 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
Infrastructure Deployment Technologies
This section provides a detailed analysis of available Infrastructure Deployment Options. None of the options listed represent any form of importance or acceptance. Each option offers features and benefits as well as limitations. Deployment options may well be used in combination.
1 Conventional Duct Infrastructure
This is the most conventional method of underground cable installation and involves the creation of a duct network to enable subsequent installation of cables by pulling, blowing or using floatation techniques. This may comprise a large main duct that contains smaller sub-ducts (for individual cable installation), a large main duct into which cables are progressively pulled one over the other as the network grows or a small sub-duct for the installation of a single cable. Duct installation provides the easiest and safest deployment method and also enables further access and reconfiguration. As with direct burial (below) consideration needs to be given to other buried services. Efficiency of cable installation in ducts relies heavily on the quality of the duct placement; this applies to all installation methods.
| Necessary main elements · Ducts and possible sub-ducts · Duct cables · Branch-off closures |
 |
1.1 Product Map
1.2 Duct network
The use of a single duct maximizes the number of cables that can be installed but full ducts make it difficult to
extract older cables (typically at the bottom of the duct) to create room for new cables. Using sub-duct may
reduce the total number of cables that can be installed, but at least older cables can be removed and new ones
installed. It also allows the use of cable blowing as well as cable pulling, since it is easier to obtain an airtight
connection to the sub-duct.
Typical duct sizes are 110mm, 100mm or 90mm for main duct and 50/43mm (50mm outer diameter, 43mm
inner diameter), 40/33mm, 33/26mm or 25/20mm for sub-duct. Smaller ‘microducts’ may also be deployed (see
below).
Cables are installed into the ducts by pulling, blowing or floating. If they are to be pulled, then the duct either needs to contain a pre-installed draw-rope or to have one installed by rodding and roping. If they are to be blown in or floated, then the duct and any connections between sections of duct need to be airtight. The inner wall of the sub-duct is manufactured to ensure low friction with the cable sheath. This is typically achieved with a low friction coating. Alternatively, the sub-duct could contain a low friction extruded profile and/or special duct lubricants can be used.
A number of factors govern the continuous length that can be pulled or blown, including coefficient of friction, bends in the duct route (vertical as well as horizontal), the strength or weight of the cables and the installation equipment used. The cable diameter should not be too large compared to the duct inner diameter. Fill ratios should be calculated as part of the planning process. For cable blowing operations the duct joints must be airtight. For existing networks the condition of the ducts should be checked for any potential damage and suitable space and capacity for future cabling.
1.3 Type of Ducts Main Ducts – Underground Systems The feeder ducts run from the Access Node to the FCP. The number of ducts required will be dictated by the size of the FTTH area and the size of feeder cables used. Consideration may also be given for more than one cable to be installed in a single duct to save vital duct capacity (e.g. using over blowing or pulling techniques). Ducts sizes will range from 25 - 50mm O.D. Larger ducts of 110mm O.D may be used and these may contain smaller sub-ducts between 20-40mm O.D. The duct material is normally HDPE |
Example – Main HDPE Duct cross section |
 | Pagini: 1 2 3 4 5 6 7 8 9 |  |
|
|