Fiber optic cable is offered with two different types of armor – aluminum interlocking armor for indoor cables and corrugated steel tape for outdoor cables. The armoring offers an added layer of mechanical protection to the cable. The differences between the two types of armor are the material that the armor is made of and the way it is applied to the cable. Aluminum interlocking armor is made of – you guessed it – aluminum – and it is wrapped helically around the fiber cable. This type of armor is used in indoor rated cables. The second kind of armor is corrugated steel tape. This armor is composed of coated, corrugated steel and it is folded
longitudinally around the cable. Corrugated steel tape is found in outdoor rated cables. Fiber optic cables are offered in many different cable constructions, each with their own advantages and disadvantages. Armored cables have some benefits when you are installing them, and there are applications where it will be more cost effective to use this kind of cable. Some of these cables are more versatile than others, and if you have some on hand, it may help you to be ready for any situation (like an unexpected network outage). Other times the decision will come down to the engineer and the type of cable they prefer for the job. There are costs associated that can help you make the decision about the style you choose. Armored cable costs more than non-armored, but the labor to install it may be a less expensive, and this could make it more feasible to install armored cable. Below we will discuss a few different cable constructions and where you can pick between the two, armored versus non armored.
Distribution Cable is a tight buffered cable construction; inside of the outer jacket is a layer of aramid yarn and multiple fibers with 900um tight buffer jackets. Distribution cables are multi fiber cables that are used for indoor applications. The color of the outer jacket for single mode is typically yellow and for multimode the outer jacket can be orange, aqua, magenta or lime green depending on the multimode fiber type. Having a 900um jacket on the fibers allows you to be able to terminate a connector without having to do a build up on the fiber. Where this cable is being run indoors will help to determine if armor is needed. When fiber optic cable is being run in harsh environments or high traffic areas, it would be good to have the extra protection of the armored cable. This may be in a warehouse environment or it may be above a ceiling that is accessed regularly. Indoor armored cable uses an aluminum interlocking armor that helps to protect the fiber cable, along with increasing the durability of the fiber run. Sometimes you may be required to run cable in conduit indoors. The aluminum interlocking armored cable can help eliminate the need for conduit and it can be substituted for running conduit. Installing conduit can increase the cost of the installation because you have to spend time to place the conduit. Then you have to pull the cable through the conduit which means you have essentially doubled the labor costs to perform the installation. When using the aluminum interlocking armor cable, you now just have to pull your cable once. When running the armored cable in a cable tray or under a floor or through a ladder rack – any location where it will be installed and is not likely to be touched or disturbed then you probably do not have to use armored cable.
Indoor Outdoor Cable
Another style of cable that offers an armored or non-armored construction is Indoor Outdoor Cable. This type of cable typically has a black UV resistant outer jacket as well as moisture blocking material in the Kevlar or aramid yarn of the cable. There are two different types of indoor outdoor cable that you can use. One is known as distribution style and it will have 900um tight buffer like the indoor distribution cable we talked about above. Indoor/Outdoor distribution is the same construction as the above mentioned distribution cable, except it has a special black UV rated jacket to protect the fibers inside from the sun’s rays.
Indoor Outdoor is also available as a Dry Loose Tube construction. This is where the fibers have a 250um acrylate coating only, and they are arranged in separate buffer tubes with 12 color coded bare fibers in each tube. These are similar to the next category – Outside Plant Cable, but they do not contain any water blocking gel, hence the name “Dry”. Similar to the distribution style cable, this type of cable can be armored or non-armored. The armor used in the cable is aluminum interlocking armor. This type of cable cannot be direct buried, but the armor gives the fiber some extra protection in rugged environment settings. Oftentimes installers will use this when they need to run indoors and some distance outdoors as well. Rather than needing an interconnect box at the building entrance to transition from outdoor to indoor cable, this type of cable can be run in conduit outdoors and then be brought inside without transitioning to an indoor rated cable.
This type of non-armored cable can be used in multiple applications because it is so flexible in the ways that it can be deployed. Since you can run this cable inside or outside, some contractors will purchase this type to keep on hand because they can use it for a variety of applications. This allows them the flexibility to handle multiple situations without having to carry several different spools of cable.
Outside Plant (OSP) Cable
Outside Plant Cable is a cable construction that typically has gel or Icky Pic coating the bare fibers to give it extra water blocking protection. OSP cables are run either underground or in aerial applications. These gel filled cables can only be run inside a building up to 50 feet because of the toxicity of the fumes and smoke produced when it burns. Building codes regulate this distance and the cable run will need to be inspected once it is installed. The way that this cable is installed will help to determine if you will need armor or not. Aerial and buried applications can use either armored or non-armored outdoor fiber optic cable. Here we will focus on when the cable is buried in the ground.
When you talk about outside plant cable being buried, you have a couple options as to how you can accomplish the installation. The first option has to do with non-armored cable and involves the use of conduit or innerduct. When you are running conduit underground an armored fiber is not needed but can be used if desired, because it will give the cable extra ruggedness and it will help with locating the cable later.
Armored outside plant cable is made so that it can be direct buried and it does not require the use of conduit. This type of cable construction uses corrugated steel tape for the armoring. When you bury the cable, please know how deep the frost line is in the area where you are located because the cable will need to be buried below that line. The cable is buried below the frost line so it isn’t damaged when the ground freezes and “frost heaves”. Not only is armored cable suitable for direct burial, it is also used for rodent protection. So if you have rodent trouble, it would be wise to use the armored cable. Keep in mind that the armored cable will need to be bonded and grounded for protection from lightning strikes, especially when it is used for an aerial application.
What does bonding and grounding the cable do? Basically, bonding and grounding an armored fiber optic cable protects the cable and the equipment that it connects to from electrical currents such as current from faulty or exposed wiring or lightning strikes.
Although this article does not go into the details of all applications, it does give you an idea of a few different cable constructions as well as armored versus non-armored applications. Please remember that when you are doing fiber optic cable installs, whether it is your first time or if you are a seasoned veteran, you should make sure to do your homework on the geography of the location where you will be installing, as well as mapping the path where you need to do the installation.