In the fiber industry, we have all probably seen the words plenum or riser in our day, as these are two of the most common jacket types in the United States. In Europe we are seeing more Low Smoke Zero Halogen cables being utilized. But there are other options out there in the fiber optic world that are lesser known and talked about, they are the likes of Low Smoke Zero Halogen (LSZH), and Polyethylene (PE).
When looking at the construction of any fiber optic cable, you will notice that the jacket is the first line of defense against physical damage from chemicals, water, burning and other potentially damaging effects that would compromise the viability of the cable. Cable jackets come in multiple colors, but there are industry standard color codes such as aqua for OM3 or yellow for single mode, but in some cases there are custom colored jackets. You will also see foot markers on the outer jacket, showing you length of the cable, and even a print string showing the type of fiber, brand of cable, and type of cable construction. The print string will also contain information as to whether or not the cable is UL listed, and if it is, it will contain the UL number. Most cable jacket material is made from PVC or Polyvinyl Chloride, and there are additives that determine its jacket rating.
Plenum and riser ratings are defined by the National Electrical Code (NEC). They are also responsible for the standards that these cables must abide by in order to be classified as plenum or riser cabling. This standard basically states that if a fire were to start within a structure, how much would these compounds contribute to the fire, and create a “fuel” source - transporting the fire from place to place along the cable.
Most fiber optic cables that adhere to these fire standards are Underwriter Laboratories (UL) tested, meaning that they bear the UL marker on the cable jacket and have been certified to meet the NEC Standard for the cable jacket type. These UL Listings are independently tested, and qualified to ensure that the safety measures are upheld. They (UL) have no monetary stake in the items that they test, and consumers can be assured that this UL listing means that the safety standards are upheld. These listings are given and can be taken away at any point if the quality of the product does not continue to meet that UL standard.
The real question that most technicians ask in the field is where to use what type of jacket. Below we will go into a breakdown of the cable jacket types and where they can be utilized within a building or structure.
Plenum Cable
Plenum has the highest fire rating, meaning that it can be installed in all of the plenum spaces within a building such as the air ducts and ventilation systems - any part of the building that has to do with heating or cooling. Plenum can sometimes be utilized in any space within a building as an alternative to other jacket types. Plenum cables are less hazardous and create less smoke and toxic fumes in the case of fire. If a job requires plenum cable then plenum cable must be installed, there are no alternatives for this type of cable install. Plenum cables for the above reasons are usually slightly more expensive than the other cable jackets.
Riser Cable
Riser cabling is only to be used within riser spaces in a building - such as between building shafts, for vertical runs. It is meant to be a backbone cable, the fire ratings that fit a riser rating are not as strict as plenum. You can utilize a plenum cable within a riser space, but you cannot utilize a riser cable in a plenum space. Such as in the case of a ventilation shaft - you could not install a riser cable because this is a plenum air space, but you can install riser say in an elevator shaft between the floors of a building. Typically, riser cables are less expensive than plenum because the standards are less stringent.
Low Smoke Zero Halogen (LSZH) Cable
Low Smoke Zero Halogen cable jacketing or LSZH is a separate classification from riser or plenum cables because it does not contain the same compounds or thermoplastics that produce smoke and other hazardous chemicals that could be harmful to humans and animals that may be in the vicinity of the cable, if it ever should burn. To be considered low smoke zero halogen cable, it must be made of flame retardant materials that do not excrete halogens, and produces little to no smoke when it burns. LSZH is not the same as a plenum cable - they are two different fire ratings. While it may seem beneficial to use LSZH within every space in a building, this type of cable does not fit the bill for every single application. Since this product is far more expensive than other compounds, it does not make sense to install this in areas that do not require a less hazardous, or low smoke material. LSZH is highly recommended for areas that have poor ventilation, where people tend to congregate or in a confined space. LSZH is primarily utilized in Europe currently but, this type of cable is gaining traction within the US markets. .
PE Cable
PE (polyethylene) rated cable is primarily used for outdoor cables only; this is not a cable that can be installed more than fifty feet inside of a building. PE cable jacket's superior weather, temperature and water or moisture resistance makes this a great pick for harsh weather conditions and installations, but its rigid characteristics make it difficult to utilize in environments that require flexibility or movement of the cable. It also boasts superior UV protection because its black color absorbs the sunlight, which is a typical characteristic for outdoor rated cabling.
While there are more cable ratings and classifications than these shown above, these are the most common types that your average technician will run into on the job more. Familiarity with the cable jacket types is never a bad thing to have in a technician’s pocket. Knowing and being able to define what makes a plenum cable plenum or riser cable riser is superior knowledge that will benefit the technician on future jobs. .
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