Why is the outer sheath of optical fiber cable important? What are the materials?
Optical fiber cables are generally composed of optical fiber core, cladding, coating, strengthening elements, and outer sheath. The outer sheath is used as the protective layer of the cable, which has the functions of fire prevention and moisture resistance. When a fire occurs in the data center, the outer sheath performance has a significant impact.
Data center fiber optic cable
The outer sheaths of optical fiber cables are divided into different material types. The outer sheaths of each material have their inherent characteristics (different fire performance) and are suitable for use scenarios. The common outer sheath materials are divided into PE, PVC, and PVDF. , LSZH, Plenum, Riser, etc.
Most of the outer sheath materials have good flame retardant performance. Is the outer sheath material the only standard to measure the fire performance of optical fiber cables? No, the flame retardant materials used in the cables must pass the test and meet certain requirements. fire rating. For example, for a cable with a PVC outer sheath, in order to achieve the best fire performance, it is also necessary to consider the fire rating of the cable as a whole.
What are the fire ratings of fiber optic cables?
In NEC (National Electrical Code), the fire rating of optical fiber cables is often divided into OFNP/OFCP, OFNR/OFCR, OFNG/OFCG, OFN/OFC.
OFNP/OFCP, NEC standard flame retardant grade (supercharged grade), the highest grade. Assuming that a fan is used to forcibly blow the flame to a bundle of flame-retardant (supercharged) optical fiber cables, the flame on the optical fiber cable will extinguish itself within 5m, and non-toxic and non-corrosive gas will be generated.
OFNR/OFCR, the vertical level (trunk level) in the NEC standard, ranks second. A fan is also used to forcibly blow the flame to the bundled trunk-level optical fiber cables. Although the flame will extinguish itself within 5m, it has no smoke or toxicity regulations.
OFNG/OFCG and OFN/OFC are commercial grade and general grade respectively. Optical fiber cables under these two standards are often used in environments that do not have high requirements for fire resistance.
What kind of fire rating can optical fiber cables with different outer sheath materials achieve?
Although there is no necessary relationship between the fire rating of optical fiber cables and the material of the outer sheath, in general, if the fiber optic cable with Plenum as the outer sheath is tested for NEC flame retardant rating, its fire rating can theoretically reach OFNP; if PVC or If the fiber optic cable with Riser as the outer sheath is tested for NEC flame retardant rating, its fire rating theory can reach OFNR; if the fiber optic cable with LSZH as the outer sheath is tested for NEC flame retardant rating, its fire rating theory can reach OFN.
How to choose optical fiber cables with different outer sheath materials?
In order to prevent and reduce the probability of fire in wiring scenarios such as data centers, you must know which level your data center belongs to, what it is used for, and what special requirements it has, so that you can choose different external protection according to the standards. fiber optic cables.
Choose fiber optic cables of different materials according to the layout area
Generally speaking, fiber optic cables made of Plenum are suitable for use in horizontal wiring areas and inflated environments (conveying pipes, air handling systems), where the air is circulated and fires are difficult to control. The best choice; fiber optic cables made of Riser/PVC are suitable for use in the vertical backbone wiring area, providing connections between entrance equipment or computer rooms and communication cabinets on different floors, the possibility of large-scale fires is small, and the flame retardant level reaches OFNR Yes; LSZH fiber optic cables are often used in general areas. Even if a fire occurs, the smoke released by it is non-toxic, so it can avoid causing harm to rescuers.
Choose fiber optic cables of different materials according to the level and size of the data center
Because data centers of different sizes have different impacts after a fire occurs, the US NEC standard recommends optical fiber cables suitable for different environments. Generally, fiber optic cables made of Plenum are suitable for use in large/ultra-large data centers, fault-tolerant/parallel maintainable data centers; fiber optic cables made of Riser/PVC are commonly used in medium-sized data centers and redundant data centers, and optical fibers made of LSZH Cables are often used in small data centers and general enterprise computer rooms.
