Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SUBSURFACE FIBRE OPTIC CABLE
NETWORK INSTALLATION
Field of the Invention
The present invention relates to subsurface installation of fibre optic
cables, for example, in urban settings where cable is laid buried under the
surfaces of streets or sidewalks. As well, the invention relates to fibre
optic
cable installation within masonry construction and other construction, as
well as systems for forming a branching fibre optic cable network.
Background of the Invention
With the rapidly growing need for high-speed data connections to
businesses and residences (driven mainly by the need to access the
Internet) a faster and more economical method is needed in order to
deliver these connections. Optical fibre offers the greatest potential to
deliver high-speed services due to its ability to carry high bandwidth over
long distances. One problem that the telecommunications industry has
been faced with is the high cost of installing optical fibre between the
provider and the end customer. This issue has restricted the expansion of
optical networks to very densely populated regions where the economics
can justify the expensive conventional construction process of burying
cable within a relatively large trench.
It has been suggested that an inexpensive and simple means to lay cable
is within a shallow slit-like trench cut into an upper layer of pavement or
the
like, for the laying of a cable within or immediately under a street or other
surface. Such a system requires a convenient means to form junctions or
branches within the cable system. In conventional cable-laying systems or
methods, the forming of a branching network requires considerable
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additional excavation in order to install conventional junction boxes or the
like.
It is desirable to provide a simple and inexpensive system for installing a
branching-type network of fibre optic cables within a variety of surfaces.
One approach that is known is to install cable within narrow slit-like
trenches or recesses that are cut, for example, into street surfaces. Such
an arrangement should also provide a convenient means for subsequent
location of intersection points, as well as providing for future expansion of
the cable network. For the latter, it is important that this system provide an
easy means to provide cable slack without requiring the labour-intensive
job of splicing of cables to meet future system needs.
Further, it is desirable to provide a junction box or branching node that
readily fits within a narrow slit like trench or groove without requiring
substantial additional excavation, and which further is easy to install and
subsequently locate.
Description of the Prior Art
Several patents have been issued for technology relating to electrical and
optical fibre cable installations.
One example is U.S. Patent No. 5,879,109 issued to Finzel, et al. which
provides a complex process for installing optical or electrical cable into
solid surfaces such as asphalt. The method uses a slow moving apparatus
to heat the ground surface until it has softened. A channel-forming unit is
subsequently used to introduce a channel into the heated ground by
displacing the ground material alongside the channel border. A laying unit
is then used to introduce the optical or electrical cable into the channel,
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followed by a filling unit which is used to reintroduce the displaced ground
material back into the channel and then rolled to compact the ground
material which has been reintroduced into the channel. However, the
complexity of this method if used for small segment connections between
end customers and providers of optical fibre cable within confined urban
locations and in a variety of infrastructure materials would make it
prohibitively expensive. Also, this method does not work in concrete
material as found in sidewalks, curbs and grout lines, which are often
preferred routes in most last mile deployments.
In another example, U.S. Patent No. 6,065,902 issued to Mayr, et al.
provides a method and apparatus for on-site production and installation of
optical fibre cable at the location for placing. This method seeks to reduce
transportation costs and quantity of material required for large-scale optical
fibre cable installations. However, for small-scale installations this method
is impractical and notably more expensive.
Canadian published application no. 2,237,324 (Zeidler et al) discloses a
method for laying a thin fibre optic cable of between 2 mm and 10 mm,
within a narrow channel having a width slightly wider than the cable. The
cable is introduced into the channel by means of a cable feed device, and
is filled with infill material by a filling device which moves along in a
coordinated fashion with the laying device. The laying channel extends
into the top several layers of a paved surface and is between 4 cm and 15
cm in depth, with 7 cm being identified as ideal.
The prior art systems and methods tend to be complex, expensive and do
not suitably provide for several needs. There is a need for a convenient
arrangement for forming cable junctions. There is a need to easily provide
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slack in the installed cable to accommodate junctions, system expansions
and repairs. There is a further need to easily accommodate a variety of
surfaces including pavement, sidewalks, vertical walls, unpaved surfaces
such as sod, etc.
Summary of the Invention
The objects of this invention are to provide improved methods and systems
for installing cable within a narrow, shallow trench; to provide a convenient
cable junction system; and to provide means to accommodate future
system expansion. In accordance with the above objects, the present
invention comprises in one broad aspect a method for laying or installing of
a cable such as a fibre optic cable, or a branching network of fibre optic
cables within a surface or substrate such as a paved roadway, a masonry
wall or other hard or soft surface. The term "substrate" herein means any
surface, whether a roadway, walkway, wall or the like.
It is contemplated that system "nodes" are provided at intervals within the
cable network system. A node may comprise a cable junction or a region
of looped cable that may be used to provide cable slack for future node or
junction installation or other system expansion. In this aspect, the method
consists of the steps of:
= cutting a narrow channel or groove within a surface such as
pavement or other ground surface or a portion of a. building or
residential unit;
= installing a fibre optic cable within the narrow channel;
= providing at periodic convenient locations one or more system nodes
by installing within the channel at such locations a loop of cable, and
optionally a junction box, and connecting to said junction box on
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opposing sides of an incoming cable and two or more outgoing
cables; and
= backfilling and sealing said channel or groove.
