Selecting armored fiber optic cable for direct burial or a tracer wire element to install with your next underground build might allow you to “check the box” that your plant can be found. However, are you creating an effective system to do so for the life of the network? I ask network operators to reflect on how you specify and order materials based not just on capex, but also on some of the hidden operating costs with toning options on the market today.
I recently compiled one mile worth of connected cost data for the several types of toning options associated with fiber builds. These figures only include materials, and they do not include any labor estimates. We will look at the implications of using cable armor versus a tracer wire element. While this article applies to telecom networks, it does include valuable cost comparisons for locating products used for all utilities.
Armored fiber optic cable in the United States gradually morphed over the last 10-15 years. The primary reason for armor underneath the sheath is mechanical protection for direct burial purposes. It may also shield against rodents, but that shield along with toning capabilities are additional benefits secondary in the design.
Fiber armor was once thick, corrugated stainless steel with excellent strength and corrosion resistance. Installers wanted a cable that was more flexible and easier to access, so cable manufacturers switched to a chrome-coated steel that is thinner, with an additional coating for corrosion resistance. This armor is commonly known as “lite armor.” It is worth noting that some standards written years ago for the conductivity requirements of cable armor may not be met by the current alternate materials and thicknesses used in lite armor.
The cost of lite armor in fiber optic cables is typically a 15-20% premium regardless of the strand count. Therefore, the higher the fiber count, the higher the total cost of the armor in that cable. Using current market pricing, armor on a mile of 288 strand fiber costs 81% more than 24 count over the same distance. This has great implications for middle mile versus last mile builds, which might make other materials more attractive, such as using a tracer wire and duct instead on long haul applications.
Chart A compares a few of the lower cost scenarios. The pull tape with tracer includes one mile of tape with conductor and connectors. The other two figures include just the cost of the conductive material in that product. This shows it is less expensive to order the 24 count with armor than it would be to order a dielectric cable with the intent to install a pull tape with conductor along with it.
The effort to specify and purchase armored cable will be for naught if the proper termination and installation procedures are not followed. Changes in cable design, coupled with the rigors of outside plant environments, have created the need for new recommended procedures. As an example, manufacturers have tweaked the “bullet bond” connectors to accommodate distinct types of fiber on the market. Are you still using the same b-bonds? Are the proper connectors being used to ensure the integrity of the system? Are splice closures being supplied with ground lugs?
New connectors exist on the market to provide easier access to cable armor without exposing the sheath for toning and grounding purposes. This eliminates the need to use a
splice closure if the only purpose is to bond at that location. These new connectors use Insulation Displacement Contact (IDC), which leaves little room for installation error, and
they are designed to hold through temperature cycles.
In addition to proper connectivity for toning, the armor must be bonded to protect from lightning strikes and other transient voltages. For some, the risk a conductor wrapped
around fiber poses is too great no matter how well the cable is bonded. In this case, a separate tracer wire would provide additional protection depending on its proximity
to the cable. If you are going to place tracer inside the same pathway as the cable, you still expose the cable to damage from transient voltage hitting the tracer wire. Let’s look at
the flavors of tracer wire to see which might be the best fit.
Often the specifications are written on projects to simply, “install a 12-gauge tracer wire.” Leaving the requirements open to interpretation of the installer can lead to a costlier and
less effective installation.
In Chart B, I compare the costs of one mile of tracer wire, including their splices over that distance. As you can see, copper clad steel (CCS) wire is more cost effective than THHN with solid copper conductor. Even though it is less expensive, the CCS wire is better to use as
tracer wire for several reasons.
• CCS tracer is made with a polyethylene jacket UL rated for underground use; THHN is not.
• CCS has no scrap value, making it less attractive to thieves.
• CCS is stronger than solid copper conductor wire, which allows it to be plowed or installed by directional drill.
IDC connectors are also available for CCS tracer wire, which makes for simple and secure tool-less installations. Those connections will resist corrosion, thus increasing the life of the wire. However, even the polyethylene jackets of the CCS wire can become compromised, thus limiting the life of the tracer wire. Certainly, you would want the tracer
wire to last as long as your network.
Waterblock tracer wire is an option that significantly increases the life of the system. It uses a smaller, solid conductor surrounded by waterblock elements in a polyethylene
jacket. If the jacket is pierced by rocks during backfill, the conductor remains protected.
The waterblock tracer wire is also designed as a system with IDC branch and splice connectors, further increasing its reliability.
Using my previous example of one mile worth of connected material, Chart C shows how the cost of waterblock tracer wire compares to CCS wire and armor in a higher count cable. While the waterblock wire is more expensive than copper clad, it costs less than adding armor to a mile of 288 count fiber.
One additional benefit to the waterblock tracer design is that if the wire becomes compromised by transient voltage, the wire fails at the point where the surge in voltage occurs. Thus, the wire does not carry those transient voltages along to damage additional points in the network. This significantly reduces the cost and time to restore the fiber as well as the tracer wire.
However, if you specify a waterblock tracer wire and splices are made by stripping wire and wrapping connections in electrical tape, all the cost benefits go down the drain. The cost of the proper connectors is minimal when you compare each solution. Why should you lose sleep over whether your network is found or not?
If your engineers take time to specify every piece of fiber connectivity for the sake of network performance, please do not overlook trace line systems for the sake of cost.
Matt Brice is the Product Sales Manager at Comstar Supply and has served seven years of experience in the industry. Comstar Supply is a distributor of telecom and utility outside plant materials. Matt can be reached at firstname.lastname@example.org.