Advantages of Drop Cables in FTTH

The drop cabling forms the final external link to the subscriber and runs from the last FCP to the subscriber building with a distance restricted to less than 500 meters and often much less for high density areas. 

The drop cables will contain only 1 or 2 fibres for the connecting circuitry and possibly additional fibres for backup or for other network architecture reasons. The drop cable will normally provide the only link to the subscriber, with no network diversity.

For underground networks the drop cabling may be deployed within small ducts, within micro-ducts or by direct burial to achieve a single dig and install solution.

Overhead drop cables will feed from a nearby pole and terminate onto part of the building for routing to the subscriber fibre termination unit.

The above may take the form of pre-terminated or pre-connectorised cable assemblies to achieve rapid deployment and connection and to meet economic and minimal disruption demands.

Air blown cables and fibre units are able to enter through the building fabric using suitable micro-duct products and route internally within the building. This will form part of the internal cabling network with the building entry device acting as the transition point for the micro-duct (external to internal material grade).

Drop cables can be divided into 3 types:

- Direct buried cable

- Blown fibre cable

- Aerial cable

Direct buried cables are available in 2 constructions; non-metal, and with metal protection (corrugated steel).

The advantage of the metal protected cables is their very high crush resistance and high-tension load.  New non-metal strain relievers and protective sheets have been developed to give non-metal direct buried cables similar performance to metal protected cables. On average, non-metal cables are lower in cost.

Direct buried drop cables are available in fibre count from 1 to 12 (typical 2- 4). Direct buried cables and blown fibre cables can be pre-connectorised which gives an advantage on installation (less installation time in the home and better planning).

Direct Buried Drop Cable with Armour Protection

Blown fibre cable consists of a direct buried micro-duct (typical sizes inner tube: o.d 3, 4 and 5 mm) through which a fibre unit or micro-cable can be blown. Typically 2 to 12 fibres can be blown in this duct cable.

Air Blown Unit Drop Cable

Aerial cables are available in 3 types:

- ADSS: All Dielectric Self Supporting

- Figure 8 (cable fixed to a steel wire)

- OPGW (optical ground wire)

Aerial cables

Both ADSS and Figure 8 cables can be used as a drop cable for fibre to the home applications. OPGW cables are mainly used in power line connections.

ADSS cable is a non-metal reinforced cable with typical tensile load up to 5000 Newtons and fibre counts from 2 to 48.

The Figure 8 cable consists of a central tube cable fixed to a steel wire (see picture). Typical fibre counts are 2 to 48. The tensile load is typically 6000 Newtons.

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