The channel typically has a width between nodes of between about 1 mm
and 50 mm with a preferred range of between 2 mm and 12 mm. A still
more preferred width is between 4.5 mm and 6 mm. The depth of the
channel is between about 8 mm and 250 mm, although there is in principle
no limit to the depth of the channel and depths up to 1 m are acceptable.
The preferred depth range is between 12 mm and 172 mm. A most
preferred depth is between 40 mm and 70 mm. Depending on the width of
the channel on each side of a node, the channel may be widened at the
region of each node, by up to a further 20 mm but preferably by no more
than a further 15 mm.
The deeper end of the depth range of the channel (e.g. 50 mm- 1 m) is
suitable for crossing streets that may get resurfaced in order to survive a
pavement grind and overlay. As well, a deeper cut within this same range
is desirable if the surface is breaking away or is in generally bad shape. If
the surface is sound then the cut may be in the range of 8 - 50 mm in depth
and preferably about 40 mm deep. In another aspect, the blade that is
used on the slab saw makes a cut that is about 4.5 mm wide.
The junction box consists of a narrow, generally flat housing having a width
suitable for fitting within the narrow channel.
In another aspect, a metal member capable of detection by a metal
locating device is incorporated within the junction box or buried within in a
node either in the absence of a junction box or in position with the junction
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box, in order to provide a convenient means for subsequent location of the
junction box or node by means of a metal detection device. The metal
member may be either non-ferrous or ferrous, or alternatively, a ferrous
member may be buried with a non-junction box node and a non-ferrous
mmeber with a junction box node, or vice-versa, for differential (i.e.
discriminating) detection by different types of metal detectors after burial.
In a further aspect, the channel as described above is formed within the
interstices between pavers on a walkway or roadway, or within a masonry
wall. In the case of a wall, the channel has a generally horizontal
orientation and is formed between adjacent brick layers. In this aspect, the
channel has the width described above but the shallower end of the depth
range is sufficient, i.e., about 12 mm deep. The channel is then covered
with mortar grouting to provide a matching appearance with the remainder
of the brick or masonry wall. In a similar fashion, the channel may be
formed in the interstices within a brick or stone walkway or roadway.
In a further aspect, the location of the channels within a masonry wall may
be indicated by visual indicators and/or metal implants for location by a
metal detection device.
In a further aspect, the channel is wholly within a surface region or layer of
an asphalt or concrete roadway or sidewalk. Ina further aspect, the trench
may be cut at or immediately adjacent to the junction of a roadway and a
curb, or within an expansion joint between a curb and an adjacent
sidewalk.
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In a further aspect, a plurality of cables may be laid in overlying
relationship
within a trench. The plurality may be between 2 and 20 cables, with a
preferred array being 2 to 5 cables.
In a further aspect, the trench may be filled with liquid resin or other
anchoring cement to form a smoothly finished patch. An example is a
two-part polyurethane grout that hardens, but remains flexible. When
hardened, this material is very difficult to pick away and seals the cut. In a
still further aspect, a wire may be positioned to immediately overly the
installed cables to provide a convenient means for removing the overlying
patch material for future maintenance. In a still further aspect, a looped
portion of fibre optic cable may be formed within a deepened portion of the
channel at a location removed from the junction node to provide cable
slack for future expansion of the cable network.
In a still further aspect, one or more of the system nodes include between 1
and 20 loops of cable, for providing slack when required for future system
needs, with a preferred number of cable loops being between 2 and 5.
In a still further aspect, the invention relates to a junction box for
installation
within a narrow slit-like channel or trench, as part of a fibre optic
branching
network or system. In this aspect, the box consists of a housing or case
having flat opposing sides with an overall width selected to fit snugly within
the trench. Preferably, this width is between 5 mm and 20 mm, and
preferably between 8 mm and 12 mm. A most preferred width is about 10
mm to fit within the narrow slit-like trench or channel. The inside cavity is
about 6 mm in width to accommodate passive optical components and/or
splices. The two sides are joined together by releasable fastening means.
Conveniently, the box is generally rectangular in all elevations. An opening
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at one of the ends of the box permits entry of input cable line. A plurality
of
openings on a second, opposed end of the box permits the outlet of output
cable lines. The inlet and outlet entries are provided on the narrow ends of
the box in order to maintain a flat, narrow arrangement when the cables are
joined with the box. Sufficient interior space within the junction boxes is
provided for joining together the input and output cable ends. As well,
passive optical networking components and optical splices may be placed
in the box.
In a still further aspect of the above method, one or more loops of cable
slack are formed to surround the junction box prior to burial of the node.
