Fiber Optic Cable Basics

You hear about fiber optic cables whenever people talk about telephone system, cable TV system or the Internet. They are also used in medical imaging and mechanical engineering inspection nowadays. How much do you know the basic information of cables? For example, what a 9/125/250µm cable mean. In this article, we will show you some cable basics.

Cable Size

The size of the optical fiber is commonly referred to by the outer diameter of its core, cladding and coating. Example: 50/125/250µm indicates a fiber with a core of 50 microns, cladding of 125 microns, and a coating of 250 microns. The coating is always removed when joining or connecting fibers. A micron (µm) is equal to one-millionth of a meter. 25 microns are equal to 0.0025 cm. (A sheet of paper is approximately 25 microns thick).

Cable Types

Cables can be identified by the type of paths that the light rays, or modes, travel within the fiber core. Also according used in different environments, there are outdoor cable, waterproof cables, lszh cable, submarine optical cable, etc.

Distribution Cables

These cables are small in size, and used for short, dry conduit runs, riser and plenum applications. The fibers are double buffered and can be directly terminated, but because their fibers are not individually reinforced, these cables need to be broken out with a “breakout box” or terminated inside a patch panel or junction box.

Breakout Cables

They are suitable for conduit runs, riser and plenum applications. Because each fiber is individually reinforced, this design allows for quick termination to connectors and does not require patch panels or boxes. Breakout cable can be more economical where fiber count isn’t too large and distances too long, because is requires so much less labor to terminate.

Loose Tube Cables

These cables are composed of several fibers together inside a small plastic tube, which are in turn wound around a central strength member and jacketed, providing a small, high fiber count cable. This type of cable is ideal for outside temperatures and high moisture conditions(waterproof cables also do good jod in moisture conditions), as it made with the loose tubes filled with gel or water absorbent powder to prevent harm to the fibers from water. It can be used in conduits, strung overhead or buried directly into the ground.

Ribbon Cable

This cable offers the highest packing density, since all the fibers are laid out in rows, typically of 12 fibers, and laid on top of each other. This way 144 fibers only has a cross section of about 1/4 inch or 6mm! Some cable designs use a “slotted core” with up to 6 of these 144 fiber ribbon assemblies for 864 fibers in one cable! Since it’s outside plant cable, it’s gel-filled for water blocking.

Armored Cable

Used for rodent protection in direct burial if required. This cable is non-gel filled and can also be used in aerial applications. The armor can be removed leaving the inner cable suitable for any indoor/outdoor use. (Temperature rating -40ºC to +85ºC)

Indoor/Outdoor Cable

Indoor/Outdoor cables combine the flame resistance and safety features of an indoor riser or plenum cable with the durability that is critical for OSP use. The result is a unique, dual-purpose cable that can save time and money by allowing OSP applications to flow seamlessly indoors, using a single cable and no splices.

Aerial Cable

Aerial cables are for outside installation on poles. They can be lashed to a messenger or another cable (common in CATV) or have metal or aramid strength members to make them self supporting.

Special Cable

These cables combine specialty optical fiber with cabling construction that make installation or deployment easier and/or protect the fibers for long-term use in harsh environments.

Even more types of cables are available and also many brands cables from different manufacturers are available. Corning is one of the outstanding fiber optic cable manufacturers, who invented the first commercially viable low-loss optical fiber in 1970. Today Corning remains the global market leader in the industry, the corning fiber optic cable is recognized for their excellence and innovation.

Fiber Optic Cables For Harsh Environment Applications

Fiber based systems offer apparent advantages over electrical methods in large plants and factories where the harsh environment threatens data reliability and security. Unlike copper cable, fiber optic cabling is resistant to electromagnetic interference (EMI), making it an ideal option for harsh environments involving high voltages or machinery with variable frequency drives, is a safe alternative to traditional wiring.

As you know, fiber optic cable consists of three parts: the core, the cladding, and the coating. The core transmits the light and has a high refractive index. The cladding contains the light within the core because its lower refractive index causes all the light rays to reflect back into the core. This “total internal reflection” or “fiber-optic effect” is the technology’s underlying principle. The coating, usually an acrylate polymer, protects the core/cladding assembly.

Optical fiber is typically made from high-purity silica glass. Plastic fiber of varying configurations is also available. But the attenuation of light energy can approach one thousand times that of glass fiber. The length and integrity of the transmission path and the core/cladding arrangement affect the bandwidth, or the frequency range that the optical fiber transmits. Fiber bandwidth is expressed in megahertz-kilometers (MHz-km).

Depending on the application, the distance involved, and the location, several types of cable configurations and connector types are available. Optical fiber is fragile and must be protected, mostly from mechanical stresses such as bending, crushing, thermal effects, and pulling during installation.

Tight Tube And Loose Tube Cable

A tight-tube (or tight-buffer) design has a PVC coating, which tightly bonds to the fiber, limiting movement. This cable type can have strength members, which you pull through conduit and cable trays. This design, however, has low crush resistance and is susceptible to deformation due to thermal expansion; thus, it is recommended for indoor use only.

A loose-tube design gives a fiber free movement. Each component of the Loose Tube Cables (the sheath or outer coating, the strength member, and the buffer tubes that carry the fibers) has different thermal characteristics. By allowing the fibers and the components surrounding them free movement, deformation is avoided.

Loose-tube construction has much better crush resistance than tight tube because of the buffer-tube protection of the fibers. Loose-tube cables have a strength member, which is used as the pulling member for conduit installation. Loose-tube cables are usually filled with a gel, which surrounds the fibers and increases protection from water. This also improves crash resistance because of the gel’s cushioning effect. You mostly use this cable type for outdoor applications, but you can also use it in harsh industrial environments. A drawback to this type of cable is the difficulty in handling individual fibers. The fiber coating does not have to be as thick as in tight-tube construction; thus, attaching connectors is difficult.

Remember that tight-tube construction does not allow for free movement and provides low protection against mechanical stress. It does, however, have a thick coating for ease of handling. Loose-tube construction, on the other hand, allows free movement and provides a good degree of protection.

Breakout Cable

Breakout cables are a hybrid solution. In a breakout cable, each fiber is treated as a separate unit, complete with a sheath and strength member. This design eliminates the need for a breakout kit, because the sheath lets you attach connectors easily.

Breakout Cable Fiber let fiber subunits move freely, and they protect each fiber by virtue of their thicker coating/strength member arrangement. Each fiber subunit is configured as a tight tube. Breakout cables also come equipped with a separate strength member just like the loose-tube design.

FiberStore harsh environment Fiber Cables is designed and manufactured with specialized components which provide improved performance and protection against damage, breakage, and performance limiting conditions that often exist in harsh environment applications. FiberStore has the resources, expertise, and experience to design, develop, manufacture, install, and maintain a product ideally suited for your exact application.