How to pick a GYTZS fiber optic cable without overcomplicating it

How to pick a GYTZS fiber optic cable without overcomplicating it

You’ve got a GYTZS cable spec in front of you, and you are not quite sure if it is the right outdoor armor cable for the job. The short answer: if fire safety regulations or confined spaces with people occupy the deployment site, GYTZS makes sense. If none of those apply, a cheaper gyts will do the same job for less money.

Let us break down what the model name actually means, how the cable differs from similar types, and when you should pick it over the alternatives.

What the letters GYTZS actually stand for

The naming follows a Chinese industry convention that tells you what is inside the cable. Each letter means something specific:

·         GY – Outdoor communication cable (Ye wai guang lan).

·         T – Filled construction with water-blocking compound in the loose tubes.

·         Z – Flame-retardant sheath, specifically LSZH (Low Smoke Zero Halogen). This is the key differentiator from GYTS.

·         S – Steel-PE bonded sheath (corrugated steel tape armor).

So GYTZS is basically a GYTS cable with one major upgrade: the outer jacket is swapped from standard polyethylene to LSZH flame-retardant material.

If you take the same cable with a regular PE jacket, it becomes GYTS. Same steel tape armor, same loose tube construction, same water blocking—just a different outer layer.

How the structure works

GYTZS uses a stranded loose tube design. 250µm optical fibers sit inside high-modulus plastic loose tubes. Each tube gets filled with a waterproof compound. The tubes then get stranded around a central steel strength member. A corrugated steel tape wraps around the core for crush resistance and rodent protection. Finally, the LSZH jacket goes on top.

This setup gives you three things at once: mechanical protection from the steel tape, water resistance from the tube compound and core filler, and fire safety from the LSZH jacket.

The cable handles typical pulling loads of around 1500N short-term and 600N long-term. Crush resistance sits at about 1000N per 100mm. Bending radius is 10 times the cable diameter when static, 20 times when under tension.

The one big tradeoff: LSZH vs PE

GYTZS exists because polyethylene cannot go everywhere.

Standard outdoor cables use a black PE jacket. PE resists UV radiation, handles moisture well, and costs very little. But when PE burns, it releases thick black smoke and corrosive gases. That is a problem in tunnels, mine shafts, underground vaults, and anywhere people need to evacuate through smoke.

LSZH compounds solve that. They burn with minimal smoke. No halogen gases come out. No corrosive hydrochloric acid forms.

The catch is that LSZH is not as tough outdoors as PE. Regular PE jackets last decades under direct sunlight. LSZH formulations have improved, but many still degrade faster under UV exposure. Some manufacturers blend UV stabilizers into the LSZH compound, but you need to verify this with the supplier. For permanent outdoor aerial installation without conduit, a PE jacket is still the safer long-term bet.

This is why some engineers route GYTZS inside ducts even when the cable is rated for direct burial. The LSZH jacket handles the fire safety requirement, and the duct protects it from UV and physical abrasion.

GYTZS vs the rest

If you are comparing outdoor armored cables, the main alternatives you will run into are GYTS, GYTA, and GYTA53.

A few things stand out from this table.

GYTA uses aluminum tape instead of steel. That makes it lighter and easier to handle, but it offers less crush and rodent protection. If you are burying cable, stay away from GYTA. If you are running it through ducts with existing cables, the lighter weight helps.

GYTA53 throws everything at the problem. Double armor, double jacket. It is heavy, expensive, and overkill for most aerial or duct jobs. But for rocky direct burial where backhoes might dig nearby, you want the extra armor.

GYTS is your baseline. It does the job for most outdoor deployments at the lowest price.

GYTZS is GYTS with a safer jacket. Nothing else changes.

When to actually pick GYTZS

Here is the decision flow.

Pick GYTS if: You are deploying outdoors, no fire regulations require LSZH, and cost is a factor. That covers most aerial and duct installations in open areas. The PE jacket lasts longer in sunlight.

Pick GYTZS if: Any of these conditions are true:

·         The cable passes through a tunnel, mine, or underground vault.

·         Local building codes or safety regulations mandate flame-retardant cables.

·         The installation sits in a confined space where smoke inhalation risks are high.

·         The cable enters a building from outdoors and indoor fire ratings apply.

Pick GYTA if: You need moisture protection but minimal mechanical strength. Lightweight duct applications. Not for burial.

Pick GYTA53 if: The cable goes directly into rocky ground or areas with heavy rodent activity. Be prepared for higher material cost and harder pulling.

What the standards say

GYTZS cables typically comply with YD/T 901 or YD/T 1114. Some also carry MT386-1995 certification for coal mine use, though that standard has a more specialized application.

The LSZH jacket should pass flame tests under IEC 60332-1-2 or IEC 60332-3-24, smoke emission tests under IEC 61034, and halogen gas tests under IEC 60754-2. Ask the supplier for test reports if compliance matters for your project.

A practical note on installation

LSZH compounds do not slide through ducts as easily as PE. They have higher friction. If you are pulling long runs through conduit, factor that into your tension calculations. Use pulling lubricant.

For aerial installation between poles, GYTZS works fine, but check the UV rating on the specific jacket material. Some manufacturers produce LSZH formulations with added UV stabilizers. Others do not. Get it in writing.

The bending radius rule stays the same as any armored loose tube cable: no sharper than 20 times the cable diameter while pulling, 10 times after it is in place.

Bottom line

GYTZS is not a different cable from GYTS. It is the same cable with a different jacket material. The steel tape armor and water-blocking are identical.

Use GYTZS when fire safety rules force you to. Use GYTS when they do not.

Most of the time, you will end up with GYTS. But when the deployment site has people in confined spaces and smoke is a real hazard, the extra cost of LSZH pays for itself in safety.