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The importance of fiber optic cable outer sheath material and fire rating

2022-08-12
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Data center cables are intricate, converged, scattered, and extend to every part of the data center. Therefore, the importance of flame-retardant and fire-resistant fiber optic cables to data centers is self-evident. Because of improper selection, it is possible to cause the fire to spread when the fire occurs, burn down the entire data center, and cause irreparable huge losses.

 

Why is the outer sheath of optical fiber cable important? What are the materials?

Optical fiber cables are generally composed of optical fiber cores, cladding, coatings, reinforcing elements, and outer sheaths. The outer sheaths are used as the protective layer of the cables, which have the functions of fire prevention and moisture resistance. When a fire occurs in the data center, the outer sheath is used. Performance has a major impact.

 

Fiber Optic Cables for Data Centers

The outer sheath of the optical fiber cable is divided into different material types. The outer sheath of each material has its inherent characteristics (different fire performance) and suitable scenarios. Common outer sheath materials are PE, PVC, PVDF. , LSZH, Plenum, Riser, etc.

fiber optic cable

Most of the outer sheath materials have good flame retardant properties. Is the outer sheath material the only criterion for measuring the fire resistance of optical fiber cables? No, the flame retardant materials used in cables must also pass the test to reach a certain level. fire rating. For example, in order to achieve the best fire performance of a cable with a PVC outer sheath, 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, flame retardant grade (pressurized grade) in NEC standard, the highest grade. Assuming that a fan is used to force the flame to a bundle of flame-retardant grade (pressurized grade) optical fiber cables, the flame on the optical fiber cable will be extinguished within 5m, and non-toxic and non-corrosive gases will be generated.

 

OFNR/OFCR, the vertical level (trunk level) in the NEC standard, ranks second in level. A fan is also used to force the flame to the bundles of trunk-grade fiber optic cables. Although the flame will be extinguished when it spreads to within 5m, it has no smoke or toxicity specifications.

 

OFNG/OFCG and OFN/OFC are commercial grade and general-purpose grade, respectively. Optical fiber cables under these two standards are often used in environments with low requirements for fire and flame retardant.

 

What fire rating can fiber optic cables with different outer sheath materials achieve?

Although the fire rating of the optical fiber cable is not necessarily related to the material of the outer sheath, in general, if the optical fiber cable with Plenum as the outer sheath is tested for the NEC flame rating, its fire rating can theoretically reach OFNP; The optical fiber cable with Riser as the outer sheath is tested for NEC flame retardant rating, and its fire rating can theoretically reach OFNR; if the optical fiber cable with LSZH as the outer sheath is tested for NEC flame rating, its fire rating can theoretically reach OFN.

 

How to choose fiber optic cables with different outer sheath materials?

In order to prevent and reduce the probability of fire in cabling scenarios such as data centers, you must know which class your data center belongs to, what it is used for, and what special requirements are there, so that you can choose different external protection according to the standard. Fiber optic cable with sleeve material.

 

Select fiber optic cables of different materials according to the layout area

Generally speaking, Plenum fiber optic cables are suitable for use in horizontal wiring areas and inflatable environments (conveying ducts, air handling systems), where air is circulated and fires are difficult to control. Therefore, the use of OFNP flame retardant fiber optic cables is The best choice; Riser/PVC fiber optic cables are suitable for use in vertical trunk wiring areas to provide connections between entrance equipment or computer rooms and communication cabinets on different floors. Yes; LSZH fiber optic cables are often used in general areas. Even in the event of a fire, the smoke released by it is non-toxic, so it can avoid injury to rescuers.

 

Choose fiber optic cables of different materials according to the grade and size of the data center

Because data centers of different sizes have different effects after a fire, the American NEC standard recommends fiber optic 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 maintenance data centers; fiber optic cables made of riser/PVC are commonly used in medium-sized data centers, redundant data centers, and LSZH fibers. Cables are often used in small data centers and general enterprise computer rooms.

 

Summarize

Of course, the outer sheath of the optical fiber cable is only part of the prevention and control of fire. To better reduce the risk and loss of fire, the planning of the early wiring scene and the layout of the fire early warning in the later stage are essential. Ensure data center security.

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