A further aspect of the invention relates to a cable-winding device for
forming one or more cable loops for installation in a node. The winding
device comprises a base having cable-receiving means at either end for
winding a length of cable, which may be subsequently removed from the
device for burial. Conveniently, rotatable arms at the receiving means
releasably retain the cable. A junction box retaining means such as an
array of pegs extending from the base may be provided to releasably hold
a junction box against the base in position from wrapping cable loops
around the box.
A generally rigid frame such as a rigid wire loop may be provided to
support the cable loops. By "rigid" is meant having sufficient rigidity to
protect a cable loop from damage. A high degree of rigidity is not
necessarily required. The frame has generally the same configuration as
the cable loops, and is joined to the base either before or after the loops
are wound about the base. The combined looped region of cable and wire
frame are then released from the winder for burial. The attached wire
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frame adds rigidity to the cable loops to prevent inadvertent crushing before
or after
burial.
A still further aspect of the invention relates to a rigid conduit for burial
of cable
within a narrow trench or channel set within a soft ground surface such as
sod. In
this aspect, the conduit comprises an elongate, hollow conduit such as a
length of
PVC pipe having a channel extending into the interior thereof and extending
the full
length of the conduit. The conduit may have a generally circular oval or
rectangular
cross-section. The invention further relates to a method for installing cable
within a
soft ground surface such as sod by cutting a narrow trench as described above,
and
installing into the channel one or more fibre optic cables together with an
elongate
conduit as described above with the channel facing downwardly followed by
burial of
the conduit to restore the surface.
A further aspect consists of a fibre optic cable comprising a substantially
waterproof
outer casing, a fibre optic core, and an absorbent material within the
interior of the
cable, such as a string having a super-absorbent polymer embedded in its
fibres.
According to a further aspect, the invention relates to an assembly for
installation in
a subsurface fibre optic network, comprising a plurality of fibre optic cables
and a
fibre optic cable protector for retaining said cables, said cable protector
comprising
an elongate member having sidewalls defining an interior space therebetween,
with
a closed upper end and a selectively openable lower end, said openable lower
end
including mating closure members on each of said sidewalls to selectively open
said
protector to receive said cables in said interior space, wherein said cables
and said
interior space are configured whereby the cables are confined between said
sidewalls in a vertically stacked array one cable in width.
The mating closure members may comprise a projecting ridge extending from a
first
of said side walls and a groove recessed in an opposing one of said side
walls.
Preferably, the sidewalls are substantially flat and are located parallel to
each other.
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According to another aspect, the invention relates to a method for installing
a fibre
optic cable within a substrate, comprising the steps of providing a cable
protector
comprising an elongate member having sidewalls defining an interior space
therebetween, with a closed upper end and a selectively openable lower end,
said
openable lower end including mating closure members on each of said sidewalls
to
selectively open said protector to receive said cables in said interior space,
forming
a channel within said substrate, opening the lower end to expose the interior
space,
positioning a plurality of fibre optic cables within said interior space in a
stacked
array one cable in width, closing said protector whereby the cables are
confined by
the side walls in a stacked array between said side walls, and burying said
protector
within said channel.
The terms "base", "cap" and like references are not intended to refer to any
particular spatial position of any component but are used herein to refer to
various
components purely for ease of description.
The term "approximately" or like terms herein mean plus or minus 10 per cent.
Brief Description of the Drawings
Figure 1 is a sectional view of a typical fibre optic cable for use in
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accordance with the present invention;
Figure 2(a) is a side elevational view showing a subsurface installation
according to the present invention, including a junction box and cable
winding device;
Figure 2(b) is a plan view of an installed subsurface system;
Figure 3 is a similar view as in figure 2(a), showing a looped cable within a
subsurface installation;
Figure 4(a) is a side elevational view, showing cable loops being prepared
for burial using a cable winding device;
Figure 4(b) is a view similar to Fig. 4(a) with the cables ready for burial:
Figure 5A is a perspective view of a cable winding device with its wire
frame separated;
Figure 5B shows the cable winder with the wire frame in position ready to
receive loops of cable;
Figure 6 is a side view of a masonry brick wall with a cable installed within
a horizontal channel;
Figure 7 is a close-up view of Figure 6 showing a cable installed within a
narrow channel between brick layers;
Figure 7(a) is a plan view, from above showing an installation within a
roadway formed from pavers;
Figure 8 is a sectional view, showing a trench cut within an asphalt or
concrete roadway or sidewalk, with a plurality of cables buried within the
channel;
Figure 9 is a similar view, showing a channel recessed into an expansion
joint between a curb and sidewalk;
Figure 10 is a similar view, showing a close-up view of multiple cables
installed within a trench cut into asphalt or concrete;
Figure 11 is a cross-sectional view showing an alternative installation within
a concrete or asphalt roadway or surface;
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Figure 12 is a more detailed view of the installation shown in Figure 11;
Figure 13 is a perspective exploded view of a junction box according to the
present invention;
Figure 14 is a front elevational view of a further embodiment of the
invention showing an exposed cable installation passing under a conduit;
Figure 15 is a side elevation of the version of Figure 14;
Figure 16 is a sectional view of a further embodiment illustrating a rigid
conduit for retaining and protecting cables; and
Figures 17(a) and 17(b) are sectional views of another version of a conduit
for retaining cables.
