Electric heating – Heating devices – Plural separate heating devices
Reexamination Certificate
2000-06-27
2002-08-20
Jeffery, John A. (Department: 3742)
Electric heating
Heating devices
Plural separate heating devices
C219S480000, C219S544000, C219S466100, C219S468100, C392S432000, C385S099000, C385S134000
Reexamination Certificate
active
06437299
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for heating a protective member for protecting a fusion splicing part of optical fibers.
2. Description of the Related Art
Two coated optical fibers are permanently spliced to each other in such a manner that a coating layer of an end part of each coated optical fiber is removed to expose a vitreous fiber thereof(hereinafter referred to “optical fiber”), and the thus exposed optical fibers are aligned, joined end to end and fusion spliced together. The exposed portion of the optical fibers including the fusion splicing part is covered with a protective member and protected thereby.
FIGS. 8 and 9
are diagrams showing protective members each used for the optical fiber fusion splicing part.
FIGS. 8A and 9A
are transverse sectional views of the protective members, and
FIGS. 8B and 9B
are longitudinal sectional views of the same.
In
FIGS. 8 and 9
, reference numerals
10
and
10
′ represent protective members;
11
and
11
′, adhesive tubes;
12
and
12
′, reinforcing members; and
13
, a thermal shrinking tube. The protective member
10
of
FIG. 8
is applied mainly to a splicing part of the optical fiber ribbon containing a plurality of optical fibers. The protective member
10
′ of
FIG. 9
is applied mainly to a splicing part of a coated optical fiber containing a single optical fiber.
The protective member
10
of
FIG. 8
consists of the thermal shrinking tube
13
, the adhesive tube
11
and the reinforcing member
12
which is solid semicircular in cross section. The adhesive tube
11
and the reinforcing member
12
are stored in the thermal shrinking tube
13
while the reinforcing member
12
is disposed in parallel to the adhesive tube
11
in a longitudinal direction. The protective member
10
′ of
FIG. 9
consists of the thermal shrinking tube
13
, the adhesive tube
11
′ and the reinforcing member
12
′ which is solid circular in cross section. The adhesive tube
11
′ and the reinforcing member
12
′ are stored in the thermal shrinking tube
13
while the reinforcing member
12
′ is disposed in parallel to the adhesive tube
11
′ in a longitudinal direction. The adhesive tubes
11
and
11
′ are made of adhesive resin, such as ethylene vinyl acrylate. The reinforcing members
12
and
12
′ are made of material having good heat resistance and a high compressive strength, such as glass ceramic or stainless steel. The thermal shrinking tube
13
is made of irradiated polyethylene, for example.
An optical fiber ribbon containing a plurality of optical fibers is made in such a manner that a plurality of optical fibers are aligned and coated by a coating resin to form a tape-shape. As shown in
FIG. 8
, the reinforcing member
12
is shaped to be solid semicircle in cross section, and the adhesive tube
11
is shaped to be hollow elliptical in cross section, in order to dispose the optical fiber ribbon thereto easily. However, the adhesive tube
11
may be hollow circular in transverse cross section, since it is soft and easy to be deformable. In the case of a coated optical fiber containing a single optical fiber, the cross section of the coated optical fiber is circular, and hence, there is no need that the reinforcing member
12
′ should be solid semicircular in cross section. Therefore, as shown in
FIG. 9A
, the reinforcing member
12
′ is solid circular in cross section, which makes it easy to manufacture of the reinforcing member, and the adhesive tube
11
′ is also hollow circular in cross section.
FIG. 10
shows a working procedure to protect an optical fiber fusion splicing part with the thus produced protective member.
FIGS. 10A
,
10
B and
10
C are longitudinal sectional views showing the working procedure. In
FIG. 10
, constituent parts same as those in
FIGS. 8
are referenced correspondingly, and their description will be omitted. In
FIG. 10
, reference numeral
14
represents an optical fiber ribbon;
15
, an optical fiber; and
16
, a fusion splicing part.
As shown in
FIG. 10A
, two optical fiber ribbons are spliced to each other in such a manner that a coating layer of an end part of each optical fiber ribbon is removed to expose optical fibers thereof, and the thus exposed optical fibers are aligned, joined end to end and fusion spliced together. The exposed portion of the optical fibers
15
including the fusion splicing part
16
is passed through the adhesive tube
11
of the protective member
10
. A plurality of optical fibers
15
are aligned in parallel in the direction vertical to the paper of the drawing. Accordingly, the optical fibers
15
are seen as a single optical fiber in FIG.
10
.
Subsequently, the fusion splicing part of the optical fibers, which is covered with the protective member
10
, is disposed on a heater of a heating apparatus and heated thereby. By the heating, the adhesive tube
11
is fused, and also the thermal shrinking tube
13
is thermally shrunk. A compressive force of the thermal shrinking tube
13
generated due to thermal shrunk puts the fusion splicing part of the optical fibers adaptively along the reinforcing member
12
. The inside of the thermal shrinking tube
13
is filled with the fused adhesive resin of the adhesive tube
11
.
FIG. 11
shows an embodiment of a heater of a heating apparatus which is used for heating the protective member.
FIG. 11A
is a plan view showing the heater, and
FIG. 11B
is a longitudinal sectional view taken on line X—X in FIG.
11
A.
FIG. 11C
shows a graph of a temperature distribution of the heater. The heater designated by reference numeral
17
is a ceramic heater in which a heating conductive circuit
17
a
is buried in a narrow ceramic plate
17
b
. The heater
17
has a temperature distribution configured such that temperature at the center of the heater is high and gradually decreases toward both sides ends of the heater as shown in FIG.
11
C. That is, when the heater is operated, the protective member
10
is heated gradually from the center to both side ends.
FIG. 10B
shows the protective member when its center is heated.
FIG. 10C
shows the protective member when the heating reaches both side ends of the protective member. As shown in
FIG. 10B
, with the heating of the heater, at first, a central portion of the adhesive tube
11
is fused, while the central portion of the thermal shrinking tube
13
shrinks. Subsequently, the phenomena of the fusing of the adhesive tube and the shrinking of the thermal shrinking tube gradually progress toward both side ends of the protective member. Finally, the adhesive tube is fused over the entire length of the protective member and the thermal shrinking tube is also shrunk over the entire length as shown FIG.
10
C.
During this process, the phenomenon of fusing of the adhesive tube progresses from the center to both the side ends and therefore air around the central portion of the fusion splicing part of the optical fibers is extruded towards both the side ends of the protective member. If the air is completely extruded from the center to both the side ends, there is no fear that the air around the optical fiber fusion splicing part remains in the form of air bubbles in the adhesive resin.
If the phenomenon of the heating of the protective member does not progress from the center toward both the side ends gradually and the portions near both side ends is heated excessively quickly, the air is not completely extruded to both the side ends and sometimes remains in the form of air bubbles in the adhesive resin. In such a case that air bubbles remain in the vicinity of the optical fiber fusion splicing part, the following problem arises. When the optical fiber fusion splicing part protected by the protective member undergoes a variation of ambient temperature, the air in the bubbles expands and shrinks to generate a bending stress in the optical fiber. This leads to deterioration of the transmission charac
Torii Ken-ichi
Watanabe Tsutomu
Jeffery John A.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
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