Active Optical Cable Jacket Explained: OFNR vs OFNP vs PVC vs LSZH?

NADDOD Abel InfiniBand Expert Feb 8, 2023

Since active optical cable is actually a combination of optical transceiver and fiber optic cables, its fiber cable parts’ fire rating level is usually taken into consideration when choosing this type of product. Like any other types of fiber optic cables, active optical cables are made up of many components and you may often see the names OFNR, OFNP, LSZH, PVC, etc. Deciding which fiber optic cable is best for your entire business can be very confusing. Although they appear to be the same thing, OFNR/OFNP and LSZH/PVC are two types of very different and very significant properties of fiber cables, and a single fiber optic cable can own both of them. Understanding fiber optic cable construction as well as the various fire rating levels connected with them is necessary to better comprehend these characteristics.

Fiber Optic Cable Structure

The fiber cable is made up of a number of components. To provide protection and shielding, especially for the conductors and the fiber core, each component, starting with the cladding, moving on to the coating, strength member, and finally the outer jacket, is covered on top of each other. Above all of these, the outer jacket is the first line of defense and fortifies the fiber to withstand a variety of environmental factors during installations and operations, including fire, moisture, chemical, and stress.

Types of Material for Fiber Cable Outer Jackets

In terms of various materials, fiber cable outer jackets can be divided into several types. Depending on the application, these materials can be used in a variety of ways and have various properties. The most common types of outer jacket materials are listed below, along with examples of how they are used.

Material Characteristics and Applications
PVC (Polyvinylchloride) It is the most typical material for an outer jacket. It is inexpensive, sturdy, adaptable, fire resistant, and has many uses.
PE (Polyethylene) While maintaining a high insulation, it has excellent electrical properties. PE cables are more flexible despite being solid and firm.
PVDF (Polyvinyl Difluoride) It is mostly utilized in plenum areas and is more flame-resistant than PE cable.
PUR (Polyurethane) It can withstand scratches and is typically used in low-temperature environments, and is very flexible.
LSZH (Low Smoke Zero Halogen) LSZH is less toxic than PVC. Its flame-resistant outer cover doesn’t emit halogen when heated. Used primarily in confined installations. It is required

*Cables used in LANs, WANs, and other networks must meet the LSZH specifications in the European market, in accrodance with the requirements in the IEC 60332-1.

Optical fiber cables are categorized according to the National Electrical Code (NEC). These specifications define how the fiber cables will act in a fire situation and classify them based on their intended use in these various areas.

What is the Plenum Area?
A plenum area is a space used to move air to workspaces for the purpose of ventilation or to form air flow for an air distribution system.

What is the Riser Area?
Commonly seem riser areas are floor openings, tubes, or channels that run upwards over one or more floors. Riser cable is planned for use in upright shafts that run between floors.

What is the General-Purpose Area?
A general-purpose area is all other areas that are not plenum or riser on the same space or floor.

Fiber Optic Cable Jacket Fire Ratings

For fiber cables, there are four levels of fire rating levels, and conductive and non-conductive cables are divided into two categories for each level. While the lower rating cables can’t be used in place of the higher ratings, the higher rating cable is backward compatible with the lower rating cable and can be substituted.

Optical Fiber Nonconductive Plenum Cable (OFNP) and Optical Fiber Conductive Plenum Cable (OFCP) are two types of fiber cable. As their names imply, OFNP and OFCP cables are used in plenum areas and are fire and smoke resistant.

For the riser areas, optical fiber nonconductive riser cables (OFNR) and optical fiber conductive riser cables (OFCR) are used. The spread of the fire must be stopped between floors by these cables.

Optical Fiber Nonconductive General-Purpose Cable (OFNG) and Optical Fiber Conductive General-Purpose Cable (OFCG) refer to optical fiber general-purpose cables that are neither conductive nor nonconductive. The length of the cables that spread the fire cannot exceed 4 feet, 11 inches.

OFN and OFC Fiber Cable refers to optical fiber that is both nonconductive and conductive. The cables must also be used in general-purpose areas and the flame must not penetrate the floors or ceilings to receive this cable rating.

*Nonconductive: Cables that are nonconductive are those without metal components and do not contain any conductors.
*Conductivitive: The cable has a conductivity, but there is no current flowing through it.

Active Optical Cable Jacket Explained: OFNR vs OFNP vs PVC vs LSZH?

We can put to rest the confusion between OFNR/OFNP and LSZH/PVC cables now that we are aware of the various cable materials and their fire rating levels. These two types of properties are not the same, they are just referred to differently. It may cause issues in choosing the right fiber optic cables including active optical cables (AOC) is failing to comprehend these classifications properly.

How to Check the Cable Material and Fire Rating?

For cables that comply with the UL standards, we can check the UL marking on the cable jacket, which lists its material type and its fire rating level. Take the following NADDOD InfiniBand AOC cable as an example, we can find the markings “… (UL) type LSZH OFNR …” repeated at intervals not longer than 40 inches.

QSFP56 200G HDR 5m AOC outer jacket

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