Detailed Description of the Preferred Embodiments
Turning to Figure 1, the present invention is intended to be used in
association with narrow gauge fibre optic cables 10, composed of a
polycarbonate and polyester alloy outer casing 12 such as GE Plastics
EnoyTM material and an inner core 16. The core is composed of multiple
optical fibres 17 and a moisture-blocking element 15. The core is
preferably wrapped with a moisture barrier 14. The moisture-blocking
element 15 comprises a string with super absorbent polymer (SAP)
embedded into its fibres extending the length of the cable. The outside
diameter of the cable casing is about 3.8 mm (about 0.15 inches) with a
wall thickness of about 0.9 mm. The fibre used is a non-ribbonized
coloured loose fibre with a diameter of 0.25 mm. These dimensions are by
way of example only and may be varied to suit the application as is known
in this art.
The relatively narrow cable contemplated for use in this invention allows for
easy placement into saw cuts made by common diamond blades. For
cable installation within sidewalk joints and masonry surface walls, the cut
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should preferably be less than 0.3 inches and more preferably, less than
about 0.1875 inches in width so that existing lines in sidewalks (joints and
breakpoints) and grout lines between bricks can be followed without
defacing the appearance and integrity of the infrastructure. The channel
width is between 1 and 25 mm, with a preferred range between 2 and 12
mm and a still more preferred range between 4.5 and 6 mm. A small
diameter cable allows installation under existing surface mounted conduits
by elevating the conduit off of its underlying surface with a spacer block
between the conduit and the surface. This spacer block will shift the
conduit slightly (without disruption) following which the fibre cable can be
pushed under the conduit and permanently mounted, as will be described
in more detail below. The channel depth is described below.
It is important that the cable remain reasonably straight when it is removed
from the spool for installation into a crack or cut into a surface, so that it
will
lie flat in the bottom of the cable channel. If the cable has fixed bends from
handling or from memory of being on the spool, it will tend to rise out of the
channel in certain spots, making installation a challenge. To minimize fixed
bends or memory of being spooled, the material used in the casing of the
cable may be polycarbonate and the cable spool diameter should be
sufficiently large to prevent memory (for example a 30 inch diameter core
on the spools). A polycarbonate material does not distort easily; it springs
back into its original shape after being handled (unless it is kinked with
significant force). The polycarbonate material also exhibits a full range of
good physical, chemical, and economical properties making it suitable for
the present invention.
In general, a cable installation system comprises a length of cable installed
within a relatively shallow and narrow channel (the nature of this channel
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will be described in detail below), interspersed with one or more "nodes". A
node comprises a region of channel containing either loops of cable to
provide cable slack, or a cable junction, or both loops and a junction.
Turning to Figures 2(a) and 2(b), a typical node installation 20 is shown. A
narrow slit-like trench or channel 30 is excavated into a paved roadway 22.
The channel 30 may be cut into any type of paved surface such as
concrete or asphalt, or into the interstices between courses of paving
blocks. The dimensions and mode of excavation will be described in
greater detail below. At the node 20, the trench depth and width is
increased in order to accommodate a junction box 32 and accompanying
cable loop 34. Within the trench leading up to and leading away from the
node, the cable is installed in a conventional manner within the trench,
such that it lies on the floor of the trench. At the node 20, the cable is
looped into one or more loops 34 to provide slack for cable manipulation.
The incoming cable includes a cable end 36, which enters a first side of the
junction box 32. Within the junction box, the incoming cable end 36 is
joined with a plurality of outgoing cables 38. For example, an incoming
cable having twelve optic fibres may be mated with two outgoing cables
having two and ten fibres respectively. Other examples are contemplated,
including one or more incoming cables with 2 to 50 fibres, each mated with
single or multiple outgoing cables. A portion of the outer casing of the
cable is removed to expose the optical fibres in the region of cable that will
be fitted into the junction box. A selection of the exposed fibres 37 may be
severed and respliced to optical fibres from a cable branch. Alternatively a
passive optical component (not shown) can be spliced in to form a branch
with another cable. The outgoing cables may all be laid within a common
outgoing trench. Alternatively, a plurality of outgoing trenches may be
provided in different directions heading away from the node where it is
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desired to form a network branch (Figure 2(b)). If the outgoing plurality of
cables are laid within a common outgoing trench, a branch may be
provided at another location.
A metal member 35 may be buried within the node 20 for subsequent
detection by a metal detector in order to find the location of a node after
burial. The member 35 may be buried within either a junction box-
containing node or a non-junction box node, or both. It is also possible to
provide a means to discriminate between junction box and non junction box
nodes after burial by providing eg. ferrous and non-ferrous members 35
within the different node types for locating by different types of metal
detectors.
