Fiber optic network construction is linking together all forms of digital infrastructure to ensure that optical telecommunications traffic can seamlessly reach end users at the lowest possible cost.
Fiber optic construction is bringing high-speed internet connectivity to homes and businesses in cities around the world. These networks are constructed both underground and through aerial fiber, at an average cost of $1,000 to $1,250 per residential household passed or $60,000 to $80,000 per mile.
Dgtl Infra provides an in-depth overview of fiber optic network construction, including its density, as measured by strand count, and the time it takes for a fiber network to become operational. Additionally, we detail the entire process for deploying both underground and aerial fiber. Finally, Dgtl Infra reviews the costs of fiber construction and what the key drivers of these costs are, using real-world examples.
What is Fiber Optic Construction?
Fiber optic construction is a cost-effective way of bringing network access to areas with significant end user voice, video, and data traffic.
How is Fiber Constructed?
Fiber optic networks are constructed through the placement of both underground and aerial fiber, meaning that fiber does not always have to be buried.
- Underground: Fiber optic cable is placed in a conduit system, which is buried through plowing, trenching, jack and bore, multi-directional bore, or directional bore techniques
- Aerial: Fiber optic cable is placed on top of utility or telephone poles
How Many Strands are in a Fiber Optic Cable?
Fiber optic cables consist of many glass fiber strands, with existing networks typically having been built with 36, 48, 72, 144, and 288 fiber strands in each cable. However, newer fiber optic cables are being built with 432, 864, and 1,728 fiber strands in each cable, which provides fiber optic networks with built-in capacity for future growth.
Higher strand count fiber optic cables are particularly deployed on backbone (core) network routes from a telecommunications provider’s central office (CO).
Fiber Route and Strand Miles
Fiber route miles signify the length, measured in non-overlapping miles, of a fiber optic network. While fiber strand miles represent the number of route miles in a network multiplied by the number of fiber strands within each fiber optic cable on that network.
As an example, a 10 mile fiber route with 288 fiber strands would be commonly referred to as having 2,880 fiber strand miles.
How Long Does Fiber Construction Take?
As a general rule, fiber construction takes 6 to 10 months for a network to become operational, after the beginning of a build-out. However, the construction timeline for a new fiber optic network varies depending upon the number of route miles to be constructed, the number of homes or premises targeted for connection to the network, and the general deployment of the network.
Fiber Construction Process
The fiber optic network construction process involves the placement of both underground and aerial fiber, which are each detailed below:
Underground Fiber Construction Process
How is Fiber Cable Buried?
Fiber optic cable is buried in tubes, known as a conduit, which are placed by means of plowing, trenching, jack and bore, multi-directional bore, or directional bore techniques. As shown below, machinery from manufactures like Ditch Witch, is used to plow, trench, and bore into the ground:
Conduit Construction for Fiber Optic Cables
Conduits are usually constructed on a level grade, parallel to the surface of the ground, with only gradual changes in grade elevation over the fiber run. Fiber optic cable is placed into three primary types of conduit: HDPE (polyethylene plastic), PVC (vinyl polymer plastic), and steel.
An innerduct, which is a separate tube within a conduit, divides the larger conduit into subsections. Therefore, in this common approach, no fiber optic cable is run directly in any split/solid conduit, without an innerduct.
Typically, if conduit is laid along paved city, state, federal, and interstate highways, as well as railroad crossings, bridges, or through tunnels, then it will be encased in steel conduit. Otherwise, HDPE and PVC conduits are viable options for placing fiber optic cables.
Fiber Optic Cable Installation in Conduit
Once the conduit has been buried, the fiber optic cable is installed, “pulled”, or “jetted” through the conduit. Specifically, larger installations generally occur through either pulling or blowing:
- Powered pulling winch and hydraulic powered assist pulling wheels, which apply a maximum pulling force to the cable of 600 pounds
- Sealed pneumatic cable blowing system, which uses compressed air to “jet” multiple innerducts into the conduit
Usually, 65 to 150+ feet of slack cable will be left in all intermediate handholes & manholes, splice locations, and facility locations (e.g., points-of-presence).
How Deep Should Fiber Optic Cable Be Buried?
Fiber optic cable is buried in conduits, typically at a depth of 3 feet to 4 feet, which is equivalent to 36 inches to 48 inches underground. In many instances, cable installation agreements will stipulate a minimum depth of 42 inches, with certain environments requiring the conduit to be placed at even greater depths.
For example, depths of 48 inches can apply for conduit placed in ditches adjacent to roads, highways, railroads, and interstates. While 60 inches is often the minimum requirement for conduit placed across streams, river washes, and other waterways.
What is Microtrenching for Fiber?
Microtrenching is a process used to bury fiber optic cable that reduces the time to build a network and bring on customers, while creating less disruption (e.g., no road closures) in the area where fiber is being placed. However, microtrenching does not reduce the cost to construct a fiber optic network.
Uniquely, microtrenching buries fiber optic cable in the ground at much shallower depths of only 8 to 16 inches deep, while creating a trench that is only 1 to 2 inches wide. As shown in the video below, the microtrenching process can support conduit that is over 3 inches in diameter.
Aerial Fiber Construction Process
How is Aerial Fiber Installed?
