The armor layer is the part of an outdoor fiber optic cable that decides whether your link survives five years of rocky soil, hungry rodents, salt fog, or a careless backhoe. Pick the wrong armor and you either overpay for steel you didn't need, or you save a few cents per meter and splice the cable back together every wet season.
This guide cuts through the material list and code tables and answers the question buyers actually ask: which armor material, and which model code, fits my route? We walk through metal vs. non-metal armor, read the digit codes inside names like GYTA23 or GYFTY63, and map each armor type to direct burial, aerial, rodent-prone, and corrosion-heavy environments.
What the Armor Layer Actually Does
Inside an outdoor fiber cable, the armor layer sits between the inner sheath (or core wrap) and the outer jacket. Its job is narrower than people assume - it is not a general "protection" layer, it is a crush, bite, and lateral-impact barrier. Tensile load is handled by the strength member (FRP rod or steel wire in the core), and moisture is handled by water-blocking tape and jacket materials. The armor is specifically there to stop rodents, rocks, and mechanical crush.
Because of that narrow role, armor selection is almost entirely driven by installation environment - not by fiber count, not by bandwidth. The relevant international reference is the IEC 60794 family of optical cable standards, with regional supplements such as China's YD/T 908 (which is where the numeric armor codes in this article come from). A more detailed walkthrough of the full fiber optic cable structure from core to sheath is available separately.
Metal vs. Non-Metal Armor: Which One Fits Your Site?
Almost every armored outdoor cable falls into one of two families. The choice is rarely about "strength" in the abstract - it's about whether the route tolerates metal at all.
Metal armor (steel tape, stainless steel tape, round steel wire)
Choose metal armor when the cable will be buried, pulled through rocky duct, or run through areas with documented rodent pressure. Corrugated steel tape is the standard and the cheapest option that passes most direct-burial specifications. Stainless steel tape costs more but keeps performing in salty air, chemical plants, and coastal soil where ordinary galvanized steel pits and perforates within a few years. Round steel wire (single or double layer) is reserved for deep-sea, river-crossing, or extreme-pull applications.
Avoid metal armor where you need to run parallel to high-voltage lines (induced current is a real hazard on long spans), near radar or EMI-sensitive equipment, or where lightning exposure is high and the route has no reliable earthing scheme - that is the exact problem all-dielectric self-supporting (ADSS) cables were designed to solve.
Non-metal armor (glass yarn, FRP rod, aramid yarn)
Non-metal armor is lighter, fully dielectric, and surprisingly effective against rodents when paired with a hard FRP or glass-yarn layer that resists tooth penetration. It is the right choice for aerial spans near power lines, for data center and building risers, for substations, and anywhere the installer wants to skip grounding hardware entirely. The trade-off is lower crush resistance than corrugated steel, so non-metal armored cables are generally not specified for direct burial in rocky soil. FRP as a reinforcement and armor material has its own performance envelope worth understanding before specifying it.
Armor Material Quick Comparison
| Armor material | Crush resistance | Rodent resistance | Corrosion resistance | EMI/lightning safe | Typical use |
|---|---|---|---|---|---|
| Corrugated steel tape | High | Good | Moderate (galvanized) | No | Direct burial, duct |
| Stainless steel tape | High | Very good | Excellent | No | Coastal, chemical, heavy rodent |
| Round steel wire (single/double) | Very high | Very good | Moderate | No | Submarine, river, deep trench |
| Glass fiber yarn | Moderate | Good | Excellent | Yes | Aerial, indoor, substations |
| FRP rod / non-metal rod | Moderate–high | Very good | Excellent | Yes | Rodent-prone aerial, all-dielectric direct burial |
How to Read the Armor Code in a Cable Model Number
In the Chinese-origin naming system (YD/T 908), which is widely mirrored across Asia-Pacific and in many export specifications, an optical cable model ends with one or two digits describing the armor and outer sheath. The second-to-last digit is the armor; the last digit is the outer sheath. A quick reference:
- 0 or no symbol - no armor. Example: GYTA (aluminum-tape-bonded, no armor), GYTS04 (steel tape laminated moisture barrier, no separate armor, PE jacket).
- 1 - steel tube armor. Example: GYTA13.
- 2 - lapped (corrugated) steel tape. Example: GYTA23, the workhorse for general outdoor routes.
- 3 - single-layer round steel wire. Example: GYTA33.
- 33 - double-layer round steel wire (submarine and river crossing). Example: GYTA333.
- 4 - stainless steel tape. Example: GYTA43 - the go-to for heavy rodent and mildly corrosive environments.
- 5 - chromium-plated steel tape. Example: GYTA53.
- 6 - non-metal wire armor. Example: GYFTY63.
- 7 - non-metal tape armor. Example: GYFTY73.
- 8 - non-metal (FRP) rod armor. Example: GYFTY83.
- 88 - double-layer non-metal rod. Example: GYFTY883.
A practical shortcut: if the model starts with GYFTY, the cable is fully non-metallic and whatever follows will be a non-metal armor code (6, 7, 8, or 88). If it starts with GYTA or GYTS, the cable has metallic elements and the armor digit will be 1–5. The outer sheath digit that follows is typically 3 (PE) or 53 (PE + steel-tape flooded jacket). For a deeper look at the GYFTA53 structure and why it is favored for direct burial, the linked technical note covers the double-jacket construction in detail.
Choosing Armor by Scenario
Best armor for direct burial fiber optic cable
For direct burial, the cable has to survive backfill compaction, stone point loads, ground movement, and - in most rural and long-haul routes - rodent activity. The default answer is a double-jacket, corrugated steel tape armored construction such as GYTA53 or GYFTA53 (the latter when you need a fully dielectric build). Routes in dry, rocky soil sometimes step up to round-wire armor. Product selection for this category lives under our direct-bury fiber optic cable line.
