Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1999-11-23
2002-02-12
Ngo, Hung N. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S083000, C385S147000
Reexamination Certificate
active
06345916
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a fiber optic connector having an optical fiber fixed therein for connecting an optical fiber to an optical device, such as an optical waveguide, and its manufacturing method.
(ii) Description of Related Art
A fiber optic connector wherein optical fibers are fixed to a substrate is used as a fiber optic connector attached to an optical device, such as an optical waveguide.
FIG. 20
is an explanatory diagram of the fiber optic connector disclosed in Japanese Patent Laid Open Publication No. 10-160974.
In this fiber optic connector, only a part of the bare portion
5
a
and
5
b
of optical fibers are fixed to a grooved substrate but the other portion of the optical fibers including the coated portion
5
b
and
6
b
of upper and lower fiber ribbons
5
and
6
are not fixed to a grooved substrate
1
.
As a result, the bare portion of optical fibers easily can be damaged when they touch an edge of the substrate or the like.
Therefore, the coated portion of optical fibers as well as the bare portion of optical fibers in which the coatings have been removed are usually fixed to a substrate in a fiber optic connector.
FIG. 16
shows one example of such a fiber optic connector.
As shown in FIG.
16
(A), a part (called “part A”) for fixing the bare portion of optical fibers and a part (called “part B”) for fixing the coated portion of optical fibers are built onto the substrate
1
, fiber arranging grooves
1
c
are formed in the upper surface of part A
1
a,
and part B
1
b
is formed at a different level than part A
1
a.
As shown in FIG.
16
(B), in order to fix optical fibers
3
onto a substrate, with the bare portions
3
a
of the optical fibers
3
arranged in the fiber arranging grooves
1
c
and pressed down from above by a fiber pressing member
2
, an adhesive
4
is injected around the bare portion of the optical fibers between the fiber arranging grooves
1
c
and the fiber pressing member
2
and also around the bare portion
3
a
and the coated portion
3
b
of the optical fibers
3
placed on part B
1
b.
An illustration of the adhesive is omitted from FIG.
16
(B).
Usually, the outside diameter of a bare portion
3
a
of the optical fiber is approximately 125 &mgr;m and the outside diameter of the coated portion
3
b
of the optical fiber is approximately 250 &mgr;m.
Therefore, if a step down is built between part A
1
a
and part B
1
b
of the substrate so that the difference in the level of the centers of bare portion
3
a
in the fiber arranging grooves
1
c
and the level of the upper surface of part B
1
b
of the substrate is approximately 125 &mgr;m, the center of the optical fibers fixed to the substrate will follow an approximately straight line, as shown in FIG.
16
(C).
In order to connect to a waveguide or the like, the end faces of the bare portion of optical fibers are ground, usually, at a slant, for example at an angle of 8° relative to a plane perpendicular to the axis of the optical fibers so as to reduce the occurrence of reflected light.
However, it is difficult to align the position of the fibers as shown in FIG.
16
. If the position of the optical fibers at the rear end of the fiber arranging grooves
1
c
shifts upward or downward, the bare portion of optical fibers
3
a
will contact either the rear edge of the fiber arranging grooves
1
c
or the rear edge of the fiber pressing member
2
resulting in damage to the bare portion of the optical fiber. The bare portion of optical fibers may also be stressed locally by the expansion or contraction of the adhesive due to heat.
The above problems are particularly striking in double-density fiber optic connectors. Here, double-density fiber optic connectors shall mean high-density fiber optic connectors wherein the sequencing density of the optical fibers is set to double the conventional density, for example the connectors described in 1997
Electronic Communication Information Association General Meeting, Preliminary Lectures,
Takagi et.al., C-3-15, “PLC High-Density Double 2×16 Splitter Module Production.”
Two optical fiber ribbons, an upper and lower, are used in these double-density fiber optic connectors. The bare portion of optical fibers in the upper fiber ribbon are inevitably raised to form a gap between the bare portion and the substrate.
This gap is then filled with adhesive to set the upper and lower optical fibers, demanding a relatively large amount of adhesive. Therefore, the influence of any expansion or contraction of the adhesive due to heat is greater than in the case of normal density fiber optic connectors.
FIG. 17
shows one example of a double-density fiber optic connector. A fiber arranging groove of half the pitch of the fiber arranging groove
1
c
shown in
FIG. 16
is formed on the substrate
1
.
The fiber ribbons
5
and
6
are composed of plural optical fibers having its bare portion (i.e. glass portion) with an outside diameter of 125 &mgr;m coated with a protective coating such that their outer diameter becomes 250 &mgr;m. The optical fibers are arranged at intervals of 250 &mgr;m and covered with a common coating to form a fiber ribbon.
As a result, if the common coating and the protective coating are removed at the tips, the bare portion of optical fibers are aligned with 125 &mgr;m gaps between them. By shifting the upper and lower fiber ribbons
5
and
6
apart horizontally by 125 &mgr;m and layering them on top of each other, the upper and lower bare portion of optical fibers
5
a
and
6
a
fit alternately in their respective gaps. Seen in a planar view, the bare potion of optical fibers
5
a
and
6
a
of the upper and lower fiber ribbons are lined up perfectly straight in alternating pairs. But viewed from the side, the bare portion of optical fibers
5
a
and
6
a
are bent with their front ends pressed down by the fiber pressing member
2
and fixed to the substrate
1
by an adhesive. In this way, a double-density fiber optic connector is obtained.
FIG. 18
shows a double-density fiber optic connector wherein two upper and two lower fiber ribbons have been attached. In the figure, the fiber optic connector comprises 16 fibers arranged in four fiber ribbons, two above and two below.
However, a fiber optic connector with 32 optical fibers can also be made using eight fiber ribbons each having 4 optical fibers.
If the fiber optic connector of
FIG. 18
is observed at in a planar view, the bare potion of optical fibers
5
a
and
6
a
of the upper and lower fiber ribbons are lined up perfectly straight in alternating pairs. However, if it is viewed from the side the bare potion of optical fibers
5
a
and
6
a
are bent with their front ends pressed down by the fiber pressing member
2
and fixed to the substrate
1
by an adhesive.
FIG. 19
shows the fixed condition of the bare potion of optical fibers in the double-density fiber optic connectors of
FIGS. 17 and 18
. The tips of the bare portion of optical fibers
5
a
and
6
a
of the upper and lower fiber ribbons
5
and
6
are fixed at the same height, but the positions of the bare portion of optical fibers within the upper and lower fiber ribbons differ. As a result, the bare portion of optical fibers
5
a
of the lower fiber ribbon
5
stretch and extend toward part A
1
a
of the substrate
1
while bending upward and the bare portion of optical fibers
6
a
of the upper fiber ribbon
6
extend toward part A
1
a
of the substrate
1
while bending downward, as shown in FIG.
19
(A). The bare portion of optical fibers
5
a
of the lower fiber ribbon
5
can also be made perfectly straight, but in that case it is necessary to increase the bend in the bare portion of optical fibers
6
a
of the upper fiber ribbon
6
more than that shown in FIG.
19
(A).
In either case, upward and/or downward bends in the fibers result.
If the radius of curvature of these bends is small and the bare portion of optical fibers are fixed in this condition, they may break due to static fatigue.
In order to increase the rad
Ikechi Teruo
Ishida Hidetoshi
Kobayashi Kohei
Sasaki Takashi
Shiozaki Manabu
Ngo Hung N.
Sumitomo Electric Industries Ltd.
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