Aerial fiber optic cable is installed by stringing and bolting overhead cables on top of existing utility and telephone poles. This aerial fiber construction can be performed though a new pole attachment or by utilizing a technique called overlashing, which involves the attachment of a new cable to an existing cable.
Overlashing is accomplished by placing the new cable beside the existing cable, and “lashing” or binding the two cables together with spinning wire that is wrapped around both cables. This technique allows for the addition of new aerial fiber optic cable, utilizing existing pole attachments, without the requirement for additional space on the pole.
Often, aerial overlash and pole attachment rights are secured by fiber optic providers, from utility companies, to utilize space on their utility poles.
Fiber Construction Costs
Discussed below are underground fiber construction costs (i.e., laying fiber), the key drivers of fiber construction cost variances, two real-world examples of fiber construction costs, and the lower inherent cost of aerial fiber installation.
How Much Does it Cost to Lay Fiber?
On average, it costs between $1,000 to $1,250 per residential household passed or $60,000 to $80,000 per route mile, to “lay” or bury fiber optic cable. Households passed refers to fiber that is built along residential streets, but excludes the connection or “drop” into the home, which uses lateral fiber connections.
Drivers of Fiber Construction Costs
Fiber construction costs vary significantly, depending on factors including labor, population density, depth or height of the fiber deployment, terrain, equipment, whether or not the provider has existing conduit, make ready costs, and permitting costs. Below are further details on each of these drivers of fiber construction costs:
- Labor: Physical labor comprises the single largest cost component of fiber builds, often making up over 60% of total fiber construction costs
- Population Density: The United States population density is about 93 people per square mile, which is relatively low on a global basis. Fiber construction costs are lower for densely populated urban environments and meaningfully higher in sparsely populated rural areas
- Depth or Height: Fiber optic networks are constructed through the placement of both underground and aerial fiber. Underground fiber optic cable built in a conduit system is significantly more expensive than aerial fiber placed on poles
- Terrain: Fiber needs to be constructed across different types of land, which can be more or less expensive to traverse. For example, fiber is often built around or through mountains & hills, valleys, and plains, as well as natural elements like rivers, rocks, and soil types
- Equipment: Fiber optic transmission and other electronic equipment costs will vary depending on the length of the fiber optic network being constructed
- Existing Conduit: Lower buried fiber construction costs benefit carriers that own existing copper conduits, which can be used to pull fiber optics through. For example, Frontier Communications, an incumbent local exchange carrier (ILEC), notes that it has a ~$40 benefit per location passed by utilizing its existing conduit capacity
Additional Drivers of Fiber Construction Costs
- Make Ready Costs: expenses associated with securing rights of way, franchises, conduit leases, property leases, and pole attachments. Incumbent operators generally avoid these “make ready costs” if they own poles and/or conduit
- Permitting Costs: municipal and other governmental permits, licenses, and authorizations required to be obtained prior to commencement of construction
Examples of Fiber Construction Costs
Below are two examples of fiber construction costs, using real-world deployment data, from the Fiber Broadband Association / Cartesian and internet service provider (ISP) Shentel.
1) Fiber Broadband Association and Cartesian
The Fiber Broadband Association (FBA), an all-fiber trade association, and Cartesian, a specialist consulting firm, produced a study on the cost, in the United States, to construct a fiber to the home (FTTH) network that passes different populations, based on their household density per square mile. Particularly, this study yielded the following cost ranges for urban and rural areas in the United States:
- Urban: Costs range from $700 to $1,500 per household passed
- Rural: Costs range from $3,000 to $6,000 per household passed
Fiber to the Home (FTTH) Costs to Pass per Household
2) Internet Service Provider (ISP) – Shentel
Shentel (NASDAQ: SHEN), a broadband internet service provider (ISP) in Virginia, West Virginia, Maryland, Pennsylvania, and Kentucky, through its Glo Fiber brand, is targeting 450,000 homes passed by 2026. In terms of population density, Glo Fiber’s service targets higher density urban and suburban areas.
Glo Fiber is a greenfield fiber overbuilder deploying 10-gigabit symmetrical passive optical network (XGS-PON) fiber-based transmission technology, while seeking to deliver bandwidth speeds of up to 2 gigabits per second (Gbps) to customers.
Given the discrete nature of this fiber to the home (FTTH) initiative, Shentel identifies key data points relating to its fiber construction costs. Specifically, the company estimates that its build capital expenditures (CapEx) will average $1,200 per passing, based on a range of $1,000 to $1,400 per passing.
How Much Does it Cost to Install Aerial Fiber?
On average, it costs between $8 to $12 per foot or ~$40,000 to ~$60,000 per mile to install or “overlash” aerial fiber optic cable. However, these costs will differ greatly based on the type of geographical area, with urban environments being the most expensive, followed by suburban and rural areas being progressively cheaper. To this end, rural areas have fewer obstructions, making pole attachments easier and more cost-effective for fiber networks.
As a reference point, Frontier Communications states that its fiber networks receive a ~$30 benefit per location passed, by overlashing its aerial copper lines.
Importantly, aerial fiber deployments require only days or weeks to connect, as compared to underground fiber construction, which can take several months.
Aerial fiber construction costs include pole attachment expenses, fiber materials, installation, and splicing. Additionally, a significant component of aerial fiber network construction expenditures are the “make ready costs” which involve engineering and rearrangement of cables to prepare utility or telephone poles for the attachment of new fiber optics.