Figure 2(a) illustrates a looping of separated optic fibres formed within the
interior of the junction box 32. This provides additional slack for future
needs. For this purpose, individual cables are stripped of their casing to
release the individual fibres 17 each coated, a length of which are then
pulled into the box. The surplus fibres are looped within the interior of the
box 32. One or more loops of the cable 10 may be formed within the
junction box 32.
The cable 10 is preferably installed as one long continuous cable.
Installation of a junction box 32 requires that only the outer case 12 of the
cable is cut away and the optical fibres 17 inside remain uncut and
continuous. About 40 to 100 cm of the casing is stripped at the site of the
junction box thus exposing the optical fibres that then are looped inside the
junction box. The ends of the casing are clamped into the junction box so
that the loops of exposed fibre can be spliced and worked without being
strained by the springy cable casing. A passive optical component (not
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shown) may be spliced into a passing fibre or the fibre from the primary
cable may be severed and spliced onto a fibre from a cable that goes in a
different direction.
Figure 3 illustrates a non-junction node 40 of the network, which provides a
looped portion 34 of cable to provide cable slack to accommodate future
system expansion. At this node, the trench 42 is deepened, and one or
more cabled loops are buried within the trench at this location. Figure 4(a)
illustrates the cable loops prior to burial, and Figure 3 illustrates such
cables subsequent to burial. At these nodes, a junction box 32 may be
installed in the future or cable may be drawn for future repair or expansion
projects. For this purpose, cable slack may be utilized from the node to
permit such future installation. The loops 34 may be of any convenient
size. As a non-limiting example, the loops may each comprise between 0.3
and 3.0 metres of cable formed into an oval or possibly a circular loop.
With the spacing described below, the excess fibre optic cable comprises
from 0.3% to 10% of the total fibre optic cable in the network.
Conveniently, nodes containing either junctions or simply looped cable may
be provided about every 5 to 100 metres of channel. It is understood that
node spacing cannot be maintained at an exact distance due to variations
in the substrate into which the network is being installed. To facilitate
future growth and periodic maintenance, the nodes will be spaced apart an
average of 10 - 40 metres, with a preferred spacing being about every 25
metres on average. While not necessary, preferably there is at least one
non-junction node 40 for each junction box 32 in a network. Further, a loop
node may be provided on either side of a roadway for roadway crossings of
the installed cable.
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Figures 2(a) and 2(b) show a trench 30 cut into a surface at a branching
node position. It will be seen that the trench has a relatively narrow width
at the locations 44 adjacent to the node, in the order of about 4 mm. At the
node, the width 46 is increased by up to a further 20 mm, with a preferred
increase being about 15 mm, making the trench width at this region about
19 to 21 mm. Conveniently, the slit-like trench may be cut into a surface by
means of a saw. At the nodes, the depth of the trench is also increased.
At positions between the nodes, the trench depth is in the order of 40 mm,
while at the nodes the trench depth is in the order of 80 to 200 mm, with a
preferred depth of about 150 mm in order to accommodate the cable loops
and junction box. However, even at its deepest the trench is wholly or
substantially within the asphalt or concrete layer of an asphalt or concrete
roadway or sidewalk. If the trench is within a masonry or sidewalk joint, it
is preferably fairly shallow for convenient installation and subsequent
uncovering.
Concerning the trench depth, the depth is selected to be sufficiently close
to the surface for ease of installation. However, the depth cannot be so
close to the surface as to present a risk of disruption or cutting of the
cable
as a result of normal wear, tear and cracking of the surface, or shallow
cutting of the surface as a result of routine maintenance. Thus, the inter-
node trench depth is between 8 mm and 250 mm, with preferred depths
between 12 and 172 mm and between 30 and 80 mm. A still more
preferred depth for most applications is between 40 and 70 mm with a
most preferred depth being in the order of about 40 mm.
Forming one or more cable loops for burial at a node may be carried out by
means of a cable winding device 200, as shown in Figures 2(a), 4(a), 4(b),
5(a) and 5(b). The winding device comprises an elongate base 202, which
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conveniently has a general oval shape with rounded ends. A pair of pegs
204 is mounted along each side of the base, each peg being capped by a
pivoting arm 206 that rotates freely between a first outboard position
extending past the perimeter of the base, and a second inwardly directed
position. Mounted to either end of the base, and stepped back from the
ends thereof, is a pair of winding blocks 207 having a rounded and grooved
outwardly facing edge 208. The blocks 207 comprise cable-receiving
means for winding a cable about the two blocks. The receiving means
could comprise a suitable outer surface for receiving cable. Each block
207 supports a pair of pivoting arms 210 on its upper surface. An oval wire
frame 212 is provided, the configuration of which matches the shape of the
base 202 although dimensionally smaller to be set inwardly from the
perimeter of the base. As seen in Figure 5(b) the frame 212 is engaged
against the base prior to winding cable about the device, such that the
frame extends around the winding blocks, but inwardly from the pegs 204.
