EoW September 2011

technical article

Riser cable

Strain gauge

Misalignment

Pulling direction

Pulling grip

Duct

Duct

Gap size

▲ ▲ Figure 4 : Testing setup

An additional advantage of this cable is the extremely small bend enabled by ClearCurve ® [2] fibre that allows discreet storage of fibre in the building, either for tether or for excess pigtails lengths. The flexibility and the small outer dimensions of the riser cable assembly ensure the very easy installation of the cable and routing through the wall or on the various levels of the building.

duct congestion. The installation process was simulated for several duct diameters and shapes both with and without cop- per cables already installed. Additionally, duct misalignment and gap size shown in Figure 4 were considered. Tests were performed for 3m duct pipes with different dimensions. This simulates typical 3m distances between floors in the MDU building. Each cable was pulled 3 times for every configuration. Figure 5 shows the pulling force for a 6x4 configuration measured for 3 duct with various inner diameters (ID) and with different filling ratios. Results showed that the most important factor is the number of riser tap points, which will be pulled simultaneously through the duct. However, the pulling force for different fill ratios depends also on copper twisted pairs arranged inside the duct.

OD = 7.6mm

OD = 9.0mm

▲ ▲ Figure 3 : Micromodule cable (up to 144f)

delivered to the deployment site ie MDU. The riser assembly is built according to the exact individual MDU architecture. Only very basic parameters like the distance between floors (F) and the distance from the basement distribution terminal to the first floor breakout point (B) have to be provided in order to enable this ( Figure 2 ). Based on this information even installers not used to handling fibre can deploy the proposed cable very quickly. The basement tail length is predefined at 120cm for easy connection into the basement distribution terminal. The length of the individual breakout tethers at the floor level depends on the given floor height (F) and are predefined as F-15cm as the maximum length. In order to minimise the cable diameter during installation the connectors at each floor level are staggered along the main cable during the installation procedure. The cable assembly comes with a pulling grip for easy installation. The extension distance from the last tap point to the pulling grip is predefined at 5m. Different connector types such as SC or LC can be chosen for the complete assembly. In order to route vertical cables efficiently and unobtrusively inside buildings, Corning’s design efforts for this product focused on smaller diameter and more flexible units leading to FRNC micromodule cables as shown in Figure 3 .

2 Installation conditions

One of the most critical issues related to cable installation is pulling through the vertical duct already installed in MDUs ( Figure 2 ). The following tests were performed to simulate installation conditions and define installation limits of the cables in terms of

▼ ▼ Figure 5 : Puling force vs Duct fill ratio

PF Pulling force [N]

Duct fill ratio [%]

70

EuroWire – September 2011