Note: Descriptions are shown in the official language in which they were submitted.
CA 02389675 2002-04-30
Attorney Ducket No. 8433-000003
ARRANGEMENT OF FIBER OPTICAL ELEMENTS
AND A SPLICE HOUSING FOR FIBER OPTICAL ELEMENTS
DESCRIPTION
[0001] The invention provides an optical fiber element and splice
housing arrangement for optical fiber elements of high-voltage cables, in
particular sea cables, especially those including fiber optics carried in an
outer
area.
[0002] It is known in the art to provide coupling collars for plastic-
insulated high and intermediate voltage cables having integrated fiber optics
within the cable covering (German Patent Nos. DE 40 12 183 A1 and DE 39 05
090 A1 ), the construction of which includes a separate splice housing for
enabling splicing and lengthening of the fiber optics, which is built tubular
or
square-formed dependent upon the number of fiber optics integrated in the
cable
covering. The splice housing is positioned parallel to the collar in the area
between this collar and a shrink wrap covering the collar.
[0003] Typical, for such arrangements is that the fiber optical elements
are directly inserted into the end faces of the splice housing. The end faces
lie
orthoganol to the axis of the high voltage cable, so that the fiber optical
elements
are taught in the transition area between the cable and the splice housing.
[0004] With fixed lying high voltage cables, positioning of the adjacent
fiber optical elements outside of the splice housing presents no problems,
because, after having installed the cable, flexing is no longer a concern.
With
other high voltage cables, in particular sea cables, splicing is mainly
performed
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CA 02389675 2002-04-30
Attorney Docket No. 8433-000003
prior to installation. During installation, the high voltage cable is unwound
from at
least one installation roll and thereby flexed. Should a splice with a splice
housing already exist along the high voltage cable, the splice housing must
flex
without problem, it cannot reduce the flexibility of the high voltage cable
and must
further provide full stress protection for the fiber optical elements.
[0005] With flexing of the high voltage cable, the fiber optical elements
having a straight insertion into the end faces of the splice housing, would be
accordingly compressed or stretched as the result of the absence of a length
compensator that could relieve the flexing stresses of the fiber optical
elements.
If one wanted to implement such a length compensator for the fiber optical
elements, it must be assembled into the splice housing, thereby increasing the
construction time and resulting in an unmanageable housing size.
[0006] It is an object of the invention to provide an arrangement of fiber
optical elements and a splice housing for fiber optical elements, which
fulfills the
requirements of optimized protection for the fiber optical elements even under
flexing stress of the high voltage cable, in particular sea cables.
[0007] The solution is depicted in the features of the following claims.
Further arrangements are found in the underlying dependent claims.
[0008] The invention assumes that the fiber optical elements are
preferably, but not always, positioned in the outer area {cable covering,
reinforcement covering, exterior filling) of the high-voltage cable. As fiber
optical
elements are exemplary defined as one or more small stainless steel tubes, in
which one or more fiber optical fibers are lead. The fiber optical elements
are
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Attorney D~.;Ket No. 8433-000003
wound around the surface of the cable with a 180° bend from their
position in the
energy cable. Then, the fiber optical elements are preferably inserted through
a
pressure-sealed seal bushing into the splice housing.
[0009] In accordance with the following described embodiment for a
high voltage cable with an outer diameter of approximately 70mm, the fiber
optical elements are disposed in the reinforcement area. The single small
stainless steel tube with fiber optical fibers is thickened to an equivalent
diameter
of one of the reinforcement covered with a plastic cable covering and
substitutes
for one or more reinforcement wires. For one fiber optical splice the fiber
optical
fibers must have slack of up to approximately one meter. If a splice is
necessary,
the slack can be provided in the reinforcing machine. With a fiber optical
splice
in the immediate vicinity of an energy cable splice the necessary slack can be
similarly provided. With repair, the fiber optical elements must be inserted
into
the energy cable assembly and interconnected with one another across two
splice housings.
[0010] In accordance with the inventive splice housing the construction
time is reduced, whereby the fiber optical elements are led from their
position in
the cable in an area outside of the splice housing, and from there with a
large
radius redirected about approximately 180° and inserted into the splice
housing
from underneath. This arrangement of the fiber optical element inhibits
compressing and stretching of the elements from flexing stress. This type of
fiber
optic arrangement does not elongate the splice housing.
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Attorney Docket No. 8433-000003
[0011] The splice housing is fixed onto the cable and pressed onto the
cable with two clamp-functioning half rings on the ends. To increase the
safety
against tensile stress, the possibility exists to cut two of the reinforcing
wires (not
those that lie immediately adjacent to the fiber optical elements ), bend them
upwards and bolt them to the inner face of the half rings with fasteners. This
supplementary lock presents, in both the axial direction and circumferential
direction, an effective stretch-resistant fastening. Because the total amount
of
reinforcement wires are usually not required to transfer the installation
force of
the energy cable, the separation of two wires is not problematic.
[0012] The small stainless steel tube is inserted from the exterior
through the seal bushings, up to the bottom of the groove in the side spaces
and
there lengthened. The seal bushings preferably lie at a right angle to the
bottom
surface in the splice housing. Within the splice area the fiber optic fibers
run
without protection. The fiber optic fibers are spliced in a traditional manner
and
provided with a splice protector. The splice protector can be held within a
glued
in splice holder, directly glued or lain in the groove bottom.
