The Steps Involved in Aerial Cable Construction

What is the order of operations on an aerial build?

Aerial construction is less forgiving of sequence errors than underground work, because every step depends on someone else's approval. A bore can often be redesigned in the field. An attachment cannot be moved up a pole because the crew would prefer it there.

The sequence below is the one that holds on most builds. Where projects go wrong is usually a step performed out of order: cable placed before make-ready cleared, splicing before slack was set, or closeout attempted after the crew demobilized and the field record was never captured.

• Route design, pole line verification and permitting.
• Pole survey and data collection for loading analysis.
• Make-ready engineering and construction, ending in a permit to attach.
• Messenger strand placement, guying, tensioning and bonding.
• Cable placement and the lashing pass.
• Slack storage, splice enclosure placement and risers.
• Fusion splicing and OTDR verification.
• Restoration, cleanup and closeout documentation.

Where are the hold points between steps?

A hold point is a check that has to pass before the next step starts. Aerial builds need them because each step buries the evidence of the one before it. Once cable is lashed, nobody re-checks the strand sag. Once an enclosure is sealed, nobody looks at the slack coil inside the tray again unless a test fails.

The useful hold points are few and specific. Each one has a named check, a person who confirms it, and a record that proves it happened. A hold point with no record is a hope, and it will be the first thing questioned when a pole owner inspection or an acceptance test goes wrong.

Owners benefit from asking for these checks in writing before award. They cost the contractor very little to perform during the build. Reconstructing them afterward is close to impossible, because the condition they verify is hidden by the next step.

Step one: route design and permitting

Design starts with a route that is buildable, not just drawable. That means confirming the pole line actually exists as mapped, that spans are within reasonable length for the strand class, and that the route can cross roads, water and railroads at locations where permits are achievable.

Permits stack. Pole attachment applications go to the pole owner. Work in the state right of way needs an FDOT utility permit, and county or municipal rights of way have their own processes. Maintenance of traffic requirements come with those permits and drive crew size and equipment on the day of work.

Design also sets the splice plan: where fiber counts break out, where enclosures land, and where slack has to exist. Deciding that at design time rather than in the field is what keeps splice locations at accessible poles instead of over a canal or in the middle of an intersection.

Step two: survey, make-ready and the permit to attach

The pole survey collects attachment heights, span lengths, guying, midspan clearances and existing violations. Those inputs feed a loading analysis that determines whether each pole can carry the new attachment, and what has to change if it cannot.

Make-ready construction follows: rearranging attachments in the communications space, adding guys and anchors, correcting violations, and replacing poles where the analysis requires it. Existing attachers transfer their facilities on pole replacements, which is normally the longest lead item on the entire project.

Nothing gets attached before the permit issues. The practical discipline is to track status pole by pole and mobilize only into segments where every pole in the segment is cleared, so that a crew never builds into a pole that still has a transfer pending.

Step three: strand placement and tensioning

Strand is pulled span to span, dead ended at terminal poles, and supported at intermediate poles with the specified hardware. Corners and ends of runs get guys and anchors sized for the unbalanced pull, and anchor installation is ground disturbing work, so a Sunshine 811 locate ticket and verified marks come first. Potholing at anchor locations near known services is normal practice rather than an extra.

Tension is then set to the sag target from the sag chart for that strand class, span length and the temperature at the time of stringing. A dynamometer confirms tension during the pull and a midspan measurement confirms the resulting sag and clearance.

Bonding is completed as the strand goes up. Bond connections at poles and to ground rods at the specified intervals are inspection items, and they are far easier to install during the strand pass than to retrofit after cable is lashed.

Step four: cable placement and the lashing pass

Cable is placed by one of two methods. In a block pull, blocks are hung on the strand and the cable is pulled through them from a reel. In a back pull, the cable is paid off at a mid point, figure eighted on the ground to remove twist, and pulled in both directions. Both methods exist to keep the cable inside its rated pulling tension and minimum bend radius.

A pulling swivel between the pulling line and the cable grip prevents rotation from transferring into the cable. Twist in a fiber cable is not always visible and can show up later as added loss, which is why the swivel and the reel brake settings are worth the minute they take.

The lasher then runs the span, wrapping lashing wire in a helix around strand and cable and terminating in a lash clamp at each pole. Cable is inspected for jacket damage before and after the pass, and the lashing wire material is chosen for the setting, which near the coast usually means stainless.

Step five: slack, enclosures and risers

Slack is placed at splice locations, at major crossings, and at transitions to underground, on snowshoes that hold each loop above the fiber minimum bend radius. The sequencing point is that slack goes up before the splicer arrives. A splicer who finds no slack at a planned enclosure either waits or improvises, and improvised slack is where bend loss gets built in.

Splice enclosures are mounted on the strand near the stored slack so a technician can lower the enclosure to a bucket without cutting into adjacent spans. Enclosure position, mounting orientation and drip loops matter in a climate with daily summer rain, since water tracking down a cable into an enclosure is a slow failure mode nobody catches until it causes trouble.

Risers carry the cable down a pole into conduit at transition points. The riser needs mechanical protection, a bend radius that the cable can tolerate at the top and bottom, and stored slack so that the underground portion can be reworked without disturbing the aerial run.

Step six: splicing and OTDR verification

Fusion splicing joins fibers by aligning and arc welding them. A clean splice on matched single mode fiber typically produces very low loss, and the owner's specification sets the per splice acceptance limit, measured bidirectionally. Bidirectional testing matters because a mismatch in fiber backscatter can make the same splice read low from one end and high from the other, producing gainers and false failures.

The full test set on a completed span is normally an OTDR trace from each end at both wavelengths plus an end to end loss measurement with a light source and power meter. The OTDR locates and characterizes events. The power meter verifies the total loss against the link budget. They answer different questions and neither replaces the other.

Splice quality is mostly a preparation problem. Clean strip, clean cleave, clean fusion splicer, and correct sleeve placement produce consistent results. When loss is high on repeated attempts, the cause is usually cleave angle, a dirty V groove or contaminated fiber rather than the splice program.

Step seven: restoration, cleanup and closeout

Aerial work leaves less ground disturbance than underground work, but it is not zero. Anchor installations, pole holes, riser bores and truck access across grass all require restoration to the standard the permit specifies. Sod, grade and pavement patches get restored to match, and the site gets left clean of wire cuttings, reel debris and hardware packaging.

Closeout is the deliverable most owners actually keep. It should include the as built route with pole identifiers and attachment heights, strand class and hardware, sag or tension verification, slack locations and quantities, splice locations and fiber assignments, OTDR and loss test results, photo documentation, permits and attachment approvals, and the daily production reports from the build.

The reason to build the closeout package during construction rather than after is simple. The information exists on the day the work happens. Reconstructing it weeks later means a return trip and a document that is a reasonable guess rather than a record.

Strilla Communications Company performs aerial cable construction with owned equipment and crews, a single point of contact for daily communication, and closeout documentation delivered as part of the work rather than as an afterthought.