FTTH Aerial vs Buried vs Microduct: Choosing the Right Outside Plant Method

Outside plant method selection is the single biggest cost decision in an FTTH build. A wrong call locks the operator into decades of higher OPEX, slower repairs, or stranded capacity. This guide walks through the three dominant methods used in North American FTTH today: aerial lash, direct-buried plow, and microduct with air-blown fiber. We compare cost, install rate, lifecycle, regulatory friction, and the test gear each method requires.

The Three Methods at a Glance

Each method places single-mode fiber between the OLT and the customer drop, but the construction technique, hardware, and long-term economics differ sharply.

Cost ranges assume a typical 144 to 432-fiber count cable in suburban North American conditions. Urban core with traffic control, restoration, and permitting can double these numbers in any method.

Aerial FTTH: Fast, Visible, Politically Loud

Aerial deployment lashes a fiber cable to an existing messenger strand on utility poles, or uses ADSS (all-dielectric self-supporting) cable that needs no separate strand. It dominates rural and small-town builds because the right of way already exists.

Where aerial wins

• Pole inventory exists: Joint-use agreements with the power utility give you ready right of way without permits or restoration.
• Rural spans: Long pole-to-pole runs (200 to 300 ft) are cheaper to lash than to plow through ditches and driveways.
• Visible repair: Cuts from tree falls, vehicle strikes, or ice loading are easy to locate and splice from a bucket truck.
• Future expansion: Adding a second cable on the same strand takes a single lashing pass, no new excavation.

Where aerial loses

• Make-ready costs: Power utility may charge $500 to $5,000 per pole to rearrange existing attachers, often more than the cable itself.
• Storm vulnerability: Hurricanes, ice storms, and tree-fall events take aerial fiber out for hours to days at a time.
• Aesthetic objections: Affluent neighborhoods and HOAs increasingly mandate undergrounding.
• Pole crowding: In some markets, the communications space is full and undergrounding becomes the only option.

Splice testing on aerial cable typically uses a 1km launch cable staged at the pole base to push the OTDR dead zone past the closure, since most aerial closures sit 30 to 100 ft from the bucket truck.

Direct-Buried FTTH: Permanent and Quiet

Direct-buried plowing places armored loose-tube fiber at 24 to 36 inches below grade using a vibratory plow or static ripper. It is the workhorse of suburban greenfield builds where pole right-of-way is unavailable or undesirable.

Equipment and crew profile

• Vibratory plow: Self-propelled or skid-steer mounted, places cable in a single pass without open trench.
• Locator: Required for One Call markouts before any digging.
• Restoration crew: Yard repair, sod replacement, and concrete cuts add 20 to 40 percent to the labor budget.
• Hand-hole and pedestal placement: Splice points sit in flush-mount enclosures every 1,500 to 3,000 ft.

Soil and terrain factors

Sandy and loamy soil plows easily at 4,000 to 6,000 ft per day. Rocky soil drops production to 1,500 to 2,500 ft per day and may require a rock saw, doubling the cost. Permafrost, high water tables, and dense root systems can make direct-bury impractical entirely.

Crews testing direct-buried splice points should use a tri-wavelength handheld OTDR at the pedestal, with the 1625 nm wavelength used for in-service maintenance after the link goes live.

Microduct and Air-Blown Fiber: Future-Proof at a Premium

Microduct deploys a bundle of small-diameter HDPE tubes (typically 7-way, 12-way, or 24-way) into the ground, then blows fiber units into individual tubes as demand grows. The first build costs more, but subsequent fibers are placed in hours instead of weeks.

Why operators are moving to microduct

• Cap once, expand forever: Adding a second operator or upgrading from 144F to 432F requires no new digging.
• Faster restoration: A cut tube can be re-blown without excavating the entire duct path.
• Reserved capacity: Empty tubes can be leased to wireless carriers, municipalities, or wholesale tenants.
• Lower lifetime OPEX: Twenty-year TCO often beats direct-bury despite higher upfront cost.

Air-blown fiber operations

A blowing machine pushes fiber units through the microduct using compressed air at 100 to 150 PSI, typically achieving 3,000 to 5,000 ft per shot. Bend management is critical: each tube must maintain a minimum 12-inch bend radius through hand-holes and risers, or blowing distance drops sharply.

After blow, every tube is tested end to end with a tri-wavelength PON power meter against the design loss budget. Continuity is verified with a visual fault locator before splicing into the distribution cabinet.

Cost Modeling: A Five-Year TCO Comparison

Sticker price misleads. The right way to compare methods is total cost of ownership over the realistic life of the plant. Here is a five-year model for one mile of 144F suburban distribution serving 200 homes passed.

The TCO ranking flips depending on assumptions. If no second cable is added in year three, direct-bury wins on total cost. If the operator expects to add a second 144F cable within five years, microduct becomes the clear winner.

Test and Acceptance Requirements by Method

Each construction method generates different test artifacts during acceptance. The customer (city, ISP, or wholesale tenant) typically requires bidirectional OTDR traces, end-to-end loss measurements, and a visual continuity confirmation before accepting the plant.

For all three methods, an inspection microscope is the single most important quality gate. Dirty connectors at the splice closure are the leading cause of acceptance failures regardless of construction method.

Hybrid Builds: When to Mix Methods

Most real FTTH builds use more than one method. The trunk between the OLT and the distribution cabinet might be microduct in HDPE conduit. The distribution legs might be aerial through wooded sections and direct-bury through subdivisions. The drops to each home might be either aerial or buried depending on the front-yard situation.

• Backbone: Microduct or HDPE innerduct for 25-year capacity reserves.
• Distribution: Aerial where poles exist, plow where they do not.
• Drops: Match the existing utility convention on the street.
• MDU risers: Indoor microduct or innerduct for tenant churn flexibility.

The transition points between methods (pole to pedestal, pedestal to MDU) are where most splice losses accumulate. Plan splice budgets generously and test each segment before tying in.

Frequently Asked Questions

Which is cheapest per mile?

Aerial at $15K to $25K per mile when poles exist with available make-ready space. Direct-bury runs $25K to $60K. Microduct sits between $35K and $80K but lowers lifetime cost by avoiding future re-trenching.

How long do aerial cables last?

Properly tensioned aerial ADSS or figure-8 cable carries a 25 to 30 year design life. Direct-buried armored cable lasts 30 to 40 years. Microduct-blown cable inside HDPE can exceed 40 years.

Can microduct be used aerially?

Yes. Aerial microduct (often 7-way or 12-way bundles) lashes to messenger or self-supports as figure-8. Common in suburban overbuilds where future expansion is expected.

What is the typical install rate?

Aerial: 4,000 to 8,000 ft/day. Plow: 3,000 to 6,000 ft/day in good soil. Microduct blow: 3,000 to 5,000 ft per shot once duct is in.

Which has fastest repair time?

Aerial is fastest because cable is visible and reachable from a bucket truck. Microduct is moderate because crews can blow new fiber through clean duct. Direct-buried is slowest due to excavation requirements.

Bottom Line

Pick aerial for fast, cheap rural and small-town builds with existing pole right-of-way. Pick direct-bury for suburban greenfield where undergrounding is mandated and capacity is fixed. Pick microduct when you expect to add fibers, lease conduit space, or operate the plant for thirty years or more. Most builds will use all three methods within the same project, and the test gear required is largely the same: a tri-wavelength OTDR, a PON power meter, an inspection microscope, and a visual fault locator.