[0013] The splice chamber in the splice housing is formed from a flat
space in the lengthwise direction of the splice housing and two lengthwise
positioned deep grooves (side spaces). Within the splice chamber, the fiber
optical fibers can be inserted through one side, the slack lain therein and
again
led out through the other side (diagonally opposing). This gives the advantage
of
turning the direction of the fiber optical fibers for splicing so that more
movement
space is provided. Because of this, the size of the splice chamber is
sufficiently
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Attorney D~uket No. 8433-000003
large so that the minimum bending diameter of the fiber optic fibers that are
approximately 60mm thick is not diminished. The depth of the side spaces and
the width of the flat portions of the splice chamber create an optimal use of
the
available area.
[0014] The insertion of the fiber optical elements is formed of a metallic
seal adjacent the small stainless steel tube and of a bushing seal. In the
case of
a special strengthening of the fiber optical elements with a polyethylene
covering,
the seal bushing seals against the polyethylene covering.
[0015] The cover of the splice housing is pressure sealed. Preferably,
welding is anticipated. For welding and because of the desire for corrosion
resistance, high grade material is implemented (in particular stainless
steel).
Alternatively, the cover can be bolted down and sealed with an O-ring.
[0016] An exemplary embodiment of the invention is illustrated in the
Figures. They show in detail:
(0017] Figure 1 a side view of the splice housing and
[0018] Figure 2 a cross-section through the cable and splice housing.
[0019] The splice housing 10 clasps about two quadrants of the
circumference of the energy cable 8 and includes therewith a half-tubular form
in
the lengthwise direction with a thick wall. In the area of the two lower
quadrants
of the energy cable, the fiber optical elements are gathered from the energy
cable for insertion in the splice housing. The cable is reinforced in the
outer area
with reinforcing wires 6 (6' in Figure 2). The splice housing 10 is releasably
fixed
on to the energy cable, whereby energy clasping half rings 20,21 are
CA 02389675 2002-04-30
Attorney Do4ket No. 8433-000003
implemented on both end sides 120 of the splice housing 10. The half rings
20,21 are bolted to the splice housing 10 with bolts 22.
[0020] The splice chamber is formed from a flat area in the lengthwise
direction and two parallel positioned deep grooves or side spaces 12,12'
having
a somewhat equal length. Preferably, the space 13 for the splice chamber is
formed in the cover 101 of the splice housing. The side spaces 12,12' increase
the splice space sideways and thereby enable a bent storage form of the fiber
optical cables. The exterior edges of the splice housing are filleted where
possible, to avoid hindering bending of the fiber optical elements and to
prevent
damage to the exterior components of the high-energy cable. The fillets enable
the exterior application of a protective coating, for example in the form of a
shrink
tube or a shrink wrap and facilitate the installation motion.
[0021] On each of the underlying long sides of the splice housing a
seal bushing 150 is provided for the pressure sealed insertion of the fiber
optical
element 30. The bushing is screwed about and with an O-ring seal pressure-
sealed against the surface of the fiber optical element 30. Alternative to an
O-
ring, a metallic seal is anticipated. With this a lead body is provided (or an
equivalent soft metal alloy) having an exterior cone and an interior bore,
through
which the small stainless steel tube is inserted. The lead body is screwed
into
the interior cone of the seal bushing with a clamping nut. The advantage of a
metallic seal lies in the diffusion reliability over time, a quality which an
O-ring
seal does not necessarily include.
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[0022] The insertion bores 141 in the splice housing run with relatively
flat angles against the axis of the cable or splice housing - preferably in an
angular range from 15° to 40°. In the illustration of Figure 1,
the angle is
approximately 25°. In Figure 2, a fiber optical element splice is shown
with a
reference sign 32 indicating splice protection.
[0023] The small stainless steel tube 30 is inserted from outside
through the seal bushing 150 around up to the base of the side spaces 12,12'
(see reference sign 141 in Figure 2) and there lengthened. From this point the
fiber optical fibers 33 run without protection. The fiber optical fibers 33
are
spliced in a customary manner and covered with a splice protector 32. The
slack
of the fiber optical fibers are lain in either a circular form or the form of
an eight
(8) in the splice space. The splice protector 32 can be clamped in a glued in
splice holder, itself glued, or lain in the base of the side spaces.
[0024] The splice housing 10 is closed with the cover 101. On the
cover 101 and the corresponding edge of the cover opening are positioned
profiles 102,103, on which a weld seam can be lain.
[0025] For underwater applications, the splice housing 10 and its
components are preferably manufactured from stainless steel.
[0026] A reinforcing wire 6 is bent upward on each end side 120 of the
splice housing 10 and clamped with a screw terminal 24 on the half rings
20,21.
From the Figures it is apparent that the reinforcing wire 6' is fixed on the
half
rings 20,21 with fasteners and bolts 24.
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Attorney Docket No. 8433-000003
[0027] The space between the half-rings 20,21 can be sealed with a
cover 210 (as sheet metal in the form of a half cylinder). It is anticipated
that
grooves 27 are formed in the half rings 20,21, where the cover 210 can be
glued
or screwed fixed thereto. The space beneath the cover is otherwise not sealed.
(0028] Preferably the splice chamber 12,13 is filled with a gel
preferably not exceeding the volume of the side spaces. For improved handling,
a filling bore 160 with a stopper is anticipated on the splice housing. The
splice
chamber can be filled with a light gas to over-pressure. Also a seal test
should
be possible. Through application of a silicon-mass, vulcanizable to a gel, a
penetration of the gas into the small stainless steel tube can be avoided. The
closing of the filling bore 160 or a test opening is achieved in a similar
manner as
the insertion (seal bushings 150 and O-rings or with lead stoppers) for the
small
stainless steel tubes.
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