A cable design engineer, after reading the customer specification decides the construction details of an optical fiber cable. One of the important considerations he/she needs to take is whether extra protection is required or not. If extra mechanical protection is required, armoring is one choice. Here we will see the factors that influence the choice of armor.
Typical optical fiber cables that are laid in ducts are the single sheathed type. After the field survey and prior to the network design, network owners gather information on the field where their network infrastructure will be constructed. If extra mechanical protection is required, they need to consider it for not only fiber optic cables but also for other infrastructure components.
Hence, in deciding whether or not to use armoring and in choosing between the various types of construction, multiple factors play their roles. Very careful consideration should be given to the local conditions of installation. Most of this information would be provided by your customer. In case you do not receive such information, it is always better to check with your customer before you start designing the cable.
The factors that influence the necessity of armoring are written below;
1. Cable Deployment method: Where your customer will install the cable? Is it in the duct or they bury the cables directly in the soil?
2. Micro-trenching along the road: If your customer plans to install the cable by making micro-trenches on a road where the vehicle traffic is heavy, you need to consider suitable armoring such as wire armoring or double corrugated steel tape armoring etc.
3. Type of Sheathing/Jacketing Material: You need to care before committing the armoring on a PVC cable. Confirm the type of material and its compatibility with the armoring material. A PVC material may not be a good friend of the copolymer material attached to the steel tape. Steel wires are good with PVC or LSZH materials.
4. Ask your customer if they plan to install electrical cables along with fiber optic cables. If the answer is Yes, then it is better to use non-metallic armoring materials. It is not due to the concerns of signal interference, but for the safety of people handling the fiber cable during repairing and installation. An exposed power cable core if comes in contact with the ) whether other cables are or may be laid along the same run;
5. Soil Nature: If your office is located in France and you design a cable for Vietnam, you surely need to know the environmental conditions especially the soil conditions. This is significantly important when the cable is of direct burial type. If your team have no idea of the nature of the soil, tell them to get details. You should know whether the terrain is rocky, sandy, corrosive or not apart from the presence of micro-organisms.
6. Details of Trench: International guidelines are available for the depth of the trenches. Depth shall not be less than half a meter but for larger cables may go deeper such as 0.8 meters.
7. Rodents and Insects: Rodents in France and that in Vietnam are different. If your armored cable design passes the anti-rodent test in France with the French-rats, it doesn’t guarantee the performance in Vietnam. Believe me, the rats in Vietnam are really big. Do a google search and reconsider the corrugation materials, the number of layers, thickness, and diameter etc. It would help you a lot later to reduce complaints from the field.;
8. Lightning attack: It is said that fiber optic cables are immune to the electricity but what if it comes in billions of watts. Not only cable almost all telecommunication infrastructures would turn into carbon. A proper earthing can save.
I know the list is not full, but just tried to put those situations, where armoring is unavoidable. If you know any other points, please use the comment box below.
Note: Armoring is not limited to the direct buried cables but done for aerial cables as well where the installation environment demands such protection. For example in Myanmar and Brazil where the aerial cables are prone to attack from the squirrels.
You may also be interested in Type of Armoring in Fiber Optic Cables