Tag Archives: cable jacket

Cable Jacket Rating: Something You Need to Know

As the first defense line against the surrounding environment, the cable jacket prevents the core of fiber optic cable from water, flame, chemistry, etc. Meanwhile, the outermost layer keeps inert to gases and liquids that may be exposed during its service life. Besides, the cable jacket provides a smooth, low friction surface. The jacket must be made of a material that can keep the cable flexibility and maintainability at all temperatures during its service life. Today our topic is the cable jacket rating of fiber optic cable.

What Is Cable Jacket?

The optical fiber cable is composed of the inner core, cladding, coating, strength member and the outer cable jacket. The core made of plastic or glass is a physical medium used for optical signal transmission. Because bare fibers are easily broken, outer cable jacket is required to protect optical fibers. Just like mentioned above, the cable jacket is the first line of moisture, mechanical, flame and chemical protection for cables. If there is no jacket, fiber optic cable is likely to be damaged during and after installation. Common jacket materials are PE (Polyethylene), PVC (Polyvinyl Chloride) and LSZH (Low Smoke Zero Halogen).

cable jacket: fiber cable structure

Fiber Cable Structure

Cable Jacket Rating of Fiber Optic Cable

In general, the NEC (National Electrical Code) provides eight grades of fire resistance for non-conductive and conductive cables. All indoor cables must be marked and installed for the intended purpose: plenums, risers, and general purpose areas.

  • Plenums: A plenum area is is used for air flow or air distribution system (ceiling and elevated floor) building space.
  • Risers: A riser area is a floor opening, shaft or pipe vertically passing through one or more floors.
  • General purpose areas: The general area refers to all other areas on the same floor without pressure ventilation systems or risers.

Cable jacket rating is important. If the cables do not have these ratings, they cannot be installed on walls or ceilings. Here we will introduce the most common cable jacket ratings that you will encounter.

  • CL/CM/CMG: These cable jackets are applicable to all common situations. Specifically, CL cables are used for audio and video applications, and CM/CMG for communication applications, such as Ethernet. They are all tested through the so-called “vertical tray flame test”, which means they usually won’t spread the flame more than eight feet. You can install these rated cables on walls or ceilings without worrying about risers and plenums at home.
  • CMR: The CMR rating means that the cables can be used in the risers of commercial buildings because they limit flame spread better than the cables in the CL/CM series. In addition to plenums, they can be installed anywhere.
  • CMP: “P” clearly represents the plenum, so in addition to the places where CM and CMR cables can operate, this communication cable can also be used for plenums. The jacket is made of the material that retards the spread of flame. It does not emit a large amount of smoke or poisonous gas when it burns.

Conclusion

These are the common ratings of fiber optic cable jacket. We should follow these cable jacket ratings in the NEC guidelines to minimize the risk of impact, fire and toxic smoke in each area, thus preventing fire. Besides, fiber optic cable plays an important role in the field of communication. You can visit www.fs.com to find fiber cables that can meet your needs, such as single mode fiber optic cable, multimode fiber optic cable, and fiber patch cord. I hope you can get your own cable.

Cable Jacket: Should I Choose LSZH or PVC?

When talking about communication cables, we commonly use terms like LSZH and PVC to describe them. These two terms describe the chemical compounds used in production of the cables. As we might be rather familiar with these widely used terms, do you exactly know what they really mean? Or more importantly, which one is better for your project? In this article, we are going to explain these frequently asked questions, by analyzing and comparing LSZH and PVC cables.

Communications-Cable

What LSZH and PVC Stand for?

LSZH—Short for low smoke zero halogen, LSZH is a kind of cable built with a jacket material free from halogenic materials (such as chlorine and fluorine), since the toxic nature of these chemicals when burned. The term “low-smoke, zero-halogen” describes two distinct properties of a cable compound. The term “low- smoke” describes the amount of smoke which a compound emits when burned, while “zero-halogen” describes the amount of halogens used to make the compound. Terms like LSOH, LSHF and LSNH are all proper references for cables possessing low-smoke and zero-halogen properties.

PVC—Polyvinyl chloride (vinyl), a general-purpose plastic jacket material used for cables. Features low in cost and flexible, PVC cable is widely used in applications such as computers, communications and low voltage wiring. In the world of cabling, “PVC” is often used to denote a cable that is not suitable for use in a plenum airspace. PVC can potentially be dangerous in a fire situation, releasing heavy smoke and hydrogen chloride gas, which poses a great threat to human health electronic devices. PVC cables often have a CM, CMG, or CMR rating as defined by the National Electrical Code (NEC).

Differences Between LSZH and PVC Cable

Judging from the physical appearance, the difference between LSZH and PVC cable is very distinct. A PVC cable feels soft and it is smooth, whereas an LSZH cable feels rough since they contain the flame retardant compound and it is stiffer. LSZH cables are more aesthetically appealing than PVC cables. In addition to this, LSZH cable differs from PVC one in at least three aspects:

Cost: LSZH cables are slightly higher in cost than some PVC cables, but they are much safer when it comes to human health and sensitive and expensive electronic equipment. And this should be considered when comparing the cost.

Flexibility: Comparing with PVC compounds, there is a limited range of compound flexibility available for LSZH compounds, so LSZH cable is not recommended for robotic or continuous flex applications.

Heat: When a PVC cable is set on fire, it emits chemical fumes, acids and other toxic gases, which are both corrosive and harmful to human beings and environments. As for LSZH cable that has a flame-resistant jacket, it doesn’t emit these chemical substances even if it burns or exposed to high sources of heat. And it can reduce the amount and density of the smoke.

LSZH-PVC-differences

When Do I Use LSZH or PVC?

It is feasible that LSZH and PVC have equally effective performance in modern buildings. So the decision on which one to choose actually depends on the situation, that is to say, where you are going to run the cable.

PVC cable has been used in built environment for power and control applications for decades. It is commonly used for horizontal runs from the wiring center, or for vertical runs between the floors—but only if the building features a contained ventilation system running through the duct work.

LSZH cable would be more appropriate for places where fire presents a hazard to occupants. We known that the primary danger in the event of a fire is not the fire itself but the smoke and gas produced. Therefore, it is vital that the materials and products that are installed contribute as little smoke and gas as possible when burnt. LSZH cable can be employed in the following situations:

  • Confined spaces with large amounts of cables in close proximity to humans or sensitive electronic equipment, such as submarines and ships.
  • Mass transit, central office facilities and telecommunication applications.

LSZH-cable-application

Conclusion

Even though PVC cable still reigns supreme in wire and cable industry, the use of which has decreased over the past years. On the other hand, LSZH cable technology has advanced significantly, it is well suited to some applications mentioned in this article. Your cabling choice always relays on your specific condition, while to consult with wire and cable experts can also be beneficial.