Skip to content 
The material of the outer sheath of MPO/MTP cable directly determines its fire rating, wear resistance, and applicable environment. The selection is mainly based on the fire safety regulations and installation location of the data center or cabling system. There are currently four commonly used materials in the market: LSZH, OFNR, OFNP, and armored. Below, Yingda will help expose their characteristics and differences one by one.
Definition and Differences
The main differences in the materials and structures of these four types of fiber optic cable sheaths are their flame retardant rating, application scenarios, safety, and physical defense capabilities.
In data centers and building cabling, according to fire safety regulations (such as NEC standards in the United States) and installation environments (such as pipelines, outdoor areas, and risks of rodent bites), different outer jacket must be strictly selected.
Type 1: LSZH (Low Smoke Zero Halogen)
- Principle: The material does not contain halogens. During a fire, it can maintain extremely high visibility and will not produce highly toxic inhalants, ensuring the safety of personnel evacuation.
- Features: The smoke generated during combustion is minimal and does not release toxic halogen gases (such as chlorine, fluorine, etc.).
- Main application: European data centers and China mainstream data centers. Europe (especially EU countries) has extremely high requirements for environmental protection and personal safety, and has mandated the implementation of LSZH.
Type 2: OFNR (Optical Fiber Non conductive Riser)
- Principle: Typically utilizes flame-retardant PVC material. Though it is capable of self-extinguishing, it releases dense smoke and toxic gases when burning.
- Features: It has vertical fire resistance and can prevent flames from spreading upwards along the vertical pipes (Risers) of the building.
- Main application: The vertical main shaft of the building (cross floor wiring). It is commonly used in the North American market, but it cannot be used for horizontal ventilation ducts in vertical channels.
Type 3: OFNP (Flame retardant peel off grade/Ventilation duct grade/Optical Fiber Non conductive Plenum)
- Principle: Fluoroplastic materials such as PTFE/FEP are usually used.
- Features: The highest fire protection level. Not only can it self extinguish within 20 minutes, but the smoke and toxic gas produced during combustion are also extremely low.
- Main application: North American data centers and inflatable return air environment (Plenum area). North American law mandates the use of OFNP in enclosed spaces such as suspended ceilings and elevated floors where air circulation is high and fires are highly likely to spread.
Type 4: Armored Anti rodent Cable
- Principle: There is a hard armor layer underneath its outer skin (LSZH, PE, or PVC) that mice cannot bite, effectively protecting the fragile optical fibers inside.
- Features: The highest physical defense capability. A layer of steel belt, stainless steel hose or fiberglass yarn protection layer is added inside the outer skin, which is specially used to resist the bite of rats and the extrusion of heavy objects.
- Main application: outdoor trenches, basements, old computer rooms, non enclosed warehouses, and other environments where mice often appear.
4 Type Outer Jacket Parameters and Performance Comparison
| Jacket type | LSZH | OFNR (Riser) | OFNP (Plenum) | Armored anti-rodent cable |
| Flame retardant rating | moderate | High (vertical flame retardant) | Highest (forced self extinguishing) | Depends on the material of the inner/outer sheath |
| Smoke and Toxicity | Extremely low (non-toxic) | High (toxic) | extremely low | Depending on the specific outer skin |
| Mechanical compression/rodent prevention | ordinary | ordinary | ordinary | Extremely strong (physically resistant to biting) |
| Cable flexibility | Soft and easy to bend | moderate | Slightly hard (due to special material) | Harder, with a larger bending radius |
| Price cost | moderate | lower | expensive | Higher (due to increased metal layer) |
| Standard dominant area | Europe/Chinese Mainland | North America (Vertical Building) | North America (Data Center) | Global applicability (special environment) |
Difference in fire safety: LSZH vs OFNR vs OFNP
It should be clarified that LSZH is a material selection, while OFNP and OFNR are fire safety ratings defined by UL (Underwriters Laboratories). When making a purchase, it is important to pay attention to the safety rating rather than just looking at the materials.
The ranking of fire performance levels for these three is: OFNP>OFNR>LSZH. Higher grade cables can be used for scenarios with lower grade requirements, but not vice versa.
- OFNP: Safety Ceiling. Require flame spread not to exceed 1.5 meters and extremely low smoke production.
- OFNR: Vertical safety line. Require flames to spread no more than 3.6 meters and be non-toxic.
- LSZH: Choosing safety and environmental protection. Low smoke, halogen-free, non-toxic, and low corrosiveness during combustion.
Rat Bite Prevention: Hardcore Defense of Armored Fiber Optic Cables
Armored cables defend against rodent infestations through physical means.
Structure and principle: Add a hard protective layer inside the ordinary optical cable as a physical barrier. There are mainly two types:
① Metal armor: Use stainless steel hoses, steel strips, or steel wires to directly prevent biting.
② Non metallic armor: using hard materials such as fiberglass yarn to make mice feel uncomfortable or injured when gnawing, thereby creating fear.
Additional features: In addition to rodent protection, it also provides strong compressive and tensile strength to prevent fiber optic cables from being damaged in harsh environments.
Combination Fist of Sheath Material and Armor
In practical fiber connectivity products, these features often appear in combination to meet multiple needs. For example, a fiber optic cable can have multiple characteristics such as “LSZH outer sheath”+ “armored stainless steel tube”+“OFNP fire rating” at the same time.
How to Choose the Best Suitable MPO Cable sheath?
You make following guidelines for your reference, you can refer and make a choice based on the actual installation environment:
| Application scenarios | Recommended jacket sheath type | Main considerations |
| Internal data center (connection between cabinets) | LSZH or OFNR | LSZH can ensure personnel safety in case of fire, while OFNR meets the fire protection requirements for vertical wiring |
| Computer room ventilation duct/under elevated floor | OFNP | This is a mandatory requirement because ventilation ducts are critical channels for flame spread |
| Vertical shafts between floors of office buildings | OFNR | Specially designed for vertical trunk lines, it can effectively prevent the spread of fire between floors and has high cost-effectiveness |
| Residential communities, factories, outdoor direct burial | Armored | These environments have a high risk of rodent infestation, and armor is the key to physical protection |
| Public places such as subways, hospitals, airports, etc | LSZH | The characteristics of dense personnel, low smoke and non-toxic combustion are the first choice to ensure life safety |
| Indoor general horizontal wiring | PVC (universal type)/LSZH | PVC has a lower cost and is suitable for ordinary environments; If the building code has higher requirements, LSZH should be selected |
Conclusion
When selecting optical cables, it is necessary to first clarify the fire safety regulations for the installation location (referring to the applicable scenarios of OFNP and OFNR), then decide whether to use LSZH material based on environmental safety requirements, and finally determine whether to add armor protection based on the risk of physical damage.