The device may then receive cable for winding about the winding blocks
and against the wire frame. After a selected number of loops of cable have
been wound around the device, the end arms 210 are rotated outwardly to
retain the cable loops and an array of ties 214 may be wound around the
looped cable and frame to bind these components together prior to burial,
as in Figure 4(b). The cable, with frame 212 attached, is removed from the
device 200 for burial in a node. Figure 4(a) illustrates schematically a
winding device, including winding frame, with wound cables ready for
burial.
A junction box may also be retained by the winding device, as seen in
Figure 2(a). For this purpose, the junction box is position against the base
200, and is held in position by arms 206 being inwardly turned as in Figure
5(b). While the junction box is thus retained, one may perform an initial
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winding of cable about the winding device, as well as formation of a
junction within the junction box which has its lid removed for this purpose.
The wound cable loops, together with the sealed junction box with spliced
cable therein, are then installed within a trench, as in Figure 2(a).
Preferably, the wire frame 212 remains attached to the bundle of cable
loops and is buried along with the looped cable within the node. The frame
provides a degree of structural support to the loops to prevent pinching or
breakage after burial. Alternatively, the frame may be removed prior to
burial of the cable loops, particularly if the cables are believed to have
sufficient strength to withstand burial without pinching or breakage.
Conveniently, the trench may be formed in two steps. In a first step, a
narrow saw cut is made within the solid substrate along the full length of
the proposed cable line to form the main trench having a width and depth
as described above. In a second step, at each node a second saw cut is
made with a second, wider blade to cut a slightly wider and somewhat
deeper trench 46 at the node position, to form a node-region having the
shape shown in Figures 3. The trench 46 may be formed with one blade
on a slab saw such as an 18-inch diamond blade with a width of about 4
mm. The blade is dropped down 150 mm for the first pass, followed by a
parallel cut in a slightly offset angle. The material between the cuts breaks
away to form the required junction box cut.
As seen in Figures 6 and 7, a channel 50 may be cut or formed horizontally
within a wall 52. Figures 6 and 7 illustrate a masonry wall construction
although it will be readily seen that other types of wall or wall surfaces
also
easily accommodate a similar cut. In Figures 6 and 7, a channel is shown
having the inter-brick mortar 54 between courses of brick or other masonry
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blocks. Following installation of the fibre optic cables and nodes, the
channel may be covered with additional mortar or anchoring cement. This
may be a semi rigid grout material like polyurethane 56, to cover the
channel. In one version, visual indicators 58 are provided to indicate the
location of the channel for future work and to provide a warning to building
owners as to the location of the cable. Such visual indicators may take any
convenient form including a decorative arrangement.
Figure 7(a) shows an installation option somewhat similar to that in Figures
6 and 7, however, the channel 30 is cut vertically within a roadway into the
interstices between paving blocks 59. The steps are otherwise the same
as described in connection with Figures 6 and 7.
Figures 8 and 9 illustrate additional installation options. In Figure 8, a
slit-
like channel 30 is cut vertically into an asphalt or concrete surface 62 such
as a road or a sidewalk. A plurality of cables 10 are installed within the
channel in overlying relationship. By way of a non-limited example, a
convenient array is up to four cables in a stacked overlying relationship
within the channel. The channel is then patched with liquid rubber semi-
rigid grout material such as polyurethane or anchoring cement 64 to
provide a generally flush appearance. Figure 9 shows a similar
arrangement, in which the channel 30 is cut into an expansion joint
between a sidewalk 66 and an adjoining curb 68. Figure 9 also shows a
similar channel 30 within a paved roadway 22 at a location close to the
curb. Another convenient installation option is a channel cut at the line of
the intersection between a roadway and a curb.
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Figure 10 shows a close-up view of an installation of the type shown in
Figures 8 and 9, with a plurality of cables 10 installed within a trench 30 in
stacked overlying relationship.
A locator wire 67 is positioned to overlie the cables 10. The wire 67 is
locatable by a metal detector and permits early localization of the buried
cables. Also, overlying the cables 10 is a rigid backing rod 69, for
preventing the grout materials from sticking to the cables.
The trench is then patched with a convenient patch material 64 to provide a
smooth appearance. Figures 11 and 12 show a similar arrangement with
one or more cables 10 are installed within a narrow trench or channel 30
recessed into a sidewalk joint 66. The channel may be either vertical or
horizontal. The preferred patching material is a silica-fumed grout.
Figures 11 and 12 illustrate a vertical channel or trench 30 having vertical
sidewalls 68. The cables are overlaid with a sturdy wire 70, the purpose of
which is to aid in future removal of the patch material 64. When it is
desired to remove the patch material at a future date for maintenance or
system expansion, all that is required is to excavate a portion of the
channel to reach the wire. The wire 70 may be then pulled upwardly to
remove the patch material from as much of the channel as is desired. The
wire is formed from a corrosion-resistant and sturdy material, such as
braided cable or any other convenient and suitable wire or cable
arrangement. It is also contemplated that the wire 70 may be detectable by
a metal detector thus serving the same purpose as the locator wire 67.
