curable resin and covering the external surface of said fiber glass structure through said first jacket layer, wherein the mechanical factors of said fiber glass structure, the mechanical factors of said first jacket layer and the mechanical factors of said second jacket layer are selected in order that the Young's modulus of said first jacket layer is larger than the average tensile stress (&sgr;
r
+&sgr;
&thgr;
+&sgr;
z
)/3 as applied to said first jacket layer
5
while the resin temperature of UV curable resins largely falls from the temperature when the rigid UV curable resin starts hardening to the temperature when the hardening is finished.
In accordance with another aspect of the present invention, an optical fiber cable in which a plurality of optical fibers are bundled, each of said optical fibers comprises: a fiber glass structure; a first jacket layer made of a soft curable resin and directly covering the external surface of said fiber glass structure; and a second jacket layer made of a rigid curable resin and covering the external surface of said fiber glass structure through said first jacket layer, wherein the mechanical factors of said fiber glass structure, the mechanical factors of said first jacket layer and the mechanical factors of said second jacket layer are selected in order that the Young's modulus of said first jacket layer is larger than the average tensile stress (&sgr;
r
+&sgr;
&thgr;
+&sgr;
z
)/3 as applied to said first jacket layer
5
while the resin temperature of curable resins largely falls from the temperature when the rigid UV curable resin starts hardening to the temperature when the hardening is finished.
In accordance with a further aspect of the present invention, a method of manufacturing an optical fiber comprises: a fiber glass structure; a first jacket layer made of a soft curable resin and directly covering the external surface of said fiber glass structure; and a second jacket layer made of a rigid curable resin and covering the external surface of said fiber glass structure through said first jacket layer, wherein the mechanical factors of said fiber glass structure, the mechanical factors of said first jacket layer and the mechanical factors of said second jacket layer are selected in order that the Young's modulus of said first jacket layer is larger than the average tensile stress (&sgr;
r
+&sgr;
&thgr;
+&sgr;
z
)/3 as applied to said first jacket layer
5
while the resin temperature of curable resins largely falls from the temperature when the rigid UV curable resin starts hardening to the temperature when the hardening is finished.
In accordance with a further aspect of the present invention, an optical fiber comprises: a fiber glass structure; a first jacket layer made of a soft curable resin and directly covering the external surface of said fiber glass structure; and a second jacket layer made of a rigid curable resin and covering the external surface of said fiber glass structure through said first jacket layer, wherein, in the case where the Young's modulus of said soft curable resin is substantially small as compared to the Young's modulus of said rigid curable resin, the coefficient of thermal expansion a, of said soft curable resin and the coefficient of thermal expansion &agr;
2
of said rigid curable resin satisfy
α
2
>
3
2
(
1
+
v
2
)
{
1
-
(
R
0
R
1
)
2
}
{
α
1
-
1
-
2
v
1
Δ
T
}
where R
0
is the radius of the fiber glass structure
3
, R
1
is the outer radius of the first jacket layer
5
, &ngr;
1
is the Poisson's ratio of the soft curable resin, &ngr;
2
is the Poisson's ratio of the rigid curable resin, and &Dgr;T is the deviation of the resin temperature of said curable resins from the temperature when the rigid UV curable resin starts hardening to the temperature when the hardening is finished.
In accordance with a further aspect of the present invention, an optical fiber cable in which a plurality of optical fibers are bundled, each of said optical fibers comprises: a fiber glass structure; a first jacket layer made of a soft curable resin and directly covering the external surface of said fiber glass structure; and a second jacket layer made of a rigid curable resin and covering the external surface of said fiber glass structure through said first jacket layer, wherein, in the case where the Young's modulus of said soft curable resin is substantially small as compared to the Young's modulus of said rigid curable resin, the coefficient of thermal expansion &agr;
1
of said soft curable resin and the coefficient of thermal expansion &agr;
2
of said rigid curable resin satisfy
α
2
>
3
2
(
1
+
v
2
)
{
1
-
(
R
0
R
1
)
2
}
{
α
1
-
1
-
2
v
1
Δ
T
}
where R
0
is the radius of the fiber glass structure
3
, R
1
is the outer radius of the first jack
Ohashi Keiji
Watanabe Hirohito
Fujikura Ltd.
Hughes James P.
Lee John R.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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