Installing fiber optic cable correctly is the difference between a link that lasts 25 years and one that fails in the first year. This guide covers the three main installation methods, the mechanical limits you must respect, and the tests to run afterwards.
Confirm the route, the environment and the cable type. A cable rated for duct use is not automatically rated for direct burial, and an aerial cable must carry its own weight between poles.
Self-supporting figure-8 and ADSS cables are designed for pole-to-pole spans. For ADSS, the span is limited by sag and wind load — typically up to 200 m depending on the sheath and installation point on the pole.
Duct routes protect the cable from soil movement and rodent attack. Pull tension must never exceed the cable's short-term tensile rating — for a typical 12-core GYTA cable this is around 1500 N.
Direct buried cable needs armouring against crush, rodents and moisture. GYTA53 (double sheath, corrugated steel tape) and GYTS are common choices.
Every installed span must be tested before it is accepted. The standard tests are:
Every span is accepted or rejected on recorded measurements, not on a visual check. The table lists the five tests that decide acceptance and the criterion applied to each.
| Test | What it proves | Pass criterion | Scope |
|---|---|---|---|
| OTDR trace, 1310 nm and 1550 nm, both directions | Splice loss, bend loss and breaks — and the baseline every future fault-finding run is compared against | No event loss above the design splice loss; one stored trace per fibre and per wavelength | Every spliced span |
| End-to-end insertion loss | Total link loss against the optical budget calculated at design stage | Measured loss no higher than the budget: fibre attenuation x length + splice loss + connector loss | Every link before handover |
| Continuity and polarity | Every fibre is live, correctly sequenced and labelled at both ends | 100% of fibres pass light and match the port labelling | Every link before handover |
| Visual end-face inspection | Contamination, scratches and polish defects that add loss and damage mating sleeves | Core zone clean and defect-free after cleaning | Every connector mating |
| Bend and crush spot check at handholes and pull boxes | Hidden loss caused by an over-tight radius during installation — the most common cause of a link that passes on day one and fails later | Cable bend radius at or above the static limit in the bend radius table below | Every handhole and pull box |
Pull tension is limited by the strength members, not by the jacket. The short-term figure applies only while the cable is being pulled and only for a few minutes; the long-term figure is the load the cable may carry for the whole of its service life. Stay below the long-term value wherever the cable will remain under permanent tension, as on a self-supporting aerial span.
| Cable family | Typical model | Long-term allowable tension (N) | Short-term allowable tension (N) | Typical route |
|---|---|---|---|---|
| Bow-type drop cable (indoor) | GJXH | 100 | 200 | Indoor wall and desk drop, short pulls |
| Bow-type drop cable (self-supporting) | GJYXCH | 300 | 600 | Aerial FTTH drop between pole and building |
| Indoor tight-buffer breakout | GJFJH | 200 | 660 | Inside plant, riser and patch panel |
| Non-metallic central loose tube, flat | GYFXTY | 600 | 1500 | Duct, short span, no earthing required |
| Non-metallic central loose tube, round | GYFXY | 400 | 1000 | Duct |
| Non-metallic stranded loose tube | GYFTY | 800 | 1500 | Duct, aerial lash, high-EMI routes |
| Stranded ribbon | GYDTA/S | 600 | 1500 | High fibre count duct routes |
| Figure-8 aerial, central tube | GYXTC8S | 1000 | 2500 | Pole-to-pole self-supporting span |
| Figure-8 aerial, stranded loose tube | GYTC8S | 4000 | 7500 | Long self-supporting span |
| Heavy armoured, double sheath | GYTA53 | 1000 | 3000 | Direct burial |
| Armoured underwater | GYTA33 | 3000 | 5000 | River, lake and wetland crossing |
| Mini ADSS | ASU | 700 | 1700 | Short aerial span without messenger wire |
| ADSS, span-rated | ADSS | 1500 | 4000 | Aerial, span set by sag and wind load |
ADSS figures are span-rated rather than a plain tensile rating: 1.5 kN recommended daily maximum working tension, 4.0 kN maximum allowable tensile load and 10 kN breaking strength for the 12.5 mm design, with the permitted span further limited by sag and wind load. Always convert kN to N when comparing with the other rows in this table.
The multiplier is applied to the cable outer diameter, so a larger cable needs a larger absolute radius for the same figure. For flat drop cable the multiplier applies to the larger cross-section dimension.
| Cable family | Typical model | Ref. outer diameter (mm) | Static radius (installed) | Dynamic radius (during pulling) |
|---|---|---|---|---|
| Bow-type drop cable (indoor) | GJXH | 3.0 x 2.0 | 20D | 40D |
| Bow-type drop cable (self-supporting) | GJYXCH | 5.0 x 2.0 | 20D | 40D |
| Non-metallic stranded loose tube | GYFTY | 9.0 | 15D | 30D |
| Non-metallic central loose tube, flat | GYFXTY | 7.2 x 4.5 | 15D | 30D |
| Non-metallic central loose tube, round | GYFXY | 8.0 | 10D | 20D |
| Stranded ribbon | GYDTA/S | see datasheet | 10D | 20D |
| Flame retardant, steel tape | GYTZA/S | see datasheet | 10D | 20D |
| Armoured, steel tape | GYXTY | 6.6 | 15D | 30D |
| Heavy armoured, double sheath | GYTA53 | see datasheet | 15D | 30D |
| Figure-8 aerial, stranded loose tube | GYTC8S | 9.0 x 17.0 | 15D | 30D |
| Armoured underwater | GYTA33 | 15.7 | 12.5D | 25D |
| Mini ADSS | ASU | 7.0 | 15D | 30D |
Worked example. A GYTA33-12B underwater cable has a 15.7 mm outer diameter: static minimum radius = 12.5 x 15.7 = 196 mm, dynamic minimum radius = 25 x 15.7 = 393 mm. A handhole that forces the cable below 196 mm will show loss on the OTDR even when the cable looks undamaged. For the 5.0 x 2.0 mm GJYXCH drop cable the same rule gives a static radius of 20 x 5.0 = 100 mm and a dynamic radius of 40 x 5.0 = 200 mm.
Aerial, duct and direct burial each impose different mechanical demands. Choose the cable for the route, respect the tension and bend limits, and always test before acceptance. Huifiber supplies figure-8, ADSS, GYTA/GYTS and GYTA53 cables designed for these three installation methods.
For the material and strength-member choices behind outdoor drops on aerial routes, see our outdoor FTTH drop cable guide — it covers the pull tensions and bend limits that decide whether a drop survives installation.
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Aerial (strung between poles or towers with self-supporting or lashing arrangements), duct (pulled through buried or overhead conduit) and direct burial (armoured cable laid and backfilled in a trench). Each has its own cable rating, tension limit and clearance rules.
ADSS spans are limited by sag and wind load rather than by the fibre. In practice the working span is typically up to about 200 metres, depending on sheath type, installation point on the pole and local wind and ice loading.
Pull tension must never exceed the cable short-term tensile rating, around 1500 N for a typical 12-core GYTA cable. Use a tension meter and a swivel, pull at a steady speed, and respect the minimum bend radius at every duct entry and sheave.