The purpose of providing a plurality of cables in stacked array within the
same trench is to facilitate splits and routes and to increase the fibre count
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delivered to an area. This feature makes it possible to cover a broader
area and lessens the number of road or sidewalk cuts required.
Turning to Figure 13, a junction box 32 according to the present invention
is illustrated. The box is generally rectangular in plan and elevational
views, and is generally flat and plate-like in appearance. The box
comprises a flat base 80, with a flat lid 82 removably joined to the base by
screws or other like fastening means. In use, the box and lid form
sidewalls when the box is in a vertical orientation. Shallow sidewalls 83
and end walls 86 extend from the base 80. The interior of the box
receives cables and other components, as will be described below.
Opposed end walls 86 of the box are provided with a series of cable entry
and exit orifices 88a and 88b, respectively. A plug 90 is provided at each
opening 88 to prevent or minimize moisture entry. Cable lock 91 prevents
slippage of the cables through the orifices 88a and 88b. The interior of the
box provides sufficient space for a junction to be formed between one or
more inlet cables, and a plurality of outlet cables. The junctions are formed
by conventional means and are not shown. An inwardly stepped shoulder
92 on the sidewalls 83 and endwalls 86 support a cable retainer 87,
consisting of a flat rectangular plate with a hollow middle region. The
retainer 87 is held in place by projections 95 that fit within holes 96 within
the walls 83, 86. The cable retainer 87 projects inwardly over the sidewalls
and end walls 83 and 86, i.e. the sidewalls are undercut from the inside
edges of the retainer. An additional tongue 89 projects inwardly from each
end of the retainer 87. A cable loop positioned within the junction box 32 is
prevented from springing outwardly from the box before the lid 82 is
fastened, by the retainer 87. In particular, the retainer 87 prevents a
portion of the cable loop from being caught under the lid 82 as the lid is
fastened to the box, thereby minimizing the risk of pinching of the cable as
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the lid is fastened. The tongues 89 are provided to catch any portion of the
cable loop that is not otherwise caught by the retainer 87.
The retainer 87 is composed of a semi-rigid rubber material and also
functions as a sealing gasket. Ridges 92 on the walls 83,86 of the box
mate with the flat underside of the retainer 87 and help to create a seal.
Likewise, ridges 92 on the topside of the retainer 87 mate with the flat lid
82 to help create a seal.
The interior of the box 32 also provides sufficient space to house optical
networking components such as splitters. A cable splice holder 99 is
fastened to the base 80, and comprises of an array of semi-ridged, semi-
tubular members for releasably retaining an array of spliced cables.
Typically, a cable splice includes a thickened portion formed by a heat
shrink-wrap extending around the spliced portion. These wrapped portions
of individual fibres are individually held within the splice holder 99.
Alternatively, the splice holder may hold optical splitter components.
The box preferably has a width of no more than about 12 mm, in order to fit
within the node region 20 of the trench or channel described above.
However, the box may have any width within the range of widths
acceptable for the trench width at the nodes. The height and length of the
junction box are within a range for fitting within the trench nodes, as
described above. In one version, the box is in height and length about 95
by 190 mm. In another version, the height and length are 65 mm long by
250 mm respectively.
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Other convenient dimensions for the box range from the above dimensions
to about 290 mm length x 110 mm height x 12 mm width. It will be noted
that the above dimension examples are merely preferred examples and are
not intended to limit the dimensions of the box, which may have
inconvenient dimension of a size which is suitable for installation within a
node, while having sufficient interior space to conveniently permit the
formation of a cable splice. The junction box may comprise an ABS or
ABS polycarbonate alloy base, conveniently with a stainless steel lid. The
gaskets 92 and plugs 90 associated with the box 32 comprise rubber, such
as SantopreneT"" or equivalent.
In a further aspect, as seen in Figures 14 and 15, a cable 10 is
installed underneath an existing surface mounted (i.e., above ground)
conduit 100. This embodiment relies on a conventional conduit of the type
that is supported on a surface 22, for example a cable-containing conduit
supported by a paved surface such as may be found in industrial settings.
Similarly, a conduit may be surface-mounted against a wall. A small space
is created beneath the conduit by separating the conduit from the surface.
This is accomplished by inserting under the conduit a series of spacer
blocks 102. It is contemplated that these will be about 0.1875 inches in
thickness, although this thickness will vary depending on the diameter of
cable and other factors. Suitable thickness of the blocks 102 may range
from 0.1 inches to 0.3 inches. Within the space thus created, one or more
cables 10 are inserted and then installed with cement or the like. Junction
boxes 32 as described above may be similarly mounted, as well as cable
loops 34 being formed at nodes.
It is contemplated that the method of the present invention is suited for
retrofitting of existing infrastructure, such as existing streets, pathways
and
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buildings. However, the method also benefits applications in new construction
of
infrastructure such that the required channel or trench is set into the new
construction at the time of construction or shortly thereafter. This applies
to new
roadways or pathways as well as new buildings, masonry walls and the like.
