Optical waveguides – Accessories
Reexamination Certificate
2002-02-07
2004-10-19
Bevernick, Rodney (Department: 2874)
Optical waveguides
Accessories
C385S100000
Reexamination Certificate
active
06807355
ABSTRACT:
CLAIM OF PRIORITY
This application claims priority from Canadian Patent Application No. 2,337,284 to Dofher, entitled “Subsurface Fibre Optic Cable Network Installation” filed Feb. 15, 2001.
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 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. Pat. 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, 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. Pat. 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 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 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.
Bevernick Rodney
Stahl Mike
Storm & Hemingway LLP
TeraSpan Networks, Inc.
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