What armor should aerial fiber cable use?
Aerial spans don't need crush protection - nothing is pressing on the cable - so heavy metal armor is usually overkill and adds weight that forces shorter spans and heavier hardware. Most aerial routes go with non-metal armor (glass yarn or FRP rod) or no armor at all, with the strength handled by the self-supporting structure (figure-8 messenger or ADSS). The exceptions are aerial runs in dense rodent habitat and aerial-to-underground transitions, which may justify a light steel-tape armored aerial cable. A breakdown of configurations is available in the aerial fiber optic cable category.
Rodent-resistant armor: metal or non-metal?
Both work, and the better question is which rodent. Against rats and mice, corrugated steel tape or stainless steel tape is highly effective because the tooth cannot easily perforate the corrugation. Against larger rodents and persistent gnawing (porcupines, some squirrel species), stainless steel tape outperforms galvanized steel because the surface stays smooth and doesn't corrode into weak points. Non-metal FRP rod armor also performs well in lab bite tests and is used extensively in regions that prefer dielectric cables, but it generally requires a thicker construction to match steel on bite resistance. Dedicated anti-rodent fiber optic cable designs combine both approaches. Limits apply - no armor is "rodent-proof," only rodent-resistant, and jacket material, armor coverage overlap, and installation depth all affect real-world outcomes.
Corrosion-proof armor for coastal and chemical sites
Salt fog, acidic soil, and industrial chemical environments shorten the life of galvanized steel armor significantly. Two options work: stainless steel tape (code 4) for routes that still need metal crush protection, or fully non-metal construction (GYFTY-series) for sites where metal is either unwelcome or unnecessary. Chromium-plated steel tape (code 5) sits between the two on both cost and corrosion performance.
Scenario-to-Model Quick Selection
| Installation scenario | Recommended armor | Typical model example |
|---|---|---|
| General direct burial, moderate rodent risk | Corrugated steel tape, double jacket | GYTA53, GYTS53 |
| Direct burial, heavy rodent or coastal soil | Stainless steel tape, double jacket | GYTA43, GYTS43 |
| Direct burial, fully dielectric required | Non-metal rod + double jacket | GYFTY83, GYFTA53 (non-metal variant) |
| Aerial, standard ADSS or figure-8 | None or light non-metal | GYFTY, GYXTC8S |
| Aerial through rodent habitat | Light steel tape | GYXTW, GYTC8S23 |
| Duct installation, urban | Corrugated steel tape, single jacket | GYTA23 |
| Submarine / river crossing | Double-layer round steel wire | GYTA333 |
| Substations, EMI-sensitive sites | Non-metal (glass yarn or FRP) | GYFTY, GYFTY63 |
Common Mistakes to Avoid
- Specifying heavy armor for aerial runs. It adds weight, shortens permissible span length, and forces heavier suspension hardware without adding meaningful protection.
- Using galvanized steel tape in salt-fog environments. Within 3–5 years the armor pits, water ingress follows, and attenuation starts climbing. Specify stainless steel or go dielectric.
- Assuming "armored" means "rodent-proof." It doesn't. Armor coverage, overlap, jacket hardness, and installation depth all matter. If a route has known high rodent activity, specify a cable tested to a recognized rodent-resistance standard and consider burial depth and conduit.
- Ignoring lightning and induced-current risk on long metallic runs parallel to power lines. If grounding is uncertain, default to dielectric.
FAQ
Does aerial fiber cable need armor?
In most routes, no - or only a light non-metal armor. Aerial cables are not subject to crush, so the main reason to add armor is rodent or bird damage on specific spans. A plain ADSS or figure-8 cable is enough for the majority of installations.
What's the difference between steel tape and stainless steel tape armor?
Mechanical performance is similar. The real difference is corrosion behavior: galvanized steel tape is cheaper and fine for most inland, non-corrosive soils; stainless steel tape costs more but holds up in coastal, chemical, and persistently wet environments, and it also performs better against aggressive rodents over time.
What does the "23" in GYTA23 actually mean?
The "2" is the armor code (lapped/corrugated steel tape), and the "3" is the outer sheath code (polyethylene). So GYTA23 is a loose-tube, aluminum-tape-bonded cable with corrugated steel tape armor and a PE outer jacket - one of the most common direct-burial and duct cables in service.
Can I use a non-metal armored cable for direct burial?
Yes, in many cases - GYFTA53 (with non-metal strength members) and GYFTY83 are built for it. They trade a small amount of crush resistance for full dielectric behavior, which is preferred near high-voltage infrastructure or in lightning-prone areas with uncertain grounding.
Where can I find the official definitions of these armor codes?
The numeric code system comes from YD/T 908 (China's industry standard for optical cable type designation), which is broadly aligned with the IEC 60794 series on optical fibre cables. For materials and dimension terminology, the ITU-T recommendations on optical fibre cables are the international reference.
Working With a Cable Manufacturer on Armor Selection
Armor choice looks like a catalog decision, but on real projects it usually comes down to three inputs the manufacturer needs from you: (1) the installation method and environment - buried, ducted, aerial, submarine, coastal, substation; (2) the rodent and wildlife profile of the route; and (3) whether the route runs parallel to power infrastructure or through EMI-sensitive zones. With those three answers, a qualified supplier can narrow the model to two or three options and quote against recognized standards.
Hengtong manufactures the full range of armored outdoor cables covered above - corrugated steel, stainless steel, round wire, FRP rod, and glass-yarn constructions - and supplies them against IEC 60794 and YD/T 908 specifications. Where a project has an unusual combination of constraints (for example, dielectric + heavy rodent + long aerial spans), custom-engineered cable structures are available with project-specific performance reports.