It will be further noted that the method of the present invention involves a
single step
procedure for cutting a trenchway and laying a cable therein. The equipment
required for cutting the necessary trench is typically a conventional rotary
saw.
Specialized equipment is not general necessary for cutting such a trench.
A still further aspect of the invention is illustrated at Figure 16 and 17. In
this version,
a single cable or a bundle of cables is buried within a soft substrate, such
as sod,
earth, gravel, etc. A channel is formed into the substrate, having a depth
within the
ranges specified above. The width, however, may be wider. A cable protector is
provided, comprising a rigid or semi-rigid elongate member 1200, having an
opening
1202 to the exterior of the member. The opening 1202 extends the full length
of the
elongate member, and opens into an interior space 1204. In one version (Figure
16)
the elongate member 1200 comprises a length of tubular pipe, such as PVC pipe,
having a groove or channel 1202 extending the full length thereof. In another
version
(Figures 17(a) and 17(b)) the member comprises an extruded component 201, such
as a plastic extrusion, having parallel sidewalls 1208, and an open channel
1202.
The protector of Figure 17 has a slimmer profile than the first version (Fig.
16) and is
thus capable of fitting within a somewhat narrower trench than the version of
Figure
16. The cable protector of Figures 17(a) and (b) is generally boat shaped in
section,
with the upper and lower ends thereof tapering to a sharp ridge. The tapered
upper
end serves to deflect a shovel or the like which may accidentally disturb the
protector. As well, the upper end region of the protector comprises solid
material,
thus providing additional resistance against breakage. The protector may be
formed
from rigid or semi-rigid PVC or other suitable material. The sidewalls 1208
are
openable to receive cables into the interior of the protector, and are snapped
shut by
a mating locking ridge 220 and groove 222. Conveniently, the protector is
molded
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such that the rest position thereof is in the open configuration shown in
Figure 17
(a), thereby permitting easy positioning of cables within the interior. When
ready for
burial, the sidewalls may be snapped shut, as shown in Figure 17 (b).
Alternatively,
the rest configuration may be closed as shown in Figures 17 (b), with the
sidewalls
1208 being forcibly separated to permit entry of cables. The lower end 225
likewise
reaches a point, for facilitating burial within a soft substrate. A rigid
member such as
steel rod or cable is positioned within the interior of the protector 1200,
above the
cable array 10, for additional protection against damage by an accidental
shovel or
the like intruding on the protector. Alternatively, the cable or rod may be
molded in
place within the upper region 219 of the protector 1200.
Installation of cable protector 1200 or 201 is carried out by providing one or
more
cables (the number of individual fibre optic cables will be determined by the
capacity
of the interior space 1204, and is conveniently between 1 and 10 cables, and
most
preferably between 1 and 4 cables).
Installation of the second version of the cable protector 201 may be carried
out in a
somewhat different fashion. In an initial step, the metal rod or cable 209 may
be
positioned within the interior space 1204, or alternatively, the protector 201
may be
provided with the rod or cable 209 already in place within the interior 1204.
The
cables 10 are then positioned within the interior 1204 in a stacked array,
confined
between the walls of the protector in a stack one cable in width and the walls
1208
are then snapped shut. The closed protector 201 may then be buried within a
narrow channel. Alternatively, a slit may be formed within the substrate for
example
by passing a blade over the surface of the substrate at a relatively shallow
depth
which may be less than the depth of the protector 201. The protector 201 is
then
pushed downwardly into the substrate, with the relatively sharp and angled
lower
portion 225 serving to form a channel within the substrate to receive the
protector
201. Preferably, the protector 201 is pushed into the substrate to a depth
sufficient
to permit burial of the protector 201. For example, the overall thickness or
width of
the protector 201 may be approximately 6 to 10 mm and the top to bottom height
in
the order of 20 to 40 mm. The protector 201 contained in cables 10 may be
buried 2
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to 20 cm below the ground surface and preferable about 5 to 15 cm underground.
This is accomplished by pressing the protector 201 into the ground by the
desired
depth, followed by covering the disturbed soil region for example by back-
raking.
However, the channel or trench formed by the process may be sufficiently slim
that it
may not be necessary to replace the disturbed substrate, as this is likely to
happen
on its own over a short time. The elongate member 1200 is then positioned such
that the channel 1202 faces downwardly, and the cables are then positioned
within
the interior space 1204. The elongate member 1200, with the cables received
therein, is then set into the trench, in a face downwardly position (i.e. the
channel
facing downwardly), and then subsequently buried to restore the surface. It is
not
critical that the channel face directly downwardly, it may face e.g. sideways,
although a downward facing direction is preferred to minimize entry of soil
into the
channel 1202. One or more nodes as described above may be formed in this
version, in the same
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manner as described above.
It will be seen that the present invention has been described by way of
preferred embodiments of various aspects of the invention. However, it will
be understood that one skilled in the art may readily depart from the
embodiments described in detail herein, while still remaining within the
scope of the invention as defined in this patent specification including the
claims thereto.
