EoW January 2008

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few fibre splice and connection points, it is cost efficient to joint ducts and it also needs less skilled labour. Furthermore, a more reliable solution is achieved compared to a solution with optical connectors. The solution is exemplified by the following scenario, shown in Figure 1 . This is a typical residential area consisting of detached houses. In this scenario, only one fibre joint closure on every 5 th pole is required. From this small closure, 20-24 homes are served. The network connecting the joint closures towards the splicing cabinet (with splitters) is referred to as the main distribution cabling. The drop cabling from the end user is carried out by installing single drop ducts connected to the main duct, see Figure 2 . One simple duct joint, see 3.3 , typically serves four subscribers from the closest pole. Note that no fibre splicing is done in the duct joint. As described, this design enables a single duct assembly for feeding a long distance of poles. The number of fibre splices will be kept to a minimum since splicing between air-blown fibre and air-blown micro cable is only required on each 5 th pole. To reach all customers in the described scenario the distribution cable needs to be installed up to 1,000 metres and the drop •

cable only up to 200 metres. The blowing installation distances are further discussed under section 4.4. Figure 5 : Example of fibre joint closure with two main duct assemblies terminated ▲

Figure 6 : Example of duct joint with four single duct assemblies jointed to one multi-duct assembly ▲

3. Products 3.1 Duct assemblies

The duct assemblies are made in different configurations, see examples in Figures 3 and 4 . The ducts are self supporting, either as figure-8 or with an under-sheath integrated strength member. By combining both 10mm ducts for micro cable (distribution cable) and 5mm ducts for air-blown fibre (drop) in the same assembly, an installation of an access network with only one duct assembly between poles is possible.

Figure 7 : Tension clamp for multi-duct assembly

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Figure 8 : Four-fibre EPFU (Enhanced Performance Fibre Unit) ▲

3.2 Fibre joint closure A fibre joint closure for this application is unique in many aspects. It must be able to handle several different features, such as ducts (both for blown fibre units and for micro cables), fibre management and splices, mid-span storage of micro cable fibre units and storage of blown fibre units. It should be pole mounted (and in some cases span-mounted). Finally, all of this has to be squeezed into a small package, see Figure 5 . Aesthetics are very important. The closure must be visually discreet. In principle, the closure does not exceed the width of the pole and as such is visually hidden from most views of the pole. The length of the closure is also important. 3.3 Duct joint A duct joint is needed to branch out single ducts from the principle duct assembly to any premises requiring service. The duct joint is of a span-mounted design. It typically enables four ducts to be accessed at every pole span, enabling access to the four premises serviced from that particular pole. The duct joint that provides for this distribution from the main duct assembly is a key design feature. 3.4 Fittings The aerial duct support fittings are of the wedge clamp type and very easy to install,

Figure 4 : Example of a self supporting drop duct with 1 x 5mm inner duct ▼

Figure 3 : Example of an aerial multi-duct assembly with 8 x 5mm ducts for air-blown fibre and 2 x 10mm ducts for micro cable ▼

Figure 2 : Installation example – Aerial installation of FTTH network with air-blown fibre and cable ▼

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EuroWire – January 2008