Optical fiber

Details Optical fiber Optical fiber

1999-04-29

2001-07-31

Font, Frank G. (Department: 2877)

Optical waveguides

Optical transmission cable

Ribbon cable

C385S110000

Reexamination Certificate

active

06269210

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber having a non-strippable thin coating disposed on a cladding.
2. Description of the Related Art
As shown in
FIG. 5
, an existing optical fiber ribbon is composed of a plurality of optical fibers
4
(normally, four to twelve fibers) and an outer coating
5
. The optical fibers
4
are arranged in a row. The outer coating
5
is made of synthetic resin with a Young's modulus of 50 kgf/mm
2
to 100 kgf/mm
2
at room temperature. The outer coating
5
is disposed around the optical fibers
4
. Each of the optical fibers
4
is composed of a core and cladding
1
, a primary coating
2
, and a secondary coating
3
. The primary coating
2
is disposed around the cladding and made of synthetic resin with a Young's modulus of 0.1 kgf/mm
2
to 0.5 kgf/mm
2
at room temperature. The secondary coating
3
is disposed on the primary coating
2
and made of synthetic resin with a Young's modulus of 40 kgf/mm
2
to 100 kgf/mm
2
at room temperature. The coatings
2
,
3
and
5
suppress a transmission characteristic from fluctuating against a lateral pressure and a temperature variation.
Each coating of the optical fiber ribbon has an optimum thickness so as to stably protect the characteristics of the core and cladding
1
. For example, in the case of an optical fiber ribbon for use with a four single-mode (SM) fibers, the primary coating
2
and the secondary coating
3
are disposed on an SM optical fiber with a diameter of 125 &mgr;m in such a manner that the diameter of the primary coating
2
becomes 180 to 200 &mgr;m and the diameter of the secondary coating
3
becomes 230 to 250 &mgr;m. In addition, the outer coating
5
is disposed in such a manner that the ribbon width and ribbon thickness become 1.10 mm and 0.38 mm, respectively.
As optical communications have advanced in recent years, an optical fiber cable that densely contains optical fibers has been required. Thus, the improvement of the fiber density of an optical fiber ribbon, which is a basic dimension of an optical fiber cable, has been demanded.
Moreover, in recent years, a planar lightwave circuit (PLC device) has been densely structured. From this point of view as well, an optical fiber ribbon with a high fiber density has been demanded. As shown in
FIG. 6
, when a high density PLC fiber array with a distance of 125 &mgr;m between the center of the optical fibers is formed with two SM optical fiber ribbons with eight fibers
6
having a diameter of 250 &mgr;m, the core and cladding
1
with an diameter of 125 &mgr;m should be cross-bent. Thus, in addition to low workability, the bare fibers may contact in the fabrication process. Thereafter, the core and cladding
1
may break because of an aged deterioration due to a bend stress. Consequently, the reliability of the PLC device may deteriorate. Thus, a high density optical fiber ribbon for use with to a high density PLC device has been desired.
However, in the optical fiber ribbon, as described above, it is difficult to decrease the thickness of each coating for improvement of the fiber density since each coating is disposed with an optimum thickness necessary and sufficiently for stable characteristics of optical fibers. Thus, the optical fiber ribbon cannot satisfy such requirements.
SUMMARY OF THE INVENTION
This invention is disclosed in Japanese Patent Application No. 10-120911 filed on Apr. 30, 1998 and Japanese Patent Application No. 10-249846 filed on Sep. 3, 1998, and the entire disclosure thereof is incorporated herein by reference.
An object of the present invention is to provide an optical fiber ribbon with a high density in an optical fiber cable and that allows a PLC device to be structured with a high density.
A first aspect of the present invention is an optical fiber ribbon, comprising a plurality of optical fibers arranged in a row, and an outer coating formed around the 20 optical fibers, each of the optical fibers comprising a core, a cladding, and a non-strippable thin coating made of synthetic resin with a Young's modulus of 50 kg/mm
2
to 250 kg/mm
2
at room temperature and coated around the cladding.
The thickness of the non-strippable thin coating is preferably in the range from 2 &mgr;m to 15 &mgr;m.
The concentricity of the core to the diameter of the non-strippable thin coating is preferably 1 &mgr;m or less.
In a preferred embodiment, the outer coating has a primary coating made of synthetic resin with a Young's modulus of 0.01 kg/mm
2
to 0.5 kg/mm
2
at room temperature, and a secondary coating made of synthetic resin with a Young's modulus of 10 kg/mm
2
to 200 kg/mm
2
at room temperature.
The optical fibers are preferably almost closely arranged in a row. The primary coating is preferably formed in a ribbon shape of which the thickness thereof is twice or less than the diameter of each of the optical fibers and the width thereof is 30 &mgr;m to 100 &mgr;m longer than the total diameter of the optical fibers arranged in a row. The thickness of the secondary coating is preferably in the range from 20 &mgr;m to 100 &mgr;m.
In a preferred embodiment, each of the optical fibers also has a soft coating that is made of synthetic resin with a Young's modulus of 0.01 kg/mm
2
to 0.5 kg/mm
2
at room temperature and disposed on the non-strippable thin coating. The outer coating is preferably made of synthetic resin with a Young's modulus of 10 kg/mm
2
to 200 kg/mm
2
at room temperature.
The optical fibers are preferably almost closely arranged in a row. The diameter of the soft coating is preferably twice or less than the diameter of each of the optical fibers. The outer coating is preferably formed in a ribbon shape of which the thickness thereof is twice or less than the diameter of each of the optical fibers and the width thereof is 20 &mgr;m to 150 &mgr;m longer than the total diameter of the optical fibers arranged in a row.
The outer coating is preferably composed of synthetic resin with a Young's modulus of 10 kg/mm
2
to 200 kg/mm
2
.
The optical fibers are preferably almost closely arranged in a row. The outer coating is preferably formed in a ribbon shape of which the thickness thereof is twice or less than the diameter of each of the optical fibers and the width thereof is 30 &mgr;m to 150 &mgr;m longer than the total diameter of the optical fibers arranged in a row.
According to one aspect of the present invention, the outer diameter of an optical fiber and of an optical fiber ribbon can be much sufficiently reduced than the conventional ones. Thus, since the distance between adjacent optical fibers is shortened, the fiber density can be improved. In addition, the characteristics of the optical fibers can be sufficiently protected by the non-strippable thin coating and the outer coating disposed around the optical fiber. Thus, the optical fiber ribbon accomplishes an optical fiber cable that densely contains optical fibers. In addition, when the optical fiber ribbon is used for a high density PLC device, the reliability thereof can be improved.
A second aspect of the present invention is an optical fiber, comprising a core, a cladding, and a non-strippable thin coating made of synthetic resin with a Young's modulus of 50 kg/mm
2
to 250 kg/mm
2
at room temperature and coated on the cladding, wherein the concentricity of the core to the diameter of the non-strippable thin coating is 1 &mgr;m or less.
The diameter of the non-strippable thin coating is preferably 125 &mgr;m.
The concentricity of the core to the diameter of the cladding of the optical fiber is preferably 1 &mgr;m or less.
In a preferred embodiment, the optical fiber further comprises a primary coating disposed on the non-strippable thin coating and made of synthetic resin with a Young's modulus of 0.01 kg/mm
2
to 0.5 kg/mm
2
at room temperature, and a secondary coating disposed on the primary coating and made of synthetic resin with a Young's modulus of 10 kg/mm
2
to 200 kg/mm
2
.
According to an as

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