Dead-ending and suspension :
which network equipment for feeder networks ?
In telecommunications, the feeder part of the access networks has an important role to play as it connects the metropolitan collection networks to the access nodes, subsequently used for connecting end-users.Usually, this network segment is comprised between the Point of Presence (PoP) and Fiber Distribution Point (FDP), which is a flexibility point in the access network infrastructure. Fiber roll-outs on feeder networks represent thus a major challenge for Telcos and telecom infrastructure installers.
To make sure that the selected dead-ending and suspension devices are perfectly suitable for your fiber roll-out project, it is essential to consider the specific conditions in which the project will be carried out. As a consequence, a cable clamp or a helical dead-end installed on a feeder networks must correspond to:
- the characteristics of the cable to be deployed
- network configurations
- the installation climatic conditions
Built and deployed for hauling enough optical fibers so to connect all potential end-users residing in a given area, feeder cables present larger diameters than distribution cables or drop cables, going from 10 to 18mm. Hence, a first verification step consists into making sure that the chosen dead-ending or suspension device offers a range of permissible diameters corresponding to the diameter of the cable to be installed in overhead configuration.
In addition, fiber optic feeder cables are deployed on MV networks or telecommunications infrastructures characterised by long spans, typically of 100 to 200 meters. This implies higher tensile forces, as well as a higher pressure exerted both on the cable’s outer sheath and on its entire structure. To cope with these mechanical stresses and enable the spreading of the tensile strength over a longer surface, there are two technological solutions: the long span clamp and the dead-end cable grips.
Other parameters specific to the network configuration such as the cable sag, the rugged terrain or the line deviation must be examined in order to choose the most suitable device to your needs. Moreover, climatic conditions such as wind force, æolian oscillations, eventual ice loading or temperature variations are also criteria to be considered for the network equipment validation.
Top solutions for feeder cables fastening in overhead configurations
Depending on the structure of the cable to be deployed, several technological solutions are available. Thus, for the dead-ending of figure-8 cables with dielectric messenger and HDPE insulator on feeder networks where spans do not exceed 180 meters, long span clamps included in the ACAL range offer a mechanical resistance of 1200daN. These cable clamps for dead-ending are engineered with an aluminum open, conical body, a jaw with two plastic wedges and a 500m long flexible bail. The different versions included in this product range cover a wide range of cable diameters, from 10 to 18mm.
For the anchoring of aerial round ADSS fiber optic cables, deployed on medium spans of up to 180 meters, the most suitable solution is to use helical dead-ends with armor rods. These spirals using the preformed technology are compatible with self-suporting cables with diameters from 10.5 to 18.6mm. They present twisted wire legs with a total length of 820mm and armor rods of 1015mm. By completely covering the cable, the armor rods act like a protective shield: it enables the equal distribution of the exerted mechanical forces over a significant length of the cable. Moreover, the armor rod pushes forward the mechanical load onto the helical dead-end structure that is to be installed on the top of it. It provides additional rigidity and enables thus the maintaining of a large enough bend radius on the support side. This technological solution is particularly adapted for the most demanding installation environments. Generally, reinforced spirals are used as anchor clamp for power networks, as they are designed to meet high load conditions. Their installation requires additional accessories such as thimbles to protect the attachment point, turnbuckles to adjust tension or shackles used as intermediate items between turnbuckles and pole line hardware fittings mounted on telecom poles such as brackets.
For the suspension of round ADSS cables rolled-out on HV infrastructures and where spans do not exceed 180 meters, DSAL mobile suspensions devices are more suitable solutions as they are compatible with a large range of cable diameters (8.5 to 21mm) and their installation is fast. For short span network configurations of up to 90 meters, the suspension of round feeder cables with diameters from 5 to 17mm can also be performed with JHC J-hook suspension clamps.